LARGE SCALE POLYMER ADDITIVE MANUFACTURING OF LIGHTWEIGHT FOAM STRUCTURES

Additive Manufacturing of thermoplastic polymers is currently being conducted on both large and small scales for industrial and research applications. Big Area Additive Manufacturing (BAAM) is traditionally used to manufacture structural components for tooling, rapid prototyping, and end-use components. A dual hopper system was installed on the BAAM system allowing for multi-material structures to be manufactured and a pellet mixer added alongside the dryers. The pellet mixer, installed, can take up to four different components to create a custom blend of premanufactured pellets to create a new material composition for extrusion. Lightweight polymers can be extruded from the BAAM extruder by adding foaming agents to this mixture. Foaming agents can be in the form of expandable foaming agents or syntactic glass balloons, or through using endo/exothermic reaction pellets. This upgrade can create parts with significantly lower densities than traditional printed structures and can be done in high and low resolution with specific densities of 0.3-0.7 g/cm3. Foams can be utilized for multi-material light-weighting, complex lightweight core structures, packaging molds for high-cost components, etc. When creating foam components, layer times, the quantity of foaming agent, nozzle diameter, and heat exposure can directly impact the quality of the printed structure. In the case of high resolution (small nozzle diameter) foam prints, maintaining a constant bead width, layer height, and foaming consistency can be very challenging. In addition, lightweight structures such as flying wings and foam package molds can be created concisely by controlling various processing parameters such as tool pathing, extruder RPM, and material selection.