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11.4.2 Classification of Moulding Machines
Foundry Tools and Equipments 205
The large variety of molding machines that are available in different designs which can be
classified as squeezer machine, jolt machine, jolt-squeezer machine, slinging machines, pattern
draw machines and roll over machines. These varieties of machines are discussed as under.
11.4.2.1 Squeezer machine
These machines may be hand operated or power operated. The pattern is placed over the
machine table, followed by the molding box. In hand-operated machines, the platen is lifted
by hand operated mechanism. In power machines, it is lifted by the air pressure on a piston
in the cylinder in the same way as in jolt machine. The table is raised gradually. The sand
in the molding box is squeezed between plate and the upward rising table thus enabling a
uniform pressing of sand in the molding box. The main advantage of power operated machines
in comparison hand operated machines is that more pressure can be applied in power operated.
11.4.2.2 Jolt machine
This machine is also known as jar machine which comprises of air operated piston and
cylinder. The air is allowed to enter from the bottom side of the cylinder and acts on the
bottom face of the piston to raise it up. The platen or table of the machine is attached at the
top of the piston which carries the pattern and molding box with sand filled in it. The upward
movement of piston raises the table to a certain height and the air below the piston is
suddenly released, resulting in uniform packing of sand around the pattern in the molding
box. This process is repeated several times rapidly. This operation is known as jolting technique.
11.4.2.3 Jolt-squeezer machine
It uses the principle of both jolt and squeezer machines in which complete mould is
prepared. The cope, match plate and drag are assembled on the machine table in a reverse
position, that is, the drag on the top and the cope below. Initially the drag is filled with sand
followed by ramming by the jolting action of the table. After leveling off the sand on the upper
surface, the assembly is turned upside down and placed over a bottom board placed on the
table. Next, the cope is filled up with sand and is rammed by squeezing between the overhead
plate and the machine table. The overhead plate is then swung aside and sand on the top
leveled off, cope is next removed and the drag is vibrated by air vibrator. This is followed by
removal of match plate and closing of two halves of the mold for pouring the molten metal.
This machine is used to overcome the drawbacks of both squeeze and jolt principles of
ramming molding sand.
11.4.2.4 Slinging machines
These machines are also known as sand slingers and are used for filling and uniform
ramming of molding sand in molds. In the slinging operations, the consolidation and ramming
are obtained by impact of sand which falls at a very high velocity on pattern. These machines
are generally preferred for quick preparation of large sand moulds. These machines can also
be used in combination with other devices such as, roll over machines and pattern draw
machines for reducing manual operations to minimum. These machines can be stationary and
portable types. Stationary machines are used for mass production in bigger foundries whereas
portable type machines are mounted on wheels and travel in the foundry shop on a well
planned fixed path. A typical sand slinger consists of a heavy base, a bin or hopper to carry
sand, a bucket elevator to which are attached a number of buckets and a swinging arm which