This grant provides funding to develop variable-geometry dies for extruding complex plastic parts. Unlike most existing polymer extrusion dies, which have a single fixed geometry, design techniques will be created to build novel moving dies that morph between different shapes. Coordination of multiple actuators during the extrusion process will impose these changes in shape. The actuator locations will be optimized to provide the mechanical advantage required to resist the sizable pressure loads inside the extruder. The optimization will be accomplished with a genetic algorithm that considers the many design constraints, which include avoiding interference of moving parts, eliminating obstructions to the flow of the molten plastic, achieving a reasonably sized die, and minimizing actuator power consumption. Experimental work will develop new ways to manage the leakage of molten plastic within the die due to its moving parts. Prototype variable-geometry dies will be built and tested on a production extruder operated by an industrial collaborator. Validation experiments will derive empirical relationships between changes in the die geometry, extruder screw speed, and plastic temperature to provide process control settings that yield defect-free parts.
This research seeks to create the next generation of polymer extrusion dies that can produce a wider variety of more complex plastic parts. Specifically, the work aims to enable polymer extrusion to replace injection molding for a class of plastic parts, thereby simultaneously reducing production costs and manufacturing time. Additionally, it aspires to offer designers the flexibility to create novel engineering solutions with entirely new plastic parts of varying cross sectional shape. The developed design tools will have broader application to creating other variable-geometry structures such as morphing aircraft wings and micro-scale extrusion dies.