Blockage near cold end of hotend
Hi
I had a failed print on my Prusa i3 MK2s where there was a mass of filament stuck to the nozzle afterwords (reminded me of an HP Lovecraft creation).
When I got the filament off the head (mostly) and tried to feed in filament, it was clear the nozzle was partially blocked as the filament only came out slowly and curled up onto the nozzle. I unloaded the filament and when I tried to load more, it only feeds about 4 cm then stops.
I've tried clearing the nozzle using those thin needles designed for the task through the bottom without luck. I can't do a cold pull as I can't get the filament in far enough. I even have a tiny allen key I sometimes use to push down blockages and this also stops dead at around 4cm in.
Question, is there any way to clear this without having to completely disassemble the extruder and hotend (and remove all the cable ties)? That seems like such a bad design decision.
Thanks
Re: Blockage near cold end of hotend
if you're very careful, you get the nozzle off just by removing the fan shroud. if you want to get the block off OR check the heatbrake or ptfe tube, then you'll need to remove the noctua fan, the blower fan, and 3-4 bolts behind it for the plate holding the heatsink in.
edit: just realized you said mk2. this is the mk3 forum, but procedure should be similar
Re: Blockage near cold end of hotend
Thanks. Sorry, I hadn't noticed I had posted it to the wrong forum. OP, can this be moved to the correct forum?
I've removed all the fans but it doesn't look like I can get to the ptfe tube without removing all the cable ties and the full assembly.
Re: Blockage near cold end of hotend
Moved as requested
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Blockage near cold end of hotend
Thanks Peter.
Re: Blockage near cold end of hotend
It's been a while since I disassembled the extruder on a Mk2. But you certainly don't need to remove any cable ties. From memory:
After you remove the front fan (and nozzle) and the front 2 screws of the extruder fan, you remove the 2 (?) long screws in the front extruder housing and remove that part. The extruder is now accessible and can be removed with a forward and leftward movement, leaving the extruder hanging on the cables (don't worry, they will take the weight).
You should then be able to unscrew the heat sink from the heat break. But it may well be very tight, due to an excess of hardened thermal paste.
Once you have done that, push down the black ring at the top and the PTFE tube should push down, through the heat sink - don't try to pull it up as you will deform the PTFE and the lock ring may also lift.
If you need to go further, you can heat the block and remove the nozzle and then the heat break from the block.
Re-assembly is much the same, but there are a few extra things needed. I suggest that you disassemble only as much as necessary, fox your blockage and then post again.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Blockage near cold end of hotend
Thanks for the detailed description Peter, I will see if I can follow this tomorrow.
I'm pretty sure I removed the three screws in the back holding the extruder but nothing would move because all the cables are tied together right behind the extruder bracket.
Re: Blockage near cold end of hotend
https://manual.prusa3d.com/Guide/5.+Extruder+Assembly/295?lang=en#s4978
Step7, remove the 2 screws at the front (blue & green arrows in the picture). Make sure you know which is from each hole; they are different lengths.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Blockage near cold end of hotend
I have already removed those. However, the hotend is still firmly embedded and will not move because the ptfe lining at the top is inside the plastic enclosure.
Re: Blockage near cold end of hotend
OK, the extruder should come out fairly easily.
However, there is something else you can do (which I do with the Mk3) and that is to unscrew the heat sink from the heat break in situ.
You need to get the lower end of the extruder out just a little; with a spanner on the heat block and pliers on the heat sink, you should be able to unscrew the heat sink.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Blockage near cold end of hotend
Thanks Peter. I'll give that a go. I appreciate the patience and support.
Stephen
Re: Blockage near cold end of hotend
No matter what I tried this would not let me release the hotend without cutting all the cable ties on the back.
After doing that, it appears the PTFE is jammed solid into the top of the cold-end. Even when heated to 255C and with the black ring depressed it will not budge. I can only assume it has melted and expanded.
I've had to order a new E3D V6 hotend heatsink and heatbreak 🙁
Re: Blockage near cold end of hotend
No matter what I tried this would not let me release the hotend without cutting all the cable ties on the back.
After doing that, it appears the PTFE is jammed solid into the top of the cold-end. Even when heated to 255C and with the black ring depressed it will not budge. I can only assume it has melted and expanded.
I've had to order a new E3D V6 hotend heatsink and heatbreak 🙁
OK, that's the simple way. Do you have some spare PTFE tubing?
When you put it back together, make sure that you follow the instructions precisely. If you need any help, ask in advance!
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Blockage near cold end of hotend
Thanks Peter.
I've bought some of the Capricorn Bowden tubing from e3d as I plan to replace the bowden tubes on my AnyCubic printers. Hopefully this will do the job for the hotend too.
Re: Blockage near cold end of hotend
Yeah. I tried Capricorn tuning; works the same as regular PTFE (I didn't see any benefit).
Just ensure that you chamfer and taper the lower end and taper the upper end.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Blockage near cold end of hotend
I
keep having the same issue with a brand new kit … I keep getting filament jammed in the cold end of the hotend… its happened to me three times in a row ...what would cause this? I haven't even printed anything.. it keeps getting stuck going through setup of live z adjust. I ordered a brand new hotend assembly because I broke the thermistor …. I reassembled the whole assembly with a new the new hot end and the same thing has happened again... 👿 I don't understand... everything looks aligned with the extruder gear and the entry to the whole of the pfte tube.. the pictures above are from the old assembly