Metrological challenges introduced by new tolerancing standards
Ed Morse, Yue Peng, Vijay Srinivasan, Craig M. Shakarji
The recent release of ISO has provided designers with a richer set of specification tools for the size of part features, so that various functional requirements can be captured with greater fidelity . However, these tools also bring new challenges and pitfalls to an inspector using a coordinate metrology system. A sampling strategy that might have worked well in the past could lead to erroneous results that go undetected when used to evaluate these new specifications. In this paper we investigate how measurement strategies for sampled coordinatemetrology systems influence different algorithms for the evaluation of these new specifications. Of particular interest are those specifications where the order statistics of feature cross-sections are required. Here the inspector must decide not only how many points are required for an individual cross-section, but the number and spacing of cross-sectionsmeasured on the feature. The results of these decisions are compared with an analytic estimate of the ‘true value' of the measurand specified using this new standard.