Selective LED based Melting (SLEDM) – the targeted melting of metal powder using high-performance LED light sources – is the name of the new technology that a team around the head of the Institute for Manufacturing Technology at Graz University of Technology Franz Haas is developing for 3D metal printing has now applied for a patent. The technology is similar to Selective Laser (SLM, Selective Laser Melting) or Electron Beam Melting (EBM, Electron Beam Melting), in which metal powder is melted using a laser or electron beam and built up in layers to form a component. However, SLEDM eliminates two central problems of this powder bed-based manufacturing process: the time-consuming production of large-volume metal components and the time-consuming manual reworking.

Shortened production time

Unlike the SLM or EBM process, the metal powder is melted with a high-performance LED beam in the SLEDM process. The light-emitting diodes used for this were specially adapted by the West Styrian lighting specialist Preworks and equipped with a complex lens system with which the diameter of the LED focus can be easily changed between 0.05 and 20 millimeters during the melting process. This enables larger volumes to be melted per unit of time without having to do without filigree internal structures and thus reduces the production time of components, for example for fuel cell or medical technology, by a factor of 20.

Tedious post-processing is no longer necessary

This technology is combined with a newly designed production system, which – in contrast to other metal melting systems – assembles the component from top to bottom. The component is thus exposed, the amount of powder required is reduced to a minimum and the necessary post-processing can already be carried out during the printing process. “The time-consuming, usually manual reworking that is required in current processes to smooth rough surfaces and remove support structures is eliminated and saves further valuable time,” said Haas.

Franz Haas heads the Institute of Manufacturing Technology at Graz University of Technology and is the brain behind the 3D printing method SLEDM. © Photo Furgler

Areas of application and other plans

A demonstrator of the SLEDM process is already included in the K project CAMed of the Medical University of Graz , where the first laboratory for medical 3D printing was opened in October 2019. The process is intended to produce bioresorbable metal implants – in other words, preferably screws that are made of magnesium alloys and are used for broken bones. These implants dissolve in the body after the fracture has grown together. A second operation, which is often very stressful for people, is no longer necessary. Thanks to SLEDM, it would be possible to produce such implants directly in the operating room, because “an LED light is naturally less dangerous for operating theater than a powerful laser source,” says Haas.

The second focus is on sustainable mobility, namely in the manufacture of components such as bipolar plates for fuel cells or components for battery systems. “We want to make additive manufacturing using SLEDM economically usable for e-mobility and position SLEDM in this research area at an early stage,” says Haas, who will produce a marketable prototype of this 3D metal printer – “made by TU Graz” in the next development step: a another novelty in the university environment.

The SLEDM process was developed in the FoE “Mobility & Production” , one of five strengths at Graz University of Technology.

At the TU Graz, various research groups are working on additive manufacturing processes. Information on the topic can be found in the e-paper edition of our research magazine TU Graz research: The 3D Revolution