[brunoalokacija]

Hy everybody!

I am new at this and I am having problems calculating how many milimetars does my stepper motor do per one rotation. My stepper motor is PM55L-048, and the number of steps per rotation is 48 (7.5 deg). Do I need information for my ball screw? Thanks for your help in advance.

[keebler303]

Please search, this has been covered 1000's of times.

You need to know the # of microsteps for your driver

the steps per rev of your motor (48)

and the pitch of your screw (mm/turn)

[Jade York]

I can help you out, I just need to know how the motor is coupled.

Jade York
888-939-7250
Servo Motors and Electronics - Buy or Repair | Repair Zone

[sswitaj]

OK, here's the formula...

First, figure out how many step pulses you need to turn your motor one full turn. The base number here is the number of steps per revolution (in your case, 48) but unless you are using a very simple driver, the number will be modified by your driver, which will do fractional steps.

A 'typical" mid-sized stepper will do 200 full steps per revolution (1.8 degrees per step) but if you drive that from say, a common Gecko 201 at 10 microsteps, then it will take 2000 steps into the driver to do one full motor revolution.

If you don't know the details of your motor and drive, you can find this experimentally, by making your motor go 10 full turns. You issue a specific number of pulses (say, 20,000) and figure out how many motor turns this gave you, adjusting the number till you get ten full revolutions (then, of course, divide by 10).

This should be an even multiple of the native step count of the motor. Typical values are 1x, 2x, 4x, 8x or 10x.

It's not going to be something odd like 5.678x. If you get a number like that, (and you don't have a gearmotor) you did something wrong.

Next, figure out the gearing ratio from your motor to your lead screw. Unless you're directly coupled to the shaft, there are typically some pulleys (or, less commonly, gears) in the path. figure out the ratio for each stage.

*Do not guess*. Do not try to figure it out from turning the shafts. Take the belts off and count the teeth on each pulley.

Say your motor pulley has 20 teeth and your ballscrew pulley has 60, then you have a 3:1 ratio.

Multiply the numbers together. 2000 motor pulses per motor turn X a 3:1 ratio = 6000 motor pulses per *ballscrew* rotation.

Now figure out what the pitch of your screw is. For accuracy, measure 10 threads on the screw and divide your measurement by 10. This is usually a "standard" number, like 2mm/turn.

Take the inverse of your pitch, in this case 1/2. This is how many turns you have to turn the screw to go 1 mm.

Multiply that number (1/2 turn) by how many pulses you feed the driver to turn the screw once (6000, see above), for the system in our example you's use 3000 turns per mm.