Retraction: Retraction is the action of the extruder pulling back a small amount of filament to relieve hot end pressure. While this feature can help prevent stringing on prints, too small, large, slow, or frequent retractions can lead to zits and blobs.

Extrusion: Extrusion is a potential source of many print quality issues and it describes how filament is extruded or printed. Zits and blobs are a form of inconsistent or over-extrusion on the exterior of a model.

Nozzle temperature: The nozzle temperature is another possible source of zits and blobs, affecting a printer’s extrusion and how filament is melted. Too high a nozzle temperature can cause filament to ooze excess material even when the extruder isn’t pushing filament.

Printing speed: Printing speed is how fast the printhead moves while depositing material for the infill, walls, and first layer, for example. Constant changes in printing speeds and too high a printing speed can lead to quality defects, including zits and blobs.

Cooling: Cooling is a major part of the FDM 3D printing process, as the deposited filament needs to be properly cooled before a new layer is added. Too little cooling can cause zits and blobs because melted material will be more prone to move and form unwanted features when another layer is added.