文献翻译-夹头.docVIP

外文文献及其翻译 COLLECT CHUCK 1.Introduction To improve productivity in micro/meso-scale components,researchers have focused on developing miniaturized manufacturing instruments,such as micro-machine tools.These miniaturized systems are expected to save energy and be easily reconfigurable.The first step in micro-manufacturing instruments is miniaturizing the corresponding subsystems.In particular,micro-machine tools for material-removal processes have,as a key subsystem,a micro-spindle unit that must achieve high rotational speeds while maintaining good rotational accuracy for micro-feature machining. In developing micro-spindle units,a critical problem is miniaturization of the tool-clamping part that holds the tool in the spindle.Approaches for scaling down conventional tool clamps,such as the collet-chuck,hydraulic chuck,and shrink-fit methods,may be limited by their inherently complicated structural and operational mechanisms.In collet-chucks,a tapered collet and collet-pulling device,such as a spring and a screw,must be included in the micro-spindle.In addition,a tapered collet causes tolerance stackup,which may increase rotation error motion.Hydraulic chucks have a non-axisymmetric structure inside the spindle due to the need for an adjusting screw and oil paths.These elements unbalance the rotor mass, increasing rotation error motion at high-speed revolution.Finally, shrink-fit tool holders require specific equipment to heat the device to a high temperature to unclamp a tool,equipment that is too expensive and too large for use with micro-machine tools.One possible way to avoid these problems is to incorporate a shape memory alloy(SMA).SMAs have recently been used in various applications,such as actuators,fasteners,bone fixaters, and so on[7–13].They are lightweight,allow easy and precise installation,yield excellent reliability,and provide good immunity against shock and vibration.By employing SMA for a tool clamp, the clamp can be simplified because