About Die Casting

Die Casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. 

The casting equipment and the metal dies represent large capital costs and this tends to limit the process to high-volume production. Manufacture of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It is especially suited for a large quantity of small- to medium-sized castings, which is why die casting produces more castings than any other casting process. Die castings are characterized by a very good surface finish (by casting standards) and dimensional consistency.

Advantages

Advantages of die casting:

• Excellent dimensional accuracy (dependent on casting material, but typically 0.1 mm for the first 2.5 cm (0.004 inch for the first inch) and 0.02 mm for each additional centimeter (0.002 inch for each additional inch).

• Smooth cast surfaces (Ra 1–2.5 micrometres or 0.04–0.10 thou rms).

• Thinner walls can be cast as compared to sand and permanent mould casting (approximately 0.75 mm or 0.030 in).

• Inserts can be cast-in (such as threaded inserts, heating elements, and high strength bearing surfaces).

• Reduces or eliminates secondary machining operations.

• Rapid production rates.

• Casting tensile strength as high as 415 megapascals (60 ksi).

• Die casting fluid length is unaffected by solidification range, unlike permanent molds, sand castings, and other types.

• Corrosion rates for die castings are slower than those for sand castings due to the smoother surface of the die castings.

Disadvantages

The main disadvantage to die casting is the very high capital cpst.Both the casting equipment required and the dies and related components are very costly, as compared to most other casting processes. Therefore, to make die casting an economic process, a large production volume is needed. Other disadvantages are:

• The process is limited to high-fluidity metals. Increased scrap rates can be caused by fluidity failure, and scrap costs in die casting are high.

• Die casting involves a large number of parts, so questions of repeatability are particularly important.

• In the standard die casting process the final casting will have a small amount of porosity. This prevents any heat treating or welding, because the heat causes the gas in the pores to expand, which causes micro-cracks inside the part and exfoliation of the surface.