Zero Quality Control

Zero Quality Control is an ideal system that does not produce defective products and doesn’t require frequent inspections, which can waste time and money. Zero Quality Control is the goal of organizations that strive to optimize their processes and are committed to continuous process improvement.

It was created by Shigeo Shigo, who is the inventor of the Single Minute Exchange of Die (Poh-kah Yokay). Shingo was also a major contributor to the Toyota Production System. Shingo passed away in 1990. However, his ideas are still influential for those who use Lean Six Sigma tools.

The use of Poke-yoke and Source Inspection devices can eliminate the need to control statistical quality. This book is not easy to understand, so you need to take your time and read slowly.

This book explains Shingo’s “three crucial aspects of quality control” in detail and includes many examples to show the wide variety of possible applications.

Two main tools of zero quality control

Zero Quality Control is possible only if you implement two Lean Six Sigma-related techniques, Poka-Yoke or source inspection.


Poka-Yoke, also known as error-proofing or mistake-proofing, is the process of identifying where mistakes are most likely and making adjustments to prevent them from happening. It is used in Six Sigma to avoid mistakes and waste. Poka-Yoke gives workers the power to stop production systems when they see a problem, giving everyone the opportunity to fix it.

Source Inspection

This includes looking for defects in the materials, equipment, and fabrications used to make the final product. Identifying defects at the source prevents mistakes from occurring in the manufacturing process or the creation of the final product. This term is sometimes used to describe the practice of inspecting products before they are shipped to a manufacturer.

These two combined allowed Toyota to “virtually remove the need for Statistical Quality Control” (SQC) which had been at the heart of quality control for this country for many years, according to Norman Bodek, publisher of Shingo’s book. He said that “Zero Quality Control is Source Inspection and The Poka-Yoke System.”

Zero Quality Control: The Importance

For any business, the most important determinant of success is the quality of its finished product or service.

Toyota’s consistent quality products are one of the main reasons why it has been able to compete with (initially), larger companies in Europe, and the United States. The Corolla and Camry models were the benchmark for automotive reliability.

Like the ideas of Shingo and Toyota Production System, Zero Quality Control can lower costs, make processes more efficient, and improve quality. Shingo and Toyota proved that this was possible. Shingo believed that business leaders should abandon the notion that zero defects are impossible.

Moving beyond SQC

Shingo stated in his book that he believed that Statistical Quality Control was the pinnacle of quality control for 20 years. The function evolved from simply removing defective products to trying to prevent defects from occurring. He realized that SQC inspections were too costly and time-consuming.

He wrote that he realized that we were only giving feedback and taking action after defects were detected. It occurred to him that there was no inspection system that could prevent these defects from ever happening.

The elements of source inspection, Poka-Yoke, and then he combined them. The results: In 1977, Shingo wrote that zero monthly defects occurred in a 30,000-units-per-month washing machine assembly process at the Shizuoka plant of Matsushita Electric’s washing machine division.

Shingo said that this result “freed me completely from the spell of statistical control quality control.” This idea eventually led to Total Quality Control, which has enjoyed worldwide popularity.

Putting Poka-Yoke Into Action

Shingo stated that PokaYoke has the “very real ability to reduce and eventually eliminate defects.”

  • Make a process flowchart with all details about each step of a process.
  • To determine the most common human error, review each step.
  • Once you have identified potential errors, go through the process to determine the root cause.
  • You can find solutions that reduce or eliminate the chance of an error from happening in the first place. These solutions could include removing the step or replacing it.
  • Teams must find ways to reduce the impact of errors if they cannot eliminate them. This can include changing the source inspection method.