Experimental Study On Fabrication Of Micro-dimple Arrays Using Modified Through-mask Electrochemical Micromachining With Its Interelectrode-gap Filled With Flexible Porous Material

It has been found that well-defined micro-dimple arrays can reduce friction, wear and improve heat transfer, fluid motion state effectively. Because ECM has the advantages including ability to machine various materials that are regardless of hardness and toughness, good surface quality showing few residual stresses as well as no heat-affected layer, it has been viewed as one of the most effective processes to fabricate micro-dimples on the metal surface. Non-adhesive active through-mask electrochemical micro-machining process has the advantages of high machining efficiency and reusable mask, thus, it has great potential in the machining of micro-dimple arrays. To solve the problems of the electrochemical micro-machining process using non-adhesive active through-mask,such as complexity of fixing the soft through-mask on the workpiece and less applicability to non-planar surface, this dissertation proposed a new through-mask electrochemical micro-machining(TH-EMM) process which uses a removable mask and has flexible porous material in its inter-electrode gap. The feasibility of this newly developed process was verified by the experiment and favorable micro-dimple arrays were produced. With the financial co-support of the following programs: Technology Innovation Talent Support Program of Henan Province-“Modified through-mask electrochemical micromachining method with flexible porous media filled in the inter-electrode gap”, Technology Innovation Team Support Program of Henan Province-“High performance nontraditional machining technology and equipment ”and Innovation Team Support Program of Henan Polytechnic University- “Micro-structure Nontraditional machining technology on metal surface”. This modified process were further researched systematically in this dissertation, with the aims of analyzing the effects of some key process variables on the machining efficiency and qualities of the machined micro-dimples, as well as of obtaining the optimal process parameters. The main research works are as follows:(1) The feasibility of this newly developed process was verified by theoretical analysis and experiments. Special electrochemical machining device was developed.(2) Processing parameters in DC, such as, voltage, aspect ratio, the original inter-electrode gap, pressing force were investigated to get their effects on the machining efficiency and qualities of the micro-dimple arrays. The results showed that: Under the selected experimental conditions, the optimal process parameters for improving machining efficiency were h/d0 =0.2, H=2mm, F=10N. The optimal process parameters for improving uniformity of size were h/d0 =0.2, H=1mm, F=50N. Profiles of the micro-dimple array were different and morphologies were mainly spiral texture.(3) Processing parameters in pulsed power, such as, the pulse period and duty ratio were investigated to get their effects on the machining efficiency and qualities of micro-dimple arrays. The results showed that: Under the selected experimental conditions,the optimal process parameters for improving machining efficiency were T=80ms or T=120ms, q=0.6. The optimal process parameters for improving uniformity of size were T=80ms, q=0.2 or q=0.6. Profiles of the micro-dimple array were mainly shallow basin and morphologies were smooth at the bottom, roughness in the edge.