Hot and Cold Chamber Die casting

Hot and Cold Chamber Die casting Die casting is one of the most common manufacturing processes. The basic idea is to force metal into a permanent mold using high pressure. The metal then cools (often assisted by water cooling of the die). The mold is then opened, and the casting ejected.
Molds for die casting are quite elaborate. They are usually constructed of alloy steel in two pieces (called the cover and the ejector). The die must withstand high temperature and pressure, so the die is typically made for chromium or tungsten steel alloys. In order to increase die life, and improve throughput, the die is usually cooled with water, air or nitrogen.

Materials:

Materials best suited for die castings are zinc, aluminum, magnesium, copper, lead and tin. High pressure die casting is generally limited to non-ferrous metals because of the difficulty in making refractory molds capable of withstanding the high temperature and pressure.

Applications:

- automotive parts
- appliances
- office machines
- bathroom fixtures
- outboard motors

Hot chamber machines are:

- good for low temperature zinc alloys (approx. 400°C)
- faster than cold chamber machines
- cycle times must be short to minimize metal contamination
- metal starts in a heated cylinder
- a piston forces metal into the die
- the piston retracts, and draws metal in

Cold chamber machines:

- casts high melting point metals (>600°C)
- high pressures used
- metal is heated in a separate crucible
- metal is ladled into a cold chamber
- the metal is rapidly forced into the mold before it cools

Advantages:

• intricate parts possible
• short cycles
• inserts feasible
• cycles less than 1 minute
• minimum finishing operations
• thin sections, high tolerances, good surface finish

Disadvantages:

• metal die is costly
• porous parts
• not suited to large parts
• long setup times
• $5000-200,000 for machine
• metal melting point temperature must be lower than die