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Laser cutting takes what we engineer at the desktop and brings it out into the real world. For a luthier, this enables creating our most common working tools - router templates - to be made simply yet precisely. A real game changer! Translating creative or technical design work into router templates opens up a world of design options. Anything from an accurate outline of your body/headstock, pickup and electronics cavities, through to complete modular templating systems for recessed tremolos, etc. Powerful desktop design tools and laser cutting takes your building to the next creative and technical level. "Having it laser cut" sounds like a magic bullet of sorts; draw something up and having it drop out of the other side with little to no real effort. That's not actually too far from the truth; the technology is definitely more usable and accessible than it ever had been. The key to winning lies in mastering a number of simple fundamentals and managing a few basic expectations. Once you've moved beyond these, laser cutting becomes a very workable part of your armoury and one that you'll always find new ideas and challenges for....and like any tool, it is only as good as what you make of it! ----==---- ARTICLE SCOPE - The focus of this article will be on how to locate and choose the right laser-cutting service, illustrate the desktop work necessary to produce drawing files that are pretty much good to cut and finally show a couple of real-world working examples. We are making a few assumptions here. First is that you know basic vector work (AutoCAD or other CAD packages, Illustrator, Inkscape, CorelDRAW, etc). Secondly, that you are more or less familiar with manipulating vectors, managing object types, inspecting and changing their attributes, etc. with your chosen vector drawing package. Beyond this, laser cutting is a pushover! ----==---- CONTENTS - 1. Finding Your Laser 2. Starting Out - Communication Is Key 3. Design-Time Considerations 4. File Exchange - Break It Down To Basics 5. Example 1 - Simple Bench Hold-Down Templates 6. Example 2 - Electronics Cavity Routing Template Set ----==---- 1. Finding Your Laser Okay, well we have two options for getting our templates made. First - getting your hands dirty at a Makerspace, Hacklab, community college/educational facility or wherever else offers public/membership access to a suitable laser cutter. By far, this is the best way of extending your skill set; your time can be spent fine-tuning (or replacing!) your templates hands-on. You have end to end control. This might be a bit more costly in the short term; mandatory safe usage courses and basic fees are a necessary price to pay. You'll probably burn through a lot of material (joke not intended, but apt) in your first attempts too. It's definitely a swift and easy complete control solution once you've ticked those boxes, and the cheapest route for the habitual user. The scope of this article is not intended to take any precedence over the advice you're given during laser cutter induction. Every location will have its own set of house rules, so rely on their expertise and recommendations. Every laser is different, every facility is different. The tutors who do this are your gurus, so drop preconceptions and let them guide you. The other option is reliance on third-party services. These can vary from brick-and-mortar shop/bureaus like Mostly Out Of Cardboard, turnkey online services such as Ponoko or specialist guitar supply companies with in-house custom laser cutting such as Guitars and Woods. Third party services are not necessarily an inferior choice or even an expensive one, however you do need to shop around for a service which understands your requirements and preferably does this work all of the time. Your local trophy maker "who happens to have a laser" might charge you well over the odds for the inconvenience of reconfiguring their machine for a one-off sheet job, however simple. It might simply not pay as much money on the hour as their normal line of work, or be an alien process to them. Even a shop signage maker who cuts sheet day-in day-out might not offer an attractive price on small one-off jobs. Third-party services have the advantage of experienced operators, and you should use that. Ask if they've cut templates for luthiers or woodworkers before. Familiarity - or at least an understanding - of what you're wanting to achieve is 90% of the battle won. If they've done anything similar before, they might be able to suggest improvements on your basic design for future work or simply snag any errors in your work submissions. If they haven't, gauge whether they're open to the idea of what you're wanting and understand its purpose. Companies that are genuinely interested in your product and having you as a satisfied customer are worth fostering a relationship with....as long as that isn't simply a way of sleazing deeper into your wallet! A lot of creative and inspirational people work in laser cutting services, Makerspaces and community colleges. Often the opportunity to collaborate on something new and exciting (as exciting as router templates get?) is more important to them than a bit of time or turning a quick buck. Some operators are genuinely excited just to see new things come off the laser and might be happy just for the cost of materials. "Head towards the people that have that creative spark and not the jaded old farts who might just see you as an inconvenient interruption to their non-stop conveyor belt of boring paint-by-numbers imported Chinese component school sport's day trophies given out just for participating rather than representing real achievement." - Benjamin Franklin ----==---- 2. Starting Out - Communication Is Key The people you need to be on friendly speaking terms with from day one are the keyturners or regular users, whether they're engineers on the other end of the phone, colleagues, Makerspace tutors or fellow denizens; whoever. Laser cutting is a fairly simple process with a few hidden tricks and obstacles you need know before you encounter them. Communicating your needs and existing knowledge will produce a smoother process from your desktop to the finished item. Design Protocols There are basic conventions within drawings which denote how the laser driver will interpret the job. We'll look at these later, however you should ask your service what their own in-house conventions are, or check with the other people in your Makerspace, etc. how to set up the drawing appropriately to work with the default laser configuration (this should be covered during safe usage courses). Firstly this saves time fixing things in the mix, or worse, trashing good material. Most importantly it may ease third-party setup charges if your drawing is good to go straight to the laser. It definitely gives you room to negotiate that cost. It has to be borne in mind that services will likely operate an hour rate on setup. These charges are superfluous when a drawing is poorly designed or doesn't conform to house protocols and needs the attention of an engineer or operator! We have a dedicated thread on laser cutting over on the Forums. If you're wanting to send jobs out to cut, but are unsure on whether your design is completely appropriate for that purpose, join the conversation and we can fix most things up! Material Selection Not all Makerspaces or third-party services have a full selection of materials on-hand. Prices may also vary due to wastage, availability and basic markup. Plywood designed specifically for laser work tends to be more expensive as it has to be free of knots and voids, plus needs to use glues safe for laser cutting. Acrylic will be (well, should be) tempered cell cast due to problems with cracking and poor finish quality with the extruded variety. The right materials cost a little more, but produce infinitely better and more durable results. Thicker materials can come with unexpected side effects, such as larger kerf (width of cut left by the laser) sizes or cut edges which are not perpendicular to the face. Thinner stock is a more accurate choice for closer-fitting parts. This is a good subject to discuss with the users/owners of the laser; if theirs has the right optics and power to cut 1/2" acrylic perfectly then go for it! Ask for advice on choice and comparative costings with stock materials; you might even get a great deal on a job if something can be pulled from the offcut bin. Asking the question costs nothing and can save you a significant amount of money. Exchange File Format More than likely you'll do your design work away from the site where the laser is located, and probably using different software also. Modern laser cutter drivers are far more forgiving of input formats than they were a few years ago, however that isn't to say that every bug has been rattled out. Choosing the most appropriate format for file exchange from your machine to that of the laser is vital. If you're going third-party, as what their preferred file format is and perhaps what software they are using; if you both happen to be using CorelDRAW you can cut out unnecessary conversion steps and swap native file formats directly. I prefer DXF (Wikipedia) simply because it is the most common and interoperable file format for vector information. The same rationale applies to other packages (Inkscape, Illustrator, etc) where exporting to a widely-supported basic file type removes most common errors from translating across formats. "What-You-Get" If you're using a third-party service, ensure they are aware which cut pieces you're actually needing from the job. A negative space router template (such as a pickup cavity) may not be immediately obvious, leading to problems where you receive a "Tele pickup shaped piece of Masonite" in the mail instead of the surrounding template for cutting the cavity! Explicitly stating, "This is for a 200mm x 150mm rectangle of Masonite with that shape cut out" makes all the difference. For more complex jobs where you are needing both the negative and positive components from the cut, again, state this from the outset. It saves a lot of time and hassle. Not all laser services will know what a router template is or its end use. Obviously this is less of a problem when you're cutting work under your own steam. One issue that might crop up is when cutting out fine components. Air assist which prevents flareups will happily blow your valuable but newly-loose parts around the bed, or worse, into an exhaust port! A little double-sided tape under the material in the right places and the use of a spoil board underneath helps. Whilst this isn't a communication issue, double-checking with a third-party service that they use the same kind of approach is. ----==---- 3. Design-Time Considerations Keeping a design as simple and to the point as possible wins the day. Only add as much information as the templates really need. The true test of a template is in the quality of the workpiece it produces; not how tricked out the template is with text, logos and irrelevant detail. This is especially important if the service charges by time or in the case of Ponoko, a function of total laser work movement length! Going through your design from top to bottom pays off. Common problems that are not immediately apparent can be revealed by developing your own methodical approach to validating your designs. Alignment Marks - Transparent Materials Acrylic offers us a great opportunity to add engraved markings that can be seen through the template itself. The problem is that lasers cut from the top down. This just requires that the finalised design is mirrored prior to sending out for cut so engraved text will appear correctly when viewed through the template, plus alignment marks lay directly next to the workpiece. click to enlarge Alignment Marks - Opaque Materials Opaque materials such as Masonite or MDF may be difficult to reconcile with alignment marks such as a centreline; after all, engraved marks will be placed onto the top surface of the template and we can't see through the material like we can with transparent acrylic. For most cases, this is not too problematic; we can add additional auxiliary cutouts within a template to assist with alignment where it might not otherwise be possible. In the example above, diamond-shaped auxiliary alignment cutouts allow the template to be placed accurately on a marked centreline using internal corners rather than approximating from a top-engraved marking at an oblique angle to the edge. This is also invaluable for alignment on angled headstocks, where the centreline falls away past the nut area. Work Layers Use of separable layers improves workflow. Placing all engraving work onto a separate layer to cutting makes it a simple task to confirm that paths are not duplicated, incorrectly set and properly aligned, etc. Colour within the drawing is used as the primary guide for different laser settings. Most laser driver software can be configured so that many different colours to represent various combinations of speeds, powers and duty cycle frequencies. The accepted basic standard is that red (RGB 255,0,0 - #FF0000) represents a cut and blue (RGB 0,0,255 - #0000FF) represents an engraved line. If using a third party, confirm their house rules and conventions on colours and whether line weight is a consideration. My personal arrangement is to use black (RGB 0,0,0 - #00000) to denote the rectangular working outline for larger negative templates. Some houses may interpret this as an engraved mark unless it is explicitly stated that black represents a cut. Ensure that your drawing objects are explicitly set to the correct colours, not simply "By Layer". If your software has the ability to "select all items by colour", this helps with confirmation. Another check is altering layer colours to something unused, such as bright green.....if any objects are set to follow colour by layer, they'll stand out clearly. Kerfs Laser cutting produces small but still significant kerfs, or the "width of cut". Several factors such as material type and thickness affects the final size of kerf, however it is usually in the region of 0,15mm for thinner materials. Confirm with the laser operators what the expected kerf size of the material you are working with is, or make test cuts and physically measure it yourself. A typical kerf is in the region of 0,2mm and equates to an offset of around 0,1mm from the expected drawn outline. Kerfs are hardly worth concerning yourself with for headstock and body templates, and in fact it works in your favour for bolt-on neck/heels. Other precision joinery Items that require a tight conforming fit - such as set neck joint templates - will need test cuts to be made and the templates proofed for suitability. Offsetting the mortise half the kerf size smaller and the tenon half larger is a good start, however the proof is in how well the joints routed using the templates mate together. Adding in a larger offset than is necessary is also an option. It's better to fine tune the wood with some sandpaper than it is to have it loose straight off the router! ----==---- 5. File Exchange - Break It Down To Basics Many of the design tools in various CAD packages produce complex objects that are often handled in a manner specific to that package. For example, different types of curves, mathematically-generated contours or even text objects. Unless you are working in the exact same software that outputs jobs to the laser, the two different packages can have radically-different opinions on what how your work is supposed to render, resulting in incomplete or incorrect cuts by the laser. We can work through this by taking complex items and devolving them down into basic objects (called Primitives) that are unambiguous and are rendered equally by all software packages. A common error is font usage. They'll happily render within the package they were created within, however there is no guarantee that this will translate through to the finished product. Take the following example in TurboCAD: click to enlarge It might not seem immediately obvious that any kind of problem might exist here other than the font being solid rather than an outline. Times New Roman is a vector font, which might seem pretty universal to most systems. However, once this work is saved out to the common DXF format and re-opened in the software used for the laser (in this instance CorelDRAW for an Epilog platform) we see that the font has been substituted to a completely different one, and is no longer mirrored as in TurboCAD. How to we prevent file format exchange errors such as these? click to enlarge Complex to Simple (or "Simple > Complex") CAD packages have all kind of tools for producing high-level objects. Underneath it all, these objects are still built from a basic set of Primitives, such as lines and circles. Instructing your software to take each high-level object and strip away the complexity varies from package to package, however is usually called Explode. In the example above, taking the text object in TurboCAD and Exploding it down into Primitives should allow any other package to interpret it correctly. Often this will need to be performed more than once depending on the object being Exploded. For TurboCAD, this needs to be carried out twice in order to devolve the Text object to a single Group of objects, then down to individual Primitives (normally Polylines). However your own software works, inspect the objects to figure out whether they need Exploding further. Some objects such as characters within Text may Explode down into two individual parts; the fill and the outline. Deleting any fill prevents duplication of the same object, since we only need text character outlines. click to enlarge - a letter "O" Exploded down into internal and external polyline shapes. It is also worthwhile considering Exploding curves; whilst simple curves normally render correctly between different software packages, they usually cause the laser head to move slower than with sets of lines as the driver interprets the curve mathematically. Exploding a curve down into discrete Polyline objects is recommended to reduce job complexity and increase speed. Before committing, compare how granular a Polyline is in comparison to the original curve. Most software allows you to define how finely a curve is broken down into a Polyline. For most jobs, a cut made using Polylines is indistinguishable from one made with curves. Once you have a better understanding of which objects translate well via your chosen file exchange format, you can Explode only the ones that don't. Ultimately, if the end product cuts quickly and efficiently, breaking your drawing down to its absolute basics prevents unexpected bugs from creeping into your designs. ----==---- 6. Example 1 - Simple Bench Hold-Down Templates A few months ago, I sent out a quick turnaround job to Henri at Mostly Out Of Cardboard (MOoCB) for some acrylic pin routing templates. The files were supplied as individual DXFs. Each holddown consists of an outline plus several holes used for aligning and stacking pieces together. Henri simply imported the DXF files into CorelDRAW, set each outline for the appropriate cutting settings in the laser job driver. Being extremely simple, Henri was happy to accept the DXF files as-is straight from my CAD package and set colours for cutting, etc. at his end. ----==---- DEMO FILES - 125mm offset holddown.DXF - 175mm offset holddown.DXF - 200mm offset holddown.DXF preview of 125mm offset holddown.DXF ----==---- On my doorstep the next day I had these (love the packaging): This was an extremely simple job, which required very little back-and-forth communication. Henri is experienced at cutting a great number of different materials, so three small acrylic components was a walk in the park. In fact, I asked for "whatever light acrylic stock" they have on hand which resulted in these 4mm. A job such as this is mostly material cost with minimal setup time; even the packaging is only a minute job on top of the parts themselves. Like any job, there will be a degree of setup on some level, whether it be a complete treatment and check of the vector file sent (some bureaus insist on this, and make the charge mandatory...) copy grouping parts for efficient batch cutting or laser configuration (origin locating, focusing, etc) prior to running the job. The templates worked fantastically. 8mm-thick Oak blanks were pre-drilled and bolted down to the sled and shaped using an overhead pin router. The templates seat underneath and the pin rides against them. A very simple and neat use of laser-cut templates! ----==---- 7. Example 2 - Electronics Cavity Routing Template Set Anybody that knows me enough will be aware that I think far too much about the classic basses that came out of the Matsumoku factory in Japan from the late 70s to the late 80s. The most known of those is the Aria Pro II SB-1000 with its tank-like dual-mode 18v electronics and recognisable signature sound. A slow-burning project of mine has been to make a more or less authentic replica of the SB-1000, but with altered specifications....and a fifth string. The electronics cavity is something I'd like to replicate rather than make "similar to", so I recorded the measurements from a real SB-1000 and drew the cavity up in CAD with a few basic improvements and some cleanup. An original SB-1000 electronics cavity, bereft of life. Whilst not the most elegant or precise of electronics cavities, the space for the preamp module and batteries, plus the recesses produce a nicely-organised electronics cavity that isn't thin and weak like most "swimming pool" cavities. I figured that a set of four templates would be perfect. The first being the main outline of the cavity cover recess and cover plates (the plate is split into two pieces), a template for the main "body" of the rout down from the outer cover plus the narrower part of the battery/preamp niche, an auxiliary template to produce the wider ledge either side plus a template for the recesses. Since these templates are all related to each other, I decided that it would be useful to have engraved alignment markings on the lower face along with some basic information to remind me what to do (or not to do). As mentioned previously, lasers only cut from the top down, so engraving on the lower face means these will all need to be cut in mirror image. A vector line font was used for the text for both clarity and simplicity. Screwhole locations were marked with 2,5mm diameter circles with Point objects (crosses) engraved in their centre. The Points were Exploded down into Line pairs. A potential issue would be duplicating the cavity cover split Line. Since I drew the whole outline and added the split later, this was no problem. A look at the layer manager ("design director") shows that I defined several layers for this project. Each one contains references and guidelines, text labels or the work for the laser. This helped me create a template set from one master drawing, with the organisation allowing me to work on all of the templates as a group or individually. Turning on all of the layers shows how everything was designed. A bit of a nightmare when you look at it like this, but it works! Diary of a CADman (ergh.....) TurboCAD allows me to electively export specific objects to DXF files, so I selected the objects relevant to each template and sent them out to four individual DXF files. As you would expect, all Text, Arc, Point, etc. objects were Exploded to Lines and Polylines. I contacted Guitars and Woods to produce my template set in 5mm acrylic along with a few different designs. G&W sell templates for many common guitar designs (Strat, Tele, Flying V, etc.) and do all of their cutting in-house. Since they know the product and a luthier's needs, it seemed perfect to use them for these templates. After an email exchange with G&W on their convention on cutting and engraving colours, material availability, pricing, that DXF was an appropriate exchange format, that the outline was denoted by the outer black rectangle, etc. I sent the four DXFs to cut. Just over a week down the line we received this tidy little package.... click to enlarge So here's that first template described earlier. The alignment crosses and text appear the right way around and are engraved on the underside. Each screw/threaded insert location has the small hole for punching and the alignment marks. I used the kerf of the laser (~0,15mm) to my advantage; the cavity cover plates will drop in perfectly. click to enlarge The cavity cover recess will of course require a thicker (and wider) template to be made up since it is only meant for a 2mm cut depth. I don't think router cutters are even available that shallow! Nonetheless, marking out the location internally is important and a transparent template is excellent for alignment purposes.... click to enlarge ....due to how the other templates were designed. The outline of the cavity cover recess is replicated here as an engraved reference on the underside. By aligning this with an outline drawn using the first template (or marking off the outline since the templates are all cut from 250mm x 120mm pieces!) we have an accurate placement for each subsequent template. click to enlarge The auxiliary template is shaped similarly, but is only used for the battery ledge. click to enlarge Finally, the control recesses. click to enlarge I labelled the templates 1 through 4 and added pertinent routing information to each one. In most instances, these templates would be retained as "master templates" and copied across to a thicker sacrificial material such as Masonite, plywood or MDF. ----==---- In Closing Access to and use of laser cutting services is far easier than you might expect. Maker culture has gone a long way towards normalising this sort of technology almost into everyday life; taking advantage of that as a luthier is a simple and economical step in taking your work forward in huge bounds. Over on the ProjectGuitar.com forums we've opened up a Laser Cutting Discussion And Advice Thread. We hope this article has inspired you with new ideas and methods of producing your instruments; ask anything you want about laser cutters, designing templates or components, CAD-related issues or even service recommendations. http://www.projectguitar.com/forums/topic/48625-laser-cutting-discussion-and-advice-thread/ ----==---- www.patreon.com/ProjectGuitar This article was made possible by the generous donation our our Patreon supporters, plus invaluable input and assistance from Henri at Mostly Of Of Cardboard and Carlos of the Guitars and Woods web store. Cheers guys! If you enjoyed and benefitted from this article. become a Patron of ProjectGuitar.com and help us bring you even more articles, tutorials and product reviews like this, week-in week-out! Thanks to ProjectGuitar.com's Patrons sirspens a2k Chris G KnightroExpress Stavromulabeta Andyjr1515 sdshirtman djobson101 ScottR Buter curtisa Prostheta 10pizza verhoevenc VanKirk rhoads56 Chip

Recently I made the decision to step into the world of CNC routing machines and augment my small workshop and tool collection with a modestly-sized unit. With the rise in quality of low-end Chinese-made machines in recent years it has become easier than ever to purchase a small CNC router for home use capable of high precision. A quick search on online auction sites will reveal a vast array of pre-assembled units for sale starting in price from less than $700, with cutting beds up to 600mm x 900mm in size. While I am still a novice at CNC, hopefully my experiences can help others decide if taking the plunge is for them too. So, why choose a small CNC router? There were several reasons why I personally decided to purchase a desktop machine with the intention of applying it to guitar work: I had a limited budget and a small area where I could set up such a machine. A CNC router capable of directly milling a guitar body from a timber blank is physically large, noisy and expensive; I was after a way to improve the appearance of my builds by including professional-looking headstock logos and markings, and had thus far been dissatisfied with many of the solutions that utilised decals or transfers; I wanted a quicker and safer way to create templates for routing smaller shapes and components used in guitar construction (eg, pickup cavities, headstock outlines, truss rod covers); Having decided to explore multi-scale instruments I needed a way to make accurate drilling templates for the individual bridge assemblies commonly used for these instruments; Despite wanting to automate some of the construction process, I still wanted to retain the hands-on nature of building an instrument rather than transfer the bulk of the cutting and shaping work directly to a machine; The increased accuracy afforded by the machine for particular tasks was attractive (eg, scribing fret slots directly onto a fretboard blank, creating perfectly-fitted control cavity covers). The CNC machine I eventually settled on was at the smaller end of the scale; a 3-axis desktop unit with a similar footprint to a mid-sized inkjet printer, having a cutting bed of 200mm by 300mm (X- and Y-axis respectively) and a vertical travel of 50mm (Z-axis). The spindle is rated at 200W, with a 1/8” collet which allows the changing of cutters using a wrench system similar to that used on many handheld routers. The build quality of the frame and gantry seems quite acceptable, although for the price paid I would expect some shortfalls in terms of frame flex and milling accuracy of the spindle due to runout and eccentricity. However if you don’t work the CNC router too hard any errors in the finished milling process will be minimal, and achieving sub-micron precision in a material such as timber is probably a moot point anyway. A separate controller interface unit is supplied featuring variable spindle speed via a dial on the front panel and PC connectivity through a parallel port on the back. It is worth noting that most of the models which utilise a parallel port to interface with the computer require a desktop PC rather than a laptop, as the battery power management features of the latter are not conducive to reliable operation of the CNC router. Commonly available USB-to-Parallel Port adaptor cables are also incompatible with these units. However, if your host computer does not have a built-in parallel port you can purchase and install an aftermarket PCI parallel port card, which is exactly the path I chose. The unit also came equipped with a selection of endmills, a set of rudimentary work piece holding clamps, a number of allen wrenches and spanners and an evaluation copy of the Mach3 CNC motion control software. While the supplied endmills are satisfactory for learning the ropes and experimenting with different cutting operations, you may wish to invest in a small collection of higher quality endmills, which afford a far superior finish and longer working life than the factory-supplied ones. The controller is connected to the CNC mill via several cables with locking collars to prevent them inadvertently working loose. An unexpected bonus feature of the particular model I chose was that the controller circuit board is fitted with several unpopulated connectors that allow the retro-fitting of axis limit switches. On more fully-featured units these limit switches are fitted to the moving components as a safety measure to prevent the software accidentally driving the CNC machine past its maximum limits of travel, or to allow automatic homing of the cutting head (more in this in future articles). On the subject of software, there are two main options for driving a parallel port-based CNC router; the above-mentioned Mach Series software which is for Windows-based machines and LinuxCNC (formerly known as EMC2) for Linux-based systems. As LinuxCNC is a well-supported open-source option for these machines I elected to take this option and install a Linux partition on my host computer. Conveniently, LinuxCNC offer several LiveCD versions of their software, which has the motion control software pre-installed on a Linux operating system. The operating system can be run directly from CDROM or DVD without having to be installed on the PC. If the user decides that they would like to continue using Linux, they can choose to install the operating system and motion control software directly from the LiveCD. As these machines are directly exported from China or imported via an agent, technical support tends to be quite limited. The units require some software configuration in order to move the axes in the correct direction at the correct rate. The machine itself is incapable of knowing where it is positioned relative to the cutting bed, or how many turns of the axis motors are required to move it an exact distance without some form of calibration data maintained by the host software. Fortunately there are several online resources to help users configure their CNC routers in order to achieve precise operation. Once configured to run from the motion control software, the user can load files into the application to direct the cutting head to manoeuvre around the work piece at pre-determined directions, speeds and depths in order to create the final object. The language used in these files is known as G-Code and consists of text entries directing the axis motors to move in a specific direction at a certain rate. Other specialised commands in G-Code are used to command the spindle motor to turn on and off, make the program pause at key steps in the routine, or cause the axes to move in predefined ways such as cutting an arc or drilling a hole. While it is possible to create a G-Code file from scratch by typing commands one at a time in a text editor, it is far easier and quicker to use a Computer Aided Drafting or Computer Aided Machining (CAD/CAM) application to draw the intended cutting paths and convert the subsequent drawing to its component G-Code commands. The user has the ability to quickly mock up an outline of, say a pickup routing template, export the resultant drawing as a G-Code file, open the file in the motion control package and cut out the routing template from a sheet of MDF with sub-millimetre accuracy in a few minutes. While some CAD and CAM applications are integrated into one common application, there are also many offered as separate software solutions. Some packages are open-source and free while others cost anywhere from a few tens of dollars to well in excess of $1000, all with varying levels of ease of use, feature sets and functional integration. Below are a few examples of what operations are possible using the small desktop CNC machine when applied to guitar building. This headstock logo was first engraved while being held in a simple jig to allow the workpiece to be accurately positioned without moving. The work was done in two passes, with the larger of the two pieces of text milled using a 0.8mm diameter endmill, and switching to a 0.7mm endmill for the smaller text. The resultant cavities were filled with black-tinted epoxy and sanded flush: Cavity covers can be directly cut on the CNC router from thin timber stock, including drilling the screw holes in one pass. To create a matching routing template for recessing the cover into a body it is a trivial matter to take the original cavity outline and scale it in CAD. The resultant file will create a perfectly fitting routing template for that cover. As I was unsure if the machine would struggle to mill such a thick piece of perspex, I milled a 'master' template from 6mm MDF and then used a handheld router fitted with a pattern-following bit to transfer the MDF template to the perspex sheet: If your router has a bushing guide or pattern-following plate attachment you can use it in combination with a small diameter bit to cut cavities with tighter radius corners than woud be possible using a typical 1/2" template bit with integrated bearing. The problem with using a bushing guide is that the template used must be created oversize by the radius of the bushing minus the radius of the cutter. Creating such a template in CAD and then milling it on the CNC router is simple. In the following example I have created a routing template to suit the bushing guide for my router. The cutter used was a 1/4" straight bit and the bushing guide is 16mm in diameter, so the template has been created with a consistent (8mm - 3.175mm) 4.825mm offset to achieve the intended cutting profile for a humbucking pickup cavity: Accurately positioning the independent saddles used on multi-scale instruments can be tricky, as the risk of misalignment is increased compared to a one-piece bridge. Determining the angle of the saddles for the differing scale lengths can be problematic, and if you are constructing instruments where the scale lengths used differ from build to build, making a drilling jig by hand is time consuming. This drilling template was milled and engraved into 1/8" perspex in about 15 minutes and includes the mounting holes for the saddles, the through-body holes at the rear of each saddle, a centreline to assist in positioning the template on the body and the intonation reference mark for the scale lengths used: The CNC machine can also be used to create simple tools for use in building and setting up instruments. The time taken to create this four-sided radius gauge was about half an hour, from mocking up the basic shape in CAD to removing the perspex sheet from the machine's cutting bed. If the tool was to get lost or damaged, creating a replacement should only take a few minutes: Pros: A ready-to-go solution out of the box with minimal assembly required Competitively priced with good accuracy and construction quality Excellent finish achievable on the object being machined Capable of machining a wide range of raw materials (MDF, plywood, timber, plastic, soft aluminium) Good support from open-sourced software solutions Small footprint for installations where space is at a premium Cons: Generally not suitable for direct cutting/shaping of the major components used in guitar construction (eg, cutting body outlines, neck profiles, cavity routing) or machining harder materials (eg, making custom metal components for bridges) Minimal after-sales technical support The control interfaces supplied with the smaller and cheaper units usually require a desktop PC fitted with an archaic parallel port. The software used can be challenging to get to grips with if you’re not familiar with Computer Aided Drafting principles and terminology. Hidden costs associated with using a CNC – purchasing good quality cutters and CAD/CAM software for example ---------- In future articles I will explore calibrating the desktop CNC router and covering some of the basic operations of the associated CAD, CAM and motion control software packages.

As regular readers here at ProjectGuitar.com you will have followed the first two parts of this series of write-ups regarding the machining of fret slots on a compact CNC machine; the kind of machine typically available for less than $1000 on various online vendors. Part 1 dealt with the construction of a special jig that allows the accurate positioning of the fret board blank such that precise alignment between the two milled halves can be achieved. Part 2 covered the necessary formatting of the CAD design of a fretboard created with the FretFind2D web application, such that the milling process was safely executed without damage to the fragile endmills. In this, the third and final article we will finally use the jigs and CAD/CAM files and complete the milling of a fretboard on the CNC machine. Endmill Choice Throughout this article I will be using a 0.6mm (or 0.023") diameter endmill to cut the fret slots. The width of this cutter determines the width of the slot being cut and should match the width of the tang of the fretwire being used. In practice a 0.6mm endmill will cut a slightly wider slot by perhaps a few hundredths of a millimetre, due to eccentricity and runout in the spindle. This is advantageous to us; if the 0.6mm cutter could possibly cut a slot exactly the same width as the fret wire tang it would be very difficult to seat the frets. A little bit of leeway will actually help the frets go in easily. You will recall from Part 2 that we limited the final depth of cut to only 1.5mm. It is probably quite obvious that if the fret slot is only this shallow, after radiusing the fretboard this will not leave much depth at the sides to fit the fret wire tang. There are two reasons for limiting the depth of cut on the CNC: The process of slotting the fretboard on the CNC machine is quite slow and wear on the tiny endmills is relatively high. Effectively we are only using the CNC machine to accurately start the fret slot, While it is possible to machine the whole board to the correct depth, it is recommended that cutting the final depth of the fret slot be performed using a hand fret saw with a depth stop. The final accuracy of the slotted board should not suffer from finalising the slots with a handsaw. The low-cost CNC machines may have poor eccentricity specs for the spindle. If this becomes too severe and the fret slot being milled widens too much at the full depth the risk increases of the fret wire not being securely held in place. As ironic as it may sound, it is better that we rely on the CNC as little as possible to maximise our success in this area . Finally, it is highly recommended that you purchase decent quality cutters for this work. Cheap cutters increase the risk of breaking partway through the milling process. They will also likely dull more quickly, and leave behind slots that gradually deteriorate in quality as the work progresses. The endmills I am using are 2-flute cutters made by Kyocera, and are available in bulk packs of 5 or more from several online outlets. Higher-quality endmills with three flutes are also available for a corresponding increase in price - $25 or more for each piece. Right. Enough talking. Lets get machining. Milling the Board Assuming you have a suitable fret board blank at your disposal, use some double-sided tape to secure it to the MDF jig. Position it such that it is centred on the plate as closely as possible. Good planning will dictate that your blank will be cut oversize to allow the excess to be cut off afterwards (it is cut oversize, right?). In this example I am using a piece of Tasmanian Oak. Fit the base plate to the CNC table and tighten it securely. Install the jig with the attached fretboard such that the two holes nearest where the highest fret will be cut are located on the forward holes on the plate. Install some 1/8" pins or spare 1/8" shank cutters in all four corners so that the jig is held securely on the baseplate. Remove the lower-left pin and set it aside for a moment. Turn on the CNC machine and start up the motion control software. Fit a 0.6mm diameter endmill to the collet and home the axes to the extreme minimum limits of their motion, ie X and Y at lowest-left corner of the table and Z at maximum height. Jog the cutter head to just above the centre of the lower-left hole. The and X and Y co-ordinates at this location will form the reference point for the whole milling operation. With the cutter head positioned here touch off the X and Y axes only - do not touch of Z axis yet. Retract the cutter head back from the table and reposition it such that the tip of the endmill just touches the surface of the fret board blank. Do this carefully as you do not want to snap the endmill by accidentally driving it down into the workpiece. Only touch off the Z axis to this position, Re-install the lower-left pin in the jig and load up the first half of the G-code for the fret board job. As we have the fret board blank positioned at the lower end of the table we will be cutting frets 24 to 9 first. If you analyse the toolpath for each of the fret slots on the screen you will notice that each slotting operation is represented as a series of shallow zig-zag patterns gradually increasing in depth until the final depth of cut is achieved. These are the G-code slotting subroutines we created in Part 2. If all appears OK on the motion control software, start the spindle and begin the cutting program. Watch the axis motion and spindle behaviour carefully to see if anything untoward is happening such as excessive vibration or slipping of the fret board on the jig, and be ready to hit the emergency stop button on the mill. Assuming the feed rate is set to around 300mm per minute the first 16 fret slots will take around half an hour to complete. It is a good idea to keep a vacuum cleaner handy while the cutting progresses, as a fair amount of dust and miniature chips will be generated during cutting. Keeping the fret slots clear of chips will also help with minimising wear on the endmill. When the final slot has completed you should have something similar to below. Switch off the spindle, but do not close the motion control software or turn off the power to the CNC machine. We need the machine and software to retain its home and touch-off co-ordinates. Remove all four pins from the jig and slide the plate down such that the first 16 fret slots are overhanging the front of the table. Re-insert the pins in the four holes to re-secure the jig to the bedplate. In the motion control software load up the second half of the fret slotting job. This file should contain the slots for frets 8 to 1, plus the nut position. With this file loaded, turn the spindle on and run the code. The cutter head should advance to the beginning of the 8th fret slot and begin cutting. Again, keep a close eye on proceedings and be ready to hit the E-stop button if things appear to be going amiss. As the number of frets being cut has reduced by half the job should take around a quarter of an hour to complete. With the nut slot cut and the cutter retracted to a safe distance from the workpiece, switch off the spindle and remove the four pins. The final product is shown below: All that remains now is to gently prise off the board from the jig with a paint scraper or similar, and cut the sides to match the taper of the neck you are building. Further thoughts While we have only machined the slots into the fret board lank, there's no reason why you couldn't perform further machining tasks while the fret board is attached to the jig. All that is required is to create the associated toolpaths from the original CAD drawing, split the toolpaths at the same point that the fret slots were split and run the extra stages as further two-part tiles: Using a larger cutter (say 1/8" diameter) the perimeter of the fret board could be machined to give you the correct taper, and also cut off the extremities behind the nut and beyond the 24th fret. If the truss rod you are installing in the neck is the spoke wheel type (with the adjuster at the heel) the notch at the end of the fret board that is normally cut to provide access to the adjuster head can be easily included in the fret board outline. A nut ledge or nut slot could be cut in place of the zero fret slot that we cut in the above example. If your build included a zero fret and nut this could also be incorporated. Multi-scale fret boards can also be machined using the same technique as outlined in these articles. The fret slots are still defined as straight lines, and the slotting subroutines described in Part 2 will work without any modification. Pockets for fret board inlays can be milled in the same fashion. With a little manipulation in CAD/CAM it is also possible to machine precisely sized inlays from contrasting timber, plastics or non-ferrous metals to match these pockets. The fret board radius can be roughed in on the CNC machine, either by progressively running the cutter head in an arc around the Y-axis up the length of the fret board, or by running the cutter head in straight lines parallel to the centre of the fret board in a "staircase" pattern that approximates the radius.

In the previous article on fret slotting using a compact CNC machine we explored a sectionalised approach to milling a big object in multiple stages, also known as tiling. We also went through the process of constructing a jig that allowed us to accurately position the workpiece such that the end of the first stage of the milling process would align successfully with the next. In this week's write-up we will go through the process of generating a custom template using the online FretFind2D fret board designing tool and formatting the drawing and G-code ready for the milling process, Let's assume that we're in the process of making a guitar and, for whatever reason - be it ergonomic, tonal, a request from a client or sheer curiosity - the design has called for a slightly unusual scale length of 24.6" with 24 frets, made from some eastern-Martian Grumblebum wood we have laying around. No ready-made pre-slotted fret board can be found with this scale length in the timber that we want to use, so we're stuck with having to make our own. Designing a fret board with a particular scale length in itself presents no real challenges; there are several online calculators that will automatically spit out the a table of fret spacings based on an input of scale length It's just a matter for us to transfer this table of measurements onto a blank piece of timber and start sawing away. But in our case we want more precision than simply eyeballing the cut. FretFind2D is an excellent online tool to assist with laying out a graphical representation of a fret board based on some input parameters. It also includes a DXF export function that will generate a CAD drawing file that can be (almost) directly used to generate the G-code in order to drive the CNC mill. Based on our design requirements lets enter the appropriate values into FretFind2D and make up our fret board layout: Units = Inches Scale length = 24.6" String width at Nut = 1.375" String width at bridge = 2.125" Fret board Overhang = 0.125" Calculation method = 12th root of 2 Number of strings = 6 After entering the above data click on the 'DXF - Save to Disk' button and choose a convenient name and location to save this file as. Upon opening this DXF file in a CAD application it is clear that a little formatting work will need to be done before we can start milling; Along with modelling each fret position, FretFind2D also includes the generation of the strings and bridge location, which we won't need when milling the fret slots. Spend some time deleting the unnecessary components - the strings, fret board edges and bridge position lines are not required for our work. I also like to orient the drawing such that the nut is at the top of the screen rather than at the bottom (as FretFind2D positions it in the export), If you normally work in metric units of measurement, scale the drawing up by a factor of 25.4 or allows your software to convert it. You should end up with something that looks similar to this: You will recall in the previous instalment of this series we created a CAD drawing of the fret board holding plate, including the drill hole locations for the tiling jig. We need to now open this drawing and copy it into the fret board layout. When doing so ensure that the lower-left drill hole position gets inserted at X0, Y0. When this is complete re-position the fret slots such that they roughly sit in the middle of the fret board holding plate. Absolute accuracy isn't critical, just make sure you have roughly-equal space around the fret slots: Note the position of the middle drill holes on the tiling jig relative to the fret slots. When moving the fret slots onto the tiling jig, position them vertically such that an imaginary horizontal line drawn between these two holes would fall within the gap between two frets. One limitation of the drawing generated by FretFind2D is that it models each intersection of a fret with a string as a short 'fretlet', each one overlapping the next to give the impression of a continuous line. What we really want is each fret to be a single line. Depending on the CAD package used it may be possible to select each group of 'fretlets' and perform a union operation on them. Failing this we will need to manually rebuild the fret lines. Fortunately this is a simple task of using the existing outer end points of the 'fretlets' to draw straight lines utilising object oriented snapping. It is also a good idea to place the new one-piece fret lines on a new layer to assist with being able to delete or turn off the original 'fretlets' that FretFind2D generated. In the example below I have created two new layers - one for the redrawn frets below the midpoint of the jig (green) and one for the frets above the midpoint (yellow). Now we have our fret board formatted it is time to split it into the two tiles for our jig. Select the upper 8 frets and move them down using a middle drill hole as a start point and a lower drill hole as the end point. The result should look like this: While this looks messy at the moment, each layer can be independently turned on and off to display each half of the fret board. This forms the basis of the phyical alignment of the two tiles that need to be cut on the machine to complete the full fret board. In the above image, the green slots would be milled on the fret board blank in the position as shown. At the end of this milling operation the workpiece gets shifted down and the yellow slots are then milled at the positions shown. But because the fret board blank has been moved to a new position the remaining yellow slots get milled above the relative position of the green slots, thus completing the full fret board. Turn off any remaining layers and leave the (green) layer containing the lower 16 frets visible. Perform a CAM export of this drawing with a feedrate of 300mm/min and a Z depth of -0.3mm (or 12 inches/min, Z-0.0118" if you work in imperial units). Switch off the lower-16 layer and switch on the upper-8 layer. Perform a CAM export of this display with the same values as before. You should now have two G-code files describing the geometry of each half of the fret board. It is tempting to now simply run these two G-codes and complete the fret slotting operation, and indeed you could conceivably run these G-code listings and have the slots scribed onto a timber blank right now. The limitation is that we currently are only cutting the slots to a fixed depth of 0,3mm. We want the fret slots to be deep enough to accept the tangs of our fret wire, which could be a couple of mm tall. So maybe we could increase the depth of cut when we export the G-code from CAD? The problem here is that the cutters used to mill a fret slot are only 0.6mm in diameter and extremely brittle. Attempting to move such a tiny endmill through a hard material like ebony or rosewood at the full depth is likely to immediately destroy the endmill. So perhaps we could run the entire program multiple times and bit-by-bit increase the depth of cut on each successive pass? That is an option, provided your step change in cutting depth is quite small. The risk here is that even if the cutter is plunged in only a small amount the sudden lateral jerk as the endmill begins its traverse slotting operation can again stress the cutter too much and break it. The process of copying and pasting the entire run of code many times over is also very wasteful and hard to follow if something needs debugging. What we can do is gently ramp the endmill into each cut and zig-zag our way to the bottom of the slot. That way we can break up a deep slot into smaller steps that won't overly stress the endmill, and avoid the shock of suddenly forcing the cutter to remove too much material as soon as we move sideways after plunging: Anyone who spent time at school in the computer lab may recall programming FOR-TO loops or IF-THEN-ELSE evaluations using BASIC language. G-code features similar abilities to run repetitive milling operations and allow milling parameters to change based on variables. We can use this feature to implement our zig-zag slotting operation and make the code run more efficiently. Below is the first few lines of one of the raw fret slot G-code listings for our fret board. The code dealing with the first slot has been highlighted: Each fret slot is nothing more than a horizontal line between two points - X18.297 Y50.087 and X73.22 (the second instance of Y50.087 is not required as it only needs to be defined once when describing a straight horizontal line). Initially what we want is for the endmill to run repeatedly left and right between the two points . Using pseudo-BASIC code this could look something like the following (NB, there is no literal G-Code equivalent to a GOTO loop, this is just for illustrative purposes): Each subroutine must have a unique 'O' number. When the subroutine starts the cutter moves to X18.297, Y50.087. The next line plunges the cutter into the workpiece by 0.3mm. The slot is then cut with the endmill moving to X73.22 with Y unchanged. The endmill then moves back to its starting position of X18.297. (NB, the return X co-ordinate is simply copied from the original start point of the fret slot, three lines above it). The 'GOTO LOOP' command at the end of the subroutine returns us to the start and the process is repeated. Shuttle right. Shuttle left. Repeat. But we're still not moving the Z axis any deeper than 0.3mm, so no change in slot depth is being achieved. The other bug in this program is that because the 'G0 Z2' line falls outside the O100 LOOP it never gets executed, and the cutter remains stuck at a depth of Z-0.3mm. The next trick we need the cutter to do is gradually ramp the Z-axis down on each left-to-right run to increase the depth of cut. G-code allows the use of variables to substitue for direct co-ordinates. If we assign an automatically-changing variable to the Z-axis we could increase the depth of cut gradually to perform the ramping operation: Breaking this down line by line: A variable called #1 is assigned a value of 0 and a second variable #2 is created with a value of 0.3. On the first run of the subroutine the cutter will move to X18.297, Y50.087. The cutter then gets plunged to Z=0 (the value assigned to #1 gets substituted in place of the literal Z co-ordinate). The value currently stored in variable #2 (ie, 0.3) then gets subtracted from variable #1 (ie, 0) and the result stored back into variable #1, so now variable #1 has been updated to -0.3. The cutter then moves right to X73.22, and Z uses the new value of variable #1 as its destination. This creates the downwardly-ramping cut that we're after, starting from a depth of Z0 and finishing with a depth of Z-0.3. The cutter then moves back to its starting point of X18.297, but because Z is not listed it simply moves back at the last recorded depth of Z-0.3, flattening off the top of the initial ramping cut. The routine then returns to the top and runs again. Variable #2 once more gets subtracted from variable #1 and the result stored back into #1. But because #1 was set to -0.3 from the last run of the subroutine the new result of #1 - #2 (-0.3 - 0.3) is now -0.6. So when #1 gets used for the next Z co-ordinate it will ramp from -0.3 down to -0.6. With a bit of mental gymnastics it can be seen that on each successive pass of the subroutine Z will continually ramp down in increments of 0.3mm. But we still need some way of determining when we've cut the slot deep enough. At the moment there's nothing to stop the loop running for ever and giving us infinitely-deep slots. By changing our pseudo-GOTO loop to a WHILE/ENDWHILE statement we can place a limit on how many times the subroutine runs before it stops. Here's what the new version looks like: The WHILE/ENDWHILE loop will run until the expression evaluated by the WHILE statement is determined to be false. In our case we have specified that the G-code commands contained between the WHILE/ENDWHILE statements will run until the value stored in #1 is no longer greater than -1.5 ('GT' in the WHILE statement is short for 'Greater Than'). As variable #1 is being used to control the depth of cut within the subroutine and gets 0.3 subtracted from it on every cycle, when #1 eventually becomes less than -1.5 this will trigger the subroutine to finish and jump to 'G0 Z2' which retracts the endmill out of the bottom of the cut, ready to move to the next fret slot. Further refinement of this subroutine can be performed by removing or repositioning unnecessary or duplicated steps within the WHILE/ENDWHILE loop, giving: So now the only thing left to do is step through the remainder of the G-code listing, identify the start and end points of each fret slot and apply the same subroutines to them. Remember to use a unique O-number for each new subroutine. If you get stuck performing this manual G-code manipulation, both the raw and formatted versions are available to download at the end of this article to reference against, along with the DXF files used to generate the fret board geometry used in this article. ---------- In the next and final instalment we will get down to the nitty-gritty of using the fret slotting G-code and finally machine ourselves a fret board. We will also discuss some further ideas and applications of tiling on the CNC machine relevant to guitar building. Fretboard 24_6.zip

This tutorial is intended as a supplemental to Chris Verhoeven's "The Comprehensive Guide To Body Template Making" article here on ProjectGuitar.com; Chris' tutorial describes techniques for taking a printed design applied to a surface (in his instance, glued to thin sheet stock) and shaping that before transferring it to thicker and more permanent material. Presented here is an alternative method of taking a design printed in real-world sizes from your CAD package to that first bit of template stock. Chris' method is simple; print out your design and glue it to the sheet stock. Most people only have access to a standard format laser printer (Letter or A4). For obvious reasons, these might seem inadequate for the task since most of the templates we need to make (such as for body outlines) tend to be far larger. One solution might be to have your plan printed at a copy house straight to the appropriate size such as ANSI C or A2 which makes things a lot easier, even if it's a more expensive option. Printing a larger design over several small sheets and manually tiling them can be done within minutes, and with a little careful planning can be equally as accurate. Applying the page(s) to your target sheet stock can present a problem; spray glue is expensive, ridiculously messy and a pain to apply paper onto. Once it sticks, it goes nowhere! Equally, water-based glues have their own difficulties with the paper rippling and distorting. Without a large press, the paper bubbles and adheres poorly. Worse, when shaping a paper-based template the edges "fluff up" and obscure the lines we're trying to shape to. An alternative is to print directly to the sheet stock, or more accurately transfer a print. By taking the glues and reliance on paper out of the question, we can produce templates that are more permanent and far less hassle to produce overall. Toner Transfer Method Laser printers work by heating a solid ink powder ("toner") on a drum, physically pressing and depositing the molten ink onto the media. The toner transfer method reverses that process by using heat to re-transfer the toner from the media to the target workpiece. Why am I using the terms "target workpiece" and "media"? Media in this case is normally printer paper. We're going to bend this a little and use something a little different in place of standard paper. Secondly, "target workpiece" is down to this method having its roots in a different technique; homebrew PCB production. In that, rather than transferring toner to a sheet of MDF, hardboard or plywood it is transferred to a plain copper PCB sheet as a "mask" before etching the circuit design. The overall concept is the same. We temporarily print our design onto paper and transfer it elsewhere using heat. You will need: Glossy junk mail (with pages that will go through your printer) Painter's tape Craft knife or blade Steel ruler Clothes iron For this demonstration, I'll be transferring a doublecut bass design to a sheet of 5mm MDF. A little preparation work on your drawing is necessary. Firstly, I made a mirrored copy of the items I wanted to appear in my plan and increased the line weights to 0,5mm (~0.02in). Secondly, I created a custom printer setting which prints darker and turned "toner saving" off. Having heavier line weights and darker printing loads more toner to the print media, making it easier to transfer toner back off and to the target. Step 1 - Mark up your stock sheet I'll be tiling four sheets of paper in a 2x2 grid. To give myself reference, I drew a line across the centre of the MDF sheet and added a small mark midway across. All of the sheets will align along their longest side to this line, with the corners coinciding at this midway mark. Step 2 - Prepare for printing I chose a mail order catalogue which is slightly smaller than A4 for the print media. The paper is semi-glossy and fairly thin. Not all paper works the same for this process, so run through these steps to get familiar with the process and try a few test pieces first. The binding is a typical hot-melt glue type, so I ran a hot clothes iron along the spine and pulled off the covers. Whilst still warm the pages were easily parted into smaller sections. The residual bits of hot glue should be trimmed off otherwise they'll happily end up on your printer drum. This is NOT a good thing. I emptied the paper drawer and reset the guides to match the paper. On my computer I added a custom paper size corresponding to the physical dimensions of this paper which were 208mm x 279mm, or a little narrower than Letter. This gives you an idea of the print settings for my chosen CAD package, TurboCAD. The "real" paper size consists of 2 rows and 2 columns (set in "Layout") of my custom-defined paper size. The virtual drawing sheet size is a breakdown of the CAD plan automatically sized to the printable area. Most importantly the print is set to 1:1 scaling along with adding in the chosen alignment marks. Step 3 - Printing Send your print job to the printer and manually load one sheet at a time. Doing this reduces the chances of the paper pickup taking several sheets at once and causing a jam. Load the paper so that the print will end up on the side that is the clearest - you need to be able to see the print to trim up to it! Check that the print hasn't wrinkled or smudged, and that the alignment marks are visible. Check that the pages line up with each other without gaps/overprint and that the dimensions of the drawing are in fact 1:1 in both width and height. Step 4 - Transferral Firstly - using your steel ruler and a blade, trim the excess margins from the pages where they mate so that they butt up to each other perfectly. Align the edge and corner of the first page to the reference marks on your sheet and tape the four corners that the page lays as flatly as possible (unlike my example *cough*). (Finnish women don't look like this) Starting from the inside corner, place the iron on its highest temperature and leave it to sit for 10-15 seconds. After this, pick up the iron and place it further away from the corner with no overlap. Repeat this for the entire page. (actually, they're not screaming under the heat so at least they seem resilient like Finnish women anyway) What we're doing here is partially bonding the page to the sheet. The toner re-melts and sticks to both the iron and the paper. The page can be left a few minutes to cool, and then we can iron the page with some pressure! The glue on your painter's tape will likely melt during the ironing; making the pages prone to sliding and smudging the toner, so refine your technique with this in mind and don't drag the paper with the iron. Making sure than the sole of the iron is clean helps a great deal. After thoroughly pressing the paper down, the toner should ideally have "left" the paper and stuck preferentially to the target, hence why we used a glossier paper than standard printer paper; the bond between the ink and the glossier surface is weaker. Carefully peel the page backwards from the far corner, examining the transfer as you do so. If areas are missing, carefully re-apply the page and re-iron, taking care not to add in any misalignment as you do so. Ideally, you should end up with something like this: Transfers are rarely perfect due to a number of reasons; the cleanliness/smoothness of the target surface, and the paper used makes a difference. Your clothes iron needs to be as hot as it can manage. Again, find out what works best. All that remains is to repeat this process for all four sheets, aligning each one with the reference marks as carefully as you are able. The toner transfer method is not perfect by any means, and is subject to tolerance. Knowing how and when tolerances creep in is essential in keeping this technique accurate enough for its purpose. The lower-left sheet has a slight misalignment; things like this need to be borne in mind if any of the items you have transferred contain critical measurements. Manually check and re-check every precise dimension and marking for suitability, and re-draw them manually if needs be. Tips Include a long scale ruler on your drawing that occupies one sheet. This can help spot any dimensioning inaccuracies. Add a regularly-sized grid. 5cm or 2" gridlines expose any misalignment or distortion. Transfer the edges of guidelines to the other side. Place your sheet against a window and mark the locations of guidelines as they transition from one sheet to the next; this helps ensure that all sheets are aligned with each other since the print is on the underside. TURN OFF THE STEAM! Clean the (cold) iron sole with acetone before and after using the iron! Most importantly, you want the transfer work to go well. Secondly, you don't want to accidentally end up with melted toner or tape glue on your dress or your wife's dress shirt. Learn which things to include and not to include on your printed plan. Comprehensive is nice, but simple is clearer. This technique is also a great way of transferring photos or designs to a workpiece. Everybody knows that a gift of a cat photo on a 2x4 serves as adequate forgiveness for returning the iron with sticky toner on the sole.

If you're a regular visitor here at ProjectGuitar.com you may have caught our four-part series on using a compact desktop CNC milling machine and its application in lutherie. In the first instalment it was mentioned that a CNC is ideal for applications where precision and flexibility is required. One of which was milling fret slots in a fretboard blank, where positioning of the fret slots is crucial to the accuracy at which the resulting instrument can intonate, particularly in the higher registers where a small error in fret placement can result in a a major error in fretted pitch, The trade-off to owning a small CNC machine (or indeed any CNC machine) is that it has a practical limit to how big a piece of material it can fit within the confines of the milling area - the X, Y and Z axes can only move so far before they eventually run into the endstops, and no further reach of the cutter head is possible. If you take a guitar fretboard for example it will comfortably fit within the limits of one axis of even the smallest CNC machines - unless you are building some kind of 17 string monster most fretboards will not exceed more than about 70mm in width. The problem is that the fretboard length is usually in the vicinity of 500mm or more. To machine such a long object on your CNC machine in one hit obviously requires an axis with a reach of at least this length. There is, however, a way of expanding the reach of an axis so that you can machine objects bigger than the physical limits of your CNC machine. By milling the object in two (or even several) stages, moving and accurately repositioning the material midway through the process, it is possible to complete a complex milling operation on an object larger than the CNC router. This operation is known as tiling, and while it presents its own set of challenges and hurdles it is not unheard of to operators of CNC machines; tiling can be often be required no matter how big your CNC machine is - if the client requests an object bigger than your machine, if you simply don't have access to a larger CNC router you'll likely resort to tiling to complete the job. Successful tiling requires that the job be accurately repositioned partway through the milling process, such that the end of the first stage of milling aligns perfectly with the beginning of the next stage. This can be achieved through the use an indexing plate affixed to the CNC bed and a series of locating holes in the workpiece that align with matching holes in the indexing plate. Conveniently for us, we can use the CNC itself to create the indexing plate and holes to minimise any milling inaccuracies that may occur when changing positions. Creating the Jig Materials List: V-cutting engraving tool 1/8" diameter stubby rivet drill 6mm MDF sheet, approx. 600 x 450 12mm MDF sheet, large enough to cover table of CNC machine M6 or 1/4" nuts and bolts (20mm length) Four spare 1/8" drill bits, cutters or other solid rod material (to use as indexing pins) Glue, clamps, pencil, straightedge Patience Most CNC machine beds are made from slotted aluminium extrusions to allow the user to freely affix the workpiece to the bed using nuts and bolts. Our indexing plate will be rigidly secured to the bed and is made from a flat, smooth, easily-machined material - MDF suits our needs admirably. Cut a piece of 12mm-thick MDF large enough to cover the entire bed of the CNC. Neatness and squareness of this piece is not super-critical at this stage. With the MDF laid on the table carefully mark the locations of two outermost channels on the bed to allow us to drill some securing holes for the indexing plate. Drill a hole in each corner that aligns with the mounting channels used on the CNC bed. Use countersunk screws or otherwise recess the heads of whatever bolts you use to secure the plate to the bed. Once the plate has been drilled to accept the mounting hardware, return to the CNC machine and fit the plate to the bed. The slots on this machine will accept an M6 nut, the channels being narrow enough to prevent the nut from turning once the bolt is tightened. Mark a starting point about 50mm in from the left edge of the CNC bed. This will form the origin of a vertical line that will be engraved parallel to the long edge of the table. By using the CNC to scribe this line we ensure that the line engraved is square to the CNC machine's motion, rather than square to the table or MDF edges. This is essential for ensuring accuracy of the jig. Fit an engraver cutter to the collet. Home and touch-off the CNC to the indexing plate at the mark that was created. Most motion control applications include a manual G-code entry mode. This is useful if you want to perform some basic milling operations where generating a comparable G-code would be unnecessary or wasteful. If using LinuxCNC for example, click the 'MDI' tab in Axis (or press F5) to display the manual entry window. By typing G-commands one line at a time we can instruct the CNC machine to perform movements on a step-by-step basis. With the CNC machine homed and touched off to the MDF sheet, switch on the spindle and type the following lines into the MDI tab, pressing <enter> after each. Alternatively copy the below text into a blank G-code file, save and run it within your motion control software: G1 Z-0.5 F300 G1 Y280 G1 Z10 The above listing will lower the cutter to a depth of 0.5mm into the surface of the MDF, engrave a 280mm straight line up the Y axis and then retract the cutter out of the MDF to a height of 10mm, where the spindle can safely be switched off again. The line engraved on the MDF will form the reference to assist with assembling the next part of the jig. Using a piece of 6mm MDF cut a piece about 25mm wide and the same length as the CNC bed. Take care to ensure that one of the longest edges is as straight and square as possible (hint: the factory cut edge from a sheet of MDF is often very squarely machined - use this as the reference edge). This thin strip of MDF will form a fence for the indexing plate. Glue and/or screw the fence to the MDF indexing plate, lining up the square edge of the 6mm MDF to the engraved reference line as closely as possible. Be careful to ensure that the fence doesn't accidentally slip or move while the glue is drying. Using some more 6mm MDF, cut a baseplate large enough to comfortably hold a fret board blank with about 15-20mm overhang on all sides. For example, if your fret boards are nominally 60mm x 550mm, make the MDF plate about 100mm x 600mm. On one of the longest sides sand/cut/file/plane a nice, clean square edge. This edge will ride along the fence on the indexing plate and needs to mate with minimal gaps and bumps. For the next step we will need to create CAD drawing and resultant G-code program to drill the locating holes. The reason we do this is that the CAD drawing of the holes is subsequently used to determine the 'split point' of the fret slotting job when milling in two halves, Without an accurate reference for the split the two halves will never align properly when machined, no matter how well the jig has been constructed. In your favourite CAD program draw a rectangle representing the fret board holding plate at a scale of 1:1 (ie, 100mm wide by 600mm long) with a lower-left corner origin at X-5, Y-5. Make sure the rectangle is drawn vertically aligned such that the longest edge is in the Y-direction. Next, draw four vertexes/points in the locations shown - two positioned 5mm in from the bottom corners and two 5mm in from each side at the exact midpoint of the rectangle (hint: use object oriented snaps and draw reference lines to accurately position these points, and delete afterwards). The critical point is that by virtue of creating a rectangle with origin X-5, Y-5 and then offsetting each edge inwards by 5mm, the lower-left drill hole is at exactly X0, Y0. In the below example the points have been added on a new layer in red. The four points now need to be exported as G-code. When doing so, set the feedrate fairly low (say 50mm/min) and set the Z depth to -10mm. The resulting G-code should look something similar to the following. Note that I have broken up the listing a little and included some comments to better illustrate the four drill hole steps. Now we get to cheat a bit with the CNC machine. The collets on the smaller units are usually designed to accept 1/8" shank bits. A 1/8" 'stubby' rivet drill, with its short cutting flutes can also comfortably fit into the collet of the CNC machine, and can be used to accurately drill the workpiece locating holes for the jig. Re-install the MDF indexing plate and lay the fret board MDF plate on top with the reference edge hard up against the fence. Position the leading edge of the fret board plate flush to the front of the indexing plate and secure in place with some temporary clamps. Fit a 1/8" stubby drill bit to the spindle and tighten securely. Open the drill hole G-code in your motion control software. Home and touch-off the tip of the drill bit such that X0, Y0 is 5mm from the bottom edge of the fret board plate and 5mm from the left edge - this is where we want to begin drilling the four holes. Turn on the spindle and run the G-code - four holes will will be drilled into the holding plate and through to the indexing plate. The final step of creating the jig also serves to illustrate how the tiling technique is performed. Remove the temporary clamps and slide the fret board holding plate down such that the top two holes are now positioned over the bottom two holes in the indexing plate. Insert two spare 1/8" shank cutters or drill bits into these two holes, locking the holding plate to the index plate, and temporarily clamp the top of the holding plate in place to prevent it shifting from side to side. Open up the G-code for the four locating holes and edit out the lower two drill hole entries (hint: enclose the relevant lines within brackets to convert them to non-executable comments). We obviously don't want to re-mill the first two holes, not the least because we now have two pins inserted into them, but we do want to mill the second pair of holes again for the top section of the fret board holding plate. Note that the X90 co-ordinate has now been added to Y295. As the previously defined X co-ordinate has now been disabled it needs to be moved to the new 'initial' drill hole position, which is now at the upper-right corner. Save this file and re-open within the motion control software, but do not re-home or re-touch off the machine. Run this G-code again and note that only the top pair of holes are drilled into the holding plate through into the pre-existing holes in the indexing plate. The jig is now complete and ready to be used. By using four 1/8" pins and securing the holding plate at the lower position the first half of the job can be machined. When this operation is complete the pins are removed, the plate shifted down, the four pins re-inserted and the second half of the job run with perfect alignment between the two halves. ----==---- In the next installment we will delve into formatting and splitting an over-sized job into the requisite halves such that the milling of a fret board can be achieved, and also learn a little about optimising our G-code to run a little more 'intelligently'.

2D or even 3D CAD software is familiar to the majority of people, with packages like AutoCAD or TurboCAD. being more or less universally known. CAM software on the other hand is not so familiar. The simplest difference is that CAM takes work produced in CAD and uses it as the basis for a real-world manufacturing process. In this instance, a CNC machine. Numerous CAD and CAM packages are available to the user, from free to painfully expensive. For this tutorial we will focus on QCAD by Ribbonsoft. The software is relatively inexpensive (licenses start at 33EUR) and is available for a resettable trial period. This enables users to get to grips with the basics, and is reasonably easy for a CAD novice to understand. QCAD is also cross-platform compatible available on Windows, Mac or Linux machines, and it includes a basic CAD -> CAM interface adequately servicing our needs. On opening QCAD the user is presented with a blank document. I am working in Metric, however if you choose to work in Imperial units it is easy to switch between the two units of measurement in the program Preferences. The underlying methods are unchanged of course. To begin with, we will draw a rectangle with dimensions of 35mm by 45mm. The keyboard shortcut, typing 're' activates the 'Rectangle' command. The cursor will change to a set of yellow crosshairs, indicating a command has been invoked and is active. The command line at the bottom of the screen indicates that the rectangle command is waiting to for the user to specify the coordinates of the lower-left corner of the rectangle. With the rectangle command still active, click in the command line window where it requests 'First corner:' and type '0,0' (note the comma separating the two zeroes) and press <ENTER>. To complete the rectangle command we also need to specify the coordinates of the upper-right corner. In the command line window type '35,45' and press <ENTER>. The rectangle is drawn on the screen with the exact dimensions of 35mm x 45mm. Often when drawing in CAD packages, it is useful to add guidelines to help you work. These are erased when the drawing is complete. In this example it is handy to draw a centreline for our trussrod cover. Click the right mouse button to cancel the Rectangle command or press <ESCAPE>. Same as we did to invoke the 'Rectangle' command, type 'li' to activate the 'Line' command. By moving the yellow cursor near the top edge of the rectangle you will note that the word 'Middle' appears. This is an automatic object-oriented snap that allows us to select a key property of items already drawn on the screen with absolute accuracy. Other object-oriented snaps include the centre of a circle, an intersection between two objects or the end of a line, amongst others. In our case we will draw a line from the middle of the top edge to the middle of the bottom edge of the rectangle. Click the middle of the top edge to start drawing the line and click again on the middle of the bottom edge to complete the line. Right-click to stop drawing additional Line segments and right-click again to cancel the Line command. To give the trussrod cover a bit more visual appeal we will curve the sides in a kind of bullet shape. To achieve this we will take advantage of object oriented snaps again. Type 'a2' to start the 'Arc With 2 Points and Angle' command. Using the object oriented snaps click on the top of the centreline to start drawing an arc. While the end of the arc is 'attached' to the cursor, click in the Angle box at the top of the screen and type '45'. To complete drawing the arc click on the lower-left corner of the rectangle. The mirror image can be drawn while the Arc command is still active. Left-click the lower-right corner of the rectangle and click again at the top of the centreline. Note that this time we have gone from bottom to top. This is because the Arc command relies on an anticlockwise rotation when being defined. Clicking top to bottom would generate an arc facing the opposite direction. While this can be reversed so that the arc is drawn clockwise by changing the drawing preferences, it is quicker to remain in anticlockwise notation while the command is still active from the first arc. Right-click to cancel the Arc command. Now that the trussrod cover is starting to look roughed out, lets refine the shape a little. The three corners of the cover can be rounded over slightly by invoking the 'Round' command. Type 'rn' to start it. In the radius box at the top of the screen type '2.5'. Left-click one of the two arcs on the trussrod cover near the peak. Note that as you go near each entity it changes colour to grey. Move the cursor near to the other arc. Notice how QCAD offers 'suggestions' as to where the round-over will be if you left-click again. Click when the round-over of the peak becomes one of the suggested options on the screen. The two remaining bottom corners can also be rounded over using the same process. Right-click to cancel the Round command when finished. To finish off the cover we'll add some screwholes at each corner. The easiest way to achieve this is to use the existing outline and offset the edges inwards to provide some useful guidelines (we'll delete these once finished). Type 'lp' to invoke the 'Parallel Lines with Distance' command. In the distance box at the top of the screen type '2.5'. As for the 'Round' command, hover the cursor near each edge of the trussrod cover, and when QCAD's suggested location for the parallel line appears inside the boundary of the cover, click the left mouse button to create the new parallel line. Repeat for all three edges. Cancel the Parallel Lines command when finished. The screwholes are simply circles placed at the intersections of the parallel guideline we just created. Type 'ca' to start the 'Circle With Diameter' function. In the diameter box at the top of the screen type '2'. Move the mouse over each of the corners of the parallel guidelines and left-click when the object oriented snap 'Intersection' appears. Cancel the Circle command when complete. All the unwanted guides can now be removed from the screen. To do this simply select all of the unwanted entities in turn while holding the <SHIFT> key to create a multiple selection. When all have been selected (indicated by the colour changing to brown) press <DELETE>. So we now have the drawing of the trussrod cover complete, but there is still a little more work to do before we can pass it on to the CNC machine. The main issue we have to resolve is that the diameter of the cutter needs to be compensated for in order to properly cut the outline of the cover. Without any toolpath compensation the cutter will follow the outline of the part and create a profile too small by the radius of the cutter. This is perhaps best illustrated by overlaying a representation of the cutter on top of the trussrod cover. In the above image the green circle represents the diameter of the cutter we want to use on the CNC machine. If the cutter follows the outline of the cover it will create a part that is represented by the yellow dotted line, which is obviously smaller than we want and also encroaches on the screwholes. What we need to do is offset the outline of the cover by a distance equal to the radius of the cutter and have the cutter follow this path instead. The other issue to be dealt with is the drilling of the screwholes. Again, if no compensation is performed with our basic drawing the CNC machine will simply move the cutter in a circular motion around every screwhole and leave us with oversized holes. What we really want to do is use a cutter with the same diameter as the holes we want to drill and simply plunge the cutter in and out of the centre of each screwhole location. Turning first to the outline path, we need to create a separate drawing layer that contains only the toolpath we want the cutter to follow. To create a new layer click the red '+' button in the Layer List menu box on the right of the screen. In the popup dialogue give this layer the name 'Toolpath' and change the colour to red. Click OK when done. Make sure the new Toolpath layer is selected in the Layer List and invoke the Parallel Lines command ('lp'). We will use a 2mm diameter cutter on the CNC machine, so we want the toolpath to be offset from the outer edge of the trussrod cover by the radius of the cutter. Enter 1 in the Distance box. Hover over each of the outline entities and click to create an outside offset. Cancel the 'Parallel Lines' command when done. The screwholes are easier to deal with. Assuming we continue to use the same 2mm cutter on the CNC machine, this will drill a 2mm diameter hole when plunged in and out of the workpiece. To create a toolpath that only moves the cutter in a vertical drilling action we simply place a Vertex or Point in the centre of each screwhole. Type 'po' to invoke the 'Point' command and using the 'Reference' object snap, click in the centre of each screwhole. We can now export the drawing as a G-Code file that can be interpreted by the CNC motion control software. Hide the original drawing of the trussrod cover by clicking the 'eye' symbol in the Layer List next to the '0' layer. The original white outline disappears from the screen leaving only the red Toolpath layer visible. Click on the 'CAM Export' button on the toolbar to bring up the CAM Configuration dialogue box. Select the 'LinuxCNC' configuration from the dropdown menu and set the other options as shown below. The important settings to take note of are: Cut inner paths before outer paths - the order that the CNC machine cuts the object from the material can be important. For this reason we want to drill the screwholes before the outline is cut out. If the outline were cut first there is a risk that the part may move as it becomes free of the surrounding material, rendering the drilling of the screwholes innacurate. Z Safety - the distance the CNC machine raises the cutter by to a safe amount from the workpiece to allow for the machine to be started and stopped. Z Clear - the distance the CNC machine will raise the cutter above the workpiece when rapidly jogging between different areas of the workpiece. Z Cutting - the distance the CNC machine will plunge into the workpiece when performing a cut. As we are wanting to cut the full thickness of the trussrod cover material and drill all the way through for the screwholes, this depth should equal the thickness of the material we are attaching to the cutting bed. In our case we are using some black plastic pickguard material 0.095" thick. Feedrate - The speed at which the CNC machine will move the tool when cutting through the workpiece. In all the above cases the units are expressed in inches or inches per minute. Once all parameters have been set click 'OK', specify a file name and select a convenient location on the computer to save the G-Code to. Start LinuxCNC and open the G-Code file for the trussrod cover. You will notice that the program is drawn such that all cuts are made in one pass at the full depth of 0.095". Doing such a heavy cutting manoeuvre with the tiny bits that the CNC machine uses is likely to destroy the cutting tool. The forces involved are too great for a small machine and such fine cutters. While the three screwholes are fine to be cut to full depth in one go, the outline is not and would be better performed if the cut was made in several passes. Fortunately this can be achieved with some minor tweaking of the G-Code file within LinuxCNC. Different modifications or approaches can be used to achieve the same end result. For the purposes of simplicity, we'll use the easiest approach. With the truss rod cover G-Code file loaded in Axis click File -> Edit... A text editor window opens with the G-Code loaded. The section of code that details the outline cut is highlighted below, beginning with the G1 plunge to Z-0.095 at line 14 and ending with G3 X0.0982 Y-0.0394 I0.1378 J-0.0026 at line 20. By repeating this section of code several times over and incrementally plunging a little deeper each time we can complete the cut in several passes without stressing the cutting tool. The easiest way to achieve this is to simply copy this block of G-Code several times over and increment the initial Z depth a little during each pass until the final depth is achieved. With the above code modified as shown click the 'Save' button in the text editor. Return to Axis and click the 'Reload' button or press <CTRL-R>. The G-Code is reloaded into Axis, but notice that the truss rod cover outline now contains three identical tool paths stacked on top of each other. Leave the CNC machine switched off at this stage, home all three axes and run the G-Code. By running the code with the machine switched off it is possible to see a simulation of what will be cut before committing the cutting tool to the material. As the program runs note that the outline cut is made in several progressive layers; each time the tool passes the start of the outline at the lower-left corner it plunges to the next depth and continues around again until the final, lowest outline is completed. If the simulation appears OK turn the CNC machine on, fit a fresh piece of material to the cutting bed (double-sided sticky tape is sufficient for such a small piece), install a 2mm diameter cutter to the collet, home and touch-off the tool and run the G-Code again. In a couple of minutes you should have a perfectly formed truss rod cover ready to be fitted to an instrument. ---------- Over the course of this four-part series we have demonstrated how the compact CNC machine can open up a whole new world of possibilities in guitar construction. While we have created a rudimetary truss rod cover from scratch, we have barely scratched the surface of what the CNC machine can achieve - from carving out custom pickup rings, creating workshop tools and aids to assist with instrument building and setting up, to engraving and carving intricate designs onto headstocks and fretboards. For a modest outlay of money it is possible to have a device in the workshop capable of precision that, up until the last 15 years, was the domain of the largest manufacturing firms. After mastering basics such as those described above, experimenting with more complex ideas and demanding designs quickly allows a small CNC to transform your working procedures.

After going through the StepConf Wizard to set up our CNC router LinuxCNC will have created a shortcut on the desktop to allow us to run the CNC machine with our configuration. Double-clicking this icon will launch Axis, the default graphical user interface. Upon opening Axis the user is presented with a 3D representation of the physical machinable cutting area of our CNC machine. A default test cutting program is loaded on startup featuring the LinuxCNC logo and a small cone object in the preview window represents the position of the CNC cutting tool. The maximum bounds of movement of the CNC machine, as defined by StepConf Wizard in part 2 of this series, are represented as a rectangular cuboid object with dotted red edges. In our case the cube is 200mm wide, 300mm long and 50mm high, which aligns with the maximum limits of travel of our particular CNC router. Take a fresh piece of plywood, MDF or other flat material at least 150mm x 150mm and secure it to the table. Fit a small engraving cutter to the spindle and tighten the collet. Open a blank text document using whatever text editor you prefer to use on your system and enter the following G-Code. If your machine is set up for millimetres use the left column. If you’re running your machine in inches use the right column: Save this file as ‘100square’ with the file extension ‘.ngc’ to a convenient location on your computer. Using the metric version, let’s break the code down into its components: G21 – This command tells Axis that the units of measure contained in the following code is expressed in millimetres. If G20 is used then the units of measure are inches. G0 Z15 – the G0 command instructs the CNC machine to linearly move its axis or axes at maximum velocity. This is useful to speed up moving from one area to another in preparation for the next cut, but should not be used when actually cutting as the speeds and forces involved could damage the tool. Z is the axis that is to be moved and the number immediately following is the position the axis is required to move to. In effect this line is commanding the CNC router to raise the Z axis to 15mm above the surface of the workpiece at maximum speed. G0 X0 Y0 Z5 – The CNC machine is again required to execute a rapid move, but this time we have also included destinations for the X and Y axes (X0 and Y0). Z axis is also instructed to lower to 5mm (Z5). G1 X0 Y0 Z-0.5 F300 – G1 tells the machine to linearly move at a rate which is specified by F300, expressed in units per minute. Because the Z axis is required to move to a negative value (Z-0.5) we are now plunging the tool into the workpiece to begin cutting and a slower axis velocity is required. X and Y axes are set at 0, but because we already moved to X0/Y0 in the previous step there will be no change in these two axes. G1 X100 Y0 Z-0.5 F300 – G1 again instructs the machine to use the feed rate F300. The X axis is requested to move to 100 while maintaining Y at 0. This will result in the X axis moving to the right in a straight line to a distance of 100mm. The Z axis remains at the same value as previously commanded by the G1 instruction. G1 X100 Y100 Z-0.5 F300 – The machine will move Y up to 100 at low feed while keeping X at 100 and Z at -0.5. G1 X0 Y100 Z-0.5 F300 – The CNC router will move X axis back to 0 at low feed G1 X0 Y0 Z-0.5 F300 – The Y axis is reduced to 0 at low feed. G0 X0 Y0 Z15 – The Z axis is raised to 15mm above the surface at maximum rate. The cutter is withdrawn from the work piece. M2 – This command signifies the end of the program and the CNC can stop operation. Many G-Code commands and variables are ‘modal’ and remain in effect until another contradictory command is executed. As an example the above program could be re-written for maximum modality and provide the exact same output. The drawback is that it can become difficult to read to the user, as much of the detail is removed: You will note that the F300/F12 feed rate that originally appeared at the end of each G1 line now features at the top of the program. This is because each successive G1 command will utilise the last known feed rate, which is now defined at the beginning of the code. Returning to Axis it can be seen that on start-up the location of the cutting tool is exactly at the upper-left corner of the machine limits of travel (X=0 and Y=0) and the tip of the cone is positioned at maximum height (Z=0). This corresponds with the home position that was defined earlier while running the StepConf Wizard. In reality the cutting head could be physically located anywhere within the limits of travel, as is the case below: Before the CNC router can be operated it needs to be returned to its home position. On more advanced machines this procedure can be automatic, with the axes seeking their home positions when the user commands the machine to home itself. In our case we will home the machine manually. Click the File open button or press <O>, navigate to where you saved the G-Code program we created and load ‘100square.ngc’. You should be presented with the following in the preview window: Check the Emergency Stop pushbutton on the CNC router control interface has been reset, and press <F2> or click the ‘Toggle Machine Power’ orange button on the top menu bar. A number of greyed-out options under the ‘Manual Control’ tab become active. With the CNC machine connected to the PC and powered-up, use the four arrow keys on the computer keyboard to move the machine around the cutting bed in the X and Y directions. The <page up> and <page down> keys will also move the Z axis up and down. Manually moving the cutting head around the table is called jogging. As the cutting head moves around the display updates the position of the cone object and shows the path taken as a solid yellow line. In the below example the cutter has been jogged towards the front edge of the table by 31.739mm (Y axis), across to the left 21.547mm (X axis) and up 20.545mm (Z axis). These values appear in the upper-left corner of the display; the Digital Read-out or DRO: The CNC machine, having now executed the above moves is sitting with its cutting head physically home, but well away from the workpiece at a distance which does not yet correspond to the values shown in the preview window: Now that the CNC machine itself is at its home position Axis needs to be told that this is now the position that corresponds with the upper-left corner of the red dotted-edged cuboid object, ie the 'soft' home position. The ‘Home Axis’ button is then clicked for each of the X, Y and Z axes. As each axis is homed the DRO updates to indicate that the associated axis is at position ‘0’ and a symbol is added next to the readout. Note also that the position of the cutting head in the preview window returns to the upper-left corner of the work area box to reflect the fact that it has now had its home position reset. The second step to perform before we can run a job is to ‘touch off’ the cutter against the workpiece. This is the process of setting the position of the workpiece relative to the home position of the machine. With the CNC router homed the job can be run, but unless the tool is touched-off Axis does not know where the workpiece lies relative to the tip of the cutting tool. In the above example the square object looks as if it sits bang-up against the top of the limits of travel, when in actuality the workpiece is about 25mm below the tip of the cutter and a few inches inside the edges of the table. Without touching-off, at best the machine may run the job with the tool completely missing the workpiece. At worst the CNC may try to drive the cutting tool through the workpiece into the table, ruining the job, damaging the table and destroying the cutting tool. To touch off manually jog the cutting head to the point at which you require the origin of the job to be positioned on the material. In the below example the cutting head has been jogged right 34.071mm (X axis), jogged away from the front of the table 42.856mm (Y axis) and jogged vertically down by 22.156mm (Z axis) to place the tip of the cutter at exactly the spot where the job origin is required to be. In our case I have marked the workpiece with a cross to indicate where I want the square shape to begin: As each axis is moved into position click the ‘Touch Off’ button. A dialogue box opens to allow the user to manually specify an additional offset to the workpiece relative to the axis being touched off, but in most cases it is sufficient to use the default of 0. After touching off the axis the DRO updates to show the position of the cutter has now been reset to 0. Note also that the square object has now moved 'deeper' into the red cuboid object that defines the limits of machine movement. Click the ‘Clear Live Plot’ button or press <CTRL-K>. This clears the preview window of any paths that were created by the manual jogging of the cutting head. Manually jog the cutter away from the workpiece a few centimetres. With the machine homed and touched-off we are now ready to run the job. If the CNC machine has a manual spindle control turn it on and set the spindle speed appropriately. Click the blue ‘Play’ button or press <R>. The CNC machine and preview window will now begin stepping through the code and manoeuvring around the workpiece. Note that the movement of the cutting head in the preview window is indicated by pale red lines for slow cutting motions, and for rapid jogging motions between each cut the tool follows the cyan dotted lines without leaving a trail. After a few minutes the program completes and the cutter retreats away from the workpiece to a safe distance where the spindle can now be turned off. If all things have gone to plan you should now have the 100 x 100 square engraved on your workpiece. Take a good quality ruler or Vernier calipers and measure each of the four sides of the engraved square and confirm that they each measure 100mm. If the sides of the square do not equal 100mm then some tuning of the configuration file must be undertaken to correct this error. The most likely culprit is that the lead screw pitch has been incorrectly set. The correction factor to apply to bring the axis scale back to the correct value is: If the square is exactly out of scale by a factor of two the other possibility is that the 'Motor Steps Per Revolution' setting is out by a factor of two. Doubling the value of 'Motor Steps Per Revolution' will make the edge of the square twice as big, whereas halving this setting will reduce the length of the square’s edge by half. ---------- Now that we have the CNC router actually cutting something and each axis is scaled correctly, we can move on to creating something a little more exciting. In the next instalment in the CNC series we will create a truss rod cover from scratch using CAD and mill it on the CNC router.

So you’ve decided to launch yourself into the world of CNC machining. You’ve done some research and lurked around many online forums and resources looking for information regarding which model to choose and what features the unit needs. You’ve plonked down your hard earned cash and a big cardboard box has arrived in the mail containing a bright, shiny new CNC router. It’s been assembled and set up on your desk. Now what? Fundamentally, most basic CNCs will have a bed which workpieces are secured onto and a overhead gantry that travels the length of the table. Onto this gantry a secondary carriage travels over the width of table. The spindle itself is attached to this carriage and can move vertically. The spindle rotates a cutting tool at high speed to remove material from the workpiece. The three movement directions (side-to-side across the table, up and down the length of the table, vertically up and down perpendicular to the table) are the three axes of motion that the machine can operate in; X, Y and Z respectively. Each axis is independently controlled by specialised motors known as steppers, which are designed to rotate either direction by precisely known amounts. The rotation of these motors is translated into simple linear movement (backwards and forwards). Commonly, threaded rods ("lead screws") pulleys or toothed belts are used for this purpose. Larger machines can sometimes use these in combination (such as pulleys for X and Y, leadscrew for Z). Each have their respective advantages and disadvantages in accuracy, cost, speed, load capacity, etc. Lead screws are most common in small CNCs for all three axes. The precise rotation of the stepper motors is controlled through the application of electrical pulses. By co-ordinating the number, length and frequency of the electrical pulses, the CNC machine can be made to execute precise synchronous motions to move the cutting tool around the workpiece in complex paths. The generation of these control pulses is performed either by dedicated standalone control consoles or by software on a common computer. Non-production level CNC tends to utilise the second option; the steppers driven by a simple external interface unit that sits between the machine and PC which handles the translation of the software stepper signals into the heavier-duty control signals that drive the motors. Software generation requires that a motion control application be installed on the host computer. Two of the most popular motion control solutions at the moment are Mach3 or Mach4 (for Windows based computers) and LinuxCNC for (Linux-based operating systems). In this article we will use LinuxCNC to illustrate how to set up the desktop CNC router; fundamentally the operating principles are similar between the Mach-series software and LinuxCNC. Both options require the host computer to have a parallel port for communicating with the control interface. Laptops and USB-to-parallel adaptors are not recommended for software stepper pulse generation. The main advantage of favouring the "old" parallel port standard is that many signals can be sent simultaneously; despite being far faster, USB is purely serial and asynchronous; one piece of information at a time and "arrives when it arrives". Parallel is far closer to being a real-time interface, which USB to parallel adaptors do not reliably replicate. PCI parallel port cards on the other hand are a satisfactory option if your host computer doesn't feature a parallel port. Installation of a Linux operating system and the LinuxCNC application is beyond the scope of this article, however it is extremely simple; LinuxCNC is available as a LiveCD installation, whereby the user has the ability to boot a pre-compiled version of LinuxCNC from a CD, DVD or USB memory stick without installing the operating system onto the computer. This operating system image is available to be downloaded from the LinuxCNC website. A permanent installation of Linux and LinuxCNC can be performed from the LiveCD if the user so chooses at a later date. The first requirement in setting up the CNC machine is to create a configuration file. This contains the specifications of the CNC motors so that they are driven at the correct speed/rate, acceleration, direction, etc. From the menu bar Click ‘Applications’, navigate to ‘CNC’ and select ‘LinuxCNC StepConf Wizard’. If this is the first time that StepConf Wizard has been run a new configuration must be made. The user also has the option of opening an existing configuration to either adjust existing settings in their recently created configuration, or use another configuration as the basis for their new CNC router. In this case we will create a new configuration from scratch. Click ‘Forward’ to move to the next page in the StepConf Wizard. In the next screen the configuration can be given a meaningful name and basic setup parameters defined, such as units of operation (millimetres or inches), how many axes the machine operates with (in our case three axes – XYZ), parallel port addresses and driver signal timing. If your CNC machine comes with data or a user manual then use this to set the driver timing settings. If there is no data supplied you may have to search online to find some information regarding the suggested timing parameters, or experiment to find the best trade-off for reliable operation of the CNC router. Step Time and Step Space - the width of the electrical pulse applied to each stepper motor and the subsequent gap between each successive pulse, expressed in nanoseconds. Too small a step pulse or space and the motor will miss a step. Too long and the CNC axis movement can become unacceptably slow. Direction Hold and Direction Setup - In addition to the step pulses themselves, secondary signals are generated by the motion control software that change the order of the pulses being applied to the steppers. Changing the order of the pulses changes the rotation of the motors from clockwise to anti-clockwise. The "Direction Hold" and "Setup" parameters define the amount of time the direction signal applied to a stepper motor needs to remain activated after a step pulse has been issued, and the amount of time the direction signal needs to be applied to the stepper before issuing the next step pulse. Too small a direction hold or setup and the motor can miss a change in direction and overshoot its intended stop point. Too long and the CNC axis movement can become unacceptably slow. In most cases the values shown will work as-is and require no further adjusting. The last key item that requires attention on this page is the ‘Base Period Maximum Jitter’ setting. Instructions to the CNC (via the interface) are generated by software, so there is a potential that something occurring in the computer or operating system outside the control of the CNC machining application may interrupt the continuous supply of timely instructions (eg. graphics redrawing on the screen, hard drives being accessed, etc). Consequently we need to ensure that any interruptions that do occur do not interfere with the normal operation of the CNC machine. To find out what this minimum safety net should be the StepConf Wizard includes a ‘Jitter Base Period Test’ function. After running the test for a few minutes this returns a suitable ‘Base Period Maximum Jitter’ value. This states how much the system might be expected to be delayed during normal operation; the configuration then makes sufficient allowance to avoid interruptions in the generation of the stepper control signals. Click ‘Forward’ when all fields have been filled in. Leave the Advanced Configuration Options unchecked at this stage and click ‘Forward’ again. The Parallel Port Setup screen is where we define what each pin of the parallel port on the computer is expected to do when connected to the CNC machine. Again, consult any data or the manual supplied with the CNC router to determine how each pin is to be connected. As we are configuring a basic 3-axis machine the minimum required pins to be configured will be X Step, X Direction, Y Step, Y Direction, Z Step and Z Direction. The other important pin to configure is the Emergency Stop (or E-Stop) input from the machine. Nearly all CNC machines will be fitted with a large E-Stop switch that the user can hit in the event that the machine begins executing some unintended moves, and signals the motion control software to unconditionally stop moving the axes. The next three screens are used to configure the behaviour of each stepper motor; their speed, acceleration and limits of travel. Each axis is configured independently but the options presented are identical: Motor Steps Per Revolution – how many steps the motor needs to perform to complete one full rotation of the shaft. Manufacturers of stepper motors often express this value as degrees per step. If your stepper motor has this value specified as 1.8 degrees per step then Motor Steps Per Revolution is equal to 360 degrees divided by the degrees-per-step value, or 360/1.8 = 200. Driver Microstepping – the resolution of a stepper motor can often be increased by the action of microstepping. The basic degrees-per-step specification of the motor is enhanced by the driver forcing the motor to make an intermediate ‘soft’ step in between each 1.8 degree ‘hard’ step. In the same way that a picture with higher resolution can display more detail on a computer screen, a stepper motor with more resolution can perform finer movements. The trade-off is that the more microstepping you add the less torque that motor is able to generate. In practice a microstepping value of either 2 or 4 is a good compromise. Note that if you set microstepping to 2 it will require that Motor Steps Per Revolution be increased to 400 to maintain the relationship of the number of steps to complete one revolution of the motor shaft. Setting microstepping to 4 will require Motor Steps Per Revolution to be set to 800. Pulley Teeth – only required for CNC machines that use pulley systems to drive the axis. This is where you would specify the gearing ratio of the pulleys. We are using a lead screw in the desktop CNC machine so leave these two fields set to 1. Leadscrew Pitch – the pitch determines how far each axis will travel when the lead screw is rotated one full revolution, and its setting is critical to ensure that the axis travels the correct distance when commanded to do so. If the units of operation specified earlier were inches then the lead screw pitch is expressed as threads per inch. If millimetres were specified then this value is expressed as millimetres per revolution. Consult your CNC machine datasheet for information on the specifications of lead screw fitted. As an alternative most lead screw pitches can be measured reasonably accurately by using a ruler to count the number of thread ‘peaks’ within one inch, or the distance in millimetres between two successive thread peaks. Maximum Velocity and Maximum Acceleration – sets the maximum speed and acceleration of the axis before the CNC machine starts missing steps or losing accuracy when changing directions. As no real life object can accelerate from a standstill to full speed instantaneously, we need to specify a value in the ‘Max Acceleration’ field to limit how quickly the CNC motion control software tries to make the machine change its speed when either accelerating from zero, coming to a stop at the end of a manoeuvre, or changing directions suddenly when transitioning between two trajectories. In general this is set by experimentation with your particular machine, but the values presented here should work with the smaller desktop CNC routers as a starting point. Home Location – the default location the axis will set itself to when the machine is told to ‘return home’. The home location can actually be anywhere you like within the axis limits of travel, but is typically set at 0 (which would equate to the lower-left corner of the table with the Z axis at maximum height). Every time the software is started up the physical location of the CNC machine is undefined. Until the CNC machine is homed it cannot know where its limits of travel are (below) and therefore cannot commence a machining job. Table Travel – specifies the ‘soft’ limits of motion that the axis can move within, and is expressed as either millimetres or inches depending on how the units of operation were set earlier. For each axis this is typically set to the maximum travel that the axis can move to before reaching the end stops. When the motion control software detects that the axis has reached its soft limit it will not attempt to drive the CNC router beyond this value. Note that when setting the Z axis the Table Travel fields are normally set as a negative number to zero, rather than as zero to a positive number. The convention here is that the Z axis moves negatively with respect to the surface it is bearing down upon. The last option for each axis is the ‘Test this Axis’ function. Clicking on this will bring up a window that allows the user to see if the configuration created thus far is appropriate for their machine. With the CNC router connected to the computer and powered up the axis under test can be manually moved using the two ‘Jog’ arrow buttons, or the axis can be set to automatically swing back and forth by a set amount according to the ‘Test Area’ fields. This is useful for determining if the axis is moving by the correct amount based on the ‘Motor Steps Per Revolution’ and ‘Lead screw Pitch’ settings, and also if the ‘Max Velocity’ or ‘Acceleration’ settings are going to result in missed motor steps. Assuming that step direction was set up correctly earlier under the ‘Parallel Port Setup’ window for each axis, clicking the right ‘Jog’ arrow should make the X axis move towards the right of the table, the Y axis move away from the front of the table and the Z axis move vertically upwards. Clicking ‘Forward’ after configuring the last axis and then ‘Apply’ will create an icon on the desktop allowing the user to launch the motion control software using the created configuration file. And that’s it! If you’ve made it this far you’ve successfully created a configuration file to suit your CNC router. By double-clicking the 'launch CNC-router' icon on the desktop, the configuration file will pre-load all the necessary parameters for the CNC machine and start up the motion control software. ---------- In the next article we will begin creating a basic G-Code file to run the CNC router with. In doing so we will also verify that the machine operates correctly, and the axis motion is correctly scaled to create 1:1 cuts in preparation for applying the CNC machine's abilities to creating luthiery-related components.

Adhering to some form of best practice is not a necessary pre-requisite of a useful CAD plan. In a non-professional capacity a CAD plan only has to be fit for the purpose it is intended for, rather than following an established set of standards and work templates. That said, giving a passing nod to best practice helps improve the quality and reliability of your plans, personal working methods and raising your game. Google search results for "guitar CAD plan", "guitar dxf download", etc. reveal a hugely varying level of detailing and usefulness. Some "plans" exist as nothing more than a body outline whilst some illustrate every last part of every single component. The answer to "which of these is better?" is not always the expected answer; neither. You've probably already switched off by this point, wondering why you can't just draw what you need to draw and "git r done". That is exactly the point! Your CAD plan only needs to be useful for its intended purpose. The "basic body outline" example is usually because that is all the designer personally needed at the time. Overly-detailed plans ensure that every single bit of useful information for every type of end user is within that one drawing. Either that or it makes a great poster for your shop wall! Do we need some form of best practice? No, but your CAD work will always benefit from a consistent and methodical approach, whichever of the two extremes you fall into. A good plan generally demonstrates: use of guidelines and reference geometry grouping of parts by layer and/or colour straightforward representation without unnecessary detail or ambiguity fitness for the intended end use annotation, readability and easy derivation of measurements These might seem like too much to bear in mind, however they all have a direct bearing on how well your technical drawing work translates to organising work in the shop and the final finished item. Best practice makes your CAD plans productive and useful. Guideslines/Reference Geometry Guitars have a very common underlying structure around which the rest of the instrument is built. For example, a centreline is fundamental to 99,99% of instruments work from. Reference geometry is the structure around which the rest of the instrument is defined. Without it, measurements become unreliable or impossible to acquire. Grouping Individual primitives (lines, arcs, etc.) representing a composite shape (such as a pickup rout) should be separable or at least identifiable from others. Simple colour differentiation, discrete grouping or separation by layers organise your geometry. Without grouping, complex drawings become impossible to interpret usefully. Straightforward representation How much information do you need in your plan? Do you need to draw all of the knurls around the nut of your toggle switch, or would it better be represented as a 1/2" circle and a centre point? Superfluous detail clouds communication of useful information. Structure, relevant grouping and useful visual communication produce easily-navigable and understandable plans. Fitness for purpose What is the drawing for? Does it convey required information as comprehensively and accurately as required? Does it answer any questions you may ask at build time? Is it over or under detailed? CAD plans produced with best practice in mind are an accurate and defensible mathematical representation of the final instrument. Musical instruments are themselves based on mathematical models. Keeping that relationship from the initial design through to the shop work ensures accurate and controlled work throughout. Through subsequent articles in this series we'll mention certain useful examples of best practice which will have a direct impact on your design work. Work smart!

When one thinks of a guitar or a bass, it is easy to think that the number of angles on headstocks, non-flat shapes, radii and sticky-out bits plus various pieces on top of each other would favour 3D; modelling the instrument as a virtual item or set of items. A tangible real-world object often seems more appropriate as one possessing three dimensions. How is it that 2D is still the most appropriate design methodology for the vast majority of instrument design? In many respects, 3D is genuinely useful and definitely relevant for instrument manufacture. As soon as CNC milling becomes part of the equation (or 3D printing of course!) mere flat 2D is no longer sufficient. Whilst basic shape and contour milling ("2.5D" or "3-axis" as opposed to true 3D) have much in common with 2D, what we are in essence doing is directly modelling a real-world item as opposed to drawing a representation of it. The general objective for the 2D approach is to provide drawings which abstractly communicate the metrics, characteristics and specifics of the final product. Whilst a 3D representation has direct relation to the end product, 2D can be far more arbitrary in how it represents details, attributes and the processes required to reach that same thing. To reinforce this comparison, here are two images. One is a 3D representation of a '62 Stratocaster body from a publicly-available Solidworks model, the other is an excerpt from an original Fender blueprint of the same '62 Stratocaster. It should be abundantly apparent that on its own, a 3D model communicates little whilst a detailed blueprint is a goldmine of abstracted specifications and measurements; a virtual instruction manual. The comparison of extremes is perhaps a little unfair in that Solidworks models can have 2D drawings produced from a modelled item. Generally it is not necessary to go up to the level of 3D modelling only to bring it back down to 2D abstractions. Most hand-built guitar and bass designs can have their measurements, layout and specifications represented adequately in 2D and have that translate more or less directly to the final physical woodworking. Operations such as cutting the outline of a body, routing a pickup hole/control cavity, locating the bridge or even planning a neck take place in two dimensions. Whilst 3D definitely offers many powerful modelling and simulation capabilities, in the context of guitar building it is more of an addition than a replacement to "traditional" 2D.

CAD ("Computer Aided Design") in its most basic form is the electronic equivalent of traditional pen-and-paper technical drawing. CAD stores drawn shapes (such as primitive lines, points, curves) as precise mathematical representations or "vectors". Whilst this might seem an overly-simplistic description for anybody familiar with CAD, this description is as true now as it was in the late fifties when the idea was first germinated. That a technical drawing or "mathematical representation of real world metrics" could be electronically stored, transmitted, reproduced, manipulated, merged, transformed and have calculations carried out on it with absolute mathematical precision was a profound innovation. It soon revolutionised industries such as automotive, aerospace, architecture, civil engineering, cartography, military, travel, even graphic design and desktop publishing plus countless other disciplines. Consequently, this precision lent itself perfectly to engineered instrument designs, CNC manufacture, virtual product simulation/testing and even - as a distant cousin - the PLEK system. The tools for CAD work have become accessible to the point of ubiquity with many free CAD packages broadly compatible with high value industry standard software. Autodesk (makers of AutoCAD) even provide an online version of their software ("AutoCAD 360") offering basic sketching, modification and collaboration tools. It is no longer true to say that CAD requires the same financial, educational or time investments or that it is hindered by clunky user interfaces, is unreliable and buggy, or worst of all opaque, unhelpful with a steep learning curve. Whilst some software might seem to hang onto these negative '80s aspects of CAD, the general landscape is now completely the opposite; CAD is completely accessible and easy to pick up. tl;dr version CAD was a revolutionary design invention, initially for specialised industries but now a freely-available tool. For the purposes of planning and drawing a personal instrument, the most basic geometry tools available in virtually all CAD packages are more than sufficient. Even if you want to go down the completist route, this too is not too far removed from the most basic tools. For example, you might want to draw out every last screwhole, inlay, radius, fret, cutaway and cross-section to reliably communicate a final design to a third party. We won't be going into this level of detail, purely because our hypothetical CAD journey is to demonstrate taking a practical design from the computer through to the wood, only highlighting details where they are genuinely useful for this end purpose. Vectors Without going into the deep (and unnecessary) history of Euclidean geometry or mathematics, vector geometry is simply the representation of positions and shapes on a 2D plane. Not entirely unlike dot-to-dot on a sheet of graph paper. Unlike graph paper however, CAD coordinates/vectors are almost infinitely resolvable; numbers can be stored to staggering levels of precision. It is possible to zoom into a drawing pretty much to the limits of yours software's ability (more often, willingness) to do so without "losing resolution" as you would with a pixel-based drawing. In real terms for woodworkers, this might seem like splitting hairs. We couldn't care less about losing 0,01mm here or 1/2048" there. Those are impossible to reliably achieve in the wood anyway; these individual measurement tolerances are genuinely not that useful in the workshop. That said, the ability at the design stage to maintain precision, prevent compound tolerance errors and to ensure that the drawings and layouts we do transfer to timber are free of significant error margins, tolerances and inaccuracies is paramount. It is perfectly reasonable to take measurements in the order of 0,25mm or 1/64" to the workshop, however being this coarse at the design stage could leave you a few mm or a large fraction of an inch out later on in the game! To create an awfully mixed metaphor, "looking after the pennies at the design stage means that the pounds will look after themselves in the workshop" (groan) Putting this together, CAD software handles all of the vector mathematics for you at huge precisions without you having to worry about having to work with big numbers or nasty maths. It's happy to locate all of your fret slots to more decimal places than you could ever use behind the scenes but leave you with two or three in your working measurements - if that's what you want in the workshop. Model Space/Paper Space As touched on earlier, a basic 2D CAD drawing comprises a representation of a flat XY space and a corresponding measurement system (most commonly Imperial and Metric). This environment is often referred to as the "model space" where all of your individual drawing objects are created, manipulated and navigated around in a virtual space using a real-world scaling. A model space is normally able to be divided into separable layers grouping and arranging parts of the drawing, not entirely unlike having drawings separated amongst overlaid acetate transparencies for an overhead projector. A "paper space" is subtly different in that it contains a subsection (sometimes more than one) of your model space; a "window" or defined view into your drawing. A direct example of this may be a focus on a specific part of your model space such as the headstock. The term "paper view" originates from its major use; a printable section of the model space. A single model space can have many paper spaces, with each paper space showing different sections or selected layers from the model space plus annotations relevant to that sheet such as scaling, tolerances, filename, revision dates, etc. The model space is where fundamental design work is done whereas the paper space is how parts of the model space are brought out into the real world as useful drawings. The following images show an example of a finished drawing's model space with an example paper space showing a subsection of the model space and a specific selection of its layers, ready for printing. Drawing Entities A drawing in the model space is populated with a number of mathematically-positioned and dimensioned primitive shapes such as points, lines, polylines, rectangles, arcs, etc. In additional to individual primitives, there are compound, complex or specific entities. A hexagon for example, is a compound of six lines in a specific geometric arrangement. A closed semicircle is a compound of a arc plus a line; in fact, a circle is usually no more than a complete arc. More specialised entities like Bezier curves and splines, etc. provide a comprehensive set of objects from which any object can be formed. Individual CAD packages provide many different drawing tools to simplify the creation of complex shapes. Underneath this, the same primitives are at work. TurboCAD for example, can draw a rectangle with rounded corners of a specific radius. Definitely useful for drawing a soapbar pickup cavity! Underneath this convenient veneer is a set of four lines and attached 90° arcs. The following photo shows a selection of primitives and (slightly) more complex objects: Hopefully it now seems clearer that creating a complex instrument design requires little more than knowledge of a few basic shapes and tools. Coupled with a bit of basic geometry and maths (which you can make the software carry out...phew) plus an organised approach, CAD becomes an powerful, efficient and still a creative tool for designing your next instrument.

Many schools of thought exist on the design process for making a solidbody instrument. At one end of the spectrum there's the mad genius school of working directly in the wood by feel and intuition, and at the other there's the CNC gurus who design the entire instrument as a virtual model and have totally different concerns to the general enthusiast luthier. Traditionally, instruments were designed on paper (usually) in 1:1 scale by hand. CAD is not too far removed from this, and adds many layers of powerful use on top of traditional drafting. Through this series I'll be describing my personal design process which I've established over many years and has seen me through the development of many different projects, guitar and otherwise. Rather than teaching "my method as gospel" which it is certainly not, the objective is to break the process down in such a way as to help you develop your own personal design solutions and methods. My specific mindset is to maintain 100% consideration for the final working methods and requirements so that the final CAD plan simplifies and preferably guides the work. Anything less than that is merely a "to-scale picture" rather than your definitive go-to reference. Breaking the series down, we'll be covering subjects such as (in no particular order): CAD fundamentals and basic geometry2D vs. "3D"Best practice from beginning to the endSqueezing the most useful information out of your planTracing an instrument from photos, measuring real instruments and creating a derivative working designSingle-scale instrument design vs. compound scale designUsing your plan to produce templates, guides, reference measurements and "taking it to the wood"Quite an ambitious set of objectives from which we hope readers will all be able to take something to bolster their existing skill sets.... For my own part, I have been using IMSI TurboCAD for around a decade and I'll be demonstrating most concepts via this CAD software. The underlying operation are universal across the vast majority of 2D CAD packages. Whatever you have access to, the ideas will translate across easily. If you're learning CAD for the first time or just don't have immediate access to the software right now then IMSI have a free 30 day downloadable trials of TurboCAD. 30 days is more than enough time to familiarise yourself with the design processes described here. Do try out other packages and figure out whether dropping $40 on the cheapest version of (TurboCAD Designer) would be a good investment for your own work. ProjectGuitar.com has no affiliation or financial interest in IMSI of course! Please leave feedback comments on the articles and I'll attempt to address questions and improve the quality of information on the fly. Most importantly, enjoy! I hope that this series gives both the beginner and the experienced something to take back with them.