Casting – is the process of manufacturing castings, filling the mold with molten material (foundry alloys, plastics, some of the rocks), and further processing of post-curing products.

In the most common sand casting foundry it is produced a model (previously – wood, now it is often used plastic models, obtained by rapid prototyping) are copied to a future item. The model is filled with sand or sand mixture (usually sand and binder) that fills the space between it and the two open boxes (mold). Holes in the parts are formed with the help of foundry sand cores that replicate the shape of future openings. The mixture poured in a flask is sealed of shaking, pressing or cures in thermal oven (drying oven). The cavities are filled with molten metal through the holes – gate. After cooling form is broken and casting is extracted. Then the gating system is separated, heat treatment is conducted.

Rapid Prototyping Technologies are used in Lost Wax Casting, in cases of manufacture of parts of high-precision (eg turbine blades, etc.) from the fusible material: paraffin wax, stearin, etc. (in the simplest case – made of wax) produced an exact model of the product and gating system. The most widespread is a model P50S50 consisting of 50% stearin and 50% paraffin, for big products it is used salt mixture that less prone to warping. Then the model is dipped into a liquid suspension through the binder and the refractory filler. As a binder it is used hydrolyzed ethyl silicate ETS 32 and ETS 40, the hydrolysis is carried out in an acid solution, water and solvent (ethanol, acetone).

As the refractory filler it is used: electro corundum, distensilimanit, quartz, etc. On the model unit (and LPS) they cause the suspension and make short crust or cause of 6 to 10 layers. With each subsequent the layer of the grain of fraction short crust change for the formation of dense surface of the shell mold. Drying of each layer is not less than an hour, to accelerate the process it is used special drying cabinets, in which ammonia gas is injected. Then the model is smelted: in water, in the model structure, burning, steam pressure. After drying and sweat the block is heated at a temperature of about 1000 for the removal of the shell mold substances capable of gassing. After that the shells are filled. Before filling the blocks are heated in kilns to 1000. The heated block is placed in the oven and heated metal is poured into the shell. Filled block is cooled in the thermostat or air. When the unit is fully cooled, it is sent to the knockout.

Because of the large consumption of metal and high cost of LVC, it is used only for main parts.

The process of investment casting is based on the following general principles:

• A copy or model of the final product is made of low-melting material.

• This model is surrounded by ceramic mass, which hardens and forms a shape.

• When heating the model of the casting form is melted and removed.

• Then in the remaining on-site remote wax cavity is filled with metal, which reproduces accurately the original model casting.

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