Loosing Temperature solved

[spunkhart 0]

Hey,

after Assembling the new Hotend and installing it onto my machine,

(which works sooo much better) after a few prints i got error messages in Printrun

'cold extrusion prevented'. I noticed that the heater works fine while preheating,

but when the fan starts the PWM goes up to 127 and tries to hold the temperature

but it ultimately fails and it goes down to 170°C. When i stop the fan with 'M107' the

temperature rises up again and the PWM goes to 50-70 and holds the temperature fine.

So I think something is wrong with my Heater. I measured the resistance of my heater

and it is about 10 ohms. Is that a correct value?

Any suggestions?

Thanks in advance.

[joergen 2]

The heater has nominally about 9 Ohm, if you measure 10 Ohm, that would make it a 36W heater, still plenty...

Check your fan assembly: if you are blowing cold air directly onto the heater block, it will not manage to keep the temperature. the cold air is supposed to blow downwards, and cool the printed plastic.

[spunkhart 0]

Thanks for the help. I figured it out.. as it turned out, my thermocouple was defect.

Due to friction (and harsh assembly) the isolation of the two wires was bruised

and the wires joined just outside of the metal can (where the crimping was done).

So it measured the Temperature just outside of the heaterblock and when the fan

started, the layer of hot air was blown away. And so the desaster started..

I fixed the thermocouple and it works like a charm again.