Sand casting

A brief process description

Casting is a forming technique. A fluid material becomes a firm object after solidifying. Workpieces are cast, if they require specific properties which would make the manufacture by some other means economically unviable or simply impossible.  Workpiece casting can be used equally well for either bulk production or individual parts.
The point of departure for sand casting is models of the end product. The models are made up of one or more parts wood, synthetic resin, plastic, steel, aluminum, rigid foam or styrofoam. Due to the fact that dimension changes can occur with the casting technique (also known as shrinkage), depending on casting temperature, contour, and density during the form-cooling process, this variable must be anticipated and taken into account for the model construction. In the next step, the model is placed in the appropriate mold box, and the mold box is filled with foundry sand and compressed. At this time, the feeder is positioned, through which the molten metal will later be cast. By removing the model after hardening (for this purpose, a special hardener is mixed into the foundry sand), a negative from of the desired workpiece is created. The mold boxes are subsequently fixed together and prepared for casting on the swiveling table.

At the same time, the individual components of the desired alloy are combined together. Precisely weighed, the individual elements - this can be shavings or chunks - are placed into the smelter on the electric furnace. There they are heated slowly to the pre-determined smelting temperature. The molten alloy is transported to the sand mold in a crucible and poured slowly into the form via the feeder. At the same time, the swiveling table including the form is tipped so the alloy flows into the hollow cavities slowly, and with as few vortices as possible. The feeder also serves as a material reservoir. If the workpiece begins to shrink during the cooling process, the reservoir adds material and fills out the  hollow cavities again. After the final cooling of the form, which depending on the size can take several days, the foundry sand is knocked out, the casted workpiece is exposed and prepared for further processing or inspection.