(10/19/2016) I did retraction calibration for B'struder.

Extruder drive: B’struder Kysan Nema 17 5.18:1 geared stepper motor, 2.4 V, 1.0 A

config.g of RepRapFirmware-dc42 1.12a

M92 411.230 M201 X4000 Y4000 Z4000 E3000 ; Accelerations (mm/s^2) M203 X15000 Y15000 Z15000 E15000 ; Maximum speeds (mm/min) M906 X800 Y800 Z800 E800 ; Set motor currents (mA) M92 411.230

Retraction setting in Slic3r 1.2.9: Length: 3.4 mm Z Lift: 0.4 mm Speed: 15 mm/s (10 mm/s and 20 mm/s give similar result.) Retraction after layer change: on Wipe on retraction: on

Filament: eSun PLA 1.75 mm Layer height: 0.2 mm Printing speed: 20 mm/s Travel speed: 250 mm/s

190 degrees Celsius gave better result than 180 degrees Celsius. Why?! (3/16/2016)

White one was done by RepRapPro Fisher last year. There was huge improvement in retraction quality. Only modification I did I glued end of Bowden tube on the push fitting of the extruder half year ago.

190 C or 180C wouldn't make much difference.

Slic3r settings (3/16/2016): Layer height: 0.25 mm Travel speed: 200 mm/s

Retraction Length: 2 mm Lift Z: 0.4 mm Speed: 40 mm/s Minimum travel after retraction: 2 mm Retract on layer change: on Wipe while retracting: on

Previous Slic3r settings (2015):
Layer height; 0.1 mm
Extrusion width: 0.28 mm
Printing speed: 30 mm/s
Travel speed: 20 mm/s
Retraction
Length: 4.5 mm
Lift Z: 0.075 mm
Speed: 150 mm/s
Extra length on restart: 0.1 mm

Source:
Fine Positive Features Performance
http://www.thingiverse.com/download:872736