< SLUSHING
WAX INJECTION
Injecting wax into reproduction moulds is generally associated with precision and high volume jewellery casting processes. Both of these industries usually make use of either vulcanised rubber (block moulds), or metal die moulds for producing waxes (see REPRODUCTION MOULDING).
The entrance of the die is designed to locate and lock into a spigot, which in turn is connected to a sealed reservoir of molten, pressurised wax. Set between the spigot and the reservoir is a valve which upon activation, releases a quantity of wax. The valve is usually activated by pushing the die (secured within clamps), into the spigot. This forces wax under pressure into the die cavity. When the die is released from the spigot the valve closes isolating the wax reservoir.
Unlike the brushed on or slushed wax techniques previously described, which produce hollow reproductions, the deposited wax in a die usually creates a solid wax pattern. Consequently, most of the wax patterns created by this process are suitable manufacturing small, solid metal designs only. Hollow casts can be formed by a wax injection process, either by joining a number of individually injected wax patterns together as a constructed ‘kit’, or alternatively, by incorporating a preformed refractory core into the die cavity prior to wax injection. The core remains in the wax pattern throughout the investment process until cleaned out after casting.
Waxes used in die injection process are generally much harder and have shorter melting ranges than those waxes used for slushed and brushed on art foundry work. The wax is often blended to contract minimally upon cooling, and therefore retain dimensional accuracy. This level of stability is an essential quality given the high degree of precision demanded by the jewellery and engineering industries.
WORKING WITH WAX PATTERNS >
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