Blobs and zits are small bumps or raised spots on the print surface, typically appearing at layer seam points where the extruder starts or stops a perimeter. They detract from surface finish quality.
Common Causes
- Layer seam start/stop points — Excess pressure builds up where each layer begins
- Retraction settings incorrect — Too little retraction causes ooze at travel endpoints
- Coasting not enabled — The extruder keeps pushing filament at the end of a perimeter
- Temperature too high — Low-viscosity filament oozes more easily at seam points
- Pressure buildup in the nozzle — Residual pressure causes a small burst when restarting
Recommended Fixes
- Enable “wipe” or “coasting” in your slicer to reduce pressure at layer seams
- Set seam position to “sharpest corner” or “rear” to hide blobs in less visible areas
- Fine-tune retraction distance and speed to minimize ooze
- Reduce nozzle temperature by 5°C to decrease material flow at seam points
- Enable linear advance (Marlin) or pressure advance (Klipper) for better pressure control
- Use “extra restart distance” set to a small negative value (-0.02 to -0.05mm)
- Slow down the start of each perimeter to reduce initial over-extrusion