2. Learning Objectives
• At the end of session, student must be familiar
with;
– Concept of manufacturing & its processes
– Concept of casting & its uses
– Concept of Pattern, Core, Mold
– Stages in sand casting
– Advantages & disadvantages
3. Manufacturing Processes
• Conversion of raw material into a finished
product as per the specifications given by the
designer
• They are broadly classified as;
– Castings [Sand, Shell, Die, Centrifugal]
– Metal removal[Turning, Drilling, Milling, Grinding]
– Deformation [Forging, Rolling, Extrusion, Drawing]
– Joining [Welding, Soldering, Brazing, Fittings]
4. Casting
• A mold is formed into the
geometric shape of a desired
part.
• Molten metal is then poured
into the mold, the mold holds
this material in shape as it
solidifies, called as casting
• Terms used;
– Pattern
– Core
– Mold
– Casting
5. Pattern Making
• It’s a replica of Casting to be produced.
• The solid form that is used to make the mould
• Pattern has to be designed to facilitate
moulding and ensure good quality castings.
• A poor casting may result from a good pattern
due to various other factors but a poor
pattern would never make a good casting.
• The design of the pattern depends upon the
shape and complexity of the casting, the
material of the pattern, the type of moulding
adopted and the number of castings to be
produced.
• Material: Wood, Plastics or metals –
Aluminum, Steel.
• Types: Solid, Match plate, Cope & drag
6. Cope & Drag Pattern
• The cope and drag pattern is a two
piece pattern representing the
casting and divided at the parting
line.
• Each of the two halves are
mounted on a plate for easy
alignment of the pattern and mold.
• The cope and drag pattern enables
the cope section of the mold, and
the drag section of the mold to be
created separately and latter
assembled before the pouring of
metal.
7. Core Making
• Cores form the internal geometry of
a casting.
• They are placed in the mold &
remain there during the metal
pouring phase of the manufacturing
process
• The metal casting will solidify
around the core
• Cores are made of the highest
quality sand and are subject to
extreme conditions during the
casting operation
• Once the metal casting has
hardened the core is broken up and
removed much like the mold
8. Sand Casting
• Widely used casting process in manufacturing.
• Almost all the metals can be sand cast.
• Simple, complex & large enough castings.
• Sand: Silica sand (SiO2
)
• It is inexpensive & is very resistant to elevated
temperatures
• Mixture: 90% Sand, 6% Clay & 4% Water
• Engine blocks, machine tool bases, cylinder heads,
pump housings, and valves etc.
9. Stages involved in Sand Castings
• The drag of pattern is placed on the board
• Dry facing sand is sprinkled over the board and pattern to provide a
non sticky layer.
• Molding sand is then riddled into cover the pattern with the
fingers; then the drag is completely filled.
• The sand is firmly packed in the drag by means of hand rammers.
• After ramming, the excess sand is leveled off.
• Using vent rod, vent holes are made in the drag to facilitate the
removal of gases during pouring.
• The finished drag flask is now rolled over to the bottom board
exposing the pattern.
10. Stages involved in Sand Castings
• The cope of pattern is placed over the board.
• Dry facing sand is sprinkled over the board and pattern to
provide a non sticky layer.
• A sprue & riser pin is located at a small distance from the
pattern.
• The operation of filling, ramming and venting of molding
sand on the cope proceed in the same manner as performed
in the drag.
11. Stages involved in Sand Castings
• The sprue and riser pins are removed first & a pouring basin is
scooped out at the top to pour the liquid metal.
• Then patterns from the cope and drag is removed
• Facing sand in the form of paste is applied all over the mold
cavity and runners which would give a good surface finish to the
finished casting.
• The mold is now assembled & is now ready for pouring metal
• Molten metal is then poured into the mold, the mold holds this
material in shape as it solidifies, called as casting
12. Advantages of Casting Process
• Size of cast objects vary over large range - from 5 gm to 200
ton, anything can be cast.
• Complexity: Very complex shaped objects
• Weight Saving: Component made with casting process is
lighter than the component made with other machining
processes.
• Wide range of properties can be attained by adjusting
percentage of alloying elements.
• Accuracy: Casting can be made like hair, provided proper
molding and casting precision technique are employed.
13. Advantages of Casting Process
• Fibrous Structure: Casting leaves component with its solid
fibrous structure which inherit great compressive strength,
e.g. IC engine cylinder
• Control Over Grain Size: Grain size of cast component can be
easily controlled by controlling cooling rate which in turn can
be used to modify the properties.
• Low Cost: Casing is one of cheapest method for mass
production.
14. Disadvantages of Casting Process
• Though casting is cheapest for MASS Production, it
becomes non economical in case of JOB production.
• Sand casting leaves rough surface which needs
machining in most of cases. It adds up the cost in
production.
• Poor dimensional accuracy is achieved.
• Cast products are superior for compressive loads but
they are very poor in tensile or shock loads. (They are
brittle).
