Mendel X belt bearings problem

Hi all. I have a problem with the X belt system. Basically, as the X carriage moves across the x axis, the belt that drives the carriage moves up and down in the z direction due to the fact that some of the bearings that the belt goes around have an axis of rotation that is slightly off from in the z direction. Therefore as the belt is drawn across the bearing, the belt is forced in an upwards or downwards direction depending on which way the belt is moving. This causes the belt to hit the mudguard washer at the bottom or the printed bracket at the top, causing a lot of friction and making the x carriage traversal hard and not smooth at all.

I think that if all of the bearings were aligned better such that the axis of rotation was dead on the z axis, I wouldn't have this problem. Has anyone had this problem before? How can I make the belt stay perfectly flat?

Thanks!

On mine the belt falls to the bottom due to gravity and runs against the mudguard washers, which are smooth, so I don't have a problem.

Why are your bearings not vertical? The bottom of the bracket should be flat and the bearings pull flat against it.

Perhaps less belt tension would help, although I have mine pretty tight,

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It might be the fact that I don't have a washer on the m4 bolt cap side. I notice that the bolt head is digging into the plastic a bit and this might cause the unevenness that I am observing in the fit, causing the bolt to lean a bit out of "verticallity", if that's a word. I left out the washer because The 16mm m4 bolts that I used were just not long enough to get the assembly like so: Bolt head->washer->printed bracket->washer->bearing->washer->mudguard washer->locknut. Maybe I should try 20mm bolts instead of the 16mm.

Hi:

I had endless problems with this in my Techzone mendel. I also had only one washer. Finally, I cut my 6mm belt to 5mm, used both washers (placed with the most rounded side inward) and kept the belt loose. This eliminated most of the problem. I suggest you switch to a design with a vertical x belt as soon as possible. Either Prusa or mine (Simplified Ball Bearing Mendel) have this, maybe others also. Get printing and you can be independant.

john

Perhaps the printable bearing guide that comes with Prusa iteration 2 would help solve your problem. I actually redesigned it a little since I found that it's hard to make the inner and outer race concentric in the current design. I just posted the files in thingiverse.



edit:

I just realized this issue is with the Sells Mendel. You can probably modify the 608 design for the 624 bearings, but it probably would need to be printed with at a higher resolution with a nozzle smaller than 0.5 mm.

Edited 2 time(s). Last edit at 03/26/2012 05:33PM by brnrd.