Shigeo Shingo Philosophy

A true "zero defects" level of quality is the ultimate level of conformance to specification.
Zero defects (ZD) implies that each and every item built conforms to specification.
Shingo maintains that statistical-based quality control is not conducive to zero defects.
He states that statistical quality control can lower, but not eliminate, defects. Shingo proposes the poka-yoke (mistake-proofing) system to totally eliminate defects.

The mistake-proofing concept is a human- or machine-sensor-based series of 100 percent
source inspections,self-checks, or successive checks to detect abnormalities when or as they occur and to correct them on the current unit of production as well as system wide.

The Shingo Zero Quality Control System consists of four fundamental principles

1-Use source inspection –the application of control functions at the stages where defects originate.
2-Always use 100 percent source inspections (rather than sampling inspections).
3-Minimize the time to carry out corrective action when abnormalities appear.
4-Set up poka-yoke (mistake-proofing) devices, such as sensors and monitors, according to product and process requirements.