Balancing production, or the practice of Heijunka*, is from time to time described by some groups as unattainable or imaginary, because it is not fully understood. Yet throughout all the processes in which value is flowing, there are three important causes that do not produce added value. They have been named: Muda (waste), Mura (irregularity), and Muri (overburden). These three phenomena directly affect the system in connection with one another. For example, Mura is at the same time one of the basic causes of Muda. Taking an example from nature on this subject, Taiichi Ohno said the following:
“The slow but consistent tortoise produces less waste and is more desirable than the hare that races ahead and sometimes stops to nap. The Toyota Production System can be realized only when all employees become like the tortoise.”
What is meant here is that production is carried out regularly, steadily, and at the same speed. In this way, the waste produced by production is minimized. In fact, this situation is like a car making its way in congested traffic. Because of stopping and starting, fuel use has increased and the passengers are tense. When the same car travels continuously at a steady speed, however, both fuel consumption falls and the passengers enjoy the changing scenery.
The necessity of balancing production arises from this. What is meant by balancing production is carrying out rhythmic and steady production. Many companies perceive the JIT style of production as irregular production, which is a mistaken approach. As a result, by passing incoming demand on to production as it is, they cause a continually changing speed in production and, consequently, overtime and idle time. Employees, suppliers, and machines swing continually with the changing demand, and costs rise rapidly. They find themselves in difficulty in material management because of the differences that arise between what was planned and what actually happened.
Let us give an example of the effect of balancing and rhythmic production on the stock level. Suppose you work at a company that manufactures white goods. Let the line capacity be 120 per hour. Let a supplier close to you be able to deliver material to you every hour (what a great advantage). If the total number of product varieties in the range is 1200, let us take the variety of material this supplier will deliver to you, thanks to standard use, as 600 varieties. In such a situation, a one-hour stock that you would hold can reach incredible dimensions, and a shortage of space arises. To meet a 120-unit order for one of the low-selling product varieties, two kinds of supply may be possible:
1. This need must be known some time in advance, planning must be done with the supplier, and the material must be delivered to the line before production starts. I am talking about the classic push system. In such a system there is a significant increase in costs and in lead times.
2. Another solution, in keeping with the pull system, is to create a supermarket at the head of the line and to consume the material held there when production starts. This situation brings out another problem. The problem of space. This problem appears even more clearly, especially for products whose average daily sales are low. For example, what kind of supermarket can you create if a one-time order of 120 units arrives for a product whose average daily consumption is 40 units? Keeping 120 units in stock, while creating the ability to produce the order immediately, will carry the stock level and the non-moving stocks to incredible dimensions, whereas the opposite, keeping a stock equal to daily consumption, will make it difficult for you to deliver the order.
In this situation, balanced production emerges as the solution. As a result of balancing, producing 40 units at a time at intervals of one hour will reduce the stock level and ensure that the customer order is delivered within the same day. In this way the supplier will not be pushed to the limit, the sales department will get what it wants, and the stock level and the use of space will fall to a ratio of 1/3.
The example we have given may have seemed complicated to you from many sides, but I am sure that your production is at least as complicated as what is described here. For this reason, I think that such a complicated example will be useful from many points of view.
*In some sources, the English word "levelling" is translated as "leveling." In terms of meaning, however, we were the first to use "balancing" as the correct equivalent, and we consider it correct.