Summary

Most instructions to set your DEFAULT_AXIS_STEPS_PER_UNIT on the extruder say to mark the filament with a pen. I wanted something more accurate!

The included STL is fit for the Think3DPrint3D extruder, but I've included a customisable OpenSCAD so everyone can have a play.

Instructions

Screw this on to your bowden extruder and you can really nail down your DEFAULT_AXIS_STEPS_PER_UNIT.

The included STL is the correct size for the Think3DPrint3D extruder, but I've included a customizable OpenSCAD file, so everyone can use it.

To use; place the calipers in the slot, with the screw plate resting in the lower slot to stop them from moving backward.

I recommend that you hold everything firmly in place while you do this. During testing, I had a shoe box under my calipers to keep everything steady.

Extend the caliper to the filament hole.

Extrude 1mm at a time until the filament is pushing the calipers.

Zero the caliper.

Extrude 10-20mm and watch as your calipers are pushed closed :-)

Note the reading (which will be negative) and adjust your DEFAULT_AXIS_STEPS_PER_UNIT accordingly.

You may want to push the filament into the groove before taking your final measurement as it can bend upwards sometimes.