Introduction
The steel, automobile and aerospace industries are some of the largest components of American manufacturing; however, they are not the only large industries in the U.S. The forest products industrial sector provides roughly seven percent of all the U.S. manufacturing output, and employs more than 1.5 million people. Forest products generates annual sales of $250 billion. (CollegeJournal, 2006).
Manufacturing in the forest products industry encompasses an enormous variety of products. Manufactured forest product end-items cover an extensive range from plywood and oriented strand board to construction components such as stair rails and treads and risers to musical instruments to kitchen cabinets to furniture. In the furniture manufacturing industry alone, for instance, there is a huge variety of products with many different price points. This extremely large selection of manufactured forest products dictates a variety of manufacturing systems and an even larger set of production processes.
Manufacturing Systems
With intense international competition, the success of a manufacturing company depends on the design of its manufacturing system (Black, 1988). Presently, there are five manufacturing systems being used by industry. The forest products industry uses four of them: Cottage or custom shop, Job shop, Flow shop, and Lean Production. Forest products manufacturing systems run the gambit from the ancient cottage industry producing custom or very small batches of such end products as high end furniture, guitars, and other musical instruments; to the newest manufacturing system, lean production. The lean production manufacturing system increases productivity and quality while reducing costs and maximizing the utilization of the factory’s two most valuable non-depreciable resources—labor and raw materials.
Construction materials such as plywood, joists and wall studs, are produced on highly automated mass production systems. Mass production automatic flow lines are the best systems for production of very high volumes of product. These mass production systems are ideal for high volume production and we see very little change in the future for these systems. However, because of extremely strong off-shore competition in the furniture industry, we will see more and more furniture and wood component manufacturers changing manufacturing systems to lean production in order to remain competitive.
Lean Production
The Lean Production (LP) system is the newest manufacturing system design and it is functionally and operationally different from any other manufacturing system (Black and Hunter, 2003). LP uses less of everything when compared to the job shop manufacturing system—less labor effort, less manufacturing space, less investment in tools, and less design engineering hours to develop a new product. The proper implementation of Lean Production typically means keeping less than half the regularly needed inventory on-hand (Womack, 1991). In addition, the implementation and adoption of LP by a manufacturer results in much fewer defects; and therefore, an increase in quality. The fundamentals of LP are: manufacturing and assembly cells, pull system methodology, 100 percent good quality, on-time delivery every time, and respect for people. Lean Production uses cellular manufacturing for one-piece flow wherever possible in the system. This LP system is flexible while designed to produce superior quality products, on-time, at the lowest possible cost, and on a continuing basis. More and more furniture and wood components factories are converting to LP. Most of these company’s managers believe that they must convert to LP in order to stay competitive in today’s world market place.
Cellular manufacturing and the other lean production subsystems are the cornerstone of the lean production methodologies. Benefits one can expect from full adoption of this manufacturing system include: real productivity gains, improved turn-around time, reduced defect rates, reduced work-in-process inventory, increased production in less floor space, wait time eliminated, reduced expeditors, improved morale, low costs/no costs improvements, and a lean, trim infrastructure.
Cellular Manufacturing
The basic building block of the LP system is the manufacturing or subassembly cell. Typically, the LP system is composed of manufacturing and subassembly cells linked by a pull kanban system that holds and physically controls in-process inventory between cells. In manufacturing cells, processes are grouped according to the sequence of manufacture needed to produce a family of parts or products. In the cell, parts flow by single piece, from machine to machine (or station to station) (Hunter et al; 2004).
Cells are designed for flexibility. To add flexibility, cells are typically arranged in a U-shape so that workers walk the shortest distance from process to process, loading and unloading parts. Cell workers are standing, walking, and multifunctional; thus, they are more productive than the older systems. The cell workers are reducing many ergonomic risk factors that potentially could adversely affect their health (Hunter et al, 2003). In addition, the workers are empowered to make decisions about processing functions; for instance, they have line-stop authority in case their cell has a quality problem.
All the cells in the plant are designed to produce parts when needed. In the LP factory, manufacturing cells produce components for the subassembly and final assembly lines. These upstream cells are designed to provide parts at the rate the subassembly cell or final assembly lines require component parts. Too fast a production rate results in excess in-process inventory; on the other hand, too slow shuts down downstream areas. (Hunter et al, 2004)
Cellular Processes
The LP methodology strives to utilize manufacturing processes that are single-cycle automatics whenever possible. This is not a prerequisite but it is a goal. Single cycle automatic processes that are capable of completing a processing cycle untended. Here, the part is loaded, the process cycle is initiated and the machine turns off when finished completing a production cycle. Single cycle processes include minimal labor requirements, usually require minimal capital investment, and produce parts at the rate needed, thus do not build in-process inventory.
All manufacturing systems require some minimal level of inventory. Unfortunately, many companies carry inventory levels much higher than necessary. However Lean Production works continuously to reach the minimal inventory level. This minimal level is necessary to minimize carrying costs, free up valuable floor space, and avoids scores of expensive storage related problems.
Summary
The forest products industry is an extremely important segment of the American economy, producing six percent of U.S. manufacturing, with sales of $250 billion, and employing 1.5 million people.
Much of the forest products industry’s manufacturing sector is driven by mass production and is heavily automated. This commodity section lead by the construction related forest products will continue to use automation and the flow shop manufacturing system. Meanwhile, we see an ever increasing portion of the case goods, kitchen cabinet, and upholstery furniture industry abandoning the job shop and converting to the lean production manufacturing system.
The lean production manufacturing system increases productivity and quality while reducing costs. Typically, the LP system can be implemented for low or no additional costs. The LP cell design provides several important ergonomic and physiological benefits for cell workers including shortest walking distance, easy communication, minimum work-in-process, and reduced floor space.
Lean production implementation requires a systems-level change for the factory—a change that will impact every segment of the company, from accounting to shipping. Lean Production system implementation is not turning a leaf but rather it is growing a new tree.
References
Black, JT. and S.L. Hunter. (2003). Lean Manufacturing Systems and Cell Design, Society of Manufacturing Engineers, Dearborn, Michigan, 336 pages.
Black, JT., (1988). “The Design of Manufacturing Cells.” Proceedings of Manufacturing International ’88, pages 143 - 157.
CollegeJournal (2006).Manufacturing information by Vault.com, http://www.collegejournal.com/researchindustries/researchindustries/manufacturing-v.html
Hunter, S.L., JT. Black, and R.E. Thomas. (2003). “3D Simulation for Ergonomic Analysis: Colossal Tooling Design.” Ergonomics in Design Journal, Vol. II, No. 1, Winter 2003, 121-135.
Hunter, S.L., S. Bullard, P.H. Steele. (2004). “Lean production in the Furniture Industry: The Double D Assembly Cell.” Forest Products Journal 54(4): 32-38.
Womack, J.P., D.T. Jones, and D. Roos, (1991). “The Machine that Changed the World: The Story of Lean Production.” First Harper Perennial Publishers, NY.
Steve L. Hunter is an Associate Professor and Manufacturing Systems Engineer, Forest Products Department
The Institute for Furniture Manufacture & Management, Mississippi State University, MS 39762-9820
Posted: 21 April 2007
Updated: 23 August 2007
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