Zaxis Ball screw question

[Neale]

Not a lot of theory here, but this works for me...

I use 1605, 1-1 belt drive from stepper. Z feed rate is generally lower than X and Y, so you do not need 10mm lead ballscrews. I have never had any problems with downward creep of Z, even with power off, and that's with a big chunk (500x200x20) of tooling plate for the spindle platform and a 2.2KW spindle. I use 8x microstepping. This is not so much for resolution (I have a theoretical 0.003mm step increment) but for motor smoothness. Something around 8x seems like a good compromise between smooth running (fewer microsteps runs more roughly) and loss of torque (with too fine microstepping). However, testing with my touchplate, I have seen +-1 microstep (i.e. +-0.0003mm) repeatability. I doubt if the machine is that accurate when cutting, but even with intricate 3D machining, I have not seen any problems.