We have developed a femto-second laser machining system for lowering friction on mechanical parts which have nano-size periodic morphologies. The system consists of a femto-second laser, an optical beam shaper, and a five axes mechanical stage to control direction and orientation of the periodic structures on various kinds of mechanical parts. With this system, periodic structures were formed over curved surfaces of metal parts such as ball bearings and inner surfaces of engine cylinder. We have investigated laser power dependence on nano-size periodic morphologies as well as a function of laser scanning speed on the metal surfaces. At a fluence region around 0.5 J/cm
2, a wide area of such fine periodic structures was obtained. By evaluating a friction of such surface, we have found about 25 % reduction in friction coefficient. We have proposed a simple monitoring system to measure the periodicity by reflection spectrum diffracted at the periodic surfaces.
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