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Replacing a Hot End Thermocouple

Overview

Thermocouples are delicate components on the Gigabot -- proper use of the printer, maintenance, and handling of these components is important for their longevity. You may need to replace your thermocouple if you encounter ERROR_MAXTEMP or other errors. An obvious indicator of the need to replace the thermocouple is if it reads a temperature greater that 900C. This happens when the wiring of the thermocouple is damaged and their is a break in the circuit. Please search our Knowledge Base or contact support@re3d.org for more help with troubleshooting potential thermocouple issues.
 
In the event that you do need to replace the thermocouple, please follow these steps:
 

Gigabot

  1. Heat the hot end and remove the filament from the affected extruder.
    • IMG_0302.jpg
  2. If your hot end heater block has plastic residue build up on it that may prevent the thermocouple from being removed, brush the heater block with a a brass wire brush to remove the residue. This is important to make sure the thermocouple does not break when attempting to remove it.
  3. After removing, set the hot ends to cool down.
    • IMG_0303.jpg
  4. Once cooled to below 50C, turn off the Gigabot
  5. Remove the back print head cover by unscrewing the two bolts in the back plate, revealing the wiring connections
    • IMG_0143.png
  6. Remove the print head cover by unscrewing the M3 bolts on each side
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  7. Remove the extruder motor from the print head by first unplugging its cable, then unscrewing the 3 M3 bolts on the front of the extruder body and pushing it through the hole in the extruder body.
    • IMG_0503.jpg
  8. Unslot the connection of the affected thermocouple from the backplate of the print head, then push the loose connector through the hole in the back plate and then through the aluminum trolley plate.
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    • IMG_0497.jpg
  9. Remove the spiral wrap around the heater cartridges and wires (see above photo) and straighten out the thermocouple so that it can spin freely.
  10. Unscrew the thermocouple from the heater block with a 3.5mm wrench. If there is plastic surrounding the connection, you will need to soften it with a heat gun or heat the heater cartridge through the viki so that it doesn't break in the heater block.
    • IMG_0313.jpg
  11. Screw in the new thermocouple with the wire unplugged and straight so that it doesn't get twisted. Tighten with the 3.5mm wrench.
    • IMG_0314.jpg
  12. Reroute the thermocouple wire and plug back in and set into the slot in the back plate, then replace the spiral wrap.
  13. Screw in the extruder motor (making sure to not pinch any wires between the two motors), the back print head cover, and the top print head cover. *Make sure to not pinch the heater cartridge or thermocouple wires between the two motors, or the fan wires between the top print head cover and the aluminum trolley plate*
  14. Check that the thermocouple is working by turning on the printer and reading its value on the Viki LCD screen.
  15. If its reading the ambient temperature correctly, verify that its wiring is correct by heating that hot end to 40C and watch the Viki read-out temperature.
  16. If it functions as intended, your Gigabot is now ready to print again.

Terabot

  1. First, cool off the hot ends to <50C, then turn off the Terabot.
  2. Remove the print head cover by bending its tabs outwards and lifting it upwards.
    • IMG_0306_2.jpg
  3. Unplug the affected thermocouple and the extruder motor wire, then push the loose connector through the hole in the wiring plate.
    • IMG_0311.jpg
  4. Remove the screws for the wiring plate on each side, then lift it up slightly and push the thermocouple underneath it to freely separate it
    • IMG_0310.jpg
  5. Remove the spiral wrap around the heater cartridges and wires
    • IMG_0312.jpg
  6. Use a 3.5mm wrench to unscrew the thermocouple from the heater block
    • IMG_0313.jpg
  7. Screw in the new thermocouple with the wire unplugged and straight so that it doesn't get twisted. Tighten with the 3.5mm wrench
    • IMG_0314.jpg
  8. Replace the spiral wrap, reroute the thermocouple wire and plug back in, tighten the wiring plate, then replace the print head cover
  9. Check that the thermocouple is working by turning on the printer and reading its value on the Viki LCD screen.
  10. If its reading the ambient temperature correctly, verify that its wiring is correct by heating that hot end to 40C and watch the Viki read-out temperature.
  11. If it functions as intended, your Terabot is now ready to print again.
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