Timing belts slipping

[dergoldstein 1]

After stopping a print mid-way, the positioning of the X/Y belts seems to have messed up. Usually the printer will move the print head to the back-left until both limit switches are tripped, to zero out the position, but now this doesn't seem to be working anymore and the UM2 will often try to move the print head beyond the "front" of the machine.

This happens whenever I do anything that requires the print head to move to the front. When the print head reaches the front the motor will keep turning and the timing belt will skip over the pulley, quite loudly.

I shut down the machine and moved the print head around manually, there doesn't seem to be any location where it jams or there's unusual friction. I tried resetting to the factory default, but that didn't solve the problem.

The one difference in "behavior" that I've noticed is that the UM2 no longer does the zeroing out procedure after printing or replacing the filament, the print head just remains at the front of the machine. I can't imagine what setting would cause this to happen which would remain that way after resetting the printer to factory settings.

I don't know how much damage the timing belts skipping over the pulleys causes, so for now I'm not trying anything else to avoid harm to the machine.

If anyone has any ideas, please let me know.

[stu_le_brew 42]

my first thought would be that one (or more) of the pulleys have come loose, you need to check all of them

[jhertzberg 19]

You should also check if your Y limit switch is damaged.

[dergoldstein 1]

I found the following post which not only had the same problem, but also (almost) the same cause:

https://ultimaker.com/en/community/15979-printer-head-cant-find-home

Except for me the wires of the Y axis were pinched by the feeder's motor. I've disassembled the feeder so often that it didn't occur to me that this would be the cause. Some type of filament or another either gets jammed, or the feeder starts grinding it. So the last time I re-attached it the Y limit switch's wires were clamped and shorted. This caused the UM2 to keep getting a positive read on the Y limit and think that the head was all the way to the back, all the time.

I cut out the crushed part of the wires and re-soldered them, that solved the problem.

[stu_le_brew 42]

glad you soted it out