Official Luthiers Forum!

This body is done totally in 2d. Cheap, fast and pretty easy. I'd say go Excitech or QuickCNC with Vectric software. I can give you a great contact. No commission at my end. Just trying to help a brother out.

I totally forgot to mention that I could engrave a watch face with this machine. I think analysis paralysis can be the biggest hurdle. It was for me.

Just to clarify a bit, I normally use SolidWorks 2012 and VisualMill pro for SW to do my CAD and CAM work but for inlay, Vcarve is fantastic for two big features they have:

1) Inlay feature that compensates for cutter diameter - with Vcarve, there's no reason to manually radius the corners of your pockets and inlay - when you select a vector, Vcarve will automatically round the appropriate inside and outside corners to match the smallest cutter you'll be using. I believe this is possible in VMpro as well but you've got to do it manually for each machining operation.

2) Spiral toolpath - especially when cutting shell with tiny bits (e.g. 1/64" or .015") you've really got to limit jerk on the bit to keep it from breaking. Vcarve has a toolpath that spirals down along the vector to provide very constant engagement forces. I stopped breaking bits when I discovered that toolpath.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

By the by...I like the looks of those turnkey micro mills but still think that an 11k spindle is too slow. Feed rates will be glacial. I've been debating going for a 24k spindle on my machine because the feed rates are too slow for my tastes.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

NEMA 23 is common for small CNCs, as it has enough torque and good speed. "23" refers to the mounting face size, about 2.3 x 2.3 inches. Here's a spec sheet of a dual-shaft 23: http://www.kelinginc.net/KL23H2100-35-4B.pdf
Larger CNCs use NEMA 34 or 42, and very small CNCs can use NEMA 17. A larger frame gives more torque, more weight, larger shaft, slower rpms, and more cost.

Steve, certainly a ~$5k cnc is a different class machine.

Richard, the CarveWright looks like it's optimized for long signs, molding, etc. The belt feed is very clever for that, but has much worse repeatability for fine detail.

Andy, thanks! The spiral toolpath sounds slick.

To choose a machine for the "S" or similar inlays, to me it's a question of risk:
- A low-$ moving-gantry machine like the 3020 may work under some conditions, but has much higher risk of broken bits and chipped inlays. Its key weakness is its long "chain" of flex and slop: bed -> long flexy shafts for gantry -> sloppy bearing arrangement -> flexy gantry -> long flexy shafts on gantry -> etc. This long serial chain amplifies errors at the cutter. So by design, it will have unpredictable slop, racking, and high-amplitude vibration. If a 1/64" bit is carving the ~0.012" tail of the "S" when the machine decides to vibrate or shift its slop...
- A well-executed low-$ moving-table machine like the Microcarve will have much less slop and vibration than the 3020. Bearing slop will be near 0, as they are preloaded and the moving-table layout minimizes amplification errors at the cutter (2 short "chains" are much better than 1 long one). The 3/4" shafts are much stiffer than the 3020's, but since they're supported only on the ends, they'll allow more vibration amplitude than a Taig. (In a higher $ machine like Andy's, a moving-gantry can work very well using fully supported linear rails and bearings.) So this machine will likely work, but has more risk than the Taig. As Andy suggeted, see what Microcarve says about making the "S" reliably.
- A metalworking mill like the Taig will have far more stiffness and much less vibration. There are no long flexy shafts in the load path from bed to workpiece or bed to cutter. Its "chains" of flex and slop are short and direct. The adjustable gibs should allow near 0 bearing slop, and it will be well-behaved since the dovetail ways have high damping friction. This is why it can cut metal! But it's more $ and would be slow for general wood jobs.

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David Malicky

Okay....
How about THIS one, assuming I can trust this zero-feedback Ebayer who demands clear payment before shipping.....

I've been thinking about getting a CNC machine for solidbodies anyway, and this looks like it could do the trick for that AND do small MOP pieces..........

http://www.ebay.com/itm/151101367485?ss ... l2649#shId

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Old growth, shmold growth!

I would stay far away from that one. Looks like the typical POS Chinese machines people complain about on the zone all the time. Cast iron table and steel base yet it has SBR rails....run away.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Good to know.

How about this as the basis: http://www.cncrouterparts.com/pro4824-4 ... p-250.html

Then I build a nice table for it to rest on, and order the rest of the parts piecemeal from the same company over time?

It looks like the movement is controlled by gear driven wheels that run on tracks rather than screw driven movements, unless I'm missing something.

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Old growth, shmold growth!

Actually, it looks like the wheels are metal and run on rails while the movement is controlled by toothed pulleys that run against tooth rail tracks.

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Old growth, shmold growth!

Actually, some of those cast iron cnc's are awesome!. If you google QuickCNC you'll get a company in Jinan who do those 600x900mm machines for about $1200. The guys name is Taney, he has great English and I've been dealing with him for years. If you are budget conscious and new to cnc, why not just buy one ready made with all the control circuits built in? You dont even need to buy a toolpath path program if you run vectric software for your artwork as it does it all for you automatically. Is it because its from China? I understand the desire to buy local, but I wouldn't even be into cnc if that was my only option. I honestly don't understand why you'd go to all the hassle and expense of making a machine? Unless its for education purposes.

CNCrouterparts.com has a very good reputation on CNC zone for support and for their products. As you noticed, it uses what's called rack and pinion drive rather than a lead screw of some sort.

R&P is very good for speed but usually the resolution is lower than compared to a leadscrew machine. I personally don't have any experience with R&P machines but you should talk to someone who does and find out if it will handle the tolerances you need. It's very possible that it will also give you that 50/50 yield sort of thing. It's possible to have very tight R&P machines but they use very expensive helical racks and pinions etc.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Will cut2d cut work for inlaying a radiusd fretboard??

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MK5acoustics.com

Interesting point.
So, then it might follow that the tighter sheet specs on the Chinese machine I linked is due to the screw shaft down the center?
It looks like a nice thick sturdy screw shaft.
In fact the machine looks well designed, although I'm not 100% sure about it's software platform.
I've been talking to the guy and he's not dodgy at all, seems on the up and up. Plus he's from Texas, my home State!
Says he supports his products and provides support, the advantage of buying from the states. He said if I buy directly from China then I could run into problems.

Decisions, decisions.......

Though it seems I've taken the red pill (LOL!) I'm still mulling things over.

SO.................

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Old growth, shmold growth!

The machine requirements are now a lot harder: large enough to do bodies, precise enough for fine inlay. More money is one answer, but it may take a lot more. It might be hard to find a machine that can do both that meets the other usual requirements (good history and support, reasonable cost). The best single machine I can think of is an XZero like Andy's, though as Andy said, it's far from turn-key. I don't have direct experience with the Chinese machines, but it sounds like some people are happy and some have headaches. I'd suggest buying from a vendor who has a history of good products and support; there's much that can go wrong that is hard to fix, especially for someone new to CNC.

Agreed with Andy on the CNCRP machines -- great company, clever machines for their purpose, might be good enough, but not optimized for fine inlay. They preload the pinion into the rack to remove slop, but the preload wears the pinion faster (and then precision is lost). Their linear motion systems give good performance for the cost, but are sensitive to chips and their V-rollers may develop some lateral play over time (not important for wood, but could be a problem for the "S").

Yes, a ballscrew is the most precise drive system for CNC. Next is a good ACME screw. Then a non-ACME screw. Then R&P, belt, chain. (Generally)

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David Malicky

Funny how that happens, right?

I may pull the trigger on a Chinese behemoth.

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Old growth, shmold growth!

Oh, that never happens to me.

For a medium $ turnkey machine, I would spend $2.5k more and get something like a K2CNC: http://k2cnc.com/product_kg2525.aspx
USA construction and support, well-established company
Servos on all axes (more precise, accurate, and smooth than steppers)
Better ballscrews
Profile rails
0.001" repeatability
Mach3
We have a K2 in our shop and use it regularly; it has some limitations and I think it's overpriced, but I'd take it any day over a generic import machine.

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David Malicky

Thanx, but I can see that easily turning into a 10K purchase with options LOL!

I dunno. I think buying a Chinese machine from a US importer who will provide customer support from over here will work out, either at first if he tests it before shipping it to me, or down the road after all the glitches are worked out. I can live with that, I think.

I MAY just buy THIS one, for doing just pearl, and possibly machining bridge hardware:

http://www.ebay.com/itm/321194315336?ss ... 1423.l2649

As you can tell, I'm ALL over the map, and may have to have Birko do some for me in the meantime until I make up my mind, or give up.

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Old growth, shmold growth!