A study on mutative scale straightness measurement based on uncertainty analysis

Mutative scale measurement is often used to measure the characteristics of mechanical and electrical equipments/components in manufacturing industry. A typical case is the straightness measurement of large-scale rails. Due to the uncertainty of surface error distribution, and difference in the size and the locations of sample points, the evaluated value has a certain degree of uncertainty, which reduces the accuracy of the measurement. Since the decrease of uncertainty is at the expense of higher measurement cost, optimization of measurement cost for an acceptable uncertainty becomes a significant issue. This paper describes the composition of the uncertainty that caused by the measuring process and analyzes the uncertainty caused by sample size insufficiency. On the basis of these arguments, a model has been proposed to calculate the minimum sample size which meets the requirement of measurement uncertainty. Case studies are carried out to demonstrate the application of the derived methodology on sampling strategy. (C) 2012 Elsevier Ltd. All rights reserved.