Nihon Kikai Gakkai ronbunshu (Jun 2019)
Ultra-precision cutting of roll molds having two-directional wavy microstructures
Abstract
The demand for functional films with surface microstructures is increasing in industry. Functional films with multi-directional wavy components can be applied to fluid drag reduction in turbulent flow applications. In order to implement the high-efficiency manufacturing of functional films, it is necessary to machine wavy microgrooves onto the surfaces of roll molds first. The molds can then be used to imprint patterned films. However, the machining of complicated microgrooves with multi-directional wavy components has never been reported so far. In this study, the authors propose a two-directional wavy microgrooving process by introducing simultaneous reciprocating motions of a diamond cutting tool driven by a slow tool servo. First, microgrooving experiments were conducted by oscillating the tool in two single directions, namely tangential and normal directions of the surface, and the material removal mechanism in each experiment was investigated. In tangential direction tool oscillation, burrs formed on the edge of the groove, which were suppressed by appropriately setting the oscillation amplitude and the tool clearance angle. In normal direction oscillation, shear angle changed significantly with the groove depth, which in turn influenced the groove surface roughness. By synthesizing the results of single-direction oscillation cutting, wavy grooving was performed by reciprocating the tool in both directions simultaneously. As a result, two-directional wavy grooves were successfully machined with form accuracy of 1.2 μm P-V and surface roughness of 12.2 nm Ra. Then, the microgrooved roll molds were used in ultraviolet resin imprinting tests to fabricate films with wavy microstructures. The wavy microstructures were precisely transferred to the resin films with a transcription error of less than 0.7 μm P-V. The results of this study provide a new approach to rapid manufacturing of functional films with wavy microstructures.
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