Rostock Max Z Stepper Issue

[videospecialist46]

I just finished my Rostock Max setup and am trying to calibrate for the first time. I've flashed the most up-to-date Marlin firmware, etc. When I send the G28 command in Repetier, the X and Y skates move up, but the Z vibrates up and down slightly by about 1/4 inch. I've tightened the stepper driver gear and tried reversing the Z direction in the firmware to no avail. What could be causing the Z axis to not move up, but just vibrate in place?


Thanks for any help on this, I'm stuck.

[rs50pilot]

If its wired incorrectly it will do that.

[videospecialist46]

I've triple checked the wires and that can't be the issue. I just ran G28 again and let the X and Z skates hit the end stops (while the Z remained vibrating in place versus moving up or down). The X and Y stopped as they should at the end stops and the Z kept vibrating. After resetting the maching, I ran G28 again and now the X stays up at the top, the Y vibrates like Z (only up by the end stop switch) and the Z remains where it has been, about halfway up the t-slot, just vibrating in place. It really seems like some firmware or setting issue in Repetier, unless I've blown the stepper drivers on the RAMBo, but that shouldn't be the case...

[gabrielk]

I found that on http://www.reprap.org/wiki/Calibration, but I don't know if that can help you since we all have the same stepper motors, and settings should be the same or very similiar. Please correct me if I'm wrong. (I'm learning everyday)

Motor vibrates without turning.

This generally means that you don't have sufficient current to the motors. You could also have a problem with a part sticking which stops the motor from being able to drive the axis. It might also be possible to be way off in your steps/mm (eg typo), when steps/mm is double the correct value your motor might vibrate on the spot.

Axis movement pauses momentarily and then resumes.

You may have too much current going to the motor which is causing the pololu to over-heat. Reduce the current. This can also be caused by firmware but check your motors first. Another possible cause is the set screw on the gear is not tight enough.

[mhackney]

I'm betting a loose wire at the connector. Easy check - switch your Z and one of the other connectors (say X) at the RAMBo. Then, which stepper works? If Z now works (when you do a G1 Y10 for instance) but X doesn't, then the problem is likely the driver or configuration (over amp or too high feed rate). If Z still doesn't work, then it's either the wiring/connector or the stepper.

If the little pins are not inserted all the way into the plastic housing on the connector you can get intermittent problems like this.

[mhackney]

I forgot another obvious potential - the Z axis pulley could be slipping. Make sure it is tight on the stepper shaft.

I would approach this debugging in this order:

1) check mechanicals - tight pulleys, carriage not binding
2) electricals - as per my previous post, swap the Z and another stepper at the RAMBo and follow the diagnostics.

[videospecialist46]

You were absolutely right about the connection on the stepper motor pins not being tight/fully connected. I redid my crimps and made sure all of the stepper motor wires were securely pushed into the 4 pin connectors and that did the trick...G28 works like a charm now!

Thanks for the help!

[mhackney]

Great! I had a similar problem with a CNC mill I built last year. Drove me crazy until I switched ports and realized it was the cable and not the stepper or controller.

cheers,
Michael