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UNIT – I LATHE

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INTRODUCTION:

Lathe is the father of all machine tool. It is a basic machine tool probably the most important

one of all, lathe was actually the first machine tool.

Lathe is a particular type of machine tool in which the work is held and rotated against a

suitable cutting tool for the purpose of producing surface of revolution in any material.

LATHE SPECIFICATIONS:

In order to specify a lathe, a number of parameters could be used on the specific

applications. However, the major elements used for specifications should invariably be based on

the components that would be manufactured in the lathe. The sum of lathe specifications is,

L=Distance between centers. A=Swing diameter over bed. B=Swing diameter over carriage. R=Radius. H=Height of center from bed

DISTANCE BETWEEN CENTERS (L):

This would be specifying the maximum length of the job that can be turned in the lathe.

SWING DIAMETER OVER BED (A):

This specifies the maximum diameter of the job that can be turned in the lathe machine

generally restricted to small length jobs.

SWING DIAMETER OVER CARRIAGE (B):

This specifies the maximum diameter of job that can be turned in the lathe machines with the

job across the cross slide.

Manufacturing Technology Lab - I Manual

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Other factors should also be specified to fully describe the lathe machine.

1. Horse power of the motor

2. Feed range

3. Accuracy achieved

4. Cutting speed range

5. Screw cutting capacity

6. Spindle nose diameter

PARTS OF ENGINE LATHE OR CENTER LATHE:

The principal parts of an engine lathe are,

1. Bed,

2. Head stock,

3. Tail stock,

4. Carriage,

4.1. Saddle,

4.2. Cross slide,

4.3. Compound rest,

4.4. Tool post,

4.5. Apron.

5. Feed Mechanism,

6. Thread cutting mechanism.

CARRIERS AND CATCH PLATES:

Carriers and catch plates are used to drive a work piece when it is held between two centers.

Carriers or driving dogs are attached to the end of the work piece by a setscrew, and catch plates are

either screwed or bolted to the nose of the headstock spindle.

CHUCK:

A chuck is one of the most important devices for holding and rotating a piece of work in a lathe.

Work piece of short length, and large diameter or irregular shapes, which cannot be conveniently

mounted between centers, are held quickly and rigidly in a chuck.


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TYPES OF CHUCKS:

1. Four jaw independent chuck

2. Three jaw universal chuck

3. Air or hydraulic operated chuck

4. Magnetic chuck

5. Collet chuck

6. Combination chuck

7. Drill chuck

FACE PLATE:

A faceplate consists of a circular disk bored out and threaded to fit the nose of the lathe spindle. This has the radial, plain and T slots for holding work by bolts and clamps.

ANGLE PLATE:

This is a cast iron plate having two faces machined to make them absolutely at right angles to

each other. Holes and slots are provided on both faces so that it may be clamped on a faceplate and can

hold the work piece on the face by bolts and clamps.

MANDRELS:

A mandrel is a device for holding and rotating a hollow piece of work that has been previously

drilled or bored. The work revolves with the mandrel which is mounted between two centers.

PLAIN MANDREL:

The plain mandrel this type of mandrel is most commonly used in shops and finds wide

application where a large number of identical pieces having standard size holes are required to be

mounted on it.

STEP MANDREL:

A step mandrel having steps of different diameters may be employed to drive different work

pieces having different sizes of holes without replacing the mandrel each time. This type of mandrel is

suitable for turning collars, washers and odd size jobs used in repairing workshops.

COOLER MANDREL:

A cooler mandrel having solid coolers is used for turning work pieces having holes of larger

diameter, usually above 100 mm. This construction reduces weight and fits better than a solid mandrel

of equal size.


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SCREWED MANDREL:

A screwed mandrel is threaded at one end with a collar. Work pieces having internal threads

are screwed on to it against the collar for machining.

CONE MANDREL:

A cone mandrel consists of a solid attached to the one end of the body, and a sliding cone,

which can be adjusted by turning a nut at a threaded end.

GANG MANDREL:

This has a fixed collar at one end and a movable collar at the threaded end, which may be

adjusted, to this position by a nut. The mandrel is used to hole a set of hollow work piece between two

collars by tightening the nut.

EXPANSION MANDREL:

There are different types of expansion mandrels. The mandrel consists of tapered pin, which is

driven into a sleeve that is parallel outside and tapered inside the sleeve has three longitudinal slots,

two of which are cut nearly through, and the third splits it completely.

RESTS:

A rest is a mechanical device which supports a long slender work piece, which is turned

between centers or by a clutch, at some intermediate point to prevent bending of the work piece due

to its own weight and vibrations set up due to the cutting force that acts on it.

STEADY REST:

A steady rest shown in Fig consists of a cast iron base, which may be made to slide on the loath

bed ways and clamped at any desired position where a support is necessary.

FOLLOWER REST:

A follower rest consists of a “C” like casting two adjustable jaws which support the work piece. The rest is bolted to the back end of the carriage and moves with it.

TYPES:

1. Speed lathe

a. Woodworking

b. Centering

c. Polishing

d. Spinning


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2. Engine lathe

a. Belt drive

b .Individual motor drive

c. Gear head lathe

3. Bench lathe

4. Tool room lathe 5. Capstan and turret lathe

a. 6. Special purpose 7. Automatic lathe

b. Wheel lathe

c. T. Lathe

d. Gap. Bed lathe

e. Duplicating lathe

THE ENGINE LATHE OR CENTER LATHE:

The term “engine” lathe is associated with the lathe owing to the fed that early lathe was driven

by steam engines It has all parts.

THE BENCH LATHE:

This is a small lathe usually mounted on bench it has similarly all the parts of an engine lathe or

speed lathe and it only difference is being in the size. This is used for small and precision work.

THE TOOL ROOM LATHE:

A tool room lathe having the features similar to an engine lathe is much more accurately built

and has wide range of spindle speed ranging from a very few to quite high speed unto 2500 rpm. This

lathe is mainly used for precision works on tools, dies, and gauges and in machinery work.

THE CAPSTAN AND TURRET LATHE:

These lathes are developed of the engine lathe and are used for product on work. The

distinguishing features of this type of lathe is that the tailstock of an engine lathe is replaced by a

hexagonal turret on the face of which multiple tools may be fitted and feed into the work in the proper

sequence.

SPECIAL PURPOSE LATHE:

As the name implies they are used for special purpose and the jobs, which cannot be

accommodated or conveniently machined on a standard lathe. The wheel lathe is made for finishing

the journal and turning the traded on the railroad carriage and locomotive wheel. The gab bed lathe in


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which a section of the bed is adjacent to the headstock of the bed is recoverable is used to sluing extra

large diameter piece. The T lathe a new member of the lathe family is intended for machining of rotor

for jet engines.

AUTOMATIC LATHE:

These are high speed heavy duty mass production lathe with complete automatic controls once

the tools are set and the machine started it performs automatically all the operation to finish the job.

TOOLS:

A cutting tool may be used either for cutting a part as with a knife or for remaining the chips

parts are produced by removing the metal mostly in the form of small ships removal in the metal

cutting process may be performed wither by cutting tools having distinct cutting edges or by

abrasively sticks abrasive cloth etc, All cutting tools can be divided into 2 groups

1. Single point cutting tool 2. Multi point cutting tool

SINGLE POINT CUTTING TOOLS:

Single point cutting tool has a sharpened cutting part its point and shaft; the point of the too

bounded by the base. The side flank or major flank or end slank or minor flank or and it base. The side

cutting edges of a tool is form by the interaction of the base and the side flank. The end cutting edge, a

tool into form by the intersection of the base and the flank, the chip and cut from the work piece by the

side cutting edges. The paint a where the end and side cutting edge met is called nose of tool.

LATHE OPERATIONS:

TURNING:

Turning is the further most generally used operation is the lathe. In ties the work held in

spindle is rotated which the tool is fed part the work piece in a direction parallel in the axis of rotation.

The surface generated is the cylindrical shape

FACING:

Facing is the operation of machining the ends of a piece of work to produce flat Surface Square

with the axis. The operation involves feeding the tool parallel to the axis of rotation of the work piece.

TAPER TURNING:

Taper may be turned in a lathe by feeding the tool at an angle to the axis of the work piece.

Which taper is essential that the tool cuttings edge should be accurately on the centre line of the work

piece otherwise correct taper will not be obtained


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i. By a broad nose form tool

ii. By setting over to the tailstock center

iii. By swiveling the compound rest

iv. By a taper turning attachment.

v. By combing longitudinal and cross feed in a lather.

THREAD CUTTING:

Thread cutting is one of the most important operations performed in a lathe. When the job is

reduced between centers or by a chuck. The longitudinal feed should be equal to the pitch of the

thread to be cut per revolution of the work piece.


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� FACING, PLAIN TURNING, AND STEP TURNING

� TAPER TURNING

� V - THREAD CUTTING

� KNURLING

� BORING AND INTERNAL THREAD CUTTING

LATHE EXERCISES

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DRAWING:

105

3230

100

BEFORE MACHINING

ØØ

30Ø

20Ø

80 20

AFTER MACHINING

All Dimensions are in mm


FACING, PLAIN TURNING AND STEP TURNING

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Ex. No: Date:

AIM:

To obtain the required shape and size of the work piece by turning and facing operation.

MATERIALS SUPPLIED:

Cylindrical work piece of diameter 32 mm and length 105 mm mild steel rod.

TOOLS REQUIRED:

1. Lathe

2. Cutting tool

3. Vernier caliper

4. Try square

5. Scriber

6. Vernier height gauge

SEQUENCE OF OPERATIONS:

1. Checking

2. Work piece

3. Tool setting

4. Facing

5. Turning

6. Tapper turning

7. Chamfering


1. FACING, PLAIN TURNING AND STEP TURNING

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DRAWING:



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WORKING STEPS:

1. The given work piece is checked for its dimension.

2. The work piece is held in the chuck. Chuck key is used to tighten the job firmly, ensuring

centering of work piece.

3. The single point cutting tool is held in the tool post and tightens the nuts using spanner.

4. Facing is done with cutting tool moving from the centre of work piece towards outside. It is

one until the required length of the job is obtained.

5. Turning is done to reduce the diameter of the job. Sufficient depth of cit is given and it is

done until the required diameter of the job is obtained.

6. Finally the dimension of work piece is again checked.

RESULT:

Thus the required size and shape of the given work piece is obtained.


Department of Mechanical Engineering Assessment of Practical

Description Maximum Marks Marks Obtained

Performance 25

Record 15

Viva – Voce 10

Total 50

16

DRAWING:

105

32

BEFORE MACHINING

Ø

2040

AFTER MACHINING

30 252040

Ø Ø



TAPER TURNING

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Ex. No: Date: AIM:

To obtain the required shape and size of the work piece by taper turning operation using

compound rest & Tailstock set over method.

MATERIALS SUPPLIED:

Cylindrical work piece of diameter 32 mm and length105 mm mild steel rod.

TOOLS REQUIRED:

1. Lathe

2. Cutting tool

3. Vernier caliper

4. Try square

5. Scriber



1. Checking

2. Work piece setting

3. Tool setting

4. Facing

5. Turning

6. Taper turning


2. TAPER TURNING

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DRAWING:



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WORKING STEPS:




3. The single point cutting tool is held in the tool post and tightens the nuts using Tool post

key.





6. Next step taper turning is done on the work piece, as per the taper angle already

calculated. Then the compound rest base is swiveled and set at half taper angle. Cutting

tool is moved at an angle to the lathe axis. Tool is moved by the compound rest hand

wheel.

7. For chamfering to be done at the end of the work piece, the tool is held at 450 to the lathe

axis and is fed against the rotating work spice.


RESULT:



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DRAWING:

105

32

BEFORE MACHINING

Ø



V – THREAD CUTTING

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Ex. No: Date: AIM:

To obtain the required shape and size of the work piece by turning and thread cutting.

MATERIALS SUPPLIED:


TOOLS REQUIRED:

1. Lathe

2. Cutting tool

3. Vernier caliper

4. Try square

5. Scriber



1. Checking


3. Tool setting

4. Facing

5. Turning

6. Chamfering

7. Thread cutting.


3. SINGLE & V-START MULTI THREAD CUTTING

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DRAWING:



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WORKING STEPS:









6. For chamfering to be done at the end of the work piece, the tool is held at 450 to the lathe

axis and is fed against the rotating work spice.

7. The cutting tool in the tool post is taken out. Thread cutting tool is held in the tool post and

tightened the nuts.

8. For right hand thread the lead screw rotates in clock wise direction and for left thread, it

rotates in anti clock wise direction. The carriage is engaged to lead screw and automatic

feed is given.

9. Suitable depth is given and thread is cut on the work spice.

10. Finally the dimension of work piece and pitch of the thread are again checked.

RESULT:





Performance 25

Record 15

Viva – Voce 10

Total 50

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DRAWING:

105

32

BEFORE MACHINING

Ø

AFTER MACHINING

60 40

30Ø



KNURLING

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Ex. No: Date: AIM:

To obtain the required shape and size of the work piece by Facing, plain turning and knurling.

MATERIALS SUPPLIED:


TOOLS REQUIRED:

1. Lathe

2. Cutting tool

3. Vernier caliper

4. Try square

5. Scriber


7. Knurling tool


1. Checking


3. Tool setting

4. Facing

5. Turning

6. Knurling


4. KNURLING

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DRAWING:



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WORKING STEPS:









6. Fix the knurling tool in the tool post.

7. Move the carriage outward, and then move it longitudinally, and give a small cross feed.

Repeat this step until knurling of required length is done.


RESULT:



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DRAWING:

105

32

BEFORE MACHINING

Ø

AFTER MACHINING

100

25

30 20

Ø Ø


BORING AND INTERNAL THREAD CUTTING


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Ex. No: Date:

AIM:

To obtain the required shape and size of the work piece by Facing, plain turning and Boring

and internal threading.

MATERIALS SUPPLIED:


TOOLS REQUIRED:

1. Lathe

2. Cutting tool

3. Vernier caliper

4. Try square

5. Scriber


7. Boring tool and internal thread cutting tool.


1. Checking


3. Tool setting

4. Facing

5. Turning

6. Boring

7. Thread cutting.


5. BORING AND INTERNAL THREAD CUTTING

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DRAWING:



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WORKING STEPS:









6. Fix the boring tool in the tail stock.

7. Slowly given the feed by rotating the wheel in the tailstock which moves the tool

longitudinally to producing a boring.

8. Fix the internal threading tool, to cut the internal thread.


RESULT:





Performance 25

Record 15

Viva – Voce 10

Total 50

33

UNIT – II WELDING

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INTRODUCTION

Welding is the metal joining method wherein localized coalescence is produced either by

heating the metal to suitable temperatures, with or without use of filler metal or by application of

pressure.

The filler material has similar composition and melting point temperatures as the base metal. It

is used to fill gap between the joint surfaces.

TYPES OF WELDING

1. PLASTIC WELDING:

The pieces of metal to be joined are heated to the plastic state and then forced together by external

pressure without the filler material.

a. FORGE WELDING:

The work pieces are placed in a forge or other appropriate furnace and heated within the area to be

joined to the plastic condition. Then parts are quickly superimposed and worked into a complete union

by hand or power hammering or by pressing together.

b. RESISTNACE WELDING:

In resistance welding, a heavy electric current is passed through the metals to be joined over limited

area, causing them to be locally heated to plastic state and the welding is completed by the application

of pressure for the prescribed period of time.

c. THERMIT WELDING:

It is a fusion process in which weld is effected by pouring super heated liquid Thermit Steel, around the

parts to be united with or without the pressure.


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2. FUSION WELDING:

a. GAS WELDING:

Gas welding is a process in which the required heat to melt the surfaces is supplied by a high

temperature flame obtained by a mixture of two gases. Usually the mixture of oxygen and acetylene is

used for welding purpose.

b. OXY-ACETYLENE WELDING:

In oxy-acetylene welding Oxygen and Acetylene are the two gases used for producing flame. The

Oxygen is manly used for supporting the combustion intensity.

TYPES OF FLAMES:

1. Neutral Flame (Oxygen, Acetylene in equal proportions)

2. Oxidizing Flame (excess of Oxygen)

3. Reducing Flame (excess of Acetylene)


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WELDING TECHNIQUES:

There are two techniques in gas welding, depending upon the ways in which the welding rod and the

welding torch are used.

(i) Leftward technique or Forehand welding method

(ii) Rightward technique or Backhand welding method.

(I) LEFTWARD TECHNIQUE:

1. The welder holds welding torch in his right hand and filler rod in the left hand.

2. The welding flame is directed away form the finished weld.

ADVANTAGES:

1. The flame is pointed in the direction of welding; it preheats the edges of joint.

2. Good control and neat appearance arc characteristics are ensured in the leftward technique.

(II) RIGHTWARD TECHNIQUE:

1. Here the welding torch is held in the right hand of the welder and the filler rod in the left.

2. The welding flame is directed towards the finished weld (i.e. opposite to that when employing

the leftward technique)

ADVANTAGES:

1. As the flame is always directed towards the solidified weld, it results in annealing effect and

better mechanical properties are obtained.

2. Very little agitation is produced because torch moves in a straight line.


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FILLER METAL:

It is the material that is added to the weld pool to assist in filling the gap. Filler metal forms an integral

part of the weld. The filler metal is usually available in rod form. These rods are called filler rods.

FLUXES:

During the welding, if the metal is heated in air, oxygen in the air combines with the metal to form

oxides which result in poor quality, low strength welds or in some cases may even make welding

impossible. In order to avoid these problems, a flux is added during the welding. This flux prevents

oxidation by preventing oxygen from contacting the weld zone.

No flux is used in the gas welding of steel. The most commonly used flux materials are Boric acid, soda

ash and sodium chloride.

ADVANTAGES OF GAS WELDING:

1. It can be applied to a wide variety of manufacturing and maintenance situations.

2. The rate of heating and cooling is relatively slow.

3. Since the sources of heat and of filler metal are separate, the welder has control over

filler-metal deposition rates.

DISADVANTAGES OF GAS WELDING:

1. Heavy sections cannot be joined economically.

2. Flame temperature is less than the temperature of the arc welding.

3. Fluxes used in certain welding and brazing operations produce fumes that are irritating to the

eyes, nose, throat and lungs.


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ARC WELDING:

In arc welding process, the source of heat is electricity. In arc welding process, coalescence is produced

by heating the work piece with an electric arc struck between an electrode and the work piece.

Welding may be carried out in air or in an inert atmosphere. Filler material may or may not be used.

The temperature of the arc is of the order of 36000C.

PRINCIPLE OF ARC WELDING:

The heat required for joining the metals is obtained from an electric arc. The electric motor generator

or transformer sets are used to supply high electric current and the electrodes are used to produce the

necessary arc. The electrode serves as the filler rod and arc metals the surfaces so that the metals to be

joined are fused together.

The transformer type welding machine produces AC current. It takes power directly from power

supply and to produce high current and low voltage to the welding. It is least expensive.


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Motor generator type welding machine produces DC current to welding machine. This current is

having straight or reversed polarity. The polarity selected for welding depends on the electrode arc

used in the welding.

WELDING BEAD CLEANING ACCESSORIES:

1. Chipping Hammer

2. Wire Brush

3. Hand Screen

4. Helmet

5. Tongs

6. Goggles

7. Hand Gloves


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ADVANTAGES OF ARC WELDING:

1. Flux shielded manual metal arc welding is the simplest of all the arc welding processes.

2. The equipment can be portable and the cost is fairly low.

3. This process finds innumerable applications, because of the availability of a wide variety of

electrodes.

4. A big range of metals and their alloys can be welded.

DISADVANTAGES OF ARC WELDING:

1. Because of the limited length of each electrode and brittle flux coating on it, mechanization is

difficult.

2. In welding long joints (in pressure vessels), as one electrode finishes, the weld is to be

progressed with the next electrode. Unless properly cared, a defect (like slag inclusion or

insufficient penetration) may occur at the place where welding is restarted with the new

electrode.

APPLICATIONS OF ARC WELDING:

1. Today, almost all the commonly employed metals and their alloys can be welded by the arc

welding process.

2. Shielded metal arc welding is used both as a fabrication process and for maintenance and repair

jobs.

3. The process finds application in air receiver, tank, boiler and pressure vessel fabrication and

ship building.

4. Arc welding is used in building and bridge constructi


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� LAP JOINT

� T- FILLET JOINT

� GAS CUTTING AND GAS WELDING

� BRAZING

WELDING EXERCISES


42

DRAWING:



SINGLE –V- BUTT JOINT

43

Ex. No: Date: Aim:

To make a butt joint using arc welding on the given work pieces.

MATERIAL SUPPLIED:

Mild Steel Plate of size 80 X 40 X 3 mm – 2 Nos.

TOOLS REQUIRED:

1. Power Supply (AC or DC)

2. Electrodes

3. Tongs

4. Chipping Hammer

5. Wire Brush

6. Gloves

7. Apron

8. Shield

9. Safety goggles

10. Earthling clamps


1. Edge preparation (Removal of rust, scale etc)

2. Tacking

3. Welding

4. Cooling

5. Chipping

6. Cleaning

1. HORIZONTAL WELDING (BUTT JOINT)


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DRAWING:

All dimensions are in mm


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WORKING STEPS:

1. First of all, the work pieces must be thoroughly cleaned of rust, scale and other foreign

material.

2. Then the given work pieces are placed on the table in such a way that two work pieces are

brought close to each other with some gap as shown in fig.

3. Connect the positive electric supply to electrode and negative electric supply to work.

(Since the given material is thin)

4. Now the welding current output may be adjusted.

5. When current is passed, arc is produced between the electrode and work pieces.

6. Set the two work pieces in correct position like butt joint and tack at both ends of the work

pieces.

7. Then the welding is carried out throughout the length.

8. As soon as the welding process is finished, switch off the current supply and drop the work

piece into water for cooling using tongs.

9. Slags are removed by chipping process with the help of chipping hammer.

10. Finally using wire brush welded portions are cleane

RESULT:

Thus the desired butt joint is obtained using arc welding.




Performance 25

Record 15

Viva – Voce 10

Total 50

46

DRAWING:



LAP JOINT

47

Ex. No: Date: AIM:

To make a lap joint using arc welding on the given work pieces.

MATERIAL SUPPLIED:


TOOLS REQUIRED:


2. Electrodes

3. Tongs

4. Chipping Hammer

5. Wire Brush

6. Gloves

7. Apron

8. Shield

9. Safety goggles

10. Earthing clamps



2. Tacking

3. Welding

4. Cooling

5. Chipping

6. Cleaning


2. OVER LAPING WELDING (LAP JOINT)

48

DRAWING



49

WORKING STEPS:

1. First of all, the work pieces must be thoroughly cleaned to remove rust, scale and other

foreign material.

2. Now the work pieces are placed on the table in such a way that two work pieces are

overlapped one over another as shown in fig.





6. Set the two work pieces in correct position like lap joint and tack at both ends of the work

pieces as shown in fig.

7. Then the welding is carried out throughout the length of the work piece.

8. As soon as the welding process is finished, switch off the current supply

9. Then drop the work piece into water for cooling, after that slags are removed by chipping

process with the help of chipping hammer.

10. Finally by using wire brush, welded portions (weldment) are cleaned.

RESULT:

Thus the desired lap joint is obtained using arc welding.




Performance 25

Record 15

Viva – Voce 10

Total 50

50

DRAWING:



T – FILLET JOINT

51

Ex. No: Date:

AIM:

To make a T-Fillet joint using arc welding on the given work pieces.

MATERIAL SUPPLIED:


TOOLS REQUIRED:


2. Electrodes

3. Tongs

4. Chipping Hammer

5. Wire Brush

6. Gloves

7. Apron

8. Shield

9. Safety goggles

10. Earthing clamps



2. Tacking

3. Welding

4. Cooling

5. Chipping

6. Cleaning

3. VERTICAL WELDING T – FILLET JOINT


52

DRAWING:



53

WORKING STEPS:

1. First of all, the work pieces must be thoroughly cleaned to remove rust, scale and other

foreign material.

2. Now the work pieces are placed on the table in such a way that two work pieces are

brought close to each other ‘T’ shape is formed as shown in fig.





6. Set the two work pieces in correct position like T-Fillet joint and tack at both ends of the

work pieces as shown in fig.

7. The joint is placed on a welding table in a flat position by keeping the tack side down.

8. Then the welding is carried out throughout the length of the work piece.

9. As soon as the welding process is finished, switch off the current supply

10. Then drop the work piece into water for cooling, after that slags are removed by chipping

process with the help of chipping hammer.

11. Finally by using wire brush, welded portions (weldment) are cleaned.

RESULT:

Thus the desired T-Fillet joint is obtained using arc welding.


54

DRAWING:



GAS CUTTING AND GAS WELDING

55

Ex. No: Date: AIM:

To cut and joint given metal sheets in gas welding

MATERIAL SUPPLIED:


TOOLS REQUIRED:

1. Oxygen and acetylene gas cylinders with pressure regulators and pressure gauges.

2. Gas welding torch

3. Filler rod

4. Safety gloves

5. Goggle

6. Chipping hammer

7. Wire brush



2. Tacking

3. Welding

4. Cooling

5. Chipping

6. Cleaning


4. GAS CUTTING AND GAS WELDING

56

DRAWING:



57

WORKING STEPS:

1. The surface of the plate to be welded is cleaned for perfect joint and more strength.

2. The metal sheets to be welded are positioned properly.

3. Open the acetylene and oxygen cylinder valves slowly, then open the acetylene valves in

the torch. Keep the tip of the torch away from the body and light it using lighter.

4. Adjust the oxygen and acetylene valves in the torch slowly to get the required flame for

welding.

5. Maintain the gap 3 mm between to be welded and inner cone of the flame.

6. The welding torch and filler rod are moved backwards along line into be welded.

7. Complete the welding process by removing slag using chipping hammer.

Result:

The two metal sheets are welded in gas welding.




Performance 25

Record 15

Viva – Voce 10

Total 50

58

BRAZING – INTRODUCTION- for demonstration purpose

Brazing is the process of joining metals with a nonferrous filter metal that has a melting point

below that of the metals being joined. By AWS definition, the melting point of the filler metal will be

above 8000F (4270C). Below this temperature are the solders. The filler metal must wet the surfaces to

be joined, that is, there must be a molecular attraction between the molten filler material and the

materials being joined. The brazing alloy, when heated to the proper temperature, flows into the small

joint clearances by capillary action. A limited amount of alloying occurs between the filler metal and

the base metal at elevated temperature. As a result, the strength of the joint when properly made may

exceed that of the base material. The strength is attributed to three sources, atomic forces between the

metals at the interface; alloying, which comes from diffusion of the metals at the interface; and inter

granular penetration.

The heat for brazing may be provided in many different ways, the most common o f which are by

torch, induction furnace, and hot dipping.

TYPES OF BRAZING:

1. TORCH BRAZING:

Torch brazing is one of the oldest and most widely used methods of heating for brazing; it is versatile

and adaptable to most jobs. It is especially good for repair work in the field and for small-lot jobs in the

shop. As it is a manual operation, torch brazing may have high labor costs, and the skill and judgment

of the torch operator will determine the quality of work. Torch brazing may be done with the use of

natural gas and oxygen, air and acetylene, butane, propane, MAPP, and the regular oxyacetylene.

2. INDUCTION BRAZING:

The heat of induction brazing is furnished by an AC coil placed in close proximity to the joint. The

high-frequency current is usually provided by a solid-state oscillator that produces a frequency of 200,

000 to 5, 000, 000 Hz. These alternating high-frequency currents induce opposing currents in the

work, which, by electrical resistance, develop the heat. This method has the advantage of


59

providing good heat distribution, accurate heat control, uniformity of results, and speed. It is

especially good for certain types of repetitive work that require close control.

3. FURNACE BRAZING:

Parts are to be furnace brazed have the flux and brazing material pre placed in the joint. If the furnace

has a neutral or shielding atmosphere, the flux may not be necessary. The furnace may be batch or

conveyor type. Automatic controls regulate both time and temperature and, where applicable,

atmosphere. The three steps used in copper-hydrogen furnace brazing are shown in figure.


60

4. DIP BRAZING:

Dip brazing gets its name from the fact that parts are jigged (or in some cases the parts are self-

jiggning, as shown in fig) and are placed in a chemical or molten-metal bath maintained at the correct

brazing temperature. In a chemical bath, the parts are first thoroughly cleaned and then assembled

with a filler-metal placed on or in the joint. The bath, usually molten salts, is maintained at a higher

temperature than the filler metal being used. After dipping, the parts are removed and immediately

cleaned to remove the flux. The number and size of the parts to be brazed limited only by the capacity

of the bath and the handling facilities.

5. PASTE BRAZING:

A newer development in brazing is paste brazing. Anyone who has done any brazing knows there is

some skill involved. After the appropriate type and amount of flux and filler metal are selected, the

appropriate temperature must be chosen. Too little flux means the base metal will not be sufficiently

cleaned, resulting in a weak joint. To ensure strong joints, excessive flux is often used, this wastes

material, requires more cleaning, and can erode parts and fixtures.


61

6. PASTE ALLOY PROCESS:

Paste alloys are designed to overcome the problems given in the previous paragraph. Paste alloys are

blends of filler metal in powdered form and a flux that are held in suspension by a paste-type binder.

Premixing of flux and filler ensures the proper proportions of each and keeps the alloy localized to the

joint area. Pastes rely on capillary action to spread the metal and flux over the joint area. Paste brazing

filler materials are available in silver, nickel, copper and gold based formulations.

7. BRAZE WELDING:

Braze welding is similar to brazing in that the base metal is not melted but joined by an alloy of lower

melting point. The main difference is that in braze welding the alloy is not drawn into the joint by

capillary action. A braze-welded joint is prepared very much lik a joint is prepared for welding except

that an effort should be made to avoid sharp corners, because they are easily overheated and may also

be points of stress concentration.

BRAZING FLUXES:

Generally, fluxes are available in 3 forms namely powder, paste or liquid. Of the three, paste is most

commonly used, although powdered flux is frequently mixed with water or alcohol to give a paste like

consistency.

BRAZING FILLER METALS:

Brazing filler metals are divided into seven classifications. In order of popularity, these are silver,

copper, copper-zinc, copper-phosphorus, aluminium-silicon, copper-gold, and magnesium. These

alloys are produced in many forms such as wire, rods, coated sheets, and powder. Frequently, brazing

alloys are performed into rings or special shapes to simplify placement of the correct amount at the

joint.

ADVANTAGES OF BRAZING:

Brazing is well suited to mass-production techniques for joining both ferrous and non-ferrous

metals. Some of the principal advantages are

1. Dissimilar metals can be joined easily.

2. Assembles can be joined in a virtually stree-free condition.

3. Complex assemblies can be joined in several steps by using filler metals with progressively

lower melting temperatures.

4. Materials of different thickness can be joined easily.


62

5. Brazed joints require little or no finishing other than flux removal.

LIMITATIONS OF BRAZING:

1. Joint design is somewhat limited if strength is a factor.

2. Joining is generally limited to sheet-metal thicknesses and relatively small assembles.

3. Cost of joint preparation can be high.


63

UNIT – III SHEET METAL

64

INTRODUCTION

Sheet metal work is working on the metal of 16 gauges to 30 gauges, with hand tools and

simple machines into different forms by cutting, forming into shape and joining.

Sheet metal work is one of the major applications in engineering industry. It has its own

significance as a useful trade in engineering work.

APPLICATION OF SHEET METAL

Sheet metal work is used for making

Hoppers

Funnels

Various ducts

Chimneys

Ventilating pipes

Machine tool guards

Boiler etc.

PROCEDURE FOR SHEET METAL WORK

The exact size and shape of the sheet to be cut is given by the development of the concerned

object.

The development is drawn on a flat sheet of metal and then the sheet is cut.

The cut sheet is folded or rolled to the required shape before the joints are made by welding or

any form of fastening.

METAL USED IN SHEET METAL WORK

a. Black iron

b. Galvanized iron

c. Stainless steel

d. Copper

e. Aluminum


65

f. Tin plate

g. Lead etc.

Selection of these metals is based upon the type of process.

TOOLS USED IN SHEET METAL

1. CUTTING TOOLS(CHISELS, SNIPS OR SHEARS)

(a) CHISELS: Chisels are used in sheet metal work for cutting sheets, rivets, bolts, and

chipping operations. Though there are many types of chisels available, round nose chisel

and flat chisel are mostly used for sheet metal work.

(b) SNIPS (OR) SHEARS: Snips are hand shears, varying in length from 200mm to 600mm.

and 250mm length is most commonly used.

STRAIGHT SNIPS are used for cutting along outside curves and Straight lines.

CURVED SNIPS OR BENT SNIPS are used for trimming along inside curves.

2. STRIKING TOOLS

(a) Hammers (b) Punches


66

(a) Hammers: Hammers are used in sheet metal work for following, raising, Stretching or

throwing off. The following hammers are mostly used in sheet metal work.

(i) Riveting hammers

(ii) Raising hammers

(iii) Setting hammers

(b) Punches: In sheet metal work, punch is used for marking out work locating centers etc.

The following two types of punches are widely used.

(i) Prick punch

(ii) Centre punch.

3. SUPPORTING TOOLS

Stacks: Stacks are nothing but sheet metal workers anvils used for bending, seaming or

forming, using a hammer or mallet. The following fig. shows different shapes and sizes of

stakes.

4. BENDING TOOLSPliers: Pliers are mainly used for bending the sheet metal to the required

shape. It is also used for holding and cutting the sheet metal. Flat nose pliers and round nose

pliers are used in sheet metal work for forming and holding.


67

5. LAYOUT TOOLS.

Steel rule: It is used for measuring and laying out small work. It can measure with an

Accuracy of up to 0.5mm.

Scriber: It is a long wire of steel with its one end sharply pointed and hardened to scrach line

on sheet metal in laying out patterns.

Dividers: Dividers are used for drawing circles or arcs on sheet metal. They are to mark a

desired distance between points and to divide lines into parts

Trammels: It is used for making of arcs and circles. Maximum size of the arc that can be scribed

depends on the length of the beam in scriber.

SHEET METAL OPERATIONS

1. Shearing

2. Bending

3. Drawing

4. Squeezing.


69

� SQUARE TRAY

� FUNNEL

SHEET METAL EXERCISES

70

DRAWING:

150

100

5

5



SQUARE TRAY

71

Ex. No: DATE: AIM: To make a tray from given sheet metal.

MATERIL SUPPLIED:

22 gauge Galvanized Iron (GI) sheet.

TOOLS REQUIRED:

1. Snips

2. 2. Ball peen hammer

3. Mallet

4. Steel rule

5. Scriber

6. Divider

7. Rivet set

8. Dot punch

9. Stakes


1. Checking

2. Leveling

3. Marking

4. Cutting

5. Hemming

6. Bending

7. Riveting


1. FABRICATION OF SHEET METAL TRAY

72

DRAWING:



73

WORKING STEPS:

1. The size of the given sheet is checked using a steel rule.

2. Then the sheet is leveled on the leveling plate using a mallet.

3. The dimensions are marked as shown in fig

4. The sheet is cut as per the marked dimensions by straight snips.

5. Then a single hemming is made on the four sides of tray as shown in fig.

6. These four sides of the tray are bent to 90 0 using stakes anvil.

7. Finally the corners of the tray are joined by riveting.

RESULT:

Thus the tray is made from the given metal sheet.




Performance 25

Record 15

Viva – Voce 10

Total 50

74

23,09

PART - 1

PA

RT

- 2

49,28

50

80

L

L1

P

Q

O

Ø


FUNNEL


75

Ex. No: DATE:

AIM:

To make a funnel from given sheet metal.

MATERIL SUPPLIED:

22 gauge Galvanized iron (GI) sheet.

TOOLS REQUIRED:

1. Snips

2. Ball peen hammer

3. Steel rule

4. Scriber

5. Divider

6. White paper

7. Protractor

8. Stakes


1. Checking

2. Marking on paper

3. Marking on sheet metal

4. Cutting

5. Folding.

6. Hemming

7. Soldering.

FABRICATION OF FUNNEL


76

DRAWING:



77

WORKING STEPS:

1. The size of the given sheet metal is checked for its dimensions using steel rule.

2. The required developed of surface is being made on the white paper which is overlapped

on the sheet metal.

3. The marking is done on the sheet metal as per the development being done on the paper.

4. Now using straight snips, unwanted materials are removed.

5. Now fold and bend the work piece to make the funnel shape and joint is made on the work

piece.

6. Then using groove, locked grooved joint is made for about 5mm. Also, hemming is done in

the bottom of the funnel.

7. In between top face and bottom face, butt joint is made using solder.

8. Finally, trimming and finishing operation are being carried out.

RESULT:

The funnel of the required dimensions is made from the given metal sheet.




Performance 25

Record 15

Viva – Voce 10

Total 50

79

UNIT – IV PREPARATION OF

SAND MOULD

80

INTRODUCTION

Producing Components by casting has been used since the earliest days of civilization. Lot of shapes

and sizes can be prepared in a casting process. To make the casting of a component, a cavity of desired

shape is t be produced in which the molten metal is poured.

Mould is the cavity to the required shape made in modeling sand or other material. The process of

modeling consists of all operations done to make a mould.

PATTERN:

Pattern is the model used to get required casting. It is used to produce the moduld cavity in

sand.

FOUNDRY:

The place where modeling and casting are done is known as foundry.

MOULDING SAND OR GREEN SAND:

It is a maximum of sand and additives such as water, bentonite, inoculent, sodium silicate etc,

used to create mould cavity.

COMPONENTS REQUIRED FOR MOULDING:

The following components are essential for producing mould.

(i) Moulding Sand(Green sand)

(ii) Moulding Boxes

(iii) Pattern

(iv) Moulding tools

MOULDING SAND

Composition

It is a special type of sand used for making mould. Moulding sand has three

constituents. They are

(i) Sand (ii) Binder (iii) Additive


81

SAND:

It has silica, clay and moisture. Silica is the main constituent of sand. Silica has 80 to 90 %

silicon dioxide. Silicon gives refractoriness to the sand.

CLAY:

Clay is another constituent of sand. Clay gives more bonding strength to the sand. Generally

sand has 5 to 20 % clay. Moisture is the water added to the sand. It gives the bonding action. In general

2 to 8 % water is added to the sand.

BINDERS:

Binders are added to the moulding sand to bring the property of the cohesiveness. The binder

binds the sand grains together and brings strength. There are three types of binders.

a) Clay type binders eg: Bentonite

b) Organic binders eg.Resin

c) Inorganic binders eg. Sodium silicate.

ADDITIVE:

By adding an additive, properties like strength, refractoriness and permeability can be

increased.

PATTERNS:

A pattern is the replica of the desired casting, used to produce a mould into which liquid metal

is poured. When pattern packed in a suitable material produces a cavity called mould. This cavity when

filled molten metal produces the desired casting,

The following pattern materials are widely used.

i) Wood and wood products

ii) Metals and alloys

iii) Plastic and rubbers

iv) Plasters and Waxes


82

PATTERN ALLOWANCES

The various pattern allowances are mentioned below.

i) Shrinkage or Contraction allowance

ii) Machining or Finishing allowance

iii) Draft or Taper allowance

iv) Distortion allowance

v) Shake or Rapping allowance

PATTERN TYPES

Various types of pattern are

a) One piece (Solid ) pattern

b) Split pattern

c) Loose piece pattern

d) Match plate pattern

CORE MAKING PROCEDURE

Core making is done in the following steps.

1. Moulding a green sand core.


83

2. Baking

3. Finishing

4. Coating

MOULDING BOXES

1. Cope (Top box)

2. Check (middle box)

3. Drag (bottom box)

MOULDING TOOLS:

1. Shovel

2. Sieve

3. Trowel

4. Rammers

5. Sprue pin

6. Strike off bar

7. Lifter

8. Gate cutter

9. Runner

10. Riser

11. Vent rod

12. Draw spike

13. Bellow

ADVANTAGES OF SAND CASTING:

1. Use is widespread; technology well developed


84

2. Materials are inexpensive, capable of holding detail and resist deformation when

heated.

3. Process is suitable for ferrous and non-ferrous metal casting.

4. Handles a more diverse range of products than any other casting method.

5. High levels of sand reuse are achievable.

LIMITATIONS OF SAND CASTING

1. Typically limited to one or more a small number moduls per box.

2. Sand: metal ratio is relatively high.

3. High level of waste is typically generated, particularly sand, bag house dust and

spent shot.


85

MOULDING TOOLS


87

� SOLID PATTERNS

� MOULD WITH SPLIT PATTERN

� MOULD WITH LOOSE – PIECE PATTERNS

� INJECTION MOULDING

FOUNDRY EXERCISES

88

DRAWING:


SOLID PATTERN


89

Ex. No: Date: AIM: To make the mould of solid pattern

MATERIAL REQUIRED:

Molding sand, Parting sand, facing sand, pattern, molding boxes etc.

TOOLS REQUIRED:

1. Shovel

2. Sieve

3. Trowel

4. Rammers

5. Sprue pin

6. Strike off bar

7. Lifter

8. Gate cutter

9. Runner

10. Riser

11. Vent rod

12. Draw spike

13. Bellow


1. Sand preparation

2. Core preparation

3. Placing the pattern on the moulding board.


1. MOULD WITH SOLID PATTERN

90

DRAWING:

Dimensions are in mm


91

4. Ramming of drag

5. Placing runner and riser

6. Ramming of cope

7. Removal of pattern, runner, riser

8. Gate cutting.

WORKING STEPS:

1. The pattern is placed on the moulding board.

2. A suitable core is prepared and placed in the hole of the pattern.

3. Clay washing is done inside the drag surface.

4. Parting sand is applied over the pattern.

5. Box is filled with smooth moulding sand and proper ramming is done using flat and

peen rammer.

6. Excess sand is removed using the strike off bar.

7. The drag is turned upside down.

8. The cope is placed on the drag after doing clay wash.

9. The runner and riser are placed over the pattern.

10. After applying parting sand, moulding, sand is filled over the part ten.

11. Ramming is done to get a rigid mould.

12. Using strike off bar excess sand is removed.

13. Vent holes are made using vent rod.

14. Runner and riser are removed and a funnel shape is made on the runner hole.

15. Cope is kept aside and the pattern is removed using draw spike

16. The cope is placed on the drag.

RESULT:

Thus the gear mould is prepared and ready for casting.


Department of Mechanical Engineering

Assessment of Practical

Description Maximum Marks

Performance 25

Record 15

Viva – Voce 10

Total 50

92

DRAWING:



MOULD WITH SPLIT PATTERN (V-GROOVED PULLEY)

93

Ex. No: Date:

AIM: To prepare a sand mould using a split pattern.

MATERIAL REQUIRED:

Moulding sand, Parting sand, facing sand, split pattern, Moulding boxes etc.

TOOLS REQUIRED:

1. Showel

2. Sieve

3. Trowel

4. Rammers

5. Sprue pin

6. Strike off bar

7. Lifter

8. Gate cutter

9. Runner

10. Riser

11. Vent rod

12. Draw spike

13. Bellow


1. Sand preparation

2. Core preparation

3. Placing the pattern on the moulding board


2. MOULD WITH SPLIT PATTERN (V-GROOVED PULLEY)

94

DRAWING:



95

4. Ramming of drag


6. Ramming of cope


8. Gate cutting.

WORKING STEPS:

1. The mould box, pattern, tools, and the table /floor are cleaned.

2. The drag is filled with green sand after positioning lower part of the pattern on the

table.

3. The green sand is rammed carefully and the excess sand is struck off.

4. Till the drag upside down and sprinkle river sand on top of it.

5. The cope is positioned on the top of the drag and upper part of the pattern is positioned

carefully.

6. Position the sprue pin and riser pin, then the fill cope with sand ramming is done and

the excess sand is struck off.

7. Remove the sprue pin and the riser pin carefully

8. Apply water on the edges of the pattern and remove them carefully using the draw

spike, then finish the cavity.

9. Vent holes are made using vent wire.

10. A funnel – shaped opening and gate is made to pour the molten metal.

RESULT:

Thus the mould cavity of the given split pattern is obtained.




Performance 25

Record 15

Viva – Voce 10

Total 50

96

DRAWING:



MOULD WITH LOOSE-PIECE PATTERN

97

Ex. No: Date:

AIM:

To prepare a sand mould using a loose – piece pattern.

MATERIAL REQUIRED:

Moulding sand, Parting sand, facing sand, pattern, Molding boxes etc.

TOOLS REQUIRED:

1. Showel

2. Sieve

3. Trowel

4. Rammers

5. Sprue pin

6. Strike off bar

7. Lifter

8. Gate cutter

9. Runner

10. Riser

11. Vent rod

12. Draw spike

13. Bellow


1. Sand preparation

2. Core preparation

3. Placing the pattern on the moulding board


3. MOULD WITH MOULD WITH LOOSE-PIECE PATTERN

98

DRAWING:



99

4. Ramming of drag


6. Ramming of cope


8. Gate cutting.

WORKING STEPS:

1. The mould box, pattern, tools, and the table /floor are cleaned.

2. The drag is filled with green sand after positioning lower part of the pattern on the

table.

3. The green sand is rammed carefully and the excess sand is struck off.

4. Till the drag upside down and sprinkle river sand on top of it.

5. The cope is positioned on the top of the drag and upper part of the pattern is positioned

carefully.

6. Position the sprue pin and riser pin, then the fill cope with sand ramming is done and

the excess sand is struck off.

7. Remove the sprue pin and the riser pin carefully

8. Apply water on the edges of the pattern and remove them carefully using the draw

spike, then finish the cavity.

9. Vent holes are made using vent wire.

10. A funnel – shaped opening and gate is made to pour the molten metal.

RESULT:

Thus the mould cavity of the given loose piece pattern is obtained.




Performance 25

Record 15

Viva – Voce 10

Total 50

101

INJECTION MOULDING - INTRODUCTION- for demonstration purpose

WORKING PRINCIPLE:

The injection moulding is used to achieve high speed moulding of thermoplastics. The working

principle of this process is tat the molten thermoplastic is injected into a mould under high pressure.

For achieving high pressure, the plunger system is used.

OPERATION:

The moulding material is loaded into a hopper from which it is transferred to a heating section by a

feeding device where the temperature is raised to 1500 C - 3700 C. The material melts and is forced by

an injection ram or by plunger through a nozzle and sprue in a closed mould which forms the part.

There are two types of injection moulding and it is given below.

RAM OR PLUNGER TYPE INJECTION MOULDING:

The ram and plunger type injection moulding has two units.

1. Injection unit

2. Clamping unit.

So it may be split in order to eject the finished component.

Initially, the polymer is filled in a hopper. Then it goes to the heating section where the polymer is

melted and the pressure is increased. The heated material is injected by the ram under pressure. So, the


102

heated material is forced to fill in mould cavity through the nozzle to get the required shape of the

plastics. Here, the mould is water-cooled type.

SCREW TYPE INJECTION MOULDING:

In this type also, there are two units to split and eject the finished component such as

1. Injection unit

2. Clamping unit

The injection unit has hopper, screw and heating section. In clamping section, it has mould.

In screw type moulding machine, initially the pellets are fed into the hopper. The resins are pushed

along with the heated reciprocating screw. The screw is moved forward to force the plastic material

into the mould. The screw itself is moving backwards and allowing the accumulation of enough

material to fill the mould.

The rotation of the screw provides the plasticizing action by shearing and frictional effects. The axial

motion of the screw provides the filling action.

The jet moulding process is used to find the problems occurred in injection moulding process. The

reaction moulding is the recent development in injection moulding. In reaction moulding, the low

viscosity monomers are used in the mould. A chemical reaction takes place between resins at low

temperature and a polymer is created.


103

In jet moulding, the plastic is preheated about 930 C in the cylinder surrounding the nozzle. The

reaction moulding is suitable for the production of polyurethane moulding.

ADVANTAGES OF INJECTION MOULDING:

1. High production capacity and less material losses.

2. Low cost and less finishing operation.

3. It is used for making complex threads and thin walled parts.

4. Accuracy becomes ± 0.025 mm.

5. Wide range of shapes can be moulded.

APPLICATIONS:

1. It is used in making parts of complex threads.

2. Production of Intricate shapes like thin walled parts.

3. Production of typical parts like cups, containers, tool handles, toys, knobs, plumbing fittings.

4. Production of electrical and communication components like telephone receivers.

LIMITATIONS:

1. Equipment of cylinder and die should be non-corrosive.

2. Reliable temperature controls are essential.

The injection capacity of injection moulding machines ranges from 12,000 mm3 to2.2 X 106 mm3.


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