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FEATURED ANSWERS:

May 2002

"We want to implement an improvement philosopy, but we can't decide between Lean, Six Sigma and Theory of Constraints. They all seem very powerful but different. How do we decide which is best for us?"

In very broad terms, the different philosophies can be summarised as follows:

Six Sigma focuses on reducing variation, thus achieving more uniform processes and resulting in less waste, less throughput time and less inventory.

Lean Manufacturing focuses on eliminating waste and reducing flow time, thus achieving less variation, uniform output and less inventory.

Theory of Constraints (TOC) as first outlined by Goldratt, focuses on constraints and increasing throughput, thus achieving less inventory and demanding a different accounting system.

Thus the three approaches seem to end up with quite similar results. The differentiating factor could be the speed at which the approach can be accepted into the culture of your organisation.

If your organisation values analytical studies and the relationships of data, charts and analysis, then it will be more comfortable with Six Sigma.

If your organisation thrives on visual change and "right now" time, then it will quickly take to Lean Manufacturing.

If your organisation values a systems approach where full employee participation is not desired or expected, then TOC could be implemented quickly.

For further discussion of these issues,
email us at info@manufacturing-excellence.ie
(or see Nave, D., "How to Compare Six Sigma, Lean and Theory of Constraints", Quality Progress, March 2002)

February 2002

How do you know if you are getting Lean?

Jim Womack (Joint author with Dan Jones of "The Machine that changed the World" and "Lean Thinking") says "I'm often asked by operations managers how they can know if their firm is really getting lean. My answer is simple: Just check your inventory "turns." If they aren't going steadily up, you can be sure you aren't getting lean no matter how many future state maps you may have drawn and how many kaizens you may have conducted."

Inventory turns is simply the ratio of annual sales to Inventory on-hand. It effectively measure how quickly product is getting through your factory to the customer. It is not critical whether you use year-end inventory or an average through the year, as long as your measure is consistent as we are looking for year-on-year increase in Turns.

To read more about Jim Womack's comments see www.lean.org