CarD
^ d^gg
CarE
^ ^
An Assembly Line Based on the Load-Smoothing Production System
Figure 4-4. Load-Smoothing Auto Production
there are many different colors, two-door and four-door models, left and right steering wheels, all mixed together and interspersed while moving through the assembly line.
With this assembly line in operation, it becomes possible to have load smoothing not just for the quantities but also for the types. The work done in this fashion at the final assembly line guarantees that equalization can occur in all preceding processes.
Now take another look at the upper portion of the figure. These exclusive lines could just as well be processes devoted to parts (or to assembly). When all of these lines are equalized, then every line can have adequate work, and work can also become equalized.
PLAN MUST ALSO BE LOAD-SMOOTHING
The load-smoothing system of production has been created to eliminate peaks and valleys in the work load and to avoid excessive production and excessive progression in a particular process. Its aim has been to equalize the work load. However, there is still another contribution that has not been discussed.
That is, through this system it has become increasingly easier to change the production plan. And the workplace has accepted plan changes more cheerfully.
One line produces 100 units every day. A plan change calls for increasing its output to 105 units daily. The workers do the job without thinking of changing their production capacity or system.
However, if suddenly an order requiring 150 units daily is sent to a line that has been producing 100 units, difficulties will arise. Overtime may become necessary, there are not enough workers, and in an extreme case, a new machine may have to be brought in. If this condition persists, the company may be forced to hire more personnel or to utilize subcontractors. Its ability to respond to change becomes rather limited.
The key to solving this problem is the production plan. But almost every factory and company seem to have poorly managed production plans.
During the month of January, the line in question is produc- ing at the rate of 100 units. In February, it is likely that 120 units must be produced because orders are coming in. This fact is usually known by January 10. However, a common practice is to draft a plan for presentation at monthly production meetings. The workplace receives a written plan after January 20. In an extreme case, a 20 percent increase in February and an additional 20-percent increase in March are the facts already known, but management Insists on waiting until the very last minute to hold its monthly Wanning meetings. Management does not think to change the bfcviously set dates for these conferences.
If management continues to follow this practice, there is no iftiv the workplace can respond to change. It becomes a victim of m «>wn silly rules, resulting in a curious inability to move ahead.
Therefore, when making a change in the production plan, Biild in the necessary changes gradually. Change the plan when an hi re.ise or decrease in the amount of production is known. In this Bftiuilar example, it was known by January 10 that the demand would be higher by 20 percent in February. The management Bottld have asked the workplace on January 11 to increase its Kily output immediately by five to eight units. By taking this [ll'iulinil approach, the workplace could have handled it well.
к
EASIER TO ESTABLISH STANDARD OPERATIONS
In any work, it is important to establish standards. But unless the work itself is somewhat stabilized, standardization becomes rather difficult. In some instances, standards may be established, but they are worthless for practical purposes.
"The first step toward improvement is standardization." Where there is no standard, there can be no improvement.
When we engage in the load-smoothing system of production, we can establish standard operations throughout the entire process, covering all processes and lines. This is one of the main goals of load-smoothing production.
At Toyota, we manufacture through load smoothing, we figure out the cycle time and we create standard operations. We then promote our improvement activities. These are the basic steps we have consistently followed.
In a nutshell, the Toyota kanban system removes the signboards proportionate to the quantity used, and goes to the preceding process to withdraw exactly the same quantity. The preceding process manufactures the exact quantity just withdrawn. The kanban system is a system that keeps on turning this cycle.
Frequently we hear this comment: "That's a very snappy way of doing things. Even for those parts bought from outside suppliers, all one has to do is send a piece of paper and the parts arrive." But the success of the kanban system is dependent on the thoroughgoing conformance to the load-smoothing system of production at each of the final processes.
Assuming that the final process has not been converted to the load-smoothing system of production, but insists on using the kanban to receive parts — for a party receiving this demand, it is a bolt from the blue.
The workplace cannot use the kanban to order 50 boxes today, none tomorrow and 150 boxes the day after tomorrow. If the preceding process or supplier is treated in this manner, utter confusion will result.
Under the kanban system, the subsequent process withdraws parts and material from the preceding process every day, with consistency — in the same manner, at the same interval and in about the same amount. It is only in this way that the system can succeed.
obstruction called exchange of die
A bottleneck is often created in the load-smoothing system of production by the exchange of die.
Normally the exchange of die is considered a time-consuming process. Why?
The preponderant reason is that where there is no desire to do die exchange quickly, it becomes a self-fulfilling prophecy.
In fact, some workplaces do not worry if the exchange of die takes eight hours. That, of course, is an extreme case, but no one thinks much about the die exchange that takes one hour. In some workplaces, equipment procurement is often premised on iliese uncontrolled die-exchange procedures.
In places like these, the load-smoothing system of production ||nd the exchange of die become irreconcilable opposites.
One of the characteristics of the Toyota system is to make the р/с of a lot in the workplace as small as possible. If the time spent ■>r exchanging die is greater, the lot is likely to remain larger, when the lot is larger, it is often assumed that through it the time pt through the exchange of die can be recovered. But this can ■til to the waste arising from overproduction.
Our aim is to please our customers by producing only those ВГ» that they order. If we complain about the frequency of die KChange, we are in effect saying to our customers: "Why don't Hi order the same style and same type of cars?" That is not the Itav to do business.
The only alternative left for us is to shorten the time spent for ■ exchange of die.
вера ration and cleanup are the keys
F It is not that difficult to shorten the time needed for the liangc of die.
The point is to make an advance preparation of those molds, jigs and tools that can be assembled ahead of time, and to clean and place in their storage places those molds, jigs and tools that are removed only after the machine starts moving again. This is called thoroughness in the outside exchange of die.13
We must concentrate on, and try to improve, those operations that cannot be performed without stopping the machine. With this alone, the time needed can be significantly reduced. This is called thoroughness in the inside exchange of die?
If tools are to be used, be sure that all those needed are kept by the side of the machine and in the order they are to be used. Do not overlook the proper arrangement of materials. Focusing their attention of the die exchange, workers can perform it quickly and expertly. But this can come to nothing if they do not have the necessary materials. Things like this happen frequently.
Preparations and arrangements can be made through improvement in the work process. In other words, these can be accomplished through the workers' own ingenuity. The procedure must be standardized and written down in a standards manual with which workers can continue training and retraining to do the exchange of die. Time reduction becomes possible.
This training is very similar to fire drills practiced by many companies. In a fire drill, it is not unreasonable to expect that all the water hoses are readied within two minutes. Everyone observes the correct procedure. The fire fighters also know how to divide up their work without any waste or delay.
In exchanging die for large equipment, Toyota retains the services of a special unit organized by specialists in die exchange, j Seven or eight years ago, it took three hours to exchange die in am eight hundred-ton press. Today it takes only three minutes.
Chapters 5, б, 7, 8, and 9 are selections from Today and Tomorrow^ Henry Ford (Cambridge: Productivity Press, Reprint edition 1988)
ШЩ т i 1 ж Ш ■ я^Ш^^ШШ1 щ щ щ ж Щ > I I Щ
ш ЯиЯН
Ми
11 ill Мшт-. IBS
яряртянр||14| Ш/рШтТ. н''.' ч
ЩИдЮ ЙНИИДИЮ
A ЙЧн 'AtiWfi1'