Ultra-precision motion systems

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In today's market, many consumer products, such as contact lenses, DVD read/write heads, and the light-enhancing films on almost every laptop screen, are manufactured by a technology called diamond turning.  In this process, a piece of well-shaped diamond tool is installed on a precision lathe, so that metal parts can be machined with optical-quality surfaces.  These parts are then used as molds to reproduce products such as mentioned above, in a very economical and precise way.  However, in conventional diamond-turning processes, the producible surfaces are limited to several types of rotationally symmetric surfaces, due to the inability of the diamond tool to respond to fast-rotating spindles.  As a result, many well-designed and much-demanded optical surfaces, such as those used in micro-lens arrays, cannot be manufactured with satisfying precision. The proposed research is to design a fast tool servo, which can generate very fast motion at 2000 times of gravity acceleration.  When combined with a precision lathe, the fast tool servo moves the diamond cutting tool in and out over 1000 times in each spindle revolution so that non-rotationally symmetric surfaces can be generated.  We will also design and build a precision spindle that is guided, suspended, and driven by a novel compact electromagnetic actuator.  This actuator can automatically adjust forces on the spindle according to the feedback signals from precision spindle position sensors.  Therefore, the spindle motion errors can be reduced to less than 3 nanometers. The breakthrough results of the proposed work will significantly improve the efficiency and accuracy of manufacturing free-form surfaces for products such as digital projector lenses, digital camera lenses, and so on.