Weird pimples on print.

Hi guys!

I have this weird problem, where pimples as on foto occur. Every pimple is a place where extruder starts to create outer layer of the print. Each layer is one pimple. In slicer I have set Seam on Random (photo). If I select to create seam in the same place I got this ugly line through the print.

What am I doing wrong here? What do I change to eliminate this problem?

Thank you for all answers and help. Have a good day!

You're not doing anything wrong, but you need to calibrate the extruder/retraction settings. If you get it set right, the blebs will all but disappear. I use 1.5 mm of retraction, retract on layer change and lift the nozzle 0.5 mm when retracting, retraction speed 30 mm/sec and retraction acceleration 3000 mm/sec^2 IRIC. That gives me this:

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]