Development of diffusion bonded large scale parts for highly stressed tool applications

Due to rising demands on the quality and of the final plastic product, it becomes increasingly important to influence the thermal behaviour of the tools (e.g. variothermal tempering). Due to this fact the geometry of heat-control channels becomes very complex, leading to a change in the manufacturing strategy of large scale tools – manufacturing of a layered structure and joining to the complete component. Even though smaller parts can be joined by brazing, diffusion bonding emerges as the promising method for large scale, highly stressed parts as moulds or distribution systems etc. However, in order to apply diffusion bonding for such application, it becomes necessary to understand the major influences and up-scaling effects. In the present paper, first results of a collaborative research between joining and tooling institutes and companies will be shown. The aim of this work is to use the understanding of process-relevant influences for deriving a suitable diffusion bonding related manufacturing chain. Combining numerical simulations for the design of the channels and tools with the thermal and mechanical behaviour of the parts during bonding is one major part to gain deeper insight and knowledge for diffusion-bonding friendly design and processing. The data will be used for a tooling design framework, which can be used for several new developments without long-term fundamental research. A validation and data gathering will be carried out by the means of bonding samples up to large sizes with varying design and manufacturing history, generating broad experimental data for up-scaling tasks. Microstructural changes will be analysed and set into relation with the simulations and applicatory requirements.