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PTFE insulator coupler clogged, drop of PLA found on the print

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After 1 week of successful small prints, the nozzle started to get clogged. I cleaned it and everything seemed to be fine, except that on a large print (20 hours) it failed mid-print again.

The filament got stuck in a different way so I had to take everything apart to discover the ptfe insulator coupler were responsible:


The grey filament I am using became bounded with the ptfe coupler and you can see that the tip of the wire has the print of a ball.

This tiny ball or drop was found on the failed print.

The brown color on the ptfe coupler might come from the bronze pla filament I was using before.

Do you know what could have caused this issue?

I would think that it is temperature-related and that at some point, the ptfe coupler's temperature dropped to a level below the melting point of PLA.

The parameters I was using were:

Layer height: 0.1mm

Shell thickness: 0.8mm

Fill Density: 20%



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The only way to pull the filament out was to heat it up before.

I use Ultimaker filament.

I changed the ptfe coupler and raised the temperature from 210 to 225 celcius degree and started the exact same print again.

The same issue happened at the end, the only difference was that I was here and heard the motor doing a strange noise, going back and forth. I manage to pause the printing and and block the filament.

I still don't know what is triggering this issue. A retraction issue or an imperfect seam on the filament that catches an edge in the nozzle are my leads.

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Hi Charles10,

Could you post a picture of your print head from this angle:


Filament should not be flooding into the coupler, nor should PLA bond to the PTFE. Have you done any Atomic pulls? I suggest doing a few Atomic pulls when you change filament to make sure your nozzle is clear.

Guide here --> https://ultimaker.com/en/support/view/149-atomic-method

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Thanks for your suggestions!

I played a lot with different parameters and solve this problem:

I raised the pressure of the feeder. The white tension pointer was at the top position, I lowered it down to the second line.


(the lower the pointer, the greater the pressure on your filament)

I also turned down the speed from 50 to 40 mm/s.

Before, I raised the pressure, the filament would get stuck because the feeder force was not great enough to overcome any friction changes from the filament in the nozzle. It would then back up and try again, over and over until the filament is completely ground.

After I made this adjustment, I was able to get a 40-hour print without any issues.


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