An experimental study on a rapid micro imprinting process

Abstract

Abstract Large-area micro features have been studied a lot due to their diverse functions and vast application prospects in many industrial clusters. Even though many methods have been developed, a flexible fabrication method which could be easily applied on curved surfaces has not been found. In the present work, a rapid micro imprinting (RMI) process employing periodic dynamic load and the feed of workpiece was proposed and studied. A RMI experimental platform was firstly developed and micro dimples arrays were successfully manufactured on the surface of pure copper. Through observation, the forming process of a micro feature was analyzed to consist of impacting and exiting stage. During the exiting stage, the affected zone of the moving imprinting tool was characterized and divided into ploughing-affected zone (PAZ) and deformation-affected zone (DAZ). The comprehensive effects of the tool’s geometry, grain size and process parameters on the forming results were investigated thoroughly by experiments. It was found the tool’s fillet can improve the forming depth but also result in step-shaped features on the wall area of micro dimples. Though increasing the grain size can improve the forming depth, it can enhance the risk of crack in the ploughed surface. Furthermore, the deviation of forming depth was revealed to change with the grain size and reach the highest value at a critical value close to the diameter of the tool feature, which was further discussed in terms of the inhomogeneous material properties influenced by grain size. Finally, based on the analysis of the process parameters including the feed speed and imprinting frequency on the forming depth and undesirable geometry, a process map was plotted to provide guidance for manufacturing micro dimples with reduced undesirable geometry.