The jolt moulding has been used since 1869 (a US patent). The principle of this method is illustrated in Figure. A pattern plate with a pattern assembly is fastened to the machine table. A moulding box along with a filling frame is located on the guide pins of the pattern plate, which are subsequently filled with the moulding aggregate. Then the machine starts the jolt operation by applying the air pressure to the jolt piston, which causes the machine table to lift for a few centimetres (depending on the setting). After the piston has reached the position, the compressed air escapes through the outlet hole, and the piston, together with the machine table carrying the pattern assembly and moulding box, drops down under its own weight against the stand stop, producing a sharp jolt. The shock is largely absorbed by the moulding box assembly. This process is repeated for a certain number of times. The action of raising and dropping is called ‘jolting’.
a) lower position of the piston, b) upper position of the piston;
1 – filling frame, 2 – moulding box /flask, 3 – pattern plate, 4 – machine table,
5 – outlet hole, 6 – jolt piston, 7 – compressed air supply