moulding

1. Advanced Casting Process

2. Casting
• Casting is a manufacturing process, which is used
directly or indirectly in almost every industry.
• In this era there is a demand to innovate processes,
which can reduce lead-time, reduce cost of
production without compromising with the quality
of the products and reduce ill effects on
environment.

3. casting
• The type of process employed for casting has an effect over
properties like surface finish, microstructure, hardness,
toughness, etc. of the resultant product.
• In modern days industries there are many factors, which
affects the decision of selecting the type of casting process
to be:
Cast Product
Cost incurred in manufacturing
Lead time
Environmental effect

4. Magnetic mould casting
• Magnetic mould casting is an innovative process
having a great potential to replace conventional
casting methods due to various advantages
associated with it.
• The setup of MMC includes winding of copper wire
such that it behaves like a solenoid with hollow
cavity in which actual casting process is to be
carried out.

5. Magnetic mould casting
• Magnetic mould casting (MMC) is an application of
electromagnetism to the process of casting.
• Steel shots constitute the mould that is formed by
application of magnetic field on them.
• The application of magnetic field that induces
magnetic bonds between steel shots which
gives strength to mould.

6. MMC Set up

7. Magnetic mould casting
• Hollow cylinder of Diameter = 200mm and Height
=250mm is made by winding copper wire over
hollow core of steel. Steel is used as core so as to
confine the magnetic field inside the solenoid since
steel has high magnetic permeability.
• Copper wire of 19 wire gauge is used to sustain the
current for required time period of experiment
without damage due to heating.

8. Magnetic mould casting
• Iron container- It is made up of pure iron sheet of 1mm
thickness rolled into the shape of cylinder of 180mm outer
diameter and 250mm height and closed at one end.
• Power supply- Constant DC power supply is provided with the
help of single-phase 0-250V autotransformer and a bridge
rectifier of 230V and 10 A rating is used.
• For supply to the copper coil, a power rectifier in series to
auto transformer is connected. Ac supply is given to
autotransformer through which voltage is varied. Output of
autotransformer is connected to power rectifier, which
converts ac to dc, and this dc output supply is given to
copper coils.

9. Magnetic mould casting
• The numbers of turns were decided by checking
the magnetic field value at different values of
turn and winding was stopped when required
field value was obtained.
• Hall effect sensor is used for the detection of
magnetic field produced inside the mould box.
The mould box is designed to produce magnetic
field from 0-0.5 Tesla.

10. MMC Set up

11. Magnetic mould casting
• Steel shots constitute the mould that is formed by
application of magnetic field on them.
• The application of magnetic field that induces
magnetic bonds between steel shots which
gives strength to mould.
• This reduces the time elapsed in ramming process.

12. Magnetic mould casting
• breaking of mould becomes easier by using magnetic
field, as it is required to switch off the supply to turn
down the magnetic field and mould breaks.
• MMC process employs a one-piece mould and an EPS
(expandable polystyrene) pattern, which gives an
advantage of cast products being free of defects
associated with joint line.
• the products have better dimensional tolerances than
the products obtained from conventional methods.

13. Magnetic mould casting
• The amount of machining required is less thus
reducing the time and cost involved in finishing a
product for use.
• The mechanical properties like tensile strength,
impact strength and hardness of the products cast
from MMC have higher values as compared to sand
casting products.
• The reason behind this improved might be the
higher solidification rate of steel mould as its thermal
conductivity is more than the sand mould.

14. Magnetic mould casting
• In casting, foundry waste is released, which is
directly related to type of molding technique, type
of furnace and type of metal used.
• MMC steel shots can be reused and magnetic field
had not any effect on the worker’s health.
• MMC is an eco-friendly process as waste
generation is minimum and due to reusability of
mould material.

15. Process parameter
• gauge of copper wire
• intensity of field required
• size of steel shots
• composition of steel shots
• size of expendable polystyrene pattern
• refractory coating on its surface

16. Magnetic mould casting
• This process is still in its research phase. There
is no evidence of its use in any industry till
now but it can be used as a replacement of
conventional methods of casting as this
process has certain advantages over them.

17. Centrifugal Casting
• The essential feature of centrifugal casting is the
introduction of molten metal into a mould which is
rotated during solidification of the casting. The
centrifugal force is relied upon for shaping and
feeding the molten metal with the utmost of detail
as the liquid metal is thrown by the force of gravity
into the designed crevices and detail of the mould.

18. Centrifugal Casting
• The concept of centrifugal casting is by no means a
modern process. This technique which lends clarity
to detail was used by Benvenuto Cellini and others
in the founding arts during the 16thcentury.
• The mention of actual centrifugal casting machines
is first recorded when a British inventor,
A.G.Eckhardt, was issued a patent in the year 1807.

19. Centrifugal Casting
• Centrifugal casting process is most widely used for
production of pipes, cylinder liners, brake drums, flywheels
and other axis-symmetric parts, in which molten metal is
poured at suitable temperature into rapidly rotating mold.
• The process of centrifugal casting differs from static casting
in that the mold itself is spinning during the time, casting is
solidifying.
• The defects in centrifugal castings are mainly related to the
solidification process.

20. Schematic of centrifugal casting
process

21. Centrifugal Casting
• It is essential that pouring temperature of molten
metal should be high enough to enable it to reach
the farthest point in the mould before
solidification commence.
• The axis of rotation of mould may be horizontal,
vertical or slightly inclined.
• The centrifugal force imparted to molten
metal enables it to be picked up and held in
contact with the rotating mould.

22. Centrifugal Casting
• The mould is allowed to rotate till the casting is completely
solidified.
• Thus the outer shape of casting takes the shape of the
inside of the mould and the bore of casting is truly circular
and concentric with axis of rotation.
• The thickness of casting is determined by the quantity of
molten metal poured, and by the length of mold between
two end plates.
• In case of centrifugal casting, there is no need of runners
and risers .

23. Centrifugal Casting
• The metal in the bore serves as riser.
• Therefore, the yield from centrifugal casting is
much higher than normally obtained in gravity
poured castings because there are neither separate
gates nor risers.
• The castings thus produced also have a high
density than that of gravity poured castings, and
have the superior mechanical properties.

24. Methods of Centrifugal Casting
• True Centrifugal Casting
• No core is used in this method; essentially all
of the heat is extracted from the molten
metal through the outer mold wall.

25. True Centrifugal Casting
• The poor thermal conductivity of the air in contact
with the internal diameter results in little heat loss
from this direction.
• Thus, perfect directional solidification is obtained
from outer surface to inner one and grain growth
is typically columnar.

26. Semi-Centrifugal Casting
• This is very similar to true centrifugal casting, except core is used
in this method, due to the irregular contour of the internal bore.

27. Semi-Centrifugal Casting
• Solidification occurs in both inward and outward
directions, with the consequent problem of
centerline soundness.
• By the application of centrifugal force feeding is
enhanced, and is equivalent to the use of
very high risers.
• This method is adaptable to a wide variety of cast
parts such as jaw clutches, sheaves, gear blanks,
casing heads, and flanges. It is also used for the
production of castings, which have very thin metal
sections.

28. Centrifuge or Pressure Casting
• In this method (usually done vertically but sometimes
horizontally), there is a central sprue at the axis of
rotation of the mold.
• Mold cavities are clustered about the central
sprue in a symmetrical array, each connected to sprue
by one or more radial gates.

29. Applications of Centrifugal Casting
• Centrifugal castings are used over a broad field of
application and the process allows the manufacture of
components in many alloy types, both ferrous and non-
ferrous.
• Rings, flanges and compressor casings are cast in
martensitic and austenitic heat resisting steels and
nickel-rich alloys for the aircraft industry.
• Steam-turbine bearing-shells in leaded nickel bronze.
• Reducing roller for steel-rolling mills in alloy iron,
spheroidal-graphite iron and carbon-steel.

30. Applications of Centrifugal Casting
• Corrosion-resisting rolls for the textile and cellophane
industries in stainless steel.
• Cylinder liners, gear blanks and piston-ring blanks in
all grade of grey iron for the motor-car industry.
• Rollers, ball or plain bearings in phosphor-bronze and
other copper-rich alloys for the engineering industries.
• Switch-gear components in high-conductivity copper
for the electrical engineering
industries.

31. Advantages
• Effect of solidification shrinkage is progressively
transferred to the inner bore.
• Lower pouring temperatures are possible than
those used for static castings.
• High casting yield, since conventional running and
gating systems are eliminated, can reach 96
percent and over in some application.

32. Advantages
• Compared with static castings, thermal gradient is much steeper
due to unidirectional heat flow, this result in the characteristic
columnar grains, compared with the equiaxed structure of sand
casting.
• The steep thermal gradient, especially with metal moulds gives
rapid solidification and therefore fine grain-size
• Clean metal: When spun, the impurities such as dirt, sand slag,
and gas pockets, since they are lighter, will collects on the inner
surface of the central hole, where it can easily be removed by
machining.
• Dense metal: Since the molten metal solidifies under pressure, a
dense metal
structure is produced
• Elimination of central cores.
• Adopted for mass production.

33. Metal Injection Molding (MIM)
• Metal injection molding (MIM) is
a metalworking process in which finely-powdered
metal is mixed with binder material to create a
"feedstock" that is then shaped and solidified
using injection molding. The molding process
allows high volume, complex parts to be shaped in
a single step. After molding, the part undergoes
conditioning operations to remove the binder
(debinding) and densify the powders.

34. • MIM is a subcategory of the Powder Injection
Molding (PIM) manufacturing technique.
• The fundamental idea behind the MIM
manufacturing method is to combine the shaping
benefits of injection molding with the resilient
mechanical properties of metals.
• This “best of both world” approach allows the
production of complex and detailed metal parts
with high strength and stiffness.

35. • Traditional casting methods requires the metal to
be in a molten state during the casting, the metal
powder and polymer feedstock used in MIM
enables the molding process to be performed at
much lower temperatures.
• feedstock is loaded into the injection molding
machine and the machine drives the screw filling
the mold.

36. The MIM Process
• At the mixing stage, both metal powder and the
polymeric binder (thermoplastic types) are
combined into a homogeneous mixture

37. • The first stage following the injection molding is
debinding. The debinding stage is designed to get rid of
the polymer binder material from the molded part,
making it purely metal.

38. After the binder material has been removed follows the final stage,
sintering. At the sintering stage the now pure metal powder part is
heated up to near melting temperatures. The high temperature makes
the particles of the metal powder fuse together, increasing the density
and strength of the part.

39. Injection molding machine
• The machine is made up of two main units, an
injection unit and a clamping unit.
• The two units are focused on performing two
different tasks which when combined will
produce the parts.

40. Injection molding machine
• Injection unit
The main task of the injection unit is to heat up
the feedstock and then force it into the mold.
The injection unit controls features from
feedstock viscosity to shot size. The unit consists
of a few central components:

41. Injection molding machine
• Hopper: Is the container that sits above the machine and
feeds granulates to the process
Reciprocating screw: is the heart of the injection unit. It not
only provides the push that forces the molten raw material
into the mold its´s also the prime producer of heat.
Barrel: is the casing around the screw, the barrel is covered
in adjustable heating bands that keep the barrel at constant
temperature.
Screw motor: Provides the rotation for the screw.
Injection cylinder: Moves the screw forwards and backwards
inside the barrel. Also provides the thrust for the injection.
Nozzle: Connects the barrel to the mold. Provides the final
heating to the shot before it enters the cavity.

42. Injection molding machine
• Clamping unit
The main task of the clamping unit is to control the
mold throughout the cycle. With the help of a
hydraulic motor the clamping unit can open and
close the mold. The most demanding aspect of the
clamping unit is keeping the mold halves tightly
together during injection and packing. The clamping
unit also controls the part release trough moving
the ejector rod and pins.

43. Injection molding machine

44. Injection molding machine
Molding cycle The molding cycle can be divided into
different phases:
1. Feedstock granulates
2. A rotating screw
3. A hydraulic ram
4. The remaining < 10% of material is injected with high
pressure.
5. Mold opens, ejector pins push the solidified part out
from the mold cavity.
6. Mold closes and cycle repeats.

45. Feedstock
• Feedstock refers to the raw material used in metal
injection molding. The whole MIM process is
essentially based upon the properties and
constituency of the feedstock
• The feedstock consists of two main components: a
binder and a metal powder.
• The influence that the feedstock will have on the
molding process can be traced back to five main
factors:
• Metal powder characteristics
• Binder composition
• Powder/binder ratio
• Mixing method
• Pelletizing technique

46. • Most commonly used alloys consist of stainless
steel, tool steel, copper, cemented carbides,
titanium and other refractory metals.
• In theory, the particle size of a powder can be as
big as 45μm but the ideal particle size for most
alloys is below 22μm in diameter.
• The role of the binder is purely to provide the
feedstock mix with moldability and shape retaining
properties during manufacturing.

47. Debinding
• Debinding is the process of removing the binder-
material from the molded part.
• During debinding the molded part must endure the
stresses produced by the binder being extracted
from within the part, while still maintaining its
shape.
• The debinding process requires two steps: primary
debinding and secondary debinding.
• The function of the primary debinding is to get rid
of the filler phase and surfactants. The secondary
debinding step is where the backbone binder is
removed and the sintering process sets in.

48. • Sintering
Sintering is the process that gives MIM parts their
strength. The sintering process will transform the
rigid powder compacts into proper solid metal
objects. After sintering the produced parts will
exhibit strength, hardness, ductility, wear resistance,
conductivity and even visual resemblance similar to
parts produced by conventional metalworking
methods.

50. HIGH PRESSURE MOULDING
TECHNOLOGY
• Alcatel developed, qualified and introduced in
1993 for their cable products a moulding machine
based on a high pressure technique.