As a manufacturer you need to make products faster, better, and cheaper. Lean Manufacturing and Six Sigma are two ways to achieve these goals, but how do you select the best
approach?

You don’t have to choose. Many companies are merging Lean Manufacturing and Six Sigma methods into a comprehensive approach to improvement.

Whittling away waste
Lean Manufacturing focuses on reducing waste. Using a flowchart-like tool called value stream mapping, you map out all the activities needed to make a product. Your team then works on improving “flow” and making the manufacturing process as efficient as possible.

Lean Manufacturing emphasizes quickly eliminating obvious sources of waste by focusing on processes. For instance, a Wisconsin manufacturer that makes panels for car dashboards applied Lean Manufacturing and discovered that materials were located too far from the manufacturing cell where they were needed. A simple relocation solved the problem. Lean Manufacturing is well suited for situations where a company is seeking immediate and/or visual changes.

Getting consistent
Six Sigma, on the other hand, aims at reducing variation with the ultimate benefit of improving quality by reducing defects. To reduce variation you use a five-step, systematic method known as DMAIC (see comparison chart for details). Six Sigma depends on in-depth statistical analysis, data, and experiments. It’s best used when you need to solve a complicated problem.

For example, Ford Motor Company used Six Sigma to reduce hood defects on Ford Mustangs after many customers complained that the hoods were too hard to latch. Ford implemented Six Sigma tools including simulations, process mapping, and line trials to help redesign a support bracket and improve installation of the hood latch. Ford expected these changes to reduce hood defects by 97 percent and save $283,000 a year.

The Lean & Six Sigma advantage
Lean Manufacturing and Six Sigma have different aims. Lean thinking aims at removing waste, which speeds up the manufacturing process and cuts lead-time. Six Sigma focuses upon improving product quality and reducing costs. These are complementary goals, and when the two approaches are combined, Lean & Six Sigma can be a powerful improvement tool.

Michael George, author of “Lean Six Sigma: Combining Six Sigma Quality with Lean Speed,” points out that quality problems and manufacturing delays are related: “10% scrap can slow down a factory by 40%,” he writes. By applying Lean & Six Sigma, companies can reduce defects and lead-time. This synergy can cut overhead by 20 percent and inventory by 50 percent.

Wisconsin company combines approaches
Lean & Six Sigma also helps focus improvement projects. A Wisconsin company that makes parts for commercial lawn care products needed to speed up assembly. They applied Lean Manufacturing principles and created a comprehensive value stream map.

The company then used Six Sigma to discover key problems. They found a bottleneck at a punch press, large lot sizes, and poor equipment placement. “The complexity of the value stream map made six sigma tools valuable,” says Brenda Kujawski, manufacturing specialist with WMEP. “It helped us focus much more effectively.”

But lean thinking provided a much-needed big picture. “That may sound like a simple point. But before value stream mapping people would point to a couple of big issues they were aware of and just focus on them,” she says. Initially, without this combination, lean practitioners would only pick the “low-hanging fruit.” Now, they can explore issues more in-depth.

Synergistic tools
Lean & Six Sigma is like having a wide angle and a telephoto lens. Lean thinking lets you see the big picture, while Six Sigma zooms in on problem areas. Lean thinking is system focused, easier to implement, and gives quicker results, while Six Sigma is issue focused and can handle more complex problems. The combination of Lean & Six Sigma gives you the best of both worlds.

WMEP Manufacturing Specialist Tony Gischia says that Lean & Six Sigma is the future for improving manufacturing operations. He’s seen companies save hundreds of thousands of dollars by combining the two approaches. The trick is selecting the right tools for the project. “Both lean and six sigma are toolboxes,” he says. “WMEP can help companies build the toolbox that’s customized for them and maximizes their benefit.”