The study of a measurement system precision

Abstract: The use of measurement system Repeatability and Reproducibility (R&R) studies is widespread in industry. Such analyses have become mandatory for many companies who supply the automotive industry and is now an integral part of the QS 9000 automotive industry standard. R&R study allow one to estimate the contribution of variation attributable to the measurement system itself and is used to ensure that a company measurement system is acceptable. If the measurement system R&R study indicate that the recorded measurements may be unreliable, this may impact all subsequent analyses, e.g. control charts, capability analyses etc. It is the aim of this paper to address such issues and to show a measurement system R&R case study that was made in a major automotive company. A measurement system used to measure a bore diameter of a part, having a specification of 18.1 to 18.3 mm was to be evaluated. Ten parts have been selected for measurements by three operators. Each part was measured twice with a dial bore gauge. Because R&R value was between 10 % and 30%, it had required further analysis to find the sources of measurement error. The supposition was that the dial bore gauge was not adequate to measure this bore diameter, so it was replaced by an internal micrometer and another measurement system R&R study was made. The conclusion was that the new measuring system is excellent