Dimensionally Accurate Mold Inserts and Metal Components by Direct Metal Laser Sintering
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45 Mat. Res. Soc. Symp. Proc. Vol. 625 © 2000 Materials Research Society
Conventionally the structure is built to be as strong as possible which is not the optimal way: The mechanical requirements of the mold depend on the size of the series to be produced as well as on the material to be molded or cast. Therefore, in order to save time and energy, the material properties of the mold should be tailored to withstand only as much strain as necessary. In addition, the strongest material should be deposited only where it is needed based on known stresses inside the mold. Material research started at Rapid Product Innovations already in the late eighties. The research was first focused on pressureless furnace sintering of metal powders [1]. The objective was to produce net-shape metal molds for injection molding with the assistance of a negative mold pattern.Using a special powder mixture that did not shrink during furnace sintering proved to be the best solution for the process. After finding a suitable mixture [2] the need for a more flexible process was evident and a European RP machine manufacturer EOS GmbH was contacted. The result was a co-operation agreement and the first generation bronze-based powder was developed especially for the Direct Metal Laser Sintering (DMLS) process in 1995 [3,4]. In 1996 the powder as well as the machine were released to commercial use. The next step was to develop new powders. In addition to bronze-based powder with smaller layer thickness (50 jim), a completely new steel-based powder was introduced in 1998 [5]. This was also the first time when direct laser sintering of steel powder was possible. The properties of these materials can be seen in Table I. Combining process control with the non-shrinking behavior of the powder mixture [6,7] has one remarkable outcome: the sintered Table I. Selected materialpropertiesof commercially available DMLSpartso ae: sinet-ped materials. *DirectMetaland DirectSteel are trademarksof EOS GmbH, Germany. parts are net-shape.m The surfaces require TM M DirectMetal 100-V3 DirectMetal50-V2* DirectSteel' 50-V1* minor post-processing after the sintering and Layer 50 pm 50 pm 100 prm special thickness with precautions the Main dimensional accuracy constituent Bronze Bronze Steel is retained even with 2 2 2 < 500 N/mm
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