Y axis belt rubbing against wood plate, fraying?

[jasonwebb]

Right after I finished my last print (a simple Expo marker holder, which printed perfectly), my Y axis was having a really hard time returning to it's endstop. I shut off my printer, let things cool and then tried to manually move my Y axis carriage up and down.

When pushing the carriage upwards I feel considerable resistance, which I also feel to a lesser extent going downwards. I can visibly see the belt fraying and rubbing against the wood plate that is the top of the base. I can also see the belt twisting slightly.

It's a bit hard to see the idler bearings since it is all hidden inside the tower / stepper assembly, behind the tower beam, but when I feel around I actually don't feel anything different than on the other axes! Clearly something is misaligned, but I'm having some trouble pinpointing what.

I slightly loosened the bolts holding the two idler bearings together, hoping that the extra "play" would allow the belt to self-align, but it doesn't seem to have changed anything.

I can easily replace the belt, but I'm concerned that it'll just get frayed again right away unless I figure out what is causing this issue. Anybody have some ideas about what this might be a symptom of? Could the tower be so far out of alignment all of the sudden that the belt now doesn't line up with the idler assembly?

Here's a quick video of the symptoms: https://vid.me/4jX8

[KAS]

Are you able to look at the pulley to see if it's offset or backwards?

[jasonwebb]

Ah, it does look a little bit more offset than the other axes. Is there any way to adjust the pulley without disassembling the entire printer? It took so long to calibrate...

[KAS]

It's not the easiest thing to do, but yes you can remove or adjust the pulley without disassembling the base.

This should help locate the setscrews from the outside.
[img]http://i482.photobucket.com/albums/rr18 ... 201501.jpg[/img]

[jasonwebb]

I'll keep trying, but unfortunately it looks like I don't own any Allen keys long enough to reach the pulley. Short by a couple millimeters.

[KAS]

You might be able to loosen the belt and unscrew the stepper motor and pull it out.

[jasonwebb]

Yes! The belt had to be replaced anyway, so I was able to pop out the motor and take a closer look. The pulley was a little loose on the shaft, so I think the grub screw may have just jiggle loose or hadn't been perfectly tightened to begin with. I moved it back into position, gave the grub screw some more threadlock and tightened it down again.

Thanks for the help!