Page 16 - Module DMV20173

2.0 CASTING PROCESSES

Figure 2.6 Schematic illustration of the expendable pattern casting process.

5. The evaporative-pattern process has a number of advantages over other casting
methods:

a) Simple process because there are no parting lines, cores, or riser systems.
b) Flexibility design because polystyrene can be processed easily into patterns
in complex shapes, various sizes, and fine surface detail.

c) Inexpensive flasks.
d) The casting requires minimal finishing and cleaning operations.
e) The process can be automated and is economical for long production runs.

6. Some of the limitations of the evaporative-pattern casting consist of:
a) High cost to produce the die used for expanding the polystyrene beads.
b) The need of many tooling preparations.

2.4.6 INVESTMENT CASTING

1. The investment-casting process, also called the lost-wax process.
2. A variation of the investment-casting process is ceramic-shell casting.
3. Fig. 3.7 shows the schematic illustration of the investment casting (lost-wax) process.
4. The evaporative-pattern process has a number of advantages over other casting

methods:
a) Can produce fine and detail products.
b) It is suitable for casting high-melting-point alloys.
c) Good surface finishes.
d) Close dimensional tolerances.

e) Economical because of few or no finishing operations.
5. However, the mould materials and labor involved increase the cost of investment-

casting.
BPLK 48 DMV 20173