How to calculate belt step.

[Mcyoda]

I am kind of familiar with step motor and screw but when come to belt and servomotor I am lost.

For example I plan to use single end belt system with reduction of 4.8:1 similar to the attached picture.

The main belt: T5
Main pulley drive T5: 20 teeth
Belt Reducer: 4.8
Servomotor RPM max: 3200
steps for Mach: ?
Encoder: 500 CPR

What other information I need to calculate the steps Mach3?

Thanks

Rocky

[blackbeard52]

Actually I will chime in...I am not 100% but looks to me that the motor step i.e. 180 steps per rev divided by diameter of pulley should give inches or mm per rev...or pretty close, then fine tune in Mach diag. screen

[Mike Everman]

"The main belt: T5
Main pulley drive T5: 20 teeth
Belt Reducer: 4.8
Servomotor RPM max: 3200
steps for Mach: ?
Encoder: 500 CPR"

OK,
T5 is 5mm per tooth.
One rev of drive pinion goes 100mm.
Input reduction means 4.8 revs at motor for 100mm linear travel.
4.8*180 steps per 100mm (.864steps/mm)
4.8*500 encoder counts per 100mm (2.4 counts per mm)

Any way you slice it, you'll want more resolution. US digital can get you 8,000 encoder counts after quadrature.

[Mcyoda]

Originally Posted by Mike Everman "The main belt: T5 Main pulley drive T5: 20 teeth Belt Reducer: 4.8 Servomotor RPM max: 3200 steps for Mach: ? Encoder: 500 CPR" OK, T5 is 5mm per tooth. One rev of drive pinion goes 100mm. Input reduction means 4.8 revs at motor for 100mm linear travel. 4.8*180 steps per 100mm (.864steps/mm) 4.8*500 encoder counts per 100mm (2.4 counts per mm) Any way you slice it, you'll want more resolution. US digital can get you 8,000 encoder counts after quadrature.

Last few days I tried to digest the whole calculation. I am even more confused at the moment.

1. Where do you get the 180 steps from?
2. Why is 0.864 steps/mm not 8.64?
3. 4.8*500 ecoder counts per 100mm ( isn't it should be 24 counts per mm?)

[Mike Everman]

No wonder there was no response! Everyone was thinking: "what is this yutz Everman talking about??"

You are of course right. It is 8.64/mm on cardinal steps, and 24/mm on encoder counts, and I neglected to consider microstepping in my sleepy post, so you will have plenty of resolution with even modest microstepping. I would, however go with higher encoder resolution if you are going to use a servomotor.

I was thinking just of cardinal steps, which for most steppers is 180 per turn.

I sincerely apologize for my sloppy help! I should have waited till I'd had some sleep before opening my virtual mouth.

Cheers.