Thesis QUALITY IMPROVEMENT OF STYROFOAM SHELLS BY USING DMAIC PROCESS AT LONG HUEI VIETNAM

ABSTRACT The purpose of this paper is to explore the benefits of implementing six sigma and its methodology DMAIC (Define, Measure, Analyze, Improve, Control) to improve the quality of Styrofoam shells. The Styrofoam department had the highest defect rate of 0.91% compared with other production departments. The goals of this project are, therefore, to identify quality problems of Styrofoam shells in the Styrofoam department, to find out the root causes of quality problems and to suggest and implement solutions and then evaluate their effectiveness. In the Define phase, Pareto analysis shows that there is one defect that occur most in the Styrofoam shell production process, namely structure. In measure phase, a process capability study was conducted to measure current process performance before improvement. The result of the current process study was incapable and thus it needed to be improved. By applying Fishbone diagram and Brainstorming method in the improve phase, the author determined the root causes of structure defect: Difficulty in controlling the extent of bead expansion; Deterioration of expanded bead pump hoses; Conveyor belts do not have protective barriers; Poor layout; The quality of the raw beads is not uniform in each batch; High humidity. In improve phase, the solutions recommended correspondingly with the 6 root causes: Making expansion density table; Make pump hoses maintenance plans; Install weld fences for conveyor belts; Divide the storage area into two areas, the area for raw beads and the area for the expanded beads; Strictly control the raw bead batches; Using dehumidifiers. However, after conducting an effortandeffect analysis, the improvement using dehumidifiers was removed due to its low effect and high effort. After a process improvement has been done, the result is an increase of 0.4 sigma level from 3.77 to 4.17, which results in the expected cost savings of VND 264,939,140 per year. In the Control phase, a control plan was established to control and monitor the process to sustain improvement efforts.

HCMC UNIVERSITY OF TECHNOLOGYSCHOOL OF INDUSTRIAL MANAGEMENT

BACHELOR THESIS

QUALITY IMPROVEMENT OF STYROFOAMSHELLS BY USING DMAIC PROCESS

AT LONG HUEI VIETNAM

HCM City, 06/2021

No.: 15-CLC

HCMC UNIVERSITY OF TECHNOLOGYSCHOOL OF INDUSTRIAL MANAGEMENT

BACHELOR THESIS

QUALITY IMPROVEMENT OF STYROFOAMSHELLS BY USING DMAIC PROCESS

AT LONG HUEI VIETNAM

-Independence – Freedom – Happiness

-Ref No : _/BKĐT

DEPARTMENT: Production & Operations Management

STUDY SPECIALIZATION: Business Administration

1 Title:

QUALITY IMPROVEMENT OF STYROFOAM SHELLS BY USING DMAIC PROCESS AT LONG HUEI VIETNAM

2 Thesis assignment (requirements for content and data):

- Identify the quality problems of Styrofoam shells in Styrofoam department - Find out the root causes of quality problems

- Suggest and implement solutions and the evaluate their effectiveness

(Sign and write full name)

FOR SCHOOL/ DEPARTMENT

Approved by (initially examined by): Department :

Date of defense: Total mark: Stored at:

On the very outset of this thesis, I would like to extend my sincere thanks towards all the individuals who have helped me to complete this research successfully.

First of all, I would like to express my sincere gratitude to the lecturers in the School of Industrial Management – Ho Chi Minh city University of Technology for teaching, guiding and transmitting the foundational knowledge to me In particular, I would like to thank my supervisor Dr for her patience, motivation, enthusiasm, and immense knowledge Her guidance helped me in all the time of research and writing of this thesis.

Besides, I would like to thank Long Huei (Vietnam) Co Ltd for offering me the internship opportunities and precious guidance Thanks to this chance, I learnt, improved myself and met many wonderful people and professionals who led me through this internship period I would like to express my deepest gratitude to Ms Tseng, Zhi-Ying, Quality Manager, who in spite of being busy with her duties, took time out to hear, guide, and keep me on the correct path I would also like to thank the employees of Quality Department for helping me and enthusiastically answering my questions.

It is a great pleasure for me to acknowledge and express my gratitude to my classmates and my best friends for their understanding, unstinted support and endless encouragement during completion of this thesis

I perceive as this opportunity as the big milestone in my career development I hope to continue cooperation with all of those wonderful people in the future.

Ho Chi Minh City, June 28, 2021 Author,

The purpose of this paper is to explore the benefits of implementing six sigma and its methodology- DMAIC (Define, Measure, Analyze, Improve, Control) to improve the quality of Styrofoam shells The Styrofoam department had the highest defect rate of 0.91% compared with other production departments The goals of this project are, therefore, to identify quality problems of Styrofoam shells in the Styrofoam department, to find out the root causes of quality problems and to suggest and implement solutions and then evaluate their effectiveness In the Define phase, Pareto analysis shows that there is one defect that occur most in the Styrofoam shell production process, namely structure In measure phase, a process capability study was conducted to measure current process performance before improvement The result of the current process study was incapable and thus it needed to be improved By applying Fishbone diagram and Brainstorming method in the improve phase, the author determined the root causes of structure defect: Difficulty in controlling the extent of bead expansion; Deterioration of expanded bead pump hoses; Conveyor belts do not have protective barriers; Poor layout; The quality of the raw beads is not uniform in each batch; High humidity In improve phase, the solutions recommended correspondingly with the 6 root causes: Making expansion density table; Make pump hoses maintenance plans; Install weld fences for conveyor belts; Divide the storage area into two areas, the area for raw beads and the area for the expanded beads; Strictly control the raw bead batches; Using dehumidifiers However, after conducting an effort-and-effect analysis, the improvement using dehumidifiers was removed due to its low effect and high effort After a process improvement has been done, the result is an increase of 0.4 sigma level from 3.77 to 4.17, which results in the expected cost savings of VND 264,939,140 per year In the Control phase, a control plan was established to control and monitor the process to sustain improvement efforts

CHAPTER 1: GENERAL INTRODUCTION 1

1.1 RATIONALE OF THE STUDY 1

1.2 OBJECTIVES OF THE STUDY 2

1.3 SCOPE OF THE STUDY 2

1.4 PRACTICAL MEANING OF THE RESEARCH 3

1.5 THE STRUCTURE OF THE STUDY 3

CHAPTER 2: LITERATURE REVIEW AND METHODOLOGY 5

2.1 LITERATURE REVIEW 5

2.1.1 Six Sigma Overviews 5

2.1.2 Methodology of Six Sigma – DMAIC 11

2.1.3 Six Sigma and Kaizen - Differences 15

2.1.4 Statistical Quality Control Tools 17

3.5.2 Function and Responsibility of Each Department 39

3.6 OVERVIEW OF THE PRODUCTS OF LONG HUEI COMPANY 42

3.6.1 Definition of Helmets 42

3.6.2 Main Elements of A Common Helmet 42

3.6.3 Production Process: 43

3.6.4 The Helmet Type of Long Huei Company 45

3.7 SUPPLY CHAIN OF LONG HUEI VIETNAM COMPANY 45

CHAPTER 4: QUALITY IMPROVEMENT OF STYROFOAM SHELLS BYUSING DMAIC PROCESS 50

4.1 BRIEF INTRODUCTION OF STYROFOAM DEPARTMENT 50

4.1.1 Impact Absorbing Liner Introduction 50

4.1.2 Stages of Manufacturing Styrofoam Shells 50

4.2 DMAIC PROCESS 52

Figure 2 1 What is Six Sigma? 5

Figure 2 2 Illustration of levels of Six Sigma 8

Figure 2 3 DMAIC process 11

Figure 2 4 An activity flowchart of a changeover operation for a production line 18

Figure 2 5 A cross-functional flowchart for acquiring new equipment 19

Figure 2 6 Use of an Office Copy Machine 19

Figure 2 7 An example of a classification check sheet 20

Figure 2 8 An example of a defect location check sheet 20

Figure 2 9 An example of a frequency check sheets 21

Figure 2 10 An example of measurement scale check sheets 21

Figure 2 11 An example of check lists 22

Figure 2 12 An example of histograms 23

Figure 2 13 An example of a pareto diagram 24

Figure 2 14 An illustration of a scatter diagram 24

Figure 2 15 An example of a fishbone diagram 25

Figure 2 16 Types of control charts 26

Figure 2 17 The interface of Minitab software 26

Figure 2 18 Thesis implementation method 28

Y Figure 3 1 Factory 3 in Kim Huy Industrial Park 32

Figure 3 2 Logo of ZEUS brand 34

Figure 3 3 Logo of Andes brand 35

Figure 3 4 Logo of Cromo brand 36

Figure 3 5 Logo of SUNDA brand 36

Figure 3 6 Organizational Structure 38

Figure 3 7 Parts of a common helmet 42

Figure 3 8 Production process of a finished helmet 44

Figure 3 9 Types of helmets at Long Huei Vietnam 45

Figure 3 10 Supply chain of Long Huei Vietnam 45

Figure 3 11 Promotion helmets for Coca cola business customer 47

Figure 3 12 A helmet of Bulldog brand 47

Figure 4 1 Impact Absorbing liner (Styrofoam shell) 50

Figure 4 2 A steam chamber 50

Figure 4 3 The polystyrene pellets before and after expansion 51

Figure 4 4 A foam moulding machine 51

Figure 4 5 DMAIC Process 52

Figure 4 7 The cut-through of a standard full-face helmet 53

Figure 4 8 Pareto chart of defect rate of Styrofoam department 55

Figure 4 9 %Contribution analysis result on Minitab 57

Figure 4 10 %Study Var analysis result on Minitab 57

Figure 4 11 Xbar-S chart of Initial process (before improvement) 59

Figure 4 12 Testing Normality Assumption for Initial Process 60

Figure 4 13 Capability study for initial process (before improvement) 61

Figure 4 14 Cause-and-effect diagram related to the structure defects 62

Figure 4 15 Measurement of A material 64

Figure 4 16 Maintenance schedule for foam machine 65

Figure 4 17 Daily checklist for foam moulding machine 66

Figure 4 18 Illustrations of the ejecting shell position before and after improved implementation 66

Figure 4 19 Before and after improved implementation layout of the storage area 67

Figure 4 20 How a dehumidifier works 69

Figure 4 21 An industrial dehumidifier 69

Figure 4 22 Effort & Effect Analysis 70

Figure 4 23 Process Capability Before & After Improvement 70

Figure 5 1 Sample of problem-proposing card 76

LIST OF TABL

Table 2 2 Method of Data Collection 30

Y Table 4 1 SIPOC diagram 54

Table 4 2 Project charter 55

Table 4 3 Standards for MSA assessment 58

Table 4 4 Description of structure defect 58

Table 4 5 Data collection plan of structure defect 59

Table 4 6 Structure defects at Styrofoam department – current and expected states 61

Table 4 7 Expansion density table 64

Table 4 8 Data collection plan of monthly inspection report 68

Table 4 9 Expected cost for implementing improvement 6 69

Table 4 10 Financial savings from the improvement project 71

Table 4 11 Control plan 71

Table 5 1 Effectiveness measure of the improvement project 75

QC Quality Control

Solutions (the software for statistics analysis)

CHAPTER 1: GENERAL INTRODUCTION

1.1 RATIONALE OF THE STUDY

Manufacturing companies, which were heavily affected by the US-China trade war in the past two years, were once again affected adversely when the COVID-19 pandemic spread around the world The decline in consumer demand for goods increases the challenges for manufacturing companies As a result, factories across countries in many continents, from the US to Europe and Asia, all faced a decline in output in the past months The competition between businesses is getting fiercer, companies are under greater pressure when customers become more and more demanding, requiring manufacturers to constantly improve in design, materials and technology to improve productivity and quality to meet orders with less and less time and cheaper prices Long Huei Vietnam is the top-quality helmet manufacturer in Vietnam with nearly 20 years of experience in manufacturing motorcycle helmets, owning many famous helmet brands in Vietnam as well as abroad such as Andes, Sunda, Zeus, Cromo, etc However, at present, the company is facing fierce competition from domestic and global enterprises, especially cheap fake helmets from China.

Based on the data of the defect rates in six production departments (see more detail in Appendix A), the Styrofoam department possessed the highest defect rate (0.91%) and the lowest sigma level (3.86) compared with other production departments (Figure

Figure 1 1 Defect rate and sigma level of production departments

This means that the quality problem of Styrofoam department has become more serious and this department has given priority to improvement project In addition, currently there is not any project that has been undertaken with the aim of improving the ratio of the semi-finished product effectively and maintaining the stability of the Styrofoam department

The DMAIC approach is the most common approach in Lean Six Sigma implementation However, DMAIC is not exclusive to Six Sigma and can be used as a framework for applications to improve, optimize production management, improve product quality, reduce costs, improve overall efficiency process or increase productivity DMAIC is a five-step systematic approach that allows quality analysts to efficiently manage process improvement projects DMAIC stands for Define, Measure, Analyse, Improve, Control There are a large number of successful examples of implementing DMAIC in improving the quality and cost minimization such as Motorola, General Electric, Honeywell, Sony, Caterpillar, Ford, LG, etc

Based on practical factors of problem, scale, current conditions, the DMAIC cycle incorporates quality tools which is the most suitable method to improve the quality of Styrofoam shells at Styrofoam department As a result, the author decides to conduct

the topic “Quality Improvement of Styrofoam Shells by Using DMAIC Process atLong Huei Vietnam”.

1.2 OBJECTIVES OF THE STUDY

 Identify quality problems of Styrofoam shells in the Styrofoam department  Find out the root causes of quality problems

 Suggest and implement solutions and then evaluate their effectiveness

1.3 SCOPE OF THE STUDY

 Research location: Styrofoam department, factory 3, Long Huei (Vietnam) limited company, Kim Huy industrial park, Binh Duong

 Research product: Styrofoam shells

 Research duration: 11/02/2020 – 05/31/2021

1.4 PRACTICAL MEANING OF THE RESEARCH

For Long Huei Vietnam company:

- Help the company and all employees understand the benefits that Six Sigma could bring, and improve teamwork efficiency through a DMAIC project

- Identify the problems that are being encountered in the Styrofoam department, and propose some recommended measures to improve the problems and quality control plans.

For the author

- Apply knowledge of Six Sigma and DMAIC process, knowledge about quality management which has been learned into the practice of the company.

- This is also an opportunity to help the author be able to collect, aggregate and analyse data, as well as be able to use the knowledge learned in solving the problems in reality

1.5 THE STRUCTURE OF THE STUDYChapter 1:

In this first chapter, the author will present the reasons for conducting the topic “Quality Improvement of Styrofoam Shells by Using DMAIC Process at Long Huei Vietnam”, along with the goal of the topic and scope of the study The author will also present the practical meanings of the topic for Long Huei Vietnam company and for the author

Chapter 2:

In the second chapter, the author will present relevant theories as the foundation and basis for applied research The author will state the theories of Six Sigma methods, DMAIC method, the differences between Six Sigma and Kaizen and theories of statistical quality control tools and Minitab software in helping to synthesize, analyze and offer comprehensive solutions

Chapter 3:

In this chapter, the author will introduce about Long Huei Vietnam Co., Ltd with the information such as the field of production, organizational structure, products, customers, supply chain and SWOT analysis This will be the foundation for understand the problem the company is facing.

Chapter 4:

In this chapter, the author will introduce briefly about research product and apply five steps of DMAIC method from defining the problem, measuring the problem, identifying the cause of the problem, implementing and verifying the solution to maintaining the solution

Chapter 5:

In the last chapter of this thesis, the author will summarize the main results of the topic, and propose more recommendations for the company The author will also point out the lessons learned in the implementing process of DMAIC method and the limitations of the topic

CHAPTER 2: LITERATURE REVIEW ANDMETHODOLOGY

2.1 LITERATURE REVIEW2.1.1 Six Sigma Overviews

2.1.1.1 Definition of Six Sigma

Figure 2 1 What is Six Sigma?

Six Sigma is a systematic methodology for process improvement based on statistics to reduce the error or defect rate that is minimized to 3.4 per million defect possibilities by identify and exclude sources of variation (instability) in manufacturing and business processes In defining defects, Six Sigma focuses on establishment through the deep understanding of customer requirements, and therefore, customer orientation

Six Sigma is not a quality management system, measuring product quality like ISO 9001, or a quality certification system This is a methodology that helps to reduce product defects based on process improvement This means that instead of focusing on checking defects on output products, enterprises should focus on improving production processes and finding out the causes of defects, adjusting appropriately so that defects do not occur.[CITATION Hen00 \l 1066 ]

2.1.1.2 History of Six Sigma

The Six Sigma story originated in the 1980s at Motorola In the year 1983, a prestigious engineer named Bill Smith came up with the conclusion that checking and testing cannot detect all of the product defects, but customers are ones who can discover the defects, and the defect is the cause of the product failure Due to the number of defects in the process was much more than the number of defects from completed product tests, so Smith decided that the best way to solve the problem of product defects is process improvement to minimize or eliminate the possibility of defects He sets standards 6 Sigma – 3.4 defects per million opportunities or 99.99997%, almost perfect and turns this principle into a method This Six Sigma method has been promoted at Motorola and helped it save more than $16 billion over 15 years Later on, a large number of companies, ranging from General Electric, Honeywell, Sony, Caterpillar to Johnson Controls, have applied Six Sigma and gained remarkable benefits [CITATION Pan00 \l 1066 ]

Although Six Sigma is not widely common in Vietnam, a few foreign-invested companies such as SONION, American Standard, Ford, LG and Samsung have applied the Six Sigma program.

Ford Vietnam is one of successful examples of applying Six Sigma in improving process In 2000, Ford Vietnam Company started implementing Six Sigma in 200 projects to improve processes in all areas of production and business As a result, in 2007, Ford saved 1.2 million USD and the customer satisfaction index reached over 90% per year.

One of Ford Vietnam's most successful Six Sigma projects was to reduce the number of imported parts containers in 2005 Waste is identified because the car component

boxes in the containers are still abundant space, Ford arranged and made the most of the available space according to the innovative Six Sigma method Although it is just such a small project, it saved Ford $ 150,000 in 2005 and contributed significantly to increasing profits for the parent company [CITATION JAR20 \l 1033 ]

2.1.1.3 Related Studies

Not only Six Sigma has been universally incorporated into manufacturing and service industries due to the positive influences on quality enhancement and cost reduction but also it has gained much prevalence and acceptance among academic scholars [CITATION Noo12 \l 1066 ] explored the applicability and suitability of the Six Sigma framework for process improvement of IT industries By applying DMAIC process and several statistical quality control tools such as I-MR chart, Fishbone, C&E Matrix, etc., they found out the roots causes that affected the unsatisfaction of customers towards IT Infrastructure factor Thanks to this improvement project, the volume of customer complaints of IT Infrastructure reduced to 75% One of the most critical problems faced by manufacturers nowadays is that they cannot meet the forecasted demand [CITATION Nic \l 1066 ] performed Six Sigma and Lean to create a better process with more reasonable cost that can meet the customer needs The objectives were to reduce process wastes and optimize production process to increase productivity and competitive advantages of the company [CITATION Ada09 \l 1033 ] applied Six Sigma methodology to find out root causes of power errors through a 2-factor experiment and implement actions to reduce defects [CITATION Hsi11 \l 1033 ] successfully applied steps of DMAIC process to reduce the defect rate of egg cakes by 70% in the food industry At the beginning of the project, the rate of defects was 0.45%, and after implementing improvement actions during six months, the figure decreased to below 0.141%

2.1.1.4 Levels of Six Sigma

Six Sigma is a methodology of statistical process improvement with the aim of minimizing error or defect rates to the most perfect extent by identifying and eliminating root causes in processes Six Sigma method focuses on identifying and understanding thoroughly customer requirements; hence it is very customer oriented.

“Sigma” means the standard deviation in the statistics; thus, Six Sigma means six standard deviation units:

Table 2 1 Levels of Six Sigma

Sigma % Accuracy % Defects opportunity (DPMO)Defects per million

Figure 2 2 Illustration of levels of Six Sigma

The goal of Six Sigma is only 3.4 defects per million possibilities of failure In other words, it is about 99,99966% perfect.[CITATION Mek06 \l 1033 ]

2.1.1.5 Advantages and Disadvantages of Six Sigma

There are various benefits that Six Sigma brings to organizations[CITATION Jij04 \l 1033 ]:

 Six Sigma strategy places a clear focus obtaining measurable and quantifiable financial returns to the bottom-line of a company There is no Six Sigma project approved if the bottom-line influence has been clearly identified and defined  Six Sigma strategy puts an unprecedented importance on strong and passionate

leadership and the support needed for its successful deployment.

 Method of solving the problem of Six Sigma integrates the human factors (cultural change, customer focus, belt system infrastructure, etc.) and process elements (process management, statistical analysis of process data, measurement system analysis, etc.) of improvement.

 Six Sigma methodology utilizes tools and techniques for improve problems in business process in a sequential and disciplined approach Each tool and technique within the Six Sigma methodology have a vital role in success and failure of a Six Sigma project.

 Six Sigma creates an infrastructure of champions, master black belts (MBBs), black belts (BBs) and blue belts (GBs) that lead, deploy and implement the approach

 In Six Sigma, it is considered that data and decision making based on facts and data are more important than assumptions and hunches This methodology forces people to conduct measurement.

 Six Sigma utilizes the concept of statistical thinking and encourage the application of trustworthy statistical tools and techniques for reducing defects through process variability reduction methods (e.g., statistical process control and design of experiments).

Disadvantages:

Like any other quality improvement methodologies, Six Sigma has its own limitations, including[CITATION Jij04 \l 1033 ]:

 First of all, find out quality data is the challenge of any Six Sigma projects’ analysist, especially in process where no data is available to begin with This is

the reason why sometimes the measure phase could account for the largest proportion of the project duration

 In addition, the statistical definition of the Six Sigma is 3.4 defects or failures per million chances In service processes, a defect can be identified as anything that does not satisfy the customer needs or expectations It would be illogical if it is assumed that all defects are equally good when we calculate the sigma capacity level of one process For example, a mistake in the hospital could be a false admission procedure, lacking training required by an employee, employee's misconduct, lacks of goodwill to help patients when they have specific queries, etc

 The calculation of the error rates or the defect rates is based on assumptions about normality The defect rate calculation for unusual situations have not been properly solved in the current literature of Six Sigma

 Non-standardized procedures in the black and green belt certification process is another limitation This means not all the black belts or the green belts are equally capable Research has shown that the skills and expertise developed by black belts are inconsistent among companies and are dependent to a great extent on certifying body

 The start-up expense to institutionalize Six Sigma into the corporate culture can be a significant investment This specific feature would discourage many small and medium size organizations from the introduction, development and implementation of Six Sigma strategy

 Six Sigma could easily become a bureaucratic exercise if the concentrate is on things as the number of trained black belts and green belts, number of projects completed, etc instead of ultimate savings.

2.1.2 Methodology of Six Sigma – DMAIC

Six Sigma philosophy is based on DMAIC process, including Define, Measure, Analyse, Improve and Control, in which specific tools used to convert a practical problem into statistics, building solutions based on statistical model and finally into a

practical solution The problem is stated in the Define phase The performance is estimated in the measure phase to find the current sigma level Analyse phase is used to find the causes of poor performance Recommended solutions are suggested and implemented in the improve phase The last phase is control that is used to control the system and adjustment of the process management for sustainable improvements [CITATION BRA13 \l 1033 ]

Figure 2 3 DMAIC process

2.1.2.1 Define (D)

The first phase in the DMAIC cycle is define First, to identify the obvious problem that the business is facing Then to determine the main cause of the problem Once the main cause of the business has been identified, analysing the following three issues to focus on problem improvement[CITATION BRA13 \l 1033 ]:

- Voice of Business (VOB): to analyse what businesses need and want, what problems are facing and what needs to be done to meet customer needs,

- Voice of Customer (VOC): to analyse to understand what customers need in the company's products and services such as guaranteed product quality, fastest delivery time along with the lowest cost.

- Voice of Process (VOP): to analyse of the existing state of products and production machines, whether to meet customer needs and business expectations or not.

In addition, the researchers need to identify the improvement project, to define the project goals, and to form a general summary for the project using tools such as

SIPOC, Project Charter, CTQ driver tree, Pareto diagram, etc [CITATION Pet07 \l 1033 ]

- SIPOC (Supplier - Input - Process - Output - Customer): determine the source of raw materials, step by step input process, specific parameters, steps in the production process as well as output and quality criteria that the customers expect.[CITATION Shi09 \l 1033 ]

- Project Charter: set up a summary of the project to shape the direction as well as provide key information about the project From there, it helps to facilitate research and application of improvements [CITATION Ben19 \l 1033 ]

- CTQ driver tree: critical to quality Transform the voice of the customer to internal process measurement [CITATION Six20 \l 1033 ]

- Pareto chart: determine the level of output impact of each product on the enterprise and to select the type of product to improve according to its influence on the economic efficiency of the organization

2.1.2.2 Measure (M)

Objective of measure phase is to measure the performance of work related to the company's production activities and process current state, and translate the problem in to a measurable parameter [CITATION BRA13 \l 1033 ]

Take measurements of the equipment's performance, quality and downtime From there, measure the production capacity of the equipment in the process as well as calculate the process capability indicators by applying tools such as[CITATION Pet07 \l 1033 ]:

 Measure variables: gather all variables that could be measured  Prioritisation: Choose the most significant variables to be measured

 Data collection plan: Distinguish variable type, set up measurement system, define operational definition.

 Sampling: Perform measurement of historic and/or current data.

 Pareto chart: Determine the level of output impact of each product on the enterprise and to select the type of product to improve according to its influence on the economic efficiency of the organization.

 Histograms: Represent frequency of data based on the column type It simply describes the data without losing any of the statistical information of the data  Process capability: Calculate initial process capability and process sigma.

2.1.2.3 Analyse (A)

Objective of this phase analyse aims to determine the causes of poor performance - Analyse the influence of input and output factors.

- Analyse the current process capacity.

- Identify causes and factors that have high influence level - Analyse the correlation of input and output factors

-Verify by using statistical tools [CITATION BRA13 \l 1033 ] The tools are applied, including[CITATION Pet07 \l 1033 ]:

- Cause and effect analysis: or called Ishikawa diagram (‘fishbone diagram’) to find and list all root causes to problems.

- Regression analysis: find transfer functions by applying regression of measured data.

- Hypothesis testing: test connections/ relations between input and output variables by testing of hypotheses.

- DoE: stands for Design of Experiments Used to get linear and nonlinear transfer functions between inputs and outputs.

- 5 Whys analysis: use the 5 Whys tool by asking “why” questions to find the root cause of the problem.

- Brainstorming: a method used to develop many creative answers to a problem This method works by stating ideas that are focused on the problem, from there, drawing a lot of fundamental answers to it.

2.1.2.4 Improve (I)

The objective of this improve phase is to design and implement innovative solutions to eliminate inefficiencies In this step, if necessary, we have to conduct some field checks to assess whether the improvement results have achieved the intended result in the first phase [CITATION BRA13 \l 1033 ]

There are several tools applied in this phase, including: [CITATION Pet07 \l 1033 ]  Cost/Benefit analysis: also known as economic analysis, is an extensive

analysis of financial analysis, used mainly by governments and international agencies to review whether the project or policy increases the welfare of the community or not.

 FMEA: stands for failure modes and effects analysis Risk evaluation of the solution and of the implementation of the solution

 Pilot phase: test run of process improvement with a limited scope  Implementation plan: a plan that includes schedule, responsibility, etc

2.1.2.5 Control (C)

Objective of control phase is to establish standard metrological parameters to maintain results and correct problems as needed, including those problems of the measurement system Complete the measurement system, design the control system, document the process Verify the long-term capacity of the process, determine the post-improvement process capability to evaluate the improvement effect, and to know the capacity of the improvement process to control [CITATION BRA13 \l 1033 ]

Tools are applied in this phase, including[CITATION Pet07 \l 1033 ]:

 Process control chart: distinguish fluctuations caused by special causes that need to be identified, investigated and controlled from inherent random changes in the process.

 Control Plans: set up detailed control plan to ensure problems do not recur by continually monitoring the related processes.

 Evaluation of results: calculate process capability and process sigma of the improved process Compare to targets.

 Key learnings: document key learnings from the project.

2.1.3 Six Sigma and Kaizen - Differences

2.1.3.1 Kaizen Overview

Because the entire world is moving into a competitive space, almost every firm and organization is starting to implement different methodologies for overall management development Many training programs are available to improve existing processes in organizations across the globe Six Sigma and Kaizen are programs that focus on real-world situations that aim to improve consistency in different areas of the business model [CITATION Geo06 \l 1033 ]

Six Sigma has been proven to be an outstanding approach to dealing with product variations and defects Six Sigma mainly depends on statistical analysis to deliver results to customers It aims to eliminate waste and create an error-free business model.

Nevertheless, Kaizen is more than just tools and data collection Kaizen is a Japanese economic term, compounded by the word 改 ("kai") meaning change and the word kai"kai") meaning change and the word ) meaning change and the word 善 ("kai") meaning change and the word zen"kai") meaning change and the word ) meaning better, meaning "kai") meaning change and the word change for the better"kai") meaning change and the word or "kai") meaning change and the word continuous improvement"kai") meaning change and the word In Chinese, Kaizen is pronounced Gansai, which means the action of continuous improvement, bringing mutual benefits rather than individual benefits [CITATION Geo06 \l 1033 ]

In Japan, Kaizen has a history of more than 50 years and Toyota was the first company to implement Kaizen In the past, Kaizen was mainly applied in manufacturing companies such as Toyota, Canon, Honda, etc After that, Kaizen is widely applied in all companies in many different fields and today, most Japanese companies are implementing Kaizen This philosophy is not limited to manufacturing, but can also be applied to the service industry, retail business and even any course of study [CITATION Geo06 \l 1033 ] In this part, the key differences between Kaizen and Six Sigma will be identified

2.1.3.2 Differences

Both two programs possess great values in solving the problem, but the approaches taken are largely different The major difference between Six Sigma and Kaizen is that Six Sigma uses driven technical data to address product deviations On the other hand, Kaizen concentrates on making the work environment better, which has a positive influence on overall performance Six Sigma utilizes statistics for corrections, and Kaizen uses emotions to solve employee’s problems [CITATION Die20 \l 1033 ] Kaizen's methodology improves the company as a whole and it believes that based solely on charts alone will not be enough in the long term Six Sigma follows different philosophies that direct toward measurable goals In the case of Kaizen, their primary focus has never been on achieving many of these goals in the first month or year But they always try to focus on areas where people can make themselves better The main goal of Kaizen is to make the individual's life more refined and perfect [CITATION Die20 \l 1033 ]

Six Sigma is more leaned towards standardization and Kaizen relies on the organization With organizational processes Kaizen hopes to expand their scope for improvement The integration of Six Sigma makes the goal of the process specific, which only increases a specific component of the whole product In the other words, Six Sigma method examines the final product, assessing defects in the product and seeking for methods to eliminate the cause behind the defects This strategy aims to change business processes, if necessary, to deliver a final product without defects or to change the way the product is manufactured The Kaizen approach sees business with a broader lens The goal is to enhance every aspect of the business, make processes standard, to improve efficiency, and to always seek for ways to reduce waste It is a system that always concentrates on ways to improve, from the entry-level workers to top management [CITATION Die20 \l 1033 ]

In conclusion, in this study, based on the DMAIC process, the author performed defect improvement research in the Styrofoam manufacturing department instead of entire company improvement, with the goal of finding the root defects The causes are found out by applying specific statistics, from which to propose possible improvement

solutions and ultimately the future process control plan Therefore, Six Sigma and its DMAIC methodology have a high degree of relevance to the research direction and feasibility of solving the current problem.

2.1.4 Statistical Quality Control Tools

Statistical quality control is the use of statistical techniques in collecting, classifying, processing and reflecting quality data obtained from the result of an operational process in certain forms it helps to know the realities and fluctuations of that process Statistical quality control tools are means to support managers in the process of solving issues related to production and business activities Basic statistical tools have been successfully applied by Professor Ishikawa to Japanese businesses the 1960s and twentieth century, which helps Japanese products compete with goods of the US and Western European countries.

In practical production and quality management, there are many models or methods related to the statistical theories used Models or methods are concretized in the form of tools to help people apply them easily and conveniently.

Use statistical tools in process control to ensure decision making having a scientific and practical basis, which helps explain the operation situation in a correct way, promptly detect the causes of defects to adjust appropriately.

2.1.4.1 Flowcharts

A flowchart is a picture describing the procedure in the sequence of steps Flowcharts are built by those involved in the procedure such as employees, supervisors, administrators and customers Based on flowcharts, the functions of departments, processes, etc can be improved [CITATION Bùi04 \l 1033 ]

The benefits of applying flowcharts:

 Help those involved in the process better understand it.

 Train employees about standardized procedures, which help improve effectiveness.

 Flowcharts are constructed to identify quality issues as well as areas in need of improvement.

 Full documentation to help employees understand how the process works, especially new employees

There are three common kinds of flowcharts are activity, swimlane, opportunity:  Activity flowcharts

Present the sequence of activities that make up a process in a way that focuses on what happens They are basic types of diagrams and illustrate the flow of actions, decision points, rework loop, and overall sequence of the process.

Figure 2 4 An activity flowchart of a changeover operation for a production line.

 Swimlane flowcharts:

A process is described as a cross-function as it involves different departments A swimlane flowchart (or a cross-functional flowchart) describes the sequence of operations required to perform a multifunctional process This helps clarify the department responsible for performing the activity or making the decision.

Figure 2 5 A cross-functional flowchart for acquiring new equipment.

 Opportunity Flowcharts:

The opportunity flowchart provides a way to analyse and research business processes by highlighting wasteful and complex steps This type of flowchart is often divided into two parts to differentiate activities and decisions in the process that provide value-added from those that do not

Figure 2 6 Use of an Office Copy Machine

2.1.4.2 Check Sheets

A type of form used to collect and record quality data in certain ways to assess the quality situation and make appropriate handling decisions [CITATION Bùi04 \l 1033 ]

The benefits of check sheets:

 Easily understand the full status of the problem involved  Help grasp the updated situation each time of collecting data There are five basic types of check sheets:

 Classification check sheets:

A characteristic such as a defect must be classified into a category With the classification check sheets, it provides a visual overview of issue areas.

Figure 2 7 An example of a classification check sheet

 Defect location check sheets:

The physical location of a feature is indicated in a photo or illustration of the part or item being evaluated Instead of using the number of defects, defect location check sheets can reveal an area of the product that tends to see most defects Once this is known, the team can return to the process to see what is the cause of the defect in the upper-right corner of the product (Figure)

Figure 2 8 An example of a defect location check sheet

 Frequency check sheets:

The presence or absence of a characteristic or combination of identified traits.

Figure 2 9 An example of a frequency check sheets

 Measurement scale check sheets:

A measurement scale is divided into intervals and measurements are indicated by checking an appropriate interval.

Figure 2 10 An example of measurement scale check sheets

 Check lists:

The items to be performed for a task are listed so that each is completed, it can be marked as having been completed.

Figure 2 11 An example of check lists

2.1.4.3 Histograms

A form of column chart shows visually the changes and fluctuations of a set of data in certain shapes.

To evaluate quality indicators, it is necessary to collect a lot of different data and data that is always fluctuating If you look at those randomly obtained data, it is very difficult to assess the full meaning of the information they bring and very difficult to identify their fluctuations.

In order to be able to analyse, evaluate the quality situation from the collected data, and make accurate conclusions, data is gathered, classified and rearranged to represent the distribution in the form of different column graphs according to the characteristics of the data obtained [CITATION Bùi04 \l 1033 ]

Figure 2 12 An example of histograms

2.1.4.4 Pareto Charts

The Pareto chart reflects causes of the problem organized by the proportions and the impact of causes on the problem, thereby helping you to make effective problem-solving decisions, because you know what are the main and most important causes to focus resources on This chart was first given by Pareto, the Italian economist, and then by Joseph Juran, an American quality specialist, applied in the 1950s The Pareto principle is based on the "kai") meaning change and the word 80 - 20"kai") meaning change and the word rule, which means that 80% of the problem is affected by 20% of the main reasons

The Pareto chart is applied when you are faced with multi-factor problems Using it allows choosing which solution to prioritize and manage resources most effectively Pareto charts bring benefits to those involved in improvement projects Specifically, the benefit that the organization receives is the effective allocation of resources to the most important issue, thereby creating the best opportunity for improvement It is also an effective communication tool to help Senior Leaders and others understand why

you should prioritize implementing your current operations and what the expected results are [CITATION Bùi04 \l 1033 ]

Figure 2 13 An example of a pareto diagram.

2.1.4.5 Scatter Diagrams

The scatter diagram is essentially a graph showing the correlation between cause and effect or between factors affecting quality That means the change of one trait is capable of predicting the change of another trait.

A quality indicator is created through the combination and impact of many factors There is a close relationship between the quality and the factors To evaluate the quality situation, people can use two or more data at the same time to show the correlation between the elements on the graph Through that, it is possible to determine the trend of the impact of the cause considering the specific results achieved [CITATION Bùi04 \l 1033 ]

Figure 2 14 An illustration of a scatter diagram

2.1.4.6 Causes and Effect Diagrams

The causes and effect diagrams (or called fishbone diagram) was given by Mr Kaoru Ishikawa in the 1960s He was a pioneer in quality management at the Kawasaki shipyard and is considered to be a man of merit to current management Therefore, this chart is also known as the Ishikawa chart.

This chart is called a fishbone diagram, because its shape looks like a fishbone The central bone is the spine, followed by the large, medium and small bones, drawn to connect cause and effect Therefore, it is necessary to arrange the relevant factors in a systematic way to plot causality [CITATION Bùi04 \l 1033 ]

Figure 2 15 An example of a fishbone diagram

2.1.4.7 Control charts

There are two main causes of product heterogeneity: common causes and special causes of the process The purpose of the control chart is to comment whether the process contains special causes or not in order to move towards the stability of the system.

Using the control chart can predict the next time period if the process is stable and requires no adjustments [CITATION Bùi04 \l 1033 ]

There are several types of control charts:

- Attributes charts: p chart, np chart, c chart, u chart.

- Variables charts: X and R charts, X and s charts, X-MR/I-MR charts

Figure 2 16 Types of control charts

2.1.4.8 Minitab

Minitab software is an application statistics software when applied 6 Sigma system and other process improvement methods using statistical tools.

Minitab is a comprehensive and user-friendly program With this software, it is possible solve problems from the simplest that only require statistical parameters to more complex problems such as determining the effect of different factors on characteristics by methods of regression analysis, variance with graphs illustration [CITATION GRo11 \l 1033 ]

Below is the illustration of the interface and one of the main applications of Minitab:

Figure 2 17 The interface of Minitab software

2.1.4.9 Measurement System Analysis and gage R&R

Measurement System Analysis (MSA) is a systematic method to identify and analyse the variation components of a measurement system It is a mandatory step in any Six Sigma project to ensure the data are reliable before making any data-based decisions A MSA is the check point of data quality before we start any further analysis and draw any conclusions from the data.[ CITATION Mar15 \l 1033 ]

Gage R&R, which stands for gage repeatability and reproducibility, is a statistical tool that measures the amount of variation in the measurement system arising from the measurement device and the people taking the measurement

When measuring the product of any process, there are two sources of variation: the variation of the process itself and the variation of the measurement system The purpose of conducting the GR&R is to be able to distinguish the former from the latter, and to reduce the measurement system variation if it is excessive [ CITATION GAU20 \l 2057 ]

2.2 METHODOLOGY

Study the research object

Define the problem

Set up the project goals DEFINE