Official Luthiers Forum!

I've been dithering back and forth on 'should I get a CNC or not' for a long time now; I've decided the answer's 'yes', in no small part because I've found out I quite enjoy fiddling with CAD/vector graphics packages now that I've got a little bit of a feel for it, so the hurdle for bothering to learn the rest of the stuff has been removed. I'm pretty technically minded, so I'm thinking it'll be a fun challenge.

I've more or less settled on getting a 'kit' from this canadian guy on cnczone:

http://www.cnczone.com/forums/showthread.php?t=92565

Size: 30" x 48", with supported rails, on the fence about whether to get a slotted aluminum table, or stick with MDF with vacuum plates mounted (have a pair of HDPE plates with fittings already, and not much use for them at the moment).

I could roll my own machine, but without major scrounging it would likely come in more expensive, and require much more time I don't actually have (or rather, that I'm unwilling) to spare. I figure it'll take long enough to get everything working together as it is, and getting the parts from european suppliers for a quasi identcal machine comes out costing more for the linear motion bits and pieces alone, with exchange rates as they are. I pondered a Heiz (CNC-step.com) machine, which I can get locally, but a roughly equivalent machine would cost about 80% more.

Thing I'm still on the fence about is the spindle; should I use a router like a PC892 (which I'd need to import), simply drop in my PC690, get a Kress 1.2HP device (downside: small collet), a German-made dedicated spindle the CNC can control, or one of the cheaper chinese knock-offs with a VSD. Thoughts? I can spend about 400-600 bucks on a spindle/motor of some sort. The majority of work will be wood, larger projects, but I do want to delve into light-duty milling and cutting inlay/light engraving.

14 x 31 cutting area seems small to me....you might want to verify that this will handle tops, etc.. as well as necks.

Trev

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http://www.PeakeGuitars.com

He's got a variety of sizes he makes, the 30" x 48" has a cutting envelope of at least 24" wide. Wand to be able to make dishes. The Z will have 8" of travel.

Mattia, do you have a link to his website. Looks interesting but the above link is just a forum.... who is he?

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Dave
Milton, ON

Mattia,

If you're going the DIY route be sure to check out this machine. http://www.cnczone.com/forums/showthread.php?t=38220 It's the machine I built and so far I'm very happy.

Buying a set of plans gives you access to his forum. There are build logs for close to 50 completed machines and probably another 100 under construction right now. So, all the major problems have already been sorted and a lot of new performance enhancements have been made. As far a specs go, you can make the table size just about anything you want. The standard plans are for a 48"x48"x4" cutting envelope. Mine is currently 48x30x4, but I'm working on an upgrade to get another 2+ in Z. Repeatability seems to be .005" or better (honestly I've been too busy cutting parts to cut a bunch of test pieces) and I just measured average backlash at a little better than .002" on the X and .0005 on the Y. The X carriage rides on a single aluminum extrusion, so there is some flex there. But you're not going to be able to take really heavy cuts with out any slop on anything less than a pro grade machine anyway. I'm currently running my rapids at 200ipm and doing generic machining at between 100 and 150 ipm. Small bits (inlay and fret slots) are at ~20ipm. One caveat, many of the parts are sourced from mcmaster carr so shipping overseas might be a problem.

Here's a pic of some pyramid bridges. Bob Garish did the one in ebony. The top of the ziricote bridge was sanded smooth (before I remembered I wanted to take a comparison picture), but the wings are straight off the machine.



Good luck with your decision.

Bob

So Bob,

What kind of bit do you use to make those bridges? It looks awesome by the way!

Shane

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Canada

1/4 end mill for roughing followed by 1/4 ball nose with something like a 5% stepover for the finish. Turn your machine software (Mach3 in my case) "Constant Velocity" setting to OFF otherwise the peaks turn into blobs. They came out pretty well. I made two versions, one with a 20" radius across the top (or whatever that area that isn't the wings is called ) and another angled down by 1/16" on the treble side. The finish quality is not as nice as Bob's, but I can't complain.

I do them with a 1/8" straight (2-flute) and a 1/2" ball (2 or 4 flute, doesn't matter as much). I only use solid carbide or carbide insert cutters.

Pyramid bridges are funny things; they can be machined -really- quickly once you get all the problems with the shape under control.

BobK:
Hey, it's pretty hard to complain about what you got: two minutes of sanding beats a bunch of carving and probably a lot more sanding! Ebony dust and I don't get along very well, so I'm glad the machine does all the ebony cutting!

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Did you order this kit? If so have your received it and what do you think of it?

I placed an order with the guy a couple days ago and was wondering what to expect.

Not received the kit yet, no; am waiting for a few invoices to get paid out, as I'm running into some cash flow issues (car died, unfixable, so that needed replacing first). Besides, since it'll be coming to me by sea, I don't expect it'll arrive terribly soon. I'm shooting for March right now.

Right now, other than cash flow, I'm mostly wondering whether to upgrade to a 10" travel Z axis. I can't really think of reasons why 8" of Z wouldn't be enough, but you never know.

Has anyone else dealt with this guy yet?

The machine that he's offering looks like a lot of cnc for the money but I haven't found anyone how has gotten their machine yet. The price is certainly right but I'd really like to hear some customer feedback before I send him any money.

Agreed. He's very good to deal with online, and this is apparently a new branchout for his business. I'm hoping to get a bit of customer feedback as well, but I'll also be ensureing I double-up safety by using a credit card via paypal. Simple prudence.

Mattia,

One thing I noticed about your original descricption and what I saw on the photos in the link. Those rails are not fully supported, at least not the ones I saw. Do you know for sure the model you are considering have supported rods?

Ask me how I know about the need for stiffness! It is not fun to watch your cut quality suffer due to vibration or flex, and unsupported rails will flex and vibrate.

Mike

yeah, the supported rails are an upgrade, he's posted a few pics now. Also having them tapped and pocketed into the end supports and upgrading to 20mm ballscrews throughout and a 1/2" t slot aluminum table. I think there are a few pics in his last post in that thread. He expects initial customer reviews to start showing in the next few weeks as folks get their stuff up and running.

I just spoke with George on the phone last night and got the same info that you just posted. The machines look like they will be very impressive. This morning I emailed him with my specs and requested a PO for the machine. I'll probably wait until I actually see a machine in someones hands before I send any money tho. The only thing that makes me uneasy is the fact that no one has posted about getting theirs yet.

Now I'm in the process of trying to figure out what to use for a spindle. A router would be cheap but SOOOOOO loud! It would very nice to have control over my spindle speed as well.

jaydawg I thing the quitest spindles are the water cooled versions, whether Chinese or Italian. I know the little 3hp Chinese version is quite a bit less expensive but I haven't heard about life span.

My next spindle is going to be an ATC. I am tired of having to sit and wait for the little short programs to finish so I can change the bits!

Mike

I looked at those watercooled spindles on ebay yesterday but most of them run ER11 collets. That only let's you use tooling up to 1/4". That would be a real issue.

I'll have to go back and do some more research on those.

Agreed. On the other hand, he started the thread about a month ago, and from what I understand pretty much everyone was interested in supported rail machines, which started getting built up a couple of weeks ago. He quoted me a lead time of 7 to 10 days plus shipping, pursuant to all the bits and pieces being available.

He's easy to communicate with, responds quickly and completely to emails, the only part I'm still waiting on is, like you, seeing a machine in someone's hands. Well, that, and some cash in my bank account would be nice

I've budgeted about 4,000 euros for the CNC (excluding tooling, including Rhino and MadCAM), so I figure spending about 1500 us (including vat, local purchase) on a 1.6 kw TeknoMotor 24,000 rpm spindle, including VSD, meaning I can control everything from Mach. ER25 collet.

I agree, he's been very nice to deal with. He's responded very quickly to all my emails and and was very helpful during our phone conversation.

If the machine is everything it appears to be it will be far and away the best value machine available.

After following the link I can't tell if this is a working CNC, a frame, part of a CNC machine, or what. He writes this:



If this is not a working CNC, apprx. how much would a person need to invest in order to make it one? Software aside.

I'm not interested in getting one, but it's interesting to see something so potentially less expensive than commercial units. The way he communicates isn't very clear for someone (me) without any prior background.

http://www.homeshopcnc.com/HFspindle2.html
These units run the ER20 collets which will handle 1/2" shanks and even a little larger.
Nelson

It's a 'assemble it yourself' kit, and you choose how much you want; the basic price is for X and Y axes. Add a Z axis for between 250 and 300 dollars (depending on travel required), and he can provide motors (steppers), controllers and a Mach3 license if you want one. And has a few spindle and spindle mount options. Assuming you have a router, 1500 will get you a frame with all components save controllers and steppers, possibly including motors if the frame's not too huge.

Basically, it's a 'pick and choose' system, and what I'm planning on doing is getting, well, everything except Rhino and MadCAM from him, and putting it together here.

I found that same spindle on ebay last night. The ER20 would be a much better setup.

I wounder how practical it is setting up the water cooling system on a relatively small table top machine? Would the added weight on the gantry affect performance?

jaydawg I am not sure if I follow you, but I will tell you what I know about the system and maybe that will help.

The spindle is the only significant weight on the z axis which is of course mounted to the gantry. The water system is tubing that is fed into and out of the spindle via a small pump that feeds from your water storage container. Many have used aquariums and their pumps.

Hope this helps.

Mike

It's the water storage that I was wondering about. The water cooled spindles I've seen on small machines have the storage tanks mounted on the gantry. My concern was that the added weight to the gantry would cause accuracy problems. You know that whole mass, momentum, objects in motions stuff. (not trying to be a wise-ass, I really don't know )