Challenge

Additive manufacturing has quickly developed into an alternative manufacturing method for many applications. However, as the choice of materials that can be used is limited, there are applications for which it has not yet been proven that conventional processes can be replaced. This applies, for example, to the metallic material Invar. It has an extremely small thermal expansion and is available in powder form, but so far there have been no systematic analyses of the extent to which it can be used to manufacture components with minimized thermal expansion in 3D metal printing. There are also open questions about biocompatible materials for hearing aids. The required geometries have so far been produced by machining with high manual effort; complex geometries are not feasible. In addition, hearing aids are one-offs because of the users' individual auditory canals. Using an additive manufacturing process could not only reduce the effort but also enable the implementation of new, user-oriented functions.

Goals and procedure

Two goals are to be achieved with the 3DPraekomMed project: In the AtheK subproject, components are to be additively manufactured that exhibit virtually no thermal expansion. To this end, topology optimization methods and the finite element method will be used to design defined structures of the material Invar with minimal thermal expansion. Optimizations for the material and the manufacturing process are then developed and tested on cube-shaped samples.

In the SmartVent subproject, 3D printing is being used to develop new moulded fittings for hearing aids (earmold geometries) that will increase the efficiency of hearing systems. They will enable ventilation of the ear while maintaining the functionality of adaptive parameters of digital hearing aid signal processing. To this end, demonstrators are being developed that will first be tested on an artificial head. The knowledge gained in this process will be transferred to the fabrication of biocompatible resins and tested by volunteers.

Innovations and perspectives

The 3DPraekomMed project aims to create solutions for two applications for which only costly or unsatisfactory processes have been available to date. At present, temperature-critical applications still require complex cooling; in the case of hearing aids, subsequent adjustments can only be carried out by acousticians. Both solutions are special insofar as the desired functionality of the components is largely enabled by the additive manufacturing process, the design of the geometries and the smart materials.

The results of AtheK could, for example, be used directly in applications with high dimensional accuracy requirements, such as high-precision drives. Due to the improved wearing comfort and increased efficiency of hearing aids, for example in a noisy environment, SmartVent will increase the acceptance of hearing systems. Later on, the results could be used for the development of electrically controllable ventilation.