[Solved] Hotend not heating about 140C  

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lars-2
(@lars-2)
Active Member

I recently ran out of filament mid-print on my otherwise fantastic mk3s, and rather than it automatically unloading or me adding more filament, the filament just got stuck in there. I tried to push it through with various tools, to no avail, including (after seeing that advice on this forum) after removing the nozzle. Finally I disassembled the mount enough to get the hotend out (which I have to say is pretty easy, good design there), unscrewed the heatsink (with heatbreak because I couldn't find a way to avoid that), and baked that in the oven until I could remove the filament and PTFE tube. I added a spare tube and put in a fresh nozzle, but now it won't heat over about 140C. It starts out heating at normal rate, but slows down when it gets close to 100C and asymptotically approaches 140C (ca.).

I've checked that

- Thermistor and heater resistance are OK

- Thermistor readout is appropriate at low temperature

- Hotend doesn't seem to become very hot - tried holding some PLA to it, it deformed slowly, didn't melt

- Heater voltage from board is OK

- Selftest runs OK

Any thoughts on what could cause these symptoms? I suspect that removing the nozzle and then heating up the assembly could have caused PLA to go places it shouldn't. Alternatively, the heater insert came loose while I was working on it? Any tests you can suggest before I go to the trouble of replacing the entire hotend, possibly including wiring?

Here's what the heater currently looks like:

If it is useful, I can take macros shots of it. I just want my workhorse printer back in action! *sniff*

 

Thanks,

-Lars

Best Answer by lars-2:

For future people facing this issue: Unscrewing the nozzle and heatbreak from the heater block and assembling them in the way described in the manual - nozzle first, turning it back from fully screwed in by 1/4 - 1/2 turn, then heatbreak - solved this problem. Now witness the power of this fully armed and operational 0.8mm nozzle!

-Lars

Posted : 04/05/2020 8:37 pm
lars-2
(@lars-2)
Active Member

Here are some macro shots:

Posted : 04/05/2020 10:30 pm
lars-2
(@lars-2)
Active Member

For future people facing this issue: Unscrewing the nozzle and heatbreak from the heater block and assembling them in the way described in the manual - nozzle first, turning it back from fully screwed in by 1/4 - 1/2 turn, then heatbreak - solved this problem. Now witness the power of this fully armed and operational 0.8mm nozzle!

-Lars

Posted : 06/05/2020 9:53 pm
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