Measurement of five-degrees-of-freedom spindle error motion using multi probe error separation

Herein, a precision measurement method is proposed to evaluate the radial, axial, and tilt error motions of rotating devices such as precision spindles. To improve the accuracy of the estimated multiple-degree-of-freedom error motion components, form error signals in the runout signals are separated and precompensated for before the calculation of the five-degrees-of-freedom error motion components. Fourier model-based multi probe error separation (MPES) techniques, which can prevent the occurrence of harmonic distortions, are applied to separate the form error signals. A three-probe method is applied to layers on the side surface of the cylindrical artifact, and a modified two-probe method is developed and applied to the upper surface. The radial, tilt, and axial error motions are calculated using the runout signals that do not contain the separated form error signals. The measurement system uses eight capacitive probes to detect the runout signals of the cylindrical artifact mounted at the center of the rotating device. To compare the proposed method with the five-probe-based conventional measuring method, an evaluation test simulation is conducted repeatedly five times. Results indicate that the proposed MPES method calculated the uncertainty using the deviation between the computed results from the existing and novel methods; additionally, the input signal in terms of the radial, tilt (layers 1 and 2), and axial error motions are [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text], respectively. It is confirmed that the undesirable effects of the form error signals are successfully removed and that the accuracies of the measured spindle error motion components improve.

Effect of Measuring Instrument Eccentricity and Tilt Error on Circularity Form Error

From power stations to power tools, from the smallest watch to the largest car, all contain round components. In precision machining of cylindrical parts, the measurement and evaluation of roundness (also called circularity in ASME Geometric Dimensioning & Tolerancing Y14.5) and cylindricity are indispensable components to quantify form tolerance. Of all the methods of measuring these form errors, the most precise is the one with accurate spindle/turntable type measuring instrument. On the instrument, the component is rotated on a highly accurate spindle which provides an imaginary circular datum. The workpiece axis is aligned with the axis of the spindle by means of a centering and tilt adjustment leveling table. In this article, the authors have investigated the dependence of circularity form error on instrument’s centering error (also known as eccentricity) and tilt error. It would be intriguing to map this nonlinear relationship within its effective boundaries and to investigate the limits beyond which the measurement costs and time remain no more efficient. In this study, a test part with different circular and cylindrical features were studied with varying levels of predetermined instrument eccentricity and tilt errors. Additionally, this article explores the significance of incorporating these parameters into undergraduate and graduate engineering curricula, and be taught as an improved toolkit to the aspiring engineers, process engineers and quality control professionals.

In Situ Measurement of Spindle Radial and Tilt Error Motions by Complementary Multi-probe Method

This paper presents a complementary multi-probe method for measurement of radial and tilt error motions of a spindle. Neither indexing of artefact nor rotating of spindle housing is required and thus make it suitable for in situ evaluation of spindle performance effectively. In order to minimize the harmonic suppression problems commonly encountered in the multi-probe measurement approach, three sets of probe angle combinations were optimized and the harmonics of the three measurements were extracted and composed to reveal the true artefact errors in a complementary way. The exact probe angles were identified by the correlation function of the probe signals after the sensors are mounted onto the fixture and the requirement of high-precision fixtures was alleviated. The evaluation of measurement results showed that the erroneous harmonics were greatly reduced by 70%. Using this method, the radial error motions of the precision air bearing spindle were measured at seven axial positions and then the synchronized tilts error motions were calculated. This demonstrated an effective approach for measuring four degree-of-freedom error motions in one setup with a small number of displacement sensor probes.

Dependence of Measuring Instrument Eccentricity and Tilt Error on the Four Mathematical Methods of Circularity Form Errors

In precision machining of cylindrical parts, the measurement and evaluation of circularity is an indispensable component to quantify form tolerance. Of all the methods of measuring these form errors, the most precise is the one with accurate spindle/turntable type measuring instrument. On the instrument, the component is rotated on a highly accurate spindle which provides an imaginary circular datum. The workpiece axis is aligned with the axis of the spindle by means of a centering and tilt adjustment leveling table. Based on reference circles, this paper focuses on the four modeling methods of roundness, namely, (1) Least Squares Circle (LSC), (2) Maximum Inscribed Circle (MIC), (3) Minimum Circumscribed Circle (MCC) and (4) Minimum Zone or Minimum Radial Separation (MRS) Circles. These methods have been explained in author’s previous article in the context of their implications on design applications, advantages and disadvantages. In this article, the authors have investigated the dependence of these mathematical methods based circularity form error on instrument’s centering error (also known as eccentricity) and tilt error. Some intriguing results were observed for the highly nonlinear relationship of machine’s centering/tilt error with circularity results outside its useful linear region (50–600 μin for this specific machine used in this investigation). Further, the linear and nonlinear relationship was mapped within the effective boundaries of eccentricity settings to investigate the best and worst methods of circularity measurements that are susceptible to instrument errors. Very high and low machine eccentricity settings in its nonlinear regions were not accurately compensated by the machine in circularity results processing. In this study, a master part with different circular and cylindrical features was studied with varying levels of preset instrument eccentricity and tilt errors. Off the four methods, MRS reported the least circularity results. The other three methods didn’t provide any predictable trend. Circularity results were observed to differ up to 35% within these four methods. However, in this preliminary investigation, this maximum difference doesn’t appear to follow any predictable trend with varying machine eccentricities. This article also reinforces the significance of these parameters, and the way they should be understood and be incorporated into undergraduate and graduate engineering curriculum, and be taught as an improved toolkit to the aspiring engineers.