K Type Thermocouple Installing a capsule

  • Hi all,
    I purchased an unencapsulated K-type thermocouple from E3D, and have crimped a metal cap onto it to avoid contact issues. I configured it using M305 P1 T"K" X150

    It appears to read the right room temperature, but the measured temperature appears to asymptote at 200°C as I run it through a tune using M303. The heater was working fine before and easily reaching 250°C, which makes me suspect that the temperature being measured is wrong, not the heater and the fact it doesn't give short to other wiring (which were occuring without a capsule) suggests it isn't the capsule itself that is the issue, but I am not sure.

    I have inserted the thermocouple into the printer as shown in the pictures below, which sticks out slightly as the cartridge maybe 5 mm too long. I suspect either it is misconfigured in software or that there is an issue with heat conduction. I saw on another thread it can be worth grounding the cartridge can help.

    I'd love to hear your suggestions so I can get printing again!

    I am using a Duet 2 Wifi with RepRap 2.

    photo5872925305910441249.jpg photo5872925305910441250.jpg photo5872925305910441251.jpg

  • administrators

    do you have another temperature measuring sensor you can try together with this to confirm if its reading wrong or there is another problem?

  • @T3P3Tony I don't currently have another means of measuring temperatures above 100C, which is where the issues start happening - the heating rate begins to level off until an asymptote at 200C . However, I know that I was able to melt PLA at around 215C (according to my thermistor) before changing the thermistor with the thermocouple , and I haven't changed anything else, hence why I think it is an issue with the temperature sensing or conduction of heat.

  • administrators

    @qubit you can try the other channel on the thermocouple daughterboard (X151). also what version of the TC daughterboard and RepRapFirmware are you using?

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