Iron casting during Industrialization

The development of new technologies and an increased demand for cast parts gave tremendous impulses to the metal casting industry during the second half of the eighteenth century.

The artistic design of iron casts was not only limited to the creation of decorative objects but was also used for the production of machine parts and articles of daily use.

Casting and art work

From the early beginning to present day, metal casting has been used to create works of art.

Expendable mold casting

Expendable mold casting is a generic classification that includes sand, plastic, shell, and investment (lost-wax technique) moldings. This method of mold casting involves the use of temporary, nonreusable molds.

Sand casting

Sand casting requires a lead time of days for production at high output rates (1-20 pieces/hr-mold), and is unsurpassed for large-part production. Green (moist) sand has almost no part weight limit, whereas dry sand has a practical part mass limit of 2300-2700 kg. The sand is bonded together using clays (as in green sand) or chemical binders, or polymerized oils. Sand in most operations can be recycled many times and requires little additional input.

Plaster casting (of metals)

Plaster casting is similar to sand molding except that plaster is substituted for sand. Plaster compound is actually composed of 70-80% gypsum and 20-30% strengthener and water. Generally, the form takes less than a week to prepare, after which a production rate of 1-10 units/hr-mold is achieved with items as massive as 45 kg and as small as 30 g with very high surface resolution and fine tolerances.

Shell molding

Shell molding is also similar to sand molding except that a mixture of sand and 3-6 percent resin holds the grains together. Set-up and production of shell mold patterns takes weeks, after which an output of 5-50 pieces/hr-mold is attainable. Aluminium and magnesium products average about 13.5 kg as a normal limit, but it is possible to cast items in the 45-90 kg range. Shell mold walling varies from 3-10 mm thick, depending on the forming time of the resin.

There are a dozen different stages in shell mold processing that include:

1. initially preparing a metal-matched plate
2. mixing resin and sand
3. heating pattern, usually to between 505-550 K
4. inverting the pattern (the sand is at one end of a box and the pattern at the other, and the box is inverted for a time determined by the desired thickness of the mill)
5. curing shell and baking it
6. removing investment
7. inserting cores
8. repeating for other half
9. assembling mold
10. pouring mold
11. removing casting
12. cleaning and trimming.

Investment casting

Investment casting (lost-wax process) yields a finely detailed and accurate product, but mechanical properties are not good since the process involves slow cooling.

Polystyrene foam is also used in investment casting—see lost-foam casting.

After a variable lead time, usually weeks, 1–1000 pieces/hour-mold can be produced in the mass range 2.3–2.7 kg. Items up to 45 kg and as light as 30 g are possible for unit production.

die will be used to inject wax to create the patterns needed for investment casting. The patterns are attached to a central wax sprue, creating an assembly, or mold. The sprue contains the fill cup where the molten metal will be poured into the assembly.