Best way to tackle repairing CoreXY belts?
Hey all,
Like many of you, I finished my upgrade from a MK4S and encountered the Y-axis belt failure. I found the left side had a bit of play, but when I fiddled with the tensioning, the top seemed like it had too much tension, and the bottom seemed like it had too little. I'm pretty sure I've got my pulleys in the right orientation, but it's hard to tell for sure. I'm thinking that the issue might be me not getting 4-5 teeth sticking out of each side.
I'm not sure what the best way to fix this is. Maybe getting just the extruder off will let me try to reattach the belts, but if a pulley is upside down, do I need to take the whole CoreXY assembly off? Is there a guide to how to tackle that? I just finished putting this thing together, and I really don't want to disassemble it more than I have to.
Also, any other hints as to what might be wrong with my Y-Axis would be most welcome. There's no calibration message, just some clanking around in the front right corner, and then an X. Also, it had like a 1/5 chance of passing, and if it does, the X-axis test also fails.
RE: Best way to tackle repairing CoreXY belts?
To reattach belts to the carriage see the Extensive adjustment section here. But first fully loosen the tensioners on both sides. You will then be able to inspect pulleys in the tensioners, if that's what you want. Make sure that left tensioner is using the M3X18 screw to attach the pulley (I had accidentally used M3X12).
Be careful with the tensioners, some people had issues with square M3 nuts starting to rotate inside the part and therefore destroying it. Though I had no such issues.
RE: Best way to tackle repairing CoreXY belts?
P.S. Also I recommend removing the top panel; it's only 4 plastic rivets. You can push on the pin in the rivets from the inside with your finger to carefully remove them.
RE: Best way to tackle repairing CoreXY belts?
Thanks so much! I feel dumb: when the tensioning part helped, I panicked a bit, and it did not occur to me to read the "extensive adjustment" section. Very nice to have a step by step guide.
RE: Best way to tackle repairing CoreXY belts?
It's a bit unclear to me what situation you encountered while trying to adjust the belt tension. When you write "the top seemed like it had too much tension, and the bottom seemed like it had too little" -- was that after you relaxed the left (top) belt tensioner all the way, and tightened the right (bottom) tensioner all the way?
To check whether you have installed the motor pulleys correctly, look at them through the hexagonal openings on the inner side of the motor mounting blocks. The toothed pulley and belt are a bit hard to see, but you can easily see the smooth section of the pulley with the black grub screw, especially when you move the print head by hand a bit. The left motor drives the upper belt, so you should see the smooth end of the pulley (with the grub screw) at the bottom. For the right motor, the belt-driving toothed section of the pulley is at the bottom and the smooth section & grub screw on top.