Local thermal activation for a combined thermoforming and 3D-printing process

Abstract In this contribution, the use of upcycled filaments for the functionalization of technical thermoformed components using additive manufacturing is investigated. In particular, small series applications in the automotive sector are being addressed. A high-quality plastic filament is obtained from the off-cuts of the thermoforming process and used in a robot-based process to print on and thus functionalize the thermoformed components. This involves adapted path planning, which allows printing on multi-axis curved free-form surfaces with an articulated robot. The resulting process combination of thermoforming and additive manufacturing offers a circular material flow and allows a reduction in waste and total energy consumption while simultaneously increasing the possible shape variety and component complexity. This creates an alternative to the injection molding process with its high tool costs, especially for small series and complex component shapes. In addition, the homogenization of the materials used has positive long-term effects on recyclability at the end of the product life cycle. In realizing the combined process, the adhesive bond of the printed structures to the thermoformed base component is particularly important for the mechanical properties of the finished part. If the bond at the interfaces is insufficient, forces cannot be transferred from functional elements like screw bosses, ribs and honeycomb structures to the base component and vice versa. Therefore, local thermal activation plays a crucial role in the 3D-printing process to ensure sufficient polymer chain movement and entanglement across the boundary layer.