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Retraction Test Generator: Tune Stringing in One Print

Download the two-tower test, slice it with your normal settings, and drop the G-code here. Each band of the towers gets its own retraction length (or speed), clearly marked in the file. Print it once and pick the band with the least stringing.

Loading the retraction test generator...
Demo with a sample file, recorded in this tool.

How to run a retraction test

  1. 1

    Set the range

    Pick direct drive or Bowden for a starting range, or type your own start, step and number of bands. Each band is a few millimetres of tower.

  2. 2

    Slice the towers

    Download the STL and slice it with your usual profile and retraction on. Turn off wipe and avoid-crossing travel, so every travel crosses the gap between the towers.

  3. 3

    Add the retraction changes

    Drop the .gcode here. Every retraction in each band is rescaled to that band's value and each band is labelled in the file. Check the table, then download.

  4. 4

    Print and compare

    Look at the strings between the towers band by band. Pick the lowest value with clean travel, and put it in your slicer.

Typical starting ranges

Ranges people commonly start from. Your extruder's documentation or slicer profile is a better guide if it gives one.

Direct driveLength about 0.2 to 2 mm in 0.2 mm steps, at 25 to 45 mm/s. Too much retraction on a direct drive can grind filament or cause clogs.
BowdenLength about 2 to 6 mm in 0.5 mm steps, at 25 to 45 mm/s. The tube needs more pull before the nozzle pressure drops.
Speed testKeep the length you found and step the speed instead, for example 20 to 60 mm/s in 5 mm/s steps.
TemperatureStringing also depends on temperature. Run the temperature tower first, then this test at the temperature you picked.

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Retraction test FAQ

Print two towers a few centimetres apart so the nozzle travels between them every layer. Change the retraction length every few millimetres of height. The band with the fewest strings and no gaps or blobs on the towers has the right length. This page makes the towers and the G-code changes for you.
Only retraction moves. In each band, every retraction is scaled from your slicer's length to the band's length, and the matching unretraction is adjusted so the nozzle is primed exactly as before. A labelled comment marks where each band starts. Firmware retraction (G10/G11) gets one M207 or SET_RETRACTION line per band. Nothing is saved to the printer's memory.
Wipe moves the nozzle while it retracts, so part of the retraction happens during the wipe. The tool scales those moves too, but the test is easier to read when every retraction happens in one place, between the towers.
Yes, with plain .gcode in absolute or relative extrusion mode, from Cura, PrusaSlicer, SuperSlicer, OrcaSlicer, Bambu Studio, Simplify3D and others. Binary .bgcode and .gcode.3mf files must be exported as plain .gcode first.
The smallest value that removes strings, because more retraction is slower and wears the filament. Direct drive extruders often need around 0.5 to 2 mm and Bowden setups more, but your test result is the number to trust.
Yes. If the G-code uses G10 and G11, the tool adds one line per band instead: M207 S<length> for Marlin and RepRapFirmware, or SET_RETRACTION RETRACT_LENGTH=<length> for Klipper. The setting stays at the last band's value until you restart the printer or set it again.
The tool only rescales retraction moves inside the towers and adds comments, and it never adds commands that save settings. Still, check the table of bands and preview the file in your slicer's G-code viewer before printing, and watch the first layers.

The G-code changes are made in your browser and only touch retraction moves inside the test bands. Check the file in a G-code viewer before printing and stay near the printer for the first layers.