The document discusses three metal casting processes: sand casting, die casting, and shell mold casting. It provides details on the process steps for each, including mold making, pouring molten metal, cooling, and removing the final casting. Sand casting can be used for ferrous and non-ferrous metals. Die casting is suited for producing complex non-ferrous metal parts through reusable molds. Shell mold casting utilizes a sand-resin mixture to create a thin-walled mold and is capable of ferrous and non-ferrous metals.

1. ASSIGNMENT-3
Identify and study manufacturing processes. Select two for
a)Ferrous b)Non-ferrous c) Plastics
•Collect details regarding a) accuracy and finish achieved by manufacturing
processes
b) Scale of operation suitable for the process
SAND CASTING: This process is used for both ferrous and Non-ferrous metals
The process cycle for sand casting consists of six main stages, which are explained below.
1.Mold-Making: The first step in the sand casting process is to create the mold for the
casting. In an expendable mold process, this step must be performed for each casting. A
sand mold is formed by packing sand into each half of the mold. The sand is packed around
the pattern, which is a replica of the external shape of the casting. When the pattern is
removed, the cavity that will form the casting remains. Any internal features of the casting
that cannot be formed by the pattern are formed by separate cores which are made of sand
prior to the formation of the mold. Further details on mold-making will be described in the
next section. The mold-making time includes positioning the pattern, packing the sand, and
removing the pattern. The mold-making time is affected by the size of the part, the number
of cores, and the type of sand mold. If the mold type requires heating or baking time, the
mold-making time is substantially increased. Also, lubrication is often applied to the
surfaces of the mold cavity in order to facilitate removal of the casting. The use of a
lubricant also improves the flow the metal and can improve the surface finish of the
casting. The lubricant that is used is chosen based upon the sand and molten metal
temperature.

2. ASSIGNMENT-3
Sand casting overview :
2.Clamping : Once the mold has been made, it must be prepared for the molten metal to be
poured. The surface of the mold cavity is first lubricated to facilitate the removal of the
casting. Then, the cores are positioned and the mold halves are closed and securely
clamped together. It is essential that the mold halves remain securely closed to prevent the
loss of any material.
3.Pouring : The molten metal is maintained at a set temperature in a furnace. After the
mold has been clamped, the molten metal can be ladled from its holding container in the
furnace and poured into the mold. The pouring can be performed manually or by an
automated machine. Enough molten metal must be poured to fill the entire cavity and all
channels in the mold. The filling time is very short in order to prevent early solidification of
any one part of the metal.
4.Cooling:The molten metal that is poured into the mold will begin to cool and solidify once
it enters the cavity. When the entire cavity is filled and the molten metal solidifies, the final
shape of the casting is formed. The mold can not be opened until the cooling time has
elapsed. The desired cooling time can be estimated based upon the wall thickness of the
casting and the temperature of the metal. Most of the possible defects that can occur are a
result of the solidification process. If some of the molten metal cools too quickly, the part
may exhibit shrinkage, cracks, or incomplete sections. Preventative measures can be taken
in designing both the part and the mold and will be explored in later sections.
5.Removal: After the predetermined solidification time has passed, the sand mold can
simply be broken, and the casting removed. This step, sometimes called shakeout, is

3. ASSIGNMENT-3
typically performed by a vibrating machine that shakes the sand and casting out of the
flask. Once removed, the casting will likely have some sand and oxide layers adhered to the
surface. Shot blasting is sometimes used to remove any remaining sand, especially from
internal surfaces, and reduce the surface roughness.
6.Trimming: During cooling, the material from the channels in the mold solidifies attached
to the part. This excess material must be trimmed from the casting either manually via
cutting or sawing, or using a trimming press. The time required to trim the excess material
can be estimated from the size of the casting's envelope. A larger casting will require a
longer trimming time. The scrap material that results from this trimming is either discarded
or reused in the sand casting process. However, the scrap material may need to be
reconditioned to the proper chemical composition before it can be combined with non-
recycled metal and reused.
Capabilities of Sand Casting:

4. ASSIGNMENT-3
Die Casting: for Non-Ferrous metals
It is a manufacturing process that can produce geometrically complex metal parts through
the use of reusable molds, called dies. The die casting process involves the use of a furnace,
metal, die casting machine, and die. The metal, typically a non-ferrous alloy such as
aluminium or zinc, is melted in the furnace and then injected into the dies in the die casting
machine. There are two main types of die casting machines - hot chamber machines (used
for alloys with low melting temperatures, such as zinc) and cold chamber machines (used
for alloys with high melting temperatures, such as aluminium). The differences between
these machines will be detailed in the sections on equipment and tooling. However, in both
machines, after the molten metal is injected into the dies, it rapidly cools and solidifies into
the final part, called the casting
The process cycle for die casting consists of five main stages, which are explained
below
 Clamping
The first step is the preparation and clamping of the two halves of the die. Each die half is
first cleaned from the previous injection and then lubricated to facilitate the ejection of the
next part. The lubrication time increases with part size, as well as the number
of cavities and side-cores. Also, lubrication may not be required after each cycle, but after 2
or 3 cycles, depending upon the material. After lubrication, the two die halves, which are
attached inside the die casting machine, are closed and securely clamped together. Sufficient
force must be applied to the die to keep it securely closed while the metal is injected. The
time required to close and clamp the die is dependent upon the machine - larger machines
(those with greater clamping forces) will require more time. This time can be estimated from
the dry cycle time of the machine.
 Injection
The molten metal, which is maintained at a set temperature in the furnace, is next transferred
into a chamber where it can be injected into the die. The method of transferring the molten
metal is dependent upon the type of die casting machine, whether a hot chamber or cold
chamber machine is being used. The difference in this equipment will be detailed in the next
section. Once transferred, the molten metal is injected at high pressures into the die. Typical
injection pressure ranges from 1,000 to 20,000 psi. This pressure holds the molten metal in
the dies during solidification. The amount of metal that is injected into the die is referred to
as the shot. The injection time is the time required for the molten metal to fill all of the
channels and cavities in the die. This time is very short, typically less than 0.1 seconds, in
order to prevent early solidification of any one part of the metal. The proper injection time
can be determined by the thermodynamic properties of the material, as well as the wall
thickness of the casting. A greater wall thickness will require a longer injection time. In the
case where a cold chamber die casting machine is being used, the injection time must also
include the time to manually ladle the molten metal into the shot chamber.

5. ASSIGNMENT-3
Die cast part
 Cooling
The molten metal that is injected into the die will begin to cool and solidify once it enters the
die cavity. When the entire cavity is filled and the molten metal solidifies, the final shape of
the casting is formed. The die can not be opened until the cooling time has elapsed and the
casting is solidified. The cooling time can be estimated from several thermodynamic
properties of the metal, the maximum wall thickness of the casting, and the complexity of the
die. A greater wall thickness will require a longer cooling time. The geometric complexity of
the die also requires a longer cooling time because the additional resistance to the flow of
heat.
 Ejection
After the predetermined cooling time has passed, the die halves can be opened and an
ejection mechanism can push the casting out of the die cavity. The time to open the die can
be estimated from the dry cycle time of the machine and the ejection time is determined by
the size of the casting's envelope and should include time for the casting to fall free of the
die. The ejection mechanism must apply some force to eject the part because during cooling
the part shrinks and adheres to the die. Once the casting is ejected, the die can be clamped
shut for the next injection.
 Trimming
During cooling, the material in the channels of the die will solidify attached to the casting.
This excess material, along with any flash that has occurred, must be trimmed from the
casting either manually via cutting or sawing, or using a trimming press. The time required
to trim the excess material can be estimated from the size of the casting's envelope. The
scrap material that results from this trimming is either discarded or can be reused in the die
casting process. Recycled material may need to be reconditioned to the proper chemical
composition before it can be combined with non-recycled metal and reused in the die casting
process.

6. ASSIGNMENT-3
Capabilities of Die-Casting:

7. ASSIGNMENT-3
SHELL MOLD CASTING: Ferrous &Non-Ferrous metals
Shell mold casting is a metal casting process similar to sand casting, in that molten metal is
poured into an expendable mold. However, in shell mold casting, the mold is a thin-walled
shell created from applying a sand-resin mixture around a pattern. The pattern, a metal
piece in the shape of the desired part, is reused to form multiple shell molds. A reusable
pattern allows for higher production rates, while the disposable molds enable complex
geometries to be cast. Shell mold casting requires the use of a metal pattern, oven, sand-
resin mixture, dump box, and molten metal.
Shell mold casting allows the use of both ferrous and non-ferrous metals, most commonly
using cast iron, carbon steel, alloy steel, stainless steel, aluminum alloys, and copper alloys.
Typical parts are small-to-medium in size and require high accuracy, such as gear housings,
cylinder heads, connecting rods, and lever arms.
The shell mold casting process consists of the following steps:
Pattern creation : A two-piece metal pattern is created in the shape of the desired part,
typically from iron or steel. Other materials are sometimes used, such as aluminum for low
volume production or graphite for casting reactive materials.
Mold creation : First, each pattern half is heated to 175-370°C (350-700°F) and coated with
a lubricant to facilitate removal. Next, the heated pattern is clamped to a dump box, which
contains a mixture of sand and a resin binder. The dump box is inverted, allowing this sand-
resin mixture to coat the pattern. The heated pattern partially cures the mixture, which
now forms a shell around the pattern. Each pattern half and surrounding shell is cured to
completion in an oven and then the shell is ejected from the pattern.
Mold assembly: The two shell halves are joined together and securely clamped to form the
complete shell mold. If any cores are required, they are inserted prior to closing the mold.
The shell mold is then placed into a flask and supported by a backing material.
Pouring: The mold is securely clamped together while the molten metal is poured from a
ladle into the gating system and fills the mold cavity.
Cooling: After the mold has been filled, the molten metal is allowed to cool and solidify into
the shape of the final casting.
Casting removal: After the molten metal has cooled, the mold can be broken and the
casting removed. Trimming and cleaning processes are required to remove any excess
metal from the feed system and any sand from the mold.

8. ASSIGNMENT-3
Capabilities of shell mold casting: