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### Author Topic: A couple of design formulas wanted  (Read 2700 times)

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#### Stuart_H

• 34
##### A couple of design formulas wanted
« on: August 15, 2013, 06:36:08 AM »
Good evening guys,
Some time ago I was given a formula to work out what holding torque requirements i needed of a stepper motor to run the rack and pinion drive system of my router. It considered the weight of the axis to be moved and the speed of travel. Unfortunately I have misplaced it. Also another formula to work out the power supply voltage to a Stepper to get the best performance.

If somebody has this info, I would very much appreciate it.

Stuart

#### RICH

• 7,427
##### Re: A couple of design formulas wanted
« Reply #1 on: August 18, 2013, 07:48:35 PM »
Stuart,
You will find basic info on the Gecko Drive site. No use me repeating it here.

How much torque do you need? Calculators by many of the motor manufactures are based on a number of assumptions and thus they are subjective and get you in the ball park. Sizing is not straight forward since a few things come into play that are not calculated....like:

1.Torque to just move the axis ( this can be more than one thinks on a tight system)
2. Acceleration not only from start but when doing 3D  cutting since it becomes important
3. Torque required at the feedrate and material being removed, which can be calculated / estimated for metal but I have never seen anything for differeNt kinds of  wood.

Note that power ( speed x torque ) is what your after.
So be conservative on the torque requirements since  the cost is not that much more for the motor, but, do make note that all of the sizing is a comprimise and rationalization of desired operating conditions.

RICH

#### Stuart_H

• 34
##### Re: A couple of design formulas wanted
« Reply #2 on: August 20, 2013, 04:01:55 AM »
Thanks Rich,
I shall have a look at the Gecko site for the info. I appreciate its probably not as simple as a basic calculation to get a realistic figure.

Stuart