RE: Tension pulley broken
Out of those two, ASA and PC Blend, I would say that PC Blend is probably stronger and more heat resistant, but I have no experience with it personally. My CORE One has been using ABS tension pulley parts for several weeks, and is working perfectly. I used 4 perimeters and 100% infill. ABS can evidently stand the tension force, and after an initial settling period (which I think is normal even with the original PC-CF parts) it is maintaining the correct belt tension perfectly. I expect ASA would be at least as good as ABS for this part, so I think you can use either of your filaments in this case.
If you do decide to just fit the supplied PC-CF parts, make sure you lubricate the tension screw threads, keeping the screw heads clean and dry. This will protect against the galling issue.
RE: Tension pulley broken
And check your belts where they feed through the pulls at the back, I discoverd my issue was I had one of the belt driving gears reversed and that's why I as having all the homing issues and why I had all the issues with tensioning that caused me to strip out the nut in the tensioner in the first place.
RE: Tension pulley broken
One of the motor pulleys is supposed to be reversed relative to each-other. That is, one has the pulley close to the motor, one away from the motor. Though it seems a lot of people just skim the detailed instructions here and mount both the same, missing the important detail.
And check your belts where they feed through the pulls at the back, I discoverd my issue was I had one of the belt driving gears reversed and that's why I as having all the homing issues and why I had all the issues with tensioning that caused me to strip out the nut in the tensioner in the first place.
RE: Tension pulley broken
Normally I do read the instructions and follow them exactly. My guess is that since I did the process over a few days, I likely got interrupted or was tired. I'll own up to my mistake though lol
RE: Tension pulley broken
Super easy to do, not judging at all - just making sure theyre now not the same orientation and anyone skimming rhe thread doesn't end up confused.
I had to disassemble and redo a couple things myself - just caught them during assembly.
RE: Tension pulley broken
yeah I learned a lot in the first upgrade. I have no doubt the second(still sitting in the box) will go better. I'm not in a rush to upgrade my 2nd mk4s. There's something nice about being able to just grab the printer and take it out of the enclosure to look at things, lube rods, etc. I'm going to miss that when I upgrade the 2nd one.
Super easy to do, not judging at all - just making sure theyre now not the same orientation and anyone skimming rhe thread doesn't end up confused.
I had to disassemble and redo a couple things myself - just caught them during assembly.
RE: Tension pulley broken
The other very common mistake people make is to improperly tighten the pulley set screws. Set screws must be tightened FLAT FIRST, then tighten the set screw on the round. The set screw on the round locks the ss on the flat in place.
If you tighten the ss on the round first, the set screw on the flat can wobble loose because it will not be perpendicular to the shaft flat.
RE: Tension pulley broken
Assembled my kit ~3 months ago and knew the tension mechanism was going to be the first thing to fail. Of course it did. Left side, galling.
What seemed like endless gantry squarings, belt tensioning procedure changes, experimenting to reduce VFAs and trying to reduce minutes of homing knocks finally did the screw and nut in. I'm sure the pully is under warranty, but I ordered a handful of pullies and sets of left and right tensioners along with a hardened nozzle and belts. Planning to be prepared for future failures of the mechanism.
My assembly was prior to the updated instructions for lubricating the screw. Will do that once the new parts are in. The screws always felt dry when adjusting.
Has anyone experienced any negative or positive changes in printing quality or tension stability after lubricating the screws? Lubrication might mitigate early seizure failures but wondering if this just creates a new episode of yet to be found troubles.
RE: Tension pulley broken
Has anyone experienced any negative or positive changes in printing quality or tension stability after lubricating the screws? Lubrication might mitigate early seizure failures but wondering if this just creates a new episode of yet to be found troubles.
It's almost never in stock, but having a roll of Prusa PC-CF handy for spare parts is good thing. I immediately printed spare pulley tensioners and ended up needing it when one of them seized. I also had to reprint the fan shroud when it collided with a spaghetti monster and melted against the hot end. I would recommend printing one of these: CORE One belt-tensioner-pulley which replaces the square nut with a brass heat set insert.
RE: Tension pulley broken
I have not experienced any issues with lubricating those screws. I'm still out on the core one upgrade. so much so that I"m considering not upgrading my second MK4S, even though the second kit is sitting here unopened. the first upgraded machine has been printing ok since the issues I had earlier in this thread. However, the fact there's no cold pull option on the core one when there is in both my xl and my mk4s is just annoying. I did a good deal of printing with some PETG-CF filament and I had a couple partial clogs in the core one. I had even switched to the non-HF obxidian nozzle. Thankfully that stuff I was printing in the PETG-CF is done and my next challenge is the ninjaflex and softer tpu in the core one. I have a pretty good profile going for both ninjflex and chinchilla on the MK4S and XL. The bogie updates to the extruder are awesome and I haven't yet once has a case where the tpu actually gets wrapped up in extruder. On the core one there is simply too much drag in the filament path to get proper extrusion for things like ninjaflex. Sainsmart(92 and 95a) works ok but I did a calibration cube last night and it was obvious it was struggling to pull the ninjaflex through the bowden tube on the core one. I print enough with tpu that I don't think I want to give up my solid working tpu printing on the other MK4S to upgrade it. I'm going to dig into some of the core one mods folks have done before I abandon upgrading the second printer. Back on topic, The lubricated screws, I think are imporant.
RE: Tension pulley broken
I lubricated the screws on my replacements with a drop of the ordinary Prusa grease, I have not needed to touch the belt tensioning since then, I have not noticed any creeping. I have been printing a gridfinity project lately exercising the printer more than usual.
/Anders
RE: Tension pulley broken
However, the fact there's no cold pull option on the core one when there is in both my xl and my mk4s is just annoying. I did a good deal of printing with some PETG-CF filament and I had a couple partial clogs in the core one.
The bogie updates to the extruder are awesome and I haven't yet once has a case where the tpu actually gets wrapped up in extruder. On the core one there is simply too much drag in the filament path to get proper extrusion for things like ninjaflex.
I'm going to dig into some of the core one mods folks have done before I abandon upgrading the second printer. Back on topic, The lubricated screws, I think are imporant.
Prusa added a cold pull option to the 6.4.0 firmware. I've been running 6.4.0-RC for 3 weeks and it's stable enough to use. There are some nagging bugs that need fixing though before the final release.
I agree the the bogie mod is worth the trouble. I've also modded the nextruder and side sensor to allow the softer TPU's to push through them. I still think it's easier though to remove the Bowden from the nextruder and just feed it in from the top. I've been working with Siraya Tech TPU Air which is a foaming filament and gets as low as approximately 65A.
I didn't even bother with lubricating the screws and went straight for the brass heat sets. Brass is self-lubricating and resists galling.
RE: Tension pulley broken
yeah as mentioned on the other thread, I'm hesitant to load up non-final firmware versions. I did see the cold pull stuff was in there so that's good. I'm definitely going spend some time to look at what other mods are out there for tpu. I hate how constrained everything feels in the core one. On the XL I played with having more inner diameter in the bowden tubes, but in the end I took out the ball bearings in the sensors on the side and that was enough. I don't use the side filament sensors at all on the XL. I may end up doing something similar on the core one.
RE:
I turn off the side-sensor, mount the TPU on the spool holder, remove the top, drape it over the side and feed directly into the nextruder. Not pretty but it works.
RE: Tension pulley broken
how does that look from the front when it's in operation and loaded?
RE:
how does that look from the front when it's in operation and loaded?
As in the photo I just hang the Bowden off to the side. I was thinking about a spool roller that fits on top similar to the one on the MK4 but this is actually easier (in my opinion). This is with both the bogie and filament sensor mods.
RE: Tension pulley broken
nice, I'll keep that in mind. sorry to have hijacked the thread again lol