Coordinate-Measuring Machine Capability

摘要

Three-axis measuring machines have complex geometric and displacement errors. Many machine users are unaware of these systematic errors and think only in terms of the three-scale or displacement errors which may be significantly smaller in magnitude than the geometric errors. A method of estimating the volumetric uncertainty of five coordinate measuring machines (CMMs) was established and the measurement uncertainty is reported for a 20 by 18 by 12 in. work zone. The Latin-Square Three-Dimensional Ball Plate (LS3DBP) and the Space Master Ball Plate (SMBP) were the volumetric standards selected for the evaluation. Data from each ball plate were transformed into new coordinates and compared to previous calibration or reference data. The deviation between measured and referenced values was recorded. These data were used to determine a quantitative estimate of the CMMs measurement capability in X, Y, and Z space by using the Analysis of Variance Technique (AOV). Similar results were obtained from each standard. The precision and uncertainty for each machine was determined and the results ranged from 120 to 150 mu in precision and from 270 to 350 mu in uncertainty. An evaluation of a larger work volume on each of the five machines is desired to support existing measurement requirements. (ERA citation 09:001130)