Build in Quality

One of the values of operational excellence within the TPS model is to build in quality rather than inspect in quality.  This means that each process should be developed in such a way that it guarantees quality to the next process. 

Because 100% quality is not always possible, mistake-proofing systems or devices known as pokayoke are used to prevent the errors from happening. 

When errors cannot be prevented, or if there is a breakdown in the prevention system, the process must detect the error and stop, alerting people to the problem.  In this way the poor quality is not passed downstream.  This idea is called jidoka and can be applied to equipment through the use of sensors or to manual processes by empowering people to stop the line when a defect is detected.

Poor quality: don't take it, don't make it, and don't pass it on.

Building in quality does not mean "zero inspection" but rather that each person and each process must inspect their work, instead of at the very end.  The awareness of quality and the empowerment to stop the process if poor quality is detected makes the concept of "build in quality" a powerful source of improvement ideas.