Large-Scale Deposition System by an Industrial Robot (I): Design of Fused Pellet Modeling System and Extrusion Process Analysis

Fused pellet modeling (FPM) is an important method in additive manufacturing technology that uses granular material instead of filaments. In FPM, prototypes are constructed by the sequential deposition of material layers. As the size of the part increases, the long build times and part deformations become critical problems. Methods for optimizing the extrusion process to eliminate the void density during large-scale FPM processes were studied. Based on analyzing polymer extrusion theory and non-Newtonian fluid properties, a miniextruder with a variable pitch and a progressive diameter screw has been proposed for large-scale fused pellet deposition. Each of the design parameters, such as the lengths of different function sections of screw, die shape of extruder nozzle, and the material properties, was analyzed. According to these analysis results, an extrusion process simulation for controlling the filament shape was carried out with multiphysics modeling software proving that the FPM could increase the building efficiency and deposition quality for large-sized parts.