Significant stretch of the Y-Axis Belt - Shoild I replace?
Hi
Just come back to a print disaster on my MK4 (not Mk4s). Something went wrong, suspect bad bed adhesion and a large ball of PLA and strands were everywhere.
Tidied it all up and then found the Y-Axis wouldn't home as there was debris around the Y-Axis motor pulley, so tidied that up and then noticed that the Y-Axis belt was really, really lose. Possible 2-3cm of movement. I have another MK4 and that belt is tight. There was no way it would set itself up with homing.
Turned the Mk4 over and the belts are attached using the method in the picture ((which I have shamelessly stolen from the Prusa site).
The two belt attachments are tight together and there is no ability to tighten them anymore.
As these are tightened up as much as can be and the belt tensioners are tightened up as much as can be, I have come to the conclusion that the belt must be stretched (quite considerably) and that therefore it's useless. I can't see how they can be accurate if I cut them down by a few notches but I'm happy to be told thats nonsense and just cut a couple of notches off and tighten them all up again. There is no way I can tighten the belts without cutting off some notches as far as I can tell.
Is this a fair conclusion to come to?
I think these are 6mm GT2 belts and are fairly cheap for 5m of belt, circa £6 from Amazon.
Is there a better solution here please? Not looking for someone to do the work, just a second opinion would be nice 🙂 Also what are the hidden screws underneath the attachments for please? I'm assuming to lock the belt ends in.
Many thanks
Rob
RE: Significant stretch of the Y-Axis Belt - Shoild I replace?
I haven't had my belt stretch, but it did start to pull out. Make sure the belts are in all the way. If they are not engaged deep enough the belt will be too long.
If that is the original PETG part, Prusa has upgraded it to PC-CF on the MK4S. Those running high heat materials found the Y axis mount fails. It tends to let the belt slip out or the mount comes loose when the PETG softened.
The Y axis mount is what stops Y when homming against the Y motor mount. With only 1 screw it can get knocked loose after a while. That is what happened to me and led to this MOD. https://www.printables.com/model/727247-y-belt-holder-one-piece-mod-for-mk4 Along with a new Y axis Tensioner listed in the Mod it works well for me. A little lock-tite or similar on the screws also helps to keep them tight.
That is the MK3S mount in the picture.
RE: Significant stretch of the Y-Axis Belt - Shoild I replace?
Hi
Thanks for the reply.
Both ends of the belt were tight into the end holders and the belt was slack. I could pull it up by 2-3cm which surprised me. The MK4 has been fine (at least for the Y-Axis belt) since I received it fully assembled last year.
I can't tell if the two end parts are PETG or not to be honest. I don't run that much PETG (if the part is PETG), mostly PLA+ with a plate temp of 60C normally. It didn't look like the belt had slipped out. The bolts were all tight and the two ends of the belt holder were tight against each other, so I don't think any bolt had come loose. Wish it had 🙂
I can see there are various mods for the Y-Axis end holders and Y-Axis tensioners, I may end up having to use that mod. It moves the tensioning action to the end and where it is easily accessible rather than under the plate which is a PITA to access.
I'll take off the Y-Axis belt and measure it. I think it's supposed to be 650mm.
It looks to me that I need a new belt and 5M is turning up tomorrow. I'll use the other MK4 to print the mods up and fit them instead of the factory supplied parts.
Rob