courage to do it.'
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'We did it because it made perfect sense,' I say. 'Reality certainly proved us right. So Ralph, in that case at least, we did affect all the non-constraints. Should we move on?'
Ralph doesn't answer.
'Something's still troubling you?' I inquire.
'Yes,' he says, 'but I can't put my finger on it.'
I wait for him.
Finally Stacey says, 'What's the problem, Ralph? You, Bob, and I generated the work list for the constraints. Then you had the computer generate release dates for all material, based on that list. We definitely changed the way we operated a non-con- straint, that is, if we consider the computer as a non-constraint.'
Ralph laughs nervously.
'Then,' Stacey continues, 'I made my people obey those computer lists. That was a major change in the way they operate -especially when you consider how much pressure the foremen put on them to supply them with work.'
'But you must admit the biggest change was on the shop floor,' Bob contributes. 'It was very difficult for most people to swallow that we really meant they shouldn't work all the time. Don't forget that the fear of layoffs was hanging heavily above us.'
'I guess it's all right,' Ralph gives up.
'What did we do with the method we were using?' Lou asks. 'You know, the green and red tags.'
'Nothing,' Stacey replies. 'Why should we do anything about it?'
'Thank you, Lou,' Ralph says. 'That is exactly what was bothering me.' Turning to Stacey he adds, 'Do you remember the reason for using those tags in the first place? We wanted to establish clear priorities. We wanted each worker to know what is important and must be worked on immediately, and what is less important.'
'That's right,' she says. 'That's exactly why we did it. Oh, I see what you mean. Now-not like in the past when we released stuff just to provide work-now whatever we release to the floor is basically of the same importance. Let me think for a minute.'
We all do.
'Oh shit,' she moans.
'What's the matter?' Bob asks.
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'I just realized the impact that those darn tags have on our operation.'
'Well?' Bob presses her.
'I'm embarrassed,' she says. 'I've been complaining about our problems with the six or seven capacity constraint resources, I raised all the red flags, I've gone as far as to demand that in- coming orders be restricted. And now I see that I've created the problem with my own hands.'
'Fill us in, Stacey,' I request. 'You're way ahead of us.'
'Of course. You see, when do the green and red tags have an impact? Only when a work center has a queue, when the worker has to choose between two different jobs that are waiting; then he always works on the red tag first.'
'So?'
'The largest queues,' Stacey goes on, 'are in front of the bottlenecks, but there the tags are irrelevant. The other place where we have relatively high queues is in front of the capacity constraint resources. These resources supply some parts to the bottlenecks, red-tag parts, but they work on many more green- tag parts, parts that go to assembly not through the bottlenecks. Today they do the red-tag parts first. This naturally delays the arrival of the green parts to assembly. We catch it when it is pretty late, when holes are already evident in the assembly buffer. Then, and only then, we go and change the priorities at those work centers. Basically, we restore the importance of the green parts.'
'So what you're telling us,' Bob cannot contain his surprise, 'is that if you just eliminate the tags, it will be much better?'
'Yes, that's what I'm saying. If we eliminate the tags and we instruct the workers to work according to the sequence in which the parts arrive-first come, first done-the parts will be done in the right sequence, fewer holes will be created in the buffers, my people will not have to track where the material is stuck, and...'
'And the foreman will not have to constantly reshuffle pri- orities.' Bob completes her sentence.
I try to confirm what I heard. 'Stacey, are you positive that your warning about those constraint resources was just a false alarm? Can we safely take more orders?'
'I think so,' she says. 'It explains one of my biggest myster- ies, why there are so few holes in the bottlenecks' buffers, while there are more and more in the assembly buffer. By the way
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fellows, the fact that there are more and more holes indicates that eventually we will run into the problem of insufficient capacity, but not right now. I'll take care of those tags immediately. You won't see them tomorrow.'
'Well, this discussion was very beneficial,' I conclude. 'Let's carry on. When was the second constraint broken?'
'When we started shipping everything much ahead of time,' Bob answers. 'Shipping three weeks earlier is a clear indication that the constraint is no longer in production but in the market. Lack of sufficient orders limited the plant from making more money.'
'Correct,' Lou confirms. 'What do you think: did we do anything different on the non-constraints?'
'Not me,' says Bob.
'Me neither,' echoes Ralph. 'Hey, wait a minute. How come we continue to release material according to the oven and the NCX10 if they are no longer the constraints?'
We look at each other. Really, how come?
'Something even funnier is going on. How come my com- puter shows that these two work centers are still a constraint, that they are constantly loaded to one hundred percent?'
I turn my eyes to Stacey, 'Do you know what's going on?'
'I'm afraid I do,' she admits. 'It's definitely not my day.'
'And all this time I wondered why our finished goods were not depleting at a faster rate,' I say.
'Will one of you tell us what's going on?' Bob says impa- tiently.
'Go ahead, Stacey.'
'Come on fellas, don't look at me like that. After operating for so long with mountains of finished goods, wouldn't anybody do the same?'
'Do what?' Bob is lost. 'Will you please stop talking in rid- dles?'
'We all knew how important it was to make the bottlenecks work all the time.' Stacey starts at last to explain. 'Remember, 'An hour lost on the bottleneck is an hour lost for the entire plant.' So, when I realized that the load on the bottlenecks was dropping, I issued orders for products to be on the shelf, in stock. Stupid, I know now, but at least at the moment our finished goods are balanced to roughly six weeks. No more of that awful
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situation where we hold mountains of some products and not even one single unit of others.'
'That's good,' Lou says. 'It means we can easily deplete it. Alex be careful not to do it too fast, remember the bottom-line ramifications.'
It's Stacey's turn to be puzzled. 'Why shouldn't we get rid of the finished products as fast as possible?' she
