AN ANALYTICAL ASSESSMENT OF MEASUREMENT UNCERTAINTY IN PRECISION INSPECTION AND MACHINE CALIBRATION

Dimensional inspection is commonly used to scrutinize the quality of m anufactured products against the established standards and specificati ons. Meanwhile, dimensional measurement of an artifact is also commonl y used as one of the methods for machine-performance calibration. Howe ver, the quality and reliability of many inspection and measurement pr ocesses are often contaminated by various uncertainties. Two prominent sources for measurement uncertainties are: (a) the imperfection of a measuring device, and (b) the dimensional deviation and geometric char acteristics of a measured feature. Usually, the effects of both types of uncertainty are compounded by one another. To ensure the quality an d reliability of any inspection process, measurement uncertainty needs to be addressed for all data acquisition activities. A method is also needed to identify and decouple the effect of compounded uncertaintie s. If this can be done, then the data collected can be properly adjust ed and a more meaningful analysis result can be drawn. In this paper, the issues of uncertainty identification for machine calibration and d imension measurement using artifacts with various geometric features a re discussed. Analytical models are derived first to identify and then decouple the compounded effect of both types of uncertainties. Finall y, case studies are used to illustrate the procedures for both identif ying and decoupling the compounded effect of the measurement uncertain ties. (C) 1997 Elsevier Science Ltd.