Important casting terms

.Flask: A metal or wood frame, without fixed top or bottom, in which the mould is formed.
Depending upon the position of the flask in the moulding structure, it is referred to by
various names such as drag – lower moulding flask, cope – upper moulding flask, cheek –
intermediate moulding flask used in three piece moulding. Pattern: It is the replica of the
final object to be made. The mould cavity is made with the help of pattern. Parting line: This
is the dividing line between the two moulding flasks that makes up the mould. Moulding
sand: Sand, which binds strongly without losing its permeability to air or gases. It is a
mixture of silica sand, clay, and moisture in appropriate proportions. Facing sand: The small
amount of carbonaceous material sprinkled on the inner surface of the mould cavity to give
a better surface finish to the castings. Important casting terms NPTEL course on
Manufacturing processes – I, Pradeep Kumar et al.

J S Campbell, Principles Of Manufacturing Materials And Processes

R.Ganesh Narayanan, IITG Core: A separate part of the mould, made of sand and generally
baked, which is used to create openings and various shaped cavities in the castings. Pouring
basin: A small funnel shaped cavity at the top of the mould into which the molten metal is
poured. Sprue: The passage through which the molten metal, from the pouring basin,
reaches the mould cavity. In many cases it controls the flow of metal into the mould.
Runner: The channel through which the molten metal is carried from the sprue to the gate.
Gate: A channel through which the molten metal enters the mould cavity. Chaplets: Chaplets
are used to support the cores inside the mould cavity to take care of its own weight and
overcome the metallostatic force. Riser: A column of molten metal placed in the mould to
feed the castings as it shrinks and solidifies. Also known as “feed head”. Vent: Small opening
in the mould to facilitate escape of air and gases.

R.Ganesh Narayanan, IITG The six basic steps in making sand castings are, (i) Pattern
making, (ii) Core making, (iii) Moulding, (iv) Melting and pouring, (v) Cleaning Pattern
making - Pattern: Replica of the part to be cast and is used to prepare the mould cavity. It is
the physical model of the casting used to make the mould. Made of either wood or metal.

-The mould is made by packing some readily formed aggregate material, such as moulding
sand, surrounding the pattern. When the pattern is withdrawn, its imprint provides the
mould cavity. This cavity is filled with metal to become the casting.

- If the casting is to be hollow, additional patterns called ‘cores’, are used to form these
cavities.
Steps in making sand castings

R.Ganesh Narayanan, IITG Core making Cores are placed into a mould cavity to form the
interior surfaces of castings. Thus the void space is filled with molten metal and eventually
becomes the casting. Moulding Moulding is nothing but the mould preparation activities for
receiving molten metal. Moulding usually involves: (i) preparing the consolidated sand
mould around a pattern held within a supporting metal frame, (ii) removing the pattern to
leave the mould cavity with cores.

Mould cavity is the primary cavity.

The mould cavity contains the liquid metal and it acts as a negative of the desired product.

The mould also contains secondary cavities for pouring and channeling the liquid material
in to the primary cavity and will act a reservoir, if required. R.Ganesh Narayanan, IITG
Melting and Pouring The preparation of molten metal for casting is referred to simply as
melting. The molten metal is transferred to the pouring area where the moulds are filled.
Cleaning Cleaning involves removal of sand, scale, and excess metal from the casting.
Burned-on sand and scale are removed to improved the surface appearance of the casting.
Excess metal, in the form of fins, wires, parting line fins, and gates, is removed. Inspection of
the casting for defects and general quality is performed. R.Ganesh Narayanan, IITG Making a
simple sand mould

1)The drag flask is placed on the board

2)Dry facing sand is sprinkled over the board

3)Drag half of the pattern is located on the mould board. Dry facing sand will provide a non-
sticky layer.

4)Molding sand is then poured in to cover the pattern with the fingers and then the drag is
filled completely

5)Sand is then tightly packed in the drag by means of hand rammers. Peen hammers (used
first close to drag pattern) and butt hammers (used for surface ramming) are used.

6) The ramming must be proper i.e. it must neither be too hard or soft. Too soft ramming
will generate weak mould and imprint of the pattern will not be good. Too hard ramming
will not allow gases/air to escape and hence bubbles are created in casting resulting in
defects called ‘blows’. Moreover, the making of runners and gates will be difficult.

7) After the ramming is finished, the excess sand is leveled/removed with a straight bar
known as strike rod. R.Ganesh Narayanan, IITG
8) Vent holes are made in the drag to the full depth of the flask as well as to the pattern to
facilitate the removal of gases during pouring and solidification. Done by vent rod.

9) The finished drag flask is now made upside down exposing the pattern.

10) Cope half of the pattern is then placed on the drag pattern using locating pins. The cope
flask is also located with the help of pins. The dry parting sand is sprinkled all over the drag
surface and on the pattern.

11) A sprue pin for making the sprue passage is located at some distance from the pattern
edge. Riser pin is placed at an appropriate place.

12) Filling, ramming and venting of the cope is done in the same manner. R.Ganesh
Narayanan, IITG 13) The sprue and riser are removed and a pouring basin is made at the
top to pour the liquid metal. 14) Pattern from the cope and drag is removed. 15) Runners
and gates are made by cutting the parting surface with a gate cutter. A gate cutter is a piece
of sheet metal bent to the desired radius. 16) The core for making a central hole is now
placed into the mould cavity in the drag. Rests in core prints. 17) Mould is now assembled
and ready for pouring.