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Productivity improvement in assembly workstation of motor winding unit
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ScienceDirect Materials Today: Proceedings 5 (2018) 23518–23525
www.materialstoday.com/proceedings
IConAMMA_2017
Productivity improvement in assembly workstation of motor winding unit Raghunath G. Kulkarnia*, Vinayak N. Kulkarnib, V. N. Gaitondec a,b,c
School of Mechanical Engineering, KLE Technological University, Hubballi 580031, Karnataka, India
Abstract Current global competitive environment demands high productivity. Lower productivity results in financial losses. Manufacturers strive to keep the productivity high. This study aims to determine the cycle time for coil winding and insertion processes and propose improved methods to reduce them and improve the productivity. The study also aims at studying the existing shop floor layout and propose revised layout to reduce material movement in the shop. Video work study is performed on existing and proposed methods and are compared to measure the improvements. Existing and proposed shop floor layouts were analyzed using string diagram technique and ARENA software. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017]. Keywords: Work study; time study; standard time; video work study; WorkPro; string diagram; small and medium enterprise (SME); ARENA; layout optimization
1. Introduction Work Study is a technique aimed at studying the work done in an organization and determining the efficient and economical way for utilization of the available resource to achieve the maximum productivity possible. The use of scientific approaches to find solutions for management problems was heralded by F. W. Taylor who emphasized on
* Corresponding author. Tel.: +91-9535142545. E-mail address: [email protected] 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017].
Raghunath G. Kulkarni / Materials Today: Proceedings 5 (2018) 23518–23525
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fair day work. The study was concentrated on putting maximum efforts in managerial positions to achieve success in terms of obtaining the most work possible. Scientific management of oral management by data analysis aimed at improving efficiency with any physiological stress on the workers [1]. Work Study techniques aim to bring scientific approaches to managing resources in organizations. Motion Study and Study of Ergonomics help to reduce unnecessary motion which in turn reduces worker fatigue and improves cycle time. Time Study investigates all the activities being carried out in the operations and eliminate delay, waiting time, etc. Proper utilization of space helps to create an optimum plant layout which is aimed at reducing unnecessary motion [2,3]. Majority of the work concentrated on productivity utilizes the techniques such as 5S, Six Sigma, DMAIC, etc. AlSaleh (2011) studied the inspection lanes with an aim to find alternate solutions to achieve the objectives using some of the tools of motion study and time study. ARENA was used to simulate and predict the improved layout due to changes in the inspection lanes. Improvement in productivity was on par with predictions from work study techniques [4,5,6]. Globalization has brought with it trade growth opportunities by export of goods. This has created a need for higher productivity and organizations are trying to squeeze the last bit of work possible. Work study and Time Study play an important role in productivity improvement as they do away with unnecessary movement of materials, motions of workers and aim at creating an ergonomic workplace [7,8,9]. Service sectors are one of the quickest adopters of work study techniques as the sector generally work with the ‘time is money’ approach. Line balancing is also one of the aspects taken into consideration by work study as an unbalanced line is problematic. Bottleneck at any point in the line means the successive stations are kept idle for the material to arrive. The result is a loss to the organization [10,11]. Work Study techniques aim to bring scientific approaches to managing resources in organizations. Motion Study and Study of Ergonomics help to reduce unnecessary motion which in turn reduces worker fatigue and improves cycle time. Time Study investigates all the activities being carried out in the operations and eliminate delay, waiting time, etc. Proper utilization of space helps to create an optimum plant layout which aim at reducing unnecessary motion. Most of the research carried out have utilized method study techniques and manual time study. The primary concentration of these studies are medium and large scale industries. Very less work has been carried out at small scale industries which are striving to keep the productivity high. The present work aims at carrying out work study techniques at a small scale electrical company [12-15]. 1.1. Objectives of the study The study aims to investigate the effect of implementation of ergonomic workstation and analyze the improvement from the proposed shop floor layout. The primary objective is to study the existing shop floor layout and operations being carried out in the assembly station. The other objectives of the work are to propose revised shop floor layout, carry out video work study on existing and proposed workstation layouts, measure the improvement in proposed layout using string diagram and finally implement the improved workstation layout. 2. Research Methodology Unnecessary tasks and motion of the workers results in decreased productivity of the business and also worker fatigue. This is a wastage of important resources which in current global competitive environment can be harmful to the business as it will in turn create losses for the business. Work study helps businesses analyze their operations and take corrective measures to improve the productivity [16,17]. Work study is carried out to understand the problem that exists in the business and provide improved methods that aim at eliminating or reducing to negative effect on productivity. The two aspects of work study are used in order to understand the existing process and suggest revised methods for the same. These two aspects have set procedure to be followed in order to obtain accurate results [18-21].
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Raghunath G. Kulkarni/ Materials Today: Proceedings 5 (2018) 23518–23525
2.1. Time Study Time Study is a technique for observing and the recording the time taken to carry out a task, by using equipment such as stopwatch, digital stopwatch and video camera, etc. [22]. Time study is used when work which is of short or long duration is repeated, or a range of dissimilar work are performed. 2.2. Video Work Study (VWS) Video Work Study (VWS) is an advanced method used to carry out the work study analysis by using video recorded of the work bring performed and then using a software package record and analyze the data from the videos. This process eliminates all manual calculations, analysis, etc. and the results are provided by the software which uses predefined algorithms to compute and provide the results with little input from the person performing the study. It is widely used as it eliminates any chances of errors in the study as video is recorded and can be studied again in case of any errors and eliminates the process of collecting the data for the second trial. The data recorded in the software is stored and can be accessed at any moment to obtain results, graphs, charts, etc [23,24,25]. Video Work Study generally consists of the following steps: 1. Record the work using an approved video recording equipment. 2. Convert the video to suitable format as per software (if necessary). 3. Import the video into any VWS software such as WorkPro. 4. Split the video into different operations, tasks, etc. using the on-screen controls. 5. After completion of sectioning the software will provide results for different analyses as per requirement by requesting little information about the analysis. For the current study the video was recorded for two different stations viz. coil winding station and coil insertion station by using a Full HD capable video camera with digital video stabilization to eliminate errors in capturing the video. 2.3. WorkPro Software WorkPro is one of the feature rich and user friendly software available for performing Video Work Study. Video work study is preferred by many organizations for improvement as it offers an economic, effective and quick way to optimize the operations, thereby improving productivity. WorkPro provides a huge number of options that help us carry out studies such as video work study, standard time calculation, flow analysis, lean analysis, kaizen analysis, etc. 3. Data Analysis and Results Video Work Study was carried out for existing and proposed methods for coil insertion workbench and coil winding workbench, the stations that have the highest cycle times. String diagram and ARENA analysis was carried out on existing and proposed shop floor layouts. String diagram concentrated on the distance of material movement, whereas ARENA analysis concentrated on cycle times and movement times. 3.1. Video Work Study results of existing coil insertion process The existing process of coil winding was consuming excessive amount of time as the operator had no provisions to place the wound coil beside the machine. The operator after winding the coils would carry it to the table placed nearby and would tie it up and place it by segregating as per stator size. The movement from machine to table after every winding cycle was unnecessary.
Raghunath G. Kulkarni / Materials Today: Proceedings 5 (2018) 23518–23525
a
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b
Figure 1 (a)VA/NVA/RNVA graph for existing method (b)Flow Analysis bar graph for existing method
Based on the chart (Figure 1(a)), Non Value Adding (NVA) activities take up 4.77% of the time, Required Non Value Adding (RNVA) activities take up 4.59% of the time, and the rest is taken up by Value Adding (VA) activities. The NVA activity is moving of coil from winding station to assembly station which is not necessary and needs to be eliminated. The RNVA activity of adjusting the coils is important as coils have to be placed perfectly in the slots. This also affects the cycle time and can be reduced to lower the cycle time. Based on the histogram (Figure 1(b)), delays take up 4.77% of the time and the remaining 95.23% is taken up by operations. The major fraction of time is taken up by operations that are necessary to insert the coils into the stator and insert the insulation papers. The delay is caused when the operator has to move from his station to the coil winding station which is a wasted exercise. 3.2. Video Work Study results of proposed coil insertion process a
b
Figure 2 (a)VA/NVA/RNVA graph for proposed method (b)Flow Analysis bar graph for proposed method
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Raghunath G. Kulkarni/ Materials Today: Proceedings 5 (2018) 23518–23525
Based on the chart (Figure 2(a)), Non Value Adding (NVA) activities take up 1.56% of the time, Required Non Value Adding (RNVA) activities take up 7.01% of the time, and the rest is taken up by Value Adding (VA) activities. The NVA activities from the original process have been changed to RNVA activities which also consume lower time. The activities classified as NVA is the shaping of the coils which can be done during insertion and further work can be eliminated. As this did not take place it is classified as NVA activity. Based on the histogram (Figure 2(b)), inspection take up 1.56% of the time and the remaining 98.44% is taken up by operations. Delay in the process was the activity of moving the coils from the winding station to the workstation which has been eliminated and the avoidable process of shaping the coils although is a NVA activity is classified as an inspection process and remains to be eliminated by the efforts of the operator. The operator has to practice the process of shaping the coils as per the required while inserting the coil itself which will eliminate this activity. 3.3. Video Work Study results of existing coil winding process a
b
Figure 3 (a) VA/NVA/RNVA graph for existing method (b) Flow Analysis bar graph for proposed method
Based on the chart (Figure 3(a)), Non Value Adding (NVA) activities take up 3.66% of the time, Required Non Value Adding (RNVA) activities take up 12.88% of the time, and the rest is taken up by Value Adding (VA) activities. The activity of picking up the tools and other necessary items from other place will involve the operator moving from his station to other station and keeping them back in place. This NVA activity can be eliminated by making suitable arrangements. The RNVA activity of tying off the coil can be reduced into a single activity where the operator ties off the coil and cuts the wires. Based on the histogram (Figure 3(b)), delays take up 3.66% of the time, inspection take up 10.0% and the remaining 86.35% is taken up by operations. The delay is made up of the time taken by the operator to bring the tools from a different workstation perform his work and place the tools back. This as discussed earlier can be eliminated by making necessary arrangements for their placement. Inspection consists of tying off the coils into the former slots after dissection from copper wire bobbin, which can be reduced by combing multiple repeated tasks.
Raghunath G. Kulkarni / Materials Today: Proceedings 5 (2018) 23518–23525
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3.4. Video Work Study results of proposed coil winding process a
b
Figure 4 (a) VA/NVA/RNVA graph for existing method (b) Flow Analysis bar graph for proposed method
Based on the chart (Figure 4(a)), Required Non Value Adding (RNVA) activities take up 15.70% of the time, and the rest is taken up by Value Adding (VA) activities. As discussed the activity of operator movement to acquire tools has been eliminated which resulted in the elimination of NVA activities. The inability of the operator to perform the dissection task in a single activity resulted in increased RNVA times. It can be further eliminated by providing the operator with necessary training required to carry out the task. Based on the histogram (Figure 4(b)), delays are eliminated, inspection has been reduced to 4.15% and the remaining 95.85% is taken up by operations. The delay attributed to the operator movement has been eliminated as the operator movement has been eliminated by providing necessary placement for tools and other necessary items beside the operators’ location. Although the operator was unable to dissect the wires in a single activity, his try resulted in lower percentage of time being consumed for inspection process. 3.5. String Diagram Calculations Manual measurement of the shop floor dimensions was carried out for the existing layout and also for the proposed layout. The measurements thus obtained were scaled down and string diagrams were plotted and the length of the string for each case represents the movement of material within the shop floor before completion of the stator winding process. String length for existing shop floor layout = 185 cm String length for proposed shop floor layout = 114 cm 100
100 = 38.38 % The string diagram of original layout needed the material to move 185 cm from start to storage. The improved layout has a smooth flow of materials as the workstations are arranged in an assembly line order and on plotting a string diagram showed movement of 114 cm on the same scale. This resulted in reduction of movement by 71 cm or 38.38%. This will result in a reduction of total cycle time.
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3.6. ARENA results for existing and proposed layouts a
b
Figure 5 (a) Utilization of workstations in existing method(b)Utilization of workstations in proposed method
Based on Fig No. 5(a) and 5(b) we can observe that the fraction of utilization for the first three workstations have changed marginally. Whereas the later workstations have an improved utilization due to the improvement process carried out at the previous stations which now have lower cycle times that original. The changes at workstation 4 is 17.35% utilization compared to the original 14.79% and the changes at workstation 5 is 20.25% utilization compared to the original 15.35%. 4. Conclusions From the work study time chart it can be concluded that the implementation of revised methods has resulted in lower cycle times for both the processes which have improved the productivity as more products are produced in the same amount of time. On implementation of revised workbench layout the standard time for coil insertion station has reduced from 52.2 mins to 29 mins. This is an improvement of over 44%. Providing correct tools placement for coil winding workbench resulted in a marginal improvement in cycle time 14.9 mins to 13.59 mins. The improvement for this station is found to be 8.79%. The proposed methods have reduced the NVA activities and delays compared to the existing methods in all the workstations. The proposed shop floor layout has reduced the material movement by 38.38% and has also resulted higher fraction utilization of the workstations 4 and 5 of assembly line. Acknowledgements The authors would like to acknowledge the facilities provided by KLE Technological University, Hubballi and Shri Shivanand Electricals, Hubballi. The authors would also like to express their deep sense of gratitude to Dr. Ashok S. Shettar, Vice Chancellor, KLE Technological University, Prof. B. L. Desai, Registrar, KLE Technological University, Dr. B. B. Kotturshettar, Head, School of Mechanical Engineering, KLE Technological University and Dr. P. G. Tewari, Principal, B. V. Bhoomaraddi College of Engineering and Technology for their immense support for completion of this work.
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References [1] [2] [3] [4]
International Labour Office. Introduction to Work Study, International Labour Organisation, fourth edition, 1992 Suresh Dalela. A text book of Work Study, Standard Publishers, third edition, 1983 J. B. Singh, “Method Study (Work Study)”, E1-E2 Telecom Factory, Revision Date 19-01-2013 K. S. Al-Saleh, Productivity improvement of a motor vehicle inspection station using motion and time study techniques, Journal of King Saud University – Engineering Sciences 23 (2011), pg. 33–41 [5] C. Duran, A. Cetindere, Y. E. Aksu, Productivity improvement by work and time study technique for earth energy-glass manufacturing company, Procedia Economics and Finance 26 (2015) pg. 109 – 113 [6] M. A. Moktadir, S. Ahmed, Fatema-Tuj-Zohra, R. Sultana, Productivity Improvement by Work Study Technique: A Case on Leather Products Industry of Bangladesh, Ind Eng Manage 2017, 6:1 [7] M. D. Singh, S. Singh, D. Keyur, S. Saumil, Patel N., Panchal H., Overall Productivity Improvement in Casting Industry by Using Various Industrial Engineering Techniques, IJIRSET, Vol. 4, Issue 1, January 2015, pp. 18713-18721 [8] N. Patel, Reduction in product cycle time in bearing manufacturing company, IJERGS, Volume 3, Issue 3, May-June, 2015, pp. 466-471 [9] Parthiban P., Raju R., Productivity improvement in Shoe making industry by using Method Study, IOSR-JMCE, e-ISSN: 2278-1684, pp. 0108 [10] Patange V. C., An Effort to Apply Work and Time Study Techniques in a Manufacturing Unit for Enhancing Productivity, IJIRSET, Vol. 2, Issue 8, August 2013, pp. 4050-4058 [11] I. Bhiradi, B. K. Singh, Work Measurement Approach for Productivity Improvement in a Heavy Machine Shop, AIMTDR, 570, 2014 [12] P. P. Kulkarni, S. S. Kshire, K. V. Chandratre, Productivity Improvement Through Lean Deployment & Work Study Methods, IJRET, Volume: 03 Issue: 02, Feb-2014, pp. 429-434 [13] Shuang Lan, Xue Wang, Lixin Ma, Optimization of Assembly Line Based on Work Study, IEEE, 978-1-4244-3672-9/ 09, 2009, pp. 813-816 [14] V. S. Gogi, Rohith D, Shashi K K and S. M. Shaikh, Efficiency Improvement of a Plant Layout, IJIRSET Vol. 3 Issue 4, 2014, pp 1120311209 [15] R. Mishra, Productivity improvement in Automobile industry by using method study, IJSEAS, 2015, Vol. 1 Issue 4 pp 361-363 [16] M. Tapiwa, M. Kumbirayi and C. Tauyanshe, The use of Work Study Techniques in Optimizing Manufacturing Plant Maintenance Processes: an Investigation into a Fertilizer Manufacturing Company in Zimbabwe 2013 IJSR Vol. 2 Issue 2 pp. 98-103 [17] S. Tangen, Understanding the concept of productivity, APIEMS, 2002 [18] C. Andersson, M. Bellgran, On the complexity of using performance measures: Enhancing sustained production improvement capability by combining OEE and productivity, Journal of Manufacturing Systems 35, 2015, pp. 144–154 [19] D. P. Mishra, M. Sugla, P. Singha, Productivity Improvement in Underground Coal Mines – A Case Study, J. Sust. Min. Vol. 12 (2013), No. 3, pp. 48–53 [20] F. F. Baesler, E. Araya, F. J. Ramis, J. A. Sepulveda, The Use of Simulation and Design of Experiments for Productivity Improvement in the Sawmill Industry, Proc. of the Winter Simulation Conference, 2004 [21] M. P. Singh, H. Yadav, Improvement in Process Industries by Using Work Study Methods: A Case Study, IJMET, 2016, Volume 7, Issue 3, pp.426–436 [22] M. Akansel, B. Yagmahan, E. Emel, Determination of Standard Times for Process Improvement: A Case Study. Global Journal of Business, Economics and Management: Current Issues, 2017 [23] R. Kamble, V. Kulkarni, Productivity Improvement at Assembly Station Using Work Study Techniques, IJRET Volume: 03 Issue: 09, Sep2014, pp. 480-487 [24] V. Kulkarni, K. R. Darshan, N. Nayak, P. Kulkarni and P. Singh, Productivity Improvement using Work Study Techniques, IJSSM, 2014, Vol. 3 Issue 2 pp. 149-153 [25] H. N. Roy, S. Saha, T. Bhowmick, S. C. Goldar, Productivity Improvement of a Fan Manufacturing Company by using DMAIC Approach: A Six-Sigma Practice, Global Journal of Researches in Engineering Industrial Engineering, 2013, Volume 13 Issue 4
ScienceDirect Materials Today: Proceedings 5 (2018) 23518–23525
www.materialstoday.com/proceedings
IConAMMA_2017
Productivity improvement in assembly workstation of motor winding unit Raghunath G. Kulkarnia*, Vinayak N. Kulkarnib, V. N. Gaitondec a,b,c
School of Mechanical Engineering, KLE Technological University, Hubballi 580031, Karnataka, India
Abstract Current global competitive environment demands high productivity. Lower productivity results in financial losses. Manufacturers strive to keep the productivity high. This study aims to determine the cycle time for coil winding and insertion processes and propose improved methods to reduce them and improve the productivity. The study also aims at studying the existing shop floor layout and propose revised layout to reduce material movement in the shop. Video work study is performed on existing and proposed methods and are compared to measure the improvements. Existing and proposed shop floor layouts were analyzed using string diagram technique and ARENA software. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017]. Keywords: Work study; time study; standard time; video work study; WorkPro; string diagram; small and medium enterprise (SME); ARENA; layout optimization
1. Introduction Work Study is a technique aimed at studying the work done in an organization and determining the efficient and economical way for utilization of the available resource to achieve the maximum productivity possible. The use of scientific approaches to find solutions for management problems was heralded by F. W. Taylor who emphasized on
* Corresponding author. Tel.: +91-9535142545. E-mail address: [email protected] 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017].
Raghunath G. Kulkarni / Materials Today: Proceedings 5 (2018) 23518–23525
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fair day work. The study was concentrated on putting maximum efforts in managerial positions to achieve success in terms of obtaining the most work possible. Scientific management of oral management by data analysis aimed at improving efficiency with any physiological stress on the workers [1]. Work Study techniques aim to bring scientific approaches to managing resources in organizations. Motion Study and Study of Ergonomics help to reduce unnecessary motion which in turn reduces worker fatigue and improves cycle time. Time Study investigates all the activities being carried out in the operations and eliminate delay, waiting time, etc. Proper utilization of space helps to create an optimum plant layout which is aimed at reducing unnecessary motion [2,3]. Majority of the work concentrated on productivity utilizes the techniques such as 5S, Six Sigma, DMAIC, etc. AlSaleh (2011) studied the inspection lanes with an aim to find alternate solutions to achieve the objectives using some of the tools of motion study and time study. ARENA was used to simulate and predict the improved layout due to changes in the inspection lanes. Improvement in productivity was on par with predictions from work study techniques [4,5,6]. Globalization has brought with it trade growth opportunities by export of goods. This has created a need for higher productivity and organizations are trying to squeeze the last bit of work possible. Work study and Time Study play an important role in productivity improvement as they do away with unnecessary movement of materials, motions of workers and aim at creating an ergonomic workplace [7,8,9]. Service sectors are one of the quickest adopters of work study techniques as the sector generally work with the ‘time is money’ approach. Line balancing is also one of the aspects taken into consideration by work study as an unbalanced line is problematic. Bottleneck at any point in the line means the successive stations are kept idle for the material to arrive. The result is a loss to the organization [10,11]. Work Study techniques aim to bring scientific approaches to managing resources in organizations. Motion Study and Study of Ergonomics help to reduce unnecessary motion which in turn reduces worker fatigue and improves cycle time. Time Study investigates all the activities being carried out in the operations and eliminate delay, waiting time, etc. Proper utilization of space helps to create an optimum plant layout which aim at reducing unnecessary motion. Most of the research carried out have utilized method study techniques and manual time study. The primary concentration of these studies are medium and large scale industries. Very less work has been carried out at small scale industries which are striving to keep the productivity high. The present work aims at carrying out work study techniques at a small scale electrical company [12-15]. 1.1. Objectives of the study The study aims to investigate the effect of implementation of ergonomic workstation and analyze the improvement from the proposed shop floor layout. The primary objective is to study the existing shop floor layout and operations being carried out in the assembly station. The other objectives of the work are to propose revised shop floor layout, carry out video work study on existing and proposed workstation layouts, measure the improvement in proposed layout using string diagram and finally implement the improved workstation layout. 2. Research Methodology Unnecessary tasks and motion of the workers results in decreased productivity of the business and also worker fatigue. This is a wastage of important resources which in current global competitive environment can be harmful to the business as it will in turn create losses for the business. Work study helps businesses analyze their operations and take corrective measures to improve the productivity [16,17]. Work study is carried out to understand the problem that exists in the business and provide improved methods that aim at eliminating or reducing to negative effect on productivity. The two aspects of work study are used in order to understand the existing process and suggest revised methods for the same. These two aspects have set procedure to be followed in order to obtain accurate results [18-21].
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2.1. Time Study Time Study is a technique for observing and the recording the time taken to carry out a task, by using equipment such as stopwatch, digital stopwatch and video camera, etc. [22]. Time study is used when work which is of short or long duration is repeated, or a range of dissimilar work are performed. 2.2. Video Work Study (VWS) Video Work Study (VWS) is an advanced method used to carry out the work study analysis by using video recorded of the work bring performed and then using a software package record and analyze the data from the videos. This process eliminates all manual calculations, analysis, etc. and the results are provided by the software which uses predefined algorithms to compute and provide the results with little input from the person performing the study. It is widely used as it eliminates any chances of errors in the study as video is recorded and can be studied again in case of any errors and eliminates the process of collecting the data for the second trial. The data recorded in the software is stored and can be accessed at any moment to obtain results, graphs, charts, etc [23,24,25]. Video Work Study generally consists of the following steps: 1. Record the work using an approved video recording equipment. 2. Convert the video to suitable format as per software (if necessary). 3. Import the video into any VWS software such as WorkPro. 4. Split the video into different operations, tasks, etc. using the on-screen controls. 5. After completion of sectioning the software will provide results for different analyses as per requirement by requesting little information about the analysis. For the current study the video was recorded for two different stations viz. coil winding station and coil insertion station by using a Full HD capable video camera with digital video stabilization to eliminate errors in capturing the video. 2.3. WorkPro Software WorkPro is one of the feature rich and user friendly software available for performing Video Work Study. Video work study is preferred by many organizations for improvement as it offers an economic, effective and quick way to optimize the operations, thereby improving productivity. WorkPro provides a huge number of options that help us carry out studies such as video work study, standard time calculation, flow analysis, lean analysis, kaizen analysis, etc. 3. Data Analysis and Results Video Work Study was carried out for existing and proposed methods for coil insertion workbench and coil winding workbench, the stations that have the highest cycle times. String diagram and ARENA analysis was carried out on existing and proposed shop floor layouts. String diagram concentrated on the distance of material movement, whereas ARENA analysis concentrated on cycle times and movement times. 3.1. Video Work Study results of existing coil insertion process The existing process of coil winding was consuming excessive amount of time as the operator had no provisions to place the wound coil beside the machine. The operator after winding the coils would carry it to the table placed nearby and would tie it up and place it by segregating as per stator size. The movement from machine to table after every winding cycle was unnecessary.
Raghunath G. Kulkarni / Materials Today: Proceedings 5 (2018) 23518–23525
a
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b
Figure 1 (a)VA/NVA/RNVA graph for existing method (b)Flow Analysis bar graph for existing method
Based on the chart (Figure 1(a)), Non Value Adding (NVA) activities take up 4.77% of the time, Required Non Value Adding (RNVA) activities take up 4.59% of the time, and the rest is taken up by Value Adding (VA) activities. The NVA activity is moving of coil from winding station to assembly station which is not necessary and needs to be eliminated. The RNVA activity of adjusting the coils is important as coils have to be placed perfectly in the slots. This also affects the cycle time and can be reduced to lower the cycle time. Based on the histogram (Figure 1(b)), delays take up 4.77% of the time and the remaining 95.23% is taken up by operations. The major fraction of time is taken up by operations that are necessary to insert the coils into the stator and insert the insulation papers. The delay is caused when the operator has to move from his station to the coil winding station which is a wasted exercise. 3.2. Video Work Study results of proposed coil insertion process a
b
Figure 2 (a)VA/NVA/RNVA graph for proposed method (b)Flow Analysis bar graph for proposed method
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Raghunath G. Kulkarni/ Materials Today: Proceedings 5 (2018) 23518–23525
Based on the chart (Figure 2(a)), Non Value Adding (NVA) activities take up 1.56% of the time, Required Non Value Adding (RNVA) activities take up 7.01% of the time, and the rest is taken up by Value Adding (VA) activities. The NVA activities from the original process have been changed to RNVA activities which also consume lower time. The activities classified as NVA is the shaping of the coils which can be done during insertion and further work can be eliminated. As this did not take place it is classified as NVA activity. Based on the histogram (Figure 2(b)), inspection take up 1.56% of the time and the remaining 98.44% is taken up by operations. Delay in the process was the activity of moving the coils from the winding station to the workstation which has been eliminated and the avoidable process of shaping the coils although is a NVA activity is classified as an inspection process and remains to be eliminated by the efforts of the operator. The operator has to practice the process of shaping the coils as per the required while inserting the coil itself which will eliminate this activity. 3.3. Video Work Study results of existing coil winding process a
b
Figure 3 (a) VA/NVA/RNVA graph for existing method (b) Flow Analysis bar graph for proposed method
Based on the chart (Figure 3(a)), Non Value Adding (NVA) activities take up 3.66% of the time, Required Non Value Adding (RNVA) activities take up 12.88% of the time, and the rest is taken up by Value Adding (VA) activities. The activity of picking up the tools and other necessary items from other place will involve the operator moving from his station to other station and keeping them back in place. This NVA activity can be eliminated by making suitable arrangements. The RNVA activity of tying off the coil can be reduced into a single activity where the operator ties off the coil and cuts the wires. Based on the histogram (Figure 3(b)), delays take up 3.66% of the time, inspection take up 10.0% and the remaining 86.35% is taken up by operations. The delay is made up of the time taken by the operator to bring the tools from a different workstation perform his work and place the tools back. This as discussed earlier can be eliminated by making necessary arrangements for their placement. Inspection consists of tying off the coils into the former slots after dissection from copper wire bobbin, which can be reduced by combing multiple repeated tasks.
Raghunath G. Kulkarni / Materials Today: Proceedings 5 (2018) 23518–23525
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3.4. Video Work Study results of proposed coil winding process a
b
Figure 4 (a) VA/NVA/RNVA graph for existing method (b) Flow Analysis bar graph for proposed method
Based on the chart (Figure 4(a)), Required Non Value Adding (RNVA) activities take up 15.70% of the time, and the rest is taken up by Value Adding (VA) activities. As discussed the activity of operator movement to acquire tools has been eliminated which resulted in the elimination of NVA activities. The inability of the operator to perform the dissection task in a single activity resulted in increased RNVA times. It can be further eliminated by providing the operator with necessary training required to carry out the task. Based on the histogram (Figure 4(b)), delays are eliminated, inspection has been reduced to 4.15% and the remaining 95.85% is taken up by operations. The delay attributed to the operator movement has been eliminated as the operator movement has been eliminated by providing necessary placement for tools and other necessary items beside the operators’ location. Although the operator was unable to dissect the wires in a single activity, his try resulted in lower percentage of time being consumed for inspection process. 3.5. String Diagram Calculations Manual measurement of the shop floor dimensions was carried out for the existing layout and also for the proposed layout. The measurements thus obtained were scaled down and string diagrams were plotted and the length of the string for each case represents the movement of material within the shop floor before completion of the stator winding process. String length for existing shop floor layout = 185 cm String length for proposed shop floor layout = 114 cm 100
100 = 38.38 % The string diagram of original layout needed the material to move 185 cm from start to storage. The improved layout has a smooth flow of materials as the workstations are arranged in an assembly line order and on plotting a string diagram showed movement of 114 cm on the same scale. This resulted in reduction of movement by 71 cm or 38.38%. This will result in a reduction of total cycle time.
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3.6. ARENA results for existing and proposed layouts a
b
Figure 5 (a) Utilization of workstations in existing method(b)Utilization of workstations in proposed method
Based on Fig No. 5(a) and 5(b) we can observe that the fraction of utilization for the first three workstations have changed marginally. Whereas the later workstations have an improved utilization due to the improvement process carried out at the previous stations which now have lower cycle times that original. The changes at workstation 4 is 17.35% utilization compared to the original 14.79% and the changes at workstation 5 is 20.25% utilization compared to the original 15.35%. 4. Conclusions From the work study time chart it can be concluded that the implementation of revised methods has resulted in lower cycle times for both the processes which have improved the productivity as more products are produced in the same amount of time. On implementation of revised workbench layout the standard time for coil insertion station has reduced from 52.2 mins to 29 mins. This is an improvement of over 44%. Providing correct tools placement for coil winding workbench resulted in a marginal improvement in cycle time 14.9 mins to 13.59 mins. The improvement for this station is found to be 8.79%. The proposed methods have reduced the NVA activities and delays compared to the existing methods in all the workstations. The proposed shop floor layout has reduced the material movement by 38.38% and has also resulted higher fraction utilization of the workstations 4 and 5 of assembly line. Acknowledgements The authors would like to acknowledge the facilities provided by KLE Technological University, Hubballi and Shri Shivanand Electricals, Hubballi. The authors would also like to express their deep sense of gratitude to Dr. Ashok S. Shettar, Vice Chancellor, KLE Technological University, Prof. B. L. Desai, Registrar, KLE Technological University, Dr. B. B. Kotturshettar, Head, School of Mechanical Engineering, KLE Technological University and Dr. P. G. Tewari, Principal, B. V. Bhoomaraddi College of Engineering and Technology for their immense support for completion of this work.
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