Conceptual Development of an Introductory Lean Manufacturing Course for Freshmen and Sophomore Level Students in Industrial Technology by Alister Mcleod aamcleod@purdue.edu Department of Industrial Technology Purdue University Abstract: An introduction to lean manufacturing is one of the core courses taken by students majoring in Industrial Technology at Purdue University. The main objective of the course is to familiarize students with the most prominent operations management strategy (lean production/manufacturing) that company s world wide have adopted and are adopting. The course is structured by connecting its content with the context it refers to; that of a problembased context. During the semester, students are exposed to lean concepts and implementation strategies in the classroom and company s respectively. Lecture material spans the core principles of lean, developed by Womack and Jones in their book Lean Thinking, to case studies illustrating its implementation. In the laboratory section of the class students are familiarized with facility layouts and the impact they have on implementation of spatial lean techniques, such as Cellular Layouts, Single Piece Flow, and Work In Progress buffers. In addition, students get a chance to visit two manufacturing facilities at different phases of their lean journey, documenting any room for improvement they might have noticed on the tour. This paper proposes a possible conceptual model for the teaching of an introductory level lean manufacturing course. I. Introduction An introduction to lean manufacturing (IT214) is one of the core courses taken by students majoring in Industrial Technology at Purdue University. The course has been taught for six semesters during the regular school year, and has received an average rating of good by students who have taken the class. Some students have reported that the class has enabled them to speak directly to the operational needs of the companies they have interviewed with and in the process secured jobs. Typically industrial technology students pursuing a bachelor s degree take classes in operations management, control, and material processing. IT214 focuses strictly on the management and control of operations using lean production techniques. The main objectives of the course are to introduce students to: 1) the importance of manufacturing, 2) the differences between traditional and lean manufacturing principles, 3) the background of lean
manufacturing, 4) the purpose of implementing lean, and 5) the lean tools and techniques used in implementation. Accomplishing these objectives takes place in the form of two 50 minute lectures and a 2 hour lab weekly, over a 15 week period. Lean manufacturing/production has been a term that has been in widespread usage since the early 1990 s when Womack and Jones first used it to describe the Toyota Production System. Similar to its predecessors of craft/job shop production, mass production and batch production, lean production is a generic term that is used to imply a particular way of going about the manufacture of a particular product. Henry Ford s insight of lowering the expense associated with making a product by shorting the production cycle times is similar to that of lean production. A lean production manager is challenged to find new ways to increase the productivity and efficiency of their business. Because manufacturing environments vary due to differences in their purpose, design and control, there is no single set of management procedures that can be universally adopted to govern them (Hayes, Pisano, Upton, & Wheelwright, 2005). However, lean production provides us with a starting point for viewing a company s operating practices with the final goal of seeking operational improvement. Manufacturing managers are responsible for demonstrating a sound understanding of their manufacturing systems, in order to create work environments that are creative, competitive, and continuously improving (Hopp & Spearman, 2001). It therefore means that operations managers hoping to join to workforce will have to be able to replace their ageing counterparts and also continue the lean revolution (Linford, 2007). The college of technology, at Purdue University, has developed an introductory course to lean production/manufacturing for freshmen and sophomore students in hopes that a better educated workforce will be present to undertake the continuation of the lean revolution. II. Conceptual design for IT214 In the development of a curriculum, developers often struggle to structure learning experiences, in such a fashion, that the content and context will maximize learning (Putnam, 2001). The technique employed in developing and teaching the course content for IT 214 is that of Problem-based learning (PBL). PBL is an instructional approach that uses real world problems to reinforce the theory introduced initially in the learning process. Using realistic examples, allows the development of critical thinking, problem solving and self-directed learning skills. Knowledge and skills, needed by industrial technologists, are dynamic and constantly interacting with several other fields of discipline. PBL gives students a unique opportunity to explore all the options and evaluate the resulting solutions based on a particular concept. This allows them to learn skills that overlap or compliment other areas under investigation. Using PBL to teach lean manufacturing has allowed for students to come to grips with the complexity of the technique, and also to understand that it is not a solution for all problems manufacturers encounter in their daily operations ( & Savoy, 2009). Lean production encompasses a wide variety of operation management practices such as just-in-time (JIT), quality systems, work teams, cellular manufacturing, supplier management etc. which are all dependent on each other to work (Shah & Ward, 2003). This inborn
characteristic of lean production makes course development difficult to be expanded outside the bounds of a conceptual point of reference. Therefore, the conceptual bounds that are used in the creation of IT214 are comprised of a theoretical and empirical structure. The theoretical nature of lean is explained by its mathematical underpinnings which describe the underlying concepts of level scheduling, inventory control, and capacity determination. The empirical nature of lean is made up of observed characteristics that are not easily defined or measured. Researchers, who do empirical studies of lean, seek to develop and synthesize current knowledge by explaining the different concepts they observe in companies they visit or survey (Shah & Ward, 2007). These studies provide insight into lean operations and are also a key ingredient for explaining the lean implementation process. Most instructors who cover lean manufacturing, however, tend to gloss over loosely aggregated knowledge about lean manufacturing short changing their students by not delving into the theoretical or empirical underpinnings of the technique. Course development is therefore broken into two categories: 1) a conceptual world and 2) an empirical world. These two categories are measured based on their levels of abstraction and their method of measurement/evaluation. In figure 1, the conceptual world is higher on the level of abstraction, represented on the y-axis. The conceptual world is philosophical in nature and it is made up of the conceptual definition and principles of lean production. On the x-axis, the method of measurement refers to the simple metrics used to measure leanness that are taught in IT 214. The tools or practice orientation makes up the empirical world and it is also divided into two categories, a qualitative and a quantitative. The more detail that is required in the measure of a tool or a practice is the more quantitative in nature it will be. The tools and practice orientation is comprised of lean s operational definition and measurement variables used to monitor leanness. The philosophical and the tool orientations are indirectly related to each other through conceptual and operational definitions, the principles of lean and measurement variables. Separation of the conceptual and empirical world now makes possible the division of course work into three main headings, the roots of lean, factory physics and lean tools. Figure 1: Conceptual design for IT214
III. The conceptual definition of lean manufacturing Lean manufacturing can be best described as a combination of the best techniques of mass and craft production. According to Womack and Jones (1996) those techniques are the ability to provide a customer with a wide variety of products, at the right time and place, at the lowest cost and the highest quality. With a complex definition for lean production, it is therefore prudent introduce novice learners to a history of manufacturing systems. Several types of production classification schemes exist; however, the simplest is that of continuous versus intermittent processes. Intermittent processes tend to describe the way products that are discrete in nature, such as, cars, planes, and ships, are made. However, if a high demand is present for such products they could easily be produced in a continuous manner. Products made in craft production systems are classified as being intermittent and discrete in nature while those in mass production systems could be both discrete and continuous and non-discrete and continuous. Nondiscrete products are those with a propensity to flow, such as, chemical products. These products when being produced are produced in a true continuous fashion, therefore no stoppages, until they are made. Craft production enables the manufacture of a wide variety of products at a low volume. Using this method of production meant that a skilled craftsman, using only simple tools, was capable of producing a vast variety of products and designs involving a number of different skills. The main disadvantages with this form of production are that, the quality of the product is dependent on the level of the craftsman s skill, low production volume, and high production costs (Wild, 1972). Mass production, on the other hand, utilizes several low skilled workers in purposeddesigned facilities to produce products considered to be continuous or continuous over a limited, but substantial period of time (Cohen & Apte, 1997; Wild, 1972). In its modern form, mass production is achieved by the adoption of different production principles, which is spurred on by the increased access to mechanized forms of production. Two strands make up mass production, quantity and flow production, which are hierarchically separated into three subgroups (See Figure 2). These strands represent the two main forms that mass production can be carried out under. In the first strand, quantity production, large amounts of equipment or laborers are used to undertake the mass production of goods that are simplistic in their design and manufacture. In the second strand flow production refers to the mass production of goods that are complex in nature and require more than one piece of machinery (Wild, 1972).
Figure 2: Taken from Wild, 1972 Flow production is a different type of mass production technology and one that is central to the lean manufacturing philosophy. In particular discrete item flow lines are focused on in detail, given that it is the third stage of the systematic implementation of lean manufacturing. Flow processes refer to the manufacture of complex non-discrete items such as chemicals. This form of mass production is not covered in IT214 as scholars and practitioners alike are not sure how lean production could be implemented in such a manufacturing process (Abdullah, 2003). Concluding this phase of the course is the introduction of the lean manufacturing philosophy. Lean manufacturing is achieved by incremental improvement and the adoption of more efficient technologies (Hayes et al., 2005). Incremental improvement is achieved by the adoption of the principles of lean. The principles as stated by Womack and Jones (1996) stipulate that five tenets have to be systematically followed in order to achieve lean production. These tenets are, value identification, value stream mapping, flow production, pull production and then perfection (See Figure 3). Value identification is a process in which the continuous improvement team, which is comprised of workers in the process, outside experts, and customers all come together to identify aspects of the product that are of most importance. Value stream mapping then follows, and it involves the identification of tasks that add no value to the product during manufacture. Flow production, which is similar to discrete item flow production, seeks to increase the speed of the manufacturing process. Pull production comes after flow production as now the system is more responsive to demand pressures. Once there is a direct link between a product and customer the process starts over via continuous improvement.
Figure 3: The principles of lean production V. Measurement Variables (Factory Physics) The factory physics section of IT214 explains the metrics necessary for the monitoring of lean implementation. It represents the monitoring of the key measures of cycle time, throughput and work-in-progress (WIP). These measures are related to each other by little s law which states that at every WIP level WIP is equal to the throughput times the cycle time. Little s Law - WIP TH CT The law shows the direct and indirect relationship that WIP and cycle time have on throughput. However, this relationship is not perfect in its true sense and thus has to be explained. The direct relationship of throughput and WIP is only feasible up to the point of critical WIP. At critical WIP the throughput is at its maximum, however WIP can continue to increase. This breakdown in the relationship exists, due to a limit on throughput capacity in a manufacturing line, which is further determined by the technical and social specifications of the operation. Another, assumption that the law makes is that variability, that may occur from customers or other internal operations, are not present. The law itself is simplistic in nature but is a rough view of how many manufacturing systems function. Little s Law provides a means by which one can observe continuous improvement events that deal with a reduction in processing inefficiencies. Five uses of the law occur in circumstances that determine queue length calculations, cycle time reduction, measurement of cycle time, planned inventory, and inventory turnover times. The applicability of the law appears in scenarios that are not just micro scaled but also in operations that are at the macro level; therefore, applications to individual operations can be made as well as to multiple operations. The law lends itself to three particular parameters that can be used in judging an operation s
efficiency namely; best-case performance, worst case performance and practical worst case performance. In the best case scenario there are two conditions, one for the WIP in an operation being at or above critical WIP and another for it being below. Both cycle time (CT) and throughput (TH) can be described by these conditions (see equations below). The variables in the equations are r b, which is described as the bottle neck rate, T 0, raw process time and w 0, critical WIP. For conditions that are considered worst case scenarios there are also two equations that describe these states. The state of worst case can only be achieved in instances where there are multiple operations performing a single job amongst themselves, see equations below. CT worst wt 0 TH worst 1 T 0 The states of best and worst case scenarios are idealistic in nature therefore, therefore a practical worst case (PWC) scenario is one that describes the real world accurately. PWC values allow practicians of lean to make a jugdement about whether or not maximum efficiency has been achieved. Throughput values below PWC throughput and cycle time values above PWC cycle time are considered bad as there is still room for improvement. For throughput values above the PWC and the cycle time values below those of cycle time PWC there are then no room for improvement (See equations below). CT PWC w 1 w T0 TH PWC rb rb W0 w 1 VI. Tools of Lean Eight tools that embrace the concept of lean manufacturing are utilized in IT214. They are cellular layouts, single minute exchange of die (SMED), Andon boards, Jidoka, Heijunka, Six-sigma, Kanban systems and poka-yoke (See figure 4). Using these concepts, aids in bridging the gap between the empirical and conceptual worlds. Empirical and conceptual worlds are bridged when students are taken out on plant tours and hands on laboratory sessions allow for the observation of the effects of process improvement. Simulations allow for the calculations of efficiency, as it relates to these concepts, to be presented in an observable manner. Plant tours actually provide students with access to practitioners, who highlight the benefits they have noticed in lean implementation.
Figure 4: Concept map of lean production Cellular layouts, for example, refer to the arrangement of assembly line operations into small U-shaped cells. Being spatial in nature, cellular layouts are quite easy to explain to students with the use of illustrations, to show how much walking distance an assembler might have to in a typical shift and the cost saving to be derived from it. Single minute exchange of die (SMED) is a bit harder and is typically reserved to be discussed at the end of the semester when the students have to be familiar with more underlying concepts of lean production. SMED is a technique used to reduce lot sizes in a manufacturing operation that typically makes products in batches. The lean idea here is that less money will be wrapped up in work-in-progress inventories, so that if a product becomes obsolete during production not much money is lost. Andon boards are signal systems that are employed to notify operators about the status of the system (i.e. assembly line) they are working in. This concept is a bit hard to explain, but there are plant tours during the semester to re-enforce the explanation given in class. Jidoka or autonomation with a human touch is another concept that is very integral to lean production s definition. By giving automated machinery the ability to identify problems with their own work, gives them the ability, not only to detect problems but also to correct them if they are capable of doing so. Heijunka is another concept that is taught, and this concept refers to the way in which jobs are scheduled. By keeping the production constant, variability that is due to sporadic customer demand does not force the assembly line to have work-in-process when demand is low and too little when demand is high. Little s law of variability buffering is used to re-enforce this concept. Six-sigma is another manufacturing improvement strategy that has gained widespread usage. However, incorporating the six sigma concept in IT214 has allowed for the discussion on how quality is monitored in assembly lines and there benefits of doing so
at, the manufacturing stage of the products life cycle versus on the customers side. Kanban systems are lot/batch control techniques used to re-enforce Heijunka and SMED techniques in the maintenance of a constant work flow throughout the assembly line. Poka-yoke or mistake proofing systems are used to prevent both humans and machines from making mistakes. This concept is best explained with the examples, such as, a microwave oven turning itself off when someone opens its door. Utilizing these underlying concepts of lean production has made the teaching of lean production easier to accomplish. Simultaneously, while these concepts are being explained, the systematic continuous improvement strategy used by lean practitioners is highlighted. VII. Conclusion This paper provides the blue print from which a successful introductory course can be taught to students who are in the formative years of their educational careers. These students tend to lack an understanding of manufacturing operations, thus, a combination of manufacturing theory and practice is necessary for learning to occur. A conceptual model allows the class is to be view from two perspectives, that of an empirical perspective and that of a conceptual view. The two views are intertwined by the use the problem-based learning strategy that enables students to learn at their own pace. Lean manufacturing in industry and academia is loosely defined and thus, this course presents a starting point from which manufacturing systems and their related productivity improvement strategies can be followed. (Womack & Jones, 1996)
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Biography Alister Mcleod holds a Master s of Science Degree in Industrial Technology from Purdue University, which he obtained in May 2005. In 2003, he received his Bachelor of Science summa cum laude in Electronic and Electrical Technology from North Carolina Agricultural and Technical State University. Currently, Mr. Mcleod is pursuing his doctoral degree in Industrial Technology with a focus on the implementation of lean manufacturing improvement strategy implementation in small to medium size manufacturing facilities. His current research interests will make contributions to the sustainability of lean improvement strategies for first time implementers of lean. In essence, his research will aid in the training of a modern manufacturing workforce to cope with both internal and external competitive pressures. At the master s level, his main research focus was on the implementation of lean manufacturing strategies for electronic circuit manufacturers using electrically conductive adhesives as a substitute for lead free solders. This has lead him along a path of developing and teaching an introductory lean manufacturing course for sophomore level students at Purdue s College of Technology. On April 17 th 2008 he was presented with the Purdue university graduate student award for outstanding teaching.