Management Technology Aiming for Zero-Defect Manufacturing: Proactive and Reactive Quality Control

Keisuke Shida (Associate Professor, Department of Industrial and Systems Engineering)

Statistical quality control, proposed by Walter A. Shewhart, is an innovative method for evaluating product quality numerically and stabilizing the manufacturing process. This method has been adopted by factories worldwide and has had a significant impact on Japanese manufacturing. In particular, by incorporating Shewhart's methods, Japanese manufacturing has enhanced the stability of its quality and grown into an industry boasting world-class quality.

A key feature of Shewhart's approach is managing the uncertain factors that affect quality with the power of statistics to reduce product variability. This makes it possible to achieve "stable quality" and provide products that are trusted by consumers.

Now, approximately 100 years later, quality control methods have evolved even further. Conventional statistical quality control was based on the premise that a certain percentage of defects would occur during the manufacturing process, and it was a reactive management approach of "taking action after defects occur" by managing this with statistical techniques. Today, however, there is a demand for an evolution toward proactive quality control, which aims to "not produce defects" in the first place. This new approach seeks to "always produce good products (i.e., be unable to produce defects)" by constantly maintaining various manufacturing conditions in an optimal state. This is becoming achievable due to recent advances in science and technology, which allow for capturing changes in manufacturing conditions in real time and instantly grasping the quality state of products and their manufacturing conditions.

In Japanese manufacturing, the "3-Gen Principle" (San-Gen Shugi) has been emphasized for many years. The 3-Gen Principle is the principle of going to the actual site (genba), observing the actual object (genbutsu), and making decisions based on reality (genjitsu). It is the idea that appropriate measures can only be taken by accurately understanding the problems occurring on-site. Proactive quality control is a technology made possible today precisely because of significant advancements in digital technology, both in software and hardware. By instantly visualizing the quality state of each manufactured product and managing it in conjunction with manufacturing conditions, it serves as a means to prevent quality defects by sequentially determining whether to modify or continue the current manufacturing conditions. It can truly be called the modern 3-Gen Principle.

In this way, management technology in Japanese manufacturing is constantly evolving and will continue to be a crucial key for the Japanese manufacturing industry to lead the world.