Laboratory_manual Mn 201

7/28/2019 Laboratory_manual Mn 201

1/35

LABORATORY MANUAL

MANUFACTURING PROCESSES

INDIAN INSTITUTE OF INFORMATION TECHNOLOGY DESIGNAND MANUFACTURING, JABALPUR

1


2/35

Contents

Metal removal processes

Single point tool operations1. Turning

Experiment no. 1

Experiment no. 2

2. Shaping

Experiment no. 3

Multipoint tool operations

1. Milling

Experiment no. 4

Experiment no. 5

2. Fitting, drilling and taping

Experiment no. 6

Measurement of parts

Metal joining processes

Arc welding

MMAW

Experiment no. 7

Oxyfuel gas weldingOxyacetylene welding

Experiment no. 8

Sheet metal forming

Development of surfaces

Experiment no. 9

Inspection of parts

Non destructive testing

1. Pulse echo method

Experiment no. 10

2. Magnetic particle inspection

Experiment no. 11

2


3/35

MACHINING PROCESSES

Machining is one of the processes of manufacturing in which the specified shape to the work

piece is imparted by removing surplus material. Conventionally this surplus material from the

work piece is removed in the form of chips by interacting the work piece with an appropriate

tool. This mechanical generation of chips can be carried out by single point or multi point

tools or by abrasive operations. These are summarized below.

Machining Processes

Single point tool operations Multi-point tool operations Abrasive operations

1. Turning 1. Milling 1. Grinding

2. Boring 2. Drilling 2. Lapping

3. Shaping 3. Tapping 3. Honing

4. Planing 4. Reaming 4. Super-finishing

5. Hobbing

6. Broaching

7. Sawing

The process of chip formation in metal cutting is affected by relative motion between the tool

and the work piece achieved with the aid of a device called machine tool. This relative

motion can be obtained by a combination of rotary and translatory movements of either the

tool or the work piece or both. The kind of surface that is produced by the operation depends

on the shape of the tool and the path it traverses through the materials. When the work pieceis rotated about an axis and the tool is traversed in a definite path relative to the axis, a

surface of revolution is generated. When the tool path is parallel to the axis, the surface

generated is a cylinder as in straight turning or boring operations. Similarly, planes may be

generated by a series of straight cuts without rotating the work piece as in shaping and

planning operations (Fig.3). In shaping the tool is reciprocating and the work piece is moved

crosswise at the end of each stroke. Planning is done by reciprocating the work piece and

crosswise movement is provided to the tool.

Surface may be machined by the tools having a number of cutting edges that can cut

successively through the work piece materials. In plane milling, the cutter revolves and

moves over the work piece as shown Fig. 4. The axis of the cutter is parallel to the surfacegenerated. Similarly in drilling, the drill may turn and be fed into the work piece (Fig. 5).

The machine tools, in general, provide two kinds of relative motions. The primary motion is

responsible for the cutting action and absorbs most of the power required to perform the

machining action. The secondary motion of the feed motion may proceed in steps or

continuously and absorbs only a fraction of the total power required for machining. When the

secondary motion is added to the primary motion, machine surfaces of desired geometric

characteristics are produced.

3


4/35

4

Fig. 1 Straight turning Fig. 2: Straight boring

Fig. 3: Shaping and planing

Fig. 4: Plain milling

Work piece

Tool

Fig. 5: Drilling


5/35

INTRODUCTION TO LATHE MACHINE AND EXERCISE ON TURNING

TIME: 9.00 Hours

PART (A)

OBJECTIVE

To study the characteristic features of lathe.

OUTLINE OF PROCEDURE

i) Run the machine at low speed and observe the motions, which control the shapes

of the surfaces produced. Note particularly the features, which control the

geometrical form of the surface.

ii) Learn the names of the major units and the components of each machine. Record

these details (Table A). (Please ensure that the main isolator switch is off and

check that the machine cannot be inadvertently started. Do not remove guards).Use the manufacture's handbook for details that cannot be inspected.

iii) Record the obtainable speed and feed values (Table B).

iv) Note down the special features of the speed and feed control on each machine.

v) Pay attention to the following:

a. Size specification of various machine tools.

b. Machine tool structures and guide ways I slide ways.

c. Drive mechanism for primary (cutting) motion.

d. Drive mechanism for secondary (feed) motion.

OBSERVATIONS

(a) Record the following in a tabular form:

Machine Tool Specifications (Table A)

Machine Type & Make SizeSpeed given to Feed given to

Type of

Surface

Tool Work Tool Work Produced

Lathe

Speed and Feed Data (Table B)

No.Lathe

Speed Feed

1.

2.

(b) Plot the lathe speeds against No. from Table B on a semi-log graph paper and show thatthe speed steps are in G.P.

5


6/35

PART (B)

Experiment # 1: To make the part shown in the sketch from a mild steel rod on a Lathe

having three jaw chuck.

Fig. 6: Part to be produced using lathe machine

EQUIPMENT

List all tools and instruments used.


Hold the bar in a three jaw chuck and face the end with a right hand facing tool. Turn the bar

to the required diameter with rough cuts. Face the steps and finish the diameters to therequired sizes. Machine the roots and the groove with form tools. Knurl the required surface.

Cut the threads.

OBSERVATIONS

(a) Measure all dimensions (up to second decimal place) on the specimen turned by your

group. Make a neat sketch and indicate all measured dimensions.

(b) Show the calculation of the required gear ratio for thread cutting.

(c) Sketch the main drive unit of the lathe and show how the speed steps are obtained.(d) Make the process plan to manufacture the part.

(e) Note down the time required to perform different operations.

(f) Calculate the manufacturing cost of part by taking various assumptions.

6


7/35

Experiment # 2: To make the part shown in the sketch from a mild steel rod on a Lathe using

four jaw chuck.

Fig. 7: Part to be produced using lathe machine

EQUIPMENT



Hold the bar in a four jaw chuck and face the end with a right hand facing tool. Make central

hole with a center drill. Adjust the position of the workpiece and match the centre with the

axis of the machine. Turn the bar to the required diameter with rough cuts. Face the steps and

finish the diameters to the required sizes. Machine the roots and the groove with form tools.

Machine the taper with the help of the cross-slide swiveling arrangement. Mark the centre of

the eccentric circle. Readjust the position of the job piece and align the centre of the eccentriccircle with the axis of the machine. Turn the bar upto the required diameter and length.

OBSERVATIONS

(a) Measure all dimensions (up to second decimal place) on the specimen turned by your


(b) Discuss briefly how tapered portion was turned.

(c) Make the process plan to manufacture the part.

(d) Note down the time required to perform different operations.(e) Calculate the manufacturing cost of part by taking various assumptions (Same

assumptions should be taken for similar type of manufacturing activities).

7


8/35

SHAPING: INTRODUCTION AND PRACTICE

TIME: 2.15 Hours

PART (A)

OBJECTIVE

To study the characteristic features of Shaper





ii) Learn the names of the major units and the components of each machine.

iii) Record these details (Table A). (Please ensure that the main isolator switch is off

and check that the machine cannot be inadvertently started. Do not remove

guards). Use the manufacture's handbook for details that cannot be inspected.

iv) Record the obtainable speed and feed values (Table B).

v) Note down the special features of the speed and feed control on each machine.

vi) Pay attention to the following:


b. Machine tool structures and guide ways / slide ways.



OBSERVATION

Record the following in a tabular form:


MachineType &

MakeSize

Speed given to Feed given to Type of


Shaper


No.Shaper

Speed Feed

1.

2.

8


9/35

PART (B)

Experiment # 3: To machine a V-groove as shown in the sketch out of the work piece

provided.

Fig. 8: Part to be produced using shaper machine

EQUIPMENT



Hold the work piece in a vice and machine the top surface till the desired height is obtained.

Machine the inclined faces using right and left hand tools.

OBSERVATIONS

(a) Measure all dimensions (up to second decimal place) on the specimen machined by

your group. Make a neat sketch and indicate all measured dimensions.

(b) Calculate the machining time for the bottom surface of the specimen.

(c) Explain the quick return mechanism.

(d) Explain the use of clapper box on the machine.

9


10/35

MILLING: INTRODUCTION AND PRACTICE

TIME: 9:00 Hours

PART (A)

OBJECTIVE

To study the characteristic features of Milling machine.






these details (Table A). (Please ensure that the main isolator switch is off and

check that the machine cannot be inadvertently started. Do not remove guards).

Use the manufacture's handbook for details that cannot be inspected.








OBSERVATION



MachineType &

MakeSize

Speed given to Feed given to Type ofSurface


Milling (Vt)

Milling (Hz)


No.Milling

Speed Feed

2.

10


11/35

PART (B)

Experiment # 4: Milling keyway on the specimen shown in the sketch.

Fig. 9: Part to be produced using vertical milling machine

EQUIPMENT



1. Clamp the work piece in vice.

2. Mount the cutter on the spindle & set it in position with respect to work piece.

3. Test the cutter for run.

4. Cut the keyway to required depth using end milling cutter.

5. Change the cutting tool to T-slot cutter.

6. Complete the T-slot with the help of T-slot cutter.

OBSERVATIONS

(a) Measure the width of keyway.

(b) Observe the roughness of the surface produced and compare it with the surfaces

produced in other manufacturing processes

11


12/35

Experiment # 5: Spur gear cutting using Indexing on Milling Machine.

Introduction

Gears are one of the most commonly used elements in almost all simple or complex

mechanisms. It is therefore essential for all engineering students to know all about gears, their

manufacturing, machines and processes used for gear making. In this experiment, it is

expected that students, learn the principles, processes, procedures and practices used for gear

manufacturing.

Concepts used

1. Milling processes.

2. Cutter mounting in correct position.

3. Knowledge of spur gear.

4. Indexing process.

Fig. 10: Part to be produced using horizontal milling machine

EQUIPMENT

List all tools/cutters and instruments used.

1) Dividing head.

2) Gear cutter for cutting 5 modules.

12


13/35


Fit the form cutter on the arbor and the specimen between the centers of the dividing head

and the tail center. Carefully adjust the work piece so that the cutter just touches the top

surface of the specimen. Calculate the necessary depth of cut and then mill the teeth of the

spur gear in succession.

Stepwise Procedure

01 Mount and align the dividing head and tailstock on machine table. (use Dividing head, tail

stock, dial indicator)

02 Mount the gear-milling cutter on the arbor and test for concentricity. (use gear cutter)

03 Hold the work piece on the mandrel and adjust the mandrel between centres. (use Try

square, slip gauges)

04 Adjust the work piece to the centre of cutter.

05 Set the revolutions, and feed for milling.

06 In the beginning the cutter should have touched slightly on the work piece.

07 Withdraw the work piece out of range of the cutter and lift the milling table by the height

of the tooth depth in the increments of the depth of cut.08 Milling of first tooth space.

09 Withdraw the work piece from the cut and turn the indexing handle by the tooth pitch

& mill next tooth space.

10 Repeat the procedure for next tooth.

OBSERVATIONS

(a) Measure all dimensions (up to second decimal place) on the specimen milled by your


(b) Explain in brief how the required indexing was obtained with the dividing head.

(c) Explain up-milling and down-milling operations. Which one did you use for slot

milling and why?(d) Explain the advantages of using a helical milling cutter.

Gear Milling Setup For The Forming Method: -

Fig. 11: Milling gear with a form cutter

13


14/35

DRILLING AND FITTING

TIME: 4:30 Hours

PART (A)

OBJECTIVE

To study the characteristic features of Drilling machine.






these details (Table A). (Please ensure that the main isolator switch is off andcheck that the machine cannot be inadvertently started. Do not remove guards).

Use the manufacture's handbook for details that cannot be inspected.






c. Drive mechanism for primary (cutting) motion.d. Drive mechanism for secondary (feed) motion.

OBSERVATION



MachineType &

MakeSize

Speed given to Feed given toType of

Surface


Drilling


No.Drilling

Speed Feed

1.

2.

14


15/35

PART (B)

Experiment # 6: To drill, file, as shown in the sketch, ream and tap holes on the mild steel

plate.

Fig. 15: Part to be produced in fitting shop

EQUIPMENT



File all the sides of the mild steel work piece ensuring with a trisquare that all the angle are

90o. Mark the centers of the hole. Mark the circle for the diameter to be drilled. Punch at the

center and at four points on the periphery of the required hole. Drill and ream the holes asrequired. Tap the hole using a set of three taps.

OBSERVATIONS

(a) Measure all dimensions (up to second decimal place) on the specimen made by your


(b) Explain how power is transmitted from drill spindle to drill shank.

(c) Sketch a reamer and show its main features.

(d) Explain why a set of three taps was used.

15


16/35

MEASUREMENT OF PARTS

Measurement is the key on which the whole production is based. Dimensions given on the

job drawing help the operator to produce the job of required size. For every particular

measurement a particular instrument should be used. For example caliper can not substitute

micrometer or rule cannot substitute vernier gauge.

Measuring instruments, tools, equipments & various kinds of gauges are used for

measurement and inspection of the manufacturing or production accuracy of parts and

articles. Measuring instruments may be classified according to the accuracy. According to the

accuracy there are the two types of measuring instrument.

(1) Precision instruments:-

By which instruments we can take measurement within accuracy of 0.01mm or 0.001

inch is known as precision instrument.

(2) Non precision instruments:-

These types of instruments are limited to the measurement of parts to a visible linegraduation on the instrument used, such as a graduated rule or scale. The following principle

measuring instruments are used in the work shop.

(1) Linear measuring/ marking tools

(a) Steel rule /scale

(b) Calliper:- outside, inside and Odd legs

(c) Divider

(d) Depth gauge

(2) Surface measuring tools

(a) Surface plate(b) Angle plate

(c) Try square

(d) Surface gauge

(e) V block

(f) Straight edge

(3) Precision instrument

(a) Micrometer: - out side, inside

(b) Depth micrometer

(c) Varnier calliper

(d) Height gauge

(4) Angular measuring tools

(a) Bevel protractor

(b) Combination set

(c) Sine bar

(5) Gauges

(a) Feeler gauge

(b) Snap gauge

(c) Ring gauge

(d) Thread gauge

(e) Slip gauge

16


17/35

-: Linear Measuring tools :-

(1) Steel rule or scale: - Strip of a hard steel having line engraved at interval of fraction of a

standard unit of the length. It is in different sizes and styles. Scale is usually marked in inches

and centimeter both. Inches divided into 1/8, 1/16, 1/32, 1/64, and in metric system scale

divided into millimeter 1.0 mm and 0.5 mm.

Least count in inch 1/64

Least count in metric system is 0.5mm

Kinds: - (1) Steel rule

(2) Contraction rule

(3) Wooden box scale

(2) Callipers:- Callipers is an indirect measuring tool. It is generally used to transfer or

compare a dimension from one object to another and measurement count with the help of

steel scale.

(a) Outside spring callipers:- Outside spring callipers consists of two legs and both legs bent

inwards. Top of the calliper joint between the two legs is fixed around a leaf spring. The leaf

spring applies force to open the legs at the bottom. An adjusting screw and nut keep the legs

in position to set the point of callipers according to the object.

(b) Inside spring calliper:- Inside calliper is similar to outside calliper. Its points of legs are

bent outwards to make contact with the side of hole and grooves.

(c) Odd leg spring Callipers:- Odd leg caliper is similar to inside calliper. One leg of it is

straight having sharp point and other leg bent inward. It is used for scribing the parallel lines

to the edge of the work and also used for finding the center of a round work.

(1) Calipers are specified by the greatest distance it can be opened between legs.

(2) A sense of feel or touch is necessary to use a caliper successfully.

(d) Divider:- A divider is similar in construction to a caliper except that both legs are straight

with sharp hardened point at the end. It is used for transferring dimensions, scribing circles,

and doing general surface working.

(f) Depth gauge:- The narrow steel rule having a sliding head is clamped with an adjustable

screw at right angle. Depth gauge is used to measure the depth of blind holes, grooves and

slots.

-: Surface measuring and Marking Tools :-

(a) Surface plate: - Surface plates are made in rectangular and square shapes in various sizes.

The flatness of surface plate is highly accurate and smooth. Surface plate is used for marking

out the object with the help of angle plate, surface gauge, try square and v block. Surface

plate must be protected from rust, dust and apply grease and oil time to time after use. It is

made up of cast iron.

For very precision work glass surface plate is used.

17


18/35

(b) Angle plate:- It has two plane surfaces at right angle to each other. This is used in

conjunction with the surface plate for supporting work in perpendicular position. It is made

up of cast iron.

(c) Try square:- Try square is made in two pieces of steel. Blade is perfectly fixed by riveting

in the middle of one end at right angle of beam. It is used for testing the trueness of plain

surface and also used for checking the right angle of object. Some time it is used for surface

making purpose.

(d) Surface gauge:- Surface gauge is made of steel. Bottom of the base is exactly flat for

resting or setting on the face plate. The centre of the bottom is provided with V shaped

groove for resting the block on the round bar. Pole of the surface gauge is adjusted by the

adjusting screw. Marking pin or scriber is clamped with screw in the pole. It is often used for

scribing the line on the object.

(e) V block:- V block is made of Steel with V shaped grooves. It is used for supporting

and setting the round bar in the v groove in horizontal position, so object cannot rotateeasily. V block is used for marking out the round bar.

(f) Straight edge:- Straight edge is commonly used for testing the straightness and flatness of

plane surface. It is made up from carbon steel plate in different sizes.

-: Precision measuring instrument :-

(1) Out side micrometer:- Micrometer is used for measuring the dimension to the outside of

any round or thickness of object. The principle parts of instrument are.

(i) Frame:- U shape flat is known as frame and it is made of cast steel or malleable cast iron.(ii) Hardened Anvil:- A small round piece of hardened steel fixed at the end of frame with

contact to the object.

(iii) Spindle:- The spindle is an actual measuring rod having threads of 0.5mm pitch in metric

system and 40 T.P.I. in English (inch) system.

(iv) Sleeve or Barrel:- Sleeve is measuring scale. It is engraved or graduated in mm or inches.

(v) Thimble:- This is a tubular cover attached with the spindle and moves with spindle. The

beveled edge of tubular is divided into 50 equal parts 0, 5, 10, 15,, so on in mm and 25

equal parts in inch.

(vi) Ratchet:- It is small extension piece of the thimble. This is to prevent and damage of the

instrument.

(vii) Lock Nut or Clamping Ring:- This is used to lock the spindle at any desired setting.

READING OF MICROMETER:

In MM:- The graduations on the barrel are in two parts namely one above the reference line is

graduated in 1mm of intervals. The first and every fifth are long and numbered 5, 10, 15, 25.

The lower graduations are graduated in 1mm intervals but each graduation shall be placed at

the middle of two successive upper graduations to be read 0.5mm. The micrometer screw has

a pitch of 0.5mm and thimble has a scale of 50 divisions round its circumference. Thus on

going through one complete turn of thimble = 0.5mm is opened one division of its scale

50

1

5.0 mm = 0.01mm.

18


19/35

Least count =2

1

50

1 = 0.01

In INCH:- The spindle is the threaded 40 TPI. The sleeve is graduated 40 divisions in one

inch. It means one division on sleeve is 1/40 or 0.25. The thimble is divided in 25 divisions.

If the thimble is rotated one complete rotation it will move 0.025. If it is rotated only one

division out of 25 divisions, it moves 1/25 of 0.025 or 0.001. Every fourth division on the

sleeve is marked 1,2,3,4 and so on up to the length line. These represent 0.100, 0.200,

0.300, 0.400 and so on. Every fifth line of thimble is marked 0, 5, 10, 15, 20, 25. These

represent 0.005, 0.010, 0.015, 0.020, 0.025.

(2) Inside Micrometer:- The inside micrometer is used for measurement of internal hole an

accuracy of 0.01mm or 0.001inch. It is similar to an external micrometer and is used for

measuring holes with a diameter over 50mm or 2 inch. The inside micrometer head has only

13mm or movement. Any size can be obtained by fixing the required size of extension

rod. Extension rods of the following size are in common use, 13, 25, 50, 100, 150, 200 and

600mm and , 1, 2, 4, 6, and 8 in inch.

Reading:- The beveled edge of the thimble is divided into 50 division round the

circumference. One round turn by one thread pitch of 0.5mm, and one division of its scale is

therefore equivalent to a thimble movement of50

15.0 = 0.01 or

2

1

50

1 = 1/100 =

0.01mm.

(3) Depth Micrometer:-

Depth micrometer is used for measuring depth of hole to an accuracy of 0.01mm and

0.001inch.

Parts of depth micrometer:-

1. Ratchet stop 2. Thimble 3. Sleeve

4. Locking ring 5. Head 6. Spindle

The principle of measuring is similar to an external micrometer. Each depth micrometer is

supplied with three interchangeable spindles.

(4) Vernier Height Gauge:- The vernier height gauge consists of a vertical scale fixed on a

heavy base. The vertical scale carries a sliding jaw containing the vernier and a sliding clamp

for making the fine adjustment. There is a flat scriber on the sliding jaw for marking the lines.

It is very useful for direct marking and it saves lot of time in transferring the measurement bymeans of surface gauge. The measurements are read in the same way as in the vernier

calipers.

(5) Vernier Calipers:- The vernier calipers is a precision instrument which can measure up to

1/1000 of an inch and 0.02 or 0.01 in metric system. A vernier scale is the name given to any

scale making use of the difference between two scales. Beam or main scale carries the fixed

graduations. It has two measuring jaw fixed and adjustable vernier head having a vernier

scale. The sliding vernier scale or vernier head can be locked to the main scale by the knurled

screw attached to the vernier.

19


20/35

Reading:- One division of main scale =

"

40

1

Now 25 division on vernier scale = 24 division of the main scale or say

"

4024 .

One division on vernier scale =25

1

40

24 =

1000

24

Difference =1000

24

40

1 =

1000

2425=

"

1000

1

Metric system:- One division of main scale =2

1mm

25 division on vernier scale = 24 division of main scale or say2

24

One division on vernier scale =25

1

2

24 =

50

24

Difference =50

24

2

1 =

50

2425=50

1mm.

VERNIER GEAR- TOOTH CLIPERIt is used for measuring the chordal thickness of gear tooth of pitch circle of gear. The verniar

tooth caliper consists of two vernier calipers perpendicular to each.

The horizontal vernier caliper which measures the tooth thickness is similar to an out side

vernier caliper whereas the vertical version caliper is adjusted for measuring the distance

from the top of a tooth (or addendum circle) to the pitch circle of a gear. The table which

gives these distance and chordal tooth thickness for gear of different diameter pitches and

different number of teeth are available.

-: Angular measuring tools :-

(1) Bevel Protractor:- This is also called vernier bevel protractor. It can measure an angledirectly up to an accuracy of 5 minutes. The protractor disc is graduated in degree over an arc

of 1800, reading 00 to 900 way. Any angle can be measured by setting the stock at the

particular angle on the disc. The blade can slide both ways.

Reading:- The vernier scale in bevel protractor has 12 division both to right and left, to the 0

line. These 12 divisions are equal to 23 degree on the protractor dial.

1 division on protractor dial = 10

12 division on vernier scale = 23 division on the protractor

1 division on vernier scale =12

23

difference =12

232 =

12

2324=12

1or say 5 minutes.

20


21/35

(2) Combination Set:- The combination set is combined with square head, bevel protractor

and a center head. These heads are fitted in the steel rule having a groove. The square head is

used as a tiny square and bevel protractor for checking the angle. The center head is used for

finding the center on the end of round work.

(3) Sine Bar:- Sine bar is an indirect measuring instrument. It is used for measuring an angle.

Sine bars are used in conjunction with slip gauges for setting of angle. It is a flat of metal

stepped or lapped on both the ends. Two roller are fixed in each lapped with a screw. The

sine bar is specified by the distance between the centers of two rollers.

A 100 mm sine bar is very common

( )sin=Hypotenuse

larPerpendicu

-: Gauges :-

(1) Pitch Gauge or Screw Pitch Gauges:- These are steel strips hardened with various blade.The blades are fixed in a pocket for opening and closing like knife. These blades are having

one end teeth to the various pitches of the specific threads. These gauges are made in British,

American and metric thread size. The pitch or number of threads per inch is stamped on the

every blade.

(2) Feeler Gauge:- They are made in set of leaf and fixed in the metal pocket for opening and

closing. The thickness of the blade is stamped on every leaf. These are used for checking the

clearance between two mating parts

(3) Snap Gauge:- These are also known as Go and not Go. They are used for checking

diameters, lengths, and thickness of the parts. The snap gauges are made in fix and adjustablesize stamped on the gauge.

(4) Ring Gauge:- Ring Gauges are used for testing the external dimension of shafts and

cylindrical parts.

(5) Thread Gauges:- Threads are checked with thread gauges. For checking internal threads

plug thread gauges are used, while checking for external threads ring thread gauges are used.

(6) Slip Gauges:- Slip gauges are rectangular blocks of steel. The surfaces of slip gauges are

highly polished. Slip gauges are made in sets. In English measurement there are five sets

containing 81, 49, 41, 35 and 28 pieces. For general purpose a 49 pieces set is used. These areused for precise measurement of parts and for verifying measuring tools such as micrometers

and various limit gauges.

21


22/35

INTRODUCTION TO WELDING PROCESSES

TIME: 4.30 Hours

PART(A)

OBJECTIVE

To study and observe the welding methods through demonstration and practice (Arc and Gas)

Background

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 otheruses. 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: arc welding,

gas welding and brazing.

WELDING PROCESSES

Welding is a process in which two materials, usually metals, are 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 nopressure 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. In many processes the contaminants are removed byfluxing agents.

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.

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

22


23/35

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. There are so many types of the basic arc welding process in the market such as

shielded metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc

welding (GTAW), submerged arc welding (SAW).

5.

Fig.16: The basic circuit for an arc welding

Fig. 17: Schematic diagram of shielded metal arc welding (SMAW)

GAS WELDING

Gas welding usually refers to oxyacetylene welding or, as the name implies, the

burning of acetylene, the fuel gas, with the addition of oxygen to create a high-temperature

flame. The flame temperature normally obtained with 2 parts oxygen to 1 part of acetylene

is about 5850oF (3232oC). The gases are fed through the torch on a 1:1 ratio with the

remaining 1 parts of oxygen coming from the surrounding air. The chemical reaction maybe shown as

3Fe + 2O2 Fe3O4 + heat

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

of a gas flame. A filler rod is used to feed molten material in the gap at the joint region and

establish a firm weld.

Oxyacetylene Flame

Three distinct flame variations are produced with an oxyacetylene gas mixture,

reducing or carburizing, neutral and oxidizing. The acetylene flame is long and bushy. As the

oxygen is turned on, the long flame reduces in size and a feathery inner cone appears,

23


24/35

producing a reducing flame. When the oxygen proportion is further adjusted, the feathery,

white cone disappears and a rounded inner cone and outer envelope indicate a neutral flame.

The length of the luminous inner cone is usually between 1/16 and 5/8 (1.57 and 15.87 mm)

long. If more oxygen is turned on, the flame as a whole grows smaller and the inner cone is

reduced in size to produce an oxidizing flame. All three flames are shown in Fig. 18.

Fig. 18: Three types of oxyacetylene flames

Each of the three flames may be used as follows:

Carburizing flame may to used to advantage in welding high-carbon steels, for hard-facing

operation, and for welding such nonferrous alloys as nickel and Monel. It is also used in

silver- brazing operations. In this operation, only the intermediate and outer flames are used

so that a low temperature soaking heat will be imparted to the parts being joined by silversolder. If a carburizing flame is used in welding steel, the excess carbon will enter the metal,

causing porosity in solidified metal.

Neutral flame is used for most welding operation.

Oxidizing flame is used for fusion welding of brass and bronze; however, the flame is only

slightly oxidizing. An oxidizing flame used on steel will cause the metal to foam and spark.

24


25/35

PART(B)

Experiment # 7: To prepare a butt joint with mild steel strip using MMAW technique.

Fig. 19: Joining the M.S. plates using arc welding

EQUIPMENT AND MATERIALS

Welding unit, MS Electrode, mild steel flats (150*100*10 mm), Wire Brush, Tongs etc.

PROCEDURE

(i) Clean the mild steel flats to be joined by wire brush

(ii) Arrange the flat pieces properly providing the gap for full penetration for buttjoint (gap 1/2 thickness of flats).

(iii) Practice striking of arc, speed and arc length control

(iv) Strike the arc and make tacks at the both ends to hold the metal pieces together

during the welding process

(v) Lay beads along the joint maintaining proper speed and arc length (Speed 100-150

mm/min). Clean the welded zone and submit.

Report the following

1. Precautions to be taken during various arc welding processes.

2. What is the electrode coating and what its function.

3. Give the common arc welding defects and their reasons.

4. Limitations of arc welding.

25


26/35

Experiment # 8: To prepare a Lap joint with mild steel strip using oxyacetylene welding

technique.

Fig. 20: Joining the M.S. plates using gas welding

Equipment & materials

Gas welding set, gas-welding wire, fluxes, mild steel strips, wire brush, tongs etc.

PROCEDURE

1. Clean the mild steel strip removing the oxide layer and flatten it. Keep the metal strip

in lap position.2. Tack at the two ends.

3. Deposit filler metal at the joint maintaining proper speed and feed. Clean the joint and

submit


1. Nature of flame used in gas welding.

2. Composition of the filler rod used in gas welding.

3. Composition of flux used in and its role.

4. Precautions to be taken during Gas welding.

5. Advantage and limitations of Gas welding.

26


27/35

SHEET METAL FORMING

TIME: 4.30 Hours

PART(A)

OBJECTIVE

To study and observe the sheet metal forming process.

Background

Many products are manufactured from sheet metal involving combination of processes such

as shearing, bending, deep drawing, spinning etc. In all these operations, some plastic

deformation of the metal is involved. They are essentially cold working operations.

BENDING

Bending is a very important process in the sheet metal forming by which metal can be

plastically deformed according to the requirement. Bending generally refers to deformation

about one axis only. It is a flexible process. Air bending is one of the bending process in

which the punch touches the work piece and the work piece does not bottom in the lower

cavity. When the punch is released, the work piece return back a little and ends up which less

bend then that on the punch. This is called spring back. Spring back depends on the material,

thickness, grain and temper. Bottoming and coining are the other popular bending process.

Demonstration (Self secured sheet metal joints)

(a) Internal grooved joint

Mark out portions of given sheets near edges to be joined with a marker (Fig. 21.1a)

Fold the sheets at edges in the portion marked, first at right angles to the plane of the sheet

(Fig. 21.lb) and then at 180o to the plane (Fig. 21.lc)

Insert one folded sheet into the other (Fig. 21.ld)

Groove the seam using grooving die (Fig. 21.1e)

(b) Double grooved joint

Fold sheets after making them as per the instructions given (Fig. 21.2a)

Cut a piece of sheet (called strap) of required width

Strap width = (4x size of marked edges) + (4 x thickness of sheet)Close the edges of the strap slightly as shown in Fig. 21.2(b)

Slip the strap on the bent edges of the sheets after bringing them together (Fig. 21.2c)

(c) Knocked-up joint

Fold one sheet and close edges slightly (Fig. 21.3a)

Bend one sheet to form a right angle band (Fig. 21.3b)

Slip the second sheet in the folded one (Fig. 21.3c)

Close the right angled sheet using a mallet (Fig. 21.3d)

27


28/35

21.1 21.2 21.3

Fig. 21: Sheet metal joints

PART(B)

Experiment # 9: To prepare a funnel using the concept of development of surfaces as shown

in the figure.

Fig. 22: Sheet Metal Funnel

28


29/35

Equipment & material

Mallet, hand shear, bench shear, grooving and riveting tool, metal sheet.

Procedure

Draw the elevation on full scale

Complete the cone by extending the lines A and G

Choose a point O and draw curves with O as a center, and OA and OX as radii

Draw the vertical line O3, meeting the internal curve at D, and external curve at 3

Starting from D mark lengths DC, CB, BA, DE, EF and FG, each equal to ml/6

Again starting from 3 mark length 3-2, 2-1, 1-0, 3-4, 4-5 and 5-56, each equal to nd/6. (D and

d are major and minor diameters)

Draw another curve with O as a center and OX +5 mm as radius.

Joint AO and G6 and extend it to cut the outer curve at points H and I, respectively.

Provide a margin of 5 mm on one side, and 10 mm on another side for joint.

Cut out the required portion and form the conical portion.

Make the bottom half of the funnel.


1. Precautions to be taken during sheet metal working.

2. Report the spring back during the bending operation of given metal sheet.

3. Draw the sketches showing the principle of the development of the job as shown in the

sheet metal forming demonstration.

4. What are the machines used in the shearing and bending operation.

29


30/35

INSPECTION OF PARTS

TIME: 2.15 Hours

PART(A)

OBJECTIVE

To study different non destructive methods for inspecting flaws in the welding joints.

Background (WELD INSPECTION)

Weld inspection methods can be broadly divided into two groups:

(i) Nondestructive testing (NDT) and,

(ii) Destructive testing.

Nondestructive Testing (NDT )

Nondestructive testing includes visual examination, liquid penetrant, magnetic

particle, eddy current, ultrasonic, radiography, acoustic emission, thermal and optical

methods.

Visual InspectionAn experienced welder or inspector can detect most of the weld defects by careful

examination. The following defects can be observed: undercut, overlap, surface checks,

cracks slag inclusions penetration, and the extent of reinforcement. Some of these defects are

shown in Fig. 23.

Fig. 23: Some welding defects that can be checked visually

Liquid penetrant

The liquid penetrant method involves flooding the surface with a light oil like

penetrant solution that is drawn into the surface discontinuities by capillary action. After the

excess liquid has been removed from surface, a thin coating of absorbent material is appliedto draw the traces of penetrant from the defects to the surface for observation. Brightly

colored dyes of fluorescent materials are added to the penetrant solutions to make the traces

more visible.

Magnetic particle Inspection

Magnetic particle inspection is based on the principle that ferromagnetic materials,

when magnetized, will have distorted magnetic fields in which there are material flaws and

that these anomalies can be clearly shown with the application of magnetic particles. (Fig. 24)

The magnetic filed can be set up by passing an electric current through all or a portion of the

part. The current may be passed through the part or through a conductor in close proximity tothe part. To be effective, the direction of the induced filed should be almost perpendicular to

the expected flaw. Either ac or dc can be used to generate the magnetic filed. Magnetization

30


31/35

is better with ac for surface discontinuities, while dc is used to locate subsurface

discontinuities or nonmetallic inclusions.

Fig. 24: Magnetic-particle inspection

Eddy-current testing

When electrically conductive material is subjected to an alternating magnetic field,

small circulating electric currents are generated in the material. These eddy-currents are

affected by variation in conductivity, magnetic permeability, mass, and homogeneity of the

host material. Conditions that affect these characteristics can be sensed by measuring the

eddy current response of the part.

Ultrasonic Inspection

Ultrasonic inspection consists of sending a high frequency vibration (beyond 20

kHz) through a component and observing what happens when the beam hits a

discontinuity or a change in density. The altered ultrasonic signal can be used to detect

flows with in the material, to measure thickness from one side and to characterize

metallurgical structure.

The sending transducer transforms a voltage burst in to ultrasonic vibration. The transducer is

coupled to the work piece by a liquid medium such as water. A receiving transducer converts

the received ultrasonic wave into a corresponding electrical signal. With appropriate

instrumentation, the same transducer alternately serves both functions in a pitch-catch mode.The signals are sent through the part, and the time intervals that elapse between the initial

pulse and the arrival of the various echoes are displayed on an oscilloscope screen. A flaw is

recognized by the relative position and amplitude of the echo. Where contact directly above

the part is impractical, an angle beam is used.

Radiography

Radiography is essentially a shadow pattern created when certain types of radiation

penetrate an object and are differentially absorbed depending on variations of thickness,

density, or chemical composition of the material. The shadowgraph is commonly registered

on a photographic film to provide a permanent record.

Three types of penetrating radiations are presently used for industrial radiography: X-rays,

gamma rays, and neutron beams.

Acoustic-emission Monitoring:

Engineering materials undergoing stress or plastic deformation emit sound. The

acoustic emission is in the form of short bursts or train of fast impulses in the ultrasonic

range. These acoustic emissions can be related to the physical integrity of the material or

structure in which they are generated and the monitoring of these events permits detection

and location of flaws as well as prediction of impending failure. The pulse rate and amplitude

of acoustic emission bursts are usually very high compared to most natural or artificial noises

and therefore it is possible to isolate the significant signals by careful measurement of

emission rates and amplitudes.

31


32/35

PART (B)

Experiment # 10: To inspect the defects in the welding done in experiment no. 7 and in the

given specimens using pulse echo method.

1. Introducing Einstein-II TFT

Einstein-II TFT is a portable, compact, light in weight and user friendly Digital Ultrasonic

Flaw Detector. Einstein-II TFT has COLOR LCD display, it provides wide viewing angle

and allows fast scanning speed. Fully charged battery gives continuous working of eight

hours and charging time is just 3 to 4 hours. Trace pattern can be directly printed out on

conventional PC printer having serial port for interface or can be transferred to PC via RS232

Serial port for storage of data.

2. How an Ultrasonic Flaw detector Works

Einstein-II TFT is a single channel Ultrasonic testing instrument used for the inspection of

homogeneous material for the presence of inclusions, porosity and other discontinuities thatcould affect the performance of material and components. It can also be used for thickness

gauging of homogeneous material, requiring access from only one side of the test piece. High

frequency sound (Ultrasonic sound) waves are introduced into the test material/part from a

transducer/probe that is usually coupled to the test piece by water or other suitable coupling

liquid. The transducer converts electric signals to Ultrasound and vice versa. A short burst of

Ultrasound is introduced into test material so some or all of the energy is reflected by

discontinuities. The reflection of the ultrasound energy is a function of the ratio between

the acoustic impedance of the discontinuity and the base material. The greater the impedance

ratio the more sound energy will be reflected. The principal of Ultrasonic testing is shown

in figure1. It shows the ultrasonic energy generated in the test piece and resultant instrument

display. Thickness gauging with Einstein-II TFT operates on the principal of the time-of-flight measurement. This principal utilizes the precise timing of the transit time of a short

burst of ultrasound energy, through a material under test. The ultrasound waves travel to the

far side of the test piece and reflect back to the transducer/probe and a measurement is

obtained.

Basically three type of transducer/probe is available for different types of applications:

1> Straight beam Probe (Normal probe)

2> TR probe (Dual crystal probe)

3> Angle beam Probe

1> Straight beam Probe: This probe introduces ultrasound normal to the test piece surfaceutilizing longitudinal or compression waves. Normal beam probe is used mostly for flaw

detection and thickness gauging (refer figure 1.)

32


33/35

2> TR probe: This probe contains separate transmitting and receiving elements as

showing in figure 2 usually mounted on delay lines. This design improves near

surface resolution by separating the initial pulse from the received echoes. TR probe

is suitable for the thickness gauging of pitting and corrosion and also for better surface

resolution.

3> Angle Beam Probe: This probe introduces ultrasound at angle to the surface of the testpiece. In most angle beam probe, the wave energy is mode converted from a

longitudinal wave to a shear wave by the refraction principal. This probe is suitable for

inspection of the welds. The reason for this is its ability to position the

transducer/probe away from the weld bead yet propagate energy into the weld zone.

Another reason to use angle beam testing on the welds is to position the sound beam more

normal to the expected discontinuities since the flaw in welds are usually perpendicular

to the test piece (except porosity). Figure 3 shows the principal of angled beam weld testing.

3. Parts and Controls of Einstein-II TFT

Fig. 25: Parts and controls of Einstein-II TFT

33

1

2

3

4

5 6 7 8

9

10

11

12

13

1415

20

1716 1918


34/35

Report the following:

1. On the basis of observations, discuss the type of defect in each of the given samples.

2. Compare the result obtained in both the samples.

3. After testing the welded sample piece what conclusions will you draw.

4. Report of possibility of concluding false result.

Experiment # 11: To inspect the cracks in welding of the given specimen by magnetic

particle inspection.

Introduction

Magnetic Particle Inspection (MPI) is a Non-Destructive Testing (NDT) method used for

defect detection. MPI is fast and relatively easy to apply, and part surface preparation is notas critical as it is for some other surface NDT methods (Ex. LPI). These characteristics make

MPI one of the most widely utilized nondestructive testing methods.

MPI uses magnetic fields and small magnetic particles (i.e.iron filings) to detect flaws in

components. The only requirement from an inspectability standpoint is that the component

being inspected must be made of a ferromagnetic material such as iron, nickel, cobalt, or

some of their alloys. Ferromagnetic materials are materials that can be magnetized to a level

that will allow the inspection to be effective.

The method is used to inspect a variety of product forms including castings, forgings, and

weldments. Many different industries use magnetic particle inspection for determining acomponent's fitness-for-use. Some examples of industries that use magnetic particle

inspection are the structural steel, automotive, petrochemical, power generation, and

aerospace industries. Underwater inspection is another area where magnetic particle

inspection may be used to test items such as offshore structures and underwater pipelines.

Electromagnets

Today, most of the equipment used to create

the magnetic field used in MPI is based on

electromagnetism. That is, using an electrical

current to produce the magnetic field. Anelectromagnetic yoke is a very common piece

of equipment that is used to establish a

magnetic field. It is basically made by

wrapping an electrical coil around a piece of

soft ferromagneticsteel. A switch is included

in the electrical circuit so that the current and,

therefore, the magnetic field can be turned on

and off. They can be powered with alternating

current from a wall socket or by direct current

from a battery pack. This type of magnet generates a very strong magnetic field in a local

area where the poles of the magnet touch the part being inspected.

34


35/35

Dry Particle Inspection

In this magnetic particle testing technique, dry particles are

dusted onto the surface of the test object as the item is

magnetized. Dry particle inspection is well suited for the

inspections conducted on rough surfaces. When an

electromagnetic yoke is used, the AC or half wave DC current

creates a pulsating magnetic field that provides mobility to the

powder. Dry particle inspection is also used to detect shallow

subsurface cracks. Dry particles with half wave DC is the best

approach when inspecting for lack of root penetration in welds of

thin materials. Half wave DC with prods and dry particles is

commonly used when inspecting large castings for hot tears and

cracks.

PROCEDURE

Prepare the part surface - the surface should be relatively clean but this is not as critical as

it is with liquid penetrant inspection. The surface must be free of grease, oil or other moisture

that could keep particles from moving freely. A thin layer of paint, rust or scale will reduce

test sensitivity but can sometimes be left in place with adequate results. Specifications often

allow up to 0.003 inch (0.076 mm) of a nonconductive coating (such as paint) and 0.001 inch

max (0.025 mm) of a ferromagnetic coating (such as nickel) to be left on the surface. Any

loose dirt, paint, rust or scale must be removed.

Apply the magnetizing force - Use permanent magnets, an electromagnetic yoke, prods, a

coil or other means to establish the necessary magnetic flux.

Dust on the dry magnetic particles - Dust on a light layer of magnetic particles.

Gently blow off the excess powder - With the magnetizing force still applied, remove the

excess powder from the surface with a few gentle puffs of dry air. The force of the air needs

to be strong enough to remove the excess particles but not strong enough to dislodge particles

held by a magnetic flux leakage field.

Terminate the magnetizing force - If the magnetic flux is being generated with an

electromagnet or an electromagnetic field, the magnetizing force should be terminated. If

permanent magnets are being used, they can be left in place.

Inspect for indications - Look for areas where the magnetic particles are clustered.

Report the following:

1. No. of cracks found on the surface of the given specimen.

2. Report of possibility of concluding false result.

Documents

Laboratory_manual Mn 201