Process Encyclopaedia

Overview

• Developed in the early 1900s, this is the most common of the casting processes that use a permanent mould.
• It is used for high volume products, of which small zinc die-cast toys (e.g. "Matchbox" cars) are probably the most widely known.
• Very small components like zipper teeth can be made at over 20,000 an hour!

Variants:

Ferro-die is used for high melting point materials such as steels. It uses higher melting point ferrous alloys for the die materials and is more expensive.

Process details

Materials and shapes

• Mostly used for low melting point alloys such as aluminium, zinc and copper. In general only small parts are made, but it can be used for components up to 25kg.
• Complex parts can be made with good dimensional accuracy and surface detail.
• A draft (taper) angle has to be incorporated to alloy easy ejection of the part.
• Parts are left with good mechanical surface properties.
• Ejector pin marks are often visible.

Economics

• The machinery is expensive, and can cost well over £100,000.
• Dies cost many thousand pounds and need to be replaced after a few hundred thousand uses. They can take several weeks to manufacture, mean prototype testing is slow.
• The production rate depends on how long the part takes to cool before it can be ejected. This can give rates of 500+ parts per hour in normal conditions.
• Because of the high capital cost, the process is only economic for batches of 100,000+

Typical products

• Small toys e.g. cars/soldiers
• hand tools
• disc drive chassis
• motor casings
• carburettors

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