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Additive Manufacturing 18 MoldMaking Technology July 2015 18 MoldMaking Technology July 2015 Rebuild, Don't Replace By Christina Fuges Repairing damaged mold inserts is a growth area for additive manufacturing. Conventional repair processes can require multiple steps and be time-consuming. Welding, for example, requires cutting out the broken or worn area, fixing a new block of steel, performing the welding and completely re- machining the insert. It also can involve secondary operations such as machining, polishing or testing, and it has limitations, such as the durability of the repair. The need for faster, more economical ways to repair mold inserts has opened the door for direct metal laser sintering (DMLS). Rather than replacing damaged tools, this additive process can be used to quickly repair only the damaged areas, resulting in simplified repair, decreased downtime, longer operating life, and reduced costs associated with maintenance and repair. Ecoparts and Innomia are two companies that now offer customers the speed and cost advantages of DMLS tool repair. Innomia provides plastic and metal part design and develop- ment using reverse engineering, 3D scanning and additive manufacturing. Ecoparts is an EOS service provider that pro- duces prototypes, short runs and tool inserts, as well as hot runner water-cooled gate inserts, for the mold and die and mechanical engineering industries. "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. "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." In general, DMLS works by melting very fine layers of metal powders and building those melted layers up to create a single, homogenous part. Specificially, a thin layer of pure tool steel powder is applied to the building platform. A powerful laser beam then fuses the powder at exactly the points defined by the computer-generated design. The platform is then lowered, and another layer of powder is applied. Once again the mate- rial is fused to the layer below at the predefined points. For insert repair, DMLS takes a somewhat different approach. "You don't repair the inserts by welding together two broken or damaged parts," explains Daniel Kundig, owner and manag- ing director of Ecoparts. "Instead, you completely rebuild the damaged area of the insert. This ensures a homogeneous micro- structure in the parts, without having visible weld lines on the repaired insert." After DMLS, inserts can be post-processed as needed, and the insert's functionality is reestablished. Metals used in DMLS offer very good mechanical properties, Mr. 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 addi- tion, 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 nitro- gen atmosphere, ensuring structural strength. Finally, it offers short lead times and suitable quality, Mr. Rozkosny says. Innomia and Ecoparts do see a few limitations to using DMLS, however: (1) machine chamber size (250 x 250 x 325 mm) limits the size of parts that can be repaired; (2) surface finish is rough (about 10 Ra), usually requiring conventional finishing processes; (3) the layer-by-layer process demands a flat surface; and (4) only one material (1.2709) currently is approved for tooling. However, the high accuracy and surface quality after finishing that DMLS offers make it an ideal platform for tool- ing applications, including tool repair. Also, inserts repaired using DMLS are proving to prolong tool life. Both Innomia and Ecoparts have seen growing demand for the use of DMLS to repair mold inserts, as it simplifies and speeds the repair process. In most cases, this alternative to completely remanufacturing an insert saves weeks in produc- tion time. FOR MORE INFORMATION: Ecoparts / ecoparts.ch Innomia / innomia.cz Pages 13 to 18 Images courtesy of Ecoparts. After repair with direct metal laser sintering (right image), the functionality of the damaged mold insert shown in the top image was restored.