MAS 2.0 - Guides - F.A.Q. - Tutorials - Home

More Information

The die-casting process, developed in the early 1900s, is a further example of permanent-mold casting. The weight of most casting ranges from less than 90 grams to about 25 kilograms.

Hot-chamber process

The hot-chamber process involves the use of a piston, which traps a certain volume of molten metal and forces it into the die cavity through a gooseneck and nozzle. The pressures range up to 35 MPa, with an average of about 15 MPa. The metal is held under pressure until it solidifies in the die. To improve die life and to aid in rapid metal cooling, thus reducing cycle time, dies are usually cooled by circulating water or oil through various passageways in the die block. Cycle times usually range up to 900 shots (individual injections) per hour for zinc, although very small components such as zipper teeth can be cast at 18,000 shots per hour. Low-melting point alloys such as zinc, tin, and lead are commonly cast by this process.

Cold-chamber process

In the cold-chamber process molten metal is introduced into the injection cylinder. The shot chamber is not heated -- hence the term cold chamber. The metal is forced into the die cavity at pressures usually ranging from 20 MPa to 70 Mpa, although they may be as high as 150 MPa. The machines may be horizontal or vertical; in the latter the shot chamber is vertical and the machine is similar to a vertical press.

High-melting-point alloys of aluminum, magnesium, and copper are normally cast by this method, although other metals (including ferrous metals) can also be cast in this manner. Molten metal temperature start at about 600 degrees Celsius for aluminum and magnesium alloys and increase considerably for copper-base and iron-base alloys.

Source: Kalpakjian, Manufacturing Processes for Engineering Materials.