Design of Extruder with Metering Section Removed and Replaced with Gear Pump for Machine Space Savings in Large Format Additive Manufacturing

Since its creation, the plastic extrusion screw has been applied to several manufacturing processes. One of the newest applications of this technology has been 3D printing. Using an extrusion screw allows higher extrusion rates than direct drive extruders using a filament spool. This paper further develops the design by decreasing the standard screw length by removing the metering zone and replacing it with a gear pump. This allows for a smaller machine footprint. Extruders are susceptible to surging (inconsistency of the melt pressure and flow rate). Adding a gear pump to the extruder increases flow consistency at the nozzle, but this adds additional length and weight. With the addition of this gear pump-based metering device, the metering section of the screw is redundant and can be removed. By creating a shorter extruder, manufacturers can increase the flow rate without increasing machine size. The proposed extruder design is validated through flow testing and analysis of voids in the bead cross-section with image processing. By showing that a consistent bead can be produced without a metering section in the extruder, this extruder design can print parts with a wide range of materials.