RE: Tension pulley broken
Hey thanks for responding. I sent an email to prusa this morning and they responded back that they are going to send me the left and right tensioners(printed in PCCF) so it looks like I'll be shelving this for a couple days. But before I do I'm going look at your notes about squaring the gantry to see if I can do that with the PETG pieces in place while I wait for the pieces to arrive.
Stephen
This sounds like your gantry wasn't square before you started the belt tensioning process. Squaring it with belt tension alone is a bit of a kludge that is bound to result in improper tension.
With both belts completely loose you need to adjust the gantry so that there is no play on either side. Bring it to the front, and if there is a gap on one side, place a spacer item, slightly bigger than that gap, between the touching points on the OTHER side, then pull on the side that has the gap so as to bend the brackets that hold the x-rail to the y-rods. Remove the spacer item, recheck, repeat as necessary until both sides touch at the same time. Only then should you begin tensioning the belts.
Gantry to the front, print head to the right, tighten both belts in synchronisation, a little on one side then a little on the other, then measure their frequency. Aim to keep 6Hz difference in the measured frequency as you go, because eventually you want 98Hz on the top one and 92Hz on the bottom one. If you get to the point where a gap opens on one side you'll probably start to see that tightening one side either increases the tension on both belts, or neither. In that case it's simplest just to slacken them both off and start again, and this time go slower!
If you're in this thread I hope you've seen my Printables model for a tensioner pulley holder that uses a brass threaded insert in preference to the stainless steel square nut, to prevent the bolt seizing in the first place.
RE: Tension pulley broken
If you go with Prusa’s replacement parts, but a bit of lubricant on the tension screws before you insert them, to help prevent them seizing.
RE: Tension pulley broken
*put
RE: Tension pulley broken
I'll definitely keep that in mind.
So I just looked again. the left side has a about a 2mm gap when the right side is flush.
I tried stacking three(and then 4) of those universal wrenches in the right side and moving the left side forward, but it springs back to original position.
I definitely agree this is the problem.
If you go with Prusa’s replacement parts, but a bit of lubricant on the tension screws before you insert them, to help prevent them seizing.
RE: Tension pulley broken
ok, with your method I think I have it so it's square without any tension on the belts, in fact without the tension pulleys in place at all. So assuming I get the new parts in sometime next week, maybe I'll be good to go. Fingers crossed
RE: Tension pulley broken
As long as the belts are completely loose you can apply a bit more force than maybe feels comfortable, i.e. stack even more than the three wrenches if necessary.
RE: Tension pulley broken
Ah, our posts crossed. Good to hear.
RE: Tension pulley broken
What I ended up using was a 20mm xyz calibration cube I had. I definitely had some unease doing that bending but it seemed to get me where I needed to be. I'm just disappointed that the instructions don't make a bigger point of doing that alignment while you have the thing apart and the corners are easily accessible. taking the extruder back off multiple times is annoying.
I've had these two smaller printers since they were MK3 lol. Up until this time it's been pretty fun doing the upgrade from one model to the next. The XL, that one I ordered fully assembled since the building of that seemed a little daunting. I'm curious when there's going to be an XL plus upgrade
RE: Tension pulley broken
I'd like to report that Chris's modified pulley (V2) and Prusa's new belt tuning procedure closed the issue for me (for now). I've managed to tuner the belts within the new parameters and achieve both carriages contact, which means that my gantry was square to begin with.
I will monitor this setup.
BTW: Your door handle will probably fail. Use the two screw holes with M3x6 bolts and self b re asking nut for more permanent solution.
I will now proceed to make the enclosure loose less heat, and I also have all the parts required for the HT hotend mod, except for those newfangled connectors.
P.S. My colleague seats on the HT90, and he didn't even manage to take it of the pallet for 6 months. I asked him politely to give it to me. No luck for now... 🙁
RE: Tension pulley broken
So this is a somewhat questionable weak link. I kind of think a problem with the belt tensioner was causing my C1 to start throwing layer shifts. Went to adjust the belt tension after the last layer shift incident. The bolt has somehow crossthreaded the crappy square nut. With nut spinning inside the tensioner as a result. Had quite an adventure getting it out. Melted a thread insert into it and knock on wood.
I will attempt to make a few emergency spares from material I have at hand, while trying my best to justify shipping a new 3.99€ part for 15.90€.
RE: Tension pulley broken
@chris your mod to the tension pulley is a godsend. Thank you. The amount of stress that the tension between the M3S nut and CAP screw is a real weak point.
Your solution using a threaded insert spreads the load over a greater surface area of threads. It's great.
RE: Tension pulley broken
Next time prusa has some PCCF in stock I'm going to get a roll so I can make some spares. Will probably make some of chris' modded ones. For now I just got the dhl confirmation that prusa is sending me left and right tensioner+pulleys so I hope to have this first upgrade done soon. I'm going to be extra careful with the second one. I'm going to make sure things are square as soon as possible in the build to make sure that by the time I get to the end I don't have this problem again. I miss the simplicity of the MK4S!
RE: Tension pulley broken
I made both the stock ones and the modded ones as potential spares.
RE: Tension pulley broken
[...] trying my best to justify shipping a new 3.99€ part for 15.90€.
Prusa should provide replacement tensioners for free -- and to my knowledge have done so when users requested it via the support chat. The part fails prematurely due to a flawed design. (Short thread with large tolerances, high tilting force on the nut due to the lateral offset of the belt idler.)
If you end up spending money, I think it would be better spent on some PCCF filament to print your own tensioner blocks -- and print Chris' version optimized for heat inserts, https://www.printables.com/model/1360563-core-one-belt-tensioner-pulley-to-take-a-threaded/
RE:
[...] trying my best to justify shipping a new 3.99€ part for 15.90€.
Prusa should provide replacement tensioners for free -- and to my knowledge have done so when users requested it via the support chat. The part fails prematurely due to a flawed design. (Short thread with large tolerances, high tilting force on the nut due to the lateral offset of the belt idler.)
If you end up spending money, I think it would be better spent on some PCCF filament to print your own tensioner blocks -- and print Chris' version optimized for heat inserts, https://www.printables.com/model/1360563-core-one-belt-tensioner-pulley-to-take-a-threaded/
Yep they shipped mine for free. I 100% wouldn't pay for a replacement which has basically designed to fail.
I really want some PCCF but can't really justify the price.
Does anyone know if ABS-GF is a suitable replacement for the PCCF parts? I want to modify one of the existing PCCF parts but I only really have ASA, PETG-CF and ABS-GF to hand.
RE: Tension pulley broken
Yep they shipped mine for free. I 100% wouldn't pay for a replacement which has basically designed to fail.
I really want some PCCF but can't really justify the price.Does anyone know if ABS-GF is a suitable replacement for the PCCF parts? I want to modify one of the existing PCCF parts but I only really have ASA, PETG-CF and ABS-GF to hand.
Good question, and I hope someone who knows about these things will give us an answer.
For an empirical approach, this morning I've swapped my PC-CF tensioners for a couple of threaded insert parts that I printed in plain ABS (Overture white), with 6 perimeters and 100% infill, just to see how they hold up longer term. After the first print (ABS) the belts have loosened, but then they always do that with the PC-CF parts in my experience, so it's too soon to tell. I'll tighten them up and then monitor them over the course of a few more 'hot' prints.
RE: Tension pulley broken
prusa should have just opted to make these metal parts given how much tension they are handling. Heck they did it with the rod holders.
RE: Tension pulley broken
prusa should have just opted to make these metal parts given how much tension they are handling. Heck they did it with the rod holders.
CORE One S (probably 🤣 ).
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.
RE: Tension pulley broken
sure.... just like I'm waiting for the XLS lol
I was one of the original orders of the XL 5h. After I got it I had to take the ball bearings out of the filament sensors because they created too much drag when printing tpu. Still waiting on them to release an update to the XL for stuff like that. Overall though the XL, after a few firmware updates, isn't bad. I think the filament sensor design on the coreone seems way better than what's in the XL.
I may leave my second upgrade kit uninstalled for a while until this core one proves itself out(or not). At least I still have two working printers.
CORE One S (probably 🤣 ).