ME 1207 Production Processes
Contact Hours/Week: 3.00
Credits: 3.00
Presented by:
Shah Mohammed Takrim
Lecturer
Department of Mechanical Engineering,
RUET
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Reference Book
By: P N Rao
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Manufacturing Processes
Manufacturing involved in turning raw materials to finished
products is to be used for same purpose.
The proper design .
The manufacturing feasibility of their designs.
Secondly, find out that there is more than one process
available for manufacturing a particular product.
Proper choice of the process
Lowest manufacturing cost
The product of desired quality.
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These processes can be broadly classified into four
is a manufacturing process in which molten metal is poured into a mold cavity
categories: Casting
having the shape of the desired part. The metal is allowed to cool and solidify, and
then the solidified part is removed from the mold.
Forming is a manufacturing method in which a material (usually metal) is
deformed plastically into the desired shape without adding or removing
material. It relies on the application of mechanical forces or heat to change
the shape.
Casting Processes
Forming Processes
The fabrication process refers to the assembly of standardized parts or
construction of structures by cutting, joining, or shaping metal
Fabrication Processes the
components.
Material Removal Processes
The metal removal process, also known as machining, involves removing unwanted material from a
workpiece to obtain the desired shape, size, and surface finish.
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Casting is a manufacturing process in which molten metal is poured into a mold cavity having the shape of the desired part. The metal is allowed to cool and
solidify, and then the solidified part is removed from the mold.
Casting Processes
 Only liquid metal is used.
 Preparation of a cavity usually in a refractory material to resemble
closely the final object to be made.
 Molten metal is poured into this refractory mould cavity and is
allowed to solidify.
 The object after solidification is removed from the mould.
 The principal process among these is sand casting where sand is used
as the refractory material.
The process is equally suitable for the production of a very small batch
as well as on a very large scale.
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Some of the other casting processes for specialized
needs are as follows:
Shell Mould Casting
Precision Investment Casting
Plaster Mould Casting
Permanent Mould Casting
Die Casting
Centrifugal Casting
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Forming Processes
These are solid state manufacturing processes
Involving minimum amount of material wastage and faster
production.
Metal may be heated to a temperature which is slightly below
the solidus temperature
And then a large force is applied such that the material flows
and takes the desired shape.
The desired shape is controlled by means of a set of tools
called dies
Which may be completely or partially closed during
manufacturing.
These processes are normally used for large-scale production
rates.
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Some of the metal forming processes are as
follows
 Rolling
 Drop Forging
 Press Forging
 Upset Forging
 Extrusion
 Wire Drawing
 Sheet Metal Operations
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Fabrication Processes
 These are secondary manufacturing processes
 The starting raw materials are processed by any of the previous manufacturing processes described.
 It essentially involves joining pieces either permanently or temporarily to perform the necessary function.
 The joining can be achieved by either or both of heat and pressure and/or a joining material.
 Many of the steel structural constructions we see are first rolled and then joined together by a fabrication
process.
Some of the processes of interest in this category are as
follows:
● Gas Welding
● Electric Arc Welding
● Electric Resistance Welding
● Thermit Welding
● cold Welding
● Brazing
● Soldering
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Material Removal Processes
 secondary manufacturing processes
 the additional unwanted material is removed in form of chips from the blank
material
 by a harder tool to obtain the final desired shape.
 Material removal is normally the most expensive manufacturing process because
more energy is consumed and also a lot of waste material is generated in the
process.
 Still this is widely used because it delivers very good dimensional accuracy and
good surface finish. It also generates accurate contours.
 Material removal processes are also called machining processes.
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Various processes in this category are as follows:
Turning
Drilling
Shaping and Planning
Milling
Grinding
Broaching
Sawing
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Chapter 03
Metal Casting Processes
What is casting?
 Casting is one of the earliest metal shaping methods known to
human being.
 It generally means pouring Molten metal into a refractory mould
with a cavity of the shape to be made and allowing it to solidify.
 When solidified, the desired metal object is taken out from the
refractory mould either by breaking the mould or taking the
mould apart.
 The solidified object is called casting. This process is also called
founding
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Advantages
Molten material flows into any small section in the mould cavity
Any intricate shapes, internal or external, can be made
Possible to cast practically any material, be it ferrous or non–ferrous.
Necessary tools required are very simple and inexpensive.
As a result, for trial production or production of a small lot, it is an ideal method.
It is possible in casting process to place the amount of material where exactly
required.
As a result, weight reduction in design can be achieved.
Castings are generally cooled uniformly from all sides and therefore they are
expected to have no directional properties.
There are certain metals and alloys which can only be processed by the casting
and not by any other process like forging because of the metallurgical
considerations.
Casting of any size and weight, even up to 200 tons, can be made.
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Limitations
However, the dimensional accuracy and surface finish achieved by
normal sand casting process would not be adequate for final
application in many cases.
To take these cases into consideration, some special casting
processes such as die casting have been developed.
Also the sand casting process is labour intensive to some extent and
therefore many improvements are aimed at it like machine moulding
and foundry mechanisation.
With some materials it is often difficult to remove defects arising out
of the moisture present in sand castings.
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Applications
Typical applications of sand casting process
are
Cylinder blocks,
Mill rolls,
Wheels,
Liners,
Housings,
Machine tool beds,
Water supply pipes and specials,
Pistons,
and bells
Piston rings,
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Casting Terms
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Casting Terms
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Casting Terms
Reference may please be made to Fig. 3.1.
Flask
A moulding flask is one which holds the sand
mould intact.
Depending upon the position of the flask in the
mould structure, it is referred to by various names
such as drag, cope and cheek.
It is made up of wood for temporary applications
or more generally of metal for long term use.
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Casting Terms
Drag Lower moulding flask.
Cope Upper moulding flask.
Cheek Intermediate moulding flask used in three piece moulding.
Pattern Pattern is a replica of the final object to be made with some
modifications. The mould cavity is made with the help of the pattern.
Parting line This is the dividing line between the two moulding flasks that makes
up the sand mould.In split pattern it is also the dividing line between the two
halves of the pat tern.
Bottom board This is a board which is normally made of wood and is used at the
start of the mould making. The pattern is first kept on the bottom board, sand is
sprinkled on it and then the ramming is done in the drag.
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Casting Terms
Facing sand The small amount of carbonaceous material sprinkled on the inner
surface of the moulding cavity to give better surface finish to the castings.
Moulding sand It is the freshly prepared refractory material used for making the
mould cavity. It is a mixture of silica, clay and moisture in appropriate proportions
to get the desired results and it surrounds the pattern while making the mould.
Backing sand It is what constitutes most of the refractory material found in the
mould. This is made up of used and burnt sand.
Core It is used for making hollow cavities in castings.
Pouring basin A small funnel shaped cavity at the top of the mould into which the
molten metal is poured.
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Casting Terms
 Sprue The passage through which the molten metal from the pouring basin reaches the mould cavity. In
many cases it controls the flow of metal into the mould.
 Runner The passageways in the parting plane through which molten metal flow is regulated before they
reach the mould cavity.
 Gate The actual entry point through which molten metal enters mould cavity.
 Chaplet Chaplets are used to support cores inside the mould cavity to take care of its own weight and
overcome the metallostatic forces.
 Chill Chills are metallic objects which are placed in the mould to increase the cooling rate of castings to
provide uniform or desired cooling rate.
 Riser It is a reservoir of molten metal provided in the casting so that hot metal can flow back into the
mould cavity when there is a reduction in volume of metal due to solidification.
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Sand Mould Making Procedure
a) Drag completed
b) Ready for roll-over
c) After roll-over
d) Cope rammed
e) Mould ready for pouring
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Sand Mould Making Procedure
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Patterns
Pattern is a replica of the object to be made by the
casting process, with some modifications.
The main modifications are:
 The addition of pattern allowances,
 The provision of core prints, and
 Elimination of fine details which cannot be obtained by casting and hence are
to be obtained by further processing.
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Pattern Allowances
 The dimensions of the pattern are different from the final dimensions of the casting required. This is required
because of the various reasons.
These are detailed as follows.
Shrinkage
 All the metals shrink when cooling except perhaps bismuth. This is because of inter– atomic vibrations which
are amplified by an increase in temperature.
Types of Shrinkage:
 Liquid shrinkage refers to the reduction in volume when the metal changes from liquid to solid state at the
solidus tempera ture.
 Solid shrinkage is the reduction in volume caused when metal loses temperature in solid state. The shrinkage
allowance is provided to take care of this reduction.
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Finish or Machining Allowance
Draft
At the time of withdrawing the pattern from the
sand mould, the vertical faces of the pattern are in
continual contact with the sand which may damage
the mould cavity, as shown in Fig. 3.5(a).
To reduce its chances, the vertical faces of the
pattern are always tapered from the parting line
(Fig. 3.5(b)).
This provision is called draft allowance.
Draft allowance varies with the complexity of the
job.
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Finish or Machining Allowance
The draft allowance given varies for hand moulding
and machine moulding.
More draft need to be provided for hand moulding
compared to machine moulding.
In machine moulding, the actual draft given varies
with the condition of the machine (new, rigid,
properly aligned, etc., require less draft).
An observation here is that draft is always provided
as an extra metal over and above the original casting
dimensions as shown in the following example.
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Shake Allowance
 Before withdrawal from the sand mould, the pattern is rapped all around the vertical faces to
enlarge the mould cavity slightly which facilitates its removal.
 Since it enlarges the final casting made, it is desirable that the original pattern dimen sions should
be reduced to account for this increase.
 There is no sure way of quantifying this allowance since it is highly dependent on the foundry
personnel and practices involved.
 It is a negative allowance and is to be applied only to those dimensions which are parallel to the
parting plane.
 One way of reducing this allowance is to increase the draft which can be removed during the
subsequent machining.
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Distortion Allowance
 A metal when has just solidified is very weak and therefore is likely to be distortion prone.
 This is particularly so for weaker sections such as long flat portions, V, U sections or in a
complicated casting which may have thin and long sections connected to thick sections.
 The foundry practice should be to make extra material provision for reducing the distortion.
 Alternatively, the shape of pattern itself should be given a distortion of equal amount in the
opposite direction of the likely distortion direction.
 This can be done by trial and error basis to get the distortion amount. Some data about a few test
cases may be available from the literature.
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Core Prints
 For all those castings where coring is required, provision
should be made to support the core inside the mould
cavity.
 One of the methods that are universally followed is to
provide core prints where possible.
 Figure 3.7 shows an example of the provision of core
prints.
 The size of the core prints to be provided is estimated
based on the specific casting.
 Example: Flange
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Pattern Materials
The usual pattern materials are
 wood,
 metal and
 plastics.
1. Wood
The most commonly used pattern material is wood, because of
 its easy availability, low weight, can be easily shaped and is relatively cheap.
 But the main disadvantage of wood is its absorption of moisture as a result of which distortions and
dimensional changes occur.
 The usual varieties of wood commonly used for making patterns are pine, mahogany, teak, walnut and
deodar.
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Pattern Materials
2. Metal patterns
 Durability and smooth surface finish,
 large scale casting production and for closer dimensional tolerances.
Though many materials such as cast iron, brass, etc., can be used as pattern
materials, aluminium and white metal are most commonly used.
 Light,
 Can be easily worked,
 Corrosion resistant.
 Since white metal has very small shrinkage, it can be used for making additional
patterns without worrying about the double shrinkage allowances.
Most metal patterns are cast in sand moulds from a master wood pattern
provided with the double shrinkage allowance.
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Pattern Materials
Plastics
 Low weight,
 Easier formability,
 Smooth surfaces and durability.
 Do not absorb moisture and are therefore, dimensionally stable and can be cleaned easily.
The making of a plastic pattern can be done in sand clay moulds or moulds made of plaster of paris.
 Cold setting epoxy resins with suitable fillers.
 Polyurethane foam. It is very light and can be easily formed into any Shape required.
 This plastic has very low ash content and hence can be burned inside the mould.
The pattern material is to be chosen based on the expected life
of the patternes.
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Types of Patterns
1. Single Piece Pattern
Inexpensive and the simplest type of patterns are made of
a single piece as shown in Fig. 3.9.
This type of pattern is used only in cases where the job is
very simple and does not create any withdrawal problems.
It is also used for applications in very small–scale
production or in prototype development.
This pattern is expected to be entirely in the drag.
One of the surfaces is expected to be flat which is used as
the parting plane.
If no such flat surface exists, the moulding may become
complicated with the necessity of a follow board.
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Types of Patterns
2. Split Pattern or Two Piece Pattern
 This is the most widely used type of pattern for intricate castings.
 When the contour of the casting makes its withdrawal from the mould difficult.
 When the depth of the casting is too high,
Then the pattern is split into two parts so that one part is in the drag and the other in the cope.
 The split surface of the pattern is same as the parting plane of the mould.
 The two halves of the pattern should be aligned properly by making use of the dowel pins which are fitted to the cope
half.
 These dowel pins match with the precisely made holes in the drag half of the pattern and thus align the two halves
properly as seen in Fig. 3.10.
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Types of Patterns
3. Gated pattern
 This is an improvement over the simple pattern.
 The gating and runner system are integral with the pattern.
 Eliminate the hand cutting of the runners and gates.
 Improve the Productivity of a moulder.
4. Cope and drag pattern
 These are similar to split patterns.
 The cope halves, drag halves of the pattern and the gating and risering systems are attached separately to the metal or
wooden plates along with the alignment pins (fig. 3.11).
 The cope and drag moulds may be produced using these patterns separately by two moulders
 But they can be assembled to form a complete mould.
 These types of patterns are used for castings which are heavy and inconvenient for handling as also for continuous
production.
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Types of Patterns
5. Match Plate Pattern
 These are extensions of the previous type.
 Here the cope and drag patterns along with the gating
and the risering are mounted on a single matching
metal or wooden plate on either side as shown in Fig.
3.12.
 On one side of the match plate the cope flask is
prepared and on the other, the drag flask.
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Home Work! Home Work!! Home Work!!!
Loose Piece Pattern
It has detachable parts that are removed separately after
the main pattern.
Used for making moulds with complex shapes or undercuts.
board supports weak or uneven patterns during moulding.
Follow Board Pattern AIt helps
keep the pattern steady and properly aligned.
rotating arm shapes large, round moulds like cylinders or cones.
Sweep Pattern AUsed
instead of full patterns for big symmetrical castings.
Skeleton Pattern
A wooden frame outlines the shape and is filled with sand.
Used for large, simple castings to save material and cost.
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Pattern Colour Code
The patterns are normally painted with contrasting colours such that
the mould maker would be able to understand the functions clearly.
The colour code used is
1. Red or Orange on surfaces, not to be finished and left as cast
2. Yellow on surfaces to be machined
3. Black on core prints for unmachined openings
4. Yellow stripes on black on core prints for machined openings
5. Green on seats of and for loose pieces and loose core prints
6. Diagonal black stripes with clear varnish on to strengthen the weak
patterns or to shorten a casting
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Pattern Colour Code
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Moulding Materials
A large variety of moulding materials are used in foundries for manufacturing
moulds and cores. They are:
Moulding sand
System sand (backing sand)
sand is reclaimed moulding sand that is reconditioned
Rebonded sand (resin bonded sand) Rebonded
by adding fresh binder and water for reuse in foundry moulds.
Facing sand Parting sand is a fine, dry sand sprinkled on moulding surfaces to prevent sticking between the
Parting sand pattern and the mould or between mould halves
sand is a highly permeable sand, mixed with binders, used to make cores that form
Core sand Core
internal cavities in castings.
The choice of moulding materials is based on their processing properties.
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Moulding Materials Properties
is the ability of a material to withstand high temperatures without melting or breaking down, especially in foundry applications.
Refractoriness (To withstand the high temperatures)
Green strength is the strength of moulding sand in its moist (uncured) state, which allows it to retain shape during handling and
pattern removal.
Green Strength (Sand that contains moisture)
Dry strength is the strength of moulding sand after it has dried, allowing it to resist erosion and deformation during metal pouring
Dry Strength (Moisture is completely expelled)
Hot strength is the ability of moulding sand to retain its strength at high temperatures, especially during the pouring of molten
metal.
Hot Strength (All the moisture is eliminated)
Permeability (Gases are to be expelled)
Permeability is the ability of moulding sand to allow gases and steam to
pass through it during metal casting.
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Moulding Sand Composition
The main ingredients of any moulding sand are:
Silica grains (SiO2) (up to 96 %)
Clay as binder
Kaolinite or fire clay (Al2O3 2SiO2 2H2O)
Bentonite (Al2O3 4SiO2 H2O nH2O)
Moisture to activate the clay and provide plasticity (2% to 8%)
Besides, some other materials are also added to these to enhance the specific properties
of moulding sands.
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Quiz! Quiz!! Quiz!!!
Clay acts as a binder in moulding sand, providing cohesiveness and strength to help the sand retain its shape
during moulding and casting.
Common additive materials
1. Why clay is used in moulding sand?
include:
2. What are the additive materials used in moulding sand?
Wood flour (reduces sand
expansion)
Coal dust (improves surface finish)
Cereal binders (enhance strength)
3. What are the importance of testing sand properties?
4. What is Grain Fineness Number (GFN)?
Grain Fineness Number (GFN) is a measure of the average size of sand grains in moulding
sand. It affects surface finish, permeability, and strength of the mould.
Silica flour (improves hot strength)
Iron oxide (reduces metal
penetration)
Testing sand properties is important to ensure:
Good mould strength
Proper permeability
Dimensional accuracy
Defect-free casting
Reusability of sand
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Moulding Sand Properties
The properties of moulding sand are dependent to a great extent on a
number of variables.
● Sand grain shape and size
● Clay type and amount
● Moisture content
● Method of preparing sand mould
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Types of Sand Moulds (specific properties)
In order to produce sound castings, moulds are required to have some
specific properties.
It must be strong enough to withstand the temperature and weight of
the molten metal.
It must resist the erosive action of the flowing hot metal.
It should generate minimum amount of gases as a result of the
temperature of the molten metal.
It should have good venting capacity to allow the gene rated gases to
completely escape from it.
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Types of Sand Moulds
Moulds that are used for sand casting may broadly be classified as
Green sand moulds
Dry sand moulds
Skin dried moulds
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Green Sand Moulds
Advantage
Freshly prepared from silica grains, clay and moisture.
Metal is poured immediately and the castings taken out.
Most commonly used
Adapted for rapid production.
Require less floor space.
Least expensive.
Less tendency for hot tearing of the castings.
Discontinuity that occurs during
the solidification stage of a casting operation
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Green Sand Moulds
Disadvantage
Mould erosion is common.
The permeability of these moulds should be properly controlled
Otherwise blow holes and gas inclusions are likely to form.
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Dry Sand Moulds
Advantage
Green sand moulds
Completely dried in an oven from 150 to 350°C for 8 to 48 hours
Depends on the binders in the moulding sand.
Higher strength than the green sand mould
Generally used for medium to large castings.
Better surface finish and dimensional accuracy.
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Dry Sand Moulds
Disadvantages
Likely distortion of the mould caused during the baking process.
Susceptibility to hot tearing of castings
Longer production cycles.
Also this is more expensive than the green sand mould.
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Skin Dried Mould
Drying only the skin of the mould cavity .
With which the molten metal comes into contact, instead of the full
mould.
Skin dried to a depth of 15 to 25 mm,
Using either torches or by simply allowing them to dry in
atmosphere.
Pouring of metal should be completed immediately after the drying
process.
Such that moisture from the undried portion would not penetrate
the dried skin.
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Moulding Machines
• Hand moulding = Suitable for small batch production or for large size
castings.
• Machine moulding = For large batches of the same type of casting.
• Basically three methods used for ramming the sand into the moulding
flasks.
They are:
Jolting
Squeezing
Sand slinging
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Jolt moulding
The sand is first filled into the flask generally from an
overhead hopper
It is raised to a certain height.
Allowed to free fall on to a solid bed plate.
The resulting impact forces the sand to get
compacted uniformly into the mould.
This lifting and dropping process continues
repeatedly till the required mould hardness is
achieved.
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Jolt moulding
This type of ramming is suitable for horizontal surfaces.
It is very severe on the moulding equipment and also
Likely to give rise to uneven packing.
The sand at the bottom experiences the highest force
Bottom sand is packed well compared to the sand in the top layers.
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Squeeze ramming
A plate slightly smaller than the inside
dimensions of the flask.
Fitted into the flask already filled with the
moulding sand as shown in Fig. 3.38(a).
A uniform pressure
By either moving it down or by moving the
flask upwards.
The resulting force compacts the sand
uniformly.
The sand next to the plate rams hardest while
the sand below is progressively less hard.
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Sand slinging
Throwing sand into the flask rapidly and with great
force.
develops uniformly high mould hardness.
very fast and gives high uniform sand ramming.
The sand should be uniformly sprayed into the mould
by moving the nozzle through the entire area of the
flask.
Also it is necessary that the sand be sprayed in layers to
achieve uniform hardness.
However, the initial cost of the equipment is high.
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Cores
Cores are the materials used for making cavities and hollow
projections which cannot normally be produced by the pattern alone.
• Any complicated contour or cavity can be made by means of cores
• So really intricate shapes can be easily obtained.
• These are generally made of sand.
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Normal characteristics desired of a core
Green strength: before baking
Dry strength:
Refractoriness:
Permeability:
Collapsibility: (ability to decrease in size), to provide resistance against
shrinkage and thus can cause hot tears.
Friability: (the ability to crumble), core need to remove after casting
Smoothness: provide a good finish to the casting.
Low gas emission:
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Core Sands
• Contain the sand grains, binders and other additives.
• Coarse silica (higher refractoriness), is used in steel
foundries.
• The finer sands for cast irons and non–ferrous alloys.
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Core Sands
The binders generally used
Linseed oil,
Core oil,
Resins,
Dextrin,
Molasses, etc.
Core oils are mixtures of
• Linseed,
• Soy,
• Fish,
• Petroleum oils
• And coal tar.
The general composition of a core sand mixture could be core
oil (1%) and water (2.5 to 6%).
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Types of Cores
• The cores are essentially of two
types.
Green sand
Dry sand cores
1. Green sand
Disadvantage
• Obtained by the pattern itself during
moulding.
• Most economical way of preparing
core.
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 Green sand being low in strength.
 Cannot be used for fairly deep holes.
 Need a large amount of draft
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Types of Cores
2. Dry sand cores
Made by means of special core sands in a separate core box,
Baked and then placed in the mould before pouring.
Before the baking process, core is generally weak and should be well
supported.
But for slender and complicated cores it may be necessary to place the
core in the core box during the baking process.
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Types of Cores
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Core Prints
Provided so that the cores are securely and correctly positioned in
the mould cavity.
To take care of the weight of the core before pouring
And the upward metallostatic pressure of the molten metal after
pouring.
To ensure that the core is not shifted during the entry of the metal
into the mould cavity.
The main force acting on the core, when metal is poured into the
mould cavity, is due to buoyancy.
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Chaplets
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Chaplets
Metallic supports
Kept inside the mould cavity to support the cores.
These are of the same composition as that of the
pouring metal
So that the molten metal would provide enough heat
to completely melt them
And thus fuse with it during solidification.
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Chaplets
Disadvantage
 In practice it is difficult to melt the metal and normally
it forms a weak joint in the casting.
 The condensation of moisture which finally ends up as
blow holes.
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