Accelerating the product development process of overmolded structures via Robotic Screw Extrusion Additive Manufacturing

Abstract

Automotive components that are based on primary forming processes require a cost-, time- and resource-intensive product development process (PDP), since a new geometry-specific tool is required for each iteration. The use of Robotic Screw Extrusion Additive Manufacturing (SEAM) offers the possibility of replacing these primary forming structures in the prototype phase with additive structures, which increases the flexibility of the entire PDP. For this purpose, the presented work aims at extending the scope of application for additive manufacturing (AM) in the product development process. Robotic SEAM allows the processing of a large number of available standard thermoplastic pellets, which greatly expands the material selection and reduces raw material costs. This ability allows the use of the target material of the primary forming process, e.g. injection molding, that will later be used in series production. In addition, much higher plasticizing rates can be realized relative to other extrusion processes such as fused filament fabrication. The combination with a 6-axis industrial robot as positioning system as well as a turn-tilt table as build platform enables the fast build-up of even large components or additive manufacturing on existing structures. In this presentation, the robotic SEAM process will be demonstrated using the example of a spare wheel well to be printed on. In the series process, the spare wheel well, taken from an actual Mercedes-Benz series vehicle, is made of a formed organo sheet and overmolded with a 40 % glass fiber filled polypropylene. The overmolded structure consists of reinforcing ribs and functional interfaces such as screw mounting points and pins. In order to avoid the expensive injection molding tool in the prototype phase, these geometries are initially to be additively printed directly on the formed organo sheet, already using the target material. The focus is on the geometric and functional validation of early-stage components with the ultimate goal of manufacturing only the mold, ready for series production. This reduces development times and resource consumption leading to a more flexible and sustainable PDP. The presentation will provide insights into the studies on the adhesion between the organo sheet and the additively manufactured structure, the process planning and manufacturing of subareas of the demonstration part.