The Libro-Struder is an original 3d printer extruder created at the Pueblo City-County Library District. It is part of the RepRap Libro project but is a general purpose filament extruder for all your filament-pushing needs. It uses plastic-on-plastic friction forces rather than toothed-gear biting forces to grip and advance a plastic filament. The Libro-Struder is less prone to jamming and slipping than the more common Wade or Bowden-type extruders. It can also be created with fewer specialized parts. The design explores the idea of using taken-apart pop rivets as tiny bushings on shafts. The current model does require a stepper motor that has an orbital gearbox attached. I have had much success with a Nema 17 stepper with a 27:1 gearbox, Part No. 17HS19-1684S-PG27.
Hackers encouraged to print their own gearbox. :-)
Original design by David Hartkop, Technology Trainer PCCLD.
Nema 17 motor, 27:1 gearbox #17HS19-1684S-PG27
4 x M3x8mm screws
Push-in pneumatic fitting for 4mm od nylon tube
18 gage steel wire, 3 inches
22 x 1/8” x 1/4” long pop rivets, steel.
nut #10 (M5)
set screw #10 x 3/16" long (M5x5mm long).
-> Movement of the central gear is slow and continuous while movement of the smaller gears undulates as they periodically engage and the spring arms flex slightly.
-> The center hub of the big gear is held tightly to the motor shaft with a set screw in an inserted nut. The hub is reinforced by wrapping some bare stranded copper wire around its groove 6-8 times and then soldering around it. This creates a metal band that is fused into the plastic.
-> Print Settings for Parts: All were printed in ABS 1.75mm filament
Big Gear: 4 shells, 75% infill, 0.3mm/layer, no supports
Small Gear: Same as big but just 2 shells.
I/O Module: 2 shells, 25% infill, 0.3mm/layer raft & support
Galaxies: 3 shells, 25% infill, 0.3mm/layer, raft, support for motorGalaxy
-> The Big Gear's nut and set screw are #10 and #10 x 3/16" long (M5, M5x5mm long).
See video the Libro-Struder power loading here: https://youtu.be/CCGOJw2fUM8
See video of the Libro-Struder extruding here: https://youtu.be/b2AEpmFmc_0
See video of dragging filament out of the Libro-Struder: https://youtu.be/2r9iNOMyIR0