The Grasshopper Generative Guitar

[GenerativeGuitars]

Hello guys,

Im using Rhino3D and RhinoCAM to build guitars with my CNC. I just started doing guitars and I know RhinoCAM (RC) since about 4 years.

I have a 1000Z CNC-Step cnc which is quite nice, 1000x600x110mms of cutting area. I've had it for 5-6 years and delivers amazing quality.

The big difference with other CAD artists out there is that I use almost exclusively a Rhino3D module/plugin called Grasshopper (GH) to do all the design. Almost no drawing tools used within the Rhino3D interface. 

The basic body shape is an outline imported from a CAD file and the rest is drawn using GH using the draft's size and distance measures.

Everything that can be CNC'ed was modeled and I added the option to change the following parts too:
- Body shape
- Scale of fret board
- Inlays for fret board
- Neck head shape
- additional pickups (std pickets, but im modeling humbuckers and different bridges later)

Also the neck profile can be changed, the fret board dome radius, pickguard,

It's all based on a telecaster - so the lespaul looks (or scale) can be used also. Continued in next post...

 

[GenerativeGuitars]

So here we have a Lespaul neck on a fantasy shape body...

I know it's not a want to have body kind of guitar, but it's the approach which I think some of you might find interesting.

The process is first to model the guitar as correctly as possible. Test it in the CAM program for possible issues, see what tools can be used, times needed per stock and part.

The Lespaul body is more complex so I'm still modeling this in my head for when I want to do it. That being said, i saw another way of doing cavities in guitars and need some more experience doing Telecaster bodies before.

The picture of the program is next.

 

 

[GenerativeGuitars]

So this is a top view of the whole program in Grasshopper...

The program started in March 2023 after getting the draft plans for a Telecaster (dont ask me which, it's not written.)



I will post more about the CAM program later.

[GenerativeGuitars]

The CAM work is made quite easily in RhinoCAM since you can select directly the parts want to carve. These parts are created into Rhino3D objects directly from GH.

Whereas before i would create a shape in GH and then position it in Rhino viewport to CNC, now i automated this process - including for the flip sides CNC. I dont have a big or expensive CNC so i do with what i can but the setup process is as easy as can be. Any size of block or part. Quite proud of this idea.

Once the strategy per part is defined it takes practice to find quickly the job you need with near - no sanding needed surfaces.  

In case there are new iterations of a part, it's easy to redefine each job. But it can be tedious. I haven't done this yet out of prototype designs so reality will surely slap me hard in the face sooner or later.

[henrim]

There’s something fascinating about this. I can’t think how it would be of any use for me, but I guess there are people who would be thrilled to be able to put together their own partscaster this way.

One thing you need to figure out is the neck angle. With carved tops (e.g. Les Paul) and different bridge designs there may be need to set the neck to a different angle. Also it can be a personal preference to have an angled neck. It affects playing just like different neck profiles, string spacing, string height and fretboard radius etc.

[GenerativeGuitars]

6 hours ago, henrim said:

There’s something fascinating about this. I can’t think how it would be of any use for me, but I guess there are people who would be thrilled to be able to put together their own partscaster this way.

One thing you need to figure out is the neck angle. With carved tops (e.g. Les Paul) and different bridge designs there may be need to set the neck to a different angle. Also it can be a personal preference to have an angled neck. It affects playing just like different neck profiles, string spacing, string height and fretboard radius etc.

Thanks. You're right but the angle is not a hard to do design. I also need to model the truss rod channel too - something that I'm leaving for last as I saw a curve in the plan/draft - which im not sure why it is or how it changes the gutter size and depth.

[henrim]

8 minutes ago, GenerativeGuitars said:

I also need to model the truss rod channel too - something that I'm leaving for last as I saw a curve in the plan/draft - which im not sure why it is or how it changes the gutter size and depth.

There are two main types of truss rods. Single action and double action. The former is (typically) seated in a curved channel and the latter in a straight channel.

There are other types as well like the Fender bi-flex, which is a single rod in a curved channel but acts like a double action rod. It needs an additional anchor in the middle.

[GenerativeGuitars]

Yesterday I received the Fender Telecaster tuners and it's not the same setup from the diy guitars. I had only modeled the main hole, not the screws I had and these tuners have 2 pegs instead which will need to be machined at some point.

So today in about 30 minutes, I created a cluster (like a prepackaged object in GH) for a Fender Telecaster tuner and voila. It auto positions to the head of the guitar. I left rotations and possible orientations outside the cluster so it it easier later to orient for the Lespaul time heads. Anything is possible with this arrangement.

Im not interested into doing minute details for the rest of the tuner because it doesn't make sense at the moment.


[henrim]

I’m not really familiar with Fender but I think they typically use tuners with pins instead of screws. Anyway I don’t think you need to cnc anything for the pins. They will be pressed in to the wood when the tuner is tightened in place. For the screw mounted ones a pilot hole would be nice.

What you have here is 6L tuners. 6 in line on the left hand side of the headstock. Les Paul has 3L+3R tuners. The R tuners are physically different. Like a mirror image of the left side tuners. Then some guitars use 6R, six in line on the right side of the headstock. And any number of other combinations. But 6L and 3L+3R are the most common combinations. Then there are of course lefty guitars which I think use the opposite ones than the righty’s do. But don’t quote me on that, I have zero experience with lefties.

[Bizman62]

10 minutes ago, henrim said:

I’m not really familiar with Fender but I think they typically use tuners with pins instead of screws. Anyway I don’t think you need to cnc anything for the pins. They will be pressed in to the wood when the tuner is tightened in place.

Predrilled holes are more or less a must. The pins are about 2 mm thick with rounded tips, and about 3 mm long. Pretty much impossible to just push into maple even with a wrench making the bushing pull from the other side. And the Fender AmStd neck of mine has drilled holes instead of crushed.

[henrim]

7 minutes ago, Bizman62 said:

Predrilled holes are more or less a must. The pins are about 2 mm thick with rounded tips, and about 3 mm long. Pretty much impossible to just push into maple even with a wrench making the bushing pull from the other side. And the Fender AmStd neck of mine has drilled holes instead of crushed.

In that case they of course need drilled holes. The ones I have seen on some other tuners have just small nibs. Expect the Steiberger tuners that have a pin that def needs a pilot hole.

[GenerativeGuitars]

57 minutes ago, henrim said:

Like a mirror image of the left side tuners. Then some guitars use 6R, six in line on the right side of the headstock. And any number of other combinations. But 6L and 3L+3R are the most common combinations. Then there are of course lefty guitars which I think use the opposite ones than the righty’s do. But don’t quote me on that, I have zero experience with lefties.

That's a nice detail to learn. Thanks!

[GenerativeGuitars]

Pre-drilled holes are a serious advantage. Everything fits and lines up - and a cnc can do this in record time compared to the ruler way...

Recent project i had was to align holes (FCS surf fin insert holes) to a board and the fit was perfect. Not a drill hole - far more complex because of .03 mm offset (position or size) would not work!

Edited November 16, 2023 by GenerativeGuitars

[GenerativeGuitars]

, Missing still its the pickup hole.

The plans for this part were limit useless. But we'll see when we start doing prototypes.

 

 

 

Edited November 21, 2023 by GenerativeGuitars

[GenerativeGuitars]

Since I designed this guitar based on a basic Telecaster draft plan with engineering sizes and positions (not always obvious), I had no idea, back in March, how the pickup was in the right place or not. I have the fret scale (telecaster and Lespaul) encoded but still didn't know how it really worked out for the placement of the pickups - or how it was important in relation to the bridge.

Now I learned the phytagoras part of the design logic of frets (https://tex.stackexchange.com/questions/500427/drawing-an-accurate-guitar-fretboard-with-tikz) , I might have to recode the whole guitar assembly. Or maybe just nudge some references point - this is my big problem. How to re-write this right. Parts don't have to be recoded but the whole model might need to be rewired. Talk about spaghetti code!!!

The pickups are based on a point in the beginning of the program (middle end towards the head/neck, top of the guitar body) that sets the origin of the other parts. I thought the Nut to be the 'center' of the universe (because fret is measured down from it). Or is the Bridge the starting point from where I need to measure distance to the nut? What is the best logic here? Imagine the neck/body sizes change... I can find the right frequency for frets, but what about the pickups? Any logic there?

 

[Bizman62]

3 hours ago, GenerativeGuitars said:

The pickups are based on a point in the beginning of the program (middle end towards the head/neck, top of the guitar body) that sets the origin of the other parts. I thought the Nut to be the 'center' of the universe (because fret is measured down from it). Or is the Bridge the starting point from where I need to measure distance to the nut? What is the best logic here? Imagine the neck/body sizes change... I can find the right frequency for frets, but what about the pickups? Any logic there?

Can't tell about the logic but the Pythagoras thing is interesting. That makes explaining some theories so much easier!

If you take that Pythagoras thing and mirror the neck side to the body side at the 12th fret you'll notice that the harmonics rules apply there as well. You can pluck a 4th harmonic both on the 5th fret or 1/4 of the scale length from the bridge. Funny enough that happens to be right over the neck pickup of a 21 fret guitar! Same with the bridge pickup, the Tele pickup sits at about 1/16 which also produces a high pitched harmonic. Placing the pickups to certain nodes is an arguable thing, though. Just think about 24 fret guitars, the pickup has to be placed to the closest location of the neck but it's far from the 1/4 node and nobody cares. That said, our very own @Crusader has tested various locations regarding pickups and nodes and he has managed to both make his guitars ring and move some less favourable tones outside of the scale.

 

Speaking about the center of the universe, let's start from the nut. The bridge is adjustable and although you can do similar compensation to the nut it's of less importance. The frets on the headstock side are so wide that placing your finger makes more difference than the nut. On the narrow frets there's less play so compensating at the bridge makes more sense. Not to mention that the impurity is part of what makes a guitar sound so nice in our ears! Otherwise we'd all be using True Temperament Frets with calibrated string sets. And maybe robot players with uniform fingertips and preset picking force and angle.

[GenerativeGuitars]

Thanks Bizman62!

Someone sent me a link about temperament which made a lot of sense against using Pythagoras precision. I plan to stick to the original fret scale 25.5 which I had already encoded from the plan I am using at the moment,

 

 

 

[GenerativeGuitars]

Stuff to know...
 

 

[Bizman62]

Good watching, a well spent 6 minutes there!

I know an elderly mandolin/accordeon player who also fixes the latter. According to him the old accordeons (pre 1940's or so) were tuned according to A 432 instead of A 440 which made them play perfectly with mandolins tuned to A 440. With both tuned to 440 the accordeon sounds sharp. Also tuning the old accordeons to 440 pitch ruins their tone. Guess that has something to do with how the sound is produced.

More about the subject here: https://emastered.com/blog/432-hz-tuning-standard

And further: A common trick to "make your guitar sound better" is to tune one semitone lower, to Eb instead of E. The 432 tuning falls roughly in the middle between concert pitch and the dropped semitone.

And of course changing the tuning requires re-intonating... But so does changing the strings to another gauge or even within the same gauge to another brand with a different type of metal used. So many variables, yet we're trying to mass produce identical instruments!

[GenerativeGuitars]

I could introduce you to a violin player/maker...

 

[MiKro]

@GenerativeGuitars, I love it, I too have been using Rhino since version 5, Now have 7, I love Grasshopper. Would love to see your GH file on that.

MK

[henrim]

39 minutes ago, MiKro said:

@GenerativeGuitars, I love it, I too have been using Rhino since version 5, Now have 7, I love Grasshopper. Would love to see your GH file on that.

MK

I guess I should try Rhino again. I tried the beta versions prior to 1.0 back in -97. Nurbs was a kinda new thing then. I had  learned polygon modeling and didn’t quite like the workflow. I have of course used nurbs after that but never really got back to Rhino. I guess it is a bit different in today’s releases

[GenerativeGuitars]

1 hour ago, MiKro said:

@GenerativeGuitars, I love it, I too have been using Rhino since version 5, Now have 7, I love Grasshopper. Would love to see your GH file on that.

MK

I added jumpers to each section last week.
On top, the red lines are the parts ready to be assigned in RhinoCAM.

[GenerativeGuitars]

42 minutes ago, henrim said:

I guess I should try Rhino again. I tried the beta versions prior to 1.0 back in -97. Nurbs was a kinda new thing then. I had  learned polygon modeling and didn’t quite like the workflow. I have of course used nurbs after that but never really got back to Rhino. I guess it is a bit different in today’s releases

I understand that different people prefer the Freehand (macdraw) vs the Illustrator/AutoCAD modes of drawing. I get creative right away with the prior and struggle to do anything with the later. But Rhino is natural UX adoption for me, it's old mac style and it's so intuitive (cough cough)... I learned about Rhino3D at version 6 and it was adopted in one week. I also liked SolidWorks way of working but can't afford the license. I really like the look of Fusion360 but it reminds me of AutoCAD's way of working (Illustrator like). I tried FreeCAD and got nothing done in 2 weeks! Tried Rhino and day 1 I'm creative again and producing stls for the 3D printer or CAM tests of the day.

I used to teach and consult printer shops, publishers Freehand and Illustrator 30 years ago... I did a bit of industrial engineering and architecture drafting also.

For the Grasshopper modeling I didn't have to use SubD but I'm looking forward to integrating it later for the neck.

The only non-grasshopper items in this program are the body shape, and the head shape which are flat (2D) Rhino curves. I found how to model the body's curves but the neck is - yeah not needed yet. The reason I love GH is that now I can reposition anything, carve any body and any neck profile such that they fit perfectly body-neck which is, I hear, paramount to guitar building...

Edited November 25, 2023 by GenerativeGuitars

[MiKro]

@GenerativeGuitars, I agree I like Solidworks even better, but the cost, like you said is an issue. F360 is not intuitive to me, the CAM in it has some good ops though that Rhino CAM does not. 

SubD has been a game changer to some extent

I have been working on a GH for necks but left that in the design stage and quit messing with it last year. UGH!!!

I use a Prusa Slicer right now with my FDM and only step files. STLS are old tech and not as clean in my opinion.

 

MK