Dual-crankshaft out-of-phase balanced drive mechanism applied to high-frequency scraping of high-density microcavities patterns

Abstract

This study examines the development of a “dual-crankshaft out-of-phase balanced drive mechanism” and its application in the realization of high-frequency scraping in the production of highly precise, extremely dense microconcavity patterns. The high-density microcavity mold can produce micro-lens arrays, which achieve energy saving through the light-gathering effect. A monocrystalline diamond tool driven by the designed positive drive mechanism facilitates scraping at a high-frequency using positively reciprocated motion. To inhibit system vibration caused by a single crankshaft, a dual-crankshaft out-of-phase balanced drive mechanism is developed, which allows both the primary drive shaft and balance shaft to possess identical eccentric distance with their eccentric forces going in opposite directions. The design offsets the eccentric force made by revolution of the primary drive shaft against the simultaneous force made by the revolving balance shaft. Experiments show that when system vibration error is restrained to 1-μm, the single crankshaft tool reaches a drive frequency of 15 Hz. While under the dual-crankshaft out-of-phase setup, drive frequency reached up to 50 Hz. Further experimental results demonstrated that the dual-crankshaft out-of-phase balanced drive mechanism has the capability of scraping a vast microconcavity pattern with high-precision, -integrity and -consistency. Characteristic surface roughness of microcavities was below Ra 0.024 μm and feature edges were burr-free. In addition, this paper discusses in detail: the material shear rate, scraping force prediction, influences of the workpiece forward feed-rate and tool actuation frequency as well as the relationship between major and minor axes in microconcavity formation.