Improved calibration uncertainty assessment technique in coordinate metrology considering thermal influences

Reliable measurement uncertainty is a crucial part of the conformance/nonconformance decision-making process in the field of Quality Control in Manufacturing. The conventional GUM-method cannot be applied to CMM measurements primarily because of lack of an analytical relationship between the input quantities and the measurement. This paper presents calibration uncertainty analysis in commercial CMM-based Coordinate Metrology. For the case study, the hole-plate calibrated by the PTB is used as a workpiece. The paper focuses on thermo-mechanical errors which immediately affect the dimensional accuracy of manufactured parts of high-precision manufacturers. Our findings have highlighted some practical issues related to the importance of maintaining thermal equilibrium before the measurement. The authors have concluded that the thermal influence as an uncertainty contributor of CMM measurement result dominates the overall budgets for this example. The improved calibration uncertainty assessment technique considering thermal influence is described in detail for the use of a wide range of CMM users.