Lean Manufacturing Basics

Lean Manufacturing, a process-management system created by Toyota Production Systems in the 1950s and 1960s, “supports profitable growth by improving productivity and quality, reducing lead times and freeing resources,” says Chet Marchwinski, communications director for the Cambridge, Mass.-based Lean Enterprise Institute Inc. (www.lean.org).

Lean’s three guiding principles involve purpose, process and people. “The primary purpose of any organization—and first step in any Lean thought process—is to correctly specify the value that the customer seeks, in order to cost-effectively solve the customer’s problems, so the organization can prosper,” he explains.

Once that’s settled, companies must focus on the process, or value stream, used to achieve this objective, Marchwinski says. “Generally, this is the combined result of three processes: product and process development, fulfillment from order to delivery, and support of the product and the customer through the product’s useful life.”

People power

Next, address the people part of the equation. “Make someone responsible for each value stream,” Marchwinski recommends. “This value-stream manager must engage and align the efforts of everyone touching each value stream to move it steadily toward the customer, while elevating performance from its current state to an ever-better future state.” That requires three things, he says. One is a master plan for the enterprise, often called strategy deployment. Another is frequent improvement cycles for each process. The final is standard work with standard management for every step in each process.

To describe workplace practices conducive to visual control and Lean production, Lean employs the 5S method, based on five Japanese words that, when translated, begin with the letter S. Seiri is separating needed from unneeded items, then discarding the unneeded. Seiton is neatly arranging what’s then left—“a place for everything and everything in its place,” Marchwinski explains. Sesiso is cleaning and washing. Seiketsu is “cleanliness resulting from regular performance of the first three Ss,” he notes. Finally, Shitsuke is discipline to perform the first four Ss. He notes that the Five Ss often are translated as sort, straighten, shine, standardize and sustain. However, some Lean practitioners add safety, which means to establish and practice safety procedures in the workshop and office.

Production is characterized as either push or pull. “Push refers to processing large batches of items at a maximum rate, based on forecasted demand, then moving them to the next downstream process or into storage, regardless of the actual pace of work in the next process,” Marchwinski says. But, he notes, such a system “makes it virtually impossible to establish the smooth flow of work.”

Pull refers to a method in which downstream activities signal their needs to upstream activities. The method strives to eliminate overproduction, says Marchwinski. And it’s one of three major components of a complete just-in-time, or JIT, production system, he states.

Three basic types of pull exist. One is supermarket, the most basic and widespread system. “Each system in each process has a store—a supermarket—that holds an amount of each product it produces. Each process simply produces to replenish what is withdrawn from its supermarket,” Marchwinski explains. The second type, sequential, finds use when there are too many part numbers to hold inventory of each in a supermarket, he says “Products are essentially ‘made-to-order’ while overall system inventory is minimized.” The third type, mixed-supermarket-and-sequential-pull, may be used “when an 80/20 rule applies, with a small percentage of part numbers accounting for the majority of daily production volume,” he remarks.

While there is more terminology to Lean Manufacturing, what’s important is that Lean improvement efforts must connect to organizational management, and solutions to key business problems, Marchwinski states. “Otherwise, early gains, even if substantial, will be difficult to sustain.” Translated: “Backsliding to old ways of working” is at or near the top of leading obstacles to true Lean operations. 

C. Kenna Amos, ckamosjr@earthlink.net, is an Automation World Contributing Editor.
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