Underextrusion after travel moves with PETG/Colorfab XT

  • I came across several issues which seem to have been lowered.
    Firstly, I changed from a 0.4 to a 0.5 mm nozzle. Because of the backpressure I was not able to print my PETG (Colorfabb XT filament) below 270°C which caused unresolvable oozing. After that I was able to extrude till 230°C.

    The left print below shows the result. I disassembled the hotend, there was no leak or whatsoever. Maybe it was too cold for printing. However, the temperature displayed was 250°C. Then I replaced the cheap aluminum heat block with a copper alloy based one. After that my PIDs did not work anymore. I had to greatly enhance the d-term, otherwise there was a big overshoot. Guess there was a serious heat conducting issue with the old BQ hotend.

    Prints using BQ Alu Heatblock (left) and Copper alloy Heatblock (right)

    Anyway, from there it became better. However, I noticed that I still have severe underextrusion after travel moves (second piece, first picture, first piece, second picture). I use Cura, so I activated retraction with the feature to prime after travel moves. I got the wall closed just after 0.35 mm³.

    Prints using Copper alloy Heatblock (left)

    My Question: Is this underextrusion after travel moves normal for PETG/XT? I did not discover such behavior with PLA or ABS in the past.

    Current Site Advice: Despite the weight, copper heat blocks seem to be worth the upgrade.

    What is your retraction length?

    I need 2.5 mm for PETG. But the underextrusion happens also if no retraction is active.

  • Brian Chow

    Brian Chow Correct answer

    4 years ago

    Have you tried adjusting the Extra Restart Distance in Simplify3D or Retraction Extra Prime in Ultimaker Cura? Most slicers should have a similar setting, perhaps named just slightly differently. A small positive value can help prime the nozzle after a long travel when you've lost back pressure or oozed a little.

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Content dated before 7/24/2021 11:53 AM

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