applying the 8d method enhancing quality control effectiveness in the loopline at hcp factory of bosch vietnam co ltd

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<b>TECHNOLOGY AND EDUCATION</b>

MINISTRY OF EDUCATION AND TRAINING

<b>HO CHI MINH CITY UNIVERSITY OF </b>

<b>APPLYING THE 8D METHOD - ENHANCING QUALITY CONTROL EFFECTIVENESS IN THE </b>

<b>LOOPLINE AT HCP FACTORY OF BOSCH VIETNAM CO., LTD. </b>

<b>GRADUATION THESIS INDUSTRIAL MANAGEMENT</b>

<b>LECTURER: MBA. TRUONG VAN NAM STUDENT: BUI NHU NGOC</b>

SKL012383

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FACTORY OF BOSCH VIETNAM CO., LTD.

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Advisor

MBA. Truong Van Nam

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Reviewer

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ACKNOWLEDGEMENTS

First and foremost, the author would like to express heartfelt gratitude to all the professors and lecturers in the Faculty of Economics at Ho Chi Minh City University of Technology and Education who enthusiastically imparted knowledge and provided support throughout the author's time studying at the university. The sincere contributions from these esteemed teachers have laid a crucial foundation of knowledge for the author, aiding in the research process and the completion of the thesis.

Additionally, I wish to express my gratitude for the wholehearted support and guidance provided by the engineers at the TEF department, especially the TEF 3.1.1 team. Throughout my internship at Bosch Vietnam, it afforded me the chance to acquire and broaden my knowledge, enhance my skills, and gain practical experience in a professional environment teeming with creativity and dynamism. This opportunity has enabled me to bridge the divide between theoretical concepts and practical applications, prompting me to reevaluate the academic knowledge I've gained while gaining valuable insights into how it is applied in practice.

Particularly, the author wishes to extend deep gratitude to Mr. Truong Van Nam, who allocated time for guidance and provided invaluable advice that greatly contributed not only to this graduation thesis but also to the understanding and enhancement of future knowledge on the author's career path.

The author acknowledges their limitations in terms of expertise and practical experience, which may lead to potential errors in the thesis. The author sincerely hopes for input and guidance from the professors to refine and further develop their research direction in the future. Lastly, the author sends well wishes of health and prosperity to the entire company, esteemed colleagues, and professors. Sincere gratitude is sincerely expressed!

Ho Chi Minh City, 5<small>th</small> November, 2023 Student

Bui Nhu Ngoc

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LIST OF ABBREVIATIONS

Organization for Standardization (ISO)

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LIST OF TABLES

Table i: Production results according to plan from April to July, 2023 ... 1

Table 3. 1: Detailed description of the process ... 26

Table 3. 2: Common issues and remedies in Laser Cutting ... 34

Table 3. 3: Common defects in the LEM stage ... 36

Table 3. 4: Common defects and solutions in the Ring Washing stage ... 37

Table 3. 5: Common defects in the Rolling stage ... 38

Table 3. 6: Process for loop inspection after Loop Washing ... 40

Table 3. 7: Common defects and remedies in Loop Washing stage ... 40

Table 3. 8: Standard rejection for the Loop Annealing ... 41

Table 3. 9: Common defects and remedies in the SQC stage ... 42

Table 3. 10: Production output and reject rate statistics from March to July 2023 ... 43

Table 3. 11: Number of defects in each stage ... 44

Table 3. 12: Defects corresponding to each type of defect in July ... 45

Table 3. 13: Labor Statistics ... 47

Table 3. 14: Number of loopline 10 downtime incidents in July ... 49

Table 4. 1: Members of project ... 53

Table 4. 2: Summary of yellow defect locations ... 54

Table 4. 3: Frequency statistics of defect locations ... 55

Table 4. 4 Is/Is Not analysis table for addressing yellow spot on Loopline 10 ... 56

Table 4. 5: Frequency statistics of causes for yellow defects in products ... 58

Table 4. 6: Details of the loop inspection process for hypothesis 1. ... 60

Table 4. 7: Results of loopset inspection at various positions in the stage. ... 62

Table 4. 8: 5 Whys to find the root cause of yellow defects in the loopset. ... 63

Table 4. 9: Progress and effectiveness monitoring table for corrective actions. ... 65

Table 4. 1: Members of project ... 67

Table 4. 10: Is/Is not analysis table for analyzing the encountered issue ... 68

Table 4. 11: Summary of root causes for white defects ... 68

Table 4. 12: 5xWhys question for white defects on the loopset... 69

Table 4. 13: Corrective actions for each root cause ... 71

Table 4. 14: Progress monitoring and effectiveness tracking for corrective actions .... 72

Table 4. 15: Preventive actions for each root cause ... 72

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Table 4. 16: Area designation based on color standards ... 74Table 4. 17: Color standards for labels ... 76Table 4. 18: Maintenance form for machines ... 78

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LIST OF FIGURES

Figure 1. 1: Company logo ... 4

Figure 1. 2: Overview of Bosch Factory in Long Thanh ... 6

Figure 1. 3: Company Organizational Chart ... 9

Figure 1. 4: Continuous Variable Transmission (CVT) pushbelt ... 9

Figure 1. 5: Some of Bosch's customers ... 10

Figure 2. 1: Benefit of 8D method brings to organizations ... 14

Figure 2. 2: The 8D problem solving method process ... 18

Figure 2. 3: Pareto chart ... 19

Figure 2. 4: Fishbone Diagram ... 20

Figure 2. 5: Is/Is not tool and question for describing the problem ... 21

Figure 2. 6: 5xWhy technique ... 21

Figure 2. 7: TRC and MRC ... 22

Figure 2. 8: Flowchart basic symbols ... 23

Figure 2. 9: Plan - Do – Check – Act process ... 23

Figure 3. 1: The structure of a CVT pushbelt ... 24

Figure 3. 2: Operating principle of pushbelt ... 24

Figure 3. 3: Pushbelt production diagram ... 25

Figure 3. 4: Overview of the loopset production steps ... 25

Figure 3. 5: The loopset production process. ... 26

Figure 3. 6: Input material inspection flowchart ... 29

Figure 3. 7: Operator inspect the quality of steel coils ... 30

Figure 3. 8: Gap Measuring Machine along the pipe's edge. ... 32

Figure 3. 9: Steps in the Ring Washing stage ... 36

Figure 3. 10: Chart illustrates defect rate by month ... 43

Figure 3. 11: Pareto chart illustrates the high-defect-generating stages ... 44

Figure 3. 12: Pareto chart illustrates the defects occurring in the Facet stage ... 45

Figure 4. 1: Timeline for project ... 53

Figure 4. 2: Pareto chart for the locations of defects ... 55

Figure 4. 3: A fishbone diagram identifies the causes of yellow spots. ... 57

Figure 4. 4: Pareto chart of product defects ... 59

Figure 4. 5: Identification of high-risk areas for defects ... 59

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Figure 4. 6: Branch of the first hypothesis causes yellow defects on the loop. ... 60

Figure 4. 7: Causal diagram branch for yellow defects in hypothesis 2. ... 62

Figure 4. 8: Components of Sorting and the locations for loopset inspection. ... 62

Figure 4. 9: Timeline for project ... 67

Figure 4. 10: White defect on the loop surface ... 68

Figure 4. 11: The stopper button on the edge of the cover. ... 71

Figure 4. 12: Floor marking distance regulations ... 75

Figure 4. 13: Expandable label for the cart, board ... 77

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LIST OF FIGURES ... vii

TABLE OF CONTENTS ...ix

CHAPTER 1: BOSCH VIETNAM COMPANY LIMITED INTRODUCTION ... 4

1.1 Overview of Robert Bosch GmbH Corporation ... 4

1.1.1 Overview ... 4

1.1.2 Scale... 4

1.1.3 Business field ... 5

1.2 Overview of Bosch Vietnam Co., Ltd. ... 5

1.2.1 Introduction to Bosch Vietnam ... 5

1.2.2 Vision and Mission ... 6

1.2.3 Introduction to organizational structure ... 7

1.2.4 Product Business Characteristics ... 9

1.2.5 Customers ... 10

CHAPTER 2: LITERATURE REVIEW... 11

2.1 Overview of quality ... 11

2.1.1 Definition of quality ... 11

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2.1.2 Definition of quality management ... 11

2.1.3 Quality management methods ... 11

2.2 The 8D problem solving method ... 12

2.2.1 Definition ... 12

2.2.2 Objective ... 13

2.2.3 Value ... 13

2.2.4 The 8D problem solving process ... 14

2.3 Related concepts of the study ... 19

2.3.1 Pareto chart ... 19

2.3.2 Fish bone (Ishikawa Diagram) ... 20

2.3.3 Is/Is not method ... 20

2.3.4 5xWhy Technique ... 21

2.3.5 TRC and MRC ... 22

2.3.6 Flow chart ... 22

2.3.7 PDCA Cycle ... 23

CHAPTER 3: QUALITY CONTROL IN THE LOOPLINE - HCP FACTORY ... 24

3.1 Product information and production process ... 24

3.1.1 Introduction to CVT pushbelts ... 24

3.1.2 Loopset production process ... 25

3.2 Process of loopset quality control... 27

3.2.1 Incoming materials quality control ... 27

3.2.2. Quality control each stage of the loopset production process at LL10 ... 30

3.3 The quality control results at Loopline 10 ... 43

3.4 Factors affecting quality control at Loopline ... 46

3.4.1 Raw materials ... 46

3.4.2 Labor ... 47

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3.4.3 Machinery and Equipment ... 48

3.5 Assessment of the current situation at the loopline ... 50

3.5.1 Advantages ... 50

3.5.2 Limitations and Causes ... 51

CHAPTER 4: ENHANCING THE EFFECTIVENESS OF QUALITY CONTROL IN THE LOOPLINE - HCP FACTORY ... 53

4.1 Applying the 8D method to identify the root causes of yellow defects on loopsets ... 53

4.1.1 D0_Plan ... 53

4.1.2 D1_Forming a Team ... 53

4.1.3D2_Describing the Problem ... 54

4.1.4 D3_Defining containment actions ... 57

4.1.5 D4_Finding the Root Cause ... 57

4.1.6 D5: Defining corrective actions and proving effectiveness ... 64

4.1.7 D6: Implementing corrective actions and tracking effectiveness ... 65

4.1.8 D7: Establishing preventive actions ... 66

4.2.2 D2_ Describing the Problem ... 67

4.2.3 D3_ Defining containment actions ... 68

4.2.4 D4_ Finding the Root Cause ... 68

4.2.5 D5: Defining corrective actions and proving effectiveness ... 71

4.2.6 D6: Implementing corrective actions and tracking effectiveness ... 71

4.2.7 D7: Establishing preventive actions ... 72

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4.2.8 D8: Final meeting ... 73

4.3 Suggestion to enhance quality control efficiency in the loopline ... 73

4.3.1 Workforce training ... 73

4.3.2 Perfecting the 5s implementation at the factory ... 74

4.3.3 Improving machine maintenance and service operations solutions ... 77

CONCLUSION ... 79

BIBLIOGRAPHY ... 80

APPENDIX ... 82

Appendix 1: Steel coil inspection criteria ... 82

Appendix 2: Identified Chemical Components ... 82

Appendix 3: Steel Coil Production Process ... 82

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INTRODUCTION 1. Rationale

In an increasingly competitive period of economic globalization, the quality of products and services will define success or failure. Businesses are currently focused on ensuring high production, product quality, low prices, and enhanced profitability. To do this, organizations must painstakingly and properly execute the assembly line manufacturing process at each level, ensuring compliance with standards and eliminating product defects, hence avoiding the need for rework during production. It is critical to use the 8D approach to assess and resolve difficulties and incidents during the manufacturing process. This allows the organization to precisely identify and treat the fundamental causes of problems, as well as provide effective solutions.

During my past 6-month internship at the HcP factory, Bosch Vietnam Co., Ltd., this factory specialized in producing the CTV pushbelts at Bosch. The pushbelts are composed of elements and loopsets. The main materials come from specialized steel coils to ensure meeting customer output standards. To achieve this, each process in the loopset and element production line must operate optimally and steadily, with the number of defects minimized. During the internship, the author had exposure to the Loopset production line and observed a relatively high occurrence of product defects in looplines. According to production statistics from the Loopset production department:

Table i: Production results according to plan from April to July, 2023

LL10 1,089,790 91% 1,131,150 94% 1,120,010 93% 1,100,420 92%

LL11 1,159,240 97% 1,252,580 104% 1,340,010 112% 1,230,590 103% (Source: Loopset production department) As shown in the table above, the production lines are not yet truly stable, and they do not achieve the specified percentage of production according to the plan. Consequently, it requires additional time for rework to prevent a significant drop in production output. This situation has led to an increase in raw material costs and labor costs for overtime production and has a noticeable impact on the production schedule and company

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revenue. Given this situation, identifying the root causes of the productivity decline is of utmost importance. From the identified issues at the factory, the author chose the topic "Applying the 8D method: Enhancing quality control effectiveness in the Loopline at HcP Factory of Bosch Vietnam Co., Ltd." for the purpose of research and the completion of the graduation thesis.

3. Research Subject and Scope

Research subject: The production and quality control process for Loopsets Research scope:

- Spatial scope: The research is conducted exclusively within the Loopset production line at HcP Factory, Bosch Vietnam Co., Ltd.

- Time scope: From April 15<small>th</small>, 2023, to Aug 25<small>th</small>, 2023. 4. Research Methods

The research is conducted by combining scientific research methods with statistical techniques, comparisons, and analyses. From establishing theoretical foundations to practical applications, the study aims to address and clarify the research objectives. Moreover, the research places particular emphasis on collecting input from various experts, managerial personnel, and individuals involved in relevant management and operational processes, enriching and enhancing the content of the study.

Qualitative research method: Initially, the study provides an overview of relevant theories and builds upon the findings from previous research models concerning the application of the 8D method. Subsequently, through on-site observations at the factory, discussions, and research, the methodology is refined and adjusted to ensure effectiveness. This process involves developing assessment criteria and modifying questions to better serve the quantitative research phase.

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Quantitative research method: The survey is conducted by utilizing a questionnaire and a series of direct interviews. The aim of this process is to gather information from the labor force directly involved in the production line as well as from various management levels within the line. The collected data have been processed and prepared for the next steps in the research process.

Method of data collection, analysis, and synthesis: Information is gathered from internal company documents provided. This data is then analysed and synthesized, selecting relevant information for the report.

Expert opinion method: Consultation is sought from process engineers at the factory and opinions from the guiding instructor.

5. Structure of Study There are four chapters:

Chapter 1: Bosch Vietnam Company Limited Introduction Chapter 2: Literature Review

Chapter 3: Quality Control in the Loopline - HcP Factory

Chapter 4: Enhancing the Effectiveness of Quality Control in the Loopline - HcP Factory

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CHAPTER 1: BOSCH VIETNAM COMPANY LIMITED INTRODUCTION 1.1 Overview of Robert Bosch GmbH Corporation

1.1.1 Overview

Robert Bosch GmbH is a multinational technology conglomerate, founded in 1886 by Robert Bosch in Stuttgart, Germany. The company specializes in providing technology and equipment for the automotive industry and maintains business relationships with most global automobile companies. Additionally, Bosch manufactures handheld tools, household appliances, clean energy solutions, security systems, smart homes, packaging solutions, construction solutions, mobile solutions, IoT, and Industry 4.0 technologies. Company logo:

Figure 1. 1: Company logo

(Source: Bosch.com) Headquarters: Gerlingen, near Stuttgart, Germany.

Slogan: Invented for Life. Website: www.bosch.com

1.1.2 Scale

The Bosch Group comprises more than 725 subsidiaries and has over 400.500 employees in more than 60 countries worldwide. To deliver the best products and continuously evolve with the changing global landscape, the Bosch Group employs a staggering 76,100 researchers and engineers across all nations globally.

In Vietnam, the Bosch Group's first representative office is located in Ho Chi Minh City. Since 2007, Bosch has expanded with two additional offices in Hanoi and Da Nang. Bosch established the Transmission System Plant in the Long Thanh Industrial Zone in Dong Nai Province, specializing in producing CVT pushbelts for automobiles. The plant started operations in 2008 and commenced production in 2011. Currently, there are over 5,000 associates engaged in diverse business activities at Bosch Vietnam, covering fields such as Mobility Solutions, Industrial Technology, Consumer Goods, Energy Technology, and Construction.

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<small>1.1.3 Business field </small>

Automotive Technology

About 60% of Bosch's global sales revenue is related to automotive technology. Bosch was the first to invent the magneto, which was put to practical use. This was the source of electrical ignition during the early stages and was used to ignite most of the first internal combustion engines. Bosch's logo to this day symbolizes the component within the magneto. Bosch also invented the Anti-lock Braking System (ABS). Over time, Bosch has led in specialized areas such as the Traction Control System (TCS), Electronic Stability Program (EPS), vehicle electronics, oxygen sensors, fuel injectors, and fuel pumps.

Industrial equipment

Bosch's subsidiary, Bosch Rexroth, is an industrial equipment provider. Through this division, Bosch offers technology for drives, controls, and machinery operations. Another branch of Bosch is Bosch Professional, specializing in handheld power tools and specialized equipment for industrial use.

Automation is also one of Bosch's business areas, making it a reputable industrial machinery contractor while also participating in other fields such as the Internet of Things and Artificial Intelligence.

Consumer Goods and Power Tools

Bosch has expanded into the consumer goods and construction technology sectors with power tools, thermal technology, security systems, and applications for household use through its subsidiary BSH Bosch and the joint venture Siemens Hausgeräte GmbH. Furthermore, Bosch is also a renowned manufacturer of various household appliances. Monitoring Equipment

In addition, Bosch provides camera systems and monitoring software for multinational corporations, government agencies, and organizations.

1.2 Overview of Bosch Vietnam Co., Ltd.

<small>1.2.1 Introduction to Bosch Vietnam </small>

Company Name: Bosch Vietnam Co., Ltd.

Address: No. 8 Road, Long Thanh Industrial Zone, Tam An Commune, Long Thanh District, Dong Nai Province.

Primary Industry: CVT pushbelts.

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Bosch Vietnam Co., Ltd. was established in April 2008 with an initial investment of 30 million euros in the first phase and 55 million euros in the second phase in 2015. Bosch Vietnam is equipped with advanced technologies and infrastructure on a 16,000 square meter area. By April 2011, the main factory officially commenced operations, specializing in the production of CVT pushbelts for automobiles. These products are supplied to automotive manufacturers in the Asia-Pacific region.

Figure 1. 2: Overview of Bosch Factory in Long Thanh

(Source: Bosch.com)

<small>1.2.2 Vision and Mission </small>

In terms of vision, Bosch is built upon 7 foundational values. Firstly, Bosch focuses on delivering results, ensuring a prosperous future, and building a foundation for the company's social initiatives and the Robert Bosch Foundation. Secondly, the company acts carefully and responsibly, considering the interests of both the community and the environment. Thirdly, Bosch operates on its own initiatives, with a corporate spirit of responsibility and determination to pursue its goals. Fourthly, the company openly addresses important issues, fostering trust and credibility in its relationships. Fifthly, Bosch treats colleagues and business partners with fairness, considering fairness as the cornerstone of the company's success. Sixthly, the company commits only to what it can deliver, accepts binding agreements, and complies with the law in all business dealings. Finally, Bosch respects and encourages diversity, viewing it as an essential condition for success. These values underpin Bosch's vision and mission, guiding the company's actions and decisions in achieving its goals and contributing positively to society and the environment.

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In terms of its mission, the Bosch Group is built upon key elements, including:

 Goal-oriented approach: Drawing from the spirit of Robert Bosch, they aim for the sustainable future of the group by ensuring meaningful strength and development while maintaining financial independence.

 Motivation: With the slogan "Invented for Life," Bosch aspires to create products that ignite passion, improve the quality of life, and contribute to the preservation of natural resources.

 Strategic: They concentrate on customers, shaping change, and striving for the best outcome.

 Strength: Bosch relies on its cultural foundation, innovation, quality, and global presence.

Bosch establishes its values based on a set of core principles as the foundation for the future, including responsibility and sustainability, openness and trust, fairness, creativity, legality, reliability, and diversity.

<small>1.2.3 Introduction to organizational structure </small>

The departmental structure of Bosch Vietnam is divided into two main branches: Commercial Branch (HcP/PC), under the responsibility of the Commercial Plant Manager, focuses on trade and finance. Within this branch, there are four main departments with distinct roles as follows:

- CTG (Accounting): Manages the company's budget and finances.

- HRL (Human Resources): Handles tasks related to human resource management and planning, from recruitment for various positions within the company to organizing welfare programs and managing internal matters such as salaries and holidays.

- ICO (Information Coordination): Manages information and internal connectivity systems within the company. Provides software and network support to engineers and assists in connecting accounts for all employees in the company.

- LOG (Logistics): Versees tasks related to shipping, receiving raw materials, transportation, and customs procedures for goods. Records consumption reports, arranges suitable storage in the warehouse, and controls warehouse data. Additionally, this department updates the status of goods both inbound and outbound.

- TGA (Technisch Gewebliche Ausbildung): rovides vocational training alongside a professional education program based on Bosch's training program

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Production Branch (HcP/PT), under the responsibility of the Technical Plant Manager, is responsible for overseeing the entire manufacturing process of products. In each branch, there are various departments that fulfill specific functions and responsibilities. - MFG (Manufacturing): This department is responsible for producing Continuous Variable Transmission (CVT) belts, starting from manufacturing small components (elements and loopsets) to assembling these parts into complete transmission belts. MFG1: Responsible for element production.

MFG2: Responsible for loopset production.

MFG3: Responsible for assembling elements and loopsets into complete products. - QMM (Quality Management): Ensures the overall quality of the company, including establishing control processes, measurement methods, quality checks from raw material input to finished product output, and quality systems for the entire factory.

- FCM (Facilities): Manages physical facilities and equipment, including infrastructure and machinery used in the factory.

- HSE (Health, Safety, and Environment): Focuses on safety-related issues in the factory, including employee health and safety, as well as environmental protection, noise, water, and soil pollution prevention within the factory. This department also provides safety-related training and skill development for employees.

- ETC (Engineering, Testing, and Current Product): Responsible for quality testing of products to ensure the highest quality when they are released to the market.

- TEF (Technical Function): Primarily responsible for technical aspects within the factory, covering both software and hardware, including documentation. This department is further divided into several sub-departments:

TEF 1: Manages the technical production system and detects errors when issues arise. It also proposes machinery upgrade solutions to enhance operational efficiency.

TEF 3: Maintains analyses and provides maintenance strategies for machinery TEF 4: Focus on promoting digital transformation

TEF 6: Develops training programs to enhance engineers' skills in using support tools. - BPS (Bosch Production System): Manages the production system of Bosch Vietnam's Long Thanh plant.

- PRS (Protection Security): Manages plant security and safety.

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Figure 1. 3: Company Organizational Chart

(Source: Human Resources Department)

<small>1.2.4 Product Business Characteristics </small>

The products of Bosch Vietnam Co., Ltd. are Continuous Variable Transmission (CVT) pushbelts, and this is the sole product manufactured at this factory. In 2008, CVT pushbelts production was initiated at the HcP - Bosch factory located in the Long Thanh Industrial Park. Regarding CVT pushbelt, Bosch currently has three factories in three different countries producing this product: the Netherlands (Tilburg), Mexico (San Luis Potosi), and Vietnam (Long Thanh).

Figure 1. 4: Continuous Variable Transmission (CVT) pushbelt

(Source: Bosch.com)

<small>Ho Chi Minh City Plant</small>

<small>FCMHSEETCTEFBPSPRS</small>

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The strength of a CVT automatic transmission lies in its ability to efficiently operate the car's engine at all speeds. This means the pushbelt must continuously transmit power from the engine to the wheels. Furthermore, the fuel consumption of this system is lower compared to manual transmissions by up to 15%, and it also reduces emissions by more than 15%. In addition to these benefits, a CVT offers fast acceleration, reduced engine noise, and high adaptability to ensure continuous acceleration.

<small>1.2.5 Customers </small>

Bosch Vietnam operates on a pull system, manufacturing products based on customer demand. The primary market for their products is in the Asian region, with some well-known customers in the automotive industry, including companies such as Sokon, Honda, Jatco, and others.

Figure 1. 5: Some of Bosch's customers

(Source: Bosch.com)

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CHAPTER 2: LITERATURE REVIEW 2.1 Overview of quality

2.1.2 Definition of quality management

According to ISO/TC 176, "Quality management is a comprehensive approach or belief to lead and manage an organization, with the aim of continuously improving performance over the long term by focusing on the customer and addressing the needs of all other relevant parties. Quality management is not only applicable in manufacturing but in all fields, and it is not solely the responsibility of the quality department; achieving quality requires collaboration and quality assurance from other relevant departments." 2.1.3 Quality management methods

QC (Quality Control): ISO 9000 defines quality control as "a part of quality management that focuses on fulfilling requirements. Quality control can be applied to specific products, to processes that create products, or to the output of an entire organization by measuring overall organizational performance."

Quality control is a process that businesses use to ensure that product quality is maintained or improved. It requires creating an environment in which both management and employees are highly conscious of ensuring quality.

Quality control aims to ensure that the products produced meet the specifications and characteristics. The goal is to identify errors and take corrective actions promptly. Quality control helps companies meet customer and consumer demands for better products.

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QA (Quality Assurance): ISO 9000 defines quality assurance as "a part of quality management that focuses on providing confidence that quality requirements will be fulfilled."

Quality assurance systems are designed to increase customer trust and the company's reputation, while also improving processes and work efficiency, allowing the company to compete better with other rivals.

Another way to understand quality assurance (QA) is as a company's process to enhance the quality of its products. Many businesses view quality assurance programs as a commitment to stakeholders and customers that the company will provide high-quality products, ensuring a positive experience for users.

2.2 The 8D problem solving method

<small>2.2.1 Definition </small>

According to Seel (2012), “A problem is generally considered to be a task, a situation, or person which is difficult to deal with or control due to complexity and intransparency. A problem is a question proposed for solution, a matter stated for examination or proof. In each case, a problem is considered to be a matter which is difficult to solve or settle, a doubtful case, or a complex task involving doubt and uncertainty."

Besides that, a problem is also defined as deviations that affect the results in an unexpected way. It is uncontrolled and has a significant impact on the outcomes. Due to its complexity, solving the problem is one of the priority tasks that all organizations, as well as individuals, need to focus on (Viet Quality, 2019).

Generally, a problem encompasses all the variables that affect the final result, leading to unexpected consequences. Problems are omnipresent, occurring for diverse reasons, both external and internal, within every firm. These issues within enterprises have a profound influence on operational processes, necessitating prompt resolution to prevent future recurrences. Presently, numerous strategies are available to assist businesses in tackling challenges, with the 8D method being a popular choice adopted by many firms. Tkác et al. (2013) claimed it that:

The 8D method is a tool, the essence of which is a standardized process with an emphasis on facts. It also serves to improve products and processes. This method can be used in energy sources, means of transport and the transport of material. It

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often happens in practice that statistical methods of quality control are applied to final inspection rather than the management of production processes.

Historically, this method was first implemented by the United States Government and was standardized as the 8D process during World War II. In the sixties and seventies of the twentieth century, the Global 8D method was popularized by Ford Motor Company. In addition to automotive industry and assembly, the 8D method became the norm wherever a comprehensive and structured approach to problem solving is necessary.

<small>2.2.2 Objective </small>

The primary goal of the 8D problem-solving method is to emphasize problem definition through a thorough analysis of root causes, ultimately leading to the formulation of lasting corrective and preventive measures. This approach aids businesses in effectively resolving past errors by leveraging accumulated knowledge and charting a clear path for addressing the issue.

According to Krajnc (2012), the 8D report, which focuses on the synergy of interdisciplinary teams and a systematic eight-step approach, can be used to eliminate failures and non-conformities in many industrial sectors, including quality control. This method means permanent corrective actions and, by identifying the root causes, prevents their reoccurrence in the future. The 8D method used in the organization and presented in this research is an excellent tool for preventing defects from recurring, as indicated by the PPM (parts per million) results but also by related costs.

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Figure 2. 1: Benefit of 8D method brings to organizations

(Source: Marjanca Krajnc, 2012) In another case study conducted by Alexa and Kiss (2016), a customer received a delivery with delivery note 114643176 dated 27 June 2015, which led to a customer complaint due to non-compliant packaging with finished goods specifications. The improvements made in this case study were later implemented within the company. Additionally, a quality assurance analysis in the logistics department of the factory ensured the production of high-quality sensors to prevent defects and establish measures to prevent recurrences. Therefor, 8D also assist organizations in complying with specific customer requirements for regulatory concerns

In summary, the 8D problem-solving method offers several advantages for businesses, including establishing a structured and collaborative approach to problem-solving. This method enhances individual and team effectiveness in addressing customer concerns promptly and aligns with quality management system requirements. It also proactively identifies and prevents future issues, leading to reduced quality costs through process improvement insights and helps organizations meet specific customer requirements, especially those related to regulatory compliance.

2.2.4 The 8D problem solving process

The 8D approach must be implemented in the following eight steps: D1: Establishing problem solving team/project

During this step, the primary objective is to assemble a team that possesses sufficient expertise in the product or process where the problem has arisen, in order to devise a solution. It is imperative for a problem-solving team to consist of members who

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collectively possess the requisite knowledge and experience to function effectively. Ideally, a team should comprise 5-10 members drawn from diverse departments and involved in the respective process or product.

The composition of each team will vary based on the appropriate allocation of members. A complete 8D problem-solving team typically includes the following roles:

The first is Sponsor. This individual serves as the project sponsor, usually holding a position of high authority and influence within the company, such as a department head. Their responsibility is to ensure the provision of necessary resources for project implementation.

The second is Team Leader. The team leader is appointed by the Sponsor and assumes the role of leading, managing, monitoring progress, and reporting back to the Sponsor. The final is Team Members. The remaining team members must possess knowledge or expertise relevant to the problem. In most cases, members are selected from different departments, each responsible for specific tasks related to the problem-solving process. D2: Describing the Problem

The depiction of the current (actual) state, combined with the examination of variances, unique facets, and associations stemming from the identification of the problem's location, results in the fundamental problem - a refined problem (in terms of time, location, quantity, etc.) that is distinctly separated from unaffected areas. The fundamental problem constitutes the transition from the problem-oriented to the cause-oriented part of the PSS.

Hence, team members must collaborate efficiently to address the following W questions: Who? What? Where? When? How many? and Is/Is not tool. Consequently, the outcome is a thorough, unambiguous, intelligible, and broadly comprehensible depiction of the situation. This involves the organization and analysis of the problem grounded in factual information, effectively constraining the issue and distinguishing it from unaffected regions. This initial risk assessment entails evaluating the likelihood of occurrence and the magnitude of damage, as well as assessing the impacts on end-users and products. D3: Defining containment actions

During step D3, temporary actions should be taken to reduce and isolate the effects of the defect on other products and the production process. Several actions can be executed at this step, including isolating the affected area, installing temporary solutions, halting

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the production line or process, and more. This step can be initiated prior to both D1 and D2 to swiftly mitigate the risk of errors and safeguard customers from the consequences of the problem.

The objective of this step is to ensure that the customer does not receive, use, or deliver any non-conforming products. To achieve this, team members need to undertake several actions. Firstly, implementing containment actions to limit the impact of the problem while considering factors like speed and cost-effectiveness. This should encompass all potentially affected areas, including manufacturing, warehousing, and transportation to the customer. Secondly, evaluating the effectiveness of these containment measures.Thirdly, communicating information about the non-conformity within the affected area (e.g., the next shift) as well as to potentially affected areas (e.g., other production lines or parts). Finally, team members should implement containment measures that include documentation and information dissemination.

D4: Cause and Effect Analysis

The objective of this step is to unambiguously identify, reproduce, and prove the root cause of the non-conformity. Therefore, team members must undertake a series of tasks, including:

Firstly, systematically and thoroughly identifying all root causes related to the occurrence and non-detection, with reference to the facts compiled in D2.

Those possible causes which seem most probable can be narrowed down D2 through a logic check by asking a few key questions: Do the facts and current state description seem plausible assuming this is the cause? The resultant most probable causes (typically one to three) are scrutinized (applying the “5 x Why” method) yielding the root cause (verified through “why … therefore …” forward and backward logic statements) Secondly, verifying the root cause, preferably by replicating both the occurrence of the non-conformity (e.g., through simulation or experimentation) and its non-detection (e.g., using a test setup).

The third is delving deep by systematically identifying managerial root causes (MRC) based on technical root causes (TRC).

Finalizing the risk assessment, which should encompass an evaluation of the fault's severity, the likelihood of its occurrence or discovery, and an estimation of its potential impact.

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Finally, the team must document the derivation and description of the root cause (both TRC and MRC) with supporting evidence.

D5: Defining corrective actions and proving effectiveness

Following the identification of the root cause of the issue in step D4, the team compiles a list of potential solutions and implementations capable of fully resolving the problem. To determine the correct solution, it is imperative to either simulate or experiment with its application for a period, as employing an incorrect solution not only fails to completely resolve the issue but may also lead to more significant repercussions or impact other components.

The aim of this step is to ensure the verification of effective corrective actions for eliminating the root cause. Consequently, team members are required to perform a series of tasks, including:

- Identifying potential corrective actions to eliminate both TRC and MRC.

- Demonstrating the effectiveness of these actions through theoretical means (e.g., FMEA or a description of the modified process flow) and/or practical examinations. - Taking precautions to prevent any unintended secondary effects that may give rise to new problems.

- Selecting the corrective actions to be implemented.

Finally, documenting the corrective actions, supported by evidence of their effectiveness, to comprehensively address the root causes identified in D4.

D6: Implementing corrective actions and tracking effectiveness

This step occurs subsequent to the selection of potential solutions for implementation. In this phase, it is recommended to halt activities that could influence the process or product to ensure the collected data and observed outcomes are as effective as possible. The application duration should be sufficiently extensive to achieve effectiveness. Furthermore, even if corrective actions have been tested prior to their application at this step, it remains imperative to persist in monitoring and documenting data to evaluate any potential adverse effects.

D7: Establishing preventive actions

In order to significantly reduce the likelihood of future failures, it is essential to uphold the effectiveness of prventive actions. One such measure involves creating a record through documentation, procedural guidelines, or incorporating updates into FMEA.

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These measures not only serve as a barrier against the reappearance of flaws in the same process or product but also serve as valuable insights for other processes and products, helping to prevent the repetition; of similar errors.

The objective of this step is to prevent similar problems stemming from identified root causes from arising in other areas. As a result, team members are tasked with a series of responsibilities, which include:

- Reviewing and updating documentation, such as FMEA, Control Plans, drawings, and so on.

- Establishing suitable measures within the framework of the Quality Management System.

- Sharing acquired expertise through a Lessons Learned Network with all relevant products, processes, and locations.

The outcomes of this step should encompass the revision of standards, the exchange of experiences through a knowledge-sharing network, and confirmation and evaluation by the Learning Link Network.

D8: Final meeting

Following the conclusion of the problem-solving project, the team should undertake a comprehensive review of the implementation process. This review should encompass an evaluation of both the strengths and limitations encountered during implementation. Furthermore, it is essential to document feedback received from advisors, as it can contribute to improved performance in future endeavors. Additionally, during this phase, it is crucial to express praise and recognition from leadership to foster motivation and promote a sense of cooperation and active participation in the project implementation process.

Figure 2. 2: The 8D problem solving method process

(Source: Bosch group.com)

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2.3 Related concepts of the study

<small>2.3.1 Pareto chart </small>

As claimed by Burke & Silvestrini (2017) put it:

A Pareto chart graphically depicts the ―80/20 rule originally postulated by the Italian economist Vilfredo Pareto to explain economic phenomena.... The 80/20 rule allows users to identify and focus on the approximately 20% of factors (i.e., columns or categories) that account for approximately 80% of potential problems. The purpose of a Pareto chart is to identify those “vital few” areas that account for the largest frequency or relative frequency in a data set and separate them from the “trivial many.”

Characteristics of a Pareto chart

- On the X axis you have the area of interest (categories) e.g. as ward names. - On the left Y axis you have the number of events e.g. number of falls. - On the right Y axis you have the cumulative frequency.

- Essentially, a Pareto chart is a bar and line graph combined. The bars display the number of events per area of interest whilst the line displays the cumulative % of events. - Categories contributing to 80% of the problems are often referred to as the ‘vital few’ whereas the others are labelled the ‘useful many’.

Figure 2. 3: Example of Pareto Chart

(Source: Minitab.com)

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<small>2.3.2 Fish bone (Ishikawa Diagram) </small>

Fishbone is one method or tool in improving quality. This diagram also called the and-effect diagram. The inventor was a Japanese scientist in the 60s, namedDr. Kaoru Ishikawa, he was born in 1915, scientist at Tokyo Japan who is also a chemistry alumnus at the University of Tokyo. Thus,the diagram also called Ishikawa diagram.

cause-According to Burke & Silvestrini (2017), the purpose of a cause-and-effect digram is to graphically document the analysis of factors (causes) that relate to s single problem or opportunity (effect). Cause-and-effect diagrams are used in problem-solving situations and in general analysis to help the problem-solving or analysis team bothh understand how those factors may cause the given effect and focus on “next steps” in provess improvement.

Figure 2. 4: Fishbone Diagram

(Source: Burke & Silvestrini, 2017) As mentioned previously, a single peoblem or opportunity is identified on the right side of the graphic. Major causes often referred to as the 6 Ms: Man (personal or personel), Machine ( hardware/ equipment), Materials, Methods, Measurements, Mother Nature (Enviroment)

2.3.3 Is/Is not method

According to Mulder, P. (2012), the Is/Is Not analysis (KT analysis) is a method used to identify problems by distinguishing what is within the problem area - the factors included in the analysis - from what is not within the scope of the problem. Consequently, analysts can exclude those elements from the analysis. In simpler terms, Is/Is Not analysis aids the implementation team in selecting which points to incorporate and which to omit. This definition serves to concentrate on and precisely define the

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problem's scope, preventing confusion and deviations from the original requirements, thereby enhancing the effectiveness of the problem-solving process.

Figure 2. 5: Is/Is not tool and question for describing the problem

(Source: Robert Bosch GmbH. 2013) 2.3.4 5xWhy Technique

According to Olivier Serrat (2009), the 5-Why analysis technique is employed when attempting to resolve a problem by repeatedly asking the question "Why?" regarding the issue until the underlying problem is unearthed. This questioning process fosters in-depth examination of the matter in a methodical manner. To ensure methodical application, three key factors must be adhered to: Firstly, the problem presented must be both comprehensive and accurate; secondly, honesty in answering the questions is essential; thirdly, once the problem is identified, it must be completely addressed. This technique was established and refined by Mr. Sakichi Toyoda (1867-1930) and has been applied to the production processes of the Toyota Corporation.

Figure 2. 6: 5xWhy technique

(Source: Robert Bosch GmbH. 2013)

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Additionally, flow charts are used either to represent a chronological sequence of events (chronology of events, history chart) and/or the chronological change of parameters (flow charts for facts analysis regarding deviations/influencing factors). Both types of descriptions are used, among other things, for condensed documentation and an analysis of differences, special features and changes over the course of a problem situation. (Robert Bosch GmbH. 2013)

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Figure 2. 8: Flowchart basic symbols

(Source: Tague, 2005) 2.3.7 PDCA Cycle

As outlined by Nancy R. Tague (2005), the Plan-Do-Check-Act (PDCA) process is a four-step framework for effecting change, and it should be iterated multiple times to ensure sustained and adjusted enhancements. PDCA is a widely adopted model for enhancing business processes, and it can also be applied on a smaller scale, such as in each individual step of an improvement process.

Figure 2. 9: Plan - Do – Check – Act process

(Source: Tague, 2005)

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CHAPTER 3: QUALITY CONTROL IN THE LOOPLINE - HCP FACTORY

3.1 Product information and production process 3.1.1 Introduction to CVT pushbelts

Currently, the HcP factory exclusively produces CVT pushbelts, primarily serving customers such as Jatco and Honda, etc. Instead of using gears, the transmission system in automobiles utilizes a sliding belt between two separate conical pulleys. This system adjusts the distance between the pulleys to alter the contact circumference of the belt, resulting in changes to the transmission ratio. Furthermore, unlike typical scooters that use rubber belts, the belts used in automotive transmissions are made from steel materials.

Figure 3. 1: The structure of a CVT pushbelt

(Source: Bosch.com) The drive belt's two basic parts are elements and a loopset which together make up the product's structure. Each CVT pushbelt is composed of 19 to 400 interlocking elements, along with two loopsets fastened on both sides of the belt segments. About 6 to 12 separate loops are layered together to form a loopset.

Figure 3. 2: Operating principle of pushbelt

(Source: Bosch.com)

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3.1.2 Loopset production process

To produce a pushbelt, it is necessary to go through the main stages.

Figure 3. 3: Pushbelt production diagram

(Source: Author analyses) The process of manufacturing a CVT pushbelt consists of three main stages: the element production process, the loopset production process, and the assembly process to complete a pushbelt. However, within the scope of this topic, the thesis focuses on researching the reprocessing stages of products that do not meet the requirements in the loopset production process.

A loopset is formed from rings to various loops with different sizes. The production steps for a loopset are as follows:

Figure 3. 4: Overview of the loopset production steps

(Source: Author analyses)

<small>ELEMENT </small>

<small>LOOPSET </small>

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Figure 3. 5: The loopset production process.

(Source: Loopset production department) Table 3. 1: Detailed description of the process

LEM

(Laser Edge Melting)

Rounding the edge of rings after Laser Cutting

Ring annealing To recrystallize, restore material properties, and particle size