At one height, thermal runaway starts
Seems like every time my z gets to 1.2 a thermal runaway starts. I can pause the print via Octoprint and the temperatures start to stabilize. If I resume, it starts to fall again. can't figure out what's up. I can heat it and leave it on for extended periods of time, but the temp just starts dropping at 1.2mm height.
Re: At one height, thermal runaway starts
Hi Gabe,
you may have a problem with the extruder plug on the mini rambo, working loose, or a wire breaking in the cable bundle to the back of your X carriage behind the extruder
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: At one height, thermal runaway starts
It may be that the particular item you are printing combined with the fan leads to excessive cooling in the area where the thermister mounts. I have had this happen, and of the options to fix it I went with using tune to reduce the bed temperature by 5C before getting to that point. Putting a cover over the printer worked as well.
RE: At one height, thermal runaway starts
This exact thing is happening to me... at 1.2 Z I keep getting a thermal runaway. It has happened twice in a row at the same exact position in the print. It could be a coincidence but it looks like a bug. Something about the Gcode of this print causing the printer to either think the temperature is increasing/decreasing, or to make it actually increase/decrease.
RE: At one height, thermal runaway starts
The bug is the wiring. Most likely directly behind the extruder. Heat the extruder and wiggle the cables while monitoring the temperature. Find the broken cable and you will be fine.
RE: At one height, thermal runaway starts
Same happened to me with the print bed.
Looks like a SW bug, because pre-heating functions just fine.
I paused my print several times, pre-heated the bed to the desired temperature 90 degrees en resumed printing till the temperature dropped again to 70 degrees. Then paused again etc.
After 3 or 4 times the temperature of the bed did not drop anymore and stayed at 90 degrees.
Next print no problem. I don’t understand it. Just hope it will not happen again. I’m printing the new parts for the 2S to 2.5S right now.
RE: At one height, thermal runaway starts
Guys!
- Read the answers!
- bring your cables in order / repair them
- and happy printing
RE: At one height, thermal runaway starts
Sorry, but how can it be the cable if preheating the bed, even during a print pause, works perfectly?
This means that both heater connection and sensor connection are working fine.
No cabling or connection problems.
RE: At one height, thermal runaway starts
Read the header! "At one height, thermal runaway starts"
In seldom cases one could get a bed runaway with to much cooling directly above the bed sensor.
In almost all cases those runaways are caused by broken cables with intermittend contact depending on how they are bent.
No matter whether the preheating works or not. If you are not content with answers, just don´t ask.
Good luck with searching the failure in the firmware... You certanily will be the 1st to find it.
RE: At one height, thermal runaway starts
I found my issue. It indeed wasn't a firmware bug but it also was definitely not a cable issue as Alexander so adamantly insists. 1.2 Z was where all of my parts started bridging over support material. Fans were set to 100% for bridges and the fans caused a perceived thermal runaway effect at the thermistors. This was confusing because it never happened before I upgraded from Mk2S to Mk2.5S. It must be the new fan nozzle or possibly an update to the thermal runaway logic in the Mk2.5S firmware.
RE: At one height, thermal runaway starts
[...] 1.2 Z was where all of my parts started bridging over support material. Fans were set to 100% for bridges and the fans caused a perceived thermal runaway effect at the thermistors.
Beyond checking the fan shroud alignment, you might consider using a silicone sock to insulate the block from the fan airflow.
RE: At one height, thermal runaway starts
.... It indeed wasn't a firmware bug but it also was definitely not a cable issue as Alexander so adamantly insists......
... Fans were set to 100% for bridges and the fans caused a perceived thermal runaway effect at the thermistors. This was confusing because it never happened before I upgraded from Mk2S to Mk2.5S. It must be the new fan nozzle or possibly an update to the thermal runaway logic in the Mk2.5S firmware.
Thank you for trying to f**k with someone who´s here to help. It at least would have been nice, although it have been not the cables, to aknowlege you got led the right way with the fan and too heavy cooling over the senor mentioned.
There´s a reason I "adamatly" insisted on the cables, you even wouldn´t have to ask a question since it feels like every third thread here is about some runaway or temperature-drop which in MOST cases are broken cables which is the MOST common failure with this printer.
What you didn´t tell us in the beginning is that you did an upgrade to 2.5. Had you done that, maybe one would have hinted on the fan earlier and not be so "adamantly" with the cables.
RE: At one height, thermal runaway starts
@bobstro
Ugh I have an extra one but it's just barely the wrong size. I need to buy one for this hot end. Thanks for the suggestion!
RE: At one height, thermal runaway starts
@alexander-s27
Alex, be happy, life is good. Certainty is the enemy of truth. We can all be better engineers/designers/makers if we sprinkle in a little self doubt every once in a while. It will also make our suggestions more helpful for others.
RE: At one height, thermal runaway starts
I found the solution for my problem elsewhere on the forum. Being a newbe here, I don’t know how to add a link. SOLVED - BED THERMAL RUNAWAY at 90C
Small object in the middle of the bed. Temperature sensor of bed is also in this position under the bed. Fan cools down the bed too much. Solution: place small objects not in the center. I haven’t actually tried it yet, but it sounds plausible. It also explains why the problem went away after a couple of times pause - preheat - resume. The distance from extruded and fan to bed has increased thus less cooling down of the bed.
A bit the same like you posted Jordan-b9. Thanks.
No wiring issues. Which I already thought, because otherwise the in-between preheating would also not work properly.
RE: At one height, thermal runaway starts
And Alexander also, by the way, wrote that this can happen in seldom cases.