Thermal Runaway??????

Hey guys,

So I'm printing with Matterhackers RYNO (PETG) for the first time. Hotend temp is 240C, bed temp 65C. Something very weird happened and I'm just wondering if anyone else has seen this at all. The print started fine and the 1st layer was magnificent. Halfway into the 2nd layer, the printer had a thermal runaway error on the hotend and of course, stopped printing. There was a large "blip" in the hotend temp, which had to have been more than 10C. I checked my PID values and realized they had not been changed like I thought they had. So I re-ran PID tuning from the terminal and entered new values and saved. I just started the 2nd print and I got the same "blip" in the graph:



This is the point where the 2nd layer started. Thankfully, the printer did not stop printing; no error. On my 1st attempt, I had the cooling fans come on at the same relative time, but at 75% of full power. I can honestly say I've never seen this on any of my prints before and this is most definitely after PID tuning. I guess my questions are: Has anyone else run into this? and if so, how can I fix this? It just seems really strange because I've never run into this issue before and I've printed at much higher temps than 240C on this hotend. Anyways, I would appreciate any feedback.

Thanks,
Adikted

 

I did a PID tune before printing this. The picture above is most definitely after PID tuning.

 

Yeah, I realized this about an hour ago when I tried printing a couple of really small parts. I unchecked the setting in Simplify3D that blips the fan to full power when increasing from 0%. Also, I increased fan speed incrementally, starting at 20% for the 3rd layer, then 40 for the fourth, and finally 60% for the 6th layer. It did the trick. The past week or two, I've been printing with no thermal runaway problems at all and this happened again tonight. I'm actually printing the fan mods right now that direct the flow to the tip of the nozzle. So hopefully this won't happen again anytime soon. I think it's worse for smaller parts because the hotend basically stays in place. If it's a larger part, then increasing the fan from 0 to 60 doesn't cause much of a temperature dip and it doesn't get an error.

p.s. I know the graph is time based. I just pointed out that "this is the point where the 2nd layer started" because the fans don't kick on until the 2nd layer.