RE: Tension pulley broken
I think some of this could be helped if they had users focus on the gantry alignment early on prior to the belt tensioning steps. The same thing happened to me. My parts should be here on thurs.
This happened to me at the assemble Core X-Y stage... I was attempting pre-tensioning on the bench, then the nuts started spinning. Cut the heads off, hogged out the square nuts. Threaded in some 8-32 allen screws to be able to continue the assembly... Prusa support is sending replacements.
RE: Tension pulley broken
This happened to me at the assemble Core X-Y stage... I was attempting pre-tensioning on the bench, then the nuts started spinning. Cut the heads off, hogged out the square nuts. Threaded in some 8-32 allen screws to be able to continue the assembly... Prusa support is sending replacements.
Welcome to a not so exclusive club. LOL
RE: Tension pulley broken
I've just updated my threaded insert model with a version for the screw-in inserts that now prints the threaded section more cleanly.
https://www.printables.com/model/1360563-core-one-belt-tensioner-pulley-to-take-a-threaded
This is one of the two I printed in plain ABS, for longer term testing.
RE: Tension pulley broken
Chris I like the definition of galling on your page haha. Funny how the noun leads to the adjective haha
Since I don't have hardened nozzles on my printers anymore I probably won't be trying to print the PCCF, even if I could my hands on the prusament pccf. I'm going to try to use the prusa-supplied ones when I get them, but I'm quite interested to see what your test results end up being. I do have some spools of abs and asa I could print with if that ends up working. I put myself to be notified when the prusa pccf is back in stock but who knows when that will be.
RE: Tension pulley broken
Yeah, I signed up for notifications too, but I saw a message on Reddit to say it was in stock and nabbed a roll ASAP. Then it went out of stock again very quickly. I never did receive an alert.
It's always in short supply, because it's lovely stuff, but I have visions of hundreds of rolls sitting on people's shelves with only enough for a couple of tensioners ever being used 🙂
RE: Tension pulley broken
they may be breaking into their own stash reprinting these things for folks... She should have just done them in metal and upped the price of the upgrade kits.
RE: Tension pulley broken
I can think of another case where carbon fiber was used where it should have been metal...
https://en.wikipedia.org/wiki/Titan_submersible_implosion
lol
*POP* *POP* *POP* *BOOM*
RE: Tension pulley broken
I think some of this could be helped if they had users focus on the gantry alignment early on prior to the belt tensioning steps.
No, I don't see how this could have anything do to with a not-quite-squared gantry. The idler in the belt tensioner is laterally displaced vs. the screw & nut, so there is always a major tilting moment acting on the nut. Whether your gantry alignment is perfect or a couple of degrees off has nothing to do with it.
I also don't think the tensioner blocks should necessarily be metal. The PCCF holds up just fine to the belt tension. It's the nut getting locked to the screw which causes the problem. Using different metal for the nut to avoid the galling, longer threads to better resist the tilt, or a different tensioner geometry without the lateral displacement are the proper cures in my opinion. (But the different geometry would require reducing the Y travel range a bit, so that's unlikely to be implemented.)
RE: Tension pulley broken
I agree about the galling, but with the pccf snapping on the pully, that's a part strength issue it would seem. I 100% agree that spreading the stress across more threads would help.
RE: Tension pulley broken
I agree about the galling, but with the pccf snapping on the pully, that's a part strength issue it would seem. I 100% agree that spreading the stress across more threads would help.
I must have overlooked the "PCCF snapping on the pulley" bit. Who reported that? I have only seen reports where the galled nut was forced to spin within the PCCF block, and hence ate away the material around it.
RE: Tension pulley broken
it has happened to me but someone posted pictures a few replies back. Mine happned when I was trying to get the gantry square.
RE:
Hmm, I only see "the nuts started spinning" (in the PCCF part) pictures above.
RE: Tension pulley broken
They recommend me to reprint it in asa/abs or PC. Guess they ran out of parts to send out by now... My path to core one was mk4s kit -> conversion kit. Maybe we're more in the "suit yourself" bracket of users?
However I ordered a roll of PCCF off of amazon and will make a few spares. I wonder what more spares I should have print. What will be the next weak link?
"my recommendation" support says. Yeah, you'll see my recommendation soon enough.
I get it, it's the first iteration of a new printer platform unlike the i3 which has been worked upon for a decade or more. But things like this almost throws me back to my ender 3 v2 days.
RE: Tension pulley broken
The plastic part isn't the problem. A metal part (unless in a specifically "self-lubricating" bronze or so) won't do more than keep the nut from spinning and make it harder to repair (or at least harder to destructively disassemble).
The high tension on relatively small threads, narrow nut (so low surface area for that stress) and specific material pairing without any appropriate mitigation for galling are the issues. Anti-seize is easy to source and might be enough; the threaded insert solution is also promising.
One of the weird engineering problems is that over-engineering doesn't solve problems; it just changes where they surface. So make a cheap, easy to replace part so it can't break and suddenly expensive, hard to replace parts might break instead. And as an example, I really don't want a metal part to gall/seize up and need to be replaced.
RE: Tension pulley broken
Problem is a 3.99€ part is 15.90€ shipping. It's just never going to happen.
RE: Tension pulley broken
How do Vorons etc deal with belt tensioning? Is it a similar approach to Prusa ?
RE: Tension pulley broken
fair points.
The plastic part isn't the problem. A metal part (unless in a specifically "self-lubricating" bronze or so) won't do more than keep the nut from spinning and make it harder to repair (or at least harder to destructively disassemble).
The high tension on relatively small threads, narrow nut (so low surface area for that stress) and specific material pairing without any appropriate mitigation for galling are the issues. Anti-seize is easy to source and might be enough; the threaded insert solution is also promising.
One of the weird engineering problems is that over-engineering doesn't solve problems; it just changes where they surface. So make a cheap, easy to replace part so it can't break and suddenly expensive, hard to replace parts might break instead. And as an example, I really don't want a metal part to gall/seize up and need to be replaced.
RE: Tension pulley broken
I wonder if a design where the tension pulleys push rather than pull would minimise the galling problem?
RE: Tension pulley broken
I can think of another case where carbon fiber was used where it should have been metal...
https://en.wikipedia.org/wiki/Titan_submersible_implosion
lol
*POP* *POP* *POP* *BOOM*
There's nothing funny about people losing their lives.
RE: Tension pulley broken
I can think of another case where carbon fiber was used where it should have been metal...
https://en.wikipedia.org/wiki/Titan_submersible_implosion
lol
*POP* *POP* *POP* *BOOM*
Much as I’d love to, having just watched the Netflix documentary, I’m going to resist the temptation to take this discussion way off topic 🤣
I think the difference here is that CF is likely overkill in our application - its stiffness is its main benefit for maintaining belt tension, rather than its outright tensile strength. I already know that ABS can withstand the tension, but will it retain its shape, and hence the belt tension, after a few hours of 55 degrees chamber temperature?
I’ll have some idea by the morning.