Kengo Fujimaki

Error correction method in radial runout measurements based on laser autocollimation

Radial runout measurement on a spindle, based on laser autocollimation, is susceptible to reflection surface irregularities because an irregularity occurring in the reflected laser beam rotates with the spin of the reflection target. This, study proposes an error correction method for the influences of reflection surface irregularities by applying the three-point method, which separates the radial runout of the spindle and the out-of-roundness of the reference cylinder attached to the spindle by using three displacement sensors. The principle of the proposed method is described, and its validity is confirmed in a computer simulation and experiment.

Development of an Optical Measuring Device for Rotation Accuracy of Micro-Spindle —Application to Measurements of a High-Speed Spindle—

It is very difficult to measure the rotation accuracy of miniaturized spindles running at high-speed with a common measuring method which uses capacitive displacement sensors. Therefore the authors have proposed a new optical measuring method using a small reflection sphere as a measurement target. In this paper, the basic principle of the optical measuring method, the configuration of the measuring device and some of the measurement data are shown.

Effects of sensor noise in digital signal processing of the three-point method

The three-point method is a technique that uses three displacement sensors to separate the out of roundness of a reference sphere or cylinder as well as the spindle run-out. This method has high potential for ultra-high-precision measurements. However, applications of the three-point method have been impeded because the setting angles of the sensors have not been clearly established. In this paper, the effects of uncorrelated noise in sensor outputs on the calculation results of the roundness are analyzed by applying the process of the three-point method as a digital filter. Then, the optimum sensor angles, which minimize the effects of the noise, are computed where there is uncorrelated white or pink noise in sensor outputs. In addition, the effects of correlated noise in sensor outputs are analyzed.

Measurement and Analysis of Radial Error Motion of a Miniature Ultra-High-Speed Spindle

The optical measuring device developed in this study is based on laser autocollimation and can measure the radial error motions of a miniature ultra-high-speed spindle having a maximum rotational speed of 200 krpm. The maximum response frequency of this optical measuring device is over 500 kHz, while the frequency of the radial error motion at 200 krpm is 3.33 kHz for 1 undulation per revolution (upr), and 333 kHz for 100 upr. In addition, the optical measuring device is capable of a highly detailed analysis of the radial error motion of a miniature ultra-high-speed spindle since it has a high signal-to-noise ratio due to little susceptibility to electrical noises.