X-axis jerkiness when manually moving it

I’m brand new and just finished assembling the Shapeoko 4 XXL and have not plugged it in yet. I was tidying up the cabling and noticed that when I push the router assembly along the X-Axis, I sometimes get a bump or a jerk. If I push it slowly, it’s smooth but if I attempt to move it fast along the X-axis (all manual, no power), I get a jerk here and there. If I change directions quickly (i.e., push left and then push right), I get the jerk as well. If I move the whole gentry along the Y-Axis, it’s always smooth.

Is this an issue I should be concerned about? Is this a belt-tightening issue? I also noticed that right bottom V-wheel on the X-axis assembly is looser than the other (I can spin it with everything attached whereas the left bottom wheel, if I try to spin it, the whole assembly would move).

Thanks!

The stepper motors are generating voltage as you move the carriage. Very normal

“Edit” Did not address the wheel. I would check square on your machine. There should be even pressure on the four wheels. Being able to rotate one could also be belt tension.
Welcome. Enjoy your machine.

2 Likes

As noted, the stepper motors function as generators when pushed and will every so many rotations generate sufficient current to cause the machine to jump to the nearest full step — please limit pushing the machine when belts and motor wiring are connected to the bare minimum necessary.

For the V-wheels see:

I’ve read else wheee the nut needs to be turned anti clockwise??

My recommendation is that one tensioned, the eccentric nut and bolt be treated as a unit, and when adjusting the eccentric nut to adjust the V wheel the nut and bolt be turned as a unit using both wrench and hex key.

When is the right time to do this tension test? In the manual, this was done before the Z-axis and router were installed, which added significant weight to the whole assembly. When it was just the X-axis gentry, I couldn’t spin the wheel without the whole (lighter) gentry moving. However, once I have the Z-axis and router installed, now I can spin the wheel without the entire assembly moving (albeit it’s not free spinning).

Good to know about not moving the head with belt and wiring connected. Not sure if I missed it in the manual but I think if that warning isn’t in there, it should be added. I had been testing the smoothness of the movement throughout assembly to ensure that I had everything squared so it was a bit surprising that right before I was about to plug in, I suddenly felt jerkiness in the motions and tried to diagnose what I had done wrong.

Thanks Will for expanding on that.

Will pushing the gantry like that cause issues? I do it often.

Yes, it can push up sufficient current to the controller to damage the stepper driver chips.

Thank you Will.

Learning every day

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.