by neocalm » Thu Sep 13, 2012 7:59 am
Love the idea of having unified mechanicals but my expertise is more in electronics/software, so it's not going to be me. I'd love to use those inexpensive 5/8" McMaster Carr ball screws everywhere but am guessing the speed might be underwhelming for the Hadron build I'm doing. Except maybe the z-axis.
So far those questions TLHarrell posted are the ones I'm chasing down.
1. Is there a controller which is suitable for running all types of machines?
I cannot see a lower cost alternative to the LinuxCNC/EMC2 host with $199 Mesa 5i25+7i76 PCI Card. It provides 5-axis + Spindle, with hardware PWM up to 12.5 MHz. That assumes a PCI-based PC close at hand (there's also a PCIe solution with similar price) but includes the software cost ($0) and a RTOS kernel to boot.
There is a 6-axis + Spindle version but I haven't found a hobby machine that would require the sixth axis.
There is the minor (cough) matter of using LinuxCNC with something specialized like the 3d printer/rep rap but it looks like there are some basic solutions there. I'm not against writing some software to make it happen.
2. What stepper driver(s) would you use for best interoperability to share between the machines? Is there any problem with using a driver for a NEMA32 motor on a machine with NEMA17's?
It doesn't seem like it can be a truly universal solution because drivers for a NEMA 14 hardly would be a good fit for a NEMA 34. But here's what I found with, e.g. the Keling drives:
KL-4042D - 200 kHz Pulse / DC 18-36V / 0.5-4.2 Amps / NEMA 14/17/23 - $70 ==> x 5 = $350
KL-5056D - 200 kHz Pulse / DC 18-45V / 0.5-5.6 Amps / NEMA 14/17/23 - $90 ==> x 5 = $450
KL-8056D - 200 kHz Pulse / DC 18-70V / 0.5-5.6 Amps / NEMA 14/17/23 - $110 ==> x 5 = $550
KL-8070D - 200 kHz Pulse / DC 18-70V / 0.5-7.0 Amps / NEMA 17/23/34 - $120 ==> x 5 = $600
These by most accounts are absolutely smooth stepper digital DSP drivers that give 'servo-like performance' out of the steppers. That falls in line with the philosophy of the project - use inexpensive motors in each of 3x machines but then put 3x the cost in the drivers/controller.
You can see the cost adds up quick so it's sure to spur me to build CNC #2 and CNC #3 pretty quickly!
Don't get me wrong, servos would be great on the universal mechanical project.
3. How much of an issue is it swapping config files and software stacks to move the controller/driver combo to a different machine?
Ah, now that's my expertise. Even starting out with a bash script would make this simple. Those Keling drivers can even be tuned in software - probably THAT wouldn't be easy to switch out and around, but I'm not sure yet.
4. Would you also include the power supply with the unit which is swapped from machine to machine? Or would a dedicated power supply for each machine be preferable as each have differing power needs? Obviously, a laser power supply differs greatly from one for a small CNC.
Not including the "spindle" (laser power supply included in that) I think the power supply for the host/controller/drivers would be a common high quality set of power supplies. Again, the budget is 3x normal because it will be shared amongst the three machines, so no point cheaping out on the supply - we can afford to keep it isolated and ripple free.
So at $550 minimum (for the smaller drivers, using a spare PC, not including the set of power supplies) in comparison to $176 for the Azteeg X3. So basically if one were to build three machines that could be handled by the same drivers, one would be nearly ahead of the game - but with some pretty fantastic DSP drivers and a 12.5 MHz PWM step generator on the controller side. Sounds less hobby and more craftsman to me!