Quartzdyne has implemented dozens of successive checks (a form of informative inspection) across its manufacturing facility. These next-process-checks are implemented in the subsequent process step. It is not an independent inspection like the more traditional, more expensive, and less efficient judgment inspection. The criteria for a successive check is: 100% inspection, judgment about defects are made objectively by individuals that did not perform the work, and when defects occur the information must be immediately fed back to the operator where the defect occurred, at which point the operator takes stock and corrective measures.
The next step in Quartzdyne’s Drive to Zero Defects is source inspection. This inspection method takes place before the defect occurs. It is based on the principle to check the operating conditions that result in defects. Here poka-yoke devices are used to check operations before the processing takes place to ensure all conditions are met and to eliminate the cause of the defect.
“Every defect is preceded by an earlier [event] – the error that was the cause of the defect.”
“Zero defects will only be achieved if you detect the casual error behind the defect at the error stage and then perform feedback and actions so that the error doesn’t turn into a defect. What we absolutely cannot prevent are errors, but we can keep those errors from generating defects.”
Source: Shigeo Shingo Zero Quality Control: Source Inspection and the Poka-yoke System