Investment Casting

Investment casting is also known as the lost wax process. Investment casting process is one of the oldest manufacturing processes.

Closer tolerance control
Fewer or no machining allowance
Good surface finish

Benefits of Investment casting:
1.Intricate shapes can be made with high accuracy.
2. metals that are hard to machine or fabricate are good candidates for this process. 3. It can be used to make parts that cannot be produced by normal manufacturing techniques, such as turbine blades that have complex shapes, or airplane parts that have to withstand high temperatures.

The types of materials that can be cast are Aluminum alloys, Bronzes, tool steels, stainless steels, Stellite, Hastelloys, and precious metals. Parts made with investment castings often do not require any further machining, because of the close tolerances that can be achieved.

Investment casting, often called lost wax casting, is regarded as a precision casting process to fabricate near-net-shaped metal parts from almost any alloy. Although its history lies to a great extent in the production of art, the most common use of investment casting in more recent history has been the production of components requiring complex, often thin-wall castings. While a complete description of the process is beyond the scope of the discussion here, the sequential steps of the investment casting process will be briefly described, with emphasis on casting from rapid prototyping patterns.

The investment casting process begins with fabrication of a sacrificial pattern with the same basic geometrical shape as the finished cast part (Fig. 10.1a). Patterns are normally made of investment casting wax that is injected into a metal wax injection die. Fabricating the injection die often costs tens of thousands of dollars and can require several months of lead time. Once a wax pattern is produced, it is assembled with other wax components to form a metal delivery system (Fig. 10.1b), called the gate and runner system. The entire wax assembly is then dipped in a ceramic slurry, covered with a sand stucco (Fig. 10.1c), and allowed to dry. The dipping and stuccoing process is repeated until a shell of ~6-8 mm (1/4-3/8 in) is applied.