Additive Manufacturing Porous Structures from the Metal 3D Printer

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Researchers at the Fraunhofer Institute for Laser Technology ILT have developed a method that allows metallic materials to be additively processed to be locally permeable or dense, with graded transitions in between, high precision, reproducibility, and in a single manufacturing step.

The newly developed method is based on the Laser Powder Bed Fusion (LPBF) process, where metal powder is applied layer by layer and selectively melted with a laser. So far, the focus has been on producing parts that are as dense and strong as possible. "But if we deliberately allow local porosity—for example, by changing process parameters—we can create controlled permeability," explains Andreas Vogelpoth from the LPBF Process and System Technology Group at Fraunhofer ILT.

The result is fully metallic components that are locally permeable—for example, for gases or liquids—while still maintaining the required mechanical integrity. The trick: Different density areas can be combined within a component using the LPBF process. The transitions can be realized either sharply or graded.

Integrate Porous Zones Directly into the Component

Classic metal foams or fabric structures serve similar functions but usually need to be manufactured separately and incorporated into components. This is time-consuming, limits design freedom, and leads to changes in the physical properties of the component due to seams and joints, such as increased thermal and electrical resistance. The Fraunhofer solution integrates porous zones directly into the component. Post-processing is not necessary. Even complex geometries with internal structures can be realized this way.

“We are introducing a new functionality to 3D printing—permeability as a designable feature,” explains Vogelpoth. The process is particularly interesting wherever gases or liquids need to be distributed, filtered, or guided in a controlled manner.

Gallery

The production of the porous areas is reliably reproducible, as researchers have already demonstrated with computed tomography and cross-sections. The next step is currently being worked on as part of a research project: the precise control of permeability via process parameters.

“Our plan is for users to tell us in the future which permeability is needed in which component area—and we will deliver the appropriate design and process parameters,” says Vogelpoth.

One central area of application is hydrogen technology, specifically electrolyzers. These consist of complex cell stacks with various functional layers. Fraunhofer ILT is currently investigating whether these layers can be produced directly using additive manufacturing, including targeted permeable areas. The aim is to reduce the number of individual parts, thereby improving efficiency, material use, and production costs.

Unlike other players who are already investigating similar processes in turbomachinery, Fraunhofer ILT pursues an open, cross-application approach. The goal is to make the process accessible for new fields of—especially for medium-sized companies that previously had no access to such complex manufacturing methods.

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