Zero Quality Control refers to the ideal process – one that produces zero defects and does not require frequent inspections. Achieving Zero Quality Control requires use of two Lean Six Sigma tools: Poka-Yoke and source inspection.
Poka-Yoke
The Poka-Yoke refers to a mistake-proofing approach to managing processes. Used in both Lean and Six Sigma, Poka-Yoke identifies steps in a process where errors are most likely to occur, giving managers or project teams time to make changes to the process before the errors happen. Japanese engineer Shigeo Shingo invented Poka-Yoke in the 1960s, where it became (and remains) key to the famously efficient and effective Toyota Production System.
Source Inspection
Source inspection is a critical strategy to achieve Zero Quality Control. Source inspection refers to the concept of inspecting materials, equipment and fabrication from suppliers that are used in creating a final product. By looking for defects at the source, it prevents mistakes and errors in creation of final products. This also can incorporate the idea of Jidoka, which allows employees to stop a process when they see an issue arise with defective equipment or materials.
Development of Zero Quality Control
Shingo literally wrote the book on Zero Quality Control – called “Zero Quality Control: Source Inspection and the Poka-Yoke System.” By putting Poka-Yoke to work, Shingo wrote that organizations have “the very real capacity to reduce, and eventually to eliminate, defects.” He cited the zero defects in a washing machine plant in Japan in 1977 as an example of how effective Zero Quality Control can become. At the time, the Shizuoka washing machine assembly plant of Matsushita Electric produced 30,000 units per month.
Shingo invented Zero Quality Control after years of working in manufacturing and seeing inspections done primarily on the backend of operations. Inspectors would simply throw out defective products, but time, labor and materials costs had already gone into making the defective product. Shingo wanted a method that allowed businesses to spot problems before they result in defective, useless products. Another advantage of Zero Quality Control is that it saves the cost of frequent inspections on the backend of the process.
