Shapeoko 4 XXL Top back wheel on left y rail keeps falling off

This wheel doesn’t have an eccentric nut but it falls off no matter the tightness and ruined a piece I’m working on.


All the lower v-wheels should have an eccentric. The top wheels gravity and the adjustable lower v-wheels keep the side plate in contact with the rail. So check to see if your eccentric is still in the box or was never there. You will need to get one and put it on otherwise your plate cannot be adjusted to stay on the rail. All v-wheel machines have the eccentrics on the lower v-wheels.

The upper v wheel is falling off. There is a lower eccentric

Sorry I guess I mis read your post. If the upper wheel is falling it can because of two reasons.

  1. Your eccentric on the lower v-wheel needs adjusting.
  2. Your gantry is not square meaning that your Y rails are not parallel to each other.

If you eccentric is adjusted properly the v-wheel should not pop off the rail. So check the eccentric adjustment and if that is good check your machine is square.

It sound like the end plate is slightly rotated, so that V Wheel is too high.

Something to try:

  • slightly loosen the bolts holding the end plate to the extrusion.
  • adjust lower V Wheels until all wheels seem snug against the rails.
  • Tighten bolts.

You may need to loosen the bolts at both end of the extrusion to get the ‘play’ needed to have the plate sit properly.

Once you are do, check tram!

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I see a lot of sawdust on the wheels and other components I would clean the machine and then make the adjustments.



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