Idler pulleys may need strengthening


After about 1.5 months of regular use, I finally broke my first part. My X idler pulley broke apart during a print, dropping broken pieces everywhere. I have already replaced the part and printed spares, but I’m thinking it might need some beefing up. I didn’t have it over-tightened in the yoke, and my belt tension isn’t overly high. Looking at the pieces, it looks like the flange separated on one side. Perhaps the flange needs to be a little wider, so it has more material holding it to the center hub piece.


Lucky you :stuck_out_tongue:

I put some bike chain lube on mine (that’s all I have). It seem to remove any friction it had with the X-belt tensionner, but it might have degraded the PLA since that little arm broke :S


Mine is ABS, and I didn’t add any extra lube. The bearings came pre-greased, so I figured that was good enough.


I think I never installed the bearing properly. The X tensionner arms always rubbed on the flange when I put any torque on the screw holding the bearing. So I lubed the flange to stop the friction with the arms.

It’s as if I forgot installing washers so the bearing hub would stay fixed on the x tensionner arms.

Right now the bearing is mostly rotating freely around the screw. Haven’t got any issue so far (minus the break) and I’ll replace the whole X assembly soon anyway :smile:

Got a picture of how you secured the bearing to the tensionner? I’m just curious to see what I’ve been missing for almost a year now!


I used an M4 lock nut, so that I didn’t have to tighten the assembly too much. The nut is just tight enough to keep the screw from walking back and forth, but not squeezing on the yoke at all.


I see the X-tensionner was modified to include a small extrusion that push on the center hub of the bearing. I’m running a Wilson TS which doesn’t seem to have such a thing. I’ll print the new version :smile:

Thanks for the photos


My pulleys on X and Y axis are holding up well after two months. Remember that the screw holding them in place should not be tight. Mine became squeaky after awhile and I did lube them a bit with some synthetic grease which quieted them down a bit. Would like to upgrade to molded delrin bearings at some point since these printed pulleys are round but not perfectly round. Thinking durability and possibly print quality may improve. Looks like Marty has a revised x-tensioner to accept the molded pulleys… He references them in a video as “xy-tensioners-wide.stl” but I couldn’t find them on the github site :frowning: