Process Encyclopaedia

Overview

Essentially, this process is forging for polymers - although only one 'hit' is possible. Mainly used for thermosets and rubbers in mid-size batches as injection moulding is cheaper for thermoplastics. With thermosets, the chemical reaction provides most of the heat, so little extra energy is required.

Process details

Materials and shapes

Mainly used for thermosets, although rubbers, some thermoplastics and chopped-fibre composites can be formed this way. Limited to simple shapes, although a wider variety is possible with rubbers as they can be more easily removed from the mould. Possible part size range from 10mm up to 1m. Waste material, called flash, needs to be removed after moulding and is not readily recycled.

Economics

Cycle time is limited by heat transfer, or curing time and is usually over 1 minute. Production rate can be increased by using multiple cavity moulds. Equipment cost is low compared to similar processes - about £10,000 - £50,000. Die cost a few thousand pounds, and need replacing after 10-50,000 uses. The low production rate means that it is only usually economic for batch sizes in the tens of thousands.

Typical products

Dishes, handles, caps, electrical components.

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