Why Is Lean More Popular Than Six Sigma And The Theory of Constraints?

I think there is much more in common between Lean and the Theory of Constraints (TOC) than we’d like to admit. As big and broad as Lean is, the real benefit of implementing it the right way attacks the same problem with the same benefits as TOC.

And that is in the Value Stream of the Supply Chain. In fact, if you read “Lean Thinking” by Womack and Jones, the first several chapters discuss exactly this: the tremendous opportunity most manufacturing companies have because they are still manufacturing like we were all taught we were supposed to: Optimize local efficiencies, and maximize people and machine utilization, by processes work in batches. Big batches. Keep people and machines as busy as possible, and by gosh, if material is available, get it out on the shop floor, because the faster we get material out on the shop floor, the faster it’s going to come out as finished product, right??

Unfortunately, no.

Both Lean and TOC address this problem in fundamentally the same way: by implementing “pull” of (ideally single-piece) material, instead of “push”ing batches out to the shop floor, in essence, holding back on the release of material until it is necessary to feed the cell or bottleneck resource.

TOC implements Drum-Buffer-Rope (DBR), which by definition attacks this problem head-on. I think a lot of Lean implementations get stuck in 5S, or stop with one or two Value Stream mapping sessions. If you don’t get to the Value Stream Mapping session where you’re including the bottleneck resource, you won’t see the dramatic benefits as outlined in Lean Thinking.

It’s true: Lean is MUCH more popular than TOC. And it has been for a while. When we released our implementation of DBR in our ERP system VISUAL, it was initially called VISUAL DBR. But then we realized from a marketing standpoint, wasn’t going to fly, so we renamed it VISUAL EasyLean  (

But what it really is, under the covers, is DBR, or Simplified DBR, attacking that usually very big opportunity for improvement. To determine HOW big that opportunity is, like in Lean Thinking, we ask a manufacturing company:

1. What’s the lead time you’re quoting customers for your product? (typically, 6 – 8 weeks)
2. What’s the actual touch-time (direct value-added steps in Lean terms) to make that product assuming any and all material, tools, fixtures, machines, people are at the ready?

Answer: typically “a couple/few days”, sometimes “hours”!

There is so much opportunity out there.