ExtrudoWhy is my 3D print surface zits and blobs?
Surface zits and blobs is usually caused by extra plastic oozes out right when the nozzle starts or stops a layer at the same spot each time. Small bumps or blobs appear on an otherwise smooth surface, often in a vertical line
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Quick reference
| Defect | Most likely cause | First thing to try |
|---|---|---|
| Surface zits and blobs | Extra plastic oozes out right when the nozzle starts or stops a layer at the same spot each time | Turn on coasting |
What it looks like
Small bumps or blobs appear on an otherwise smooth surface, often in a vertical line
Most likely cause
Extra plastic oozes out right when the nozzle starts or stops a layer at the same spot each time
How do I fix surface zits and blobs? Step-by-step
- 1
Turn on coasting
Enable 'Coasting' in your slicer, which stops extruding slightly before the end of each layer to use up built-up pressure.
Done when: Fewer blobs appear at the same spot
- 2
Randomize or hide the seam
Change your slicer's seam setting to 'Random' or 'Align to nearest edge' so blobs don't stack in one visible line.
Done when: Blobs are scattered or hidden on a less visible edge
- 3
Slightly reduce nozzle temperature
Lower the temperature by 5°C — cooler plastic oozes less at the seam.
Done when: Fewer or smaller blobs at the seam
Frequently asked
What causes surface zits and blobs in 3D prints?
Extra plastic oozes out right when the nozzle starts or stops a layer at the same spot each time
How do I fix surface zits and blobs on my printer?
Follow the step-by-step fix above, starting with "Turn on coasting". Each step includes a "done when" check so you know whether it worked before moving on.
Is this fix confirmed by other makers?
This entry is part of Extrudo's seeded defect library. Confirmation counts appear once real users report the fix worked.
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