Productive Systems Process Monitoring through Process Capability Indices

Process capability indices are widely used in process assessments and in evaluation of decisions for a continuous improvement of quality in manufacturing or service process. This paper provides a brief survey of the main capability indices. The paper also focalizes the process capability indices in order to determine their sensitivity to time changes of the production system, showing some models, which emphasize both structural and random variables in the short or middle-long period of time. Then, we address the choice of suitable indices to make structural changes relying on the data process monitoring “ex post” or, alternatively, in real time when location or dispersion shifts from the target values are pointed out. Models are given and a Monte Carlo study has been perfomed.