2011

Improving rotational precision, low-heat generation at high speed and dust/moisture resistance

NTN Corporation (hereafter NTN) has developed an “air spindle for ultra high-precision machine tools” that offers higher rotational precision and lower heat generation at high speeds, plus improved dust and moisture resistance primarily for precision cutting an machining of aspherical lens.

In recent years, there has been dramatic progress in technologies for enhancing performance and reducing size of devices such as portable music players, digital cameras and mobile telephones, thus requiring higher precision for optical components such as built-in thin aspherical lens. Machining such high-precision components requires air spindles with high rotational precision. Taking advantage of the fact that air spindles get their high rotational precision by not having any contact whatsoever between the rotary shaft and housing, NTN has thus far has concentrated on developing air spindles for test equipment and equipment for use in vacuum environments, as well as for the high-precision machining field.

The air spindle for ultra high-precision machine tools we have just developed features an improved air blow structure for the bearing section; it realizes the highest rotational precision in the industry at speeds as high as 20,000min^-1, and at the same time, uses a low heat generation structure that keeps position fluctuation of the work surface to 1 μm or less while machining. Dust and moisture resistance are also improved by use of an air-blow structure in the non-contact seal section and an anti-back-flow structure that doesn't allow grinding fluid sucked up from the vacuum chuck section to get inside; stable operation is realized by the high reliability afforded by the product.

The air spindle has started being delivered to some customers, and will soon be available to processors and manufacturers participating in the growing market for high-precision parts such as optical components.

Features Air spindle unit (with power source and driver)

(1) High rotational precision	NRRO*, actual measurement value 0.005 μm or less (highest in the industry) (1/2 that of the past [at 20,000 min-1])
(2) Superior dimension stability due to low heat generation structure	Max. 1 μm work surface position fluctuation (1/3 that of the past for continuous operation)
(3) Improved dust/moisture resistance	Grinding fluid kept out by anti-back-flow structure and air blow structure of non-contact seal section

* Non-repeatable run-out

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