Plastruder Temperature Is Not Stable Or Not Heating

Signs of this could be subtle, but the most obvious is that immediately after aborting a build due to a stalled extruder, the temperature in control panel is much lower than it should be for the cooling time between abort and opening the panel. The wires on your nozzle may be damaged. To test this, turn off the system and measure both the thermistor and the nicrhome heater.

The heater can be measured easily without disconnecting it. Turn off the machine, and measure the voltage across the nicrhome terminals. (It should be zero with the machine off, but there may be some residual voltage for a short while.) If the voltage is zero, switch to resistance, and check if the nichrome measures around 6-8 ohms, as it did when it was built. (You can also disconnect the wires and measure it, which may be a bit safer.) After you've initially measured, gently wiggle the wires from the loose ends to the nozzle and make sure that the reading doesn't fluctuate. If the resistance jumps higher, you have a intermittent connection somewhere. As the nichrome doesn't solder, the joint between the wires and the nichrome is a likely spot. If the resistance drops lower, the insulation has probably flaked off the nichrome and it is shorting against itself or the heater barrel. Either problem will require a rebuild of the heating element.

The easiest way to test the thermistor is to check the control panel with the power on. Check if the temperature reading is reasonable. If the nozzle is cool, heat the thermistor directly with your finger (not on a hot nozzle!!) and see if you can get the temperature to change by a degree or so. Gently wiggle the wires and see if the temperature jumps. If it does, you have an intermittent connection somewhere.

If the thermistor temperature is not reasonable, with the machine off, disconnect the wires for the thermistor and check the resistance directly. A room temperature nozzle should be 90k-110k ohms. If it reads as open circuit or short circuit, your thermistor could be damaged or the leads to it touching, etc. If it looks ok when measured directly but wrong in the control panel, your extruder controller might be damaged or insane — try reflashing it. (See Insane Plastruder Controller.)

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