Address for Correspondence

Transcription

1 Okpala et al, International Journal of Advanced Engineering Technology Review Article THE TOOLS AND TECHNIQUES OF LEAN PRODUCTION SYSTEM OF MANUFACTURING Chukwutoo C. Ihueze and Charles C. Okpala Department of Industrial/Production Engineering, Nnamdi Azikiwe University, P.M.B Awka, Anambra State, Nigeria. ABSTRACT This paper discussed in details the main tools and techniques of Lean Production System (LPS) a manufacturing strategy that has been adjudged the world s best practice, and is aimed at improving throughput and profitability,, by eliminating all wastes that are inherent in all manufacturing processes. In LPS, waste (muda) is seen as anything that destroys resources and does not add value to the requirements of the customer. The production approach is geared towards turning manufacturing which used to be full of waste of time and resources into a well organized, efficient and more profitable venture. The discussed tools and techniques are Cellular Manufacturing, Just-in-Time, Total Productive Maintenance, Value Stream Mapping, Poka Yoke, Five-S Practice, Single Minute Exchange of Dies, Takt Time Analysis, Kaizen, Visual Management, and Single piece flow. The paper revealed that the successful application of the various tools and techniques of LPS assists manufacturing companies in starting improvement processes, increase the overall awareness of quality, and also enhance the change of attitude of employees. However, the paper also explained that the tools and techniques will not achieve the desired results if they are not properly utilized; this is because LPS is not just the application of a bunch of tools but rather a completely different approach of manufacturing. KEYWORDS: Lean production system, throughput, cellular manufacturing, single minute exchange of dies, waste. 1. INTRODUCTION Manufacturers has over the years come to realise that they could not remain economically viable in the present day market without improving their efficiency and productivity in line with their competitors. To this end, it became evident that this could not be achieved through the traditional system of manufacturing which involves masss production. Therefore to remain competitive in the global market, they have embraced Lean Production System (LPS). LPS considerably reduces the cost of manufacturing, as it leads to reduction of all wastes that are associated with mass production, thereby enabling organisations to save lots of money. Commenting on the main aim of the manufacturing system, Ohno (1988) observed that it ensures the improvement of efficiency of production by taking adequate and thorough measures to eliminate wastes. According to Ihueze and Okpala (2012), Apart from identifying and eliminating wastes, LPS enables organizations to be more profitable through the application of fewer resources to manufacture more quality products at a faster rate, thereby leading to competitive advantage and customer satisfaction. Unlike mass production that is geared towards the manufacturing of large quantity of products, LPS is aimed at increasing efficiency and reducing production cost, by manufacturing the exact number of high quality products when they are needed by the customer, with emphasis on the keeping of very low inventory. According to Ohno (1988), the best approach of improving productivity is for manufacturers to produce only the exact amount of products they require with the minimumm number of employees, he pointed out that efficiency is sensible only when it achieves cost reduction. Apart from identifying and eliminating wastes, LPS enables organizations to be more profitable through the application of fewer resources to manufacture more quality products at a faster rate, thereby leading to competitive advantage and customer satisfaction. As shown below in figure 1, the major focus of LPS according to Shinkle, Gooding and Smith (2004) are to: achieve customer satisfaction, enhance value through the elimination of waste, reduce cycle time Address for Correspondence E-ISSN through response to speed, improve flow, and flexibility to ensure customer satisfaction. Figure 1: The Lean Focus Star Source: Shinkle, Gooding and Smith (2004) In their study Schonberger et al (2000) stated that Lean Production System is an approach to manufacturing which aims at achieving greater results with fewer resources. They observed that it focuses on total quality management, just-in-time production, waste elimination, continuous improvement, multifunctional teams, product design, and supplier partnerships. They maintained that it does not only focus on core production activities, but also aimed at product development, component procurement, and product distribution. 2. TOOLS AND TECHNIQUES OF LEAN PRODUCTION SYSTEM There are many tools and techniques of Lean Production System, the application of these tools and techniques assists in starting improvement processes, increasing the overall awareness of quality and also enhances the change of attitude of employees. In his study Dale (2003) explained that tools and techniques of LPS are used to aid quality planning, listen to the voices of the customer, capture data, control processes, make improvements, solve problems and improve people. However, the various tools and techniques will not achieve the desired results if they are not properly utilized; this is because LPS is not just the application

2 of a bunch of tools but rather a completely different approach of manufacturing. This was pointed out by Lang and Hugge (1995) as they argued that although a lot of techniques and tools have been associated with the concept of Lean design and manufacturing, they prove to be futile unless they are integrated with thorough understanding of the manufacturing processes, redefinition of the currently adopted processes and multidiscipline teams assigned to implement changes. Some of these tools and techniques which include Just-in-time, Cellular manufacturing, Single minute exchange of dies, Kaizen, Total productive maintenance, Value stream mapping, Five-S practice, Takt time analysis etc. are shown in figure 1. The applications, strengths, and limitations of the various LPS tools and techniques are listed in table 1. Figure 1: LPS tools and techniques house Source: Swmas, Table 1: The applications, strengths and limitations of LPS tools and techniques Tools/ techniques Applications Strengths Limitations/ Problems Uninterrupted movement of Cellular Shop floor. materials, overhead cost reduction, High set up cost. Manufacturing enhances flexible manufacturing. Just-In-Time Total Productive Maintenance Value Stream Mapping Poka Yoke Five-S Practice Single Minute Exchange of Dies Takt Time Analysis Kaizen Visual Management Supply chain, manufacturing. Machines and equipment. Supply chain, manufacturing. Manufacturing processes Shop floor Machines Manufacturing processes All production processes Shop floor Cellular Manufacturing Cellular manufacturing can be defined as a tool and technique of LPS where machines and equipment are properly arranged in order to enhance the steady and uninterrupted movement of materials and tools through the process of production without stoppages and time wastage. In their study Levinson and Rerick (2002) observed that it is only by relating each machine with the others in such a way that production will follow in straight lines without confusion, can the highest economy operation be attained. As depicted in Figure 2, Cellular Manufacturing does not allow easy accumulation of inventory as materials are immediately processed one after the other. The importance of the application of Cellular Manufacturing can be observed from figure 3 where it makes electronic layout less complicated thereby allowing for cheap transportation of equipment like the conveyors, this is distinct from the functional layout that requires forklifts and very costly automation. Improves productivity and profitability, reduces inventory, costs and lead time. Machines and equipment safety and maintenance, increase in productivity, defect reduction. Provides information and material flow, reduces cost and lead time. Eliminates errors and mistakes, reduces defects, and improves quality of products. Ensures neat shop floor, improves productivity, and reduces waste. Set up time reduction, increase in productivity and flexibility, reduction in inventory and wastes. Synchronizes demand and manufacturing, reduces wastes. Reduce wastes and inventory, improves productivity, quality of products and flexibility. Enhances productivity, efficiency and quality. Leads to losses sometimes due to stoppages in production as a result of suppliers failures. Delay in yielding of results. Does not incorporate management of human resources and the development of products. Requires set up time. Requires constant work and updating. Requires High set up cost. Difficult to apply in the manufacturing of diverse products. Results to flow disruptions. Requires constant updating. Figure 2: A Cellular Manufacturing plant Source: Hiroyuki (1998)

3 Fig. 3: Functional and Cellular layouts Source: Strategosinc, The main benefit of Cellular Manufacturing is that it assists organizations to reduce the overhead cost, as an individual worker can monitor and manage series of machines and equipment in a production channel. Also it encourages flexible manufacturing as well as reduces the wastage of shop floor space. However, it has been observed that many manufacturers are very reluctant to fully change over to cellular layout in their shop floors due to its high set up cost, as well as their unwillingness to cease production during the setting up period. Just-in-time Just-in-time (JIT) production which involves the identification and tackling of problems, as well as production cost elimination is one of the most widely used tools of LPS. It enables manufacturers to manufacture the exact amount of products their customers need and at the time they are required. According to Dennis (2002), Just-in-time means ensuring the manufacturing of the right item at the right quantity and also at the right time. It is an economical approach of manufacturing as it aims at reducing lead time and also eliminates all unwanted costs inherent in manufacturing processes. In their study Albino and Okogbaa (2001) listed the three sub goals of JIT as: Quantity control, which enables the system to adjust to daily and monthly demand fluctuations in quantity and variety; Quality assurance, which ensures that each process will supply only defect-free units to subsequent processes; and Respect of the worker, which is the base to increase human resources productivity necessary for attaining the system s cost objectives. The main strength of JIT tool is its ability to better and evenly spread out manufacturing over a required period of time, as well as the provision of products and services when they are required. It also enables manufacturers to maintain the lowest possible inventory by being in constant touch with their suppliers, thereby leading to constant waste reduction. However, commenting on the limitations of JIT, Standard and Davies (1999) stated that JIT delivery without JIT production most certainly increases cycle time and inventory. They indicated that it results to suffering of customer service, profitability, and quality, thereby leading to inability to achieve the benefits of JIT production. Also, as Lean companies have no inventory to fall back on, the application of JIT sometimes leads to losses due to stoppages in production as a result of supplier s failures. Total Productive Maintenance Total Productive Maintenance (TPM) is defined by Dale (1994) as a scientific, company-wide approach in which every employee is concerned about the maintenance and the quality and efficiency of their equipment. He argued that its objective is to shorten the overall whole-life cost of equipment and machines through better maintenance management. TPM which emphasizes on the importance of teamwork is focused on enhancing the expertise of machine operators through education and trainings to enable them to take adequate care and maintenance of their company s machineries and equipment for better operating efficiency. In his study Nakajima (1988) concluded that its double aim is to completely eliminate defective products and machine breakdowns. He maintained that achieving this leads to the reduction of costs and inventory, improvement of equipment operation, as well as a considerable increase in labour productivity. McCarthy and Rich (2004) listed the following as the critical success factors of implementing TPM in an organization. Improving the effectiveness of equipment; Incorporating productive maintenance system into the equipment s life; Ensuring the participation of all employees; Integration of planning, design, and maintenance departments in TPM implementation; TPM promotion through management motivation. Enhancing more effective flexibility, as well as reduction in defective products and lead time are some of the strengths of TPM. While its limitation is its delay in yielding of results, this is because it takes an average of three years for waste elimination to commence after the application of TPM. Value Stream Mapping Dinesh and Vaibhay (2005) defined Value Stream Mapping (VSM) as the process of mapping the material and information flows of all components and sub-assemblies in a value stream that includes manufacturing, suppliers and distribution to the customer. They explained that it has been very

4 useful in isolating and getting rid of wastes within a system with related product routings. VSM is an effective LPS tool that involves the use of paper and pencil, and assists in the understanding and monitoring information and material flow in a manufacturing plant as materials flow across the value stream from raw material to shipping. Its implementation assists an organization to improve the quality of its products, reduce the cost of manufacturing and lead time. Womack (2006) pointed out that identifying the family (set of components which move along the same activities and machines in a manufacturing company) of a product is the first approach of mapping process. He maintained that mapping is made quite easy and its benefits greatly enhanced when decisions were taken at the beginning to appropriately classify products according to families. As shown in figure 4, VSM provides the information and material flow in a manufacturing plant; it also shows various production processes, as well as the rate of defects, and set up time. Figure 4: An example of a Value Stream Map Source: Yang and El-Haik (2003) The main limitation of VSM according to Hines (1998) is that its application is not incorporated into a company s corporate strategy as well as the broader business circle. They argued that such a danger of the mapping was that it would be done in isolation of the needs of the company, potentially yielding impressive percentage improvements but unrelated to business or supply chain needs. They also maintained that VSM while focusing on fulfilment of orders and incorporation of the supplier processes pays no attention to major processes like the management of human resources and the development of products. Poka Yoke As companies and manufacturers lose money because of errors and mistakes made by employees in the course of manufacturing, LPS adopted a very effective tool and technique known as Poka Yoke (Error Proofing) for the elimination of the various mistakes. In his study Benhabib (2003) explained that Poka Yoke involves the use of devices and procedures that would prevent the assembly of wrong components and ensure the presence of all components and subassemblies. Poka Yoke is employed in the elimination of the manufacturing of defective products by ensuring the stoppage of production processes whenever an error is detected, thereby leading to reduction of production costs. With its application employees are able to self-check the work in progress during manufacturing thereby ensuring that a defective product does not pass through the production line. In most cases the concept adopts the use of cheap approaches that assists in the detection and prevention of defects without necessarily requiring the absolute concentration of the workers, by either eliminating the mistake or signaling to the worker about the mistake that is about to be made. Five-S CANDO Practice Five S is a tool of LPS which is aimed at increasing productivity by sanitizing as well as ensuring a neat and well arranged shop floor; it also adopts the use of visual signs to ensure greater benefits. The five-s which were originally Japanese words are: Seiri (Sort): Isolate and get rid of all materials that are not useful; Seiton (Straighten): Systemize the important materials and arrange them properly for better retrieval when they are required; Seiso (Shine): Clean-up the entire shop floor to maintain a conducive environment for manufacturing; Seiketsu (Systemize): Maintain a constant cleaning of the surroundings. Shitsuke (Sustain): Involve all the employees and ensure that the constant cleaning is maintained. On the other hand, the CANDO which is an English alternative has a similar meaning as it stands for: Cleanup, Arranging, Neatness, Discipline, and Ongoing improvement. This technique is geared towards ensuring that the employees maintain a neat working environment that is in order, very clean and well organized. Its benefits include: accident reduction and increase in efficiency. The first task in transforming a company to Lean production according to Skinner (2003) is to adopt the Five-S practice to properly structure and arrange the shop floor. He observed that it leads to the reduction of wastes inherent in waiting, unnecessary movement, inventory as well as wastes in other manufacturing processes. Single Minute Exchange of Dies Single Minute Exchange of Dies (SMED) is a productivity improvement LPS tool and technique aimed at waste elimination through setup time reduction. SMED plays a prominent role in Lean manufacturing as achieving setup time reduction is very important in transforming a company from mass production to Lean production. According to Shingo (1985), the application of SMED results in remarkable setup time reductions as well as increase in productivity even in its inception. He listed the three stages involved in the application of the tool as separating internal and external setup, converting internal to external setup, and streamlining all aspects of the setup operation. With quick changeover, SMED contributes immensely to increase in flexibility, production capacity and the maintenance of very low inventory in Lean production, as one-piece flow and streamlining operations can easily be achieved. Also the application of SMED enables manufacturing companies to be more competitive by achieving the following: a decrease in lot size production, setup time reduction, decrease in planning and scheduling overhead, waste elimination, and more efficient utilization of material resources, thereby leading to the production of high quality products that meets the customer s requirements. However, according to Patel, Shaw and Dale (2001), some of the major difficulties being faced by manufacturing companies in their application of SMED include:

5 Inadequate financial resources that will facilitate error proofing and reduction of set up time; Employees resistance to affect the required changes; Lack of the necessary strategy to enhance the application of SMED and error proofing; and Ignorance and inadequate training on the SMED methodologies. Takt Time Analysis Takt time is the rate with which products flow through the line of production, it can be achieved by synchronizing the production rate to the rate of product demand. Its knowledge and application is a very important aspect of LPS. According to Page (2004) takt time is the rate at which a cell produces unit products. He noted that it is used in the calculation of a manufacturing cell s size in order to ensure that it has adequate capacity to meet the demands for materials by the next user downstream. Takt time which is calculated as the (available time) divided by the (demand required) is applied in LPS to ensure that the customer s requirement are met through timely provision of products, thereby ensuring that excess manufacturing of products which translates to waste is avoided. During production when there is a less demand for products, the takt time is increased through reallocating the workers and reducing the inventory accordingly, while the takt time is determined again and subsequently reduced when the customer s demand increased thereby resulting in increase in the number of products, in order to ensure customer satisfaction. The limitation of Takt time analysis technique is the difficulty that are always encountered whenever it is applied where machines and equipment are employed for the manufacturing of diverse products. Kaizen Kaizen which is a Japanese word for continuous improvement is a very efficient tool and technique of LPS which is aimed at the adoption of creativity and innovation to detect and reduce non-value-adding work, and also affect the changes within the shortest possible time, thereby increase productivity. Here efforts are made to apply and maintain little but incremental changes continuously in order to achieve an identified improvement. According to Laraia, Moody and Hall (1999) Kaizen is the best approach of identifying and utilizing adequately the skills that a company and its workers already have for positive results that ensures the achievement of fast, obvious and sustainable success. Constant monitoring and evaluation are also used to ensure the sustenance of the adopted improvements. Companies have come to realize that Kaizen is a very important management technique because of its more efficient and faster ways of achieving success. In his study Ortiz (2006) observed that Kaizen philosophy underscores the need to get all the staff of a company involved in its implementation. He stated that it should be incorporated in the daily activities of a firm that is implementing it with emphasis on neat workplace, waste reduction, and increase in quality. Its application leads to successful manufacturing improvements over a long period of time, despite the fact that it yields little changes at its inception. In order to remain competitive and focused in a world of globalization and diverse technologies, the adoption of Kaizen techniques by organizations is one of the most efficient ways of beginning a continuous improvement approach that will lead to positive achievements and production of high quality and innovative products. For Kaizen to be successfully implemented in a company, it requires full commitment and contribution of an entire company s workforce. However, some manufacturers are reluctant to adopt the LPS technique as they argue that it does not allow for easy flow of materials due to disruptions which may hamper the smooth operation of a company. Visual Management In companies that are practicing LPS, the data and information required by the employees for certain period are made available by the management through visual management scheme. It enables workers to have the information they require for the daily manufacturing at their disposal without moving around to other sections, thereby eliminating the transportation waste. Commenting on the crucial characteristic of visual management Nicholas (1998) observed that information about levels of waste, quality, productivity, and service is collected and posted along with goals so that workers can readily see trends and gaps between goals and practice. Visual management was invented by Lean manufacturers as a means of communicating effectively with their employees in order to improve manufacturing processes. It leads to increase in the rate of production and manufacturing flexibility. Single Piece Flow Sometimes called continuous flow manufacturing, Single Piece Flow (SPF) is an essential tool and technique of LPS and can be regarded as one of the best approaches of manufacturing products in a company; it is a one component at a time continuous movement of raw materials and work in progress in a shop floor. Single-piece flow enhances the rate of production, profitability as well as elimination of wastes. However, its limitation lies in its inability to be used in all processes of production especially in manufacturing setups that produces different types of products. 3. CONCLUSION The implementation of LPS tools and techniques by manufacturing companies highly increases their productivity because of the elimination of wastes and reduction in inventory. Also due to the increase in the quality of products, companies that apply the manufacturing principle spend little or no resources correcting defective products. The adoption of the tools and techniques also makes manufacturing to be highly profitable, as a result of fast production of goods and products; also the considerable reduction in lead times and production costs enable organizations to immediately sell their products, beat their competitors and also increase the rate of turnover, thereby maximizing profit. Other factors that contribute to increase in profit in LPS include: low inventory, continuous flow of work, waste elimination, and little or no manufacturing support processes. However, the various tools and techniques will not achieve the desired results if they

6 are not properly utilized; this is because LPS is not just the application of a bunch of tools but rather a completely different approach of manufacturing. REFERENCES 1. Albino, V. and Okogbaa, G. (2001) Computer-Aided Design, Engineering, & Manufacturing: Systems Techniques & Applications, Optimization Methods for Manufacturing Vol. IV, CRC Press LLC, 2. Benhabib, B. (2003) Manufacturing-Design, Production, Automation and Integration CRC Press LLC, 3. Dale, G. (2003) Managing Quality Blackwell Publishing, Oxford, UK 4. Dennis, P. (2002) Lean Production Simplified: A Plain Language guide to the World s most Powerful Production System Productivity Press, New York, USA 5. Dinesh, S. and Vaibhay, G. (2005) Application of value stream mapping for lean operations and cycle time reduction: An Indian case study Production Planning and Control, Vol. 16, iss. 1, pg Hiroyuki, H. (1998) JIT Factory Revolution: A Pictorial Guide to Factory Design of the Future Productivity Press, Massachussets, USA 7. Hines P. (1998) Value Stream Management International Journal of Logistics Management, Vol. 9, Iss.1; Pg.25, 18 pgs 8. Ihueze, C., and Okpala, C. (2012) Application of Taguchi Robust Design as Optimized Lean Production System in Manufacturing Companies Research Journal in Engineering and Applied Sciences 1(1) (2012) 45-50, Emerging Academy Resources, 9. Lang, J. and Hugge, P. (1995) Lean Manufacturing for Lean Times Compendex Journal, Vol.33, Iss. 5; pg Laraia, A., Moody, P. and Hall, R. (1999) The Kaizen Blitz John Wiley and Sons, New York 11. Levinson, W. and Rerick, R. (2002) Lean Enterprise: A Synergistic Approach to Minimizing Waste ASQ Quality Press, Milwaukee, USA 12. McCarthy, D. and Rich, N. (2004) Lean TPM: A Blueprint for Change Elsevier Butterworth-Heinemann, London 13. Nakajima, S. (1998) Introduction to TPM Productivity Press, Massachusetts, USA 14. Nicholas, J. (1998) Competitive Manufacturing Management: Continuous Improvement, Lean Production, and Customer-Focused Quality Irwin/McGraw Hill, USA 15. Ohno, T. (1998) Toyota Production System: Beyond Large Scale Production Productivity Press, New York 16. Ortiz, C. (2006) All-Out Kaizen IIE Solutions Journal, Volume 38; Iss. 4, pg Page, J. (2004) Implementing Lean Manufacturing Techniques Gardner Publications, Ohio, USA 18. Patel, S. Shaw, P. and Dale, B. (2001) Business Process Management Journal Vol. 7, Iss. 1; pg Schonberger, et al, (2000) Technology Management Handbook CRC Press LLC, pg Shingo, S. (1985) A Revolution in Manufacturing: The SMED System Productivity Inc. USA 21. Skinner, D. (2003) Lean and Clean A Better Way to Run Sheet Metal Shops, Books Say Snips. Troy, Vol. 72, Iss.7; pg Standard, C. and Davies, D. (1999) Running Today s Factory: A Proven Strategy for Lean Manufacturing Society of Manufacturing Engineers, USA 23. Shinkle, G. Gooding, R. and Smith, M. (2004) Transforming Strategy Into Success: How to Implement a Lean Management System Productivity Press, New York 24. Strategosinc, [Online]. [Accessed 15 Sept. 2013] 25. Swmas, [Online]. [Accessed 12 Sept. 2013] 26. Womack, J. (2006) Value Stream Mapping Manufacturing Engineering Journal, Vol. 136, Iss. 5; pg Yang, K. and El-Haik, B. (2003) Design for Six Sigma: A Roadmap for Product Development McGraw-Hill, New Jersey, USA