Application of six sigma methodology in battery assembly line to improve quality and productivity

VIETNAM NATIONAL UNIVERSITY HO CHI MINH UNIVERSITY OF TECHNOLOGY NONG NGOC VU APPLICATION OF SIX SIGMA METHODOLOGY IN BATTERY ASSEMBLY LINE TO IMPROVE QUALITY AND PRODUCTIVITY 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 1: Assoc Prof PhD Do Ngoc Hien Instructor 2: Assoc Prof PhD Le Ngoc Quynh Lam Examiner 1: PhD Nguyen Van Thanh Examiner 2: PhD Nguyen Duc Duy 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: Chairman: PhD Nguyen Vang Phuc Nguyen Secretary: PhD Duong Quoc Buu Counter-Argument Member: PhD Nguyen Van Thanh Counter-Argument Member: PhD Nguyen Duc Duy Council Member: Assoc Prof PhD 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) i VIETNAM NATIONAL UNIVERSITY HCMC SOCIALIST REPUBLIC OF VIETNAM VNUHCM UNIVERSITY OF TECHNOLOGY Independence – Liberty – Happiness MASTER’S THESIS ASSIGNMENTS Full name: Nong Ngoc Vu Learner ID: 2070335 Date of birth: March 03, 1996 Place of birth: Binh Phuoc Major: Industrial Engineering Major ID: 2070335 I – TITLE: APPLICATION OF SIX SIGMA METHODOLOGY IN BATTERY ASSEMBLY LINE TO IMPROVE QUALITY AND PRODUCTIVITY / NGHIÊN CỨU CẢI TIẾN CHẤT LƯỢNG VÀ NĂNG SUẤT CHUYỀN LẮP RÁP DÒNG SẢN PHẨM PIN VỚI GIẢI PHÁP SIX SIGMA II – ASSIGNMENTS AND CONTENT: - Analyze the current state of quality in battery assembly line, identify problems and find the causes - Analyze the current state of productivity of the line and find the causes - Deploy Sigma by using DMAIC cycle for battery assembly line - Record and analyze the results achieved from the Six Sigma methodology III – ASSIGNMENT DELIVERING DATE: September 05, 2022 IV – ASSIGNMENT COMPLETING DATE: December 18, 2022 V – INSTRUCTOR: Assoc Prof PhD Do Ngoc Hien - Assoc Prof PhD Le Ngoc Quynh Lam Ho Chi Minh City, January 08, 2023 INSTRUCTOR INSTRUCTOR HEAD OF DEPARTMENT (Full name and signature) (Full name and signature (Full name and signature) DEAN OF FACULTY OF MECHANICAL ENGINEERING (Full name and signature) ii ACKNOWLEDGEMET During the implementation of the project "Application of six sigma methodology in battery assembly line to improve quality and productivity", I received guidance and support to be able to carry out the thesis Therefore, I would like to express my sincere thanks to: - Mr Do Ngoc Hien, Department of Industrial Systems Engineering, Faculty of Mechanical Engineering, Ho Chi Minh City University of Technology He has guided, advised and supported me throughout the process of making the outline and doing the thesis - Teachers in the Department of Industrial Systems Engineering, Faculty of Mechanical Engineering, Ho Chi Minh City University of Technology have enthusiastically shared and consult knowledge and suggestions for the topic - The suggestions and information sharing of the company managers and colleagues in my business, classmates and friends who did the support me in the process of data collection and implementation of the thesis Finally, I would like to express deep gratitude to family and friends, classmates, who have always supported and given me strength to complete this thesis Wishing you and everyone a lot of health, happiness and success in life! Ho Chi Minh City, December 18, 2022 Nong Ngoc Vu iii ABSTRACT Problem statement: In the trend of global economic transformation, the pressure is creasing on the companies, factories due to competition Specifically, battery manufactures are struggling on many aspects including competitive production process, effectiveness, quality control… The Techtronic Industries company is one of those, the quality control and the performance of the process have not been at highly optimizing level since the factory were recently established in 2019 The battery product of the company got high customer return ratio of 0.5%, low overall sigma level of 3.95 and the actual production output attainment of 88% with plan There is a need of increasing the quality and productivity Purpose and solution: To carrying out and implementing the thesis with the topic of improving the quality and productivity of the battery assembly line with Six Sigma solution by using DMAIC cycle at Techtronic Industries company From the review of various literatures, it is revealed that Six Sigma is well adopted in many manufacturing processes as effective systematic approach The thesis is going is study theories related to Six Sigma, analyze the current status of the battery assembly line, determine the causes affecting quality and productivity failures, plan and implement improvement into the assembly line according to the DMAIC cycle Results: - Sigma level of overall production line increased from 3.95σ to 4.12σ - Production output capacity increased from 76 pcs/h to 81 pcs/h - Actual production output attainment of plan increased from 88% to 96% Practical meaning: Reduce the failures of the production line and improve the productivity of the line Play as a basis reference for the deployment to other lines in the company The thesis is an application of Six Sigma solution to battery assembly process iv TĨM TẮT LUẬN VĂN Mơ tả vấn đề: Trong xu chuyển đổi kinh tế toàn cầu, áp lực cạnh tranh ngày lớn công ty, nhà máy Cụ thể, nhà sản xuất pin gặp khó khăn nhiều mặt bao gồm tối ưu quy trình sản xuất, hiệu sản xuất, kiểm sốt chất lượng… Cơng ty Techtronic Industries số đó, việc kiểm soát chất lượng hiệu suất quy trình chưa tối ưu hóa cao nhà máy thành lập Sản phẩm pin công ty có tỷ lệ lỗi phản hồi từ khách hàng cao 0,5%, mức sigma chung 3,95 sản lượng sản xuất thực tế đạt 88% so với kế hoạch Nâng cao chất lượng suất dây chuyền mang tính cấp thiết cao Mục đích giải pháp: Tác giả mong muốn triển khai thực luận văn với chủ đề nâng cao chất lượng suất dây chuyền lắp ráp pin giải pháp Six Sigma theo chu trình DMAIC cơng ty Techtronic Industries Từ việc xem xét tài liệu khác cho thấy Six Sigma áp dụng tốt nhiều quy trình sản xuất đóng vài trị phương pháp tiếp cận có hệ thống hiệu Luận văn tiến hành nghiên cứu lý thuyết liên quan đến Six Sigma, phân tích trạng dây chuyền lắp ráp pin, xác định nguyên nhân ảnh hưởng đến chất lượng suất, lập kế hoạch thực cải tiến dây chuyền lắp ráp theo chu trình DMAIC Kết quả: - Mức sigma dây chuyền sản xuất tăng từ 3.95σ lên đến 4.12σ - Năng lực sản xuất dây chuyền tăng từ 76 lên 81 sản phẩm/giờ - Tỉ lệ đáp ứng kế hoạch sản xuất tăng từ 88% lên 96% Ý nghĩa thực tiễn: Giảm tỉ lệ lỗi dây chuyền sản xuất nâng cao suất dây chuyền Làm sở tham chiếu cho việc triển khai đến dây chuyền khác cơng ty Luận văn ví dụ ứng dụng giải pháp Six Sigma vào trình lắp ráp pin doanh nghiệp v DECLARATION OF AUTHORSHIP I hereby declare that this thesis with topic “Application of six sigma methodology in battery assembly line to improve quality and productivity” was carried out by myself and the work contained and the results in it are true by author and have not violated research ethics The data and figures presented in this thesis are for analysis, comments, and evaluations from various resources by my own work and have been duly acknowledged in the reference part I will take full responsibility for any fraud detected in my thesis Ho Chi Minh City, December 18, 2022 Nong Ngoc Vu vi TABLE OF CONTENTS MASTER’S THESIS ASSIGNMENTS ii ACKNOWLEDGEMET iii ABSTRACT iv TÓM TẮT LUẬN VĂN .v DECLARATION OF AUTHORSHIP vi TABLE OF CONTENTS vii LIST OF FIGURES x LIST OF TABLES xiii LIST OF ABBREVIATIONS xiv CHAPTER 1: INTRODUCTION .1 1.1 Problem statement 1.2 Research objectives .3 1.3 Thesis objectives 1.4 Thesis structure CHAPTER 2: THEORETICAL BASIS AND LITERATURE REIVEW 2.1 Definition .5 2.1.1 Six Sigma 2.1.2 Benefits of Six Sigma method 2.1.3 DMAIC cycle 2.1.4 Sigma level calculation 2.1.5 Quality management tools 2.1.6 Line balancing by Takt time 12 vii 2.2 Related research 13 2.3 Methodology 14 2.3.1 General methodology 14 2.3.2 Detailed methodology 14 CHAPTER 3: DEFINE PHASE .16 3.1 About TTI company 16 3.1.1 Introduction 16 3.1.2 Mission, value, quality 16 3.1.3 Products 18 3.1.4 Battery product and production 18 3.1.5 Battery assembly process 22 3.1.6 SIPOC chart 28 3.1.7 Define phase 28 CHAPTER 4: IMPLEMENT SIX SIGMA DMAIC 35 4.1 Measure .35 4.2 Analyze 36 4.2.1 Welding Failure 37 4.2.2 Pack Voltage Fail 40 4.2.3 Gap between demand and actual output 43 4.3 Improve 44 4.3.1 Improvement plan 44 4.3.2 Improvement deployment-Quality 47 4.3.3 Improvement deployment- Productivity 65 4.3.4 Improvement Assessment 68 viii 4.4 Control 72 4.4.1 Monitor the control chart and failure 72 4.4.2 Check sheet 72 4.4.3 Solutions are documented 73 CHAPTER 5: CONCLUSION AND SUGGESTION .74 5.1 Conclusion and discussion 74 5.2 Suggestion 74 REFERENCES 75 CURICULUM VITAE .77 EDUCATION PROCESS: 77 WORKING HISTORY: 77 ix DMAIC IMPLEMENTATION The capability plot created for High Star supplier as shown in Figure 4.26 proved that the CPK of High Star supplier is 1.1 which are not a good number and the data spread is wider than Lishen supplier Figure 4.26: Process Capability for High Star supplier at sorting station Function test station At function test station, all the material inputs are assembled and processed The function test would check the items belong to performance and function of the battery Since the pack voltage failure is critical at this station Even the battery cells are sorted at the sorting station, but we would like to check how the pack voltage are distributed by the suppliers The Figure 4.27 showed that by using the cell of Lishen supplier, the pack voltage response is in statistic control by looking the I chart, there is no need to eliminate special causes in this data set The normality plot has p value greater than 0.05 mean the voltage data is following normal distribution The histogram is showing it is spread narrowly which are good The capability plot showed the CPK value of 1.31 if using Lishen cell It is proved that the pack voltage response get CPK value of 1.31 which are acceptable if using the Lishen cell 63 DMAIC IMPLEMENTATION Figure 4.27: Process Capability for pack voltage at function test by using Lishen cell The Figure 4.28 showed that the pack voltage response is stable in the I chart, there is no need to eliminate special causes in this data The normality plot has p value greater than 0.05 mean the voltage data is following normal distribution So it is acceptable to evaluate the process capability The histogram is showing it is spread wider compared with Lishen supplier The capability plot showed the CPK value of 0.85 which are not acceptable if using High Star cell It is not a prefer CPK number for capability Figure 4.28: Process capability for pack voltage at function test by using Highstar cell 64 DMAIC IMPLEMENTATION Conclusion for supplier capability By having the capability analysis at sorting station and function test station, we see that the pack voltage is not in a good distribution by using the High star cell Compared between Lishen supplier and High star supplier, it is proved that High start cell causes a low CPK value for cell voltage at sorting station and low CPK value for total pack voltage at function test station Lishen cell contributes a good CPK value There is a request send to AES team and SQE team to work with High Star supplier to improve the production process And there is a request to AES team and Sourcing team to prioritize for buying the Lishen cell supplier 4.3.3 Improvement deployment- Productivity a Improve fixture at labeling station at station At the labeling station, the operator needs to manually stick the label without any support from tool It is decided to have a improvement for the tooling A fixture is created to support the operator doing faster There was a reduction of 1.7 seconds cycle time from station by having the actions shown in the Figure 4.29 the changes of cycle time can be seen in the Figure 4.34 Before After Hold the battery pack and paste total label around the pack It is required operator to paste each label per area while rotating the back by hand There is fixture easy to rotate and lock Operators paste each label, rotate fixture and paste labels Work is faster by having the support from fixture Figure 4.29: Improve fixture at labeling station 65 DMAIC IMPLEMENTATION b Improve the scanning process at station At the function test station, there is requirement for scanning the barcode on the battery pack By having the barcode of battery, the machine can proceed to test the function The manually scanning task is taking time so it is embedded into the machine This improvement can reduce 1.2 seconds cycle time from station Action is described in the Figure 4.30 The changes of cycle time can be seen in Figure 4.34 Before After Operator the below task having the scan by manually Eliminate the manually scanning task Machine already automatically capture the barcode during testing Figure 4.30: Improve the scanning process c Redistribute task between stations After having some improvement on the line as previous section The next step is to redistribute task between stations All the tasks were reviewed and redistributed to have the improvement as Figure 4.31 Those actions can cut seconds from the bottle neck stations Some tasks from station would be moved to station (bottle neck) to reduce the bottle neck cycle time The changes of cycle time can be referred in the Figure 4.34 66 DMAIC IMPLEMENTATION Before In the below description After Move task from station to station to reduce the workload of station Figure 4.31: Redistribute task between stations 67 DMAIC IMPLEMENTATION 4.3.4 Improvement Assessment a Completion date After having the improvement completed, the completion date are recorded in the Table 4.16 it is important to monitor the results after improvement which described in the next section Table 4.16: Completion date for actions # Defect type Improvement plan Completed on Welding Failure Gemba and define critical point of alignment, update to PM check list 8-Sep-22 Welding Failure DOE study, update setting form 29-Sep-22 Welding Failure Set up the grinding by automation set the frequency of grinding 27-Sep-22 Pack Voltage Failure Improve the fixture cover PCBA 25-Sep-22 Pack Voltage Failure Standardize the cleaning process after soldering, update to work instruction 2-Sep-22 Pack Voltage Failure Grove the solder wire to reduce the solder ball created 23-Sep-22 Pack Voltage Failure Soldering tip is replaced daily 5-Sep-22 Pack Voltage Failure Alignment task is added to daily check list 17-Sep-22 Check and replace the test probe when pm time Pack Voltage Failure CPK to analyze the cell supplier 16-Sep-22 Do line balancing and reduce bottle neck by finding improvement opportunity 21-Sep-22 10 Gap between demand and actual output 68 DMAIC IMPLEMENTATION b Sigma level and DPMO improvement The Figure 4.32 show how the DPMO is going down from Aug to Nov 2022 The actual DPMO is 6933 in Aug 2022, it is only 3982 in Nov 2022 The improvement plan was done at the end of Sep 2022 There is a reduction of DPMO since the improvement completed Figure 4.32: DPMO after improvement The improvement of sigma level is shown in the Table 4.17 There was an increasement of overall sigma level from 3.95 to 4.12 after improvement, DPMO is reduced to 4443 in Oct-Nov 2022 Table 4.17: Sigma level improvement Sigma level calculation Total of number units produced Total defects Number of opportunities DPMO Sigma level Before improvement May-Aug 2022 After improvement Oct-Nov 2022 209528 25637 17 7197 3.95 110055 8312 17 4443 4.12 69 DMAIC IMPLEMENTATION c Control chart after improvement The control chart for defects is built and compared in the Figure 4.33 It can be seen that the new process after improvement has higher capability in controlling the defects In the new control chart, there is a reduction of failure from September to October, the failure is going down in a good trend after improvement taken in September The previous control chart in July and August is sometimes go beyond the UCL which showed that the process before improvement is not in well control and affected by special causes The number of defects accounted for 0.79% of number inspected battery pack in August, but it is just 0.65% in Oct Before After Figure 4.33: Control chart assessment d Productivity after improvement The line balancing improvement is shown in the Figure 4.34 the data showed the current line balancing ratio is just 84% which increased to 89% after improvement The output capacity of the line increased to 81 pcs/h from 76 pcs/h 70 DMAIC IMPLEMENTATION Before After Line of Ballance: 84% Maximum output per hour: 76 pcs/h Line of Ballance: 89% Maximum output per hour: 81 pcs/h Figure 4.34: Productivity improvement The attainment of plan is 96% in November 2022 compared to 89% August 2022 The attainment of plan by month is shown in the Figure 4.35 there is an increasement of the attainment ratio from Sep when the improvement is completed Improvement completed in this month Figure 4.35: Attainment of the plan 71 DMAIC IMPLEMENTATION 4.4 Control 4.4.1 Monitor the control chart and failure The control chart is being monitored by the quality engineer as Figure 4.36 and to track the monthly rejection/ rework The u chart of defects in September is intended to go down after improvement It is proved that the failure is reducing to 0.06%, it means that the number of defects accounted for 0.06% number of inspected battery packs The failure ratio is also in statistic control because there is no any point out of 3σ limit The u chart is using by quality department to observe and react The u chart is used instead of c chart because the sample size varies by day Figure 4.36: Control chart to be monitored 4.4.2 Check sheet Some check sheets would be used to check and ensure failure are to be continued recorded, all the parameters and standard work were followed in the production The Table 4.18 show the check sheets are used in the factory All of the tasks were described in the improvement phase would be add into the check sheets to maintain the improvement 72 DMAIC IMPLEMENTATION Table 4.18: Check sheet No Check sheet type Frequency Department Check sheet for recording failure Online Production Every shift Manufacturing in production line, keep following the status of failure Check sheet to perform and complete machine daily task Check sheet to ensure engineering Every shift production follow standard work In Process Quality Control instruction and parameters are set same as setting form 4.4.3 Solutions are documented - The SOP for improvement is updated and to be controlled by Document Control Center department to make sure the SOP used in the line is latest and has official stamp - All the solutions are updated to check list, PM instruction… as mentioned in the section 4.3 to make sure all parameters, tasks, check items are documented and be followed in future 73 CONCLUSIONS AND SUGGESTIONS CHAPTER 5: CONCLUSION AND SUGGESTION 5.1 Conclusion and discussion The project focus on application of DMAIC methodology in the battery assembly line to improve quality and productivity In around months, the project is carrying out The thesis researched knowledge of Six Sigma methodology and defined the status of productivity and quality in the battery assembly production line, DMAIC methodology is applied in the battery assembly line to improve quality and production in the battery assembly line The results are recorded and assessed Some results are listed as below: - Sigma level of overall production line improved from 3.95σ to 4.12σ - DPMO reduced from 7120 in July to 3982 in Nov 2022 - Production output capacity increased from 76 pcs/h to 81 pcs/h - Production output attainment of plan increased from 88% in Aug to 96% in Nov 2022 5.2 Suggestion The project is successful in battery assembly line Based on this experience and reference, the project can be applied to other product line in the company Increasing the scope of the project to other area can increase more value of project by improving quality and productivity in other production area of the company The sigma level reached 4.12 but it can be improved by continuing the DMAIC cycle and focus on the remaining defects Since the thesis focused only on top defects which are welding failure and pack voltage failure The control activity needs to be maintained as mentioned in the control phase The schedule attainment is 96% even reached the target of the project but this number is not perfect which needs to improve more to meet the demand in the company The project still needs to focus more on closing the gap between demand and the actual output To so, the suggestion is to perform more deeply measurement and investigation on the gap between demand and the actual output 74 REFERENCES [1] "Battery: Global Strategic Business Report." Internet: https://www.researchandmarkets.com/reports/5303140/battery-globalstrategic-business-report, Nov 25, 2022 [2] D Pohekar and R S Reosekar, "Six Sigma methodology: a structured review," International Journal of Lean Six Sigma, vol 5, iss 4, pp 392 422, 2014 [3] J Antony et al., "Six Sigma in service organisations: benefits, , challenges and difficulties, common myths, empirical observations and success factors," International Journal of Quality and Reliability Management, vol 24, no 3, pp 294-311, 2007 [4] M J Harry, The Vision of Six Sigma: A Roadmap for Breakthrough, Sigma Publishing Company, 1998 [5] S Nataraj and M Ismail, "Quality enhancement through first pass yield using statistical process control," International Journal of Productivity and Quality Management, vol 20, no 2, p 238–252, 2017 [6] D A Desai et al., "Reducing failure rate at high voltage (HV) testing of insulator using Six Sigma methodology," International Journal of Productivity and Performance Management, vol 67, no 5, pp 791-808, 2018 [7] P A D A Marques and R Matthé, "Six Sigma DMAIC project to improve the performance of an aluminum die casting operation in Portugal," International Journal of Quality & Reliability Management, vol 34, no 2, p 307–330, 2017 75 [8] L D Tran, "Cải tiến chất lượng chuyền lắp ráp thiết bị âm theo quy trình DMAIC," Master thesis, Ho Chi Minh University of Technology, 2020 [9] N Q Thai, "Nghiên cứu ứng dụng Lean Six Sigma hế thống dịch vụ công ty TNHH MAERSK Việt Nam," Master thesis, Ho Chi Minh University of Technology, 2011 [10] F W Breyfogle, Implementing Six Sigma, John Wiley & Sons, 2003 76 CURICULUM VITAE Full name: Nong Ngoc Vu Date of birth: March 24, 1996 Place of birth: Binh Contact address: Dinh Hoa complex department, Quarter 8, Thu Dau Mot city, Binh Duong province EDUCATION PROCESS: • From 2014-2018: Student, majoring in Mechatronics, Faculty of Mechanical Engineering, Ho Chi Minh City University of Technology • From 2020-2022: Postgraduate Student, majoring in Industrial Engineering, Faculty of Mechanical Engineering, Ho Chi Minh City University of Technology WORKING HISTORY: • From August 2018 to October 2020: Manufacturing process staff, First Solar Vietnam Manufacturing Co., Ltd • From October 2020 to present: Senior industrial engineer, Techtronic Industries Vietnam Co., Ltd 77