lo 2 handout 1 (2) PART 2

Primary and Secondary
Manufacturing Processes
EMC-2033 Manufacturing Technology
Learning Outcome 2
Handout 1
1

LO 2: Distinguishbetweenprimaryand
secondarymanufacturingprocesses.
• Identify primary manufacturing processes:
• List secondary manufacturing processes relative to:
a) casting and moulding
b) forming
c) separating
d) conditioning
e) assembly
f) finishing
2

What is Manufacturing ?
• Manufacturing can be defined in two ways:
• Technologically: Manufacturing is the
application of physical and chemical processes
to alter the geometry , properties, and/or
appearance of a given starting material to
make parts or products.
• Manufacturing also includes assembly of
multiple parts to make products.
• The processes to accomplish manufacturing
involves a combination of machinery, tools,
power and labor.
3

Technical definition of
manufacturing
4

Economical definition
• Economically: Manufacturing is the
transformation of materials into items of greater
value by means of one or more processing
and/or assembly operations.
• The key point here is “Add value” to material by
changing its shape or properties, or by
combining it with another materials.
• Example: sand when converted into glass, value
is added.
• The words Manufacturing or Production are
often used interchangeably. 5

Economical definition of
manufacturing
6

Primary and Secondary Industries
• Industries are organizations or enterprises that
produce and supply goods and services.
• They can be classified as:
• Primary industries: that cultivate and exploit
natural resources, example mining, petroleum.
• Secondary industries: takes the output of
primary industries and convert them into
consumer and capital goods. Manufacturing is
principle activity here, example: steel making,
oil refinery, constructions.
• Tertiary industries: service sector, example
insurance, car repairs, banking…
7

Manufacturing Capabilities
• Any typical manufacturing plant consists of a set
of Processes, Systems, and Materials.
• These three building blocks Materials-Processes-
systems constitute the subject of modern
manufacturing.
• These factors are highly interdependence among
other.
• Manufacturing Capabilities: refers to the
technical and physical limitations of a
manufacturing firm and each of its plants. 8

Manufacturing Capabilities Dimensions
1. Technological processing capabilities: is the
available set of manufacturing processes in the
plant. Example: a steel rolling factory cannot
build automobiles.
2. Physical Product Limitations: a plant with a
given set of processes is limited in terms of the
size and weight of products that he can
accommodate. Large, heavy, different type
materials needs different equipment.
3. Production Capacity: the maximum rate of
production that a plant can achieve under
assumed operating conditions.
9

Manufacturing Processes
• Manufacturing Process: is a designed procedure
that results in physical and/or chemical changes
to a starting work material with the intention of
increasing the value of that material.
• A manufacturing process is usually carried out as
a unit operation, where a single step in the
sequence of steps required to transform the
starting material into a final product.
• Manufacturing processes can be divided into two
types: Processing operations, and Assembly
operations.
11

Processing operations &
Assembly operations
1. Processing operations: transforms a work
material from one state of completion to a
more advanced state that is closer to the final
desired product.
2. Assembly operations: joints two or more
components to create a new entity, called an
assembly, subassembly, or some other term
that refers to the joining process.
12

Manufacturing
Processes
Processing
operations
Shaping
Property
enhancing
Surface
processing
Assembly
operations
Permanent
joining
Mechanical
Fastening
13

Processing operations
• A processing operation uses energy to alter a
work part's shape, physical properties, or
appearance to add value to the materials.
• The forms of energy includes: Mechanical,
Thermal, Electrical, Chemical. The energy is
applied by a controlled means of machinery and
tooling.
• Processing operations categories are:
1. Shaping operation.
2. Property-Enhancing operation.
3. Surface processing operation.
14

I - Shaping operations
Shaping operation: most shaping operations apply
heat, mechanical force, or a combination of these
to effect a change in the geometry of the work
material. This includes:
1. Solidification processes
2. Particulate processing
3. Deformation process
4. Material removal process
• following slides explain the four processes. 15

1- Solidification Processes
• In solidification processes the starting material
is heated to liquid or semifluid that cools and
solidifies to form the part geometry.
• Nearly all materials can be processed this way if
it has relatively low melting point, such as
polymers, metals, and glass ceramics.
• The molted material is forced or poured into a
mold to form the required shape.
• Casting is the name used for metals, and molding
is the common term used for plasic. 16

18
Introduction: Casting
• Casting involves pouring molten metal into a mold cavity
• Process produce intricate shapes in one piece with internal
cavities
Copyright © 2010 Pearson Education South Asia Pte Ltd

19
Introduction

20
Important considerations in
casting
• Flow of molten metal into the mold cavity.
• Solidifacation and cooling of the metal in the mold.
• Influence of the type of mold material.

21
Why Casting processes are
selected?
Casting Process are most often selected over other manufacturing
methods for the below reasons:
Casting can produce complex shapes and can incorporated internal
cavities or hollow sections.
Very large parts can be produced in one piece.
Casting can utilize materials that are difficult or uneconomical to
process by other means.
The casting process can be economically competitive with other
manufacturing processes.

22
©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e
CASTING
PROCESSES
Sand casting for an
industrial pump. Holes
and surfaces have been
machined (courtesy of
George E. Kane
Manufacturing
Technology Laboratory,
Lehigh University)
CASTING PROCESSES

23
Open Mold
• Open Mold is simply a container of the desired shape of the part.
23

24
Closed Mold
• Mold geometry more complex and requires passageway or gating
system.
24

Closed Molds
• A passageway or gating system is provided to permit
the molten metal to flow from outside the mold into
the cavity.
• the closed mold is by far the more important
category in production casting operation.
• Casting processes divided into two broad categories,
according to type of mold used:
• Expendable mold: means the mold in which the
molten metal solidifies must be destroyed to
remove the casting (made from sand or plaster).
• Permanent Mold: the Mold used many times,
made from metal or ceramic refractories.
25

Sand Casting Elements
• Sand casting mold consist of:
• The cope: is the upper half of the mold.
• The drag: is the bottom half of the mold.
• The flask: the cope and drag are contained by this
box called the flask.
• The Pattern: In sand casting we need also the pattern;
it is the mold cavity shape made of wood, plastic, or
other material.
• The cavity is formed by packing sand around the
pattern, about half in the drag and half in the cope.
• The pattern is then removed to leave the cavity. 26

The pattern:
• For the production of small quantities of casting,
patterns are made from wood, smoothed
painted or varnished to give a smooth finish to
the casting.
• Patterns are made larger than the finished part
to allow for shrinkage of the casting when it
cools.
• A special rule, know as a contraction rule, is
available to suit different metals. 28

29
Types of Patterns
• Types of patterns used in sand casting: (a) solid pattern, (b) split
pattern, (c) match-plate pattern, (d) cope and drag pattern

30
• FIGURE 11.4 A typical metal match-plate pattern used in sand
casting.

31
• Where cores are to be incorporated in casting(See below),
provision must be made on the pattern to provide a location
seating in the mold. These section added to the pattern are
known as core prints.
• The Core: When a casting is to have a hollow section, a core must
be incorporated into the mold.
• Cores are inserted in the mold after the pattern is removed and
before the mold is closed. They are located and supported in the
mold in a seating formed by the core prints on the pattern.
• Core must be strong enough to support itself and withstand the
flow of metal, and in some cases it may be necessary to reinforce
it with wires to give added strength.
• Complex cores are produces from CO2 sand.
31

32
SandCastingElements
The Sand: molding sand must be permeable, i.e. porous to allow
the escape of gases and steam; strong enough to withstand the
mass of molten metal; resist high temperature and have a grain size
suited to the desired surface of the casting.
• Silicon sand is used in molding, the grains of the sand being held
together in different ways.
• In green sand molds the grains are held together by moist clay,
and the moisture level has to be carefully controlled in order to
produce satisfactory results.
• Dry sand molds start off in the same way as green sand molds but
the moisture is driven of heating the molds. This makes the mold
stronger and is suited for heavier castings.
• With CO2 sand the silica grain are coated with sodium silicate
instead of clay. When the mold, it is hardened by passing CO2 gas
for short period of time. The sand ‘Sets’ but is easily broken after
casting
32

33
Cylinder Block and its Cores
33

34
Expendable-mold,Permanent-patternCasting
Processes:SandCasting
The Sand-casting Operation

35
Heat Treatment
• Castings are often heat treated to enhance properties
• Reasons for heat treating a casting:
• For subsequent processing operations such as machining
• To bring out the desired properties for the application of the part
in service

36
Surface Cleaning and
Inspection
• Removal of sand from casting surface and otherwise enhancing
appearance of surface
• Cleaning methods: tumbling, air-blasting with coarse sand grit or
metal shot, wire brushing, buffing, and chemical pickling
• Surface cleaning is most important for sand casting
• Defects are possible in casting, and inspection is needed to detect
their presence

37
Foundry Inspection
Methods
• Visual inspection to detect obvious defects such as misruns,
cold shuts, and severe surface flaws
• Dimensional measurements to insure that tolerances have been
met
• Metallurgical, chemical, physical, and other tests concerned
with quality of cast metal

38
Casting Quality
• There are numerous opportunities for things to go wrong in a
casting operation, resulting in quality defects in the product
• The defects can be classified as follows:
• General defects common to all casting processes
• Defects related to sand casting process

39
Casting Defects
• Metallic Projections: such as fins, flash or projections
• Cavities: such as blow holes, pinholes and shrinkage cavities
• Discontinuities: such as cracks, cold or hot tearing, cold shuts
• Defective surface: such as surface folds, laps, scars, adhering sand
layers, and oxide scale.
• Incomplete casting: such as misruns,
• Incorrect dimensions or shape.
• Inclusions: generally non metallic slags

40
• FIGURE 10.12 Examples of hot tears in castings. These defects occur because the casting cannot shrink
freely during cooling, owing to constraints in various portions of the molds and cores. Exothermic (heat-
producing) compounds may be used (as exothermic padding) to control cooling at critical sections to avoid
hot tearing.

41
• FIGURE 10.13 Examples of common defects in castings; these defects can be minimized or eliminated by
proper design and preparation of molds and control of pouring procedures. Source: After J. Datsko.

42
• A casting that has
solidified before
completely filling mold
cavity
General Defects:
Misrun

43
• Two portions of metal flow
together but there is a lack
of fusion due to premature
freezing
General Defects:
Cold Shut

44
• Metal splatters during
pouring and solid globules
form and become
entrapped in casting
General Defects:
Cold Shot

45
• Depression in surface or
internal void caused by
solidification shrinkage that
restricts amount of molten
metal available in last
region to freeze
General Defects:
Shrinkage Cavity

46
• Balloon-shaped gas cavity
caused by release of mold
gases during pouring
Sand Casting Defects:
Sand Blow

47
• Formation of many small gas
cavities at or slightly below
surface of casting
Pin Holes

48
• Formation of many small gas
cavities at or slightly below
surface of casting
Pin Holes

49
• A step in the cast
product at parting line
caused by sidewise
relative displacement
of cope and drag
Mold Shift

50
Steps in Sand Casting
1. Pour the molten metal into sand mold
2. Allow time for metal to solidify
3. Break up the mold to remove casting
4. Clean and inspect casting
• Separate gating and riser system
5. Heat treatment of casting is sometimes required to improve
metallurgical properties

51
Making the Sand Mold
• The cavity in the sand mold is formed by packing sand around a
pattern, then separating the mold into two halves and
removing the pattern
• The mold must also contain gating and riser system
• If casting is to have internal surfaces, a core must be included in
mold
• A new sand mold must be made for each part produced

52
Overview of Sand Casting
• Most widely used casting process, accounting for a significant
majority of total tonnage cast
• Nearly all alloys can be sand casted, including metals with high
melting temperatures, such as steel, nickel, and titanium
• Castings range in size from small to very large
• Production quantities from one to millions

53
Expendable-mold
Sand
Casting
Permanent-pattern Casting
Processes:

54
FIGURE II.3 Outline of metal-casting processes described.

lo 2 handout 1 (2) PART 2

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