OK guys, I finally found what the issue is, or at least kind of where it’s coming from.
As some of you (and myself) suspected, my hot end is not reaching the reported temperature. I previously blamed the low readings on my IR thermometer on not being able to point the laser directly at the hotend, but it seems it was reporting accurate readings (around 95C when klipper reports 200C).
Now, here’s where things get a little weird. At this point, I’ve used multiple thermistors, but swapped in a new one anyways. My board also has a pin for a second extruder thermistor, so I plugged it in to that one and changed the pin in my printer.cfg. No change.
I tried switching the bed and hot end thermistors on the board and in printer.cfg, no change.
I changed the thermistor “sensor type” from “EPCOS 100K B57560G104F” (same as the bed) to “Generic 3950”, no change.
I found an article about tuning your pullup_resistance value. My cfg file did not have this value specified, so I added a line and started with the default of 4700, which made no difference (I’m assuming this value is loaded from the sensor type by default?). I toyed with the values until my thermometer read ~220C when setting the printer to that temp. However, to achieve this I had to adjust the pullup_resistance from 4700 to 13k+ (far beyond what should be needed) which makes klipper report 6C at room temp (print bed reports 27C). Unsurprisingly, I can hand-feed all the filament I want, but the temp reading is only now only accurate at 220C rather than only being accurate at room temp.
The thermistor, I feel, can be removed from the suspect list, as multiple thermistors exhibit identical properties.
I also feel the motherboard can be removed as well; there are three pins for thermistors, all three show accurate readings for the bed but identically inaccurate readings for the nozzle.
This only leaves software/ firmware, which I find incredibly odd for three reasons. For one, the printer was not even shut off in between “working” and “not working”; I successfully completed a print, and without shutting down, updating any configs, changing any settings etc., I swapped out the nozzle, and the printer hasn’t worked since. Second, both the bed and nozzle thermistor are configured exactly the same, so if the nozzle is not set up properly the bed should be wrong too. Finally, Klipper is really straightforward and it’s easy to configure things that commonly need configuring, it doesn’t seem right that a configuration got changed and I’m completely incapable of finding what happened and fixing it.
As a Temporary FixTM, I’m inclined to get a nice reliable probe thermometer, calibrate a pullup resistance value for common print temps, then updating my cfg whenever I want to change temps more than ~5c. This is obviously not even close to an ideal solution, but I don’t know what else to try. Everyone else I’ve seen with this issue has resolved it either through hardware replacement or fixing settings, and I’ve tried all I can with both.
This is really a head scratcher. I’m no Klipper expert when it comes to really tinkering with the printer.cfg, however if I was in your situation the next place I would go with troubleshooting would be on the firmware side of things. Klipper already makes regular backups of your important configs so maybe try making a copy of them and do a clean install of Klipper with a default printer.cfg for your printer and see if that helps narrow down the issue some more. Saves you having to spend money on hardware if you don’t end up actually needing it.
This is among the things I did today that finally nailed the temp issue, I used a config file from last month when it was working and there was no change.
I took am certain it’s software/firmware related. I’m also not an expert, but over the course of the last few days I’ve learned a lot more than I knew, and I’m pretty confident that at least everything I’m able to edit (or at least everything the average user is intended to edit) is set up properly, which is why I feel I’m running out of things to test
Have you updated Klipper itself on your mcu?
In fact what’s the firmware version before you do if you haven’t.
It may be a big fixed by a firmware update but if not as much work as you’ve done with capturing details would probably be handy for Kevin in tracking down a weird bug/issue.
And as frustrating as this has to have been you probably know more about how a lot of these thermal mechanics work with the printer and Klipper as well
I suspect an electrical issue on the motherboard.
- What happens if you swap the bed and hotend thermistor, and/or plug one of your reference thermistor into the bed input?
- What is the open-circuit voltage on the signal line of the hotend and bed thermistor inputs?
- What is the short-circuit current of the same?
If you see differences in those last two points, that is a clue that something is messing with the divider circuit that the thermistor is a part of.
I suspect an electrical issue on the motherboard. What happens if you swap the bed and hotend thermistor, and/or plug one of your reference thermistor into the bed input?
This is one of the tests mentioned in my post:
I also feel the motherboard can be removed as well; there are three pins for thermistors, all three show accurate readings for the bed but identically inaccurate readings for the nozzle.
As to your other two points, I myself know very little of reading electrical signals, but my EE friend was over earlier today helping with troubleshooting and he verified that nothing on the board was reading out of the ordinary.
(around 95C when klipper reports 200C).
Oh wow.
Yup. Granted, that was with an IR thermometer, which doesn’t get very good readings on small shiny things. Using a probe thermometer get me around 160c. This explains why I was able to extrude for a short while, at 95c my filament is not even soft, 160c is obviously still far too low to print but it was hot enough to partially liquefy the filament.
