This is the first time I've run into this problem and it seems very confusing. I wanted to print a simple functional part out of PLA and although the first few layers were fine, the 6th/7th layer started to have some weird 'blobs'/deformations on it. I don't know how to fix it and the problem didn't go away after changing the filament. I suppose the problem is related either to my settings or the printer. It is very weird, I fully calibrated the printer right after the first fail.


  • nozzle 215 °C
  • bed 60 °C
  • speed 100, 50 mm/s for bridges
  • cooling 100 %, but no autocooling in order to print faster
  • using PrusaSlicer


enter image description here

  • $\begingroup$ Have you tried lowering your print temps? I'm wondering if your 215 °C is a bit warm for your PLA. Try bringing the temps down to 190 °C and see how it goes. $\endgroup$ Apr 9, 2020 at 13:41
  • $\begingroup$ Not hinting to the thick blobby infill, it looks at if 100 mm/s is way too fast for your printer, look at corners and infill reaching perimeters. The print quality is terrible. $\endgroup$
    – 0scar
    Apr 9, 2020 at 13:41
  • $\begingroup$ @0scar I thought that Prusa MK3S could reach up to 100 mm/s print speed. I rarely print slower than that and I still get decent quality. Maybe the surface my printer is standing on is uneven or there was some kind of wobble. I'm not sure why, but tightening the screws and cleaning the moving parts from dust, etc. helped. I also reduced the Z distance between the nozzle and the bed from 1.050 mm to 0.950 mm. $\endgroup$
    – AAaAa
    Apr 9, 2020 at 13:59
  • $\begingroup$ But clearly, it is too fast. You might need to get the nozzle closer to the bed it doesn't look like it is compressed/squished. $\endgroup$
    – 0scar
    Apr 9, 2020 at 15:17
  • $\begingroup$ @0scar The issue is fixed by now. To my surprise, I actually had to get the nozzle higher and it worked. $\endgroup$
    – AAaAa
    Apr 10, 2020 at 14:07

1 Answer 1


After hours of trying to fix the problem by trial and error I found that getting the nozzle slightly higher by approximately 0.1 mm was the solution. I cleaned the rods from dust, tightened most of the screws again and calibrated the printer.

I don't encounter this problem anymore even while printing at 150 mm/s speeds.

  • 2
    $\begingroup$ this hints you miscalibrated your printer - you want a gap of 0.1 mm between nozzle and bed in the 0 $\endgroup$
    – Trish
    Apr 12, 2020 at 16:48

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