I’ve been fighting clogging for a while. Some prints work, many don’t. The same print which worked will clog on the next print. And print quality has been kind of inconsistent. Bad filament, I thought? But switching didn’t resolve the problem.
Today, after a frustrating series of attempts to fix clogging, I finally decided to try switching from an all-metal hotend to a PTFE-liner-to-the-nozzle setup to see whether heat creep was my problem. (I have both styles of heat break for this setup, I just needed to cut a new piece of PTFE tube a different length.)
As I started to test with the swapped nozzle, Klipper errored out because the nozzle exceeded 400°C. Funny, it didn’t feel like it was that hot! I worried about PTFE fumes. At least we don’t have pet birds. Then I watched the temperature report keep climbing, up past 600°C. That seemed unlikely. I waved my hand near the hot end and it didn’t feel hot. I gingerly brushed the sock. It was only warm. I removed the sock and discovered I could touch the hot end.
I wonder how long this thermistor has been going bad?
The last time I had to do maintenance on the hot end, the cartridge had fused so thoroughly to the heat block that the heat block was damaged when I finally got the cartridge out. No problem, I was interested in swapping it out for a copper heat block I had already purchased anyway. That’s when I discovered that the copper heat block (as well as another aluminum volcano heat block I had) had no support for 3mm thermistor cartridges, only bare thermistors. I happened to have one bare thermistor in my spares and installed it, grumbling.
I think my hate for the bare thermistors has been validated. I had no idea that my clogging problem was probably just the nozzle being too cold, inconsistently, probably due to damage to the delicate thermistor, even though I tried to be very careful attaching it!
Once again thankful that machining is another one of my hobbies, I drilled a #32 hole (drills tend to drill oversize, and that was closest drill size under 3mm) in the heater block. I then drilled a few mm in with a 4.2mm drill so that the thermistor cartridge wouldn’t interfere with the shoulder on the heat break. It was behind the old thermistor screw hole, and there were a few threads there, so I was able to put a small grub screw in place to hold the thermistor cartridge in place.
After four failed starts while printing the first layer, I now successfully finished a 1.5-hour print.