INFLUENCE OF MEASUREMENT SYSTEM QUALITY ON THE EVALUATION OF PROCESS CAPABILITY INDICES

Abstract

Among statistical instruments of quality Statistical Process Control (SPC) and Measurement Systems Analysis (MSA) take particular place. The proper quality of measurement data - verification and assurance of this quality are the task of MSA - guarantees an opportunity to carry out a solid SPC analysis supplying information about a process behavior. One of the principal tasks of SPC is estimation of capability of a process i.e. the assessment of process potential as for variability regarding expectations defined by specification limits. Data for analysis of a process capability are the results of measurements made by means of a determined measurement system. The variability of this measurement system must influence the results of capability assessment, however the measurement system adequate to control the process should guarantee that the impact is little enough to be omitted. The subject of the work is the analysis of influence of measurement system variability on evaluation of process capability indices. The mutual relations between process variability and measurement system variability present analytical relationships and experimental research given in the work. The aim of the tests was an assessment of a capability of the process of steel drop forgings' heat treatment relating to a hardness. The methodology demonstrated in the work is valid quality standards compatible (ISO 9000, ISO/TS 16949 etc.).