X and Y Belts w/ rubbing/resistance feel and noise

Hey all,

I am new to CNC and am almost done assembling my S4 XXL. On my machine, there is some rubbing/resistance on both of the Y-Axis belts, as well as the X-Axis belt. This is both in the way it feels when the gantry is moved manually and clearly heard when it is moved. I have not powered on the machine yet. I have tried to tweak them tighter or looser to see if that solves the problem, but no luck. I did schedule an onboarding video call with Carbide 3D for late next week, but I was hoping to solve the issue beforehand and focus on other basic functions. Thanks for any advice you all are able to provide!


Check your v wheels. Since this is new it is not likely it is sawdust on rails or v wheels. The v wheels should only be tight enough to not slip but move carriages. Loosen bolt and adjust eccentric and hold eccentric with wrench while tightening bolt. If you tighten bolt without holding eccentric in place the eccentric will tighten by moving during bolt tightening.

Do not move axis too fast or stepper motors will be energized and it feels bumpy.

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Thanks for the suggestion! I will give this a shot tomorrow morning. Bumpy is definitely the correct adjective to use for this issue. I did notice the LED lights turn on when manually moving the axis back and forth, so that could be part of the issue, too. I’ll keep you posted!


When you move the carriages move the slowly and they should feel the same from stop to stop. If you have a particular spot where it is hard or rough then look at that area of rail. Otherwise the carriages should move smoothly without too much effort. Moving smoothly is subjective but basically it should not tire you out trying to push the carriages and they should be relatively the same effort all the time.

That’s energy generated by the motors (when the gantry is moved manually), that gets injected back into the controller, which supplies it with enough power that it will temporarily try in turn to drive the motors…and this feels like a bump during an otherwise smooth movement.

The test is moving the gantry slower, if the movement is smooth then that’s all ok. In any case you should not move the axes manually unless (very) slowly

Another way to test if this is it, is to unplug the X/Y/Z cables at the controller side, and repeat the test.

If when moving slowly (or with stepper motors unplugged from the controller) you still feel the bumps, and it’s not anything visible on the rails, then it could also be a flat spot or crack in one or several of the v-wheels.

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