Flexible and High-Precision Integration of Inserts by Combining Subtractive and Non-Planar Additive Manufacturing of Polymers

Abstract

Additive manufacturing of polymers offers great potential for the production of complex structures. In particular, Fused Filament Fabrication (FFF) processes can be used to create functionally integrated components, in addition to easy handling, tool-free production and large material options. By combining a FFF system with a robot, inserts of different types can be integrated automatically during the printing process [1]. The low dimensional accuracy of FFF induces great difficulties during the insertion operation. Furthermore, with FFF, a planar layer structure leads to a stair-step effect when overprinting inserts with curved outer contours and reduces the adhesion to the insert. Further, the adhesion of FFF-filaments to the insert depends on the surface treatment of the insert [1]. A FFF system was combined with a robot [2] and has now been expanded to include a subtractive finishing unit and an inline process control based on a machine vision system, which enables the dimensional accuracy of the FFF components to be checked during the printing process. To be able to produce functionally integrated components, a flexible control architecture is being developed that enables the execution of additive and subtractive process steps. Optimal integration of inserts with complex geometries is facilitated by using non-planar layers in the FFF path planning. For this purpose, the filament layers of the FFF components follow the tilted or curved contours of the inserts. The modified process is demonstrated by manufacturing an integrated stator for an electric motor. A system for an additive-subtractive process for the integration of functional inserts was developed. In addition, a concept for the implementation of an improved connection of the inserts through non-planar FFF layers was created. First steps for the integration of the various system-modules and optical analysis of the dimensional accuracy and the development of a printing strategy for non-planar overprinting of the inserts have been realized.