Zaxis Ball screw question

[MartinS]

I was interested and waiting for replies to this question............surprised there are no comments yet

[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.

[driftspin]

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.

Ok this answers the question... i will change my bomlist..
1605 for z 1:1 pullys.

I have zero hands on experience so...

Grtz Bert.

Verstuurd vanaf mijn SM-A320FL met Tapatalk

[komatias]

For a Z I would belt drive and reduce to 2:1. As Z motions are not always as long as the X and Y you can live with a slower speed.

The 2:1 will also ensure you do not drop as easily when the motors are off. It may not be a concern of course if you are using bog standard screws.

(I know on my little CNC conversion kits, because I am using ground screws, you can easily backdrive them. Then again the head weighs around 30kg there)

[Neale]

I reckon that my moving Z components weigh around 15kg and that seems OK with 1605 and 1-1 pulleys. However, one of the great things about belt drive is that you can always change ratios if you need to without too much work.

[routercnc]

My Z is also 1:1 with pulleys on 1605 and works fine