LabVIEW to control Scanning Electron Microscope(SEM)

[Rugby]

I have a project involving an SEM with 3 stepper motors that do not have any feedback mechanism(encoders). I am using a 7344 controller card and the MID-7604 power amp/controller in conjunction with the FlexMotion library. I wrote a simple application to test our set-up, and noticed that if I incrementally step in one-direction [while counting the number of steps], I cannot go back(in opposite direction) to the same starting point in one 'large step' simply multiplying by the number of steps taken. I have turned off the primary feedback(set to '0') in each of the motors configurations. Note: the motor has 400 steps per revolution. I have tried altering the step sizes, and each yields the same undesired result. It appears t
hat once I try to go back into the opposite direction, the motor overshoots by about 1 step.Any help would be appreciated.

[Morten]

Depending on your acceleration and the load on your stepper motors, they can certainly miss steps. This is why you need encoder feedback to ensure that you know exactly where your motor is located at all times. The board will send out the control signals, but if the load is high or if you have a high acceleration, you might not end up where you expect. Try changing your acceleration and try testing the motors without the load.

Hope this helps,

Morten Jensen
National Instruments