Hacking a CNC machine, but which one ?

Dear all,

I need to build a special machine for my business.
My plan is to replace the spindle head of a compact CNC machine by a set of custom heads, for measuring and assembling high precision parts.

The other option would be to assemble the machine from scratch using linear stages, but this looks more expensive and more time-consuming.

So I need to select a benchtop CNC machine, and any help would be greatly appreciated.
The main specs are :
- working volume: 200x200x10mm
- resolution : 10 microns
- absolute accuracy in the XY plane: 20 microns (I can easily calibrate coordinates, so reproducibility is actually the most important point)
- compatible with open-source software (I will use a custom software)
- budget: $10000

As the Z stroke is small, a CNC router may be ok.
I am also looking at 3D printers, but usually the accuracy is not good enough, and I would prefer something a bit more robust.

Do you think Roland CNC mills could be a good choice ?

Thanks in advance,
Julien

Why not use a pick and place machine? They're high speed and often contain vision systems that you could apply to your measurement needs.

Hi inthebay

This is a good suggestion.
Automatic glue dispensing robots could also be a good choice.
Unfortunately, they usually use a proprietary software and protocol.
But maybe you know one which is more hacking-friendly ?

j

At the end of the day everything is just motors, drivers, and sensors. Its a matter of getting it all wired correctly to a breakout board. for instance, I have a Nordson glue dispensing robot, but its entirely powered by Nema 17 Steppers and a few solenoids. Just reroute the system into your own control.

I know.
But still I need to choose a machine with the best spec/money ratio for me.
Thanks anyway for your advice . It made me look again at the pick and place option

No, none of the Roland CNC mills are that accurate. The MDX 540S comes the closest, but it's more expensive than you say your budget is. No CNC router I know of comes anywhere near holding an absolute accuracy of 20 microns (.00078") over its working area, although the software resolution isn't a problem if fine-pitch screws are used. There are milling machines available that can meet these specifications, but they are bigger, more expensive, and generally use proprietary control software.

Your idea of cobbling together a machine from an XY and a single linear stage might be your best bet; Parker-Daedal is one supplier that makes them large enough for your purposes: Parker Hannifin, Daedal Division, North America - A Complete Family of Motion Control Products If you get a heavy right-angle block like this: Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies you can mount your Z axis assembly to it. Adding stepper motors, drives, and the open-source Linux CNC software shouldn't be too hard.