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A Directional Consistency Analysis Framework for Performance Assessment of CMMs
Jr-Rung Chen a, Jui-Hung Liu a, Sheng-Hsiang Hung b and Ming-Xian Lin c
aDepartment of Intelligent Automation Engineering, National Chin-Yi University of Technology, Taichung, Taiwan, ROC.
bPrecision Mechanical Metrology Research Laboratory, Center for Measurement Standards, Industrial Technology Research Institute, Hsinchu, Taiwan, ROC.
cDepartment of Mechanical and Computer-Aided Engineering, Feng Chia University, Taichung, Taiwan, ROC.
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Abstract:
Leading manufacturers require consistent measurement results between their own coordinate measuring machines (CMMs) and those of their suppliers, but calibration certificates and aggregate Gage R&R provide limited direction-specific diagnostic information. This study proposes a directional consistency analysis framework combining calibrated-reference deviations, leave-one-out peer comparison, directional performance indicators, and cross-feature comparison using the Directional Coverage Ratio (DCR) and Jaccard index. Five CMMs measured a 400 mm gauge block and a 30 mm reference sphere three times in seven directions. For the monitored supplier CMM, the directional error span was 12.23 µm, the exceedance ratio was 42.9%, and the normalized directional span was 2.23. Repeat-based 95% intervals identified Y, ZX+45°, and ZX−45° as the main alarm directions outside the ±2.743 µm screening band. The sphere-form alarm set covered all three gauge-block alarms, resulting in DCR = 1.00 and a Jaccard index of 0.429. A sensitivity analysis over screening bands from ±2.0 to ±3.5 µm showed that the maintenance-priority classification remained unchanged. The framework can therefore serve as a complementary tool for routine CMM monitoring, including health status and supplier measurement consistency assessments in addition to ISO-based verification, formal Gage R&R, and measurement uncertainty evaluation.
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Keywords: coordinate measuring machine, measurement system analysis, CMM monitoring, directional coverage ratio.
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©
2026
CSME , ISSN 0257-9731
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