Trouble diagnosing high-temperature extruder (65W) heater faults

dflemstr

Hey,

I'm setting up my printer for high temperature printing (<500C) and I've step-by-step been replacing one part at a time on my extruder: first using a PT1000 sensor, then moving to a plated copper heater cartridge, then switching to a E3D NozzleX extruder, then a titanium heat break, and finally a water cooled extruder heat sink. These changes all went fine and I've been able to run the printer successfully for a few weeks after these changes. However the printer with this configuration struggled to maintain high temperatures; I assumed it was due to an underpowered heater cartridge.

Now I replaced the heater cartridge from using a 40W to using a 65W cartridge, to be able to keep temperatures more stable, and sure enough when the printer reaches the set temperature, it keeps that temperature perfectly. However, while heating up (even to a low temperature like 250C) the heater consistently faults with no apparent error message. If I reset the fault and resume heating, the heater eventually reaches 250C fine. I've been diagnosing the errors with 250C for now just to get repeatable measurements and to not play around with potentially dangerously high temperatures, but of course I'll be looking for a solution that also works up to 500C.

Things I have checked:

My PSU is a reputable brand (Meanwell) and rated to 350W.
I'm using 3 extruders like this with a Duet 3 Tool Board, and since my system is 24V, the tool board should be able to handle a 120W heater according to the specs, so that should be fine I think?
I've PID auto-tuned the heater several times and it always completes successfully (model parameters are currently e.g. M307 H1 R2.554 C349.500:118.400 D7.30 S1.00 V23.3 B0 for one of the 3 extruders)
The extruder has a pretty powerful PCF (as you can guess from the above heater params) but the faults don't ever occur due to turning on the PCF; they happen even when the PCF is completely turned off.
Running with M929 S3 logs absolutely nothing when the heater fault occurs.
Each heater is limited to 500C with e.g. M143 H1 S500
I have not changed M570 at all, maybe I should for this case? Feels dangerous...

Any ideas?

PCR

@dflemstr how are you PID tuning ?

M303 H1 or M303 T0

dflemstr

@pcr The latter (M303 T0)!

Phaedrux

What does your heater graph look like while the temp is raising? Photo?

What firmware version?

dflemstr

@phaedrux Here's a graph of me heating up Heater 1 to 250C:

I've very unscientifically marked with teal arrows where the heater faults occur, and at that point I run M562 P1 followed by re-activating the tool with T0 P0 (or clicking on "Heater 1" in the UI). Eventually the tool heats up and is rock solid at 250C, no problems whatsoever.

Some version info:

$ M115
FIRMWARE_NAME: RepRapFirmware for Duet 3 MB6HC FIRMWARE_VERSION: 3.3 ELECTRONICS: Duet 3 MB6HC v1.01 or later FIRMWARE_DATE: 2021-06-15 21:45:56
$ M115 B20
Duet TOOL1LC firmware version 3.3 (2021-06-15 16:12:58)

Phaedrux

Can you please share your full config.g and describe how your toolboards are wired? Specifically, are the temp sensors on the mainboard or toolboard?

It's possible you are experiencing some of the limitations described here: https://duet3d.dozuki.com/Wiki/Duet_3_firmware_configuration_limitations

dflemstr

@phaedrux sure, here you go! Thanks for the help so far. Full config.g. Please ignore some of the comments that are a bit out of date

Phaedrux

Also, does M98 P"config.g" produce any errors?

dflemstr

@phaedrux Nope, the config file loads completely successfully both with M98 or at board reset