Dr. Lawlor's Code, Robots, & Things

January 23, 2017

Sandstruder: metering sand for 3D printing

Filed under: Random Thoughts — Dr. Lawlor @ 10:59 am

For the NASA 3D printed habitat challenge, I’m upgrading my 3D printer to be able to shuffle around fluffy basalt dust.  For that, I need a sort of extruder capable of moving sand around.  My weekend project was a “sandstruder”, designed to extract sand from a hopper, and send it down a (to be determined) sort of sand Bowden tube.

model_of_sandstruder

OpenSCAD model

cimg7040

3D printed in two halves

cimg7047

Extruding sand!

Sand extrusion seems quite reliable, although metering is not very consistent.  Wired up as an “extruder”, and programmed like a Wade’s geared extruder, a software commanded “10mm of filament” emits between 8 and 14 grams of dust, with an average around 11 grams.  It seems to run reliably up to the speed limit of the stepper, a few thousand mm per minute (so a few kilograms of sand per minute).

If the auger bit gets jammed up on a rock, the stepper just skips steps rather than destroying itself, which is one advantage of this low-torque direct drive setup.  I will need to pre-screen the sand to eliminate the rocks, however.

Like it?  Download an STL or the OpenSCAD source code on thingiverse (or github)!

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