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Die casting is an efficient way to mass-produce a wide variety of engineered metal parts. This guide will discuss the different types of die casting machines, as well as potential considerations for manufacturers purchasing a die casting machine.
The manufacturing technique known as die casting typically employs high pressure to force molten metal into mold cavities (or “dies”) where the metal cools and hardens into its final form. Usually manufacturers use non-ferrous metals, such as zinc, aluminum, lead, copper, or tin to fabricate die cast parts.
While tooling and startup for a die casting operation can be expensive, the cost may be offset by its rapid production rate and reduced downtime between manufacturing runs. Other major benefits of die casting include:
Versatility: A wide range of materials can be die cast, depending on the casting machine’s configuration.
Reliability: Die casting produces durable, uniform products.
Easy assembly: Complex fasteners or attachment devices can be included in the final component.
Variety of surface textures: The process is capable of delivering smooth or textured part surfaces.
There are two main types of die casting machines: hot-chamber and cold-chamber. Hot-chamber machines (or “gooseneck machines,” due to the shape of their metal feeding system) have a pressure chamber connected directly to the mold cavity, allowing the continuous flow of molten metal into the pressurized compartment. When the chamber’s cylinder reverts to an unpressurized position, molten metal is fed into the casting die. The process is a rapid one, and is generally faster than its cold-chamber equivalent.
Cold-chamber die casting machines require molten metal to be hand-ladled or automatically ladled into the chamber. Afterward, a hydraulically operated plunger seals off the pressure compartment and forces the metal into a die. These machines minimize the amount of heat, reducing the chance of corrosion in the plunger and its associated components.
Because hot-chamber machines are more susceptible to corrosion, they are more efficient for metals and alloys with a low melting temperature and reasonable fluidity. Common hot-chamber die casting metals include copper, lead, zinc, and magnesium.
Due to its reduced chance of corrosion, a cold-chamber process is better suited to casting high melting-point metals. Cold-chamber die casting machines are recommended when working with aluminum or alloys with a high aluminum content.
Hot- and cold-chamber casting machines can be further divided into subcategories. Some of the more specialized die casting machines used in certain applications include:
Semi-solid molding machines: These machines create semi-solid metal billets effective for low porosity and heat-treatable applications.
Squeeze casting machines: Squeeze casting is another method for creating low porosity, heat-treatable components that reduce gas entrapment and turbulence.
Although most die casting machines have automation capabilities, more advanced (and expensive) machines can automate almost all steps in the casting process, including lubrication of dies, trimming, quenching, and, in the case of cold-chamber casting, ladling. Automation may also reduce the level of manual quality control if coupled with a processing device that analyzes and adjusts the casting process based on hydraulic pressure or metal velocity.
Die casts are a necessary component of any die casting machine. The four most common types of die cast are:
Single-cavity die: This type of die is good for creating solid, uni-body components.
Multiple-cavity die: These dies can produce several identical components at once.
Unit die: A type of die useful for simultaneously casting several different components.
Combination die: These are effective for casting numerous unique parts for future assembly.
To offset high startup and integration costs, some manufacturers use plastic injection-molded dies. While this dramatically reduces the strength and corrosion resistance of the die, it is a relatively cost-effective solution for fabricating products with low hardness or durability requirements. In addition, optional die casting features, such as modular nozzles and spray heads that eliminate fluid loss, can reduce waste and potentially save money in the long run.
