ABSTRACT
Many organizations use what is called statistical process control (SPC). SPC should be used as a preventive tool to identify patterns before an out-of-control condition happens. Mistake-proofing is a critical component of Lean and provides a mechanism to eliminate the errors so defects won't occur. The only way to prevent defects from escaping to the customer is to inspect 100% of the parts at each operation by machine not human, which leads to the concept of jidoka. Baka yoke means fool-proofing while poka yoke means fail-safing or mistake-proofing. A poka yoke's purpose is to eliminate product defects by preventing, correcting, or drawing attention to errors as they occur. Warning devices alert the operator to a problem but don't prevent the error or the defect. Control devices shut down the operation or don't allow it to proceed until it is corrected. Each category, control, and warning contains the three methods: contact device, fixed-value method, and motion step method.
