Open Source Grinder Lets You Make Your Own Custom Compression Screws for 3D Printer Extruders

Engineers at the Michigan Technological University have developed a low-cost grinding machine for the manufacture of compression screws used in direct 3D printing systems — and have released it under an open license, citing the RepRap project as inspiration.

"Some of the most promising distributed recycling and additive manufacturing (DRAM) technical systems use fused particle fabrication (FPF) or fused granular fabrication (FGF), where compression screws force post-consumer waste plastic through a heated nozzle for direct 3D printing," researchers Jacob Franz and Joshua M. Pearce explain. "To assist the technical evolution of these systems, this study provided the details of an invention for a low-cost, easily replicable open source grinding machine for compression screw manufacturing."

"The system itself can be largely fabricated using FPF/FGF following the self-replicating rapid prototyper (RepRap) methodology. This grinding machine can be made from a cordless cut-off grinder and <$155 in parts. The new invention is demonstrated to be able to cut custom screws with variable (i) channel depths, (ii) screw diameters, (iii) screw lengths, (iv) pitches, (v) abrasive disk thicknesses, (vi) handedness of the screws, (vii) and materials (three types of steel tested: 1045 steel, 1144 steel, and 416 stainless steel)."

The manufacturing tool isn't just suitable for hobbyists who are willing to accept close-enough results, either: The team claims that in testing it proved more than capable of duplicating the design of commercially-available compression screws yet offers a far greater flexibility for the production of custom screws.

The device itself is based on a combination 3D-printed framework, printed in PLA on a Lulzbot Taz 6 printer, with plywood parts cut on a CNC router with a 500x500mm cutting area — though the researchers indicate the same parts could be produced on a CNC router as small as 450x450mm, or by hand with a jigsaw or bandsaw. The grinding tool itself, meanwhile, is a repurposed power tool.

"The results show that the device is more than capable of replicating commercial screws as well as providing makers with a much greater flexibility to make custom screws," the engineers conclude. "This ability added to the DRAM toolchain by enabling makerspaces, fab labs, companies and universities to fabricate compression screws rapidly for approximately the cost of the bar stock, which assists the goals of the circular economy based on distributed recycling and additive manufacturing."

The pair's work has been published under open-access terms in the journal Inventions.