Unstable hotend - MCU Shutdown - Loosing the will to live

[Mils24]

Basic Information:

Printer Model: Homemade Delta
MCU / Printerboard: MKS SBase 1.3
klippy.log attached

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Describe your issue:

Honestly guys Im loosing the will to live on this one. I have hunted around various forums and websites for solutions and I have tried everything I can at hand so far and still no solution.

My issue is intermittent and there doesn’t seem to be any pattern or reason to it that I can see. over the past week of fault finding Ive had prints that won’t start, prints that fail within minutes, and a 5.5hr print, print successfully!

All the information I can see points towards hardware issues but I have checked as many as I can without buying a new hotend but I want o double check that there are no software issues or other potentials before I replace the hotend.

What I have checked/ruled out:

1. Full check of all connectors and cabling. Found one loose wire on motherboard, replaced the connector but no difference.
2. Full resistance check of all wiring with multimeter to ensure all joints and cables are ‘good’ - all passed
3. Hot linked to hot end fans coming on as MCU shut down error happens at various times thoughout different prints.
4. Hotend has been PID tuned several times and correct profile is in partner.cfg. (hotend is a E3D Revo six btw)
5. Initially I thought it was potentially a PSU problem as I thought there was commonality to it becoming very unstable whilst homing, however I have since shot down this theory. However for completeness of this the PSU is a 12V 400W PSU. Heated bed is Mains driven via SSR therefore it should have more than enough power.
6. Upon reading some posts on here I have changed the max_power from 1.0 to 0.7 and this seems to have helped a little.
7. Upon reading some posts on here I have changed the smooth_time from 1.0 to 0.6 and it also seems to have helped. This seems to allow the sudden changes in hotend temp to rectify itself and keep printing whereas initially as soon as it would drop it shutdown immediately.

Im at a loss now and getting very frustrated as I can’t understand why some the same print file will print for hours and then the next time it will fail within seconds of starting.

Does anyone have any help or things to check that I haven’t already? My next move would be to replace the heater core but Im reluctant to do so when it can print for 5.5hrs successfully? Is there something Im missing in the software?

Final strange behevior that I have noticed. In my Print_Start macro I have adaptive bed meshing on. I have the macro set so that the mesh happens before the bed heat up. Sometimes this happens and sometimes as soon as the print start the bed start heating at the same time as the mesh. Is this common or could there be something wrong with how my machine/mcu is heading the temp signals/gcode?

Thanks

…
klippy-4.log (1.8 MB)

[Sineos]

Note the temperature “jumps”. According to laws of physics, these are impossible, so the most obvious explanation is a defect thermistor.

[gaolst]

Same conclusion as @Sineos.
It’s Thermistor issues, and it can be anything related to Thermistor like wires and ADC channel on your mainboard.
If you did check wires - you can also try to move your thermistor to other ADC channel and reconfigure sensor_pin, usually board have few of them.

[theophile]

Also, consider whatever cable routing you’ve done. If there are any connectors between the actual thermistor and the controller board, those connections could be causing the problem even if the thermistor is perfectly fine.

In my case I have this issue sometimes because I put crimp-on JST SM connectors on the thermistor near the print head to facilitate eventual replacement. That turned out to be an unwise decision because these connectors aren’t holding up well to the constant back-and-forth motion of the print head. Sometimes the jostling of these connectors affects the overall resistance of the circuit, which causes a temp graph that looks just like yours.

[mykepredko]

@theophile

In my case I have this issue sometimes because I put crimp-on JST SM connectors on the thermistor near the print head to facilitate eventual replacement. That turned out to be an unwise decision because these connectors aren’t holding up well to the constant back-and-forth motion of the print head. Sometimes the jostling of these connectors affects the overall resistance of the circuit, which causes a temp graph that looks just like yours.

You need to make sure that your cables are fastened to moving/stationary parts close to your connectors so that there is no movement/stress on the connectors. I generally use a couple of zip ties like:

This is generally referred to as “strain relief”.