1. ME8351
MANUFACTURING TECHNOLOGY – I
OBJECTIVE:
To introduce the concepts of basic manufacturing processes and
fabrication techniques, such as metal casting, metal joining, metal forming
and manufacture of plastic components.
CO1 Explain different metal casting processes, associated defects, merits and
demerits
CO2 Compare different metal joining processes.
CO3 Summarize various hot working and cold working methods of metals.
CO4 Explain various sheet metal making processes.
CO5 Distinguish various methods of manufacturing plastic components.
2. METAL CASTING PROCESSES
Sand Casting : Sand Mould – Type of patterns - Pattern Materials –
Pattern allowances –Moulding sand Properties and testing – Cores –
Types and applications – Moulding machines– Types and applications;
Melting furnaces : Blast and Cupola Furnaces; Principle of
special casting processes : Shell - investment – Ceramic mould –
Pressure die casting - Centrifugal Casting - CO2 process – Stir casting;
Defects in Sand casting
3. SAND CASTING
Casting is one of the processes used for making
components of complicated shapes in large quantity. It is
process of producing metal parts by pouring molten metal into
the mould cavity of the required shape and allowing the metal
to solidify.
SAND MOULDS
Mould is the cavity of the required shape made in
moulding sand or in other material
PATTERN
It is model of the required casting made in wood,
metal, plastics.
4.
5. The following factors are very useful for
the selection of patterns
• Size and complexity of the shape
• Number of components to be produced
• Method of castings to be used
8. PATTERN MATERIALS
The following factors are to be considered for the selection of
pattern materials
• Design of casting
• Number of castings to be produced
• Degree of accuracy and surface finish required
• Shape, complexity and size of the castings
• Casting or moulding method adopted
9. PATTERN MATERIALS
1.0 WOOD
• Teak wood, white pine, rose wood are used.
• Metal spray coating upto 0.25mm thick, coating materials Zinc and
Aluminium to avoid moisture absorption and good surface finish
11. PATTERN MATERIALS
3.0 PLASTER
• Plaster of paris or gypsum cement is used
• Plaster can be easily made into difficult shapes and easily
worked.
4.0 PLASTICS
• Plastics pattern is cast from a wooden pattern called master
pattern.
• Light weight but strong and not affected by moisture and
more resistant to wear.
•Poly acrylates, Poly ethylene, Poly Vinyle chloride etc.
•
5.0 WAX
It is used in investment castings. Paraffin wax, shellac wax
• It has good surface finish and high dimensional accuracy
• It is used for making small pattern only
12. PATTERN ALLOWANCES:
Patterns are not made into exact size of the castings to be
produced.
Patterns are made slightly larger than the required casting. This
extra size given on the pattern is called pattern allowances.
Types of pattern allowances:
1. Shrinkage allowance
2. Machining or finish allowance
3. Draft or Taper allowance
4.Distortion or chamber allowance
5. Rapping or shake allowance
13. PATTERN ALLOWANCES
1.0 Shrinkage allowance
• The extra size provided on the pattern for metal shrinkage is called
shrinkage allowance.
2.0 Machining or Finish allowance
• The pattern is made larger than the required casting for finishing purpose.
•This extra size given to the pattern for machining purpose is called
machining or finish allowance.
16. TYPES OF MOULDING SAND
1.0 Green sand
• Moist state is known as green sand.
• 5 to 8% of water and 16 to 30 % of clay.
• soft, light and porous.
2.0 Dry Sand
• Prepared in dry stage.
• Used for large casting
• Mould does not cause defects which causes due to moisture.
3.0 Facing Sand
• Used directly cover the surface of the pattern and comes contact with molten metal.
• It contains Silica, Clay, Talc, Graphite etc..
4.0 Loam Sand
• It consists of fine silica sand, fine refractories, clay, graphite, fibre and water
• It used for bell, roller, pulley etc.
5.0 Backing sand
• It used for backup the facing sand and to fill the whole volume of the mould box.
6.0 Parting sand
• It used when a casting is made up of two halves with cope and drag. It is sprinkled over the pattern
to avoid sticking of green sand.
17. PROPERTIES OF MOULDING SAND
1.0 Porosity or permeability
• It is a measure of moulding sand by which the sand allows the steam and gases to pass through it,
otherwise casting defects such as blowholes will occur.
• It depends on Quality and quantity of clays, Moisture, Degree of compactness.
2.0 Plasticity or flowability
• It should flows around and over the pattern, uniformly fills the flask.
3.0 Adhesiveness
• It sticks or adheres to moulding boxes. It does not fall out when the flasks are lifted and turned
over.
4.0 Strength or cohesiveness
• It should have sufficient strength so that the mould does not collapse during lifting, shifting, turning,
pouring the molten metal.
5.0 Refractoriness
• It should resist high temperature of molten metal and depends on purity of the sand, sizes.
6.0 Collapsibility
• It should collapse easily after the casting solidifies.
18. TESTING OF MOULDING SAND
• Moisture content test
• Clay content test
• Grain fineness test
• Permeability test
• Strength test
• Deformation and toughness test
• Hot strength test
• Refractoriness test
• Mould hardness test
19. TESTING OF MOULDING SAND
1.0 Moisture content test
a) Loss of weight after evaporation
Moisture content = W1 – W2
% of moisture content = (W1 – W2) x 100
W1
b) Moisture teller method c) Based on chemical reaction
CaC2 + 2H2O C2H2 + Ca (OH)2
Depending upon the amount of acetylene gas,
moisture content is determined.
20. TESTING OF MOULDING SAND
2.0 Clay content test
Sand + distilled water + 1% NaOH stirred 5 min and settle down 10 min sand + clean water.
Clay content = W1 – W2, W1 – weight of sand before drying, W2 – after drying.
% of clay content = (W1 – W2) x 100
W1
3.0 Grain fineness test
21. TESTING OF MOULDING SAND
4.0 Permeability test
Tendency of sand which allows the escape of gases or air through it.
Permeability number = VH / APT
V = Volume of air (2000cc)
H = Height of the specimen = 50.8mm
A = Area of specimen = πd2/4 =20.268cm2
T = Time taken by 2000cc
P = Pressure measured in manometer.
22.
23. TESTING OF MOULDING SAND
5.0 Strength test
Measure of holding power or bonding power.
a) Compressive strength
b) Shear strength
c) Tensile strength
d) Bending strength
24.
25. TESTING OF MOULDING SAND
6.0 Deformation and Toughness test
Deformation – Plasticity of sand can be tested by applying compressive force.
Toughness –The deformation of green compressive strength provides the quality of
sand mix.
7.0 Hot strength test
8.0 Refractoriness test
26. TESTING OF MOULDING SAND
9.0 Hardness test
Indicates the ramming density of the actual sand mould.
27. CORES
• A core is a body made of sand which is used to make a cavity or a hole in
the casting.
Essential qualities of a core
• Permeability
• Refractoriness
• Strength
• Collapsibility
• Stability
28. Core making materials
A core is made of core sand, binder and additives
• Core sand consists of refractories such as silica sand, zircon,
olivine etc
• Binders contains of vegetable oil or mineral oil, core flour,
resins water, fire clay, urea.
• Additives are wood flour, coal powder, graphite, cow dung.
29. Core Boxes
• Core boxes are used to produce cores. It is made
of wood or metal
30.
31. Core Ovens
Core ovens are used for heating the cored to obtain required
hardness.
• Batch type oven
• Continuous type oven
• Dielectric baking oven
32.
33. Types of core
According to the state of core
• Green sand core
• Dry sand core
According to the position of the core in the mould
• Horizontal core
• Vertical core
• Balanced core
• Hanging core
• Drop core
34.
35.
36.
37. Various methods of testing core sand
The various core sand tests are
• Green strength test
• Permeability test
• Baked strength test
• Hot strength test
• Retained strength test
• Core hardness test
• Moisture content test
38. MOULDING MACHINES
Moulding machines is used for mass production. Since the hand
moulding is a slow process, only making few casting. For more
castings, Moulding is done by using moulding machines.
TYPES OF MOULDING MACHINES
a) Jolting Machine
Raised about 80mm and suddenly dropped.
39. TYPES OF MOULDING MACHINES
b) Squeezing Machine
The mould sand in the flask is squeezed between the machine table and squeezer head.
40. c) Sand Slinger
Impeller rotates, it will throw a stream of sand at great velocity
into the flask.
59. 7.0 CO2 PROCESS
• Pure dry silica sand mixed with sodium silicate liquid use as a
binder for making core.
• NaSiO3 + CO2----------- NaCO3 + SiO2
• Moisture should not exceed 3%.
• CO2 gas is passed through the core for 30 sec at a pressure of 140
KN/m2.
• CO2 react with sodium silicate and forms sodium carbonate and silica
gell.
• Silica gell binds the sand grains together to provide strength and
hardness to the core.
