In 1994 I visited a company that was one of the top in its industry. In its factory were several hundred machines several hundred workers several thousand tools and die castings; and to that factory the market was sending several thousand orders a day. The plant was required to turn out products using just-in-time methods according to type of order quantity and delivery date. Filling all these demands efficiently meant the creation of a production schedule. The number of products and the variations in those products were continuing to increase in one-way fashion. The lots were generally small in size but if there was one larger order for 10000 items there were also orders of only one item per lot and the order flow was mixed. Not only that but there was an increasing number of orders from customers calling for quick delivery times and that was making the production schedule ever more complicated.

At that time the plant was using human brainpower to do its production scheduling. Because the production schedule was being done manually those who were in charge of scheduling were called "human production schedulers." These human production schedulers never got a day off because they would have to come into the plant on Saturday and Sunday to set up the plans for the coming week and then they would be in supervisory positions from Monday to Friday. I even heard that several human production schedulers who got married were never allowed time off so they could go on their honeymoons.

What was required of the human production schedulers is that he or she has experience intuition and courage (KKD in Japanese). The human production scheduler had the experience of working for ten to twenty years in the factory and had the knowledge of several thousand products crammed into his head. The KKD was put to work so that all the products could be shipped from the factory just in time. Decisions about production scheduling had to be taken very quickly. If the decisions were not made immediately the delivery date would creep up quickly and just-in-time delivery would be delayed.

The human production scheduler had to be very fast in judgment and decision and also needed to have experience intuition and courage.