Unravelling a novel oscillation-loaded dynamic micro embossing process : experiment and modelling

Abstract

A new oscillation-loaded dynamic micro embossing (DME) process was developed as an efficient and flexible deformation-based method to manufacture micro structures on both planar and curved surfaces. This unique process utilizes current to stimulate miniature punch fixed to a small electrodynamic vibrator to oscillate and thus periodically emboss part surface, contributing to the advantages of high efficiency, low forming force and high flexibility. However, the geometry and morphology of micro structure formed by DME process is difficult to control and tailor due to the deficient understanding of the electro-mechanical coupled forming process. Therefore, experimental investigations and theoretical modelling were conducted to unravel the process mechanics and the quantitative relationship between structure geometry and process parameters. Employing punch with single rectangular strip feature, micro grooves and cubic pillars with different widths were obtained on the pure copper workpieces of different grain sizes. The geometry of the formed micro structure was found to be slightly asymmetrical as the result of the kinetic and mechanical interaction between punch and workpiece during forming process. In addition, the quality of formed micro structures was significantly influenced by both the punch feature size and material grain size. The reduction of punch feature size or the rise of grain size can aggravate surface roughening morphology and thus the dimension scatter of formed micro structures. Based on the energy conversion mechanics during the DME process, an analytical structure geometry model to predict the structure geometric dimensions with different process parameters was established and validated via corroboration with experimental results. Furthermore, the influence of process parameters on the structure depth formability was thoroughly revealed. The structure depth formability first surges with the current frequency and then declines when the current frequency exceeds the resonant frequency, and can be significantly improved by elevating the current amplitude.