Development of an optical measuring method for rotational accuracy of micro-spindle

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Recent rapid progress in the development of the products such as IT equipments, digital cameras and micro-machines need a lot of micro or miniature components. On the other hand, the size of production and assembly systems are much bigger than the components produced by the systems. To this end, a concept of a micro-factory, which consists of tiny machine tools and robots has been proposed. Micromachine tools such as lathes, milling machines and EDM machines have already been developed. On the other hand, new measurement technologies that meet the need of micro-factory must be developed.Measurement method for rotational accuracy of micro-spindles is one of the basic technologies for the progress of micro-factory. For example, cutting of small parts such as thin shafts, requires that the spindle be run at very high speeds in. order to maintain optimal cutting speeds. At present, a micro-spindle with a maximum rotational speed of 200,000rpm has already been demonstrated. However, measure … More ment methods for spindle rotation accuracy of high-speed micro-spindles have not been established. Then, we have tried to develop a new optical measuring method for rotation accuracy of high-speed micro-spindles. In this study, a precise micro ball lens or micro steel ball is attached to the spindle end.The trial apparatus has a semiconductor laser as light source and a quadrant diode as photo sensor. A ball lens, which is attached at the end of a micro-spindle unit, reflects the light from the laser light source and a motion of an axis is analyzed on the reflected light detected by a quadrant photo diode. As the feature of this measuring method, it is mentioned that it is hard to be influenced of an electric noise, and it can respond to high-speed rotation etc. In this study, the relation between optical system parameters and measurement sensitivity is at first made clear, and then the optimal parameters for measurement are determined. Then measurement experiments were carried out for the spindle of a micro-lathe. The measuring results were compared with the results obtained by conventional measuring method using a precision parallel roller and a capacitive type displacement sensor. Less