Fraunhofer ILT 3D prints locally permeable metal parts

Researchers at the Fraunhofer Institute for Laser Technology (ILT) have developed a method that can be used to additively and precisely process metallic materials so that they not only are locally permeable or dense – with graded transitions between the states – but can be manufactured reproducibly and in a single production step.

The newly developed method is based on LPBF. Until now, the focus has been on producing components that are as dense and resilient as possible. “But if we allow porosity locally, for example, by changing the process parameters, we can create controlled permeability,” said Andreas Vogelpoth from the LPBF Process and Systems Engineering group at Fraunhofer ILT.

The result is completely metallic components that are locally permeable – such as to gases or liquids – while still maintaining the required mechanical integrity. The trick is that areas with different densities can be combined within one component thanks to LPBF. The institute can make transitions either with a sharp separation or a graded separation.

Classic metal foams or fabric structures fulfill similar functions, but usually have to be produced separately and incorporated into components. Not only does this take time, but limits the design freedom and leads to changes in the physical properties of the component due to seams and joints (for example, an increase in thermal and electrical resistance). The Fraunhofer solution integrates porous zones directly into the component. Thus, post-processing is not necessary. Even complex geometrical shapes with internal structures can be made in this way.

“We are adding new functions to parts made with 3D printing: permeability as a designable feature,” said Vogelpoth. The process is particularly interesting wherever gases or liquids need to be distributed, filtered, or channeled in a controlled manner.

A key area of application is hydrogen technology, specifically for electrolyzers. These consist of complex cell stacks with various functional layers. Fraunhofer ILT is currently investigating whether these layers can be additively manufactured directly, including specific permeable areas. The experts at Fraunhofer ILT aim to reduce the number of individual parts – improving efficiency while reducing material usage and production costs.

Porous areas can be reproduced reliably, which the researchers have already demonstrated using computer tomography and cross-sections. They are currently working on the next step as part of a research project: the precise control of permeability via process parameters.

“Our plan is for users to tell us how much permeability is required in which component areas, and we will supply the appropriate design and process parameters,” said Vogelpoth.

The Fraunhofer ILT team is also already in contact with end users in other areas of applications such as turbomachinery, toolmaking, heat exchangers, and filters, as well as chemicals. The wide range of possible applications underlines how relevant this development is for high-tech applications.

In contrast to other players who are already investigating similar processes in turbomachinery construction, Fraunhofer ILT is pursuing an open, cross-application approach. It aims to make the process accessible for new fields of application, especially for small and medium-sized companies that previously had no access to such complex manufacturing methods.