Tormach Stepper Speed During Rapids Question

[BobWarfield]

Was playing with some numbers and a question came up.

Tormach quote a resolution on the machine of 0.0001", a tenth. Presumably that tenth represents a single step commanded of the stepper motor.

Rapids are quoted at 65 IPM, so, if we do the math:

65 IPM / 0.0001" = 650,000 steps per minute

Given that a typical stepper does 200 steps per revolution, the poor little motor is apparently running at 650,000 / 200 = 3250 rpm.

I assume the Tormach steppers don't run at anything like 3250 rpm during rapids, most steppers don't produce much torque that fast. Is the resolution perhaps derived from microsteps?

The Tordrive document claims 10x microstepping, which would put things at an almost too slow 325 rpm. 4x microstepping would put us at 800 odd rpm, which sounds about right for a typical stepper torque curve.

What rpm do the steppers move at during rapids?

[philbur]

I believe the answer is 325 rpm. The motor is direct drive on the ballscrew, which has a 5mm (0.2") pitch.

Phil

Originally Posted by BobWarfield Was playing with some numbers and a question came up. Tormach quote a resolution on the machine of 0.0001", a tenth. Presumably that tenth represents a single step commanded of the stepper motor. Rapids are quoted at 65 IPM, so, if we do the math: 65 IPM / 0.0001" = 650,000 steps per minute Given that a typical stepper does 200 steps per revolution, the poor little motor is apparently running at 650,000 / 200 = 3250 rpm. I assume the Tormach steppers don't run at anything like 3250 rpm during rapids, most steppers don't produce much torque that fast. Is the resolution perhaps derived from microsteps? The Tordrive document claims 10x microstepping, which would put things at an almost too slow 325 rpm. 4x microstepping would put us at 800 odd rpm, which sounds about right for a typical stepper torque curve. What rpm do the steppers move at during rapids?

[RTP_Burnsville]

Hi,
For conversation lets assume the motor has 200 steps per revolution. The following explains the multiplication feature?

One Step setting with one input step pulse = 1.8 degree motor rotation.
Half Step setting with one input step pulse = 0.9 degree motor rotation.
5 Micro setting with one input step pulse = 0.36 degree motor rotation.
10 Micro setting with one input step pulse = 0.18 degree motor rotation.

Summary:
A half step setting would require two step pulses to have 1.8 degree rotation.
A 5 micro setting would require 5 steps to have 1.8 degree rotation.
A 10 micro setting would require 10 steps to have 1.8 degree rotation.

You now need to know the threads per inch of the ballscrew to get your answer.

Robert P.

[philbur]

a quicker route is:

65 ipm x 5 revs per inch = 325 rpm.

Phil

Originally Posted by RTP_Burnsville Hi, For conversation lets assume the motor has 200 steps per revolution. The following explains the multiplication feature? One Step setting with one input step pulse = 1.8 degree motor rotation. Half Step setting with one input step pulse = 0.9 degree motor rotation. 5 Micro setting with one input step pulse = 0.36 degree motor rotation. 10 Micro setting with one input step pulse = 0.18 degree motor rotation. Summary: A half step setting would require two step pulses to have 1.8 degree rotation. A 5 micro setting would require 5 steps to have 1.8 degree rotation. A 10 micro setting would require 10 steps to have 1.8 degree rotation. You now need to know the threads per inch of the ballscrew to get your answer. Robert P.

[RTP_Burnsville]

I agree...... 325 is the answer with a 0.2 ballscrew.

I just added the microstep info as so many I talk with are totally confused on the issue.

[BobWarfield]

Thanks guys, gratifying to see my 325 rpm estimate was on, and that you need to use the 10x microsteps to get to 50 millionths.

Best,

BW