Beware of the sneaky pulleys 😉
Yesterday I started building the printer and while assembling the XY-carriage it turned out that one of the pulleys was blocked. I thought that the bearing in it was damaged and I swapped it for another one. The second pulley fitted into the printed element completely differently. After comparing it, it turned out that one of the pulleys had a slightly wider inner sleeve, which caused additional pressure and as a result, the blockage. After moving the wider pulley to the place where there are two with the separator, it started working without any problems.
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Looking at your photo, I would say that the ball bearing is not fully pressed into the right pulley. But I am confused how that would have caused a blockage. Don't the printed parts into which the pulleys get inserted all have little "dimples" around the axle holes, which press against the central (stationary) part of the bearing only?
Edit: Or is the left bearing pushed in too far, causing the side of the pulley to rub against the plastic part because the "dimple" does not keep it at a distance?Â
RE: Beware of the sneaky pulleys 😉
All the pulleys in the set looked like the one on the left. The bearing on the right one was sticking out on both sides. I had trouble pushing that pulley into place, and after centering it with a screw, it turned with great resistance.
RE: Beware of the sneaky pulleys 😉
All the pulleys in the set looked like the one on the left. The bearing on the right one was sticking out on both sides. I had trouble pushing that pulley into place, and after centering it with a screw, it turned with great resistance.
Ok, thanks. So maybe the plastic mounting block was putting so much axial stress onto the bearings that it caused friction in the bearings themselves? Anyway, glad you spotted it, and thanks for raising awareness of this potential problem! Â
RE: Beware of the sneaky pulleys 😉
 I build my kit yesterday, and have the same "problem" some pull are like the one on the left, and some are like the one on the right.
So in the build, i have pulley with a lot of play, and some without.
Support tell me that it's ok, with the belt tension there is no problem with play or not, just the pulley need to turn smooth.
RE: Beware of the sneaky pulleys 😉
I wouldn't worry about the play. Once the belts are on and tensioned they will keep the pulley in its one position. What you need to ensure is that the pulley rotates freely.Â
 I build my kit yesterday, and have the same "problem" some pull are like the one on the left, and some are like the one on the right.
So in the build, i have pulley with a lot of play, and some without.
Support tell me that it's ok, with the belt tension there is no problem with play or not, just the pulley need to turn smooth.
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RE: Beware of the sneaky pulleys 😉
Yes, Prusa tell me the same thing.
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RE: Beware of the sneaky pulleys 😉
Are they using o rings for spacers on the pulleys like on the XL? If so I'd say the o rings are missing on that loose one.
RE: Beware of the sneaky pulleys 😉
Are they using o rings for spacers on the pulleys like on the XL? Â
No. They just rely on little raised bits on the 3D-printed mounts.
RE: Beware of the sneaky pulleys 😉
That's odd. I thought the on rings were a good solution as they offered some compliance but kept a nice fit.Â
Thanks letting me know.