looking for a good 3d printer

[AlexDoran]

Re-reading what I wrote, I should of used accuracy instead of resolution.
You can have as much resolution as you want, but you still can't guarantee accuracy. I'm aware 3D printers will have less stiction than a typical CNC, but the same problem will still be there. Apply a bit load to the screw, or even try twisting it by hand, and unless you have a system with next to zero friction, it won't return to the exact position.
However with a 3D printer, you should get good repeatability, as the load is pretty constant. It's not like a typical CNC machine where you'll have a cutter pushing/pulling things away from where you want them.

The best way to see how much accuracy you do, or don't gain, would be to fit a high resolution encoder to a stepper, and see how even the encoder pulses are compared with the pulse train at slow speed. Once things are moving inertia will help smooth things out, and drivers will typically reduce the output microstepping anyway.

It's a bit like those who say a 10'000 count servo on a directly driven 5mm pitch screw has a resolution of 5 microns. In reality a 10'000 line servo is only likely to hold position within 20 counts with a pretty good tune, so your realistic accuracy is 0.01mm.

It's worth mentioning, that more advanced microstepping drives, will still microstep the output, even if you are using full step input. Without microstepping the output, you get rough movement at low speed.

Sound is down to a mix of the switching frequency of the drive, and the sound of the motors physically moving/cogging. Get something that switches above 20KHz, you're not likely to hear any buzzing/humming, but you'll still get the noise from the motors above a few RPM (6RPM if my calculation is correct assuming a typical 200 step motor and a lower hearing frequency of 20Hz - to get 20 steps a second, you need 20*60 = 1200 steps per minute, divided by 200 steps/rev to give 6RPM)

Now that makes perfect sense to me, thanks for explaining it i have learnt from your post, you obviously have a much higher understanding than me in general about the technology involved. I think the TMC2100 can take a 1/16 input, and re-pulse (is that even a word?) it to 1/256, but in a way that you still get the 1/16 resolution.

I believe the "Silent Mode" the TMC2100's provide is only really suitable for smaller printers / Delta Printers, and don't handle higher accelerations well, but just for context this is a good video.



Thanks

Alex