I'm printing basically a large flat square pane. This goes fine for 3 layers, after which the temperature suddenly drops by about ten degrees. After a while, my printer goes into thermal runaway protection.
I restarted my print, and as soon as the temperature drops, I pause the print. I wait for it to go up again, and resume. It starts dropping again, so I decide to see about continuing this part at 200 degrees (which worked quite fine, so I think I'll stick at 200 for now.)
I have tested running the printer at 210 and turning on the fan, thinking maybe it's simply related to that. That does not give a thermal runaway, and a drop of 2 degrees max. My assumption is that it's the PID.
How do I fix this?
My printer is a heavily modified Anet a8, running Marlin.