Plaster molding
The decision to make fine casts with investment casting is made when stringent requirements in terms of surface quality must be fulfilled and when it is necessary to fabricate filigree structures with thin walls or if almost unlimited styling options are desired. Some casting geometries cannot be made with any other procedures, or if they can be, only with great effort. Using the plaster molding procedure, it is no problem to handle large undercuts and missing drafting angles.
Masters are made on a scale corresponding to material shrinkage directly from the 3D-blank data. These might be, for instance, stereolithography, laser-sintered plastic- or models made by LOM.
The master is the basis for making one or more (if necessary) silicone tools able to represent even the most complicated geometries by multiple splitting.
Wax casting in a vacuum and cooling of the filled silicone cavity under defined conditions guarantee high accuracy and perfect surfaces of the emerging wax pattern. It is possible to produce up to 25 wax patterns with one silicone mold. Thus, tool costs for prototyping can be further reduced.
Each wax pattern is built with a gate and feeder system in a wax cluster and is recast in a cell in a vacuum with mineral molding material. By mounting a direct cooling, the casting engineer may affect the later material characteristics of the prototype even at this step of the process chain. The prepared cell is now dried in the burnout furnace and molten out.
As an alternative to the wax model, one may use plotted wax patterns or lost masters of polystyrene. These master variants provide a solution in cases where prototypes could otherwise be made only by means of ceramic cores or highly complicated split pieces.
After drying and hardening of the casting mold have been completed, it is possible to begin pouring all established aluminum- and zinc alloys.
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