Hi Roger,
CPR stands for counts per rev. It is usually applied to an encoder.
If an encoder has 2500 lines, it sometimes called pulses/rev or PPR then because of the quadrature placing of the opto-detectors
it will have 10,000 counts per rev or CPR.
If you set your microstepping to 1/8th (recommended) then your steppers will rotate exactly one revolution when the drivers are presented with 1600 pulses or CPR.
Lets tackle the Z axis first. If the stepper rotates once with 1600 pulses and the z axis will advance 2mm, being the pitch of the ballscrew.
The 'steps per unit' value that you put on the Z axis tuning page will be:
StepsPerUnit=1600 / 2
=800
Easy!
Now the X and Y axes are not so simple. You say they are belts with a 24 tooth pulley? What pitch are the teeth on the belt?
For the purposes of demonstration I'm going to assume 3.15mm pitch (1/8 inch).
StepsPerUnit= 1600 (steps per motor rev) / (24 teeth x 3.15)
=21.16
You will have to round to 21 steps per unit.
Note this is very course resolution, every pulse will advance either the X or Y axes 1/21 (=0.05)mm. Is this what you expected or wanted?
Craig
No need for rounding in Mach3. Mach will be perfectly happy with fractional steps per.