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:
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;
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.