[neilb]

hi,

in the middle of converting my benchtop mill to cnc, i have done the ball screws, but i could do with some tips on belts and pulleys. what size pulleys would be ideal? am i right in thinking that having a larger pulley on the ball screw, instead of the motor at say 2:1 is ok? any good places to buy them from around melbourne? or aus? or overseas?

sorry if this has been covered before

thanks neil

[109jb]

Depends on the motors you are using.

Stepper motors should be run direct drive (1:1) because they lose torque rapidly. You want them turning slow, not fast. Putting a reduction drive on them makes them run fast where they have little torque.

Servos on the other hand like to run fast, and have less torque, but the torque remains constant to higher rpm, so they like reduction drives.

[skrubol]

Nowhere near enough info to answer your question. What's the pitch of the ball screws? What steppers and drivers are you using? Power supply voltage?

[neilb]

thank you for the help guy's, i'm new to cnc.

as to your advice regarding 1:1 drive for stepper motors, i decided to get a t5 48t 10mm pulley for the motor and a t5 36t 10mm for the ball screw. i'll try these and see how it goes. my thinking is it's close to 1:1 but on the beneficial side to the motor.

the ball screws are 16/5 the stepper motors are fairly big i think, nema 34 8.5Nm for the x + y. i shall get a smaller motor for the z

[Zenji]

If you have belt drive you can choose any reduction.
100x50 rhs 3mm wall is a good match for nema34, plastic caps available to seal.
Direct drive is a straight jacket in design terms.