Direct metal laser sintering: Rebuild, don’t replace

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“In general, laser welding is very good for repairing damaged corners, edges or thin layer defects when there is no need to add to the material’s volume,” says Lubos Rozkosny, managing director of Innomia (innomia.cz). “When it’s more suitable to add material volume to repair the damaged area, DMLS is very efficient. It can bring material back to the exact 3D geometry specified by the part’s 3D model. This is not possible using laser welding because the process is manually controlled. DMLS can because the laser beam is computer-controlled by the CAD file.”

Melting layers of metal powders from the bottom up

In general, DMLS works by melting very fine layers of metal powders from the bottom up until the build is complete, creating a single homogeneous part made of steel. To start, a thin layer of pure tool steel powder material is applied to the building platform. A powerful laser beam then fuses the powder at exactly the points defined by the computer-generated component design data. The platform is then lowered and another layer of powder is applied. Once again the material is fused so as to bond with the layer below at the predefined points. When it comes to insert repair, however, DMLS has a different approach. “You don’t repair the inserts by welding together two broken or damaged parts,” explains Daniel Kundig, owner and managing director of Ecoparts (ecoparts.ch). “Instead, you completely rebuild the damaged area of the insert. This ensures a homogeneous microstructure in the parts, without having visible weld lines on the repaired insert.” After the DMLS process, inserts can be post-processed (for example, via milling or polishing), as required. The insert’s functionality is saved and reestablished.

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Metals used in DMLS offer good mechanical properties

DMLS melts material back onto the damaged area, and metals used in DMLS offer very good mechanical properties, Rozkosny says. For example, MS11.2709 maraging steel offers a hardness ranging to 54 HRc. (Heat treatment can be used to adjust the hardness between 34 and 54 HRc.)

In addition, different tool steels can be combined, limited only by the size of the sintered surface and weldability of the materials. DMLS also runs in an airtight chamber under an inert nitrogen atmosphere, ensuring a very good metal structure. Finally, it offers short lead times and suitable quality, Rozkosny says.

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