Retraction settings explained: tower tests, Bowden vs direct drive, and G10/G11

What the retraction settings control

When one section of a layer ends and the nozzle travels to the next, plastic keeps leaking out under residual pressure. Retraction reverses the extruder before the travel and pushes the filament back afterwards ^[6]. PrusaSlicer and OrcaSlicer expose the same handful of controls under slightly different names:

PrusaSlicer definitions and defaults come from its source ^[5]; OrcaSlicer names come from its wiki, which also allows per-filament overrides ^[2]. PrusaSlicer’s tooltip calls deretraction extra length rarely needed, and notes that a quick retract before wiping can help Bowden extruders ^[5].

Prusa’s stringing guide adds context for its own presets: the shipped minimum travel is 1 mm, raising it saves time but increases stringing, and it recommends leaving Retract on layer change and Wipe while retracting enabled ^[6]. OrcaSlicer warns that too short a retraction fails to stop oozing while too long a retraction can cause clogs or under-extrusion ^[2].

Direct drive and Bowden, as the vendors document them

A Bowden tube puts a long, slightly elastic path between the extruder motor and the nozzle, and the published numbers reflect that:

Flexible filaments are a special case. Prusa notes they usually need longer retractions because the strand stretches as it is pulled back, and that they can take a lot of tuning ^[6]. OrcaSlicer lists PETG and TPU as more prone to stringing than PLA or ABS ^[2]. For TPU specifics, see the TPU guide.

Running the retraction tower

OrcaSlicer generates a tower with a series of notches, each printed at a different retraction length. Bambu Studio offers the same test in its developer-mode calibration menu for third-party printers ^{[1, 7]}.

1. Open the retraction test and set start length, end length and step. Keep the defaults for direct drive; for Bowden, try 1 to 6 mm in 0.2 mm steps.
2. Print the tower with the filament and temperature you will actually use.
3. Find the lowest section that shows no strings or ooze. The target is the shortest clean length, not the cleanest-looking section overall.
4. Measure that section’s height, then search the G-code preview for the Calib_Retraction_tower comment at that height to read the actual length.
5. Enter the length in the printer profile or as a filament override.

The wiki warns against reading the ; retract comments instead, because they may not include the full length when Retract amount before wipe is in use ^[1]. It also notes that low-oozing materials such as PLA and ABS may be clean from the first notch, in which case 0.2 to 0.4 mm is enough. If the top of the tower still strings, dry the filament and check the nozzle for leaks before trying longer retractions ^[1].

Firmware retraction with G10 and G11

Firmware retraction keeps the slicer out of the details: the G-code says retract (G10) or recover (G11), and the printer applies its stored length and speed. Marlin’s documentation lists two benefits: tuning at the machine level and smaller G-code files ^[12]. In PrusaSlicer, enable Use firmware retraction in Printer Settings ^[5]. OrcaSlicer has a setting of the same name, which its wiki labels experimental ^[3].

Klipper. Add a [firmware_retraction] section. Its defaults are retract_length: 0, retract_speed: 20 mm/s, unretract_extra_length: 0 and unretract_speed: 10 mm/s ^[8]. Adjust at run time with SET_RETRACTION, which takes RETRACT_LENGTH, RETRACT_SPEED, UNRETRACT_EXTRA_LENGTH and UNRETRACT_SPEED, and check the active values with GET_RETRACTION. Klipper’s docs say SET_RETRACTION is commonly placed in slicer per-filament settings, since filaments need different values ^[9].

Marlin. Build with FWRETRACT. Then:

• M207 sets retract feedrate F in units per minute, length S, swap length W for tool changes, and Z lift Z ^[13]. A retraction speed of 35 mm/s is F2100.
• M208 sets extra recover length S and recover feedrate F. Marlin’s example pairs M207 S2.0 with M208 S0.5 for a 2.5 mm recovery ^[14].
• M209 S1 turns on auto-retract, which treats reversed E-only moves in ordinary G-code as retractions ^[15].
• Repeated G10 commands without a G11 in between are ignored ^[12].

Marlin’s configuration defaults are RETRACT_LENGTH 3 mm, RETRACT_FEEDRATE 45 mm/s and RETRACT_RECOVER_FEEDRATE 8 mm/s, and the docs ask you to turn auto-retract off during filament changes ^[16].

Tune pressure advance first

OrcaSlicer’s guide puts retraction after flow and pressure advance so that extrusion is already under control ^[4]. Klipper states that well-configured pressure advance reduces the retraction length required ^[9]; its pressure advance guide suggests a small slicer retraction afterwards, around 0.75 mm with wipe enabled, and disabling z-lift on retract ^[10]. Marlin’s Linear Advance page goes further and says retraction may drop as low as 0 once K is tuned ^[11]. See the pressure advance guide.

When retraction is not the problem

Prusa lists causes of stringing that no retraction setting will fix ^[6]:

• Nozzle temperature too high; try 5–10 °C lower, or run a temperature tower.
• Moisture in the filament; see wet filament.
• A coating of old material inside the nozzle, common after long PETG use.
• Poor heat transfer between heatbreak and heatsink, or misassembled hotend parts.

Over-long retractions bring their own failure mode, so if under-extrusion or jams start after raising the length, work through the clogged nozzle guide and the stringing guide.