Thermal runaway

Hi All,

Recently the RAMPS board on my PrusaI3 developed an issue with the heated bed not working. This later developed into the USB comms not working either, which was a problem as I use OctoPI. So I finally bit the bullet and got a new RAMPS board and Arduino Mega. I have chosen to use the current Marlin as I did not have a copy of the Marlin which came with the printer, I suppose I could have got one from the original printer supplier but thought I would upgrade to the current Marlin.

The printer is working but I keep getting issues with a "Thermal Runaway" showing on the LCD panel. I have managed to get a couple of prints without issue so the setup is generally working. I have done a PID auto tune and put the figures in the firmware but still get the issues. It is an E3D V6 hot end and I have tried the PID settings on the E3D web site and the results from the auto tune biut neither work. If I tell the hot end to go to 150 C and then to go to 200 C it almost always fails. It was all working fine befire I replaced the electronics. I have got another E3D V6 which I will try at the weekend.

Any other suggestions?

Z

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My blog: 3DR build and more . . . .

Try to change the extruder channel. So instead of using D10 you use D9. It is easy to do in firmware and will tell you if the MOSFET is latching or if it is a software problem.

Try to look at a curve of the temperature doing the print, does it fluctuate in a physically impossible way?

Get a 3rd RAMPS (just the RAMPS, don't need another MEGA) and try that. It is only 5USD a piece anyway and you can end up spending hours and hours troubleshooting this issues on the RAMPS just to realize it was some stupid intermittent short.

OK, will try another RAMPS board. The temperature graph in OctoPrint does not show any sort of wild swing in termperature.

Z

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My blog: 3DR build and more . . . .

Don't forget to change the channel extruder channel.

Just go to the firmware and open the file:

pins_RAMPS_14.h


Inside that find the lines:

#if MB(RAMPS_14_EFF) || MB(RAMPS_13_EFF) || ENABLED(IS_RAMPS_EF
#define FAN_PIN 9 // (Sprinter config)

Change that to:

#if MB(RAMPS_14_EFF) || MB(RAMPS_13_EFF) || ENABLED(IS_RAMPS_EF
#define FAN_PIN 10 // (Sprinter config)


Now go to:

#if MB(RAMPS_14_EFF) || MB(RAMPS_13_EFF)
#define HEATER_0_PIN 8
#else
#define HEATER_0_PIN 10 // EXTRUDER 1

Change that to:

#if MB(RAMPS_14_EFF) || MB(RAMPS_13_EFF)
#define HEATER_0_PIN 8
#else
#define HEATER_0_PIN 9 // EXTRUDER 1


Save the changes (don't forget, dosen't happen auto) and upload that. Then it will use the normal fan output for the extruder and the extruder for the fan.

Go into configuation_adv.h and for the hotend, adjust:

#define THERMAL_PROTECTION_PERIOD 40 // Seconds
#define THERMAL_PROTECTION_HYSTERESIS 4 // Degrees Celsius

The comments above them tell how to adjust them.

I've had this exact problem with my PCB heatbed. In my case, the thermistor worked, but not very reliably. I changed my thermistor for a different one I had (same type and such, just physically different) and I've not seen my issue come back yet.

All,

An update. I had a couple of cheapy RAMPS boards but had the same issues when I tried them, also when I tried swapping hot end channel the problem still persisted.Trying the firmware changes recommended by @stephenrc seemed to work, to start with but all it really did was make the problem happen less frequently. I tried my spare extruder / hot end and the problem went away but I had another unrelated issue with the cooling fan which prevented me using it full time.

I put my original RAMPS board back and removed the firmware mods and stripped down the original hot end and replaced the heater block, heater element and thermistor. When I got it all back together it ran OK both on the bench and on the printer. I haven't had chance to print anything yet as I have had a bug all weekend but it ran though over ten heating / cooling cycles with no issue, so hopefully.....

Thanks to everyone for your input.

Z

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My blog: 3DR build and more . . . .