< THE POURING CUP
THE METAL FEEDING & VENTING SYSTEM
It is quite possible on occasion, to attach a POURING CUP directly to a simple wax pattern and use this as the only means of both feeding the investment mould with molten metal and venting displaced air and evolved gases. In practice though, very few of the designs cast in art foundries are suited to such a simplistic treatment. Instead, the founder usually attaches a far more sophisticated network of FEEDER tubes and vents. These tubes are designed to direct metal to remote sections of the mould, sections which might not fill if the molten charge only enters the cavity at a single point at the top of the mould. Vents or RISERS prevent the entering charge from compressing air into trapped pockets in the mould, this could create a back pressure which might in turn prevent the charge from filling affected areas. The vents also enable gases released during the pour to escape from the mould.
In the United States and some other countries including Canada, Australia and New Zealand, the metal running system is often referred to as the SPRUE SYSTEM, in Britain the term SPRUE is usually only used to describe the casting attachment placed on a small jewellery pattern – most art founders use the terms ‘runner’ and ‘riser’ to distinguish between the metal feed and gas vent attachments. Given the terms RUNNER and RISER are self explanatory, we will follow that convention here, reserving the term SPRUE for jewellery type processes.
RUNNERS >
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