Universiti Malaysia Pahang
Universiti Malaysia Pahang
Universiti Malaysia Pahang
INDUSTRY
NOVEMBER 2008
I feel grateful to Allah S.W.T because this project has successfully completed. In
completion this final year project, I was in contact with many people that contributed
toward my understanding and problem solving. In particular, I wish to express my
sincere appreciation to my project supervisor, Ir Haji Nik Mohd Zuki B Nik Mohamad
for his guidance, advice and encouragement. Without his continued support and interest,
this thesis would not have been the same as presented here.
Not forgetting my friends who help me to grow further and influence my project
in order to finish this project. I appreciate very much to them because of the idea and
information given along done this project. I also would like thank to Dr. Kumaran A/L
Kadirgama who act as a co-supervisor and give a support to finish this report.
Last but not least I acknowledge without endless love and relentless support from
my family. All of them, you all have given me the inspirations and encouragement until
these days. This project definitely not exists without full encouragement from them.
ABSTRACT
TITLE i
SUPERVISOR DECLARATION ii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
LIST OF TABLES x
LIST OF FIGURES x
2.1 Introduction
3
2.2 Spot Welding 9
CHAPTER 3 METHODOLOGY
3.1 Introduction 16
3.3 Method 19
4.1 Introduction 25
4.32 Machine 43
4.4 Conclusion 45
CHAPTER 5 CONCLUSION
5.1 Conclusion 46
5.2 Recommendations 47
5.3 Future recommendation 48
REFERENCES 49
APPENDIX 51
LIST OF TABLES
LIST OF FIGURES
LIST OF SYMBOL
% Percentage
LIST OF ABBREVIATION
LIST OF APPENDICES
A Figure 51
CHAPTER 1
INTRODUCTION
In the body assembly there several method were used such as laser weld, tailor
welded blank and spot weld. For this report, spot weld will be taken as the main research
and case study. Resistance spot welding (RSW) is used for the fabrication of sheet metal
assemblies. The process is used extensively for joining low carbon steel components for
the bodies and chassis of automobiles, trucks, trailers, buses, mobile homes, motor
homes and recreational vehicles, and appliances and many other products.
In the body assembly process there are several problem could happen. When this
happen it could stuck the process in assembly line and disturb certain department. The
major problem in the body assembly is spot weld gun and human mistake. Everyday
there are always have problems regarding this two factor such as miss the spot part, dent
or hump, scratch, spatter burr and hole to the body during assembly. For analysis
purpose, this problem will delay the time and production to recover it back. Hence, this
research will help by making the analysis and case study at the body assembly by
proposing a solution to avoid the problem or reduce it from happening.
The aim of this project is to reduce the problem occurs during body assembly
process and decrease the possibility that mistake could happen during work. The aim can
be achieve by objective below:
The scope of this project, more focus on E-class Mercedes car assembly at
Automotive Manufacture Malaysia (AMM) factory at Pekan. Collecting the data have be
done by visited the AMM factory for several time where all the data were recorded for
used in this report. The report cover several scope:
LITERATURE REVIEW
2.1 Introduction
With increased competition in the automobile market, more attention has been
given to managing variations in automobile body assembly processes. Dimensional
variation affects fit quality and functionality. For example, variations in a body-in-white
(BIW) can ultimately cause poor sealing, undue effort required for door closing, water
leaks, excessive wind noise, prolonged time-to-market and added manufacturing costs.
Typically, the automobile body assembly process comprises numerous steps, utilizing
300–500 compliant sheet metal parts, 50–120 assembly stations and 3000–6000 spot
welds. Each step in the process is capable of contributing a degree of variation. Those
variations in turn act on one another to compound distortion in the final BIW. The
complexity of this interaction places severe demands on the existing methods of
simulation, which currently fall far short of satisfaction. (Min Hu, Zhongqin Lina et.al,
2001)
Below is the overall flow chart of how the process in assembly line for body
assembly. All the activity and the process along the line assembly were mention in the
Table 2.0 start from beginning the process until finish. From the chart, process and
information of the car that will assemble can be analyzed.
Table 2.0: Activity Process in Line Assembly
Metal Finish
1. Sanding body surface if
required.
2. Repair body surface if
required
Quality Gate
2.2 Spot Welding
Resistance spot welding (RSW) is used for the fabrication of sheet metal
previous term assemblies. The process next term is used extensively for joining low
carbon steel components for the previous term bodies next term and chassis of
automobiles, trucks, trailers, buses, mobile homes, motor homes and recreational
vehicles, and railroad passenger cars, as well as cabinets, office furniture, appliances and
many other products. High-strength low-alloy steel, stainless steel, nickel-, aluminum-,
titanium and copper alloys are also spot welded commercially.
The major advantages of spot welding are high speed and adaptability for
automation in high-volume and/or high-rate production. Despite these advantages, RSW
suffers from a major problem of inconsistent quality from weld to weld. This problem
results from both the complexity of the basic previous term process next term as well as
from numerous sources of variability, noise, and errors. Any or all of these complicate
automation, reduce weld quality, demand over-welding (i.e., the production of more
welds than are structurally needed, if each were perfect), and drive up production costs.
For this reason, ensuring weld quality has been and remains a major challenge and goal.
( Min Jou, 2003)
Resistance spot welding uses the surface resistance of the materials to be joined
to generate an intense localized heat under pressure with a short passage of a high
current. Use of coated sheet in vehicles for corrosion resistance has presented problems
related to the electrode life. The electrode life may get reduced to 50~500 welds before
maintenance (tip dressing) as against 3000~6000 welds in case of uncoated plain steels.
With introduction of HSLA steels, the need for reliability of weld quality has become
much more demanding. Suitable shop floor quality tests are vitally important. ( Cho, Y.,
and Rhee, S. 2003)
2.2.1 Large Panel with Members and Brackets
In order to make a weld with members and brackets on the large panel, such as
the center floor of the auto body, a large C-type gun is needed to access in the middle of
the panel. Since complicated jig fixtures and clamping devices are located underneath
the panel, it is very hard to teach the robot the right position with proper cycle time -
Fig. 2.2A. Once the single sided RSW system is adopted for this application, fixture and
clamping units can be dramatically reduced -Fig. 2.2B. Thanks to the easy access to the
weld spots, cycle time also can be decreased.
Figure 2.3: Single-sided RSW of a large panel. A - Large C-type gun with jig and
clamping units; and B - single-sided gun with backing plates.
2.2.2 Preassembled Parts
Weld timers provide the ability to monitor each spot weld so that its peak current
level is within predetermined limits. Dynamic resistance principle measuring the
variation of resistance over time during the weld is also used to ensure a higher level of
guaranteed quality. A sophisticated dynamic resistance system may incorporate an
adaptive control feature that varies the weld settings within certain limits to achieve
correct weld quality. The system also includes a weld current stepper function linked to
the counting of welds executed. The parameter limits are established for the specific
application and programmed for control. With capability of microprocessor based
controls, the constant current system could easily be attained for ensuring weld quality.
The weld time variation is unlikely with electronic controls. Welding forces is
applied pneumatically through line supply and hardly require a more rigid control
attained for ensuring weld quality. Tips of electrodes are to be maintained for consistent
current density. Either an individual weld count or an interface with the robot (if used) is
applied to make electrode dressing compulsory after an established number of cycles.
Pneumatic or electrically driven tip dressers shape both electrodes simultaneously to
ensure established geometry and decontaminated condition of the tip surfaces.
For quality of spot welding of automotive body, in addition to accurate panels and
jigs, tightly controlled position, sequence and direction of spot welding as well as
attitude of welding gun are necessary. Spot welding was basically manual operation.
Dedicated multi weld machines are used for high volume production in totally automatic
mode. The application of robots provided the appropriate human solution with much
higher precision in positioning and repeatability as shown Table 2.1.
With increased acceleration and deceleration of robots, spots can be applied at high
rate: a 50 mm step takes less than 0.3 seconds and a 300 mm one can be traversed in
under 0.7 second. Welding robots are generally supplied as a complete system including
gun transformer, air, water and electrical power supply, and all controls.