Can’t get rid of the v-wheel bumps along the Y Rails

I’ve been trying get my shapeoko 3xxl squared away and fine tuned. I am running into the issue where i am getting bump feedback when i am pushing the x rail back and forth. Note: the belts and wires are off and not attached yet. I go to adjust the eccentric nuts on the v wheels until the wheels have enough friction to the point where i turn the wheel by hand and the rails move. How tight or loose should the wheels be? I havent been able to get rid of the bumps for the past two evenings.

I suspect that one of the Y plates is touching before the other and that requires squaring the machine. I think that there is a video somewhere explaining this process.

The v wheels should be tightened until you can’t turn them with your finger.

Is the bump happening at regular intervals when you slide the plate or randomly ? Could be a flat on one of the V-wheels, maybe visually check all of them ? I understand you feel the bump when holding the plate and moving the rail, does it also happen when holding the rail and moving the plate ?


I have also noticed a “bump” on my machine. Except I Would say if feels more like a “hitch” and it is at regular intervals. I believe my issue is related to the motors though, because it seems to be more pronounced if push harder/faster on the x rail. I notice it both along the Y axis as well as along the X axis when sliding the carraige back and forth. It hasn’t seemed to affect performance in any way for me though.

I squared the machine up and measured diagonally achieving square within less than 1/16 of an inch. When talking about the wheel shouldn’t spin by manual force, how much force in a sense are we talking? If i keep the rail locked in position i tighten the wheels to the point where it cant be manually spun, but i am putting in a lot of force to spin it

They seem to be happening more at random

I feel it when I am holding the rail and pushing. Not so much when i am holding the plate and moving the rail.

What you describe sounds like the effect of the current that is generated when one pushes the rails while the machine is turned off (the stepper motors then work as generators, induce some current back into the controller, you probably see the blue LED shining when doing so), and is 100% expected though you should probably move slower when possible, the stepper drivers don’t like this unintentional current so much.

What Erik sees is different, since he does not have the belts on, so the pulleys/motor shaft do not rotate, hence no current. We still need to figure out what happens in his case :frowning:


I would inspect the V rails (but I guess you already did), and then have a close look at each of the V-wheels individually (which you probably also did). I’m puzzled by the random occurrence of the bump, assuming the V-wheels are tight enough that they are not slipping…
Silly question, does it also happen when you flip the rail/plate upside down ? It might give an indication as to which wheel is misbehaving

What I’m talking about it to take your index finger only and trying to spin the wheel down from the top and up from the bottom. It should not move in any direction. If it moves, you need to tighten just a bit and try again until it stops moving.

I was not sure if the bump you were talking about was at the end of the Y travel or somewhere in the middle. What I’m talking about is a bump at either end of the travel. If it is in the middle, does it happen in a particular location always, in one spot or a repeated bump along the axis? If one spot in the middle, it might be the rail that has been damaged possibly by over-tightening the V wheels or from being hit. If there are bumps at regular intervals, I would suspect the V wheels.

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I havent tried flipping the rail upside down, was trying to avoid taking the rails apart from the frame but I’ll try that. I inspected the V rails and I didn’t find any divots or irregular spots out if the ordinary. I inspected the v-wheels as well, while i did notice some very small striations on the inner sides of the wheel. I looked further and the bumps aren’t happening at the striations locations on the wheels so i ruled those out. I may have it to tight, i saw the comment that i should be only be spinning the wheel with my index finger rolling the wheel. I am gripping the wherl between my thumb and index finger pretty tight and testing the tension against the force of me spinning the wheel while holding the rail in place with my other hand…

This might be, luc.onthego you mention i should only be using my index finger to roll/spin the wheel. Ive been grabbing the wheel between my index finger and thumb with a pretty strong grip and spinning it while holding the rail in place. Ive been tightening the wheel to the point where I can’t hold the rail in place when i spin the wheel. In other words i tighten to the point where i spin the wheel manually whole holding the rails makes the rail move to the point where I can’t hold the rail in place and spin the wheel. If that makes sense.

Others can chime-in but I think you may be over-tightening the wheels and in the process you may damage the wheels and rail. I wish there was a better system than “feel” for this.

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It’s pretty hard to do any significant damage even overtightening. Ive always held the rails and if the wheel spins in place then tighten.

The rails shouldn’t take more than a pound or two of force to move with everything tensioned correctly (no belt).

Its totally possible you just recieved a bad bearing in a wheel. Although I did try non carbide3d wheels and had “bump” issues.


I dont know what the tolerances is on these machines. Am i or should i be expecting like a super buttery smooth travel across the rail? The bumps are very very very minor and hardly noticeable, buy my ocd tenancies and attention to fine details is noticing the fine bumps. Its as fine as rolling over a strain of hair or a grain of sand. Im stumped at what more i can do to eliminate these fine bumps trying to achieve a smooth travel with zero bumps. Belts and wires are all disconnected and not attached while ive been trying to tune this

The wheels should be adjusted per:

If the belts aren’t connected and attempting to adjust them per the above doesn’t result in smooth motion please remove one wheel and disassemble it and inspect the assembly and bearings — if nothing obviously wrong is found and the bearings rotate smoothly, repeat with another.

Let us know what you find out, and if you need replacement parts let us know at and we’ll work this out.

If you move it very, very slowly, does it still happen? I suspect what you’re actually feeling is the back EMF powering up the board (the steppers work as little generators). Clearly the machine is off, or you would have much more difficulty moving them.

If you move it very, very slowly and it does not happen, it’s just the back EMF from the steppers, and not a problem.

Thank you William Adams, that video was very helpful and it resolved the issue. That video would be good to add into the instructional portion of putting the shapeoko 3xxl together and i would move the squaring of the machine and fine tuning of the v wheels up in the list of instructions rather than putting that step the very end. Thanks again for the support everyone

OK but what was the issue?

After reviewing the video william posted that explained how to adjust the wheel better, it was determined that my issue was my error of over tightening the eccentric nut. According to the video i was only to adjust the wheel until it made contact with the rail, then fine tune it to where manually spinning the wheel with a finger would result in moving the center rail. So overall i was over tightening.