Steppers shuddering when I pull the belts through fast

Hi, I have built the MPCNC up to the point that I am ready to power on the Jackpot and start testing/calibrating it.

Problem is when I move the gantry around I get pretty bad shuddering. I loosened the easily accessible bolts on the trucks and most of the bearings can spin freely when turned by hand without the gantry moving.

That still didn’t fix things so I unscrewed the belt holders from the corners. Now the gantry moves around easily. I tried pulling the belt through the trucks by hand back and forth and I sometimes get shuddering that seems to come from the stepper motors. If I pull the belts through slowly the shuddering goes away.

What can I do to fix this? Is this a problem or is this normal? Is it a problem with the stepper motor itself?


You probably know this, but moving the steppers too fast when they’re electrically connected to the drivers induces a current and can ruin the drivers.

Otherwise, I don’t know that I’ve seen anything I would describe as shuddering, but I suppose that could indicate misalignment between the idlers and the pulley. Did you purchase all the parts from V1E or did you self-source?

If you purchased from V1E I’m sure @vicious1 will chime in.

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With the Jackpot board disconnected from power I unplugged the stepper motor and now the motor does not make noise when I pull the belt back and forth through it.

Having the steppers plugged in even without power to the Jackpot board must have been the problem. Hopefully I did not damage the drivers.

Thank you.

You really should not keep doing that.

When you run a stepper it turns into a generator, do not move them by hand more than you need to, especially if they are plugged into something.

Lesson learned.

One more question, should you be able to rotate the bearings by hand without the gantry moving? I want to make sure they are tightened properly.

Yes and no. Easily, no, can you, yes. You just want them touching, not clicking loose.

Thank you. Hopefully I will have it up and running and calibrated by the weekend.

Thank you for all your hard work.