Carriage moves freely in X direction with motor engaged

The carriage on my SO3 XL (my sister’s actually) is slipping in X. I can run it, and it moves in all directions, so I don’t think it’s the motor. More importantly, I can push it freely in X when the motor is engaged (Y and Z hold solid as they should). I’m pretty sure the eccentrics are properly adjusted (they seem to be adjusted the same as those on the Y axis). The belt seems loose, but I can’t tighten it. The thumb screws are both adjusted as far as they will go, and they keep slipping back into their old “groove” when I try to reposition the belt in the clip. Do I need a new belt? Is there something else I should be looking at?

Possibilities are:

  • belt — possibly flawed, or insufficient belt tension
  • pulley set screws — put a witness mark and see if it moves

Not likely to be eccentric nuts/V wheels, and usually wiring / stepper driver issues are accompanied by horrible noises.

Write in to and we’ll do our best to assist.

+1 for the pulley set screws. If you have the Shapeoko powered on and you can move the X position either your pulleys are loose or the belt is extremely loose. I discount the belt but you can take it off and inspect the notches very carefully with a magnifying glass. The belt is tensioned by the belt holders. The belt holders are not adjustable. You double the belt over on itself and the groves lock together. If you have to take the belt off when you tighten the belt holders hold them with pliers straight while tightening the allen bolt. If you do not hold the tensioners they will twist as you tighten the bolt.

The belt is very obviously loose. My sister ordered a maintenance kit that arrived today. I’ll replace the belts (X for sure, and if the Y belts look worn I’ll do those as well), and If there are worn pullieys I’ll replace those too. I’ll report back (hopefully soon).

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The X-belt was very worn. I think sitting unused for a year wasn’t helpful. BUT this is not the issue. I can rotate the pully freely when the machine is on, which is not right. To test I disconnected one of the Y belts, and it indeed cannot be easily moved while the machine is on.

So, either the X pully is loose or the X motor isn’t getting power. It looks like I can adjust the pully set screws easily, but does anyone have tips about that (i.e. how do I avoid mucking it up). How do I test whether the motor is getting power? I’m looking at the log, but I don’t really know what to look for.

The pulley has two set screws. The motor shaft has a flat. You need to align one of the set screws with the flat on the shaft and tighten that down, then do the other screw.

And you already solved this with a new belt, but the method I used to overcome the belt wanting to slip back into the place it was before was to super glue the end of the belt where I wanted it. Drastic but it stopped it from slipping.

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Some people like to replace these tiny set screws with 10mm long cap bolts. This makes it much easier to tighten the set screws without fear of stripping them. Some people use thread sealer. If you use thread sealer use REMOVEABLE and NOT PERMANENT. Permanent required high heat and would possibly destroy your belt and/or motor.

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Update: one of the pulley set screws was missing altogether. I can’t find it anywhere, but it must have fallen pretty recently. I replaced it easily with a long handled hex wrench that I picked up on amazon. It was a little bit tricky getting the screw into place, but otherwise, it was a quick and easy fix. Thanks for all your input.

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