Extruder not heating

General LulzBot Mini
1

My mini’s extruder is not heating up. I took the case off and I’m confirmed the following:

  • All 3 fuses are OK
    The light on the board comes on when I tell Cura to turn on the extruder heater
    The voltage coming out of the board on the extruder connector is about 20V (I think it is PWM so hard to get an exact reading on a multimeter. I didn’t put my scope on it).
    The resistance of the extruder wire is about 100kohms (not sure what this should be).

Any suggestions on what to check next?

2

I was able to get it back heating… not sure what I did. I took off the fan and looked at the cartridge heater and then reassembled… Seems to be back in working order.

3

And now it’s not heating again… any ideas on connection points to check?

4

Could it be something in your start script? Slicing software have options to “wait” for the hotend and/or bed to reach a certain temp before printing. Typically its the bed first, then start the hotend.

What software are you using? Or take a look your g-code files and look for: “M190 Sxx” (bed wait for temp xx) and “M109 Sxx” (hotend wait for temp xx). If the latter (hotend) isn’t set, its probaby a good idea to enable.

5

This is even just controlling it manually. I think the cartridge heater is bad, we measured >500k. I ordered a new one from Amazon…

6

The cartridge heater is rated about 20 or 30 Watts if I remember right.

P = V ^2 / R

If you use 20W and 20V in the above equation, your heater should be about 20 ohms.

Check the crimp connections at the connector pins. They might be bad or intermittent.

7

I had a similar problem with the heated bed. One of the cables inside the chain was partially broken and making intermitent contact. I replaced it and everything is fine again.