Available online at www.sciencedirect.com ScienceDirect Procedia CIRP 0 (06 ) 7 th Global Conference on Sustainable Manufacturing - Decoupling Growth from Use Lean line balancing for an electronics assembly line Nguyen Thi Lam, Le Minh Toi, Vu Thi Thanh Tuyen, Do Ngoc Hien* Department of Industrial Systems Engineering, Hochiminh City University of Technology, Hochiminh City, Vietnam * Corresponding author. Tel.: +08-09-666-006; E-mail address: hienise97@hcmut.edu.vn Abstract Line balancing is required in most of production lines, but bottleneck point often happens. As the results, many wastes would be occurred. There are many methods or tools to balance the line as well as eliminate wastes. In this paper, a lean line balancing would be studied as a simple tool, but impressive results would be brought. It would be applied in improvement of an electronics assembly line. Analysis on the current line would be done to figure out wastes and conceive the ideas to solve them. The quality of production line would be shown on the productivity, line balancing index, and effectiveness on resources. Actually, many benefits for the studied electronics assembly line were brought, which could be considered as a force to apply lean line balancing tool for other production lines. 06 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license Peer-review (http://creativecommons.org/licenses/by-nc-nd/.0/). under responsibility of the International Scientific Committee of the th Global Conference on Sustainable Manufacturing. Peer-review under responsibility of the International Scientific Committee of the th Global Conference on Sustainable Manufacturing Keywords: Lean line balancing; assembly line; Line balancing; Takt ; Lean manufacturing. Introduction Most electronics assembly companies pay much attention on reducing cost as well as enhancing customer value. takes in many forms and it should be eliminated. Lean manufacturing could prove effective for driving waste out of manufacturing process. Continuous improvement is required to create more value for customers with fewer resources. Transformation of the traditional assembly line to a lean one is a good solution to improve efficiency, effectiveness and profitability []. Assembly line is popular in manufacturing industries such as electronics, textile, or furniture [,, ]. However, bottlenecks are often occurred because the assembly line is difficult to get balancing, which would bring many wastes such as waiting, work in process (WIP), and overproduction []. Therefore, a lean line balancing could support the WIP smoothly flows through the line with minimal (or no) buffers between steps of assembly process []. Lean line balancing has been done in many industries []. Many forms of wastes such as inventory, waiting, and transport are eliminated. The studied electronics assembly line could meet customer requirements, but it was not considered as an effective line in terms of low productivity, resources efficiency, and many wastes. Therefore, the target of research project is to enhance the operation effectiveness of the line.. Methodology Line balancing is a technique to minimize imbalance between/among workers and workloads in order to achieve required run rate [, ]. Therefore, the line should be analyzed in terms of assembly process, s layout, and cycle. A multiple activity chart is used to measure the cycle at the with cooperation between an operator and machine, which is known as the operator machine chart [6]. Besides, jobs at the should be separated and analyzed in detail to figure out which one could be improved. Takt, an average unit production needed to meet customer demand, is calculated [7]. Described mathematically, Takt is available for production/required units of production a day or a period. There are two required quantities: D = Average daily customer demand for the item. W = Total available working per day, in seconds. Therefore, Takt = W / D in seconds per item () -87 06 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/.0/). Peer-review under responsibility of the International Scientific Committee of the th Global Conference on Sustainable Manufacturing doi:0.06/j.procir.06.0.089
8 Nguyen Thi Lam et al. / Procedia CIRP 0 ( 06 ) 7 The line balancing chart would be drawn to figure out the bottleneck points on the line. The ideas to improve the line would be conceived. In the next step, the bottleneck would be analyzed and focused to improve first. The value-added and non-value-added activities would be identified [, 6]. The suitable tools such as multiple activity chart, Ishikawa chart, and activity analysis table would be used to find out reasons and alternatives to enhance the line. Besides, operator comments on the operations would be collected, which are good information to improve the layout. The improvement alternatives would be designed and evaluated to optimize the used resources, eliminate or reduce wastes, as well as enhance the productivity. In addition, line balancing factors would be calculated and evaluated.. The electronics assembly line The electronics assembly line has four main s in the assembly process including Inline Loading Program (ILP), Function Verification Test (FVT), Final Inspection (FNI) and Pack out. The assembly process is summarized on Fig. Fig. Operation flow chart of studied assembly line The line layout is designed as the U-shape as shown on Fig. The process flow begins at the ILP and finishes at the Pack out one. Each has one operator to process all required tasks. Fig. Layout of electronics assembly line Fig. assembly process The frames were moved to buffers before and after s for waiting to be processed. The total transport fills a meaning ratio of the cycle. In addition, waiting between s is often long. As a result, unvalued is easy to recognize larger than value added one. The transport flow chart of the piece through the electronics assembly line is shown on the Fig. The Inline Loading Program-ILP has one operator and two fixture machines. They operate independently, in which each fixture machine can input required data for two the electronics s at the same. Operator process includes opening the fixture machine, locating the in the machine, waiting for inputting the data, moving the out and moving them to the next. The ILP process is summarized as in Table.
Nguyen Thi Lam et al. / Procedia CIRP 0 ( 06 ) 7 9 Table. Operation process at the ILP ILP-Inline Loading Program Table. Operation process at the FNI FNI Workstation picture Workstation picture: Operation description Operator Machine Locate the in the fixture machine and close machine cover. Input the data and report the result. Open machine cover If the report of the result is fail, the is moved to the debug. A red sticker note is pasted on it. Transport the to the FVT if it is passed. The Function Verification Test-FVT has one operator controlling independent fixture machines. Each machine can only test one at a. The operator has to open the fixture machine, locate the in the machine, as well as wait the machine testing inputted program. If the machine reports the green light, the is passed. If it reports the red light, the is fail. It would be transported to the next suitable. The FVT process is summarized in Table. Table. Operation process at the FVT Workstation picture: 6 Operation description Locate the in the testing machine frame Push and close the testing machine frame Test the and report the result. Pull the testing machine frame out. Transport the fail to the debug and paste the red fail note on it. Transport the passed to the FNI. FVT Operator Machine The Final Inspection-FNI has one operator checking appearance. There is a standard form using to make a comparison. A guideline of how to process is shown in Table. Operation description Operator Locate the standard form on the. Check the item Check the appearance quality. Check the lower CLD pad plate Input the barcode in the MES system. If test result is fail, - Paste an error note on the - The error information 6 is recorded in the MES system. - The error is transported to the rework station. If the test result is good, 7 the is transported to the Pack out workplace. Machine The Pack out has one operator packing the. The operator activities includes picking up the, collecting the ESD cover, putting the into the ESD cover, and packing as well as locating it in the box. Each box can handle 8 packed s. The pack out process is summarized in Table. Table. Operation process at the Packout Workstation picture: Packout Operation description Operator Machine Locate the artificial sponges to the box. Locate the slots in the box Pick up the and scan information (barcode) in the MES system. Fix the in the cover P/N JBAG008 - NE Fix the packed in the box. 6 Locate the artificial sponges to box upper side when there are completed s. 7 Close the box cover and stick a note on it. 8 Move the box to the stack in the OBA place.
0 Nguyen Thi Lam et al. / Procedia CIRP 0 ( 06 ) 7 After the operation process was analyzed, the operator value-added and/or non-value-added activities were identified for every. At each, all operations processing cycle were collected. Besides, operations would be classified into valueadded or waste activity. They are summarized as following Tables. Table. Operator value-added and non-value-added activities at the ILP Name of Workstation: Operation description Locate the in the fixture machine and close machine cover. pieces pieces 8.00.0 Scan offline.00. Observing the inputting data.00.7 process and reporting the result. Open machine cover and then.00.0 move the to the next suitable Exchange tray 0.70 trolley and exchange tray to tray 68.00 7.70 Table 6. Operator value-added and non-value-added activities at the FVT FNI Activities Name of Workstation: FVT-Function Verification Test pieces pieces Activities Operation description Pull the 0.6. testing machine frame; Locate the in it; Push the testing machine frame; And transport the tray to the FNI buffer. Scan offline 8.00 9.0 Observe the 0.68.67 inputting data program process 69. 7. Table 7. Operator value-added and non-value-added activities at the FNI Table 8. Operator value-added and nonvalue-added activities at the Packout Operation description Operation description Pick up the and scan information (barcode) in the MES system. Fix the in the cover P/N JBAG008 - NE Packout Activities ILP-Inline Loading Program Activities pieces The distribution of cycle at each was shown on Fig, in which the waste is mainly occurred at the ILP and FVT s. The percentage of the waste of the line around.8%. Actually, there are many factors affecting to the line productivity, which relate to manufacturing environment, human factor, suddenly activities, and machine broken down. The added coefficient was analyzed [7] and identified as summary in Table 9. pieces Use two hand move the.00 tested to the pack out and pick up another one from the buffer tray to test. Check the appearance.0 quality. Scan the barcode to the.00 MES system 0.0.00.00 Pack the mother board.60 Fix the packed.00 in the box..60
Nguyen Thi Lam et al. / Procedia CIRP 0 ( 06 ) 7.. Combination of ILP and Pack out s The ILP operator was considered to assign more workload for the Pack out one because the total processing is still less than the Takt. Operator processes include locating the in the fixture machine at the ILP, transporting to the Pack out, packaging good s, and then transporting to the ILP to remove the out of the machine. The summary of cycle at each is shown in Table 0, in which all of them are less than required Takt. The number of s is reduced from to, and operators could complete all jobs of the line. Table 0. Summary of the cycle at each Fig. Workstation cycle in seconds Takt Table 9. Added coefficient Added coefficient % Line characteristics Personal demand Basic relax Company regular Importantly, the customer demand around 600 s a month should be fulfilled; there is around 6 working days a month; and the company works shifts a day ( hours a day). Therefore, Takt equals: = 8.08 seconds/product. The production line capacity could meet the customer demand because all cycle s is lower than Takt. As a result, waste of resource (human resource) happens. The Pack out productivity is too large than required one. Some factors to evaluate the line are calculated as followings: Balancing line ratio equals = 8.% Number of required operators equals =. operators Line balancing efficiency equals = 6.%. Improvement alternatives The job is normal and working environment conditions are normal. Suddenly factor Not serious or normal Machine 8 Normal and in control. Total 0 The line capacity can meet customer demand, but there is large waste in human resource especially in Pack out. In addition, at the ILP and FVT the operators have to wait while the machines run. s were considered to reduce as well as eliminated as following alternatives. Therefore, ILP & PACK. 8.0 Sec/pc FVT 7.0 8.0 Sec/pc FNI 0.0 8.0 Sec/pc Line balancing ratio equals = 9.%; Line balancing efficiency equals = 70.7%; The percentage of the waste of the line is reduced from.8% to.%; However, the operator working at the ILP-Pack out is more than 8% (./8.0) cycle.. Combination of ILP and FVT s A software to read the barcode automatically for the FVT needs to be invested, which costs around 800USD. An operator has to do jobs of the ILP and FVT s. The operator processes include locating the in the ILP fixture machine, transporting to the FVT, testing four s, transporting back to the ILP, removing out the completed and moving it to the next station. Similarly, the summary of cycle at each is shown in Table, in which all of them is still less than required Takt. The number of s is reduced from to, and operators could complete all jobs of the line. Table. Summary of the cycle at each Takt ILP & FVT.90 8.0 sec/pc FNI 0.0 8.0 sec/pc PACKOUT.60 8.0 sec/pc
Nguyen Thi Lam et al. / Procedia CIRP 0 ( 06 ) 7 Therefore, Line balancing ratio equals = 80.89%; Line balancing efficiency equals = 68.8%; The percentage of the waste of the line is reduced from.8% to 0.%; However, the operator working at the ILP-FVT is still around 8% (.90/8.0) cycle. Three alternatives were considered: The current line, ILP-Pack out combination, and ILP-FVT combination alternative. Many criteria were used to evaluate them as shown in the Table. The suggested alternatives were better than the current one in terms of line balancing index and unit per hour per person one. In addition, twenty five percent of human resource were reduced; and overall labor effectiveness index is increased in both suggested alternatives. Currently, the option has been applied due to without investment more. However, the ILP-FVT operator worked most full. It is not good for a long. Therefore, option would be invested in the near future. Table. Summary of alternatives results Note: - HC: Human Capital (person) - LBI: Line Balancing Index (%) - OLE: Overall Labour Effectiveness (%) - UPH: Unit per Hour (product/hour) - UPPH: Unit per Hour per Person (product/hour). Conclusions The quality of the electronics assembly line was enhanced in terms of line balancing index, overall labor effectiveness, productivity and elimination of wastes. Although human resource was decreased %, the customer demand could meet. This research shows that there are many wastes which could be eliminated with the simple lean tools. It is not very complicate but it would bring essential benefits. After the line is balanced, standardization of works should be done. The guideline should be developed in detail for training and assuring the quality of jobs. Other lean tools such as S, Kaizen, or TPM should be studied, which could support setting up the lean environment for the company. References [] Le Ngoc Quynh Lam, Do Ngoc Hien, Nam Ki-Chan, An Implementation of Lean Technology in an in-plant Manufacturing System, a Funiture Company, Applied Mechanics and Materials, 0, Vols. 0-6, pp 799 807. [] Le Ngoc Quynh Lam, Do Ngoc Hien, Nam Ki-Chan, Modeling and simulation of a lean system. Case study of a paint line in a furniture company, International Journal of Management Research and Practice (MRP), 00, Volume, Issue, September 00, pp. 8-98. [] Tran Minh Canh, Le Thi Diem Chau, Duong Kim Ngan, Huynh Binh Song Oanh,Phan Thi Ngoc Thoa,Tran Chi Thac, An application of simulation in line balancing: A case study in Whittier woods furniture Vietnam company, Proceedings of the th International Conference on Industrial Systems Engineering & Logistics (ICISEL ), 0, Ho Chi Minh - Việt Nam [] Tran Minh Canh, Duong Kim Ngan, Ngo Hieu Loc, Do Ngoc Hien, Application of lean line balancing for Oral plant of Unilever Vietnam, Proceedings of the th International Conference on Industrial Systems Engineering & Logistics (ICISEL ), 0, Ho Chi Minh City, Vietnam. [] Ronald G.Askin and Jeffrey B.Goldberg, Design and analysis of lean production system, ISBN 978 0 7-9-9. Wiley, New York, 00. [6] Benjamin nibel & andris freivalds, Methods standards & work design, McGraw Hill, 999. [7] James P.Womack and Daniel T.Jones, Lean Thinking, ISBN 978 0760, Free Press, 00.