Lean Production. John Black
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than being worked and then transported to the next stage, or to storage, in large batches. This arrangement produces lower work-in-process inventories and small lot sizes, which in turn helps reduce space requirements and cycle time for improved continuous-flow processing. (See Figure 3.7.)
An important aspect of just-in-time operations, so important that it is part of the foundation of the Global Production System house, is leveled production. Leveled production smooths out the peaks in product volume and mix, and it allows the pattern of production to follow the pattern of sales. At Toyota, for instance, various body types move along the same assembly line at the same time, and the production of different body types is staggered evenly over the course of the day. This strategy makes the most efficient use of people and equipment, steadying the workload in all processes. Leveled production also prevents a disproportionate burden from being imposed on one team or type of machinery while others are idle or lightly loaded.
Figure 3.7: Equipment is arranged to aid flow and reduce work in process
Cycle or takt time
Toyota uses the term takt to describe the pace of sales in the marketplace. Takt is a German word for meter. Takt is quantified in Toyota plants as the quotient of daily working hours divided by the number of vehicle orders to be fulfilled each day: takt is expressed in hours, minutes, and/or seconds per product, per day. According to this quotient, takt times are also worked out for each component used to produce the vehicles. Takt time equals the total available production time divided by the number of units required to meet customer demand.
Once a takt time is determined, work is allocated to maintain a steady, optimum workload for each operator and each machine. Relying on multi-skilled workers further improves continuous flow and gives Toyota the flexibility to allocate work precisely according to takt times, but without overloading individual workers.
Standardized work is another method for successfully balancing takt time (production requirements) with people’s work time. That’s why a Global Production System strives for standardized work. Standardized work keeps productivity, quality, and safety at high levels. It also provides a consistent framework for performing work to designated takt times and identifying opportunities for improving work procedures. Once standard work is in place, takt time becomes a management tool for jidoka.
Jidoka and kaizen
Jidoka is another important principle at Toyota — one so important that it forms the second pillar working with just-in-time production to hold up the roof. Jidoka is the principle of stopping work immediately whenever a problem or abnormality occurs. Toyota production equipment is designed to stop automatically if an error is detected, and workers are expected to halt the line when defects are suspected. Defects are thus prevented from traveling any further into the system. Jidoka also helps identify the causes of problems by halting the line as soon as the problem is recognized.
In essence, jidoka means assuring the quality of everything by confirming the outcome of each process step before going on to the next. Jidoka does not have to be a feature of machines. Human workers can also detect abnormalities, particularly if they have a visual standard to watch for, and stop the process when a problem is detected. Certainly it is up to the workers to fix or correct the immediate problem and then install a countermeasure so that it cannot occur again.
The advantage of automating jidoka, however, is that it separates human work from machine work and frees workers for more value-added activities. Instead of watching machines run, employees can solve problems and find new ways to improve productivity and eliminate waste. This continuous improvement process is known as kaizen. Kaizen improvements in standardized work help to maximize productivity by encouraging individuals to help design, manage, and improve their own jobs.
When all the pieces of just-in-time production, jidoka, and waste reduction are working together, the Global Production System drives a cycle of continuous improvement. (See Figure 3.8.) Here’s how the cycle works:
•Just-in-time production reveals abnormalities by making inconsistent results immediately obvious, because bloated inventories no longer exist to conceal problems.
•Through jidoka, workers respond to the abnormalities by stopping and fixing problems, then changing the process or installing countermeasures that improve the system and the resulting quality.
•The corrections or improvements eliminate waste and cost and establish the new standard of consistency for subsequent just-intime operations.
Figure 3.8: GPS house with cycle of continuous improvement
This Global Production System will keep you in business forever. It represents revolutionary change to many industries and organizations, just as the Toyota Production System brought revolutionary changes to automobile manufacturing. Today, Toyota dominates the automobile market and is a model for manufacturing excellence. And Ford Motor Company, once the mentor, nearly failed before following the path of its protégé. The student became the teacher, and the teacher the student. In the school of hard knocks, Ford people have learned a lot in recent decades and implemented better production techniques, because clearly their survival depends on it. Many companies are trying to follow Toyota’s lead, and they’re learning that a world-class operation is highly efficient but quite difficult to achieve.
Spreading the Toyota message
After Ohno’s time, his legacy of controlled production improvement rested in the hands of two protégés, Yoshiki Iwata and Chihiro Nakao. Both men eventually retired from Toyota to form an international consulting firm, Shingijutsu Ltd. For many years, they worked together as leading emissaries of what the Japanese have learned about producing efficiently and with the highest possible quality. Their pioneering endeavors in the realms of better manufacturing methods and continuous quality improvement are unquestionably world class. Although Iwata is no longer with us, Nakao continues to help others implement lean production techniques through his company, Shingijutsu USA, and Iwata’s daughter, Kumi Iwata Otake, carries on her father’s work through Shingijutsu Global Consulting. The closer that a company can get to implementing Shingijutsu’s advice, the closer it will be to world-class performance.
DEFECTS, MISTAKES, AND INSPECTIONS
“We are part of a culture that believes defects are inevitable, and we use this belief to tolerate their perpetuation.”
— Dr. Bob Caplan, medical director of quality, Virginia Mason Medical Center
Jidoka, one pillar of the Global Production System house, is the principle of stopping work immediately whenever a problem or abnormality occurs. This concept was formalized by Shigeo Shingo, a Japanese industrial engineer for whom the Shingo Prize was named. He is sometimes referred to as the only consultant Toyota ever hired. Considered the dean of productivity, Shingo advised Toyota for over 50 years, wrote more than 20 books, and worked with the leaders of Honda, Kanzai, Matsushita, Sony, Sharp, and Nippon Steel, among others.
One of Shingo’s manufacturing interests was inspection theory. The concept of zero defects — and jidoka as a means to achieve that performance — flows directly from his work in that area.
Many organizations turn first to inspection as a strategy for ensuring zero-defect production. Regulatory structures and governmental agencies often reinforce or even mandate this strategy. But the strategy as it is typically implemented is faulty.
A much more effective strategy for ensuring zero defects is to start by distinguishing between mistakes and defects. Mistakes are inevitable but reversible. Defects, however, are mistakes that were