The Goal

221

my marital difficulties, the inventory problem at the plant seems simple-or at least it seems simple now. I guess every problem is easy once you've figured it out.

We are, in effect, going to do what my two kids came up with. The Herbies (the bottlenecks) are going to tell us when to let more inventory into the system-except we're going to use the aid of computers instead of drums and ropes.

After we returned to the conference room in the office build- ing today, we started talking, and we all agreed that we're obvi- ously releasing too much material. We don't need five or six weeks of inventory in front of the bottleneck to keep it produc- tive.

"If we can withhold materials for red parts, instead of push- ing them out there as soon as the first non-bottleneck has nothing to do," said Stacey, "the milling machines will then have time to work on the green parts. And the parts we're missing will reach assembly with no problem."

Jonah nodded and said, "That's right. What you have to do is find a way to release the material for the red parts according to the rate at which the bottlenecks need material-and strictly at that rate."

Then I said, "Fine, but how do we time each release of mate- rial so it arrives at the bottleneck when it's needed?"

Stacey said, "I'm not sure, but I see what you're worried about. We don't want the opposite problem of no work in front of the bottleneck."

"Hell, we got at least a month before that happens, even if we released no more red tags from today on," said Bob. "But I know what you mean. If we idle the bottleneck, we lose throughput."

"What we need," I said, "is some kind of signal to link the bottlenecks with the release-of-materials schedule."

Then Ralph, to my surprise, spoke up and said, "Excuse me, this is just a thought. But maybe we can predict when to release material by some kind of system based on the data we've kept on both the bottlenecks."

I asked him what he was getting at.

He said, "Well, since we started keeping data on the bottle- necks, I've been noticing I'm able to predict several weeks in advance what each bottleneck will be working on at a particular time. See, as long as I know exactly what's in queue, I just take