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EXPERIMENT-1

AIM: -TO EMPHASIS THE IMPORTANCE OF MANUFACTURING ACTIVITY AND TO GET AN

OVERVIEW AND SELECTION OF THE VARIOUS MANUFACTURING PROCESSES.

INTRODUCTION: -

The manufacturing process is the procedure followed in a plant for converting raw

materials or semi-finished products into finished products. In order for the manufactured product

to be economically competitive in the market, manufacturing must be done at the lowest possible

cost with acceptable quality.

When the manufacturing of an industrial organization decides, on the basis of market

survey and cost estimates, that a product as designed can be profitably manufactured, the following

steps are initiated for its manufacture:

A typical example of manufacturing is schematically shown in Figure

OBJECTIVES

(i) Identify the necessity of “manufacturing”

(ii) Define with examples the concept of “manufacturing”

(iii) List the main classifications of the manufacturing processes with examples

(iv) State the main purposes of “machining”

(v) Define with examples the concept of “machining”

(vi) State with example the principles of “machining”

(vii) State with examples the main requirements for “machining”

(viii) State with examples the main functions of “Machine tools”

(ix) Define the concept of “machine tools

RAW MATERIAL

MACHINE TOOL

FINISHED PRODUCT PRODUCT

MACHINING PROCESSES

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CLASSIFICATION OF MANUFACTURING PROCESS: -

BASED ON THE FUCTION OF PROCESS

1. PROCESS FOR CHANGING PHYSICAL PROPERTIES OF THE MATERIAL

It can be changed by Heat Treatment like

HARDENING

ANNEALING

FULL ANNEALING

NORMALIZING

PROCESS ANNEALING

STRESS RELIEF ANNEALING

CARBONIZING

SHOT PEENING

TEMPERING

SURFACE HARDENING

Heat treatment is the best method of changing properties of metals.

MANUFACTURING PROCEESEES

BASED ON THE FUCTION OF PROCESS BASED ON QUANTITY OF PRODUCTION

1. PROCESS FOR CHANGING PHYSICAL

PROPERTIES OF THE MATERIAL.

2. CASTING PROCESSES

3. PRIMARY METAL WORKING PROCESSES

4. SHEARING AND FORMING PROCESSES

5. JOINING PROCESSES

6. MACHINING PROCESSES

7. SURFACE FINISH PROCESSES

1. UNIT OR PIECE PRODUCTION

2. BATCH OR LOT PRODUCTION

3. MASS PRODUCTION

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2. CASTING PROCESSES

It Is A Process In Which Molten Metal Flows Into A Mold Where It Solidified In The Shape Of The

Mold Cavity. The Part Produced Is Also Called CASTING.

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3. PRIMARY METAL WORKING PROCESSES

These Processes Produce What Are Known As Wrought Metals Which Are Important

Engineering Materials Because Of Their Strength And Toughness.

Although Much Of The Output From Primary Metal Working Processes Is In The Final Form

Andmay Be Used Directly, A Considerable Quantity Of These Products Is Fed To Secondary

Processes That Make Finished Goods By Cutting Or Forming.

Common Primary Metal Working Processes Include

METAL ROLLING

COLD DRAWING

PIPE & TUBE MANUFACTURING PROCESSES

FORGING

EXTRUSION

4. SHEARING AND FORMING PROCESSES

A Large Proportion Of Products If Industry Are Manufactured By Shearing And Forming Of

Sheet Metal Into Finished Parts.

The Machines And Tools Used In These Processes Include Shears,Punches,Dies And Press.

SHEARING

DRAWING

FORMING

STRETCHING

BLANKING

PIERCING.

5. METAL JOINING PROCESSES

WELDING

SOLDERING3

BRAZING

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WELDING

Welding is the process of metallurgical joining of metals by application of heat or pressure or both.

It produces a permanent joint. Welding is one of the most important methods of joining metals. It is

used extensively in the manufacture of structures, automobile bodies, aircraft, railway wagons,

machine frames and in general machine shop work.

CLASSIFICATION BASED ON METHOD OF HEAT GENERATION AND APPLICATION: -

(1) Gas welding processes:

1. Oxyacetylene welding.

2. Oxy hydrogen welding.

(2) Arc welding processes:

1. Shielded metal arc welding.

2. Contact arc welding.

3. Carbon arc welding.

4. Twin carbon arc torch welding.

5. Submerged arc welding.

6. Inert gas shielded metal arc welding.

7. Flux cored arc welding.

8. Atomic hydrogen welding.

9. Stud welding.

10. Plasma arc welding.

11. Electro slag welding.

12. Electro gas welding.

(3) Resistance welding processes:

1. Spot welding.

2. Seam welding.

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3. Roll spot welding.

4. Upset welding.

5. Flash welding.

6. Projection welding.

(4) Solid state welding processes:

1. Forge welding.

2. Friction welding.

3. Explosive welding.

4. Ultrasonic welding.

5. Cold pressure welding.

6. Thermo compression welding.

7. Diffusion welding.

(5) Radiant energy welding processes:

1. Electron beam welding.

2. Laser welding.

(6) Thermit welding:

1. Thermit welding.

2. Cad welding.

3. Pressure Thermit welding.

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BASIC ARC WELDING WORKING

Arc welding is fusion welding process. Heat source is developed by electric arc. Electric Arc

is used to heat and melt the materials which are required to join. Due to electric flow positive

charged ions tries towards cathode through air gap. At the same time negative charged electrodes

and metal. By this arc electric energy is converted in heat energy. This heat is used to melt the

material. Temperature of arc is 6000 degree to 7000 degree C. This temperature depends on type of

electrode, air-gap distance and electric pressure. Electrode also melts by this heat source. Electric

supply used in arc welding is having range of 15 to 60 volt and 25 to 800 ampere current. A supply

either A.C. or D.C. supply is used in arc welding.

6. MACHINING PROCESSES

It Is A Process In Which We Have Produced A Job By Removing Material From It With The

Used Of Machine Tools And Cutting Tools.

Some processes of these are.

TURNING

FACING

SHAPING

DRILLING

REAMING

PLANNING

MILLING

SLOTING

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7. SURFACE FINISHING PROCESSES

It Is Used to Ensure A Smooth Surface To Improve Appearance Or To Provide A Protective

Coating.

Its includes:

BUFFING

LAPPING

POLISHING

HONNING

GRINDING

ABRASIVE BELT GRINDING

ELECTOPLATING

(B) BASED ON QUANTITY OF PRODUCTION

1. UNIT OR PIECE PRODUCTION

It a production system in which we cannot produced a job again n again of same geometrical

features.

2. BATCH OR LOT PRODUCTION

In this type of production we have to manufacture job for special one batch or lot size after that the

machining processes will change for another batch or lot.

3. MASS PRODUCTION

In mass production we produced a same geometrical shape product again and again in large

number of products.

MANUFACTURING COST

This Is The Final Price Of Product Which Can Be Estimate With Used Of Several Costs And

We Must Continuously Strive To Produce Its Products At The Lowest Cost And With A Good

Quality That Meets The Customer Requirements.

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COMPONENT OF COST

SELECTION OF THE MANUFACTURIGN PROCESS

The Selection Of The Manufacturing Process To The Used For Any Product Calls For A

Balanced Consideration Of All The Factors Discuss As Far:

It Is Based On The Following Factors.

1. The Material And The Shape Of The Product

2. The Quantity Required To Be Produced

3. The Surface Finish And Accuracy Desired

\ EXERSISE

Q.1 Classify different manufacturing process.

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EXPERIMENT-2

AIM: STUDY OF PATTERNS AND PATTERN MAKING.

INTRODUCTION TO PATTERN:

A pattern may be defined as a model of desired casting which when molded in sand forms an

impression called mould. The mould when filled with the molten metal forms casting after

solidification of the poured metal. The quality and accuracy of casting depends upon the pattern

making. The pattern may be made of wood, metal(cast iron, brass, aluminum and alloy steel.),

plaster, plastics and wax.

The following FACTORS affect the choice of a PATTERN.

(i) Number of Castings to be produced.

(ii) Size and complexity of the shape and size of casting

(iii) Type of molding and castings method to be used.

(iv) Machining operation

(v) Characteristics of castings

DIFFERENT TYPES OF PATTERNS:

The common types of patterns are:

1. Single piece pattern

2. Split piece pattern

3. Loose piece pattern

4. Gated pattern

5. Match pattern

6. Sweep pattern

7. Cope and drag pattern

8. Skeleton pattern

9. Shell pattern

10. Follow board patter

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1. Single piece pattern: This is the simplest type of pattern, exactly like the desired casting. For making a mould, the pattern is accommodated either in cope or drag. Used for producing a few large castings, for example, stuffing box of steam engine.

2. Split pattern: These patterns are split along the parting plane (which may be flat or irregular surface) to facilitate the extraction of the pattern out of the mould before the pouring operation. For a more complex casting, the pattern may be split in more than two parts.

3. Loose Piece Pattern: When a one piece solid pattern has projections or back drafts which lie above or below the parting plane, it is impossible to with draw it from the mould. With such patterns, the projections are made with the help of loose pieces. One drawback of loose feces is that their shifting is possible during ramming.

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4. Gated pattern:

A gated pattern is simply one or more loose patterns having attached gates and runners.Because of their higher cost, these patterns are used for producing small castings in mass production systems and on molding machines.

5. Match plate pattern:

A match plate pattern is a split pattern having the cope and drags portions mounted

on opposite sides of a plate (usually metallic), called the "match plate" that conforms

to the contour of the parting surface.

The gates and runners are also mounted on the match plate, so that very little hand

work is required. This results in higher productivity. This type of pattern is used

for a large number of castings.

Piston rings of I.C. engines are produced by this process.

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6. Sweep pattern:

A sweep is a section or board (wooden) of proper contour that is rotated about one

edge to shape mould cavities having shapes of rotational symmetry. This type of

pattern is used when a casting of large size is to be produced in a short time. Large

kettles of C.I. are made by sweep patterns.

7. Cope and drag pattern:

A cope and drag pattern is a split pattern having thecope and drag portions each

mounted on separate match plates. These patterns are used when in the production

of large castings; the complete moulds are too heavy and unwieldy to be handled by

a single worker.

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8. Skeleton pattern:

For large castings having simple geometrical shapes, skeleton patterns are used. Just

like sweep patterns, these are simple wooden frames that outline the shape of

the part to be cast and are also used as guides by the molder in the hand shaping of

the mould.

9. Shell pattern:

10. Follow board pattern:

A follow board is not a pattern but is a device (wooden board) used for

various purposes.

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PATTERN ALLOWANCES:

A pattern is always made larger than the required size of the casting considering the

various allowances. These are the allowances which are usually provided in a pattern.

1: Shrinkage or contraction allowance:

The various metals used for casting contract after solidification in the mould. Since the

contraction is different for different materials, therefore it will also differ with the form or

type of metal.

2: Draft allowance

It is a taper which is given to all the vertical walls of the pattern for easy and clean

withdraw of the pattern from the sand without damaging the mould cavity. It may be

expressed in millimeters on a side or in degrees. The amount of taper varies with the type

of patterns. The wooden patterns require more taper than metal patterns because of the

greater frictional resistance of the wooden surfaces.

3: Finish or machining allowance

The allowance is provided on the pattern if the casting is to be machined. This allowance is

given in addition to shrinkage allowance. The amount of this allowance varies from 1.6 to

12.5 mm which depends upon the type of the casting metal, size and the shape of the

casting. The ferrous metals require more machining allowance than non ferrous metals.

4: Distortion or camber allowance

This allowance is provided on patterns used for casting of such design in which the

contraction is not uniform throughout.

5: Rapping or shaking allowance

This allowance is provided in the pattern to compensate for the rapping of mould because

the pattern is to be rapped before removing it from the mould.

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PATTERN MATERIALS

It has Following Properties

1. Easy to work, shape and join

2. Strong, hard and durable so as to be resistant to wear

3. Light in weight

4. Dimensionally stable

5. Cheap and easily available

6. Resistant to corrosion and chemical action

The Pattern materials are

Wood

Metal

Plastics

Plaster

PATTERN DESIGN CONSIDERATIONS

1. Nature of the parting line

2. Provision of suitable core prints

3. Selection of a suitable pattern material and method of pattern making

4. Provision of adequate allowances

5. Filleting and sharp corners

EXERSISE

Q.1 Explain deffernt types of pattern allowances with help of neat sketches.

Q.1 Explain deffernt types of pattern with help of neat sketches.

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EXPERIMENT-3

AIM:-TO UNDERSTAND THE BASICS OF SAND CASTING AND IT’S PREPARATION.

INTRODUCTION TO SAND CASTING

Sand casting, the most widely used casting process, utilizes expendable sand molds to form

complex metal parts that can be made of nearly any alloy. Because the sand mold must be

destroyed in order to remove the part, called the casting, sand casting typically has a low

production rate. The sand casting process involves the use of a furnace, metal, pattern, and sand

mold. The metal is melted in the furnace and then ladled and poured into the cavity of the sand

mold, which is formed by the pattern. The sand mold separates along a parting line and the

solidified casting can be removed.

CHARACTERISTICS OF MOULDING SANDS

1. It can withstand temperature of the metal without fusing.

2. Do not chemically react.

3. It has high degree of permeability and thus the gases formed during pouring

to escape

4. The strength, permeability and hardness of the sand mix can be varied by

changing the structure or ingredients of sand.

5. Do not combine with molten metal.

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PROPERTIES OF MOULDING SAND

1. Refractoriness

This refers to the sand's ability to withstand the temperature of the liquid metal being cast without breaking down. For example some sands only need to withstand 650 °C (1,202 °F) if casting aluminum alloys, whereas steel needs a sand that will withstand 1,500 °C (2,730 °F). Sand with too low a refractoriness will melt and fuse to the casting.

2. Chemical inertness

The sand must not react with the metal being cast. This is especially important with highly reactive metals, such as magnesium and titanium.

3. Permeability

This refers to the sand's ability to exhaust gases. This is important because during the pouring process many gases are produced, such as hydrogen, nitrogen, carbon dioxide, and steam, which must leave the mold otherwise casting defects, such as blow holes and gas holes, occur in the casting. Note that for each cubic centimeter (cc) of water added to the mold 16,000 cc of steam is produced.

4. Surface finish

The size and shape of the sand particles defines the best surface finish achievable, with finer particles producing a better finish. However, as the particles become finer (and surface finish improves) the permeability becomes worse.

5. Cohesiveness

This is the ability of the sand to retain a given shape after the pattern is removed.

6. Flowability

The ability for the sand to flow into intricate details and tight corners without special processes or equipment.

7. Collapsibility

This is the ability of the sand to be easily stripped off the casting after it has solidified. Sands with poor collapsibility will adhere strongly to the casting. When casting metals that contract a lot during cooling or with long freezing temperature ranges a sand with poor collapsibility will cause cracking and hot tears in the casting. Special additives can be used to improve collapsibility.

CLASSIFICATION OF MOULDING SAND

1. GREEN SAND

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A green sand mold is very typical in sand casting manufacture, it is simple and easy to make, a

mixture of sand, clay and water. The term green refers to the fact that the mold will contain

moisture during the pouring of the casting.

Manufacturing Considerations And Properties Of Green Sand Molds:

Has sufficient strength for most sand casting applications Good collapsibility Good permeability Good reusability Least expensive of the molds used in sand casting manufacturing processes Moisture in sand can cause defects in some castings, dependent upon the type of metal used.

2. Dry Sand Molds:

Dry sand molds are baked in an oven, (at 300F - 650F for 8-48 hours), prior to the sand casting

operation, in order to dry the mold. This drying strengthens the mold, and hardens its internal

surfaces. Dry sand molds are manufactured using organic binders rather than clay.

Manufacturing Considerations And Properties Of Dry Sand Molds:

Better dimensional accuracy of sand cast part than green sand molds Better surface finish of sand cast part than green sand molds More expensive manufacturing process than green sand production Manufacturing production rate of castings are reduced due to drying time Distortion of the mold is greater, (during mold manufacture) The metal casting is more susceptible to hot tearing because of the lower collapsibility of

the mold Dry sand casting is generally limited to the manufacture of medium and large castings

3. Skin Dried Molds:

When sand casting a part by the skin dried mold process a green sand mold is employed, and its

mold cavity surface is dried to a depth of .5 - 1 inch. Drying is a part of the manufacturing process

and is accomplished by use of torches, heating lamps or some other means, such as drying it in air.

4. Loam Mold

5. Parting Mold

6. Facing Mold

7. Backing Mold

8. System Mold

9. Core Sand

SAND TESTING

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It is established for finding the desire properties of the sand described above. The tests performed

for the same are:

1. REFRACTORINESS TEST

2. SAND TEXTURE TEST

3. CLAY CONTENT TEST

4. MOISTURE TEST

5. PERMEABILITY TEST

6. FLOWABILITY TEST

SAND PREPARATION

It’s include Major Three steps.

1. MIXING OF SAND 2. TEMPERING OF SAND 3. SAND CONDITIONING

1. MIXING OF SAND

It is a process of mixing of silica with other constituents to get desired combination of properties.

Mostly other constitutes are used like clay, lime, magnesia, potash, soda, sawdust, etc.

2. TEMPERING OF SAND

It is process of adding sufficient quantity of water to the sand.

3. SAND CONDITIONING

It is a process of preparing the molding sand to make it suitable for tge ramming in flasks so that it flows ready and fills all the details.

EXERSISE

Q.1 Explain different types of Sand used in foundry.

Q.2 Explain properties of molding sand.

Q.3 Explain molding sand tests with help of neat sketch.

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EXPERIMENT-4

AIM:-TO KNOW THE FOUNDAMENTAL OF MOLD & MOULD MAKING.

INTRODUCTION

Moulding is the process of manufacturing by shaping liquid or pliable raw material using a rigid frame called a mould This itself may have been made using a pattern.A mold or mould is a hollowed-out block that is filled with a liquid or pliable material like plastic, glass, metal, or ceramic raw materials. The liquid hardens or sets inside the mold, adopting its shape.

The manufacturer who makes the molds is called the Mold-Maker. A release agent is typically used to make removal of the hardened/set substance from the mold easier.

Most mould made in two parts, the top part is called COPE and bottom part is called DRAG.

it is held in good manner by aligning pins and lugs.

In some of the mould the additional intermediate boxes called CHEEKS may be required.

IMPORTANT CHARACTERISTICS OF MOULD

1. It is strong enough to resist erosion by the flow of the metal

2. Mould material should not produce too much of gases as the gases may enter the mould.

3. It made like that the gases automatically go outside the mould.

4. It is collapsible easily after metal solidification.

5. Must have good Risering system.

6. Cleaning of castings is facilitated.

7. It provide smooth path to flow the molten metal.

HAND TOOL USED FOR THE MOULDING

1. Riddles

2. Rammers

3. Strike

4. Trowels

5. Vent wires

6. Draw spike

7. Lifter

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8. Gate cutter

9. Sprue cutters

10. Bellows

11. Gaggers

12. Swab

13. Smoother

14. Ruuner & Riser pins

15. Clamp & Bolts

TYPES OF SAND MOULDS

1. Green sand Mould

2. Skin dried Mould

3. Dry sand Mould

4. Loam sand Mould

5. Furan Mould

6. Carbon Dioxide Mould

1. GREEN SAND MOULD

A green sand mold is very typical in sand casting manufacture, it is simple and easy to make, a

mixture of sand, clay and water. The term green refers to the fact that the mold will contain

moisture during the pouring of the casting.

Manufacturing Considerations And Properties Of Green Sand Molds:

Has sufficient strength for most sand casting applications Good collapsibility Good permeability Good reusability Least expensive of the molds used in sand casting manufacturing processes Moisture in sand can cause defects in some castings, dependent upon the type of metal used.

2. DRY SAND MOULD

Dry sand molds are baked in an oven, (at 300F - 650F for 8-48 hours), prior to the sand casting

operation, in order to dry the mold. This drying strengthens the mold, and hardens its internal

surfaces. Dry sand molds are manufactured using organic binders rather than clay.

Manufacturing Considerations And Properties Of Dry Sand Molds:

Better dimensional accuracy of sand cast part than green sand molds Better surface finish of sand cast part than green sand molds More expensive manufacturing process than green sand production Manufacturing production rate of castings are reduced due to drying time

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Distortion of the mold is greater, (during mold manufacture) The metal casting is more susceptible to hot tearing because of the lower collapsibility of

the mold Dry sand casting is generally limited to the manufacture of medium and large castings

3. SKIN DRIED MOULD

When sand casting a part by the skin dried mold process a green sand mold is employed, and its

mold cavity surface is dried to a depth of .5 - 1 inch. Drying is a part of the manufacturing process

and is accomplished by use of torches, heating lamps or some other means, such as drying it in air.

4. LOAM SAND MOULD

It is built up with unburnt bricks or large cast iron parts and plasters with thick loam mortar. It is

used for building and facing of mould. This mould is dried before pouring and it is also time

consuming.

5. FURAN MOULD

Furan Moulds make use of a chemical resin-furan to reduce the time gap between making a mould

and pouring. It is made by first mulling clay free silica sand with phosphoric acid which works as an

activator.

It is hard enough within a couple of hours to allow cores to be assembled and the metal to be

poured.

6. CARBON DIOXIDE MOULD

It is used for harden the mould. The bonding strength obtained is sufficient to permit pouring of the

mould without the need for any drying and baking. It is also used for making cores. It results high

accuracy and good surface finish and this mould is used ofr all sizes of casting.

EXERSISE

Q.1 Explain different types of mould used in foundry.

Q.2 Explain properties of good sand mould.

Q.3 Explain tolls used in moulding with help of neat sketch.

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EXPERIMENT-5

AIM:-TO STUDY OF CORE AND CORE MAKING.

INTRODUCTION

CORES are pieces that are placed into casting moulds to form internal cavities of the casting, or to

form extra sections of the mould for castings that have external projections or negative draft, which,

if included in the pattern, would prevent the pattern from being removed from the mould. Multiple

cores may be used in complex castings.

Cores can be made from metal (in shapes that are easily removed from the casting, and used in

permanent mould processes) or chemically bonded sand (complex shapes, and used in all mould

types). Metal cores need to be configured such that they are parallel to the mould parting line, or

can be removed before the casting is removed from the mould, and shaped so that is readily freed

from the casting.

Metal cores are typically made from cast iron or steel. Sand cores are made from materials similar

to those used for chemically bonded sand moulds. These cores are formed in core boxes - similar to

pattern boxes used to make moulds.

REQUIREMENTS

There are seven requirements for core

1. In the green condition there must be adequate strength for handling.

2. In the hardened state it must be strong enough to handle the forces of casting; therefore the

compression strength should be 100 to 300 psi (0.69 to 2.07 MPa).

3. Permeability must be very high to allow for the escape of gases.

4. As the casting or molding cools the core must be weak enough to break down as the

material shrinks. Moreover, they must be easy to remove during shakeout.

5. Good refractoriness is required as the core is usually surrounded by hot metal during

casting or molding.

6. A smooth surface finish.

7. A minimum generation of gases during metal pouring.

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CORE BOXES

It is like a pattern made of wood into which sand is rammed to form a core. Its gives the shape of

core. There are many types of boxes available and they are:

1. Half core box

2. Dump core box

3. Split core box

4. Strickle box

5. Gang box

METHOD OF CORE MAKING

Preparation of core sand mix Core making Core drying and baking Core finishing

EXERSISE

Q.1 Explain different types Cores used in foundry.

Q.2 Differences between core, core box and core print.

Q.3 Explain molding sand tests with help of neat sketch.

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EXPERIMENT-6

AIM:-TO UNDERSTAND THE CONCEPT OF CASTING AND CASTING METHODS.

INTRODUCTION

Virtually nothing moves, turns, rolls, or flies without the benefit of cast metal products. The metal

casting industry plays a key role in all the major sectors of our economy. There are castings in

locomotives, cars trucks, aircraft, office buildings, factories, schools, and homes. Figure some metal

cast parts.

Metal Casting is one of the oldest materials shaping methods known. Casting means pouring molten

metal into a mold 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 mold either by breaking the mold or taking the mold

apart. The solidified object is called the casting. By this process, intricate parts can be given

strength and rigidity frequently not obtainable by any other manufacturing process. The mold, into

which the metal is poured, is made of some heat resisting material. Sand is most often used as it

resists the high temperature of the molten metal. Permanent molds of metal can also be used to cast

products.

ADVANTAGES

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1. Molten material can flow into very small sections so that intricate shapes can be made by

this process. As a result, many other operations, such as machining, forging, and welding,

can be minimized or eliminated.

2. It is possible to cast practically any material that is ferrous or non-ferrous.

3. As the metal can be placed exactly where it is required, large saving in weight can be

achieved.

4. The necessary tools required for casting molds are very simple and inexpensive. As a result,

for production of a small lot, it is the ideal process.

5. There are certain parts made from metals and alloys that can only be processed this way.

LIMITATIONS

1. Dimensional accuracy and surface finish of the castings made by sand casting processes are

a limitation to this technique. Many new casting processes have been developed which can

take into consideration the aspects of dimensional accuracy and surface finish. Some of

these processes are die casting process, investment casting process, vacuum-sealed molding

process, and shell molding process.

2. The metal casting process is a labor intensive process

CASTING TERMS

FLASK

A metal or wood frame, without fixed top or bottom, in which the mold is formed. Depending upon

the position of the flask in the molding structure, it is referred to by various names such as drag

?lower molding flask, cope ? upper molding flask, cheek ? intermediate molding flask.

PATTERN

It is the replica of the final object to be made. The mold cavity is made with the help of

pattern.

PARTING LINE

This is the dividing line between the two molding flasks that makes up the mold.

MOLDING SAND

Sand, which binds strongly without losing its permeability to air or gases. It is a mixture of silica

sand, clay, and moisture in appropriate proportions.

FACING SAND

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The small amount of carbonaceous material sprinkled on the inner surface of the mold cavity to

give a better surface finish to the castings.

CORE

A separate part of the mold, made of sand and generally baked, which is used to create openings

and various shaped cavities in the castings.

POURING BASIN

A small funnel shaped cavity at the top of the mold into which the molten metal is poured.

SPRUE

The passage through which the molten metal, from the pouring basin, reaches the mold cavity. In

many cases it controls the flow of metal into the mold.

RUNNER:

The channel through which the molten metal is carried from the sprue to the gate.

GATE

A channel through which the molten metal enters the mold cavity.

CHAPLET

Chaplets are used to support the cores inside the mold cavity to take care of its own weight and

overcome the metallostatic force.

RISER

A column of molten metal placed in the mold to feed the castings as it shrinks and solidifies. Also

known as ?feed head?.

VENT

Small opening in the mold to facilitate escape of air and gases.

CASTING PROCESSES

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There are many casting processes like:

CENTRIFUGAL CASTING

In this process, the mold is rotated rapidly about its central axis as the metal is poured into it.

Because of the centrifugal force, a continuous pressure will be acting on the metal as it solidifies.

The slag, oxides and other inclusions being lighter, get separated from the metal and segregate

towards the center. This process is normally used for the making of hollow pipes, tubes, hollow

bushes, etc., which are axisymmetric with a concentric hole. Since the metal is always pushed

outward because of the centrifugal force, no core needs to be used for making the concentric hole.

The mold can be rotated about a vertical, horizontal or an inclined axis or about its horizontal and

vertical axes simultaneously. The length and outside diameter are fixed by the mold cavity

dimensions while the inside diameter is determined by the amount of molten metal poured into

the mould.

ADVANTAGES

Formation of hollow interiors in cylinders without cores

Less material required for gate

Fine grained structure at the outer surface of the casting free of gas and shrinkage cavities

and porosity

DISADVANTAGES

More segregation of alloy component during pouring under the forces of rotation

Contamination of internal surface of castings with non-metallic inclusions

Inaccurate internal diameter

INVESTMENT CASTING PROCESS

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The root of the investment casting process, the cire perdue or ?lost wax? method dates back to at

least the fourth millennium B.C. The artists and sculptors of ancient Egypt and Mesopotamia used

the rudiments of the investment casting process to create intricately detailed jewelry, pectorals and

idols. The investment casting process alos called lost wax process begins with the production of

wax replicas or patterns of the desired shape of the castings. A pattern is needed for every casting

to be produced. The patterns are prepared by injecting wax or polystyrene in a metal dies. A

number of patterns are attached to a central wax sprue to form a assembly. The mold is prepared

by surrounding the pattern with refractory slurry that can set at room temperature. The mold is

then heated so that pattern melts and flows out, leaving a clean cavity behind. The mould is further

hardened by heating and the molten metal is poured while it is still hot. When the casting is

solidified, the mold is broken and the casting taken out.

ADVANTAGES

Formation of hollow interiors in cylinders without cores

Less material required for gate

Fine grained structure at the outer surface of the casting free of gas and shrinkage cavities

and porosity

DISADVANTAGES

More segregation of alloy component during pouring under the forces of rotation

Contamination of internal surface of castings with non-metallic inclusions

Inaccurate internal diameter

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CERAMIC SHELL INVESTMENT CASTING PROCESS

The basic difference in investment casting is that in the investment casting the wax pattern is

immersed in a refractory aggregate before dewaxing whereas, in ceramic shell investment casting a

ceramic shell is built around a tree assembly by repeatedly dipping a pattern into a slurry

(refractory material such as zircon with binder). After each dipping and stuccoing is completed, the

assembly is allowed to thoroughly dry before the next coating is applied. Thus, a shell is built up

around the assembly. The thickness of this shell is dependent on the size of the castings and

temperature of the metal to be poured.

After the ceramic shell is completed, the entire assembly is placed into an autoclave or flash fire

furnace at a high temperature. The shell is heated to about 982 o C to burn out any residual wax and

to develop a high-temperature bond in the shell. The shell molds can then be stored for future use

or molten metal can be poured into them immediately. If the shell molds are stored, they have to be

preheated before molten metal is poured into them.

ADVANTAGES

excellent surface finish

tight dimensional tolerances

machining can be reduced or completely eliminated

VACUUM SEALED MOLDING PROCESS

It is a process of making molds utilizing dry sand, plastic film and a physical means of binding using

negative pressure or vacuum. V-process was developed in Japan in 1971. Since then it has gained

considerable importance due to its capability to produce dimensionally accurate and smooth

castings. The basic difference between the V-process and other sand molding processes is the

manner in which sand is bounded to form the mold cavity. In V-process vacuum, of the order of 250

– 450 mm Hg, is imposed to bind the dry free flowing sand encapsulated in between two plastic

films. The technique involves the formation of a mold cavity by vacuum forming of a plastic film

over the pattern, backed by unbounded sand, which is compacted by vibration and held rigidly in

place by applying vacuum. When the metal is poured into the molds, the plastic film first melts and

then gets sucked just inside the sand voids due to imposed vacuum where it condenses and forms a

shell-like layer. The vacuum must be maintained until the metal solidifies, after which the vacuum

is released allowing the sand to drop away leaving a casting with a smooth surface. No shakeout

equipment is required and the same sand can be cooled and reused without further treatment.

HIGH PRESSURE DIE CASTING

Method of producing precision castings with a high level of automation, and hence high

productivity. A permanent mould or die, made up of several parts has liquid metal injected into it,

using a hydraulic piston, at pressures typically between 20 and 100MPa, depending on the alloy.

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The mould abdorbs the stresses of injection, dissipates the heat, and ejects the casting before

resetting for the next casting cycle.

LOW PRESSURE DIE CASTING

A metal mould, or die, is mounted on a above a sealed furnace containing molten metal. A riser tube

connects the bottom of the die to the molten metal bath. The chamber containing the molten metal

is pressureised (typically 20-100kPa), and the metal is forced up into the mould. Once the casting

has solidified, the pressure is released and the molten metal falls back into the bath, and the casting

ejected in preparation for the next cycle.

At there is only one riser and no feeders, the casting yield is very high. Clearly, long casting runs are

important to justify the cost of the dies.

GRAVITY DIE CASTING

A permanent mould casting process, where the molten metal is poured from a vessel of ladle into

the mould, and the cavity fills with no force other than gravity, in a similar manner to the

production of sand castings, although filling can be controlled by tilting the die.

The advantages over sand castings include better surface finish, and better mechanical properties,

which occur due to relatively fasted cooling rates that occur in die casting.

DIE CASTING GRAVITY DIE CASTING

PLASTER-MOLD CASTING

Mold is made of plaster. Mixed with water and additives

and poured over a pattern. After plaster sets, pattern is

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removed and the mold is dried at 120oC and Have low permeability – gases can not escape.Have

fine details and good surface finish

Patterns are made of:

– Al alloys,

– Thermosetting plastics

– Brass or Zinc alloys

CERAMIC MOULD CASTING

It isSimilar to plaster-mold processand Uses refractory

mold materials. It is Suitable for high temperature

applications

Mixture made of:

– Fine grained zircon

– Aluminum oxide

– Silica

– Mixture is mixed with bonding agents and poured over pattern

Mixture is mixed with bonding agents and poured over pattern and Molds are baked in an oven.

Molds can be used to cast high-temperature alloys and Castings have good surface finishes.Good

dimensional accuracy can be achieved.

EXERSISE

Q.1 Explain investment casting .

Q.2 Difference between true centrifugal casting and semi centrifugal casting.

Q.3 Explain slush casting with help of neat sketch.

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INTRODUCTION

Solid materials need to be joined together in order that they may be fabricated into useful shapes

for various applications such as industrial, commercial, domestic, art ware and other uses.

Depending on the material and the application, different joining processes are adopted such as,

mechanical (bolts, rivets etc.), chemical (adhesive) or thermal (welding, brazing or soldering).

Thermal processes are extensively used for joining of most common engineering materials, namely,

metals. This exercise is designed to demonstrate specifically: gas welding, arc welding, resistance

welding, brazing.

WELDING PROCESSES

Welding is a process in which two materials, usually metals, and is permanently joined together by

coalescence, resulting from temperature, pressure, and metallurgical conditions. The particular

combination of temperature and pressure can range from high temperature with no pressure to

high pressure with any increase in temperature. Thus, welding can be achieved under a wide

variety of conditions and numerous welding processes have been developed and are routinely used

in manufacturing.

To obtain coalescence between two metals following requirements need to be met: (1) perfectly

smooth, flat or matching surfaces, (2) clean surfaces, free from oxides, absorbed gases, grease and

other contaminants, (3) metals with no internal impurities. These are difficult conditions to obtain.

Surface roughness is overcome by pressure or by melting two surfaces so that fusion occurs.

Contaminants are removed by mechanical or chemical cleaning prior to welding or by causing

sufficient metal flow along the interface so that they are removed away from the weld zone friction

welding is a solid state welding technique. In many processes the contaminants are removed by

fluxing agents.

EXPERIMENT-7

AIM: -TO UNDERSTAND THE BASIC CONCEPT OF WELDING AND FAMILIARIZATION WITH GAS CUTTING AND WELDING.

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The production of quality welds requires (1) a satisfactory heat and/or pressure source, (2) a

means of protecting or cleaning the metal, and (3) caution to avoid, or compensate for, harmful

metallurgical effects.

CLASSIFICATION OF WELDING PROCESSES:

There are about 35 different welding and brazing process and several soldering methods, in use by

the industry today. There are various ways of classifying the welding for example, they may be

classified on the basis of source of heat (flames, arc etc.)

In general various welding processes are classified as follows.

1: Gas Welding

(a): Air Acetylene (b): Oxy Acetylene (c): Oxy Hydrogen Welding 2: ARC WELDING

(a): Carbon Arc welding (b); Plasma Arc welding (c): Shield Metal Arc Welding (d): T.I.G. (Tungsten Inert Gas Welding) (e): M.I.G. (Metal Inert Gas Welding) 3: RESISTANCE WELDING

(a): Spot welding (b): Seam welding (c): Projection welding (d): Resistance Butt welding (e): Flash Butt welding 4: SOLID STATE WELDING (a): Cold welding (b): Diffusion welding (c): Forge welding (d): Fabrication welding (e): Hot pressure welding (f): Roll welding 5: THERMO CHEMICAL WELDING (a): Thermit welding (b): Atomic welding

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6: RADIANT ENERGY WELDING (a): Electric Beam Welding (b): Laser Beam Welding

DIFFERENT WELDING JOINTS AND POSITIONS OF WELDING Different types of welding joints are classified as Butt, Lap, Corner, Tee and edge joints which are shown in figure

GAS WELDING INTRODUCTION

Oxy-fuel gas welding is a general term used to describe any welding process that uses a fuel gas

combined with oxygen to produce a flame. It is a fusion welding process. The most commonly used

fuel is acetylene gas. The heat source is the flame obtained by combustion of oxygen and acetylene.

When mixed together in correct proportions within a hand-held torch or blowpipe, a relatively hot

flame is produced with a temperature of about 3,300oC (6,000oF). The chemical action of the

oxyacetylene flame can be adjusted by changing the ratio of the volume of oxygen to acetylene.

Chemical reactions are as follows: -Stage1 Acetylene + Oxygen = Carbon Monoxide + Hydrogen C2H2 +

O2= 2CO + H2 Approximately one-third of the total welding heat is generated in Stage 1 Stage 2 Carbon Monoxide + Hydrogen + Oxygen = Carbon Dioxide + Water CO + H2 + O2

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= CO2 + H2O The remaining two-third of the heat is generated in Stage 2. The reaction of hydrogen with oxygen

produces water vapor.

Figure 1: Oxy Acetylene Welding

TYPES OF FLAMES: The chemical action of the oxyacetylene flame can be adjusted by changing the ratio of the volume

of oxygen to acetylene.

NEUTRAL FLAME As the supply of oxygen to the blowpipe is further increased, the flame contracts and the white cone

become clearly defined, assuming a definite rounded shape. At this stage approximately equal

quantities of acetylene and oxygen are being used and combustion is complete, all the carbon

supplied by the acetylene is being consumed and the maximum heat given out. The flame is now

neutral, and this type of flame is the one most extensively used by the welder, who should make

himself thoroughly familiar with its appearance and characteristics. The maximum temperature is

at the end of the inner cone.

OXIDIZING FLAME A further increase in the oxygen supply will produce an oxidizing flame in which there is more

oxygen than is required for complete combustion. The inner cone will become shorter and sharper,

the flame will turn a deeper purple color and emit a characteristic slight "hiss", while the molten

metal will be less fluid and tranquil during welding and excessive sparking will occur. An oxidizing

flame is only used for special applications, and should never be used for welding.

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REDUCING OR CARBURIZING FLAME: This is a flame in which an excess of acetylene is burning, i.e. combustion is incomplete and

unconsumed carbon is present. When lighting the blowpipe the acetylene is turned on first and

ignited, giving a very smoky yellow flame of abnormal size, showing two cones of flame in addition

to an outer envelope; this is an exaggerated form of the carburizing flame, but gives out

comparatively little heat and is of little use for welding. When the oxygen is turned on and the

supply is gradually increased, the flame, though still of abnormal size contracts towards the

blowpipe tip where an inner white cone of great luminosity commences to make its appearance. If

the increase in the supply of oxygen is stopped before the cone becomes clearly defined and while it

is still an inch or so long, the result is a carburizing flame which is mainly used for hard surfacing

and should not be employed for welding steel as unconsumed carbon may be introduced into the

weld and produce a hard, brittle, deposit. The temperature of a carburizing flame is lower, so it is

suitable for application requiring low heat, such as brazing, soldering etc.

GAS CUTTING

For cutting, the setup is a little different. A cutting torch has a 60- or 90-degree angled head with orifices placed around a central jet. The outer jets are for preheat flames of oxygen and acetylene. The central jet carries only oxygen for cutting. The use of several preheating flames rather than a single flame makes it possible to change the direction of the cut as desired without changing the position of the nozzle or the angle which the torch makes with the direction of the cut, as well as giving a better preheat balance. Manufacturers have developed custom tips for Mapp, propane, and polypropylene gases to optimize the flames from these alternate fuel gases.

The torch's trigger blows extra oxygen at higher pressures down the torch's third tube out of the central jet into the workpiece, causing the metal to burn and blowing the resulting molten oxide through to the other side. The ideal kerf is a narrow gap with a sharp edge on either side of the workpiece; overheating the workpiece and thus melting through it causes a rounded edge.

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Oxygen Rich Butane Torch Flame Fuel Rich Butane Torch Flame

Cutting is initiated by heating the edge or leading face (as in cutting shapes such as round rod) of the steel to the ignition temperature (approximately bright cherry red heat) using the pre-heat jets only, then using the separate cutting oxygen valve to release the oxygen from the central jet. The oxygen chemically combines with the iron in the ferrous material to oxidize the iron quickly into molten iron oxide, producing the cut.

Oxy-propane torches are usually used for cutting up scrap to save money, as LPG is far cheaper joulefor joule than acetylene, although propane does not produce acetylene's very neat cut profile. Propane also finds a place in production, for cutting very large sections.

Flame cutting is a combustion process. It is not the heating flame itself that does the actual

cutting but an oxygen jet, which burns the material during heat formation and transports the

combustion products (slag) away from the cut. When cutting, the purity of the oxygen is of huge

importance to the cutting speed. The purer the gas, the higher the cutting speed and the better the

productivity and cut quality.

Before cutting can begin, the steel must be heated to ignition temperature by means of a gas

flame. The choice of fuel gas affects cut quality and the time used for preheating. When choosing

a fuel gas, the thickness of the material must also be considered. The most important part of

cutting equipment is the cutting nozzle. The higher the outlet speed of the oxygen jet, the better

the output of the nozzle. In turn, the speed depends on the shape of the cutting nozzle.

Nowadays, nozzles with an expansion channel are often used, giving the oxygen jet a high

velocity.

The construction of the cutting nozzle and its adjustment to various fuel gases with regard to the

size of the gas channels, exact geometry, tolerances and surface finish are of crucial importance

to achieving a high quality cut. The cutting speed can be increased by using a curtain nozzle, for

example. This type of nozzle has a special oxygen channel which protects the cutting oxygen jet

from impurities, making higher cutting speeds possible.

Oxyfuel cutting can be used for cutting mild and low-alloyed steel, up to thicknesses of just over

1,000 mm. The cut quality also depends on the surface of the work piece, and can be affected by

different types of shop primer. Use of several burners for straight cutting, phase cutting and joint

preparation is an example of the cutting process’s versatility.

The use of fuel gases together with oxygen can give rise to dangerous situations, if the user lacks

adequate knowledge of how gases, equipment and the necessary protective equipment must be

used.

EXERSISE

Q.1 Explain oxy acetylene gas welding with help neat sketch.

Q.2 Explain Types of flames for gas welding.

Q.3 Difference between gas and arc welding.

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EXPERIMENT-8

AIM: - TO STUDY DIFFERENT TYPES OF ARC WELDING. INTRODUCTION

Arc welding is a liquid state welding process in which electrical energy produced by an arc between

an electrode and a work piece is converted into heat and used for fusion welding.

1. Heat Source: An electric arc is generated between a coated metallic electrode and the metal

work piece. The heat produced by this arc melts the metal, which then mixes with the molten

deposits of the electrode.

2. Filler rod: The electrodes have thin long stick like shape; so, arc welding is also known as “stick

welding”. The electrode carries the current to form the arc and provides filler metal to control the

shape of the bead.

3. Shielding: Combustion of the coating on the electrode (sometimes called flux) produces a gas,

which shields the arc from impurities in the atmosphere. As the molten metal is deposited, a slag

forms over the bead, which serves as a protective coating from contaminants in the air as the weld

cools and solidifies Figure 1.Arc welding is used for joining ferrous metals (steels), such as: Farm

implements and machinery, building construction, automobile construction, etc.

ARC WELDING

In this process a joint is established by fusing the material near the region of joint by means

of an electric arc struck between the material to be joined and an electrode. A high current

low voltage electric power supply generates an arc of intense heat reaching a temperature

of approximately 3800°C. The electrode held externally may act as a filler rod or it is fed

independently of the electrode. Due to higher levels of heat input, joints in thicker

materials can be obtained by the arc welding process. It is extensively used in a variety of

structural applications.

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CARBON ARC WELDING

Schematic Illustration of Carbon Arc Welding

Carbon Arc Welding (CAW) is a welding process, in which heat is generated by an electric arc struck

between an carbon electrode and the work piece. The arc heats and melts the work pieces edges,

forming a joint.Carbon arc welding are the oldest welding process.If required, filler rod may be used

in Carbon Arc Welding. End of the rod is held in the arc zone. The molten rod material is supplied to

the weld pool. Shields (neutral gas, flux) may be used for weld pool protection depending on type of

welded metal.

ADVANTAGES OF CARBON ARC WELDING:

Low cost of equipment and welding operation; High level of operator skill is not required; The process is easily automated; Low distortion of work piece.

DISADVANTAGES OF CARBON ARC WELDING

Unstable quality of the weld (porosity);

Carbon of electrode contaminates weld material with carbides. Carbon Arc Welding has been replaced by Tungsten Inert Gas Arc Welding (TIG, GTAW) in many applications.

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SHIELDED METAL ARC WELDING (SMAW) Shielded metal arc welding (Stick welding, manual metal arc welding) uses a metallic consumable electrode of a proper composition for generating arc between itself and the parent work piece. The molten electrode metal fills the weld gap and joins the work pieces. This is the most popular welding process capable to produce a great variety of welds. The electrodes are coated with a shielding flux of a suitable composition. The flux melts together with the electrode metallic core, forming a gas and a slag, shielding the arc and the weld pool. The flux cleans the metal surface, supplies some alloying elements to the weld, protects the molten metal from oxidation and stabilizes the arc.

ADVANTAGES OF SHIELDED METAL ARC WELDING (SMAW)

Simple, portable and inexpensive equipment; Wide variety of metals, welding positions and electrodes are applicable; Suitable for outdoor applications.

DISADVANTAGES OF SHIELDED METAL ARC WELDING (SMAW)

The process is discontinuous due to limited length of the electrodes; Weld may contain slag inclusions; Fumes make difficult the process control.

SUBMERGED ARC WELDING (SAW)

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Submerged Arc Welding is a welding process, which utilizes a bare consumable metallic electrode

producing an arc between itself and the work piece within a granular shielding flux applied around

the weld. The arc heats and melts both the work pieces edges and the electrode wire. The molten

electrode material is supplied to the surfaces of the welded pieces, fills the weld pool and joins the

work pieces. Since the electrode is submerged into the flux, the arc is invisible. The flux is partially

melts and forms a slag protecting the weld pool from oxidation and other atmospheric

contaminations.

Schematic Illustration of Submerged Arc Welding ADVANTAGES OF SUBMERGED ARC WELDING (SAW):

Very high welding rate; The process is suitable for automation; High quality welds structure.

Disadvantages of Submerged Arc Welding (SAW):

Weld may contain slag inclusions; Limited applications of the process - mostly for welding horizontally located plates.

METAL INERT GAS WELDING (MIG, GMAW)

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Metal Inert Gas Welding (Gas Metal Arc Welding) is a arc welding process, in which the weld is

shielded by an external gas (Argon, helium, CO2, argon + Oxygen or other gas mixtures).

Consumable electrode wire, having chemical composition similar to that of the parent material, is

continuously fed from a spool to the arc zone. The arc heats and melts both the work pieces edges

and the electrode wire. The fused electrode material is supplied to the surfaces of the work pieces,

fills the weld pool and forms joint. Due to automatic feeding of the filling wire (electrode) the

process is referred to as a semi-automatic.

Schematic Illustration of Metal Inert Gas Welding

ADVANTAGES OF METAL INERT GAS WELDING (MIG, GMAW) Continuous weld may be produced (no interruptions); High level of operators skill is not required; Slag removal is not required (no slag);

Disadvantages of Metal Inert Gas Welding (MIG, GMAW)

Expensive and non-portable equipment is required; Outdoor application is limited because of effect of wind, dispersing the shielding gas.

TUNGSTEN INERT GAS ARC WELDING (TIG, GTAW)

Tungsten Inert Gas Arc Welding (Gas Tungsten Arc Welding) is a welding process, in which heat is

generated by an electric arc struck between a tungsten non-consumable electrode and the work

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piece. The weld pool is shielded by an inert gas (Argon, helium, Nitrogen) protecting the molten

metal from atmospheric contamination. The heat produced by the arc melts the work pieces edges

and joins them. Filler rod may be used, if required. Tungsten Inert Gas Arc Welding produces a high

quality weld of most of metals. Flux is not used in the process.

Schematic Illustration of Tungsten Inert Gas Welding

Advantages of Tungsten Inert Gas Arc Welding (TIG, GTAW) Weld composition is close to that of the parent metal; High quality weld structure Slag removal is not required (no slag); Thermal distortions of W/P are minimal due to concentration of heat in small zone.

Disadvantages of Tungsten Inert Gas Arc Welding (TIG, GTAW)

Low welding rate; Relatively expensive; Requires high level of operator’s skill.

ELECTROSLAG WELDING (ESW)

Electroslag Welding is a welding process, in which the heat is generated by an electric current

passing between the consumable electrode (filler metal) and the work piece through a molten slag

covering the weld surface. Prior to welding the gap between the two work pieces is filled with a

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welding flux. Electroslag Welding is initiated by an arc between the electrode and the work piece

(or starting plate). Heat, generated by the arc, melts the fluxing powder and forms molten slag. The

slag, having low electric conductivity, is maintained in liquid state due to heat produced by the

electric current. The slag reaches a temperature of about 3500°F (1930°C). This temperature is

sufficient for melting the consumable electrode and work piece edges. Metal droplets fall to the

weld pool and join the work pieces. Electroslag Welding is used mainly for steels.

Schematic Illustration of Tungsten Inert Gas Welding

Advantages of Electroslag Welding High deposition rate - up to 45 lbs/h (20 kg/h); Low slag consumption (about 5% of the deposited metal weight); Low distortion; Unlimited thickness of work piece.

Disadvantages of Electroslag welding Coarse grain structure of the weld; Low toughness of the weld; Only vertical position is possible

PLASMA ARC WELDING (PAW)

Plasma Arc Welding is the welding process utilizing heat generated by a constricted arc struck

between a tungsten non-consumable electrode and either the work piece (transferred arc process)

or water cooled constricting nozzle (non-transferred arc process).Plasma is a gaseous mixture of

positive ions, electrons and neutral gas molecules. Transferred arc process produces plasma jet of

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high energy density and may be used for high speed welding and cutting of Ceramics, steels,

Aluminum alloys, Copper alloys, Titanium alloys, Nickel alloys. Non-transferred arc process

produces plasma of relatively low energy density. It is used for welding of various metals and for

plasma spraying (coating). Since the work piece in non-transferred plasma arc welding is not a part

of electric circuit, the plasma arc torch may move from one work piece to other without

extinguishing the arc.

Schematic Illustration of Tungsten Inert Gas Welding

ADVANTAGES OF PLASMA ARC WELDING (PAW) Requires less operator skill due to good tolerance of arc to misalignments; High welding rate; High penetrating capability (keyhole effect)

DISADVANTAGES OF PLASMA ARC WELDING (PAW)

Expensive equipment; High distortions and wide welds as a result of high heat input (in transferred arc process).

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RESISTANCE WELDING (RW) RW is a group of welding processes that produces coalescence of the faying surfaces with the heat obtained from the resistance of the work pieces to the flow of the welding current in a circuit of which the work pieces are a part, and by the application of pressure. Faying surfaces: The surfaces of materials in contact with each other and join about to be joined together.

PRINCIPLES OF OPERATION The RW processes differ from arc welding in that pressures used but filler metal of fluxes are not. Four factors are involved in making a resistance weld:

1) The amount of current that passes through the work. 2) The pressure that the electrodes transfer to the work 3) The time the current flows through the work 4) The area of the electrode tip in contact with the work.

SPOT WELDING It is a RW process, in which two or more overlapped metal sheets are joined. The method uses pointed copper electrodes providing passage of electric current .The electrodes also transmit pressure required for formation of strong weld

Spot welding machines

Single point welding machine (rocker arm type and press type) Multiple point welding machine

Electrodes Electrode materials in general use are copper alloys developed to combine high conductivity and hardness, plus reasonable resistance to softening at the working temperature of the tip.

Electrode cooling

Electrode life is critically dependent on water cooling. All electrodes have an internal cooling passage.

Cooling of the tip face during the weld time depends on the shape and size of the electrode itself.

Water cooling prevents progressive build-up of heat in the electrode.

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Spot welding: Principles of operation

The spot welding process involves a series of precisely controlled events. This sequence

normally consists of five time-periods, which are set on the spot welding timer/controller Squeeze time: time set to ensure predetermined welding force is achieved before current flow; some timers are also equipped with a pre-squeeze time setting

Weld time: time for which welding current is switched on Hold time(forge): time electrodes are held together under pressure after weld time Cool time: current off time between successive current pulses in pulsation or seam welding Off time: time used for repeat welding such as stitch welding; time between end of hold

time on one weld and start of squeeze time on the next, during which electrodes are re-positioned.

The following metals may be welded by RW Low carbon steels-the widest application of RW Aluminum alloys, Inconel, Nickel, Magnesium and Titanium Medium carbon steels, high carbon steels and Alloy steels(may be welded, but the

weld is brittle)

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ADVANTAGES OF RW

High welding rates; Low fumes; Cost effectiveness; Easy automation; No filler materials are required; Low distortions.

DISADVANTAGES OF RW

High equipment cost; Low strength of discontinuous welds; Thickness of welded sheets is limited -up to 6 mm.

EXERSISE

Q.1 Explain different types of Arc welding .

Q.2 Explain Plasma arc welding with help of neat sketch.

Q.3 Write a short note on electro slag welding.

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EXPERIMENT-9

AIM - TO UNDERSTAND THE BASICS OF RESISTANCE WELDING INTRODUCTION

Resistance Welding is a welding process, in which work pieces are welded due to a combination of a pressure applied to them and a localized heat generated by a high electric current flowing through the contact area of the weld.Heat produced by the current is sufficient for local melting of the work piece at the contact point and formation of small weld pool (”nugget”). The molten metal is then solidifies under a pressure and joins the pieces. Time of the process and values of the pressure and flowing current, required for formation of reliable joint, are determined by dimensions of the electrodes and the work piece metal type.AC electric current (up to 100 000 A) is supplied through copper electrodes connected to the secondary coil of a welding transformer.

THE FOLLOWING METALS MAY BE WELDED BY RESISTANCE WELDING

Low carbon steels - the widest application of Resistance Welding Aluminum alloys Medium carbon steels, high carbon steels and Alloy steels (may be welded, but the weld is

brittle)

ADVANTAGES OF RESISTANCE WELDING

High welding rates; Low fumes; Cost effectiveness; Easy automation; No filler materials are required; Low distortions.

DISADVANTAGES OF RESISTANCE WELDING

High equipment cost; Low strength of discontinuous welds; Thickness of welded sheets is limited - up to 1/4” (6 mm);

Resistance Welding (RW) is used for joining vehicle body parts, fuel tanks, domestic radiators, pipes of gas oil and water pipelines, wire ends, turbine blades, railway tracks. The most popular methods of Resistance Welding are:

Spot Welding (RSW) Flash Welding (FW) Resistance Butt Welding (UW) Seam Welding (RSEW)

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SPOT WELDING (RSW)

Spot Welding is a Resistance Welding (RW) process, in which two or more overlapped metal sheets are joined by spot welds.The method uses pointed copper electrodes providing passage of electric current. The electrodes also transmitt pressure required for formation of strong weld.Diameter of the weld spot is in the range 1/8” - 1/2” (3 - 12 mm).Spot welding is widely used in automotive industry for joining vehicle body parts.

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FLASH WELDING (FW)

Flash Welding is a Resistance Welding (RW) process, in which ends of rods (tubes, sheets) are heated and fused by an arc struck between them and then forged (brought into a contact under a pressure) producing a weld.The welded parts are held in electrode clamps, one of which is stationary and the second is movable.

Flash Welding method permits fast (about 1 min.) joining of large and complex parts. Welded part are often annealed for improvement of Toughness of the weld. Steels, Aluminum alloys, Copper alloys, Magnesium alloys, Copper alloys and Nickel alloys may be welded by Flash Welding. Thick pipes, ends of band saws, frames, Aircraft landing gears are produced by Flash Welding.

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RESISTANCE BUTT WELDING (UW)

Resistance Butt Welding is a Resistance Welding (RW) process, in which ends of wires or rods are held under a pressure and heated by an electric current passing through the contact area and producing a weld.

The process is similar to Flash Welding, however in Butt Welding pressure and electric current are applied simultaneously in contrast to Flash Welding where electric current is followed by forging pressure application. Butt welding is used for welding small parts. The process is highly productive and clean. In contrast to Flash Welding, Butt Welding provides joining with no loss of the welded materials.

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SEAM WELDING (RSEW)

Seam Welding is a Resistance Welding (RW) process of continuous joining of overlapping sheets by passing them between two rotating electrode wheels. Heat generated by the electric current flowing through the contact area and pressure provided by the wheels are sufficient to produce a leak-tight weld.

Seam Welding is high speed and clean process, which is used when continuous tight weld is required (fuel tanks, drums, domestic radiators).

EXERSISE

Q.1 Explain different types Resistance welding.

Q.2 write a short note on seam welding machine.

Q.3 Difference between butt and flash welding.

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EXPERIMENT-10

AIM - TO UNDERSTAND THE PRINCIPLE OF ROILING PRODUCTS WITH ITS METHOD AND

FUNDAMENTAL OF ROLL PASSES. INTRODUCTION Metal rolling is one of the most important manufacturing processes in the modern world. The large

majority of all metal products produced today are subject to metal rolling at one point in their

manufacture. Metal rolling is often the first step in creating raw metal forms. The ingot or

continuous casting is hot rolled into a bloom or a slab, these are the basic structures for the creation

of a wide range of manufactured forms. Blooms typically have a square cross section of greater than

6x6 inches. Slabs are rectangular and are usually greater than 10 inches in width and more than 1.5

inches in thickness. Rolling is most often, (particularly in the case of the conversion of an ingot or

continuous casting), performed hot.

PRINCIPAL OF ROLLING PROCESS

Most metal rolling operations are similar in that the work material is plastically deformed by

compressive forces between two constantly spinning rolls. These forces act to reduce the thickness

of the metal and affect its grain structure. The reduction in thickness can be measured by the

difference in thickness before and after the reduction, this value is called the draft. In addition to

reducing the thickness of the work, the rolls also act to feed the material as they spin in opposite

directions to each other. Friction is therefore a necessary part of the rolling operation, but too much

friction can be detrimental for a variety of reasons. It is essential that in a metal rolling process the

level of friction between the rolls and work material is controlled, lubricants can help with this

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The production of quality welds requires (1) a satisfactory heat and/or pressure source, (2) a

means of protecting or cleaning the metal, and (3) caution to avoid, or compensate for, harmful

metallurgical effects.

GRAIN STRUCTURE IN METAL ROLLING

In common industrial manufacturing industry, the ingot or continuous casting is hot rolled into a

bloom or slab. In addition to producing a useful shape for further processing, the hot rolling process

converts the cast grain structure into a wrought grain structure. The initial cast material will

possess a non-uniform grain structure, typically large columnar grains that grow in the direction of

solidification. These structures are usually brittle with weak grain boundaries. Cast structure

characteristically contains many defects such as porosity caused by gases, shrinkage cavities, and

solid inclusions of foreign material that becomes trapped in the metal, such as metallic oxides.

Rolling a metal above its recrystallization temperature breaks apart the old grain structure and

reforms a new one. Grain boundaries are destroyed and new tougher ones are formed, along with a

more uniform grain structure. Metal rolling pushes material, closing up vacancies and cavities

within the metal. In addition, hot rolling breaks up inclusions and distributes their material

throughout the work.

DEFECTS IN METAL ROLLING

A wide variety of defects are possible in metal rolling manufacture. Surface defects commonly occur

due to impurities in the material, scale, rust, or dirt. Adequate surface preparation prior to the

metal rolling operation can help avoid these. Most serious internal defects are caused by improper

material distribution in the final product. Defects such as edge cracks, center cracks, and wavy

edges, are all common with this method of metal manufacturing.

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Often times a sheet is not defective, it is just not flat enough. In sheet metal industrial practice, a

sheet may be passed through a series of leveling rolls that flex the sheet in opposite directions to

flatten it. Another interesting defect that can occur in flat rolling is alligatoring, where the work

being rolled actually splits in two during the process. The two parts of the work material travel in

opposite directions relative to their respective rolls.

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In shape rolling manufacture, a work piece will often experience different amounts of reduction

in different areas of its cross section. One of the goals of roll pass design is to properly design a

series of reductions in such a way as to mitigate the relative differences in shape change between

areas, in order to avoid material defects. Improper reductions of the product can cause warping

or cracking of the material. Metal rolling practice is not always the cause of warping or cracking,

sometimes defects in the metal being rolled may be the reason.

Figure:1

ROLLING MILLS

In metal forming industry, rolls themselves do not function in isolation. In a metal rolling process,

rolls, stands, bearings, housing, motors, and other mechanical equipment are all a necessary part of

the manufacturing operation. The place where all the equipment for metal rolling manufacture is

set up is called a rolling mill. Rolling mills often vary in the type, number, and position of rolls.

Rolling mill arrangements commonly used in manufacturing industry today include the two high

mill, the two high reversing mill, the three high mill, the four high mill, the cluster mill, and the

tandem rolling mill.

The three high rolling mill utilizes the principle of passing the work back and forth to achieve a

series of reductions. Unlike the two high reversing mill, the three high mill has three rolls that

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always spin in the same direction. An elevator mechanism lifts and lowers the work so that it can be

passed back and forth through the rolls.

It is known, in metal rolling practice, that the amount of roll force is reduced with a smaller radius

of the rolls. Smaller radius rolls, however, deflect easier and must be supported by other rolls. The

four high mill uses this principle with two smaller work rolls each supported by a larger backing

roll.

The cluster mill, or Sendzimir mill, uses a small work roll backed up by many other rolls. This

extremely rigid setup is often used for cold rolling high strength material to a very thin width.

The tandem rolling mill consists of several stands that the work material constantly passes through.

At each stand the thickness of the work strip is reduced a certain amount. The total reduction

between the first and last stand can be significant. There are technical problems associated with

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tandem rolling, caused particularly by the fact that the speed of the work material increases as it

passes through each stand. In manufacturing practice, various control systems are used to keep the

entire operation synchronized. Once the particular technical problems and initial setup investment

is overcome, tandem rolling can provide a great advantage in the cost and productivity of an

industrial metal rolling process. Tandem rolling can be even more advantageous when integrated

with continuous casting.

EXERSISE

Q.1 Explain different types rolling mill with help of neat sketch.

Q.2 Explain tandem rolling mill.

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EXPERIMENT-11

AIM- STUDY OF BASIC FORGING OPERATIONS AND DEFECTS IN FORGING. INTRODUCTION Metal forging is a metal forming process that involves applying compressive forces to a work

piece to deform it, and create a desired geometric change to the material. The forging process

is very important in industrial metal manufacture, particularly in the extensive iron and steel

manufacturing industry. A steel forge is often a source of great output and productivity. Work

stock is input to the forge, it may be rolled, and it may also come directly from cast ingots or

continuous castings. The forge will then manufacture steel forgings of desired geometry and

specific material properties. These material properties are often greatly improved.

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FORGING OPERATIONS

1. DRAWING This is the operation in which metal gets elongated with a reduction in the cross sedation area.

For this, a force is to be applied in a direction perpendicular to the length axis

2. UP SETTING This is applied to increase the cross seat ional area of the stock at the expanse of the length. To

achieve the length of upsetting force is applied in a direction parallel to the length axis, For

example forming of a bolt head.

3. FULLERING: It a similar to material cross-section is decreased and length increased. To do this; the bottom

fuller is kept in angle hole with the heated stock over the fuller .the top fuller is then kept

above the stock and then with the sledge hammer, and the force is applied on the top fuller.

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4. EDGING It is a process in which the metal piece is displaced to the desired shape by striking between

two dies edging is frequently as primary drop forging operation.

5.BENDING Bending is very common forging operation. It is an operation to give a turn to metal rod or

plate. This is required for those which have bends shapes.

6. PUNCHING It is a process of producing holes in motel plate is placed over the hollow cylindrical die. By

pressing the punch over the plate the hole is made.

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7.FORGEWELDING

It It is a process of joining two metal pieces to increase the length. By the pressing or

hammering then when they are at forging temperature. It is performed in forging shop and

hence is called forged welding.

8. CUTTING

It is a process in which a metal rod or plate cut out into two pieces, with the help of chisel and

hammer, when the metal is in red hot condition.

9. FLATING AND SETTING DOWN Fullering leaves a corrugated surface on the job. Even after a job is forged into shape with a

hammer, the marks of the hammer remains on the upper surface of the job. To remove

hammer marks and corrugation and in order to obtain a smooth surface on the job, a flatter or

set hammer is used.

10.SWAGING Swaging is done to reduce and finish work for desire size and shape, usually either round or

hexagonal. For small jobs top and bottom swage pair is employed, where as for large work

swage block can be used.

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FORGING DEFECTS:

(A): Unfilled Section:

In this some section of the die cavity are not completely filled by the flowing metal. The causes

of these defects are improper design of the forging die or using forging techniques.

(B): Cold Shut:

This appears as a small cracks at the corners of the forging. This is caused manely by the

improper design of die. Where in the corner and the fillet radie are small as a result of which

metal does not flow properly into the corner and the ends up as a cold shut.

(C): Scale Pits:

This is seen as irregular depurations on the surface of the forging. This is primarily caused

because of improper cleaning of the stock used for forging. The oxide and scale gets embedded

into the finish forging surface. When the forging is cleaned by pickling, these are seen as

depurations on the forging surface.

(D): Die Shift:

This is caused by the miss alignment of the die halve, making the two halve of the forging to be

improper shape.

(E): Flakes:

These are basically internal ruptures caused by the improper cooling of the large forging. Rapid

cooling causes the exterior to cool quickly causing internal fractures. This can be remedied by

following proper cooling practices.

(F): Improper Grain Flow:

This is caused by the improper design of the die, which makes the flow of the metal not flowing

the final interred direction.

EXERSISE

Q.1 Explain types of forging operations.

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EXPERIMENT-12

AIM: TO STUDY THE BASIC CONCEPT OF EXTRUSION PROCESSES.

Introduction

Metal extrusion is a metal forming process in which a work piece, of a certain length and

cross section, is forced to flow through a die of a smaller cross sectional area, thus forming

the work to the new cross section. The length of the extruded part will vary, dependant

upon the amount of material in the work piece and the profile extruded. Numerous cross

sections are manufactured by this method. The cross section produced will be uniform over

the entire length of the metal extrusion. Starting work is usually a round billet, which may

be formed into a round part of smaller diameter, a hollow tube, or some other profile. The

basic principle of metal extrusion is illustrated in figure.

In this case, a round billet is forced through a die opening creating a round part of reduced

diameter. The ram will continue to move forward, pushing more of the billet material

through the die opening. As this occurs, a continuous length of work will emerge from the

other side of the mold at a certain velocity relative to the speed of the ram. When

manufacturing an extruded product, considerations to support and guide the length of

material as it exits the die are important. As the ram reaches the end of its stroke, a small

portion of the billet stock can not be pushed through the die opening. This last part of the

work metal is called the butt end. The product is cut at the die opening to remove it from

the butt end material. In manufacturing industry, methods have been developed to extrude

a wide variety of different materials. Some materials are better suited for extrusion

manufacture than others. Aluminum is an extremely good material for metal extrusion.

Copper, magnesium, zinc, tin and some softer low carbon steels, can also be extruded with

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little complication due to the material. High carbon steels, titanium and various refractory

alloys, can be difficult to extrude.

COLD EXTRUSION OR HOT EXTRUSION

Metal extrusion is a forming process, like other metal forming processes, it can be

performed either hot or cold. The characteristics of hot forming and cold forming were

discussed in detail in the fundamentals of metal forming section.

Hot forming, or hot working, involves working a metal above its recrystallization

temperature. Hot working has many advantages in the improvement of the mechanical

properties of the part's material. Cast metal contains pores and vacancies throughout the

material. Hot working will push and redistribute material, closing up these vacancies.

Impurities in molten metal usually combine together in masses upon hardening, forming

solid inclusions within the metal. These inclusions cause weakness in the surrounding

material. Hot working causes these inclusions to break up and distributes them throughout

the mass of metal. Large, irregular, columnar grain structures are usually present in cast

parts. Hot working a metal will break up irregular structures and recrystallize the mass of

material into a finer wrought grain structure. Mechanical properties of the part, such as

impact resistance, ductility and strength characteristics, are improved. If a hot extrusion is

performed on a cast work piece, then the advantages of hot working will be imparted to the

work. However, most metal extrusions in manufacturing industry are performed on billets

that have already been hot formed, thus the mechanical advantages of hot forming have

already been imparted to the material.

DIRECT EXTRUSION COMPARED WITH INDIRECT EXTRUSION

Metal extrusion processes, in manufacturing industry, can be classified into two main

categories, direct and indirect. Hollow extrusions, as well as cross sections, can be

manufactured by both methods. Each method, however, differs in its application of force

and is subject to different operational factors.

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METAL FLOW DURING EXTRUSION

During a metal extrusion process, metal from a work piece of a certain cross section is

forced to flow through a die of smaller cross section, forming an extruded part. It is

important to understand the flow of material that occurs as the part is being formed. In

some ways it is similar to fluid flowing from one channel into another channel of

decreasing width. The metal is deformed and forced to flow together as it progresses

towards, and through, the die. As the work travels through the die, the outer layers are

deformed more than the ones closer to the middle. The outer sections, further from the

central axis, will experience greater material displacement and will have more turbulent

metal flow characteristics. The material closer to the center will move faster through the

mold, meaning it will have the higher velocity relative to the die.

DIRECT EXTRUSION

Direct extrusion is a similar metal extrusion process to the one illustrated in figure 208. In

direct, or forward extrusion, the work billet is contained in a chamber. The ram exerts force

on one side of the work piece, while the forming die, through which the material is

extruded, is located on the opposite side of the chamber. The length of extruded metal

product flows in the same direction that the force is applied.

INDIRECT EXTRUSION

Indirect extrusion is a particular type of metal extrusion process in which the work piece is

located in a chamber that is completely closed off at one side. The metal extrusion die are

located on the ram, which exerts force from the open end of the chamber. As the

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manufacturing process proceeds, the extruded product flows in the opposite direction that

the ram is moving. For this purpose the ram is made hollow, so that the extruded section

travels through the ram itself. This manufacturing process is advantageous in that there are

no frictional forces between the work piece and the chamber walls. Indirect extrusion does

present limitations.

EXERSISE

Q.1 Explain different types extrusion processes with help of neat sketch.

Q.2 Difference between direct and indirect extrusion.

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EXPERIMENT-13

AIM:-TO UNDERSTAND THE PLASTICS PART MANUFACTURING PROCESSES.

INTRODUCTION

Plastics are one of the numerous polymeric materials & have extremely large molecules or

long chain molecules with very high molecular weight. The word plastic is derived from the

greek word plastikos, which means ‘able to be molded & shaped’.

The word plastics are often used as a synonym of polymers. In fact, plastics are one of the

numerous polymeric materials & have extremely large molecules. Polymer contains

molecules of same substances joined together end to end to form a chain or bigger

molecule & the process of forming long chains of molecules is called polymerization.

(a) Natural polymers: these are prepared from natural organic materials, from animal &

vegetable products. There are some natural polymers which are available as such and are

called natural polymers for example cellulose, resins, lac, casein, shellac, proteins etc.

(b) Synthetic organic polymer: The polymers (plastics) which do not occur in nature and

are prepared artificially are called synthetic plastics or polymers. These are prepared from

coal & petroleum products,

Advantages

• Low density & light weight • High strength to weight ratio, particularly possessed by the reinforced plastics • Resistance to corrosion due to moisture & most chemicals • Noise reduction in working • Inexpensiveness in fabrication compared to other metals on volume basis • Availability with different unique shapes & properties • Low cost • Wide choice of colors, transparencies & surface finish

Disadvantages

• Low operating temperature • Low strength in compression to metals • High thermal expansion & flammability

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CLASSIFICATION OF PLASTICS

1) Thermoplastics Thermoplastic can be soften again & again by heating, remold again and again and in doing

so, they do not undergo any chemical change. On cooling they become hard & hence are

also known as cold-setting plastics. The thermoplastics can be readily molded or extruded

as they melt to a viscous state. Since the material is easily reused, there is little wastage in

making products from thermoplastics. These plastics are available in many shades & colors

with different degrees of transparency.

Thermosetting plastics

Thermosetting plastics also known as thermosets or heat-setting plastics. A product

formed out of a thermosetting plastic mixture undergoes a non-reversible chemical change

on its curing, as a result of which the cured product acquires a hard & permanent shape

which is substantially infusible & which can’t be molded again by reheating.It is with this

reason that the thermosetting plastic can’t be molded again & again by heating. Once

molded these plastics may distort under load at 120C but they will not become soft or

fusible.

CLASSIFICATION OF PLASTICS:-

THERMOPLASTIC THERMOSETTING

1. Polyethylene (PE) 1. Aminos

2. Polypropylene (PP) 2. Phenolics

3. Polystyrene (PS) 3.Polyurethanes

4. Poly Vinyl Chloride (PVC) 4.Polyesters

5. Polytetrafluoroethylene(PTFE) 5.Epoxides

6. Polycarbonates (PC)

7. Acetal

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PLASTIC MANUFACTURING PROCESSES

1. EXTRUSION MOULDING

2. COMPRESSION MOULDING

3. TRANSFER MOULDING

4. CALENDARING

5. THERMAL FORMING

6. SLUSH MOULDING

7. LAMINATION

8. INJECTION MOULDING

9. BLOW MOULDING

PROPERTIES OF PLASTICS

Low Density

To Make Low Weight With High Strength

Antifriction And Self Lubrication Sometimes Achieved.

Corrosion Resistance, water Proofing And Noiseless Operation Of Moving Parts

Low In Cost

Insulation Of Heat And Electricity

Chemically Stable

Less Brittle

Good Toughness

Easily Molded

Colour Ability

EXERSISE

Q.1 Explain different plastic manufacturing processes.

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EXPERIMENT-14

AIM: TO UNDERSTAND THE FUNDAMENTAL OF PRESS & PRESS TOOL OPRATIONS.

INTRODUCTION:

Press working may be defined as, a manufacturing process by which various components

are made from sheet metal. This process is also termed as cold stamping. The machine used

for press working is called a press.

The main features of a press are:

• A frame which support a ram or a slide and a bed, a source of mechanism for

operating the ram in line with and normal to the bed.

• The ram is equipped with suitable punch/punches and a die block is attached to the

bed.

• A stamping is produced by the downward stroke of the ram when the punch moves

towards and into the die block.

• The punch and die block assembly is generally termed as a “die set” or simple as the

“die”

Press working operations:

The sheet metal operations done a press may be grouped into two categories.

1: Cutting operations

Ø Piercing Ø Blanking Ø Notching

Ø Lancing Ø Parting off Ø Cutoff

Ø Cropping Ø Perforating Ø Nibbling

Ø Lowering Ø Trimming Ø Shaving

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Blanking:- In this Cutting action must be about a complete or enclosed contour. Blank is used part.

Notching:-

This is an operation for removing a piece of scrap from the edge.

Lancing:-

In this operation three side cutting and one side bending operation.

Parting Off:- Cut the material between two components to separate it from parent metal. Cut Off:- In this operation the cutting action must be along a line. Cropping:- This is operation for cutting operation to control the strip movement.

Perforating:

In this operation maximum number of holes are pierced in single stroke.

Nibbling:-

This is operation for cut out the sheet to size with help of punching. Louvering:- In this three side forming and one side cutting operation. Trimming:- This operation for to cut excess material which is left out on the flange of the drawn component. Shaving:- This operation give finish cut to the blanks and pierced holes.

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1. BLNKING 2. NOTCHING 3. LANCING

4. PARTING 5. CUT OFF 6. CROPPING

7. PERFORATING 8. NIBBLING 9. LOWERING

10. TRIMMING 11. SHAVING

DIFFERENT CUTTING OPERATIONS PERFORMED ON THE PRESS

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2. FORMING OPERATIONS:- 1. Bending 5. Hemming

2. Drawing 6. Seaming

3. Embossing 7. Curling

4. Coining 8. Bulging

Bending:-

In this operation bend the sheet at specified angle.

Drawing: - It is process of changing flat, precut metal blank into hollow vessel.

Embossing:- This operation created shallow forming at equal thickness. Coining:- This is operation of making impression and depression on sheet metal. Bulging:- It expands the cups along a narrow band and at the same time reduces the height.

Hemming:- This is operation for join the two sheets. Seaming:- This is the operation of pushing the material inside/outside all around the periphery. Curling:- This is the operation of turn the edge inside.

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1. BENDING 2. DRAWING 3. EMBOSSING

4. COINNING 5. HEMMING 6.SEAMING

7. BULGING 8. CURLING

DIFFERENT FORMING OPERATIONS PERFORMED ON PRESS

EXERSISE

Q.1 Explain operation performed on press.

Q.2 Write Classification of dies.