I see that the extruder is overheating every time I try to change the filament using the on-screen function. The strange thing is that when I insert the PLA filament, it drops down in “liquid drops”, which indicates that the extruder temperature is extremely high. It strikes me that the firmware (V1.3.1) does not have a safety cut-out for exceeding the maximum temperature.
I suppose that the problem is the thermistor, which may be incorrectly indicating the temperature to the motherboard.
How can the thermistor be tested?
What resistance should be measured at room temperature to see if it works well or not?
Is any way to read read temperature by connecting the printer to a PC?
Thank you very much
This is a guess.
When you change the filament, the extruder goes up to maximum heat, about 230 °C to be able to output e.g. ABS. The printer “doesn’t know” which filament is being fed out or in. PLA has a much lower melting point and will therefore flow through before the extruder cools down.
When printing, the printer will get information about the material and set the appropriate temperature.
It should be possible to check the thermistor by measuring its resistance, but you should have a data sheet to hand for this. Zortrax should be able to provide this. The resistance curve is not linear if it is an NTC.
Pour about 1 dl of oil into a vessel that you can then put in boiling water to get 100 °C or directly on the stove with a thermometer in for higher temperature.
Put the thermistor and thermometer in the oil so that it is completely covered by oil.
Then measure the resistance at e.g. every 10 degrees while the oil slowly cools down to about 30 °C. Then you can compare your values against the data sheet.