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UNIVERSITI TEKNIKAL MALAYSIA MELAKA INVESTIGATION OF PLATE WELDING QUALITY BY ROBOT WELDING USING NONDESTRUCTIVE TECHNIQUE This report submitted in accordance with requirement of the Universiti Teknikal Malaysia Melaka (UTeM) for Bachelor Degree of Manufacturing Engineering (Manufacturing Process) with Honours. by HARYATIE BINTI SAMSURI FACULTY OF MANUFACTURING ENGINEERING 2008

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Page 1: UNIVERSITI TEKNIKAL MALAYSIA MELAKAdigitalcollection.utem.edu.my/6317/1/Investigation... · walaupun dikendalikan oleh robot kimpalan. Kecacatan yang terjadi dipengaruhi oleh beberapa

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

INVESTIGATION OF PLATE WELDING QUALITY BY ROBOT

WELDING USING NONDESTRUCTIVE TECHNIQUE

This report submitted in accordance with requirement of the Universiti Teknikal

Malaysia Melaka (UTeM) for Bachelor Degree of Manufacturing Engineering

(Manufacturing Process) with Honours.

by

HARYATIE BINTI SAMSURI

FACULTY OF MANUFACTURING ENGINEERING

2008

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ABSTRACT

Joining between two metal plates by using the welding process is not produced a high

quality of final product but it has some discontinuities and defects that appear inside the

welds. These defects are actually caused from some factor either environment factor or

setting by operator before operator conducted the welding operation. For your

information, the defects still has either using manual welding or using robot welding.

But the percentage of defects that’s found on welds after using robots welding are less

comparing with manual welding. So, the performance and its result done by robots

welding and manual welding can learn together. The welding quality, defects, skill of

the welder and position done by welder also can relate with this parameter of the causes

of welding defects. This is because the parameters effecting in welding quality is the

main factor of discontinuities caused by inadequate or careless application of proper

welding technologies or by poor welder training. From this major discontinuities that

affect weld quality are solved with a best method for controlling those parameters

factors. The internal defects or an external defect that can detect by human eyes was

tested by nondestructive testing method. But this projects, the testing methods used is

ultrasonic testing which is the classical test method based on measurements by using

ultrasonic oscillations for detection of flaws in different material. The ultrasonic testing

by give reproducible test results within narrow tolerances. Not all influences have to be

regarded by the operator. In many cases of the influences can be neglected without

exceeding the permitted measurement tolerances.

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ABSTRAK

Hasil cantuman antara dua kepingan logam dengan menggunakan proses kimpalan tidak

semestinya menghasilkan proses kimpalan yang terbaik tetapi mempunyai beberapa

kecacatan akibat daripada beberapa faktor sama ada faktor persekitaran ataupun faktor

akibat daripada operator itu sendiri. Oleh hal yang demikian, kecacatan tetap ada

walaupun dikendalikan oleh robot kimpalan. Kecacatan yang terjadi dipengaruhi oleh

beberapa faktor sama ada pengelarasan pada mesin robot kimpalan yang diselaraskan

oleh operator seperti jumlah arus elektrik yang diselaraskan, frekuensi, kelajuan

menimpal, jenis elektrod, jenis kepingan logam dan sebagainya. Oleh hal yang

demikian, kecacatan yang tersembunyi yang tidak ditemui akan dikesan atau diperiksa

dengan mata kasar akan dikenalpasti melalui “ujian nondestructive”. Ujian ini terbahagi

kepada beberapa ujian kecil yang lain. Salah satu daripada ujian kecil yang telah

digunakan ialah ujian ultrasonik. Ujian ini majoriti diaplikasikan di serata industri di

negara ini. Ujian ultrasonik boleh dikendalikan dengan cara yang lebih senang iaitu

sample telah ditentukan dengan alat pengukuran yang efektif dan tepat. Sampel ujian

akan ditetapkan dengan membetulkan sistem alat pengukuran untuk mengelakkan

daripada terjadinya ralat semasa sampel diuji.

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DEDICATION

I dedicate this work to my special family, my special friend in gratitude and all my

loving friends because of her/ his patience and understanding support in all my

endeavors and special thanks to them for their love.

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ACKNOWLEDGEMENT

Alhamdullillah with God permission already able complete this PSM project. Wishes

express honestly gratitude to all the people who has given support during the period of

the project progress. First and foremost, a special thanks to University Technical

Malaysia Malacca especially for Prof. Dr. Mohd Razali bin Muhamad as Coordinator of

PSM project, and Mr. Sivarao a/l Subramonian as assistant Coordinator of PSM project

who constructs this programme for students to do the PSM project. Also thanks for Dr.

Mohd Rizal bin Salleh as PSM Supervisor for giving their full support, a lot of valuable

information, and guidance. Next, special appreciation goes to all friend that involve and

to beloved parents because give their full support and encouragement in doing this

project. May all of the person stated here and another person who is in some way

involved and has helped during my project time in campus and during my report writing,

be blessed and have a peace of mind in running their everyday life until the end of their

life.

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TABLE OF CONTENT

Abstract i

Abstrak ii

Dedication iii

Acknowledgement iv

Table of Content v

List of Table ix

List of Figures xi

List of Abbreviations xiii

1. INTRODUCTION

1.1 Welding 1

1.1.1 Development of Modern Welding Processes 1

1.2 Problem Statement 2

1.3 Objective 2

1.4 Scope of Research 3

2. LITERATURE REVIEW

2.1 Fusion Welding Processes 4

2.1.1 History and Development 4

2.1.2 Oxyfuel Gas Welding 4

2.1.3 Arc Welding Processes of Non- Consumable Electrode 5

2.1.4 Arc Welding Processes of Consumable Electrode 7

2.1.5 Gas Metal Arc Welding 7

2.1.6 Electrodes for Arc Welding 8

2.1.7 Welding Parameter 8

2.1.8 The Weld Joint 9

2.1.9 Weld Quality 10

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2.2 Robot Welding 12

2.2.1 Definition 12

2.2.2 Synchromotion 12

2.2.3 Utilizing Features and Function 14

2.2.4 Simultaneous Control 15

2.2.5 Advantage and disadvantage of robot welding 17

2.3 Nondestructive Techniques (NDT) 18

2.3.1 Definition 18

2.3.2 Types of NDT Technique 19

2.3.3 Ultrasonic testing 20

2.3.4 Advantages and Disadvantage of Ultrasonic Testing 21

2.3.5 Reflection Characteristic of Sound Waves When

Striking Discontinuities 22

2.3.6 Improvement 23

3. METHODOLOGY

3.1 Sample Preparation and Gathering 24

3.2 Raw Material 24

3.2.1 Mild Steel 25

3.2.2 Stainless steel 26

3.2.3 Differentiation between mild steel and stainless steel 27

3.3 Filler Wire 29

3.4 Joint Type 29

3.5 Research Procedure 30

3.6 Welding Method 31

3.7 Parameter Selection 31

3.7.1 Constant Parameter 31

3.7.2 Variable parameter 32

3.8 Robot Welding 33

3.8.1 Description 33

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3.8.2 Standard Operation of Robot Welding (SOP) 34

3.8.3 Standard Operation ON and OFF System 36

3.8.4 Coding 36

3.9 Testing Method 37

3.9.1 Equipment 38

3.10 Testing Technique 41

3.10.1 Calibration of the Test Sample 42

3.10.2 Standardized of Test Sample 42

3.10.3 Performance of Test Sample 42

3.10.4 Interpretation of Result 42

3.11 Contact Testing 43

3.11.1 General 43

3.12.2 Why ultrasonic testing 44

3.11.3 Comparison between ultrasonic testing and radiographic testing 45

3.11.4 Basic Method 46

3.11.5 Testing system 47

3.11.6 Parameter consideration 49

3.11.7 Couplant 52

3.11.8 Evaluating the defect 53

3.11.9 Technique define crack from floating card 54

3.11.10 Procedure 55

4. RESULT

4.1 Welding Result 56

4.1.1 Mild Steel 56

4.1.2 Stainless Steel 58

4.2 Ultrasonic Testing Result 60

4.2.1 Mild Steel 60

4.2.2 Stainless Steel 63

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5. DISCUSSION

5.1 Mild Steel 67

5.2 Stainless Steel 72

5.3 Propose the appropriate method of controlling the

parameters for better welding quality 75

6. CONCLUSION

6.1 Conclusion 78

REFERENCES 80

APPENDICES A

Gannt Chart for Project Activities for PSM 1 83

Gannt Chart for Project Activities for PSM 2 84

APPENDICES B

Figure i

Figure ii

Figure iii

Figure iv

Figure v

Figure vi

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LIST OF TABLE

3. METHODOLOGY

3.1 Chemical composition of mild steel filler wire 26

[Sources: Barry M. Patchett, 1998]

3.2 Chemical composition of stainless steel of filler wire 27

[Sources: Barry M. Patchett, 1998]

3.3 Description of robot welding 33

[Sources: Manual Lab Machine Shop]

4. RESULT

Welding Result (Mild Steel) 56

4.1 Variable welding current according the reference value 56

4.2 Variable welding voltage according the reference value 57

4.3 Variable welding speed according the reference value 57

Welding Result (Stainless Steel) 58

4.4 Variable welding current according the reference value 58

4.5 Variable welding voltage according the reference value 58

4.6 Variable welding speed according the reference value 59

Ultrasonic Testing Result (Mild Steel) 60

4.7 Variable welding current 60

4.8 Variable welding voltage 61

4.9 Variable welding speed 62

Ultrasonic Testing Result (Stainless Steel) 63

4.10 Variable welding current 63

4.11 Variable welding voltage 64

4.12 Variable welding speed 65

5. DISCUSSION

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Mild Steel 67

5.1 Welding current and its defect 67

5.2 Welding current and its defect 67

5.3 Welding voltage and its defect 69

5.4 Welding voltage and its defect 69

5.5 Welding speed and its defect 70

5.6 Welding speed and its defect 70

Stainless Steel 72

5.7 Welding current and its defect 72

5.8 Welding current and its defect 72

5.9 Welding voltage and its defect 73

5.10 Welding voltage and its defect 73

5.11 Welding speed and its defect 74

5.12 Welding speed and its defect 74

6. CONCLUSION

6.1 House of quality between mild steel and stainless steel 78

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LIST OF FIGURES

1. INTRODUCTION

2. LITERATURE REVIEW

2.1 Basic types of oxyacetylene flames 5

(Sources:Kalpakjian Schmid, 2001)

2.2 (a) Gas tungsten arc welding process formerly tungsten 6

inert gas welding (TIG welding). (b) Equipment TIG operations

(Sources:Kalpakjian Schmid, 2001)

2.3 The shielded metal arc welding process 7

(Sources:Kalpakjian Schmid, 2001)

2.4 The characteristics of a typical fusion weld zone 9

(Sources:Kalpakjian Schmid, 2001)

2.5 Various discontinuities in fusion welds 11

(Sources:Kalpakjian Schmid, 2001)

2.6 Robot welding 13

3. METHODOLOGY

3.1 Groove shape on the plate 25

3.2 Stainless steel plate 306L 25

3.3 Mild steel plate 26

3.4 Welding angle 32

3.5 Typical ultrasonic contact test displaying 39

(Source: Jimmy Gan, 2006)

3.6 Sweep delay adjustment 40

(Source: Jimmy Gan, 2006)

3.7 Sound beam reflection 43

(Source: Jimmy Gan, 2006)

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3.8 Typical contact test discontinuity indication 44

(Source: Jimmy Gan, 2006)

3.9 Schematic of pulse echo flaw detector 48

(Source: Galvery W, 2007)

3.10 Full set of ultrasonic tester machine 50

3.11 CTR screen 50

3.12 Calibration block 51

3.13 Highest echo signal 52

3.14 Lowest echo signal 52

3.15 First highest of echo signal 53

3.16 Second highest of echo signal 53

3.17 Weld size 54

5. DISCUSSION

5.1 Crack or flaw in and around a weld 66

(Source: Galvery W, 2007)

5.2 Slag inclusions 68

(Source: Galvery W, 2007)

5.3 Weld produces when use lowest speed; 10cm/min 71

5.4 Comparison of sizing accuracy in standard deviation 76

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LIST OF ABBREVIATION

A or AMP - Ampere

AC - Alternating Current

AE or AET - Alternate Ending

AS - Alternate Start

BP - Beam Path

C - Circular

DC - Direct Current

ECT - Eddy Current Testing

EXT INPUT - External Input

GMAW - Gas Metal Arc Welding

HAZ - Heat Affected Zone

HC - Harmonious circle

HL - Harmonious Line

HLO - Harmonious Line Orientation

HLX - Interpolation in Simultaneous Control

HO - Harmonious Circle Orientation

HP - Harmonious Position

IP - Initial Pulses

LX - Uniform Interpolation

MIG Welding - Gas Shielded Arc Welding

NDT - Nondestructive Testing

OAW - Oxyacetylene Gas Welding

OFW - Oxyfuel Gas Welding

P - Positioning

PZT - Zirconate Titanate

RT - Radiographic Testing

TIG Welding - Gas Tungsten Arc Welding

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Sa - Sound Path

SD - Surface Distance

SOP - Standard Operation of Robot Welding

UT - Ultrasonic Testing

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CHAPTER 1

INTRODUCTION

This chapter provides a general background of the project. It briefly describes the

general discussion of joining processes and focus on the subject being discussed easily.

It also explains the problem statements, objectives of the study, and scope of the

research.

1.1 Welding

Welding is one type joining process involve the partial melting and fusion of the joint

between two workpiece. Fusion welding is defined as melting together and coalescing

materials by means of heat [Kalpakjian et. al, 2006].

Joining process is carried out in the various ways. The mechanical joining method is

derived from metalworking processes. The solid techniques are based on the adhesion

and deformation [Gourd, 1998].

1.1.1 Development of Modern Welding Processes

The discovery of acetylene by combining with oxygen was produced a flame that used

for welding and cutting. It became known as oxyacetylene welding. The application of

heat generate from an electric arc between carbons electrodes is one basic for the

shielded arc welding process [Gourd, 1998].

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1.2 Problem statement

Today we can see the welding are generally used in manual or using the automated

robot. So, both of two categories of welding methods are totally different. For the

manual welding, these processes use a power supply created by welder to create and

maintain an electric arc between an electrode and the base material to melt metals at the

welding point. They was used either direct (DC) or alternating current (AC), and

consumable or nonconsumable electrodes. The welding region is sometimes protected

by some type of inert or semi inert gas, known as a shielding gas and filler material is

sometimes used as well. Meanwhile for robots welding, are the parameters was already

setting by operator with its controller.

Then, the welding process done by robots as the robots is the welder. But for manual

welding, the welder is human. So the final product after welding process are difference

each other because both of them have their own criteria. So from this case, we can know

mostly about the different of performance result done by robots welding and manual

welding. And at the same time the welding quality, defects, skill of the welder and

position done by welder also can relate with this case. This is because the parameters

effecting in welding quality is the main factor of discontinuities caused by inadequate or

careless application of proper welding technologies or by poor welder training. From

this major discontinuities that affect weld quality are solved with a best method for

controlling those parameters factors.

1.3 Objective

The main purpose of this project was listed below.

i. To investigate the performance of plate welding quality and its welding defects.

ii. To identify the parameters effecting the welding quality.

iii. To propose the appropriate method of controlling the parameters for better

welding quality.

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1.4 Scope of research

The scope of study was listed below.

i. To learn how to use the robot welding practically.

ii. To identify the parameters affected on welds.

iii. To perform the joining works on the sample of work piece.

iv. To carry out the testing of nondestructive techniques.

v. To analyze the result obtained from the equipment.

vi. To conclude the discussion discussed based on the result getting from the

experiment.

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CHAPTER 2

LITERATURE REVIEW

This chapter describes the information from many sources that it explains to readers

what has motivated the study by giving definition, identifying the causes and effects,

listing method used, provides historical background, describing the problem faced and

stating the advantages or disadvantages.

2.1 Fusion Welding Processes

2.1.1 History and development

The welding and oxyfuel welding was developed in 1893. Acetylene was discovered in

1836 by Edmund Davy. The automatic welding was introduced in 1920 which is an

electrode wire was fed continuously [Cary et. al, 2005]. Shielded metal arc welding was

developed around 1950 by using a flux coated consumable electrode. The plasma arc

welding was developed in the same year. The electro slag welding was introduced in

1958 and it was followed by an electro gas welding in years of 1961 [Cary et. al, 2005].

2.1.2 Oxyfuel gas welding

Oxyfuel gas welding (OFW) is define as any welding process that uses a fuel gas

combined with oxygen to produce a flame. This flame is the source of the heat that is

used to melt the metals at the joint. The most common gas welding process uses

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acetylene; this process is known as Oxyacetylene Gas Welding (OAW). Figure 2.1 is

showed the three basic types of oxyacetylene flames used in oxyfuel gas welding and

cutting operation [Kalpakjian et. al, 2006].

Figure 2.1: Basic types of oxyacetylene flames (Source: Kalpakjian Schmid, 2001)

i. Flame type

The important factor in oxyfuel gas welding is the proportion of acetylene and

oxygen.

ii. Filler metal

Filler metal is used to supply additional metal to the weld zone during welding. It

suited as filler rod or wire and coated with flux as to check oxidation of the

surfaces of the parts being welded by generating a gaseous shield around the

weld zone.

iii. Pressure gas welding

The welding of two components started with the heating of the interface by

means of a torch using an oxyacetylene gas mixture. The torch was withdrawn

after the interface begins to melt.

2.1.3 Arc welding processes of non- consumable electrode

The direct current used and its polarity as the current flows is important. The selection

based on such factors as the type of electrode, metals to be welded, and depth and width

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of the weld zone. The types of welding techniques stated and listed below [Kalpakjian

et. al, 2006].

Figure 2.2: (a) Gas tungsten arc welding process formerly tungsten inert gas welding (Source: Kalpakjian

Schmid, 2001). (b) Equipment TIG operations (Source: Kalpakjian Schmid, 2001).

i. Gas tungsten arc welding

The filler metal is supplied from a filler wire in gas tungsten arc welding (TIG)

like Figure 2.2 above. It‟s more suitable for thin metal. The tungsten electrode is

not consumed in this operation, so that the arc gap is maintained at a constant

current level. Flux is not used but the filler wire are similar to the metal to

welded.

ii. Plasma arc welding

A concentrated plasma arc is produced and directed towards the weld area in

plasma arc welding. Deep and narrow weld can be made by this process at high

welding speed.

iii. Atomic hydrogen welding

An arc is generating between two tungsten electrodes in a shielding atmosphere

of hydrogen gas. The arc is maintained independently of the workpiece or part

being welded.