Thermal Runaway and MaxTemp Errors  

RE: Thermal Runaway and MaxTemp Errors

Same happened to me, after a while, printer resets itself or the hotend temperature goes down till trigger thermal runaway. 

This is my latest printer, and have about 1 year old running OK and without reason started to fail.

I replaced hotend heater, thermistor and also power supply. Finally I moved the EINSY Rambo to another printer (It was a very big and not easy job) my older MK3 and also started to fail so I conclude that the problem is the EINSY rambo. It is labeled as version "1.1b"

RE: Thermal Runaway and MaxTemp Errors

Posted by: @smartj

Hi 

I have a newer MK3S and I am unable to complete prints.

I got a maxtemp error last week after ~5 hours of printing. I read the help articles on the issue and here's what I did to fix:

1. took apart the e-axis
   • inspected the thermistor wires and hotend, they looked fine
   • tightened the hotend thermistor and heater cartridge
   • cleaned the hotend
2. measured resistance of the hotend thermistor wires where it connects to the printer
   • seeing 100-125K Ohms at room temperature
   • when I put my hand on the hotend to warm it, the resistance drops as expected
3. checked support -> temperatures: nozzle and pinda temps are 21C, bed 22C, ambient is 25C
4. ran temp calibration ok
5. heated the hotend and watched to see if it maintained temperature (it did)

 

Everything looked good, so I tried printing again.  This time it went for ~12 hours before getting thermal runaway error.  Again I read the help articles, and here's what I tried

1. printed the same print again
   • hit thermal runaway error on the same layer
2. edited the gcode to resume from approximately the same point
   • noticed that the nozzle temp starts at 240 (as expected) but slowly drops
   • hit thermal runaway error after 5-10 minutes
3. tried resuming again at a different point (moved the build plate)
   • same temperature drop
   • the error consistently (3 times) happens after about 5-10 minutes of bridging infill

 

My firmware version is 3.9.0-3421.  I have attached the Slic3r project.

I have auto cooling off and bridge fan speed override set to 100%. I'm wondering if maybe the filament fan is blowing on the nozzle at 100% and preventing it from maintaining heat?

 

help_me_obiwan_prusa_mmu_enclosure_7.3mf

The front fan may be running too fast. I would reduce the speed or maybe use a silicone sock.

RE: Thermal Runaway and MaxTemp Errors

@karl-herbert

I had a silicon sock on the hotend heater block for the first couple runs.

RE: Thermal Runaway and MaxTemp Errors

@pekote

Did you try different firmware? I’m wondering if it’s a software issue versus einsy board version.

RE: Thermal Runaway and MaxTemp Errors

Attaching proof that I measured the resistance of the thermistor. I tried really hard to jiggle the wires to see if there's maybe a broken cable, but nothing I did (except normal room heat/cooling) affected resistance.

RE: Thermal Runaway and MaxTemp Errors

I tried a few more things. 

1. flashing back to firmware v3.8.1 doesn't fix the issue
2. issue reproduces at any fan speed above ~60%, but only when the hotend is actively extruding
3. issue DOES NOT reproduce w/ 100% fan speed when hotend is not extruding
4. changed entire extruder assembly with new PC parts
5. checked thermal cartridge wire: 14.9 Ohms
6. checked hotbed wire: 2.6 Ohms
7. checked PSU input voltages while reproducing thermal runaway: 23.5V steady (same as rest)
8. checked hotbed output voltage while reproducing thermal runaway: up and down between 8V and 11.5V

The only thing I can think of to try now would be to buy a new thermal cartridge...