Critical Chain - Eliyahu M. Goldratt [50]
"Mark," I say, "this digital processing department. Are they involved in many projects?"
"All projects. That's our bottleneck. We can't afford to dedicate these people to one project at a time. And in each project, there are many steps that they must be involved in."
"So, if I understand you correctly," I say, "each person is multi-tasking."
"You understood correctly."
"In that environment, being under pressure means that many people are putting pressure on them to work on different things? I suspect that the digital processing people are in no position to really know which tasks are more urgent?"
"How can they," Mark agrees. "I think that their priority system is according to who shouts loudest. And every project has several people who know how to shout."
"So what do they do?"
"The best they can. Jumping from one project to the other, trying to satisfy everybody."
"Typical multi-tasking," I say. "Do you all realize what impact multi-tasking has on lead time?"
They apparently don't.
"Suppose that a person has three steps to do, A, B and C. These steps might belong to different projects or the same project, it doesn't matter. Each step takes ten straight working days. If our person works sequentially, the lead time of each step is ten days. Ten days after he starts B, for example, B is released for somebody else to continue the work. But our person is under pressure and he tries to satisfy everybody. As a result, he works on a step for only five days before he moves to another step. Suppose that the resulting sequence is A, B, C, A, B, C. What is the lead time of each one of the steps?"
I draw the diagrams, so it's easier for them to figure out the answer.
Mark is the one who gives the answer. In astonishment he says, "The lead time of each step doubles. I knew that multitasking was bad, but I didn't imagine to what extent. And we didn't even consider the setup time that is wasted."
"Multi-tasking is probably the biggest killer of lead time," I say. "And we all suffer from it. Call it meetings, call it emergencies, call it other jobs. The impact is the same. Lead time inflates. If you think about it, whenever you give a time estimate you know that the actual time is just a fraction of your estimate, but you intuitively factor in the impact of multi-tasking."
This matches their experience, because they all agree. "Wait a minute," says Mark. "There is something wrong here. In our company, we have to come out with a new product every six months or so. Therefore, if we increase all the safety times, we increase the lead time of all projects. That means that more projects will be going on at the same time."
I don't see his problem. "Correct, but what's your problem?" I ask.
Slowly, he continues. "More projects means multi-tasking. And according to what we said, it means that lead times will lengthen. So what you are telling us is that if we add more safety time it won't help because the lead times will become longer?"
"Self-fulfilling prophesy," Ruth says. "You claim that it will take you longer, it will. And we all know it. My problem is different. How come we allow multi-tasking?"
"Isn't it obvious," I answer. "Without multi-tasking we might run into times where people don't have enough work. Efficiencies will go down."
"Who cares about local efficiencies." It's the first time I've seen Fred get excited. "Isn't the only important thing to guarantee that the projects will be successful."
Mark joins in. "And on the bottleneck, with multi-tasking or without it, we'll have enough work."
More join in. I know where it's coming from. Johnny Fisher is teaching them the course in production. I'd better not step into that mine field. Not without preparation.
I raise my hand to stop the attack. "Hold your horses. Wait a minute." When they quiet down, I continue. "You are raising very interesting ideas. But look at your watches. It will have to wait until next time."
That stops them.
"Let's summarize what we found today." They