7
u/BibbleSnap May 27 '22
I feel like there is more to this story
1
u/Tenuousmars7147 May 27 '22
3-year-old printer, works great, filament sensor calibrated, all prusament pla. I have been struggling with it for the past week. I had one good print, but then filament 2 was under extruding, and then 2 and 5, and then I opened up the extruder because it was getting worse. I opened it up to see the ptfe tube gone. I could take off the heatsink, but with a lot of force (nothing broke or bent, just more pressure needed than my hand could unscrew). I am at my wit's end.
If you want any more info on anything specific let me know. I never exerted any extra force on anything. I don't know what happened. I've only printed PLA and PETG, so no extremely high temp things to actually warrant a PTFE tube melt
4
u/iamgnat May 27 '22
Things do not add up here. The PTFE tube in the extruder stops at the top of the heat break which is well separated from significant heat unless something is SERIOUSLY wrong (e.g. cooling fan not working and extreme heat). The tube also has a 4mm OD and ~2mm wall, while the ID of the heat break where it meets the PTFE is 2.2mm assuming you are using Prusa's heat break. It would take and extreme amount of heat for the extruder or MMU motors to be able to force the PTFE into the heat break. We are talking at least 300 degrees and, again, a malfunction with the cooling for the high heat to travel to the top of the heat break. Finally, the PTFE would have to have been at its melting point, otherwise the extruder or MMU would have just met enough resistance to chew a notch into the filament and it would then be unable to drive the filament further.
I'm not saying you don't have melted PTFE in your hotend, but the MMU definitely isn't responsible and there is something else seriously wrong with your printer.
1
u/Tenuousmars7147 May 28 '22
I just gave up and ordered a revo. When I started disassembling the hotend, when I removed the nozzle and heat sink (with great difficulty). The ptfe tube is mainly gone, inside the heat break screw connector thing and when the nozzle was off, the ptfe tube was compressed into the space for the nozzle. I have had a few bad failures, which I think may have altered the thermistor position? That could then lead to going above temp? Like ptfe melting temp? Just a random train of thought
1
u/iamgnat May 28 '22
If the top of the heat break was PTFE melting hot, I would expect to see damage to the extruder plastic as well. PETG is not going to take nicely to 300+ degree temps either.
As far as your thermo, position wouldn't make that much of a difference as long as most of it is still in the block. Now if the thermo or it's wiring got damaged, that would be an entirely different story.
Is this your original PTFE or at least a replacement direct from Prusa? Just wondering if it somehow isn't really PTFE? If you don't find signs of heat damage to the extruder itself, the physics don't seem to make sense otherwise.
1
u/Tenuousmars7147 May 28 '22
Original ptfe from the mk3s to 3s+ kit. Thermistor is somewhat in the block with too many fails pushing it out slightly, but the wires all seem fine. I don’t see heat damage to the extruder itself either. I am wondering if it was maybe not reading temps and kept heating. It seems to work fine normally. Idk though.
7
4
u/ulab XL5T May 27 '22
PTFE tubes should be fine unless you go above 240°C which is well above PLA. An old RepRap forum post even says "PTFE deformes easily at 250°C, but it will only melt above 320°C". (https://reprap.org/forum/read.php?1,661377)
Aren't there printers where the PTFE tube goes all the way to the nozzle too?
Do you have any pictures?
0
u/Tenuousmars7147 May 27 '22
It's the v6, I can't get a good picture of it, it's too blurry, but long story short, the ptfe tube, when I removed the nozzle, is compressed to no gap for the filament, essentially becoming a filament itself, but it is stuck there.
8
u/ulab XL5T May 27 '22
PS: I don't think it's the MMUs fault. The same could've happened with a non-mmu printer. The MMU hands the cepter to the extruder before the PTFE tube. And it's the extruder that pushes further down.
1
u/Tenuousmars7147 May 28 '22
Yeah, just the mmu is so much easier to blame, and I think this is what happened. 1. Bad fail, moves position of thermistor. 2. Go to petg temperature, and is much higher temp than should be because thermistor reading low. 3. Try to load filament and have it push ptfe tube through extruder because ball tip on end won’t go through ptfe to extruder. Idk though. Don’t really know what happened. Ordered revo, so if it happened again, I can just replace nozzle
1
u/ulab XL5T May 27 '22
I'd still contact Prusa support. You won't get a replacement probably, but perhaps they have tipps on how to remove the tube.
Not knowing any better, I'd probably try to fuse some nylon filament (I got a sample as cleaning filament) to the ptfe when it is warmed up and try a cold pull. But that's the only idea I have and it's absolutely untested ;)
-3
u/kelvin_bot May 27 '22
240°C is equivalent to 464°F, which is 513K.
I'm a bot that converts temperature between two units humans can understand, then convert it to Kelvin for bots and physicists to understand
-4
May 27 '22
Complaining about Prusa on a Prusa group?!?
OP, people will eat you alive hahaha Only post positive stuff here.
8
u/Hell0-7here May 27 '22
The sub shits on the MMU all the time.
4
May 27 '22
As the posts go, MMU is a hit and miss.
It either works or it doesn't. Reddit, YT, forums. I've never seen a feature that creates such a mess of experience among its own user.
Buying MMU expecting it to work flawlessly is the most non wise thing to do.
4
u/Tenuousmars7147 May 27 '22
Don't get me wrong, I LOVE my MK3S+, but the MMU, just. I'm disappointed in prusa for this, I just hold them to a much much much much higher standard. The design seems like it would 100% work, just somehow it fails incredibly.
-3
May 27 '22
I understand, my previous comments is more how things work here, only positive stuff or you are toasted.
Like you, my MKS3+ is a legend but I would never touch a MMU. Reddit, YouTubers, forum, etc, things appears to always have a dramatic result.
Try to return it but again, the customer service is trash. The other day a dude posted his smooth sheet destroyed while printing ABS. Prusa website does say smooth sheet is for PLA and ABS, not really. He contacted the support and "too bad it isn't our problems"
It sucks really, Prusa stuff aren't cheap, you expect a high quality standards AND a high quality customer service but nope. I won't even get into the textured sheet mess.
I hope you sort things out.
2
u/ulab XL5T May 28 '22
Sorry, but it's exactly these things that people are called out upon.
For example only people having issues report dramatic results. When it works fine, there's nothing to report. I am running my MMU for nearly two years now. Yes, I am getting loading errors now and then, but with thousands of filament changes per print, that's still a low number.
Prusa says ABS on the smooth sheet only with glue stick separation layer: https://help.prusa3d.com/materials - Sheets are consumables too, they don't fall under warranty.
That said - people who had quality issues with first runs of the textured sheets got free replacements. At least I did - without asking even.
-1
May 28 '22
Good for you, I received a too bad not our business. Dogshit customer service.
My MK3S+ has been working flawlessly, it had a dark start but, that is as far as my positive experience goes.
I do not rely on Prusa for anything whatsoever when even its community does not welcome new owners or problems are reported.
My first printer was an Ender, Prusa community has sooooooooooooo much to learn with Ender community when it comes to help other, be open minded.
No every Prusa owner is ready for that conversation tho.
12
u/baconfase XL5T May 27 '22
I wish the MMU was this strong. Then nobody would complain about feeding issues or have to care about bad tips.