Hotend PTFE tube length
Hello,
after doing the upgrade from MK3 to MK3S (together with MMU2) I had no problems with the extruder for about 2 month. After that time I''ve got a scratching noise from the extruder. Sometimes only when filament wasn't loaded 'til to the extruder, sometimes also when the filament was transported through the extruder. After examining the extruder I found that the hotend PTFE tube sticks out from the printed parts of the extruder an is very close to the extruder gear.
I then started to disassemble the whole extruder and pulled out the PTFE tube from the hotend and reseated it (conical side into hotend). I put a clip under the black plastic collet to prevent it from releasing the tube. When I checked the length of the tube sticking out from the hotend it seemed to be flush with the printed parts. But after completely assembling the extruder the situations is as before with the tube extremly close to the extruder gear.
I wonder wheter there is an exact measurement for the length of the PTFE tube sticking out from the hotend?
At the moment I hope that I don't have to disassemble the hotend?
Thanks in advance for any suggestion.
Rainer
RE: Hotend PTFE tube length
Hi Rainer,
yes, there is information online. You can order the part from Prusa
https://shop.prusa3d.com/de/ersatzteile/929-ptfe-mk3smk25smmu2s-hotend.html (need to be logged in I would assume)
and they have information on what to do when the tube is damaged and how to cut on yourself:
https://manual.prusa3d.com/Guide/How+to+trim+PTFE+tube+-+Original+Prusa+i3+printers/500?lang=en
Hope that helps
RE: Hotend PTFE tube length
Hello Time,
thank you for posting the information with the links. Essentially I think the tube itself is not damaged. The upper end shows minimal wear. I am more concernd about melted and hardened filament inside the hotend that has occupied the empty space the tube left when moving upwards during printing. I am afraid that I can't push a tube deep enough into the hotend, whether it's the old one or a new one.
Rainer
RE: Hotend PTFE tube length
I am not quite sure if that is actually your problem. For that to happen you would need to have molten plastic all the way up beyond your heatbreak and in your heatsink. Molten plastic should typically solidify in the cold part of your heatbreak and lead to clogging if it gets there.
Good thing is that you can easily check your assumption by disassembling the heatbreak and visually checking for plastic in the heatsink. You might eben be able to remove it from there.
From the picture you posted it is hard to tell, but the ptfe tube does not look dramatically high up to me. Are you running into any issues with the positioning of the tube you have right now?
RE: Hotend PTFE tube length
Hello timo,
Thanks for your reply. Beside the noise from the extruder, that has started some time after the MMU2 + MK3S upgrade , I have no issues that I can directly tie to the PTFE tube.
But I had a two and a half month with a lot of troubles with the MMU for various reasons (FINDA, IR Sensor, loose PTFE tube between buffer and MMU ...). Kind of a steep learning curve. At the moment every little noise make me kind of panic. All the problems mentioned above plus the struggle to find right temperatures to prevent filament jamming in the PTFE tube led to a lot of filament load failures. So I would feel better without any unusal noise.