VIET NAM NATIONAL UNIVERSITY HO CHI MINH CITY HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY TRAN NGOC QUYNH LEAN – SIX SIGMA IN SCRAP COST IMPROVEMENT: AN APPLICATION IN ELECTRONICS MANUFACTURING SYSTEM Major: Industrial Engineering Major ID: 8520117 MASTER THESIS HO CHI MINH CITY, January 2023 THIS RESEARCH IS COMPLETED AT: HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY – VNU HCM Instructor: Assoc. Do Ngoc Hien …………………………………………………. Nguyen Vang Phuc Nguyen………………………………………………… Examiner 2: PhD. Nguyen Van Thanh………………………………………………………….
Master’s Thesis is defended at HCMC University of Technology, VNU-HCM on January 08, 2023. The Board of The Master’s Thesis Defense Council includes: 1. Do Thanh Luu ………………………………………………………. Le Song Thanh Quynh………………………………………………….
Counter-Argument Member: PhD. Nguyen Vang Phuc Nguyen……………. Counter-Argument Member: PhD. Nguyen Van Thanh……………………………….
Council Member: Assoc. Do Ngoc Hien ……………………………………. Verification of the Chairman of the Master’s Thesis Defense Council and the Dean of the Faculty of Mechanical Engineering after the thesis is corrected (if any). CHAIRMAN OF THE COUNCIL DEAN OF FACULTY OF MECHANICAL (Full name and signature) ENGINEERING (Full name and signature) VIETNAM NATIONAL UNIVERSITY HCMC SOCIALIST REPUBLIC OF VIETNAM VNUHCM UNIVERSITY OF TECHNOLOGY Independence – Liberty – Happiness ________________________ __________________ MASTER’S THESIS ASSIGNMENTS Full name: TRAN NGOC QUYNH.
Date of birth: 29th October, 1998. Place of birth: Ca Mau. Major: Industrial Engineering. I – TITLE: LEAN – SIX SIGMA IN SCRAP COST IMPROVEMENT: AN APPLICATION IN ELECTRONICS MANUFACTURING SYSTEM/ NGHIÊN CỨU ỨNG DỤNG LEAN SIX - SIGMA VÀO GIẢM CHI PHÍ PHẾ PHẨM: TRƯỜNG HỢP ĐIỂN CỨU TẠI NHÀ MÁY LẮP RÁP HÀNG ĐIỆN TỬ ASSIGNMENTS AND CONTENT: Assignments: Investigate a production system to identify the quality and productivity-related problems and their root causes Collect the information and data to prove the problem Propose a Lean Six Sigma framework to reduce the scrap cost rate in an EMS factory Reduce the scrap cost rate to meet the company target Content: Chapter 1 gives a general introduction to the research object and problem.
The research objectives, limitations and scope of the study, the content to be performed, and layout of the study will also be briefly presented in this chapter. Chapter 2 presents the theories used in the research will be presented, including the Lean concept, Six Sigma methodology, in-process kanban (IPK), Maynard operation sequence technique (MOST) and related studies. Chapter 3 introduces a research methodology with step to step to carry out this study. Chapter 4 presents an overview of the research object, such as process, layout, traceability systems, etc.
The Define, Measure and Analyze phases will be discussed in this chapter. All data collected is analyzed to identify the improvement opportunity and form a research problem. As a result, this session will also conduct improvement actions to solve the problem's root cause. Moreover, the control plan will also be defined to maintain the improvement actions and their results.
Chapter 5 reports the conclusion of the thesis. The remaining shortcomings will be pointed out, and possible developing directions for the future will be suggested. i II – ASSIGNMENT DELIVERING DATE (based on the Decision on Assignments Delivering): September 05, 2022. III – ASSIGNMENT COMPLETING DATE (based on the Decision on Assignments Delivering): December 18, 2022.
IV – INSTRUCTOR: Assoc. Do Ngoc Hien. Ho Chi Minh City, December 23, 2022 INSTRUCTOR HEAD OF DEPARTMENT (Full name and signature) (Full name and signature) DEAN OF FACULTY OF MECHANICAL ENGINEERING (Full name and signature) ii ACKNOWLEDGEMENT "Lean – Six Sigma in scrap cost improvement: an application in Electronics Manufacturing System" is a result of whale time at the Department of Industrial Systems Engineering, HCMC University of Technology. This thesis would not have been feasible without the untold amount of encouragement from numerous people who enabled me to complete the study.
First and foremost, I would like to express my heartfelt appreciation and deepest gratitude to my primary advisor – A/Prof. Đỗ Ngọc Hiền for his guidance over the course of this thesis study. I am grateful beyond words that he is ready to discuss issues with vast information I have had no chance to be shared before. I could not have asked for a better advisor for my thesis study.
Besides, thanks for the enthusiastic support from colleagues at Jabil company. In the process of implementing as well as collecting data, I have received very enthusiastic support from both teachers and brothers and sisters in the company. I would like to especially thank Mr Danh Võ – IE Functional Manager and Ms Nhi Trần – IE Engineer who facilitated and supported me directly in this project. I would also like to thank the IE support team members who have always enthusiastically supported me in my work and searching for orientation for graduation thesis topics in the company.
In addition, I would like to thank the friends who have helped me through the difficulties and also the joys. Thank you for making my life more colourful. Last but not least, I would like to express my sincerest thanks to my greatest source of motivation and inspiration: thank you to my parents for always supporting me in every way. Thank you, my brother – Trần Quốc Công, PhD for advice and guidance.
I would not have gotten to where I am today without your support. In the process of working and reporting, mistakes will inevitably be made, and I would like to ask for your comments and corrections so that I can improve my knowledge as well as future orientation. Trần Ngọc Quỳnh iii ABSTRACT This research presents six sigma implementation conducted in an EMS enterprise to reduce scrap cost rate and thereby increase its sigma level. The study has gone through the problem that the factory is facing: the percentage of scrap cost is higher than the target (actual 0.
Using the DMAIC methodology, the root cause was defined as product handling, tool-using and IPK identification between stations. Then, three improvement actions were taken to address the three identified causes. The solutions are to change the board handling trays, add a mandatory scan step when using a screw jig, and determine the number of IPKs between stations. After applying improvement solutions, the line performance is significantly improved.
The sigma level improved from 2.43 for the download station and from 2.19 for the wintest station. Since then, the rate of products passing the first time (FPY) has also improved, from 98.55%, compared to the factory's target is 98. Furthermore, the research's target was also achieved when improving the scrap cost ratio from 0. This result proves the effectiveness of the study, meeting the research objectives and the company's expectations.
Keywords: Lean Six – Sigma, scrap cost reduction, MOST, FlexSim simulation, IPK iv TÓM TẮT LUẬN VĂN Nghiên cứu này trình bày việc triển khai Six - Sigma trong một doanh nghiệp EMS để giảm tỷ lệ chi phí phế phẩm và từ đó tăng mức sigma của hệ thống. Nghiên cứu đã đi sâu vào vấn đề mà nhà máy đang gặp phải: tỷ lệ chi phí phế phẩm cao hơn so với mục tiêu (0.03% thực tế so với mục tiêu 0. Bằng việc sử dụng chu trình DMAIC, nguyên nhân gốc rễ được xác định là do thao tác di chuyển sản phẩm, thiếu công cụ hỗ trợ khi thao tác và IPK giữa các trạm chưa được xác định rõ ràng. Sau đó, ba giải pháp cải tiến đã được thực hiện để giải quyết ba nguyên nhân được xác định.
Các giải pháp là thay đổi các khay dùng dể vận chuyển bo mạch, thêm bước quét bắt buộc khi sử dụng đồ gá và xác định số lượng IPK giữa các trạm. Sau khi áp dụng các giải pháp cải tiến, hiệu suất dây chuyền được cải thiện rõ rệt. Mức sigma được cải thiện từ 2.43 cho trạm Download và từ 2.19 cho trạm Wintest. Từ đó, tỷ lệ sản phẩm đạt lần đầu tiên (FPY) cũng được cải thiện, từ 98.55%, so với mục tiêu của nhà máy là 98.
Ngoài ra, mục tiêu của nghiên cứu cũng đã đạt được khi cải thiện tỷ lệ chi phí phế liệu từ 0. Kết quả này chứng tỏ tính hiệu quả của nghiên cứu, đáp ứng mục tiêu nghiên cứu và kỳ vọng của công ty. v DECLARATION I hereby declare that this is my own research. All the data and the results used in this research are honest and have not been published in other studies.
I will be totally responsible for my research if it is incorrect as mentioned above. The research’s author TRAN NGOC QUYNH vi CONTENTS MASTER’S THESIS ASSIGNMENTS. IV TÓM TẮT LUẬN VĂN. VII LIST OF FIGURES.
VIII LIST OF TABLES .X LIST OF ABBREVIATIONS .2 RESEARCH OBJECTIVE AND SCOPE .1 LEAN SIX SIGMA .2 IN-PROCESS KANBAN (IPK) .3 MAYNARD OPERATION SEQUENCE TECHNIQUE (MOST). THE DMAIC METHODOLOGY .2 Scrap definition, FPY dashboard and EDMR system. CONCLUSION AND DISCUSSION .40 LIST OF PUBLICATIONS. 58 vii LIST OF FIGURES FIGURE 1.
EXAMPLE OF IPK. MOST DATA CARD. DMAIC METHODOLOGY FRAMEWORK. THE LAYOUT OF THE ASSEMBLY LINE.
FPY DASHBOARD INTERFACE. EMDR SYSTEM INTERFACE. BB SCRAP COST IN 10 WEEKS. %CONTRIBUTION OF SCRAP ISSUES.
%SCRAP COST TREND CHART. SIPOC OF THE PROJECT. BB SCRAP BY DEFECTS. DEFECTS BREAKDOWN BY PROCESS.
BB FPY AND SCRAP TREND CHART. CTQS OF THE PROBLEM. DESCRIPTIVE REPORT FOR THE SCRATCH DEFECT RATE. DESCRIPTIVE REPORT FOR SCRATCH DEFECT RATE (REMOVED OUTLIERS).
PROCESS CAPABILITY ANALYSIS FOR DOWNLOAD STATION. DESCRIPTIVE REPORT FOR THE DEFORMED CABLE DEFECT RATE. DESCRIPTIVE REPORT FOR DEFORMED CABLE DEFECT RATE (REMOVED OUTLIERS). PROCESS CAPABILITY ANALYSIS FOR THE WINTEST STATION.
AUTO QUALITY MATRIX. CHI-SQUARE TEST FOR DEFECT RATE OF 12 OPERATORS. FISHBONE DIAGRAM FOR SCRATCHES AND DEFORMED CABLE DEFECTS. SCRATCHES ON CASING.
THE TRAY BEFORE AND AFTER REPLACEMENT. DAMAGED NEAR SCREW HOLES. ASSEMBLY 5 MOST ANALYSIS – BEFORE. ASSEMBLY 10 MOST ANALYSIS - BEFORE.
ASSEMBLY 5 MOST ANALYSIS – AFTER. ASSEMBLY 10 MOST ANALYSIS - AFTER. ASSEMBLY LINE BALANCING CHART BEFORE AND AFTER. SIMULATED MODEL AND CYCLE TIME GLOBAL TABLE.
PARETO OF PRODUCT DEMAND. T-TEST OF OUTPUT FROM THE SIMULATION MODEL AND ACTUAL OUTPUT. MODEL'S THROUGHPUT BY TIME. WIP BETWEEN PROCESSES.
SIMULATED MODELS WITH A) IPK = 4, B) IPK = 3, C) IPK = 2 AND D) IPK = 1. DEFINE THE LOCATION FOR WIP BETWEEN WORKSTATIONS. CHI-SQUARE TEST FOR DEFECT RATES BEFORE AND AFTER IMPROVEMENT. PROCESS CAPABILITY OF DOWNLOAD AND WINTEST STATION.
BB FPY AND %SCRAP COST RATE TREND BEFORE AND AFTER IMPROVEMENT. PFMEA WITH SCAN PLV REQUIREMENT. THE HANDLING CONTAINER WITH CAVITIES REQUIREMENT. SCRAP COST DASHBOARD AND WEEKLY REPORT.
38 ix LIST OF TABLES TABLE 1. % SCRAP COST CONTRIBUTION BY CUSTOMER. DATA COLLECTION PLAN. CAUSES AND COUNTERMEASURES.
SUMMARY RESULT OF 4 SCENARIOS. SUMMARY OF IMPROVEMENT ACTIONS. SUMMARY OF RESULTS. SUMMARY OF SCRAP COST IN 10 WEEKS.
DEFECT BY OPERATORS. PRODUCTION PLAN FOR FLEXSIM MODEL INPUT. THROUGHPUT FROM SIMULATION MODEL AND FROM MES SYSTEM FOR TOP 5 PRODUCTS. SCRATCHES DEFECT RATE BEFORE AND AFTER IMPROVEMENT.
DEFORMED CABLE DEFECT RATE BEFORE AND AFTER IMPROVEMENT. 54 x LIST OF ABBREVIATIONS Abbreviation Meaning 4Q 4 Quadrands BB Box build BOM Bill of materials CTQ Critical to quality eMDR Electronic Materials Disposition Report EMS Electronics manufacturing services FPY First pass yield FVT Functional Validation Test IPK In – process kanban KPI Key performance indicator LSS Lean Six Sigma MES Manufacturing execution system N/A Not applicable NVA Non – value added PCB Printed circuit boards PCBA Printed circuit boards assembly PFMEA Process failure modes and effects analysis PLV Production line verification SMT Surface-mount technology UPH Units per hour WIP Work in progress xi CHAPTER 1.
