Centrifugal casting and investment casting are metal casting processes. In centrifugal casting, molten metal is poured into a rotating mold and centrifugal force throws the metal against the mold wall. Investment casting involves creating a wax pattern, coating it with ceramic slurry to create a mold, melting out the wax, and pouring molten metal into the mold. Both processes allow creating complex metal parts with good dimensional accuracy and surface finish. Common applications include pipes, bearings, turbine blades, and firearm components.

1. Gandhinagar Institute
of Technology(012)
Subject : Manufacturing Process - II
(2141908)
Active Learning Assignment
Branch : Mechanical
Batch : 4 A / 4A3
Prepared by : - Jain Bhavesh (160120119032)
Guided By: Prof. Naman Dave
Topic Name:
“Centrifugal Casting & Investment Casting”

2. CENTRIFUGAL CASTING
In this process molten metal is poured in the mould and allowed to solidify
while the mould is rotating. Metal is poured into the centre of the mould at its
axis of rotation.
Due to centrifugal force the liquid metal is thrown out towards the
periphery.

3.  Mould Material
 Steel
 Cast Iron
 Graphite
 Sand
 Rotation Speed of Centrifugal Mould about 1000
rpm
 A Centrifugal Casting Machine.

4. A CENTRIFUGAL CASTING MACHINE

5. PROCEDURE
1)The Mould wall is coated with a refractory ceramic
coating (applying Ceramic Slurry , spinning, dying,
baking).
2)Starting rotation of the mould at a pre determined
speed.
3)Pouring of Molten metal directly into the mould (no
gating system is employed).
4)The mould is stopped after the casting has been
solidified.
5)Extraction of the casting from the mould.

6. CHARACTERISTICS OF
CENTRIFUGAL CASTING
1) The casting is relatively free from defects.
2) Non metallic impurities which segregate toward the bore can be machined off.
3) Less loss of metal in tundish compared to that in gating and risering in conventional
and sand casting.
4) Better mechanical properties.
5) Production rate is high.
6) Can be employed to manufacture bimetallic pipes.
7) Centrifugal casting process can be used for fabricating functionally gradient metal
matrix composite material.

7. DEFECTS IN THE
CENTRIFUGAL CASTING
Conventional static casting defects like internal shrinkage, gas porosity
and nonmetallic inclusions are less likely to occur in centrifugal
casting.
Hot Tears – Hot tears are developed in centrifugal castings for which
the highest rotation speeds are used. Longitudinal tears occur when
contraction of casting combined with the expansion of the
mould, generates hoop stresses exceeding the cohesive strength of the
metal at temperatures in the solidus region.
Segregation - Centrifugal castings are under various forms of
segregation thus pushing less dense constituents at centre.
Banding – Sometimes castings produce zones of segregated low
melting point constituents such as eutectic phases and sulphide and
oxide inclusions. Various theories explain this, one states vibration is
the main cause of banding.

8. APPLICATIONS OF
CENTRIFUGALCASTING
Pipes for water gas sewage.
Bearing Bushes.
Cylinder Liners.
Piston rings
Paper making rollers
Clutch Plates.
Pulleys.

9. SOME CENTRIFUGAL CASTINGS

10. Mould Rolle
r
Mould
Cover
Rotameter
Tundish
Water Nozzles
CENTRIFUGALCASTING SET UP

11. • Investment casting is an industrial process and it is also
called lost-wax casting . This is one of the oldest known
metal- forming techniques from 5000 years ago.
• This castings allow the production of components with
accuracy, repeatability, versatility and integrity in a variety
of metals and high-performance alloys.
• It is generally more expensive per unit than die casting or
sand casting, but has lower equipment costs.
Investment Casting

12. PROCESS:
Moldmaking:
The first step in investment casting is to manufacture the wax pattern for the process.
A mold , known as the master die, is made of the master pattern. The master pattern
may be made from a low-melting-point metal, steel, or wood. Rubber molds can also
be cast directly from the master pattern.
Produce the wax patterns:
The pattern for this process may also be made from plastic; however it is often made of
wax
since it will melt out easily and wax can be reused.

13. Assemble the wax patterns:
The wax pattern is then removed from
the mold . Depending on
the application multiple wax patterns may be created so that they can all be cast at
once. In other applications, multiple different wax patterns may be created and then
assembled into one complex pattern. The multiple patterns are attached to a wax
sprue, and then it make a tree. Finally it is
dressed, which means any other imperfections are addressed so that the wax now
looks like the finished piece.

14. Investment:
•The metal casting pattern is then dipped in a refractory slurry whose
composition includes extremely fine grained sand, water and binders. A
ceramic layer is obtained over the surface of the pattern. The pattern is then
repeatedly dipped into the slurry to increase the thickness of the ceramic
coat.

15. Dewax & burnout:
The investment is then allowed to
completely dry, which can take 16 to 48
hours . Drying can be enhanced by applying
a vacuum or minimizing the environmental
humidity. Most shell failures occur at this
point because the waxes used have a thermal
expansion
Coefficient., so as the wax is heated it
expands and induces great stresses. The mold is then subjected to a
burnout, which heats the mold between 870 °C and 1095 °C to remove
any moisture and residual wax, and to sinter the mold.

16. Pouring:
The investment mold is then placed cup-upwards into a tub filled with sand but
if there are thin sections in the mold it may be filled by applying positive air
pressure or pressure assisted Pouring. Then after pouring the
mold is left for cooling.
Removal:
The shell is hammered, vibrated, water jeted , or chemically dissolved to release
the casting. The sprue is cut off and recycled.

17. ADVANTAGES OF INVESTMENT CASTING:
• Many Intricate forms with undercuts can be cast.
• A very smooth surface is obtained with no parting line.
• Dimensional accuracy is good.
• Certain unmachinable parts can be cast to preplanned
shape.
• It may be used to replace die-casting where short runs are
involved.
• With this casting we can get the exact shape of the
pattern.

18. DISADVANTAGES OF INVESTMENT
CASTING:
• This process is expensive, is usually limited to
small casting, and presents some difficulties where
cores are involved.
• Holes cannot be so small.
• Investment castings require very long production-
cycle times versus other casting processes.
• This process is practically infeasible for high-
volume manufacturing, due to its high cost and
long cycle times.

19. APPLICATION:
• Investment casting is used in the aerospace and
power generation industries to produce turbine
blades with complex shapes or cooling systems.
• Investment casting is also widely used by firearms
manufacturers to fabricate firearm receivers, triggers,
hammers, and other precision parts at low cost.
• Industries that use standard investment-cast parts
include military, medical, commercial and
automotive.