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I am using an Ender 3 with a Micro Swiss hotend and a 0.8 mm nozzle, Polylite PETG filament and a masking tape covered glass bed. I have used Cura for slicing with settings:

  • Layer height: 0.32 mm
  • Wall line count: 2
  • Printing temp initial: 255 °C
  • Printing temp after first layer: 245 °C
  • Bed temp: 80 °C
  • 1 brim
  • Print speed: 40 mm/s (10 mm/s for initial layer)
  • 2.3 mm retraction at 20 mm/s
  • Fan speed: 0 % for first layer, 40 % after

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It is also interesting that the problem did not occur on half of the part, but did occur on the other half. Is the problem due to the slight warping up of the part, or due to something else? How can I fix it?

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    $\begingroup$ Retraction can help a little but you need a cooling system that helps to reduce heating while the nozzle starts the upper layer. This is a common issue on small parts on the other side where the air flow is almost null. If you rotate the part for printing you can see some differences. $\endgroup$ – Fernando Baltazar Jun 25 at 23:05
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What you are seeing is what is called the 'seam'. Since this part cannot be printed in vase mode (where the extrusion is essentially done as a compressed spiral), there is a point where the printing on a layer ends, and the printer moves to the next layer. This is where the seam is formed. Blobs that form at this change in layers are not uncommon, but the ones in your print seems larger than expected.

You can experiment with larger retractions settings which normal reduce the size, but these seams cannot be avoided completely.

Another change is that most slicers have the option to place the seam at different locations on your part, including placing them at random locations. This removes the pronounced seam, but put little blobs all over your print. Sometimes that is preferred for accuracy instead of the specific seam.

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    $\begingroup$ Thank you so much! I will try increasing retraction, and perhaps the coasting setting in cura. $\endgroup$ – whackamadoodle3000 Jun 3 at 8:06
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    $\begingroup$ Much better than to use retraction, is to calibrate pressure advance... retraction between layers is not particularly effective $\endgroup$ – FarO Jun 3 at 9:53
  • $\begingroup$ Some slicers also have an option to move the seam inside the part. $\endgroup$ – user10489 Jun 5 at 13:18

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