The Goal

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making use of the resource in a way that moves the system toward the goal. "Activating" a resource is like pressing the ON switch of a machine; it runs whether or not there is any benefit to be de- rived from the work it's doing. So, really, activating a non-bottle- neck to its maximum is an act of maximum stupidity.

"And the implication of these rules is that we must n o t seek to optimize every resource in the system," says Jonah. "A system of local optimums is not an optimum system at all; it is a very ineffi- cient system."

"Okay," I say, "but how does knowing this help us get the missing parts unstuck at the milling machines and moved to final assembly?"

Jonah says, "Think about the build-up of inventory both here and at your milling machines in terms of these two rules we just talked about."

"I think I see the cause of the problem," Stacey says, "We're releasing material faster than the bottlenecks can process it."

"Yes," says Jonah. "You are sending work onto the floor whenever n o n -bottlenecks are running out of work to do."

I say, "Granted, but the milling machines are a bottleneck."

Jonah shakes his head and says, "No, they are not-as evi- denced by all this excess inventory behind you. You see, the mill- ing machines are not intrinsically a bottleneck. You have turned them into one."

He tells us that with an increase in throughput, it is possible to create new bottlenecks. But most plants have so much extra capacity that it takes an enormous increase in throughput before this happens. We've only had a twenty percent increase. When I had talked to him by phone, he thought it unlikely a new bottle- neck would have occurred.

What happened was that even as throughput increased, we continued loading the plant with inventory as if we expected to keep all our workers fully activated. This increased the load dumped upon the milling machines and pushed them beyond their capacity. The first-priority, red-tagged parts were pro- cessed, but the green-tagged parts piled up. So not only did we get excess inventory at the NCX-10 and at heat-treat, but due to the volume of bottleneck parts, we clogged the flow at another work center and prevented non-bottleneck parts from reaching assembly.

When he's finished, I say, "All right, I see now the error of