Circuitprinter screw extruder design

The screw extruder is a complicated thing to design. So many requirements:

  • Parts must be sourceable from McMaster-Carr or Amazon, printed parts to at minimum
  • Extruder must fit into the tool area, and cannot be so large and heavy that movement interferes with print quality
  • Must use Luer lock 3mm or 5mm syringes
  • Must be easily to disassemble so that it can be cleaned

This is the V1 extruder I made the the Jubilee

The piece on the bottom is the toolchanger interface. It is 3D printed, and is a press-fit connection to the other main piece.

The extruder drive has a few parts:

  • Nema 23 stepper
  • Stepper to screw adapter
  • Screw
  • Hex standoff
  • Extender piece on hex standoff
  • Luer-lock. I’m using a UV opaque syringe in the image since Syraya Tech UV resin is being used as test print material.
  • Main assembly. The piece at the top was the hardest to design, since the 5mL luer lock syringe is pushed in, then is rotated by 45ยบ to lock in place. I added some tape to the outside since the 3D printed connection to the toolchanger interface is hard to do with a lot of precision. 3D prints typically come out with wall thicknesses about +0.150microns thicker, but can vary by +-50 microns so this took some testing and even then needed some tape.

The assembled tool:

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