This is a 3D printer extruder for extracting sand, dust, or other granular material from a hopper, and sending it down a Bowden tube under software control. See the OpenSCAD for material details; in particular the steel auger bit needs some modification to fit the stepper in the version.

My blog post giving a bit more background:
https://lawlorcode.wordpress.com/2017/01/23/sandstruder-metering-sand-for-3d-printing/