Developing A Manufacturing Plant Layout Utilizing Best In Class Concepts Of Lean Manufacturing And Theory Of Constraints Of Optimal Macro Flow

Developing a plant layout for a manufacturing facility is a project that utilizes a combination of art and science. Although creating plant layouts has been an activity that has been performed by manufacturing and industrial engineers for decades, there is no one set formula or method that will ensure achieving the best possible optimum outcome. Many manufacturing companies are striving to adopt lean production techniques that eliminate waste to enhance flow of products through their production facilities. Tools utilized to implement lean production techniques include: kanban, supermarkets, first-in first-out (FIFO) lanes, pacemaker processes, management time frames, etc. Numerous companies are also implementing theory of constraints (TOC), which is a management philosophy to meet customer demand through synchronized production, to enhance flow of products to generate money for the corporation at an expedited rate. TOC utilizes tools like drum-buffer-rope (DBR), throughput accounting, and constraint management to achieve this. Although, companies are striving to implement lean manufacturing and TOC trough the implementation of the above mentioned tools, they miss out on implementing an optimized macro-flow in their facilities. Macro-flow is the optimization of the entire flow within the facilities of a company, which allows them to avoid sub-optimization within narrow departments or functional areas. Lean manufacturing and TOC stress the importance of maintaining a consistent macro-flow within the entire manufacturing facility for products, to achieve the highest impact in improving the productivity and profitability of a manufacturing plant. For creating the most optimum macro-flow within a facility, dimensionless block diagrams have been used by plant layout engineers. However, the way these dimensionless block diagrams are created and implemented have a lot of subjectivity built into them. This paper suggests an objective means using weightages to create the dimensionless block diagram to reduce the substantial subjectivity that creeps into the creation of the dimensionless block diagrams. With the proposed method, facility planners will be better able to optimize the macro-flow in a manufacturing facility as necessitated by lean manufacturing and TOC principles. Plant Layout as Practiced Today Industries have attempted to create efficient plant layouts since the dawn of industrialization, and many methods have been utilized by industrial, production, and manufacturing engineers to come up with the most efficient plant layout. However, there is not a set methodology that can be repetitively applied to all plant layout exercises so that they turn out as the most efficient plant layout. In this sense, creating of plant layouts is more of an art than a science 1,2,3 . P ge 13386.2 To aid in coming up with the best layout, one needs to search for alternative solutions which should push one to become creative in coming up with a solution that is most efficient. Kirck 3, 4 has summed up these efforts in a worthy to repeat manner, which have been elaborated below: 1) Exert the necessary effort to come up with an optimized solution. This needs to be done by allocating ample time to address the problem, and forcing oneself to concentrate fully on the problem during that time. 2) Do not get bogged down in details too soon, but also do not suggest solutions with no back up technology. An example 3 of this is one operation research analyst who supposedly during World War II suggested that the German submarine force could be destroyed by boiling the ocean. When asked how that could be done his response was, “I come up with solutions that others need to figure out how to implement.” 3) Ask ample questions on the forefront to highlight the problem from multiple angles. The simple questions of what, who, when, where, which, how, and why go a long way in achieving this. 4) Seek several alternatives and avoid premature satisfaction. Falling in love with a design early on hampers incorporation of better ideas later on, and makes the plant layout engineers defensive when challenged on their assumptions. Having various options allows the management team to mix and match several aspects from differing layouts based on constraints that they would like to keep in creating a new layout. 5) Avoid conservatism. Not thinking outside the box for things that have not been attempted by anyone restricts the firm from making quantum leaps in improving their productivity and profitability. Attempting to tweak what is presently available pushes a firm into simple variations of the present layout resulting in little or no payoff for the effort expended in improving the layout. 6) Avoid premature rejection. Rejecting an idea without letting others contemplate and build on it, can make a firm lose good ideas. An idea which is presented as part of a brainstorming session never has all aspects tackled when it is initially presented. Only on subsequent thought can the shortcomings and weaknesses of an idea be appropriately addressed if the benefits of the idea are substantial. 7) Benchmark—learn how others have done it. A good source for how people have solved analogous problems is to consult trade magazines, websites, libraries, and by talking with trade peers as to how they have solved problems of similar layout. 8) Try the group approach, but at the same time remaining conscious of its limitations. Brainstorming, involves a small group of people who have diverse knowledge to allow ideas to flow from to come up with the most efficient layout. Initially, no criticism of the ideas is allowed to be able to generate and capture all ideas that the participants have, and then begin the evaluation process to cull the ones that are totally infeasible. Building on each others ideas is encouraged to allow better ideas to flow. Limitations of the idea P ge 13386.3 generation method can be using the wrong experts who do not have adequate exposure to other industries to allow them to cross pollinate ideas from other fields. With all these rules of thumb too, “many of today’s layouts are the product of evolution rather than careful design 3 ”. This stems from the size and the nature of the problem itself. Unless a person like Charles Sorensen 5 , Vice-President of Production for the Ford Motor Company, is involved in creating a plant layout using experience and rules of thumb, you have to repeat the exercise several times before getting it correct. Sorensen’s story of how he created the production facility to assemble the B-24 Liberator bomber during World War II is worth revisiting to learn what can be described closest to a method for creating a plant layout. The established B-24 bomber facility was assembling an airplane a day, and there was felt a need to increase production to 25 bombers a day. Sorensen, using his 35 years of experience in designing and building manufacturing plants was able to envision how the plant should be structured after an overnight thinking spree on the day he and Edsel Ford visited the old bomber manufacturing facility. The proposed macro-flow of the plant was created by Sorensen on a piece of paper, and was accepted and signed by Edsel Ford. Eventually, the US Government funded the two-hundred million dollar manufacturing plant from which 8,800 B-24’s rolled off the assembly line in six years with over 34 thousand employees working at its peak employment level of what came to be known as the Willow Run Bomber Plant that was located near Detroit. The one principle that Sorensen kept in mind in designing the plant was smooth flow of the product throughout the manufacturing facility, which is most often mentioned today as the core lean manufacturing and TOC principle. The entire plane's design was broken down into essential units and a separate production layout was created for each unit 5 to create overall optimum flow. The production of the entire plane was next arranged so that only the required number of units are built and delivered in the proper sequence to the assembly line to make the finished plane. Optimizing Macro-Flow in the Plant Macro-flow can be defined as the flow of raw materials and information from the point they enter a manufacturing facility and gradually become a product, to the point where the finished product leaves the factory. Many times, only the flow within the actual production shop has been optimized with little attention paid to the multiple times that the raw material, information, inprocess parts and the finished product are moved beyond the flow in the production shop. To enhance macro flow with in the entire factory, departments and functional cells need to be positioned such that the flow in the entire factory is as efficient as can be. For optimizing the macro-flow, a method that has been used to ensure that the functional departments that carry the majority of the flow are positioned closed to each other is called the dimensionless block diagram 1 . P ge 13386.4 Figure 1. Traditional Dimensionless Block Diagram 1 In the traditional method of creating the dimensionless block diagram, the functional departments, production work-cells, and cost centers are identified, and how information needed for the manufacture of the products, people, and products should flow through them is captured in a matrix. Next, based on the experience of the employees, a matrix showing the importance of locating two departments or work-cells close to one another is created as shown in Figure 2. The “AEIOU-X” scale is used to assign importance in locating two departments or work-cells close to each other: A is assigned where it is absolutely essential to locate two departments close to each other, E is essential, I is important, O is ordinary importance, U is unimportant, and X is to not locate close to each other. Figure 2. Activity Relationship Diagram With Importance Categories W e ig h ta g e