Picture-perfect manufacturing: the vision of a production process with little or no waste is the inspiration behind lean manufacturing. Value stream mapping is a graphical tool that this contract manufacturer uses to create that vision

Modern Machine Shop, July, 2004 by Mark Albert

Pictures can lead us to understanding. Consider the dramatic images Michelangelo created on the ceiling of the Sistine Chapel. The climactic events of man's creation, fall and redemption are depicted in bold shapes and vivid colors. These scenes do more than tell a story. They show us how good and evil vie for the living soul and how grace ultimately prevails over sin.

We can use pictures to help us understand what should happen on the factory floor, too. Of course, these pictures will look nothing like an artist's masterpiece, yet the comparison is not as farfetched as it may seem.

Manufacturing is the uniquely human effort to impose a functional design on raw materials, to create value by transforming featureless shapes into objects ultimately intended to meet some need or want. Just as Michelangelo was preoccupied with the moral straggles underlying human experience, manufacturers con tend with the never-ending challenge to make manufacturing processes more efficient and profitable. This means finding and eliminating waste. Waste is the devil in disguise on the shop floor.

One technique that uses pictures to help manufacturers find and eliminate waste is value stream mapping. It is a graphical way to analyze where value is--or isn't--being added as material flows through the production process. Using a set of icons and symbols, the analyst depicts what happens at each step of the process, tracing the path that material and information must follow for finished products to reach the customer. By capturing and representing details about every activity, the resulting diagram makes it clear where production leadtime is out of synch with processing time. This picture would show, for example, why a part that is worked on for only 1 hour still needs 10 days to travel through the shop.

By drawing a new picture that shows how workstations and activities can be rearranged to avoid overproduction, excess inventory, unnecessary handling and pointless waiting, planners can envision a path by which customer orders can be filled in less time with less inventory and fewer workers.

Moving in this direction is the essence of lean manufacturing. Value stream mapping gives the manufacturer a "grand vision" into which waste reduction, continuous improvement and other lean techniques must fit. Without this vision, a company may end up with numerous isolated fixes that don't add up to significant savings extending to the bottom line or providing benefits to impress and gratify customers. Value stream mapping organizes the lean manufacturing experience and gives it meaning. This is the art behind waste-free production processes.

Stremel Manufacturing (Minneapolis, Minnesota) is a company that has been using value stream mapping for a number of years now. Stremel is a contract manufacturer of sheet metal fabrications, precision machined components and assemblies, with a long history of service to aerospace, defense and commercial customers. Some of its work represents long-term contracts, while other work, primarily in CNC machining, consists of short-run jobs. Although no one company can illustrate all that value stream mapping is or can do, Stremel's experiences provide more than a glimpse of the technique's usefulness and flexibility, especially in a classic contract manufacturing setting.

Seeing How It Is

"We started our journey to lean manufacturing in 1999," recalls Darin Andries, business development manager at Stremel. At the time, the company was encouraged to participate in several lean manufacturing workshops sponsored by one of its large corporate customers. "One of the first things we learned was that value stream mapping gave us a customized blueprint for becoming a lean manufacturing enterprise. It helped us see where we were, where we needed to go and how to get there in an orderly fashion," Mr. Andries says. He and other managers worked with lean manufacturing consultants from TechSolve (Cincinnati, Ohio) to hone their lean manufacturing skills.

Mr. Andries would laugh if you described him as Stremel's own Michelangelo, but he has become one of the chief value stream mapping artists at the company. Figures 1 and 3 show value stream maps that represent one of the first applications at Stremel. Because this production process involved a product protected by confidentiality agreements with the customer, Mr. Andries created simplified "generic" value stream maps based on the real ones to illustrate some basic concepts about value stream mapping.

[FIGURES 1,3 OMITTED]

Figure 1 is the current state map. It shows how the shop originally fabricated a sheet metal component. Some of the main processes on the map are welding, assembly and painting. These are represented by standard mapping icons such as process blocks, data boxes and inventory triangles. The icons and symbols follow the conventions established by Mike Rother and John Shook in their book, "Learning to See" published by the Lean Enterprise Institute (Brookline, Massachusetts, www.lean.0rg). This book did much to popularize the technique of value stream mapping in the United States, but the concepts were largely derived from the authors' experiences with the Toyota production system.