Research on a Novel Method for Measuring Volumetric Error of Coordinate Measuring Machine
CMM (Coordinate Measuring Machine) is used as an accurate measuring instrument in manufacturing and design of products. High accurate CMM is required by the development of super-finish, micro-machinery, micro-electronic mechanical systems (MEMS). The precision of CMM is influenced by its volumetric error and dynamic error. The volumetric error is the major component during slowly probing, but the dynamic error is not omitted during fast probing. Compensating the volumetric error is an effective approach to improve the precision of CMM. The volumetric error in the working space of CMM must be measured and the error model must be set up before compensating. In this paper, a novel method to measure 5 volumetric errors of a guide way at the same time by 3-beam laser interferometer is proposed. The error compensating model is validated by experiment. The method can also be used to measure the dynamical error of CMM and CNC machine in real-time. The research can be referred to design the super higher accurate CMM and the accurate CNC machine.
Calibration and Uncertainty of CMM based on Estimation of Geometric Errors.
This paper proposes a calibration method of CMM by estimating of geometric errors. In this calibration, well-known 18 geometric errors, namely parametric errors are adapted. And a rigid body error model using these parameters that indicates the behavior of deviation is described. Calibration can be conducted by estimating of those 18 parametric errors at each dispersed point in measuring volume. In order to estimate 18 parametric errors, independent 18 sets of measurements are necessary. So we designed a measurement strategy, 2D-artifact (ball plate) was arranged in several different positions and measured based on this strategy. As a result, 18 sets of parametric error curves are estimated separately. Considering the demand of uncertainty specification, ball plate uncertainty with traceabillity is reflected to the results of estimated parametric errors. That enables the calibration results to indicate the uncertainty.
Geomagnetic Polarity Epochs: Sierra Nevada Data, 3
Available paleomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85±0.15 million years; Matuyama reversed polarity epoch, 0.85±0.15 to 2.4±0.1 million years; Gauss normal polarity epoch, 2.4±0.1 to 3.35±0.1 million years; Gilbert reversed polarity epoch, 3.35±0.1 million years to (?). A brief interval of normal polarity (the Olduvai event) occurs within the Matuyama reversed epoch at about 1.9 m.y., and a brief interval of reversed polarity (the Mammoth event) occurs within the Gauss normal epoch at about 3.06 m.y. Data for twelve units from eastern California and Nevada, reported here for the first time, are particularly useful in defining the Gauss-Gilbert boundary and for recognizing the Mammoth event.