Process Capability Index Under Simultaneous Effects of Process Deterioration and Learning Process

Abstract

Process Capability Index (PCI) is often applied to measure the process’s ability of performance within functional specifications under controlled conditions. Thus, PCI can be used to evaluate the manufacturability of the product with given processes; namely, given its process setting and natural variation. However, initial process setting may become false setting and process variance may decrease because process deterioration and learning process respectively. These two effects may occur simultaneously and could be dependent for some case. In these regards, this research presents PCI expression which considers process deterioration and learning effect concurrently. The possible applications for presented PCI expression should not limit only for on-line process evaluation but also for off-line product and process design.