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Available from: Andrew Peter Longstaff, Sep 10, 2014
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    ABSTRACT: Kinematic errors due to geometric inaccuracies in five-axis machining centers cause deviations in tool positions and orientation from commanded values, which consequently affect geometric accuracy of the machined surface. As is well known in the machine tool industry, machining of a cone frustum as specified in NAS979 standard is a widely accepted final performance test for five-axis machining centers. A critical issue with this machining test is, however, that the influence of the machine's error sources on the geometric accuracy of the machined cone frustum is not fully understood by machine tool builders and thus it is difficult to find causes of machining errors. To address this issue, this paper presents a simulator of machining geometric errors in five-axis machining by considering the effect of kinematic errors on the three-dimensional interference of the tool and the workpiece. Kinematic errors of a five-axis machining center with tilting rotary table type are first identified by a DBB method. Using an error model of the machining center with identified kinematic errors and considering location and geometry of the workpiece, machining geometric error with respect to the nominal geometry of the workpiece is predicted and evaluated. In an aim to improve geometric accuracy of the machined surface, an error compensation for tool position and orientation is also presented. Finally, as an example, the machining of a cone frustum by using a straight end mill, as described in the standard NAS979, is considered in case studies to experimentally verify the prediction and the compensation of machining geometric errors in five-axis machining.
    Precision Engineering 04/2009; 33(2-33):194-201. DOI:10.1016/j.precisioneng.2008.06.001 · 1.52 Impact Factor
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    ABSTRACT: Machine tool performance testing, as defined by ISO 230 and ANSI B5.54, has been successfully used to maintain and improve the accuracy and repeatability of production-level machine tools. In this study, a controlled series of experiments have been used to test the efficacy of these performance tests in the prediction of part form errors. Results are shown for flatness, squareness, position, and profile tolerances. The experimental results suggest that standard machine tool performance tests can also be used to predict the “best-case” tolerances that can be achieved for particular part features.
    CIRP Annals - Manufacturing Technology 01/1997; 46(1-46):471-474. DOI:10.1016/S0007-8506(07)60868-3 · 2.54 Impact Factor
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    ABSTRACT: The introduction of B5.54 and ISO230-6 machine tool performance measurement standards is increasing the popularity of laser interferometer diagonal, step diagonal and vector methods for the evaluation and compensation of machine tool errors. This is due to the potential reduction in calibration time, these methods can provide over the more conventional laser interferometer-based linear, angle and straightness measurements taken along lines parallel to the machine’s X, Y and Z axes.This paper highlights limitations in the results produced by diagonal-based measurements and by the more recently introduced vector or step diagonal methods. The purpose of this paper is to alert potential users of these methods to their limitations so they can make informed decisions as to whether the reduction in calibration time they can provide outweighs the loss of accuracy and detail in the results. It also indicates some of the dangers in using laser diagonal data alone for the compensation of machine tool errors.
    Precision Engineering 10/2003; 27(4):401-406. DOI:10.1016/S0141-6359(03)00041-2 · 1.52 Impact Factor