RE:
Hello everyone,
It seems that it has happened to me too. I was printing a piece just now when I heard a ‘crack’ and saw the toothed belt slacken. It happened to me with the left tensioner when looking at the printer from the front.
I've attached a photo. My questions now are... What now? Do I have to pay €14 in shipping costs for an absurdly small part?
Regards
RE: Tension pulley broken
Tell people which area you are in, and ask if someone can print one for you.
Maybe a local hackerspace or maker space can make one.
STL's should be in the prusa 'Printables', printable parts for the core one
website
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility.Location Halifax UK
RE: Tension pulley broken
Someone posted a picture here of their temporary solution for this: they held the pulley onto the front rail using wire and managed to print a replacement. Not my idea, but I thought it was brilliant.
RE: Tension pulley broken
After I received my first roll of PC-CF, I printed spares of everything.
RE: Tension pulley broken
It's 100% essential to grease the tensioner threads and have the nut pushed in so it lines up with the hole. A touch of grease under the head is good too. Has to be Prusa grease or a plastic-safe grease. Stick to the new firmware's belt tensioner recommendations so the upper belt is around 98 Hz. Keep the X-axis perfectly square and let the lower belt frequency fall where it may, usually 91 Hz or so.
RE: Tension pulley broken
So many people have reported either broken tensioners or frozen screws that Prusa should consider redesigning this part. Maybe injection-molded glass-reinforced nylon with a brass heat insert. In the meantime, definitely lube your screws and buy some PC-CF and print some spares just in case.
RE:
It's 100% essential to grease the tensioner threads and have the nut pushed in so it lines up with the hole. A touch of grease under the head is good too. Has to be Prusa grease or a plastic-safe grease. Stick to the new firmware's belt tensioner recommendations so the upper belt is around 98 Hz. Keep the X-axis perfectly square and let the lower belt frequency fall where it may, usually 91 Hz or so.
All that is done as manual says, it was printing since 6 months ago, so it must be a design or material problem.
This part is getting all tension and forces from the belt in fast moves and of course when you tune the belt. In my opinion this piece should be made from metal or another material rather than PETG.
RE: Tension pulley broken
Got my kit 6 months ago and used the Prusa phone app for tuning. Belt slipped out on the first calibration so I re-assembled and tweaked the gantry and belt tensioning for about 2 months (on and off) as I struggled with printing artifacts. Tried the Spectroid app and found I was seriously over-tightened. Printing quality improved but I could never quite get it right. Left tensioner screw seized a month later due to the constant fiddling with tensions.
It was super-painful on the shipping cost but also got a belt set and a couple of other small items with the tensioner. Belt set was in case all of the tuning stretched them out. Never changed them so they're just backups. Along comes the instructions to grease the threads and the FW update for strobe tuning. No problems since then.
I did have a part printing option as a colleague with a Bambu PS2 prints regularly in carbon but didn't swallow my pride and ordered anyway. Also bought PC-CF locally and printed out spares if I'd ever need them. All has been good with the grease and have enjoyed printing PC-CF for unrelated parts as well.
I agree the pully tensioner and screw are a weak point, but the endless belt tuning just forces the issue. JoanTabb's suggestion is probably best for cost.
BTW, the colleague with the Bambu had multiple issues with ASA on his projects so I offered to print with my C1. No problems at all for me 🙂
RE: Tension pulley broken
If there were layer adhesion problems, I can see the tensioner breaking easily. That said, I've been doing some measurements on the Core One drive system, not for any particular reason, other than I enjoy that sort of thing. I believe the actual belt tension is about 2 kg. That doesn't seem like a lot, but maybe over time it takes its toll. As another touch point (no pun intended), it should take about 150 grams of force at the center of the front belt span to deflect it to the bearing rail. Any small spring scale that can push should do. Though it seems unlikely, in past work with vibrations and strobe lights I found it was possible to be fooled on integer multiples. If the belt were at 2X the desired frequency it could be excited by 1/2 that, and it would still look as expected at a strobe of 1/2 the frequency. I've seen talk of tight belts and have to wonder if something else is going on. Still, by Occam's Razor, the parts are likely defective.
RE: Tension pulley broken
Adding- if the belt tension is 2 kg, that has to balance on each side of a pulley, so the "pull" on the pulley tensioner is 4 kg, or 8.8 lbs where I live. Not insignificant.
RE:
got my MK4S to Core One + Kit yesterday , assembled until 6pm , core xy was not alligned , so started like described and what should I say ... Pully broken 🙁 ,
wondering if the "Upgrade" was a fault. , Yes screw was greased.
RE: Tension pulley broken
Wow, I don't have any CF material but I'm now thinking that printing up a couple tensioners with PETG might not be a bad idea just to have something in reserve.
RE: Tension pulley broken
Wow, I don't have any CF material but I'm now thinking that printing up a couple tensioners with PETG might not be a bad idea just to have something in reserve.
RE: Tension pulley broken
just ordered four ... just to be safe but this as the first "expirience" is annoying
RE: Tension pulley broken
I hate it when that happens. Prusa should redesign the part by either rotating the print layers 90 degrees or making the part out of a machined or injection-molded material, with a brass heat insert.
RE: Tension pulley broken
I hate it when that happens. Prusa should redesign the part by either rotating the print layers 90 degrees or making the part out of a machined or injection-molded material, with a brass heat insert.
RE: Tension pulley broken
I glued my broken pully with "super glue" .. and it is more relayble as the the orgiginal print 😉 ... not sure if my order of four of the "original ones" fixes my problems ..
I assume a broken and glued part is more usefull than a new one until the "broken as ordered", I hope we will get the problem fixed !! , I ordered 4 ! new pollys which will probably ... have the same quality issue !!!
RE: Tension pulley broken
to be fooled on integer multiples.
yes, there is no "guard rail"...
RE: Tension pulley broken
I just printed a couple in PETG, just to have in case one breaks. I couldn't remember much from the original build, but the ones I printed seem really stout and, if well fused, I can't imagine them breaking before lots of other things break. I did slice them with 20 or 25% gyroid infill. I'm no 3D filament expert but I've also been reading that carbon fiber, even though it can make things very stiff, can also have a detrimental effect on layer adhesion.
RE: Tension pulley broken
My questions now are... What now? Do I have to pay €14 in shipping costs for an absurdly small part?
Is your printer still under warranty? If you are based in Europe and bought as a consumer, it most likely is, since the statutory warranty (2 years) should still apply. In other regions it may be shorter. Given the multiple reports we see here, it clearly looks like a design or manufacturing issue, so Prusa should not ask you to prove that the flaw was not your fault.