Problems setting microstepping on a Danaher P70530 with a NI PCI-7344

[BerndSchoelzel]

 Hello,

I'm actually trying to get a  NMB PPM25L-024stepper motor to work smoothly with the following setup:

- A PC with LabWindows and a NI PCI-7344 is connected to a 4-Axis UMI, then via direct cable to a Danaher P70530 driver. Finally the stepper motor itself is connected to the Danaher driver.

- On the P70530 all switches are left in default setting, so I can configure the driver via software. The step/rev are set to 200.

- In MAX, all settings are made for a open-loop stepper drive with no encoder. The steps/rev are set to 200.

The specs of the stepper motor are like this:

The settings of the P70530 and MAX allow me to drive the motor via MAX but the movement is very rough and noisy. So I tried to set the steps/rev to 400 in both the P70530 and MAX but no improvement seemes to happen. The only thing I encountered is the fact, that I had to enter greater numbers for the movement target steps than before to reach the desired positions. At 800 steps/rev the motor didn't move at all.

As far as I know there should be a way to use microstepping to reduce the noise and make the motor run more smoothly but I can't see a way to set up my equipment to actually make use of it.

If anyone could point me in the right direction I'd be very thankful.

Best regards,

Bernd

[Buechsenschuetz]

As far as I can see, your motor is supposed to have 24 full steps per rev. You should always use an integer multiple of the full step number as microsteps. Choosing 200 steps per rev would mean that each full step of the motor will be composed of 8.333 microsteps which is hardly possible. I do not know what the motor driver will do in this case but I would rather start with 240 steps per rev. Anyhow, with anything beyond 5 microsteps per full step, a motor should run rather smoothly. Another thing are resonance effects. A stepper driver is always supposed to drive a load with a certain inertia. If there is no such load, under certain condtions (low microstep rate and/or slow speed) a stepper motor shaft tends to oscillate. Some motor manufacturers offer damper discs suitable for their motors, try to attach one to the shaft. For a quick try, some kind of flywheel might help. 

[BerndSchoelzel]

Hello and thank you for your answer.

As you suggested, I tried to set the steps/rev to 240 both within the P70530 driver, as well as in MAX. But in the P70530 (via P7000 Tools) it was not possible, because the default toothcount for the motor was set to 50. It seems the P70530 only allows the setting of steps/rev in multiples of the toothcount.

Changing the toothcount to any value lower than 50 seems to be impossible because the tool forbids values smaller than 50. So I set the value to 96 (4x24) for and the steps/rev to 384 (1/4 microstepping) inside the P7000 tools. In MAX I set the value of steps/rev also to 384.

The motor is actually connected to some mechanical parts so it should be a certain inertia on the axis when moving.

After setting the steps/rev and toothcount to the new values the motor still runs very rough. From my point of view nothing seems to have changed to the settings I used before. The only thing that keeps changing all the way through is the number of steps I need to fill in MAX to reach the same position after I altered the steps/rev in the driver. Changing the steps/rev within MAX and not changing them in the P70530 doesn't seem to have any impact at all.

So there still seems to be some problem with the microstepping.

Best regards,

Bernd