Retraction
Pulling filament back before travel moves to relieve melt zone pressure and prevent oozing. Defined by distance and speed.
High priority
Filament-Specific
What It Is
Retraction pulls the filament backward before the nozzle travels to a new location. This relieves pressure in the melt zone so molten plastic doesn’t drool out during the move. Two key parameters: retraction distance (how far to pull back) and retraction speed (how fast).
What It Controls
- Stringing/oozing during travel moves
- Blob formation at travel start/end points
- Print cleanliness on multi-feature prints
Why It Varies
- Direct drive vs. Bowden (Bowden needs much more retraction: 4-7mm vs. 0.5-2mm)
- Material viscosity (PETG strings more than PLA)
- Temperature affects how much retraction is needed
- Nozzle diameter (larger nozzles = more residual pressure)
How to Calibrate (Manual)
- Print a stringing test (two towers with gap)
- Start with recommended retraction for your setup
- Vary distance in 0.5mm steps (direct drive) or 1mm steps (Bowden)
- Vary speed in 10mm/s steps (typically 25-60mm/s)
- Pick minimum retraction that eliminates stringing
How the Auto-Tuner Calibrates It
- Camera + CV on stringing test — evaluates thread presence at multiple retraction values
- Backlight shadow analysis detects even fine strings
- Tests retraction × temperature matrix to find optimal combination