Innovative high-strength screw connections for additive manufactured thermoplastic components

Components that are additively manufactured by material extrusion (MEX) are exposed to complex challenges due to their layered structure. Anisotropy and the risk of delamination must be given special consideration, especially when they are exposed to high loads. In case high-loaded components have additionally to be connected to other parts or assemblies via screw connections, the connection area in the MEX-manufactured component is a limiting factor for usability. This article presents a novel method in which a preheated metallic threaded sleeve with internal and external threads is inserted into the component in order to create a high-strength threaded anchoring. This prevents pre-damage such as delamination in advance. As part of preliminary investigations, a selection of relevant parameters was first made. An open parameter test rig was developed with which the threaded sleeves could be applied into test specimens with high repeat accuracy. The effectiveness and the increase in the achievable pull-out forces were demonstrated by means of pull-out tests. It was also shown that the heat input via the outer thread flanks during application has a positive influence on the overall strength of the component.