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Author Dr.- Ing. Florian Wendt, Dipl.-Ing. Ray Wünsche, ACTech GmbH, Am St.Niclas-Schacht 13, 09599 Freiberg/Sa Germany; Wendt@actech.de
Source Rapid Prototyping & Manufacturing 2000
Abstract The Direct Croning (R) Process is an application-specific development of the well-known laser-sintering technique that has been used for several years for plastic powder. The Direct Croning (R) Process is named after the moulding sand used in this process which is very similar to conventional croning sand. This moulding material has been applied in foundries for a long time and the resulting casting quality is well known. The mould segments and cores produced by using the Direct Croning (R) Process on EOSINT-S show completely the same characteristics and quality as conventionally produced sand castings. Therefore, castings produced with the Direct Croning (R) Process are perfect to serve as functional prototypes of later series production of sand castings because the same alloy and melting, gating and rising technology is applied.
In case of using the Direct Croning (R) Process on EOSINT-S to produce sand moulds and cores ready for casting a hot curing moulding material is needed. After applying a flat, uniform 0.2mm thick layer of this material the particles are fused together by a laser beam. The energy of the laser beam initiates an exothermal chemical reaction which bounds the sand particles together. After hardening the moulding material on this way the production table is lowered and the next layer is applied. This process operates fully automatic and without any operator interaction through all of the layers. Parts with a bigger volume than 720 x 380 x 380mm are typically produced in segments and sometimes combined with exterior patterns made by any Rapid Tooling technologies.
The first dimension check is already made when assembling the mould segments at the casting location. If all segments fit together and can be assembled without any problems, the sand mould device has the right dimensions. The first visual check is followed by standard procedures as is usual for casting prototypes and the last dimension and properties checking in the laboratory. XX