LOAM MOULD AND ITS MAKING

Loam is clay and sand mixed with water to form a thin plastic mixture from which molds are made. Loam sand also contains fire clay or ganisters. The loam must be sufficiently adhesive so that it can cling to the vertical surfaces. Loam molds always require special provision to secure adequate ventilation. The object is to open out pores in the otherwise compact, closely knit mass, by artificial means. Thus various kinds of organic matter such as chopper straw, and particularly horse manure, is mixed up with the sand . A typical loam sand mixture is ,

1. Silica - 22 %

2. Clay - 5 %

3. Coke - 10 %

4. Moisture - 18-20 %

This is applied as plaster to the rough structure of the mold usually made of brickwork and the exact shape is given by a rotating sweep around a central spindle.

Cast iron plates and bars are used to reinforce the brickwork which retains the molding material. Loam molds may also be prepared by use of a skeleton pattern made of wood. The surfaces of loams are blackened and are dried before the assembled.

Loam molds are employed chiefly in the making of large castings for which it would be too expensive to use full patterns and ordinary flask equipment. Objects such as large cylinders , round-bottomed kettles, chemical pans, large gears, and other machine parts are produced in loam molds.

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