Studies on ceramics micro machining with minute-size diamond quill

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Mechatronic products tend rapidly toward integration and smallization in recent years, so that micro machining has become one of the most important subjects. Especially, main parts are usually made of hard-brittle materials such as ceramics. Because these materials are difficult to process with general physical or chemical method, they are ground mainly using diamond wheels. The objects of this research are to develop a machine for micro grinding by using a minute-size diamond quill and to eam fundamental data of the micro grinding.In order to obtain a standard grinding speed on a quill of which diameter is below 1 nim, the spindle is required of rotational speed more than 100, 000rpm. Other problems in this micro grinding are breakage and elastic deformation of the quill. Based on the above concepts, a grinding machine was newly designed and produced. This machine was equipped with a high frequency spindle of 120, 000rpm in max., and was constructed of areo-static gasbearing, a dynamometer for monitoring the grinding force and a X-Y stage driven by an AC servo motor.Through grinding ceramics on this machine, the following results were obtained.(1)The grinding forces depend upon the wheel speed, the faster spindle speed in the range to 120, 000rpm leading to the lower grinding force.(2)The grinding forces increase simply with increasing workpiece feed speed, so that they can be controlled by operating the feed speed.(3)The grinding forces increase proportionally to grinding length, and those increasing rates decrease with increasing diamond-grit size of quill.(4)Adding vibration to the workpiece vertically to the cut groove reduces the grinding force notably.