Heated volumetric extrusion mechanism with co-axial Auger and Moineau pumps for 3D printing from plastic pellets

By Carlo Fonda

3d printing co-axial auger and moineau pumps

The higher cost and lower availability of the thermoplastic filaments -compared to pellets- make FDM 3D printers underutilized in developing countries.
We designed a solution to use easily sourced plastic pellets with precise volumetric control of the extrusion flow. This is done by a rotor made of a "Moineau" progressing cavity pump co-axially coupled with an Auger screw, both contained within a single heated stator.
Our extrusion mechanism works as follows:

1. plastic pellets/granules enter the Auger screw, they are melted by the heated stator and pushed forward by the rotation of the screw, entering the cavities of the Moineau pump;
2. the plastic is transported by the progressing cavities of the Moineau pump, proportionally to the amount of its rotation, to the extrusion nozzle.
   To our knowledge, this technology -already used in food and oil industries- has not been applied to 3D printers, the main issue being the need to keep the system at 200-300 C, suitable for melting.
   The final goal is to build a pellet extruder compatible with commonly used RepRap 3D printers at a low cost. It must be made out of metal and it can be driven by a stepper motor through a geared reduction.

Attachment: descrizione.png (169 KB)

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