My M300 cant hold temperature at hot end


My Zortrax M300 have worked great until now. it seems it can not hold temperature when printing. I hade a testprobe and some kapton tape to wrap around the hot end and as the picture shows it heats up nicely to about 211c (as set in Z-suite) and when the printing starts it drops down to about 180-190c and minimum filament comes out and the extruder just clicking.
what could be the problem?

Hey there! It can be caused by faulty heater&thermocouple or extruder cable. How many hours has your printer worked so far? You can check it in Menu>Information>Printer information. Do you have a multimeter?

The heater and thermocouple are new, and I even tried the old pair with same results.
I have a multimeter, 394h

Thank you for the information. In that case, please check extruder cable paths’ continuity with a multimeter and let me know the results. Do you have such issue when printing other materials too (with higher temperature)?

There’s 0ohm at all four cables. yes same fenomenon on higher temp.

I have checked the resistor in thermocouple and it start the print at 50 ohm and then drops to about 43-44ohm. the heater receives about 24v when heating and when it gets to 50ohm it drops to about 9v and when it get do 43-44ohm it raises to about 13-15v.

I have been testing to but the temperature up to 245c in Z-suite but it always drop down to about 180-190c when printing for about 30-60 sec.

I changed the hot end to a brand new one and now it works. whats the lifetime of a hotend?

Thank you very much for the information. Hotend lifespan is approximately 350 working hours (but it can work for much longer time), it can vary depending on materials that you use. Please, observe the printer and let me know in case the issue reoccurs.