this post was submitted on 13 May 2024
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Hi guys. Please check my previous post for any background questions, I don't have it in me to go over everything again.

Long story short, I was having issues with clogging that were being caused by my hotend not reaching the reported temp. After a few days of troubleshooting and diagnosing the motherboard and Klipper settings, I gave up and decided the motherboard was faulty (even though I could not perform any tests to determine in) and bought an SKR mini. I got that all set up, and the printer has been working flawlessly since then.

Until now.

Same exact problem; one print goes perfectly fine, next print, failing to extrude by the 4th layer. I removed the clog, restarted the print, now can't even extrude the priming line. Fearing the worst, I disassemble the hotend, try hand feeding filament, and once again I am unable to push more than a few centimeters through before it gets clogged up. A probe thermometer reads ~160C while Klipper reports 200C.

What could possibly be happening here? The board is an aftermarket replacement from a completely different company, so I doubt it's a recurring manufacturer defect, but I have no idea what else can be causing this.

At this point I've spent so much time and money trying to fix this printer that I could almost buy a new one, but at this point I'm not convinced even that would solve the problem.

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[–] papalonian@lemmy.world 1 points 4 months ago (1 children)

I really, really appreciate the time you've taken to try to help me, but I'm positive the hot end not reaching target temp is the issue. If I push filament against the outside of the heat block, it melts at a very slow rate, when it would normally instantly liquefy against the block.

I'll drop my config file when I get home.

My temp chart, both before and after the issue started again, are near perfect flat lines. PID tuning done on current hardware.

My hotend has a fan blowing on the cooling block, and two part cooling fans.

There are no clogs/ obstructions throughout the hotend. New hardware has been tested (nozzles, heat throats)

Typically I print between 60-120mm/s depending on nozzle size and the model. But not long before the problem started I successfully completed a tower print at 200mm/s with zero issues. It should be noted, though, that once again this is an issue happening outside the realm of print settings.

[–] morbidcactus@lemmy.ca 1 points 4 months ago (1 children)

Super bizarre...

Any chance there's some mechanical damage to the thermistor? If you've rebuilt the hotend a bunch of times it's really easy to do, I've totally reefed down on a setscrew before and flattened one, could lead to it possibly reporting a wrong value, a crack + high vibrations during printing + thermal cycling could lead to it getting worse over time. Sudden shifts to me would suggest a problem with the thermistor itself, especially given the total overhaul you've done. As crappy as it is too, if I recall electrical components often follow an early failure pattern where they can have a higher failure rate at beginning of life and then drops off, for the price of thermistor cartridges it's not a bad idea to keep some on hand just in case.

To make your life easier, Do you have a molex connector at the hotend? A lot of thermistor cartridges come with short leads and a molex connector, makes swapping them so much easier. If you don't already have some crimpers, Engineer PA-09 is a solid pair that'll do everything from molex to jst.

[–] papalonian@lemmy.world 1 points 4 months ago (1 children)

Thermistor swap was done a few times on the old board when the same issue was happening. I had 3 of them that I was swapping between.

Currently in there is a pretty nice thermistor that, rather than using a set screen to keep it in place, is actually built in to the end of a set screw; it's effectively impossible to damage it. Unfortunately, it's a known-good resistor, my problem lies elsewhere.

[–] morbidcactus@lemmy.ca 1 points 4 months ago (1 children)

Wow yeah, that's even more annoying then. Last ditch thing to me would be to check the resistance across th0 and compare to thb, I got ~6.28 kohms on both checking a spare board, just super strange this happened so suddenly.

[–] papalonian@lemmy.world 1 points 4 months ago

Good call on checking that resistance, didn't think of that before.

Even more frustrating is it happening twice across two different boards!