1 PROCESS CAPABILITY ANALYSIS AT CHAUDRY TEXTILES (MALAYSIA) SDN BHD MOHAMED SALLEHSU BIN KAMARUZAMAN Report submitted in partial fulfilment of the requirements for the award of the degree of Bachelor of Mechanical Engineering FACULTY OF MECHANICAL ENGINEERING UNIVERSITI MALAYSIA PAHANG 14 NOVEMBER 2008
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PROCESS CAPABILITY ANALYSIS AT CHAUDRY TEXTILES (MALAYSIA) SDN BHD
MOHAMED SALLEHSU BIN KAMARUZAMAN
Report submitted in partial fulfilment of the requirementsfor the award of the degree of
Bachelor of Mechanical Engineering
FACULTY OF MECHANICAL ENGINEERINGUNIVERSITI MALAYSIA PAHANG
14 NOVEMBER 2008
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SUPERVISOR’S DECLARATION
We hereby declare that we have checked this report and in our opinion this report is
satisfactory in terms of scope and quality for the award of the degree of Bachelor of
Mechanical Engineering
Signature :
Name of Supervisor : NORAINI BINTI MOHD RAZALI
Position : LECTURER
Date : 11 NOVEMBER 2008
Signature :
Name of Panel : SALWANI BINTI MOHD SALLEH
Position : LECTURER
Date : 11 NOVEMBER 2008
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STUDENT’S DECLARATION
I hereby declare that the work in this report is my own except for quotations and
summaries which have been duly acknowledged. The report has not been accepted for
any degree and is not concurrently submitted for award of other degree.
Signature :
Name : MOHAMED SALLEHSU BIN KAMARUZAMAN
ID Number : MA05087
Date : 11 NOVEMBER 2008
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ACKNOWLEDGEMENTS
It is with a great sense of pleasure that I acknowledge the help and guidance I
have received from a numerous people during the course of my stay at Universiti
Malaysia Pahang. My supervisor Puan Noraini Binti Mohd Razali, enthusiasm and
insight to work on this interesting final year project. I am very much thankful to her for
all their support in conducting and writing up my work.
Moreover, I would like to express my heartfelt and sincere for their priceless
guidance and support during my final year. In addition to being my supervisor, she also
helps me a lot with advices in industries.
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ABSTRACT
Process capability analysis ensures that processes are fit for industry company
specification while reduce the process variation and important in achieving product
quality characteristic. Its indices are to measure the inherent variability of a process and
thus to reflect its performance. The main objective for this research are to predict current
and future capability of the process to produce product within specification in the
company and to investigate the product produced by the company meet the customer’s
specification. This project focuses on Process Capability Analysis that had been applied
in small and medium industry in the organization which includes select critical
parameters, data collection, study on process capability and data evaluation. This project
was successfully done by implementing and applying the capability study to the
company.
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ABSTRAK
Kebolehan menganalisis sesuatu process adalah untuk membantu sesebuah syarikat
industri mengetahui samada proses-proses terbabit yang mengeluar atau menghasilkan
produk adalah berada dalam spesifikasi yang ditetapkan. Pada masa yang sama dapat
mengurangkan proses variasi dan yang paling penting adalah untuk mencapai karakter
produk yang berkualiti dihasilkan. Dalam menentukan sesuatu proses tersebut
menghasilkan produk yang baik dan tepat, Cp dan Cpk dari kebolehan menganalisis
sesuatu proses telah digunakan. Selain itu, Cp dan Cpk ini juga dapat membantu sesebuah
industri mengetahui proses variasi yang berlaku. Objektif utama projek ini adalah untuk
menentukan kebolehan proses menghasilkan produk pada masa sekarang dan kebolehan
proses menghasilkan produk pada masa akan datang samada ia mengikuti spesifikasi
syarikat industri tersebut atau tidak. Objektif kedua ialah mengenal pasti samada produk
yang dihasilkan adalah mengikuti spesifikasi pelanggan atau tidak. Projek ini
mengfokuskan kebolehan menganalisis sesuatu proses yang diamalkan dalam organisasi
industri kecil dan sederhana yang meliputi pemilihan proses yang paling kritikal,
mengumpul data, menganalisis kebolehan proses tersebut dan data penilaian. Projek ini
telah berjaya dilaksanakan dan kebolehan menganalisis sesuatu proses telah digunakan
oleh syarikat industri tersebut.
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TABLE OF CONTENTS
Page
SUPERVISOR’S DECLARATION ii
STUDENT’S DECLARATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF SYMBOLS xii
CHAPTER 1 INTRODUCTION
1.1 Introduction of the research 1
1.2 Project Background 2
1.3 Problem Statement 2
1.4 Project Objectives 3
1.5 Project Scope 3
CHAPTER 2 LITERATURE REVIEW
2.1 Related Articles 4
2.2 Process Capability Indices 8
2.3 Six Sigma versus Three Sigma 12
2.4 Statistical Process Control 14
2.5 Control Chart Interpretation
2.5.1 In-Control and Out-Of-Control Processes 17
2.5.2 Points beyond the Control Limits 19
2.5.3 Zone Tests: Setting the Zones and Zone A 19
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2.5.4 Zone Tests: Zones B and C 21
2.5.5 Test for Stratification 22
2.5.6 Test for mixtures 23
2.5.7 Rule of Seven Tests 24
CHAPTER 3 METHODOLOGY
3.1 Methodology
3.1.1 Start 26
3.1.2 Literature Review 26
3.1.3 Process Selection 26
3.1.4 Select Critical Parameters 27
3.1.5 Determine the Inspection Frequency 28
3.1.6 Control Chart/Statistical Process Control 28
3.1.7 Calculate the Control Limits 29
3.1.8 In-Control 30
3.1.9 Cp and Cpk Values 30
3.1.10 Conclusion 31
3.1.11 Recommendation/Future Works 31
3.1.12 End 31
CHAPTER 4 ANALYSIS AND DISCUSSION
4.1 Analysis on X-Bar and R Chart 32
4.2 Tests for Process Normality 32
4.3 X-Bar And R Chart Analysis
4.3.1 MINITAB Analysis on X-Bar and R Chart 37
4.3.2 Manual X-Bar and R Chart Analysis 38
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4.4 Interpretation of X-Bar And R Chart 40
4.5 Process Capability Analysis
4.5.1 MINITAB Analysis on Cp and Cpk 41
4.5.2 Manual Analysis on Cp and Cpk 43
4.6 Causes Of The Process Mean Shifted Or Process Variation 44
4.7 The Cause-Effect of 4m
4.7.1 Men 46
4.7.2 Machine 47
4.7.3 Environment 48
4.7.4 Maintenance 48
4.8 The Needs for Well-Controlled Printing Process 49
4.9 Chapter Summary 49
CHAPTER 5 CONCLUSION AND RECOMMENDATIONS
5.1 Conclusions 50
5.2 Recommendation/Future Works 51
REFERENCES 53
APPENDICES
A Machineries 54
B Process Layout 61
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LIST OF TABLES
Table No.
2.1 Summarized of four article
2.2 Equivalent Cp value and capability to produce
non-conformance product
2.3 Equivalent Cpk value, quality level and DPMO
4.1 Printed fabric data in meter length
4.2 Factor for computing central lines and control limits
Page
5
11
12
33
35
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LIST OF FIGURES
Figure No. Page
2.1 Equation of Cp 8
2.2 Equation of Cp with upper and lower specification and 9
process standard deviation
2.3 Equation of Cpk 9
2.4 Equation of Cpk with upper and lower and two-sided 10
specification limit
2.5 Cpk with one-sided specification limit
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2.6 Example of process capability chart 11
2.7 Sigma levels and equivalent conformance rates 14
2.8 In-control control chart 18
2.9 Points beyond the control limits 19
2.10 Setting the zones 20
2.11 Zone A 21
2.12 Zones B and C 21
2.13 Zone C 22
2.14 Test for stratification 22
2.15 Test for mixtures 23
2.16 Rules of seven tests 24
3.1 Printing process flow 26
3.2 Flatbed screen printing machine 27
3.3 Control charts 28
4.1 Printing machine operating 34
4.2 Length of printed fabric versus frequency histogram 36
4.3 MINITAB analysis on X-bar and R charts 38
4.4 MINITAB analysis on Cp and Cpk 41
4.5 Fishbone diagram for process variation 45
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LIST OF SYMBOLS
Cp Capability index
Cpk Capability index
6σ 6-sigma
USL Upper specification limit
LSL Lower specification limit
Cpu Single sided process spread capability index
Cpl Single sided process spread capability index
μ Process mean
σ2 Process variance
x i Average of ith subgroup
x Average of the subgroup averages
σ x Population standard deviation for the subgroup averages
R Average of the ranges
Ri Individual range value for the sample
A2 Approximation factor used to calculate control limits
m Number of subgroups
σR Population standard deviation of the subgroup ranges
D4 Approximation factor used to calculate range chart
D3 Approximation factor used to calculate range chart
d2 Approximation factor for calculating within subgroup
T Tolerance
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CHAPTER 1
INTRODUCTION
1.1 INTRODUCTION OF RESEARCH
Small and medium industry is an enterprise with full-time employees not
exceeding 150 or with annual sales turnover not exceeding RM25 million [1]. The
definition of Process Capability Analysis is how likely a product is going to meet the
design specification. The following scenarios highlight the significance of the process
capability studies. Suppose the customers of a major manufacturing company have
entered into a contract with the manufacturer regarding the production of some specialty
parts. This time, the customers have asked for part tolerances so fine that the company’s
machine may not be capable of producing to that level of precision. The process
capability analysis consists of selecting quality characteristics in the process, collecting
data from the process output and calculating process capability indices. The Cp should
be at least 1.33 in order for the process to be considered capable. Cpk indicates whether it
is capable and how well-centered the process is. If the process is not capable, the
improvement steps or make an enhancement to the process must be taken by the
company [2].
A process capability analysis is made of four things that is the actual process,
performance information, action on the process, and action on the output. Using this
information, it is possible to determine the proportion of output that will be acceptable.
To conduct a process capability study, the following six steps are needed. Firstly,
determine the process is in a state of statistical control (via X-Bar and R charts is the
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most common way to do this). Then, establish the definition of capable (on Cpk scale, it
is generally > 1). Moreover, establish the process is in control (as defined in the section
on control charting). Next on the list, construct a histogram to determine if the process is
normal. If the process is normal, continue with the process. After that, determine the
mean and standard deviation of the process. Lastly, capability calculations according to
the index that is used are to be made [3].
In this case study, Chaudry Textiles (Malaysia) Sdn Bhd had been chosen as a
small and medium industry to collaborate in this research which is situated in Pengkalan
Chepa, Kelantan. Chaudry Textiles (Malaysia) is actually a manufacturer and marketer
of cotton fabric production. The company had produced many products such as cotton,