Process Capability Analysis Plot for a Product with Bilateral Specifications

a multi-process performance analysis plot based on process capability indices has been developed to analyse the manufacturing performance for multiple processes, which conveys critical information regarding the departure of the process mean from the target value and process variability, and provides a guideline for capability improvement. existing performance analysis plots usually assume normal distributions and symmetric tolerances. in this paper, we present a graphical method to evaluate the process capability of a product composed of independent multiple processes with nominal-the-best specifications and symmetric or asymmetric tolerances. the proposed plot aims to get information about the location and spread of the studied characteristics which can follow any continuous distribution. an example showing the effect of processes with asymmetric tolerances on the capability of the product is considered.