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Shell Moulding

Shell moulding is a process for producing castings. It forms a mould from resin-bonded sand mixtures brought in a contact with preheated (300-500 F, 148.89-260 C) metal patterns, resulting in a firm shell with a cavity corresponding to the outline of the pattern. The moulds may have walls from ½” to 3/8” thick, hence called, shell. It is a method for making high quality castings, maintaining tight tolerances and a high degree of dimensional stability. These qualities of precision can be obtained in a wide range of alloys.


Shell moulding is a variation of sand moulding. The mould is formed of a thin shell of special sand. The shell is formed by coating a hot metal pattern with resin impregnated sand. The heat melts the resin which then holds the grains of sand together forming a shell.


Shell moulding process is employed when a large number of same casting is needed. Shell mouldings are usually made with machines. Material of shell mouldings usually has much higher melting point than the molten metal poured in it. It protects the moulding against melting. Due to this reason, one shell mould can be used many times and thus reduces the overall castings production cost.


Darcast is using high precision metal patterns for shell moulding for extra durability. Due to this we can provide best quality shell moulding on relatively lower cost. The high precision metal patterns used in shell moulding are expensive but they are durable and reduce the unit costs of the moulds when produced in large numbers. They also allow better control of shape and size than conventional sand casting and produce castings with a smoother surface which reduces the cost of finishing.


Darcast has four state-of-the-art medium frequency electric melting furnaces capable of producing over 100,000 tonnes of base iron per annum. The Company converts the base iron produced in the electric melting furnaces into spheroidal graphite iron using shell moulding. Darcast utilises the shell-moulded process to manufacture its mould.


Given below are details of the historical roots of the shell-moulded process, the reasons why Darcast selected this technology as the most appropriate for crankshaft manufacturing and the advantages the shell-moulded process offers to customers. Overall, the shell-moulding process provides customers with the best quality crankshafts and the lowest total cost solution.


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