Critical Chain - Eliyahu M. Goldratt [93]
"And then subordinate. Subordinate all the other resources to it."
"And what is the result?" I ask. I am getting good at asking rhetorical questions. Rhetorical to these students who have learned it from Johnny.
"By that," Charlie replies, "you have removed most of the overloads from the other resources. And the sporadic peaks of load that still exist can be absorbed by the buffers."
"Exactly," I say triumphantly. "Why don't we do the same in projects?"
"But in projects we don't have a bottleneck," Ted reacts too quickly.
"Really?" Mark asks ironically. "In your company you don't have a bottleneck? Remember, we are not talking about one project; we are talking about all of them together."
"I see."
"And what is the impact of not acknowledging such a bottleneck?" I ask. "It's not just that it creates havoc synchronizing between the projects. You will get the same devastating impact we get in production. Not paying special attention to the bottleneck, not protecting it from Murphy with buffers, unavoidably results in wasting time on the bottleneck."
"Which causes," Fred continues, "a reduction in the overall throughput of the organization. We deliver fewer projects in total than we could."
"So," Mark takes over, "we identified the bottleneck. Very easy, we knew it all along. It is our digital processing department. And then we scheduled their work."
"How?" Brian interrupts.
"The same way we do it in production. There the priority is mainly determined by the due dates of the orders. In our case, by the targeted completion dates of the projects."
Ruth continues, "And from there it was easy. We went back to dealing with each project as a stand-alone. The impact of the other projects was taken into account by the additional information we got from scheduling the digital processing department."
This explanation is too abbreviated for most.
"In every project we have steps done by digital processing," Fred elaborates. "The schedule of the digital processing gave specific start and finish dates for these steps. So, for each project we first did the work as if no other project existed. You know, removing any major contentions. Then we adjusted the project to fit the digital processing dictates."
"Did it change the critical chain?" Ted asks.
"For some projects it did," Fred acknowledges.
"Then you put in the buffers?" Brian checks.
"Of course," Mark answers. "But here comes a major point. All the buffers that we've talked about so far, project buffer, feeding buffers and resource buffers, are all protecting the individual project. Here we have to remember to also protect the bottleneck, the overall performance of our organization."
Ruth continues. "So we had to insert another buffer, the bottleneck-buffer. It's not as big a deal as it sounds. We decided that two weeks is more than enough, for us it is, and every path that goes through digital processing we schedule to start two weeks earlier. It's as simple as that."
The class is quiet. Everyone is trying to digest what they've heard. I don't break the silence.
"We are still not sure if scheduling just the digital processing department is enough," Fred says. "Remember, in production there is the need to sometimes consider not just the bottleneck but another capacity constraint resource, or two."
"How are you going to know?" Charlie inquires.
"We monitor the feeding buffers with hawk eyes, for early warnings," Fred answers. "If a resource contention starts to exhaust one feeding buffer after another, we'll know."
"But only then will we declare it as another resource constraint, not a minute before," Mark is fast to interject. "We are not going to be hysterical and consider every department a constraint just because they claim to be overloaded. We've learned our lesson. Never again are we going back to that nightmare."
We are sitting in a small deli in New York eating breakfast. Me and my Judith. When in Rome act like a