World Congress Fundamental and Applied Metrology September 6 − 11 , 2009 , Lisbon , Portugal ADVANCED CALIBRATION METHOD FOR PITCH ARTIFACT
Abstract − The pitch measuring accuracy for gear measuring instruments (GMIs) is evaluated by measuring a calibrated artifact. We proposed a novel artifact which called multiball artifact (MBA). The MBA is composed of the pitch balls assumed to gear teeth and the reference axis assumed to a center axis of gear. The MBA can be calibrated more accurate than a conventional pitch artifact. When the MBA is calibrated, it is important to eliminate an error of measuring instrument; therefore we calibrate the MBA adapting the multiple-orientation technique. In the multipleorientation technique, the MBA is set up in difference orientations around the reference axis and the measurement error is eliminates by averaging the measurement value for all orientations. There are, however, Fourier components of the measurement error that can not be eliminated depending on the total number of orientations. In this paper, we propose the advanced calibration method; the error separation method for the multiple-orientation technique is improved and the total number of orientations can be reduced. The superiority of the proposed method is clarified from the calibration results using the MBA.
Design and Error Analysis of Multiball Artifact Composed of Simple Features to Evaluate Pitch Measurement Accuracy
The strength and vibration/noise of gears are influenced by the pitch deviation of micrometer order and therefore, advanced quality control is needed in gear manufacturing processes using measuring instruments. The accuracy of the pitch measuring instrument is verified using a master gear or artifact, but their accuracy is not sufficiently high. An artifact with higher accuracy for the evaluation and calibration of the pitch measurement is necessary in order to respond to the requirement of gear accuracy. In this research, the multiball artifact, a novel high-precision pitch artifact, is proposed for use in the evaluation of pitch measuring instruments. The multiball artifact is composed of balls, a cylinder, and a plane, where the center cylinder or center ball is surrounded by the balls on the plane. The positions of those elements are decided automatically by the contact among those elements. Balls, cylinders, and planes can be manufactured with accuracy on the order of several tens of nanometers. Therefore, this artifact can realize high accuracy. In addition, this artifact does not need advanced techniques in manufacturing and assembly. This leads to the reduction in manufacturing cost. In this report, the concept and structure of the multiball artifact are proposed, and theoretical analysis on the measurement of the artifact is carried out. Feasible angular pitch is analyzed theoretically. For a cylinder-centered artifact, it is easy to realize the target angular pitch by adjusting the cylinder diameter. Ball-centered types suffer from the limitation of the variation in ball diameter if standard balls are used, but an angular pitch close to the target pitch is possible through the selection of an appropriate combination of balls. The effects of the dimensional deviation of the diameter of the center cylinder, the inclination of the center cylinder, the dimensional deviation of the surrounding ball diameters, the sphericity of balls, and the flatness of the base plane are analyzed. Deviations in the cylinder have a comparatively large effect on angular pitch. On the other hand, the effect of the deviation of the ball or base plane is smaller. The feasible angular pitch is clarified, and it is verified that the concept and structure of the multiball artifact are effective. The effects of deviations in the form and dimension of the composing elements are analyzed, and it is clarified that the accuracy of the cylinder is important. DOI: 10.1115/1.3087535
Tooth Form Evaluation Using Ball Artifact Development of a Measuring Instrument of a Ball Center Distance Traceable to National Standard of Length
AIST (National Institute of Advanced Industrial Science and Technology) has proposed a new calibration method of gear measuring instrument using a ball artifact consisting of two master balls and an optical flat base (DBA). We measure a circular arc instead of involute tooth form. Difference of the distance between the arc of the master ball and involute curve can be calculated theoretically. For the calculation, center distance between two balls is required and the value of measurement uncertainty is less than 0.1 'm and also should be traceable to national standard of length. This paper reports on a new method and an originally developed instrument to measure the center distance between two balls using laser interferometer. The expanded uncertainty in measurement of a center distance of 44 mm was 21 nm.