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Set Fan on result in "under extrusion" (U2+)

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Hi Community,


I got the problem if fan is set on it result in under extruision. never had this issue befor but for 3 weeks i had it each time. So i stop using the fan.


It looks like the filament is not heating up enough if fan is set on. But the temp sensor (or Ulti's display) says a constant temperature. Cause that i am confused.


First option in my mind is to replace the heating bullet. But i don't want wasting money and time to replace a working heater.


Maybe someone is familiar with that issue.

I would be happy about helpfull infos.


Best regards


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Hi, i thought it was enought put printers type in the topic. I‘m sorry!


ultimaker 2+

Filament: pet (innofill), petg (two different brands)

I think it is not depending on filament because i print this filaments without this issue in former times.

At least one role was new shopped.


I forgot to tell, that increasing speed shows the same result...


and if i set the fan on, i cannot compansate the missing extrusion by increasing the extrusion multiplier...

i tried values more than 140% multiplier and temps over 10 degree over the  specs.. it didn’t  help.


the printig speed i can use is very less 60mm/s.


but please keep in mind:

the tempsensor vealue shows good match with low variations. Temp “seems” to be fine...

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1 hour ago, peterfrosta said:

i thought it was enought put printers type in the topic. I‘m sorry!

I missed that...sorry. I read the topic on the short title on the main page and jumped into the thread itself....ever just have one of those days?


However, the additional information does help.


It stands to follow that if you are having an underextrusion, increasing speed should make it worse. Did that happen?


Also, it may be possible that the temp sensor is a tad out of whack.

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