Mike.Mara

Haha, yeah that's plenty long! Looks like it's going to be pretty stable! It's always good to have something designed in just-in-case, even if you never need to use it, you know it's there.

How many hours did you pour into doing that?

Looking very nice indeed! How's that central screw working out for you? No racking? What are those plates under the gantry attached to your Y plates? Can't quite see what they are, I'm assuming extra rigidity?

I thought the exact same thing so I went with 20mm rails. It also probably would have been a pain to get them centred correctly without all sorts of calibration tools. Since you've done it, am I correct in that thinking? Well... With the 20mm rails, I've managed to scour the internet and find parts you can get anywhere, so we're good there. And the best part, nothing has to be perfectly square as long as you work from one reference edge. So it doesn't matter if you don't have the tools, and all you'll need is a drill and some type of saw. (So far, on just the X axis). I'm heading over to your re-build thread now! Looking forward to seeing it.

OK... In the interest of covering all bases: How do you guys feel about MGN15 rail from China? Because (I know China can be hit or miss for quality) For 2 sets of 700mm rail, 4 carriages a 1605 ballscrew and all associated parts including mount, you're looking at £122 all in ($160.90). Excluding import taxes. Combine that with some cast aluminium for the back plate (or MDF), 2 pieces of small extrusion and a motor mount (pre-fabricated) and you're pretty much there for the X axis. No fabrication so-to-speak apart from drilling a few holes. And with the method outlined by Mikro, that's not going to be an issue. Well within the range of anyone with a drill. Thoughts?

Well, Timber and aluminium anyway. That's why I originally went with extrusion as much as possible. It's a difficult thing trying to design a machine on as tight a budget as feasible so that most people could afford to build one. And thinking about the kind of tools people are likely to have access to. I personally have a CNC capable of wooden parts and a CNC mill capable of aluminium parts and given Mikro's suggested $2500+ budget, I'd have no issue putting together a damn good CNC router. But most people won't have access to that machinery or that budget. I know I don't have that budget lol. You could easily put together a machine out of that Openbuilds stuff without needing to make anything, but it's lacking in the rigidity department, although it could be helped with strategically placed steel angle. I dunno, I was just kicking the idea around... If you think it's worth pursuing, I'll soldier on!

Indeed, not that it can't be done of course... Just the right tools or right suppliers are needed. I think there wouldn't be any issues mounting the rails on their side for this application, but if one person has concerns I feel others will too. That alone would probably make it a non-starter.

I meant on the Y axis, as we then need to create a 90 degree joint to the Y axis plates. I feel like we're running the risk of taking this beyond the realm of your average person. What with needing to get multiple parts perfectly square in order to have the machine cutting perfectly. The original idea was to have as few parts to make as possible, reducing the likelihood of something being out-of-square. You've both made extremely valid points, so without either upping the original guide budget to go for hardware that's less awkward about which orientation it's mounted in it's not looking too good. HIWIN rails would be ideal, but are more expensive than the supported round type. Round type being ~£282 and HIWIN being £604.90. A decent pillar drill without a ton of runout isn't something I would think most people have so making lots of precision parts by hand may be out of most people's reach without first investing in more tools. Thoughts?

This is all good! Centre punch is an invaluable tool, I used one to mark out the Y axis plates on my CNC. Having drilled without one too, it's a must have! @MiKro Label printing paper is an awesome way of doing that! I've been using spray adhesive (which I hate both the smell and overspray) and it's a pain to remove even if done quickly. That trick will serve me well. @curtisa I'd heard that too about the bearings, especially when used on a Z axis. On further investigation, it actually takes pretty extreme forces to cause any issues. That being said though, as it's a valid concern for the longevity of the machine and one of the more expensive parts, I agree it would be wise to adjust the plan to take that into account. Do you have any thoughts on ways to attatch them to the gantry sides in that orientation?

Sure thing, didn't know if I was going overboard with sizes again. Do you think 1050 x 550 x (some useful number) would work? Means no through neck basses (Or at least none I have designed). Because if it would, there is this kit from the same seller. Obviously if we could do it all from bolt on to through neck, short scale to long scale it would be better, but for some people I imagine sourcing parts is a bit too much effort. I'll try to work out something as drill-by-numbers as possible. Preferably one design with parts interchangeable so if you want ballscrews, then use them, trapezoidal, use them, MDF/Extrusion, all the same plan. It just so happens that a 20mm ballscrew mount will take a 16mm trapezoidal nut perfectly, so it's all up to the builders budget.

Indeed, I have looked at those kind of kits before. The only issue I have with them is that dimensions are pretty... Well, they don't exist lol. (And I've heard a few people have been sent bent rails.) Don't you think 12mm rails and screws are a bit skinny? I may be over-engineering in my head again. (I have a habit of doing that). It is an attractive price for rails and ballscrews though... That's for sure.

And just for the sake of pleasing many budgets and workshops: What do you guys think? Both the same dimensions and can be upgraded from MDF/Ply to aluminium without modifying the rest of the machine. The difference is clear at ~£136 for the extrusion with MDF bed (not including brackets, t-nuts so more like £180.) Or ~£17 for MDF (Not including screws.) I'm sure you could get the MDF cut at most home stores too if they have one of those big vertical panel saws. @MiKro I'm guessing for most people the saving on the MDF there would negate the price of the housed bearings so good point, they can come into play to save having to mill pockets. So ignore my last post, I jumped the gun on that one lol. Edit: Or replace the MDF supports with 20x80 aluminium extrusion for a mid-range budget. Making that about an £86 option (Minus T-nuts again.)

The problem with that would be that housed bearings that match leadscrew diameters are expensive. Or the couplers from motor to leadscrew are difficult to find. The only leadscrew diameters that match standard housed bearing sizes are 12mm and 20mm. That's not to say the others can't be found, I have a bunch of 16mm ones, but they cost about twice the price. By the time you've bought 6 for the X and Y you're looking at £60 for 12 or 20mm and £120 for 16mm. Or about £20-30 if using standard bearings or angular contact. I'm not sure what prices are in the rest of the world, but here it starts to add up.

All valid points indeed. If AL plates though, how would the average person go about milling a bearing pocket? @MiKro I was actually thinking the exact same thing about the extrusion uprights just before going to sleep lol. I was thinking about the forces of the whole machine and during difficult or too aggressive X axis cuts, the MDF would be sure to flex. Well... With the extrusion being square, Misumi Europe do an incredible job, mm perfect and square as you'd want. However you need a business to shop there. @curtisa But wouldn't we have the same problem if it was mostly MDF too, can the average person with a modest workshop ensure square cuts with modest tools? I personally would consider my workshop modest, and I have no table saw. I can get pretty damn close with a jigsaw, square and router with a straight guide. But that's obviously not ideal as a mm out over ~1400mm would mess with the alignment and accuracy of the machine as a whole. Unless of course you have any woodworking trickery you'd like to let the rest of us in on . Right, so as Curtisa suggested... What are the boundaries? What can the average person work with a good degree of accuracy?

Well, I had a little play and came up with something like this: Not complete obviously. The brown parts being MDF. The cost for framing, aluminium, rails, leadscrews + nuts and couplers is right around £580. I'm going to take a wild guess and say the rest is about £200 for the T-nuts, bolts, bearings, shaft collars ect. (Not ballscrew bearings). So should be just shy of £800 for all the mechanical parts. Electronics + spindle + USB driver (incase people want to use laptops) ~£430. So in total about £1,250. Work area is ~X 500 x Y 1100 x Z 150. (Z could be raised or lowered by adjusting the length of the Y plates.) Machine footprint 1400x720x430 minus electronics. Like I said, just rough... Just testing an idea to see if you guys see anything I don't or if you have a better idea. (20mm rails on X and Y, 16mm on Z. Extrusion is 40X80mm, MDF can be either 18mm or 3/4" without any modification.)

All good tools to have for this! I think a mix of MDF for the more complicated parts and aluminium for the parts that are less so should work a treat. (Like the back plate on the X if it were aluminium it would only need a series of loose tolerance holes for the extrusions to bolt to. A mm here or there makes no difference.) I was hoping to use a fair bit of aluminium profile for the base, so it's just bolt together and the rails bolt right on too. I agree it should be kept as doable in a home workshop as possible, the more off-the-shelf parts and bits people can make themselves the better. I'll take a look at the JGro

Very good points! I've been spoiled by Misumi and their cutting service, they've always had square ends. Misumi Europe anyways. The end plate tolerance I think can be done reasonably if you order a laser cut template. (For those guys without a CNC). I totally agree about the electronics, that's something I've not considered a problem since at this point it's almost second nature to me. A ready to go system I'm guessing is going to be a budget blower for a lot of people. With a digital caliper and a marking gauge I think most people with a pillar drill should be able to get pretty accurate holes for mounting everything, or am I way off base here? Cutting may be a different story... I know here in the UK most suppliers that I use deliver parts ready to use. That may be a different story everywhere else though. I guess this is why I started this thread lol... So people like yourself can poke holes in the idea so we can try to make it as straight forward as possible. I mean there is always the option for those who can't do it themselves to outsource to a water jet cutter or someone with a mill, although that will add some to the cost. I guess as long as we try to keep the parts as small as possible that would reduce the cost somewhat. Mach3 I've found is a bit of a learning curve but once you've got the hang of it its super simple... Yes it does cost, but I think as long as we lay out all the costs up-front then there won't be any nasty surprises for anyone. I know there were for me what with CAD and CAM, not to mention Mach3.

Something like this for the X axis for example, should be more than rigid enough to do aluminium, and costs under £200. The drawing doesn't show the trapezoidal screw, bearings, lead nut or housing for the nuts, but the major costed parts are included, including a back plate of 10mm aluminium. The max travel for that would be 400mm, but the price increase to get to 500mm is minimal, and if using the smaller bearings could be made to travel 450mm. Those linear bearings are oversized for that gantry, they're just what I had on hand to put in there. I would imagine after the coupler for the motor and bolts ect. that it would come to around £250. Thoughts on that style? Any pitfalls you can see?

Don't get me wrong, I agree with both your points... For a machine with a great deal of accuracy, speed and rigidity that original number of $2500 minus software seems a reasonable number, hell, for just HIWIN 20mm rails and 20mm ballscrews here for a machine of the rough dimensions to make a guitar, you're looking at almost £900. That's no bearings or couplings either. Just to make the goal clear, I'm not expecting to be able to split a hair or take more than a couple mm's off the stock each time. I indeed agree with the concerns of the MDF and cutting fluid, or any moisture in general, so we'll need to come up with a solution. What do you guys think of sealing with shellac and finishing off with a lacquer to protect it? I know you can route aluminium by hand, but I'm sure I'm not alone when I say that scares the crap out of me. I had the misfortune of planning my first CNC as a scratch build and deciding half way through that instead of supported rails and trapezoidal screws that I was going to buy a "kit". So I sold all the rails and the ballscrew I had for the Z axis and bought one of those Openbuilds OX monstrosities. (Not that they're terrible in their own right, but I had the misfortune of the only person in the UK at the time selling the kits deciding he was an engineer and re-designing it, terribly, he clearly has no idea of even the basic forces involved and the "rails" were cut terribly, the whole thing was as floppy and about as rigid as damp cardboard.) I think with some careful engineering, aluminium profiles, strategically placed angle iron and the supported rails the rolling frame should be rigid enough to deal with light aluminium cutting and hardwoods at a reasonable feed rate. It should go without saying (definitely will to you guys) that it's not going to be a professional machine, more of an entry level machine with capability beyond it's price range. I have no doubt that for less than my machine cost, one could be built that would kick its ass in both rigidity and cut quality. My original plan for my CNC, the one I was building, was an MDF frame (which I still have most parts of) and when assembled, it was a damn sight more rigid than the one I have now. @curtisa Hell of a challenge indeed! I know it can be done, there will be compromise and limitations but as long as we're realistic like you said... I don't see why it shouldn't be tried. I've seen some badly designed machines made of MDF do decent work and even cutting aluminium. My machine like I said, isn't the best, or rigid enough, or many other things... But it can cut aluminium (albeit extremely slowly) and hardwoods with a reasonable degree of accuracy. Enough that I used it to upgrade itself from completely useless to usable. Price becomes a major factor though, if it can't be done reasonably for £1000 or less (minus electronics, software) then it's not worth it.

Awesome, well at least we have common numbers in most of the important parts. An extra 0.7/1.5mm or so here and there isn't too much hassle.

Also as a side note, can you get metric sizes over there easily? I know it's difficult to get imperial over here... Wouldn't be very good if we can't get all the parts both sides of the pond huh?

Exactly the idea! And well... Lesser of two evils indeed... I would think a rigid enough bed to take repeated Z axis poundings would cost more than the extras for 2 screws on the Y. What are your thoughts on that? I've seen a few MDF machines cut aluminium to an acceptable degree so I think it may be a good starting point, everyone can work it, you don't need a CNC already ect.

I wasn't having a go, sorry if I came across like that! I was just bouncing my thoughts back

On a machine as low budget as possible, I'd think 2 screws on the Y, I don't think it's particularly needed but then you need a stronger frame for the bed which would probably cost more than an extra screw, driver and motor.

Well, personally I think 500mmX1100mm work area is adequate. That would allow Flying V/Explorer types as they're the widest I can think of, and through neck basses. The PC is less of an issue now since you can get a UC100 USB (Which I currently use on a Windows 7 laptop with Mach3). I've not had any issues as long as I keep it only running Mach3 when the CNC is running. I wouldn't say accuracy is un-achievable with a low end machine, mine certainly is low end and with rough calibration with a steel rule I got to within 1.2mm over a 711.2mm scale length and the intonation is perfect. This is also GT2 belt driven, cheap chinese electronics and a router with a decent amount of runout. So I'd say given some careful and thorough design work we could do better than that. I also think that $2500 is a high number, unless you're talking HIWIN rails and ballscrews ect? I was thinking more supported linear rail and trapezoidal screws. Maybe prices are different in the US but over here you could get the rails and the screws for less than £250. My initial thought was that the CNC would be capable of doing what we want it to, and something you can easily upgrade later if your needs change.