Integration of Seven Managements and Planning Tools and DMAIC: A Case Study in a Semi-Automated Production Line

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1 International Journal of Emerging Technology and Advanced Engineering Integration of Seven Managements and Planning Tools and DMAIC: A Case Study in a Semi-Automated Production Line Low Shye Nee 1, Lau Joo Hao 2, Nadiah Mohd Shukor 3, Mohd Rizalazlim Adzmi 4 and Shahrul Kamaruddin 5 1,2,3,4,5 School of Mechanical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300, Nibong Tebal, Pulau Pinang, Malaysia 1 low_sn@yahoo.com 5 meshah@eng.usm.my Abstract The objective of this study was to present a process improvement framework to eliminate the lean seven wastes. The framework is needed as a guideline to assists the industrial practitioners in improving the production process performance with suitable tools. The framework developed based on DMAIC methodology. It used to priority the problem scopes and then selects the solutions from various options. To test its application, the framework had been validated in a semi-automated production line. The result shown that 50% reduction of manpower the, while maintain the production. The case study shows how developed framework provided a systematic approach into identification of the solutions and achieves the desired performance improvement. Keywords lean seven waste, six-sigma, DMAIC, process improvement, semi-automated, case study. I. INTRODUCTION Continuous improvement has always been an endeavour of manufacturing companies. The aim of continuous improvement is to eliminate wastes by making production lines more efficient and responsive to the market need. Waste is defined as actions that do not add value to a product and can be eliminated [1]. Hence, principles of lean manufacturing had addressed the seven wastes classification as below: Overproduction producing more parts than necessary was waste. Transportation excessive movement and handling can cause damage and are an opportunity for quality to deteriorate was waste. Movement - unnecessary human movement was waste. Re-work quality defects resulting re-work was waste Unnecessary processing energy that expended by workers or machine to accomplish work does not add value to the product was waste. Inventory there are leftover parts that must be stored was waste. Waiting whenever parts are not moving or being processed or operators were forced to wait are waste. The reduction of production wastes was defined as the fundamental thinking behind lean manufacturing and, as a result, an analysis of such wastes is needed in order to effectively reduce or eliminate it. In order to solve the wastes, a structure of process improvement methodology is needed, such as Six Sigma methodology: Define, Measure, Analyse, Improve and Control (DMAIC) process. Sixsigma is a common continuous improvement methodology that is widely used in manufacturing. The six-sigma methodology is a well ordered and structured approach used to enhance process performance and achieve high quality and low variability level [2]. Performance improvement strategy in six-sigma aims to reduce the quality level to as low as 3.4 defective parts per million [3]. Mehrjerdi [4] stated that the concept of six-sigma is a process that can improve the effectiveness and efficiency of all operations dramatically by understanding the relationships between the inputs and the metrics of the defined the quality of a process. Six-sigma can benefit manufacturing companies that performed repetitive processes because it is easy to track the flow of goods along the processes. One way to increase the performance of continuous improvement is by using the lean tools to 311

2 International Journal of Emerging Technology and Advanced Engineering identify key areas that can be leveraged by six Sigma methodologies. Souraj [2] proposed a methodology which integrated the lean tools, value stream mapping with DMAIC approach in a continuous improvement study. However, there was lack of the process improvement works focusing on eliminating the production wastes from the DMIAC methodology point of view. Therefore, there is a need to develop an integration framework of other tools in the six-sigma methodology for eliminating the production wastes. This paper presents the process improvement framework based on six-sigma methodology in eliminating the seven wastes identified by lean manufacturing. The framework is an integration of seven managements and planning tools and DMAIC. The framework is then implemented to identify and eliminate the lean seven wastes on a production line under the continuous improvement project of the case study company. II. PROCESS IMPROVEMENT FRAMEWORK The process improvement framework used in this paper consists of five stages that are crucial for dealing with the stages of the production waste identification and elimination. In adopting the DMAIC concept, it will give the magnitude to process of defining, measuring, analysing, improving and controlling a process for achieving a better product and process quality. In addition the stages of the framework helps in providing a logical sequence for the seven managements and planning tools and DMAIC concept by sufficient repackaging of the tools and concepts to reduce the production wastes. Moreover, the stages of the process improvement framework need to be completed at each phase until the conclusion of each phase before moving to the next. The summary of each stage that show the task and the adoption of tools respectively are shown Figure 1. Define: This phase aims to prioritize opportunities for improvement by quantifying any production wastes. The problem is stated based on the observation through the processes on the production line. Measurement Phase: This phase intended to define all the details of the processes on the production line. In order to identify the problems, time study technique is applied. A time study could point out possibilities of motions and times required for each task to perform. An equation to measure the process efficiency is applied for calculating the operator and machine efficiencies. 312 Analyse Phase: This phase intended to outline all the possible causes of the problem. Few techniques from the seven management and planning tools are applied, such as Prioritization Matrix and Relationship Matrix and Fishbone diagram. FIGURE 1: DMAIC FRAMEWORK Phases Tasks Tools adopted Define Definition problem 1. Brainstorming statement and objectives technique Measure Determination of process inputs and s are accomplished during this phase. (Eg. current process flow; overall efficiency; productivity) Analysis Identification and verification the critical inputs that affect to the process. Improve Suggestion of improvement on the solutions of root causes to the problem. Control Implementation and monitoring of the solutions. 2. Interview 1. Time study 2. Motion study 1. Seven Wastes classification 2. Prioritization matrix 3. Relationship Matrix 4. Fish Bone Diagram 1. Prioritization matrix 2. Relationship Matrix 1. Control systems- Check Sheet Improvement Phase: Team is assemble for brainstorming sessions to generate and identify possible solutions, select the best solutions (based on analysis), and design implementation plan. Control Phase: The control phase focused on monitoring, checking, and assessing the process improvement tasks until the problem and production wastes is solved and eliminated to meet the objectives of the process improvement project. III. CASE STUDY Company X is providing a vertically integrated manufacturing service for products comprising of electronic sub-assemblies and plastic moulded enclosures and components. The area for this study in Company X consists of four production lines, in which the shop floor area concern consists of 67 units of injection moulding machines. Each workstation requires a floor space of 250 ft 2 and the number of worker includes direct labour and indirect labour, staff, and management is over 100

3 International Journal of Emerging Technology and Advanced Engineering employees. The major customers for Company X are the telecommunication companies. In completing the continuous improvement project, the management of Company X has identified one of the production line to kick starts the project. the production line selected produces plastic housings for the usage of telecommunication product. The production line is a semiautomated line that uses a man-machine system. It consists of de-gating and labelling workstations. The workstations are connected with an injection moulding machine attached to a robotic arm. Robotic arm transfers the injected parts from the injection machine to workstation. Figure 2 shows the production line layout. problems that they are facing during their working hour. Hence, gaining important details of the problems that need to be highlighted is crucial in determining the problem statement and objectives that need to be derived. Problem statement: The de-gating and sticking processes are done manually. The problem with processing manually is that the cycle time for each working station is not consistent and varies. Inconsistent of time for each task will cause waiting or starving condition to occur. Based on the observation, there are a few problems which influences the cycle time at each working station. FIGURE 2: CURRENT PROCESS LAYOUT inventory i. Excessive operator in one workstation ii. Frequent tools (cutting and de-gating) changeover iii. High occurrence of defect due to wrong labelling Operator 2 Operator 1 Sticking process Degating process Robotic arm Injection machine The workstation produces approximately 180 pieces per hour. It requires two operators to run in eight hours shifts (1 production day requires 3 shifts). The quantity of parts produced is based on the customer s order. Once the management has agreed upon to embark on the journey of process improvement, the project will kick start with the first stage that is define phase and followed by each phase once each of the phases achieved it characterise goals. A. Define Phase This phase determines the problem statement and objective in this study. Brainstorming technique is used to generate the problem statement that describes the problem faced on the production lines. Another method used was interviewing the operators and technicians regarding their 313 Objectives: i. Reduce Operators ii. Optimise the utilization of operator By deriving the problem statements and objectives of the continuous improvement project it will give a clear insight of the achievement and target for the next following phases. B. Measure Phase This phase consists of categorising the process flow, detail work operation, data collection, and assessment of the current level of process efficiency. Using the time study approach to measure the time required to perform a given task of each operator from the operator taking out the finish part, de-gating process, and labelling process. This approach uses direct and continuous observation of the task, using a timekeeping device such as stopwatch, and video camera to record the time taken to accomplish a task by the operator. The data that has been collected is tabulated in Table 1. Operation Cycle time (s) TABLE I PRODUCTIVITY OF OPERATION % work load Units outp our/ hour Hour/ unit Units /h our line balance Hour per unit line balance Injection Degating Labeling

4 Operation Cycle time (s) International Journal of Emerging Technology and Advanced Engineering % work load Units outp our/ hour Hour/ unit Units /h our line balance Hour per unit line balance By using the equation from Fred et al. [5], the rate of production line efficiency can be calculated for the current level of process as shown as follows. From the calculation, the current overall efficiency is 78.26%. This shows that for each cycle of the parts produced from the injection machine, the utilisations of the operators are 78.26%. The idling time of operators is 21.74% based on the cycle time of injection moulding machine. (1) 2 first piece of part again Place it into container Take the sticker and stick it on the part Take the sticker and stick it on the part Take the sticker and stick it on the part Remove the scrap of part Take and hold part from container Vision inspection Place the part into container that inside the carton Take and hold part from container Vision inspection Place the part into container that inside the carton Take and hold part from container Vision inspection Place the part into container that inside the carton From the time study, the list of motions for right-hand and left- hand for carrying out the tasks and average cycle time for each work element that been done by the two operators, are tabulated. The aim of the time study is to establish the standard time for a qualified worker to perform specified work under stated conditions. Table II shows the current process flow of the production line that has been documented. Each movement of the operators was recorded for the purpose of further analysis that would be done in the Analyse phase. TABLE II: PROCESS FLOW WORK ELEMENT Operator Work Element C/T Left Hand Right Hand (sec) Take part from buffer zone Take and hold the first piece of part Take plier Press on the gate De-gating the gate Place the first piece 1 of part at side then take and hold the second piece of part Press on the gate De-gating the gate Change tool Place it into Remove the scrap of container part Take and hold the C. Analyse Phase Beforehand, a session of brainstorming is conducted to obtain the list of critical problems that occurs frequently in the production line. One of the key steps in lean production is the identification of the seven production wastes consist of the task that is non-value adding work. Hence, the list of problems is simplified into a seven wastes template in Table III. TABLE III: SEVEN WASTES TEMPLATE Wastes Unnecessary motion/movement Waiting Defect/rework Production problem occur The operator needs to change tools frequently ( and cutter) Excessive workers. Operator idling, starving occur for the operator when performing labeling process. She needs to wait for the de-gating process to be done then only the next process can be proceed. Wrong alignment of labeling The problems related to the seven wastes are based on the definition that was given earlier in the introduction section. Once the seven wastes template is completed the Prioritization Matrix is used to evaluate the level of criticality/concern of the wastes among each other. This Prioritization Matrix enables the assessment of the

5 Weight (A1) Movement (B1) Waiting (C1) Transportation (D1) Defect (E1) Overproduction (F1) Inventory (G1) Unnecessary processing Row total % Tools changeover frequently Excessive operator in process line Defect due to wrong labeling International Journal of Emerging Technology and Advanced Engineering characteristic needed based on a standard criteria and weight values (Table IV). It ameliorate in determining the level of important of the wastes (Analyse phase) and root causes (Improve phases) in the case study company. The result from the prioritization matrix will assist the continuous improvement team in deciding the solutions of the problem being focused. Table IV: RATING POINTS FOR PRIORITIZATION MATRIX Rating value Level of critical 10 Row is much more important than column 5 Row is more important than column 1 Row and column are equally important 0.2 row is less important than column 0.1 row is much less important than column The rating points of each waste can be referred in Table V. The rating is prepared after a thorough discussion with the continuous improvement team from Company X. For example, Movement (row) compared with Waiting (column), Movement is less important than Waiting. Hence, it is rated as 0.2 and recorded in the Table V. Table V: PRIORITIZATION MATRIX Wastes being compared to production line of Company X are Waiting, Movement and Defects. The next step is to compare the seven wastes with the problems that occur in the production line using the relationship matrix. The study is to associate the problems occurred with the other wastes that will be possible to associate it with one to another. The ranking points for each subject matter can be referred from Table VI. TABLE VI: RATING POINTS FOR RELATIONSHIP MATRIX Rating value Level of critical 1 Weak 5 Medium 9 Strong For example, Movement has a stronger connection with the problem of tools changeover frequently (Refer table VII). Hence it is rated as 9 and recorded in the table. The ratings are made based on the observation and discussion between the continuous improvement team from Company X. Table VII divulges the relationship of the waste and problems by using the relationship matrix. TABLE VII: RELATIONSHIP MATRIX Problems Wastes Wastes (A1) (B1) (C1) (D1) (E1) (F1) (G1) TOTAL The percentage for each waste is calculated by using the total of the row (refer Table V). The summary percentage value of each waste will be totalled up to 100%. Table V shows that the highest priority of waste elimination for the (A1) (B1) (C1) (D1) (E1) 3.7 (F1) 4.5 (G1) 4.5 Total Score Relative score (%) Rank

6 (A2) Simple single process (B2) Task requires many steps (C2) High frequency of changing tools (D2) No technical support (jigs and fixtures) (E2) Low operator efficiency (F2) Low motivation (G2) High transfer frequency row total % International Journal of Emerging Technology and Advanced Engineering After ranking and comparing the subject matter with one to another, the results obtained in Table VII shows that the subject matter that is rank as number 1 is the most vital problem. Focusing on one problem only that is excessive operator in one production line, this problem needs to be elaborated for further analysis to identify the root causes. In order to obtain the list of root causes, the appropriate subsequent step is to generate a fish bone diagram based on the main problem that the production line is facing. This fish bone diagram helps to stretched out further the problem in the production line that relates to the methodology, manpower, material and tool. It covers every aspect of the whole process that being analysed. Based the mapping of the fish bone diagram, it shows that the excessive operator in one production line occurs are due to seven issues. Once the issues have been identified, the improvement phase can begins. the problems, thus achieving the main objectives of the process improvement project determine during the first phase. A series of brainstorming sessions have been conducted by the continuous improvement team. A list of possible solutions is obtained. Hence, the best method to evaluate and analyze the solution is by using the same method as before- that by adopting the relationship matrix as shown in Table IX. TABLE VIII: ROOT CUASES PRIORITIZATION MATRIX Causes being compared to FIGURE 3: FISH BONE DIAGRAM Causes (A2) (B2) (C2) (D2) (E2) (F2) D. Improve Phase Prior to the previous fish bone diagram, a prioritization matrix as was used previously in analyse phase is generated. It is to weight the causes identified from the fish bone diagram. A similar approach is adopted that is using the prioritization matrix to generate weight values as tabulated in Table VIII. Based on Table VIII, high transfer frequency is the main cause of the problem followed by the low operator efficiency and there is no technical support (jigs and fixtures).the reasons behind the problem that occur will now be the guideline to plan the best solution for solving (G2) TOTAL Table IX shows the best solutions that will be implemented that are to combine the task, designing jigs and fixtures and followed by having effective training for the operator. Based on the proposed solutions, a new procedure of tasks needs to be developed.the new process steps that were derived, from extracting parts with robotic arm, cutting and de-gating, labeling process using jigs and placing the finished parts in the container The two workstations, which were de-gating and labelling were combined into one and will be performed by one operator. The labeling process will be completed by using jigs. Figure 4 shows the new layout that will be implemented 316

7 weight Combine tasks Design jigs and fixtures Design new cutting tools Effective training Improve ventilation system International Journal of Emerging Technology and Advanced Engineering once the solutions proposed is agreed upon by the top management of Company X. TABLE IX: RELATIONSHIP MATRIX use the production tools appropriately in completing the new assigned tasks. In addition to that on the basis of previous equations used in the Measurement Phase, the implementation of the improvement solutions would lead to a new target cycle time as shown in Table X: Causes Operator 1 Jig for sticking process FIGURE 4: IMPROVED PROCESS LAYOUT Degating process Solutions (A2) (B2) (C2) (D2) (E2) (F2) (G2) Total Score Relative score (%) Rank Robotic arm inventory Injection molding machine The implementation of the solutions identified towards the production line will eventually reduce or even eliminate the three wastes that initially occurred during the production processes. The utilisation of the operator is optimized and adequate time is allowed for the operator to 317 TABLE X: INCREASE OF PRODUCTIVITY AFTER PROCESS IMPROVEMENT Units Hour / Unit Hour / Cycle workload hour / unit / out- unit Process time (s) % line line hour put balance balance Injection Degating and labeling From the calculation, targeted overall workstation efficiency is 97.82%. It means that the utilization of operator will increase. The operating time for operator is closer to the cycle time of the injection machine after the solutions proposed being implemented. There is only 2.18% of idling time for the operator in each cycle of the parts produced from the injection molding machine. E. Control Phase In order to ensure that the proposed methods of improvement are being sustained and adopted undyingly, Company X will need to implement a set of control systems or adopting a new method. These control methods will also support the Company X in being more responsive to process variations in the future and will be better equipped to handle unexpected deviations. One of the useful methods would be continuously improving and updating the standard operating procedure (SOP) for the operator. As shown in this paper, the operator is having a new method to de-gating and labeling of the rear plastic housing that will be supported by new labeling jig. Therefore by having an up-dated SOP consisting of clear operations will be useful for reducing or eliminating the variations in procedure in completing the production tasks. Another method that is useful for controlling the system is a check sheet. It provides the guidance for the production personnel in Company X to adhere to the details of control plan for a more rapid analysis of the process

8 International Journal of Emerging Technology and Advanced Engineering performances. By monitoring and analyzing the production processes, assignable-cause variations can be distinguished and corrected. Documenting each and every production data is crucial for future continuous improvement references. For this control plan checklist, the main person that should take the responsibility in completing the task should be the team leader of the production line. In addition, constant training should be provided since the one operator will handle all the tasks, de-gating must be monitored intensively to avoid major defects caused by the operator. Thus, once the labeling jigs are installed into the process, the precision of the sticker towards the product should be accurate and consistent. These factors must be given extra attention in parallel with the control and monitoring plan developed. [3] B. Tjahjono, P. Ball, V.I. Vitanov, C. Scorzafave, J. Nogueira, J. Calleja, M. Minguet, L. Narasimha, A. Rivas, A. Srivastava, S. Srivastava, A. Yadav, "Six Sigma: a literature review", International Journal of Lean Six Sigma, 2010, Vol. 1 No: 3, pp [4] Yahia Zare Mehrjerdi, Six-Sigma: methodology, tools and its future, Assembly Automation, 2011, Vol. 31 No: 1, pp [5] Fred E. Meyers and matthew P. Stephens Manufacturing facilities Design and material handling. 2nd edition, pp. 120 IV. CONCLUSION DMAIC is more typically oriented toward identifying solution of problems at a root cause. By integrating it with seven managements and planning tools, the framework can be significant tools for identifying and eliminating production waste. Through a case study performed, the developed framework derived improvement solutions in the production line. From the solutions implemented it shows that the performance of the company is increased to a better level as regards to development of specific methods to redesign and reorganize the processes with a view to reduce or eliminate defects, improve utilization of operator, reduce operator s idle time and increase process performance. As a result, the solution proposed by combining the tasks performed in the process line with assist of sticking jig. It shows that the target performance of overall efficiency after improvement is increased from 78.26% to 97.82%. Acknowledgment This work is supported in part by the University Sains Malaysia, the top management of Company X and Knowledge Transfer Grant (KTP) from the Ministry of Higher Education (MOHE), Malaysia. REFERENCES [1] M.L. Emiliani, Lean behaviors, Management Decision, 1998, pp [2] Souraj Salah, Abdur Rahim, and Juan A. Carretero, The integration of Six Sigma and lean management, International Journal of Lean Six Sigma, 2010, Vol. 1 No. 3, pp