Casting is a manufacturing process where liquid material is poured into a mold and allowed to solidify. The solidified part is known as a casting. Investment casting, also known as lost-wax casting, involves creating a wax pattern, coating it with refractory material to create a ceramic mold, melting away the wax to leave a cavity, and pouring molten metal into the mold cavity. This allows for very intricate parts to be cast with close tolerances and smooth finishes. Investment casting is commonly used for parts that are difficult to machine from difficult to machine alloys like aluminum, copper, and steels.

1. CASTINGS
 Casting is a manufacturing process in which a liquid material is
usually poured into a mould, which contains a hollow cavity of
the desired shape, and then allowed to solidify.
 The solidified part is also known as a casting, which is ejected or
broken out of the mould to complete the process.
 Casting materials are usually metals or various cold
setting materials that cure after mixing two or more components
together,
examples are epoxy, concrete, plaster and clay.
 Casting is most often used for making complex shapes that would
be otherwise difficult or uneconomical to make by other methods.
 Casting is a 6000-year-old process.
 The oldest surviving casting is a copper frog from 3200 BC.

2. Die casting
 Die casting is a widespread non-expendable technique the which
metal are forced into the mold cavity under high pressure.
 Die casting mold that are known as dies can be used repeatedly to
produce castings in a variety of sizes, shapes and wall thickness.
 The mold cavities are designed with intricate designs that enables
in producing complex shapes with accuracy, surface finish and
attractiveness.
 Today, the die casting process is constantly getting refined by
improving the alloys and the casting process.

3. Process:
 In the die casting process molten metal or other materials are
forced, under high pressure into the cavities of the steel mold.
 Dies are two part molds that are made of alloy tool steel. The fixer
die half and the ejector die half.
 The die or mold is fabricated with the impression of the
component that is to cast.
 The molten metal is injected into the die under high pressure and
high speed, which helps in producing a casting that is smooth and
precise as the original mold. The pressure is maintained on the
mold until the hot metal solidifies. When the metal is hardened, the
die is opened to remove the casting

4. There are four types of dies:
 Single cavity to produce one component
 Multiple cavity to produce a number of identical parts
 Unit die to produce different parts at one time
 Combinations die to produce several different parts for an
assembly

6. Die casting:
Advantages:
 Good dimensional tolerances are possible
 Excellent part-part dimensional consistency
 Parts require a minimal post machining
 Post machining can be totally eliminated
 A process that can be fully automated
Disadvantages:
 Economical only in very large quantities due to high tool cost
 Not recommended for hydrostatic pressure applications
 For Castings where penetrant (die) or radiographic inspection are not required.
 Difficult to guarantee minimum mechanical properties

7. Die casting application
 Die casting is most suitable for casting medium sized parts with
complex details.
 Die-casting is the largest casting technique that is used to
manufacture consumer, commercial and industrial products like
automobiles, toys, parts of sink faucet, connector housing, gears,
etc.
 Most die castings are done from non-ferrous metals like
aluminum, magnesium, etc.

8. Centrifugal casting
 Centrifugal casting or roto casting is a casting Technique that is
typically used to cast thin-walled cyclinders.
 It is used to cast such materials as metal, glass, and concrete.
 Its noted for the high quality of the results attainable,
particularly for precise control of their metallurgy and crystal
structure.
 It’s chiefly used to manufacture stock materials in standard sizes
for further machining, rather than shaped parts tailored to a
particular end-use.

9. Features
 This castings can be made in almost any length, thickness,
diameter.
 Different wall thickness can be produced from the same size mold.
 Resistant to atmospheric corrosion a typical situation with pipes.
 Mechanical properties of centrifugal castings are excellent because
of the grain structure formed due to centrifugal action.
 Size limits are up to 6m(20ft) Diameter and 15m (49ft) length.
 Wall thickness range from 2.5 to 125mm
 Surface finish ranges from 2.5 to 12.5mm

10. Diagram

11. Applications
 Typical parts made by this process are Pipes, Fly wheels,
cylinder linears and other parts that are axi- symmetric.
 Its notably used to cast cylinder liners and sleeve valves
for piston engines, parts which could not be reliably
Manufactured.

12. Shell moulding
Shell moulding, also known as shell-mould casting
 It is an expendable mould casting process that uses
a resin covered sand to form the mould. As compared to sand
casting, this process has better dimensional accuracy, a higher
productivity rate, and lower labor requirements. It is used for small
to medium parts that require high precision.
 Shell mould casting is a metal casting process similar to sand
casting, in that molten metal is poured into an expendable mould.
 However, in shell mould casting, the mould 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.

13.  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.

14.  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.

15.  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.
Examples of shell molded items,
Include gear housings, cylinder heads and connecting rods. it is also used
to make high-precision molding cores.

16. Shell moulding

17.  ADVANTAGES:
(I) Shell molding can be completely automated for mass production.
(ii) The high productivity, low labor costs, good surface finishes, and precision
of the process can more than pay for itself if it reduces machining costs.
(iii) Complex shapes and fine details can be formed with very good surface
finish, high production rate, low labor cost (if automated).
(iv) Low tooling cost, little scrap generated.
(v) Very large parts and complex shapes can be produced.
(vi) Many material options.
(vii) Low tooling and equipment cost.
(viii) Scrap can be recycled.
(ix) Short lead time possible.

18. DISADVANTAGES:
 The gating system must be part of the pattern because the entire
mold is formed from the pattern, which can be expensive.
 The resin for the sand is expensive, although not much is required
because only a shell is being formed.
 high equipment cost.
 poor material strength.
 high porosity possible.
 secondary machining often required.
 high labor cost if done manually.
 the advantages ok but there also so many mistakes they are
creating.

19. Application:
 Cylinder heads,
 connecting rods,
 Engine blocks and manifolds,
 machine bases

20. Continuous castings
 Continuous casting is the process whereby molten metals solidifies
into continuous forms of strips and billets that can be further
worked upon in the finishing mills.
 These "semi finished" billet, bloom, or slab are casted by using
open ended mold and water spray technique.
 The continuous casting process was developed only in 1950,
before that steel was poured into a stationary mold to form 'ingots'.

21. Continuous Casting Process:
 In continuous casting, molten metal is poured into an open-ended
mold that can be made of graphite or copper.
 Graphite molds are widely used both in vertical and horizontal
continuous casting.
 Most molds are made from iso statically pressed graphite.
However, extruded graphite molds can also be used for vertical
casting of large ingots.
 The metal is first melted in a furnace and poured into a ladle. From
the ladle the hot metal is transferred into the tundish.
 The hot metal is poured into the continuous casting machine from
the tundish.
 The mold is water cooled. When the hot metal is poured into the
furnace, the metal near the walls cool first forming a skin like thin
strip. While the meal to the inside is still molten.

22.  The thin shell like solidified metal withdraws from the mold and
pass through a straightening roller. In the chamber the strand is
water sprayed which prevents porosity.
 The thin strip, now called a strand, rolls on a rotating roller. After
solidification, predetermined lengths of strands are cut into pieces
using mechanical shears or travelling oxyacetylene torches. The
cast size are are called strips, billets, slabs etc.
 Continuous casting can be better controlled by making the process
automated.
 The two common types of continuous casting are horizontal and
vertical continuous casting.
 Long shapes of simple cross section like round, square and
hexagonal rods can be done in a short, bottomless, water cooled
metal mold.

23. Advantages of Continuous Casting:
 Cost effective, time saving, casting process
 A highly productive process that can be fully automated
 High quality castings can be done

24. Application
 A great tonnage of continuous casting is done using cast steel.
 Other metals that are continuous casting are copper, aluminum,
grey cast irons, white cast irons, aluminum bronzes, oxygen-free
copper, etc.
 Metals are cast as ingot for rolling, extrusion, or forging, and long
shapes of simple cross section are cast as round, square, hexagonal
rods, etc.

25. Co2 moulding

26. CO2 Moulding
 A sand molding technique and uses sand grain in
which is mixed a solution of sodium silicate that acts
to bind the sand particles.
 CO2 gas is used to harden the sand after the mould
has been prepared.
 H2O+Na2SiO3+ CO2 →Na2CO3+SiO2

27. The Mold for Co2 Casting is made of a mixture of sand and
liquid silicate binder which is hardened by passing Co2 gas over the
mold. The equipment of the molding process include Co2 cylinder,
regulator, hoses and hand held applicator gun or nozzle. Carbon di
oxide molding deliver great accuracy in production.
Any existing pattern can be used for the molding purpose which
can be placed in the mold before the mold is hardened. This method
helps in producing strong mold and cores that can be used for high end
applications. If the process is carefully executed then casting can be as
precise as produced by the shell casting method.

28. Carbon di oxide casting is favored both by the commercial
foundry men and hobbyist for a number of reasons. In commercial
operations, foundry men can assure customers of affordable castings
which require less machining.
The molding process which can be fully automated is generally
used for casting process that require speed, high production runs and
flexibility. In home foundries this is one of the simplest process that
improves the casting quality.

29. Advantages:
 Compared to other casting methods cores and molds are strong
 Reduces fuel cost since gas is used instead of to other costly
heating generating elements
 Reduces large requirement for number of mold boxes and core
dryers
 Provides great dimensional tolerance and accuracy in production
 Moisture is completely eliminated from the molding sand
 This process can be fully automated.

30. Application
 Co2 casting process is ideal where speed and flexibility is the
prime requirement.
 molds and cores of a varied sizes and shapes can be molded by
this process.

31. INVESTMENT CASTING
• Investment casting is also called lost-wax process or
precision Investment Casting
• metals that are hard to machine or fabricate are
good candidates for this process.
• The mold is made by making a pattern using wax or
some other material that can be melted away.
• Term investment derives from the fact that the
pattern is invested with the refractory material

32. INVESTMENT CASTING
• This wax pattern is dipped in refractory slurry, which coats
the wax pattern and forms a skin.
• Slurry – Fine silica sand + water/ethyl silicate or Gypsum
solution
• This is dried and the process of dipping in the slurry and
drying is repeated until a robust thickness is achieved.
• After this, the entire pattern is placed in an oven and the
wax is melted away.
• This leads to a mold that can be filled with the molten metal.
• Because the mold is formed around a one-piece pattern,
(which does not have to be pulled out from the mold as in a
traditional sand casting process), very intricate parts and
undercuts can be made

33. Step by step procedure
• Make a master pattern of the part to be cast
(metal easily machined such as brass,
Aluminum alloy, alloy of tin lead bismuth)
• Making a master dies

34. Schematic illustration of investment casting
1. WAX INJECTION : Wax replicas of the
desired castings are produced by injection
molding. These replicas are called
patterns.
2. ASSEMBLY : The patterns are attached to a
central wax stick, called a sprue, to form a
casting cluster or assembly.
3. SHELL BUILDING : The shell is built by immersing the
assembly in a liquid ceramic slurry and then into a bed
of extremely fine sand. Up to eight layers may be
applied in this manner.
4. DEWAX : Once the ceramic is dry, the wax is melted out,
creating a negative impression of the assembly within
the shell.

35. • 5. CONVENTIONAL CASTING
In the conventional process, the shell is filled with
molten metal by gravity pouring. As the metal cools,
the parts and gates, sprue and pouring cup become
one solid casting.
• 6. KNOCKOUT
When the metal has cooled and solidified, the
ceramic shell is broken off by vibration or water
blasting.
• 7. CUT OFF
The parts are cut away from the central sprue using a
high speed friction saw.
• 8. FINISHED CASTINGS
After minor finishing operations, the metal castings--
identical to the original wax patterns--are ready for
shipment to the customer.

36. Casting with expendable mould: Investment Casting

37. Advantages and Limitations
• Parts of greater complexity and intricacy can be cast
• Close dimensional control 0.075mm
• Superior surface finish
• Un machinable Alloys can be cast
• The lost wax can be reused
• Additional machining is not required in normal course
• Preferred for casting weight less than 5 kg,( weighing 1g –
35Kg)
• Maximum dimension less than 300 mm, Thickness is
usually restricted to 15mm
• High-melting point alloys
• Al, Cu, Ni, Carbon and alloy steels, tool steels etc. are the
common materials
• Not a cheap process