Process Capability and Sigma Level
Process Capability: Basic Concepts
Having established the measurement system capability, the next logical step in a Six Sigma project is to determine the initial process capability. In process capability evaluation, we compare and find the ratio of two values: process tolerance and process variation.
Process tolerance is derived from the customer's requirements. Thus, it is sometimes called the ‘voice of customer’ (VOC). Process variation, on the other hand, is a result of our ability to manage and control the process. It is sometimes called the ‘voice of process’ (VOP). Tolerance for the process is usually specified by the designer. This obviously must relate to the customer's requirements. In complex products, ...