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Estimating stepper torque

Dale Dunn

Estimating stepper torque
April 21, 2014 10:18PM

Registered: 13 years ago
Posts: 485

Forgive my ignorance please, but I need to estimate the maximum torque some steppers I have will exert in the system so I can size related components. I have the rated current, voltage and holding torque. Does the torque roughly scale with electrical power applied? Or do I need to put in the time to comprehend steppers? I did some Googling to see if I could work it out, but the topic is larger than I expected.

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misan

Re: Estimating stepper torque
May 27, 2014 07:03AM

Registered: 12 years ago
Posts: 972

Torque vs speed graph on stepper motors is what you are looking for. Basic idea: torque decreases with speed. Holding torque is the max torque it can achieve (zero speed). Torque increases with current (up to a point when it won't increase anymore but you still can fry the motor).

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Traumflug

Re: Estimating stepper torque
May 27, 2014 07:27AM

Registered: 13 years ago
Posts: 7,616

With modern constant current stepper motor drivers torque is roughly constant up to some speed. Which speed heavily depends on the motor type. Also, doubling voltage doubles the speed range.

You can find some real world measurements in the wiki (search for "torque"). Also keep in mind that there's a maximum RPM of the steppers depending on the printer type, so it makes no sense to optimize for 2000 RPM.

Generation 7 Electronics	Teacup Firmware	RepRap DIY

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misan

Re: Estimating stepper torque
May 27, 2014 08:18AM

Registered: 12 years ago
Posts: 972

Hi Traumflug,

That seems to be the case till you reach corner speed, according to [www.geckodrive.com]

But it is unclear to me whether we are passing that limit or not on our machines.

misan

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Traumflug

Re: Estimating stepper torque
May 28, 2014 07:27AM

Registered: 13 years ago
Posts: 7,616

Calculate it smiling smiley

You have a rough steps/mm value, you have a speed expectation, you know the pulley's diameter, so you can calculate RPM at maximum speed.

Generation 7 Electronics	Teacup Firmware	RepRap DIY