| Surface texture with a certain shape and dimensional distribution has great potential application in antifriction,wear reduction,sealing,anti-sticking,hydrophobicity and so on,which can improve mechanical seal performance,friction and wear properties,heat exchange performance and biomimetic properties.The fabrication of large-area micro-dimple arrays with high machining accuracy becomes a research focus.Through-mask electrochemical micromachining(TMEMM)is an effective method for generating micro-dimple arrays,but there are also some shortcomings.In conventional TMEMM based on photoresist,the photoresist can be used only once and it need to be removed after machining,taking a long time and cost much.Due to the marginal effect of electrical field,the dimensional uniformity of the surface texture is poor.In this paper,high-pressure hydrostatic electrolyte is introduced to avoid the defects of conventional TMEMM,and the major work has been done as follows:(1)The lithography process is modified to fabricate PDMS through-hole mask.A photoresist mold was prepared by optimized lithography process with double-deck SU-8 photoresist,and the PDMS mask with a via diameter of only 36 μm was fabricated using the vacuum-aided method.(2)Three product states,low product state,transition state and high product state,are proposed during the high-pressure hydrostatic TMEMM.Compared to the transition state,surface texture with high machining accuracy can be obtained at both low product state and high product state.An array of 14,000 micro-dimples was successfully fabricated with a diameter and a depth of 105.95 and 9.79 μm,respectively,and with diameter and depth deviations of 0.59 and 0.21 μm,respectively.Based on PDMS mask with a via diameter of 36 μm,an array of 380,000 micro-dimples was successfully fabricated at one time,with a diameter and a depth of 38.2 and 6.1 μm,respectively.(3)The reasons for high dimensional uniformity during high-pressure hydrostatic TMEMM are explored.The electric field models of traditional TMEMM and high-pressure hydrostatic TMEMM were established.The simulation results showed that high-pressure hydrostatic TMEMM could reduce or even eliminate the marginal effect of electrical field and improve the dimensional uniformity of the micro-dimple arrays.The experimental results indicated that the high-pressure hydrostatic electrolyte could improve the dimensional uniformity and surface roughness of the micro-dimple arrays.(4)The application of surface texture generated by high-pressure hydrostatic TMEMM is investigated.Micro-groove and Micro-bump arrays were successfully prepared on the surface of phosphor bronze.Micro-dimple arrays with high machining accuracy were successfully prepared on the surface of perforated workpiece and gear pump by using high-pressure hydrostatic electrolyte.An array of 5,400 micro-dimples was successfully fabricated with a diameter and a depth of 107 and 11.9 μm,respectively,and with extreme difference of 1.1 and 0.6 μm,respectively. |
