Why am I loosing steps with my stepper motors?

[zimmer]

I am microstepping at 250 microsteps per ever step. This is needed because I am looking to test silicon wafers and a typical movement is around the order of 75 microns. I have found that I am loosing steps in my motion when I have tested a few pads out of about 512. I have concluded that my program is not at fault so there must be something wrong with the motion itself. I have set the current from my power drive (NI-7602) to 0.2 so the small motors I am using will not over heat after continous use. Does any know of a reason why I might be loosing steps and perhaps how to fix this problem? Thanks

[nestor-sg]

One thing to know about microstepping is that is not linear, in some cases a stepper will cause a non-linearity big enough to think that you are loosing steps. Are you controlling the stepper in closed loop mode? With a higher or equal precision (than the microstepping) encoder?

Nestor.

[zimmer]

I am using a open loop mode with no encoders. I am trying to reuse an old Alessi probe station that has two old stepper motors.

[algames]

Make sure that the stepper motors are rated for a higher torque constant than the inetrtia of your load requires, one thing to take into account when uing microstepping is that the more microstepping you apply, the more torque you will lose on the stepper motor. So if your system load and the load your motor can handle are very closely matched, then there is you answer and you will have to either reduce microstepping ratio or get a motor with higher torque rates.