Micro-dimple arrays are among the basic microfeatures that plays an important role in performance and reliability enhancement of mechanical systems. The presence of micro-dimples on the workpiece surfaces has been known to have positive impact on the friction control and wear resistance of sliding surfaces. Although several manufacturing processes have been employed to generate micro-dimples on the workpiece surfaces, it is still a challenge to generate micro-dimples utilizing a low-aspect-ratio mask by Through Mask Electrochemical Micromachining (TMEMM). In this paper, AZ-4903 is introduced as a mask due to its availability, low cost as well as chemical resistance. A novel approach of TMEMM is proposed in which very thin masks were used for generation of micro-dimple arrays. Experiments were conducted to study the influence of duty ratio on the machining accuracy and surface properties of the generated micro-dimples. Micro-hole array with an average diameter of 65 μm imprinted on the mask are successfully replicated over SS304 substrate with considerable repeatability. Micro-dimple arrays measuring an undercut of 29.15 μm, depth 32.15 μm and 0.091 μm Ra was successfully fabricated in this study. Moreover, friction test results show that surfaces possessing appropriate micro-dimple array are highly beneficial in reducing frictional co-efficient as compared to smooth surfaces.
Generation of microsurface texture is an important technology for surface engineering that can produce a significant improvement of engineering components in aspects to wear resistance, friction coefficient, load capacities, part lubrication, etc. This research proposes a novel approach of maskless electrochemical micromachining (EMM), which is anodic dissolution based on electrochemical reaction. One reused textured cathode tool with patterned SU-8 2150 mask can fabricate many work samples economically with less time. Maskless EMM set-up with developed EMM cell and vertical crossflow electrolyte supply system is used to generate micro circular patterns on stainless steel (SUS 304) using three different types of electrolytes such as NaCl, NaNO3 and NaCl + NaNO3. The influences of major process parameters such as interelectrode gap (IEG), flow rate, machining time and electrolyte concentration on mean radial overcut and mean machining depth have been investigated using these electrolytes. Out of these three electrolytes, only NaCl + NaNO3 of 20 g l−1 is selected as the best electrolyte with other best parameter settings such as applied voltage of 12 V, duty ratio of 30%, pulse frequency of 5 kHz, flow rate of 3.12 m3 hr−1, IEG of 50 µm and machining time of 3 minutes for generating good textured characteristics with overcut of 27.581 µm and depth of 15.1 µm. Analyses have also been done to investigate the textured characteristics using these electrolytes for acquiring the best parametric combination with suitable electrolyte.
Patterned microstructures are among the basic micro features that are indispensable in improving the tribological performance and dependability of various mechanical components especially Micro-Electro-Mechanical Systems (MEMS). Through Mask Electrochemical Micromachining (TMEMM) is a feasible process for fabricating micro-patterned arrays with controlled dimension, location and density by maintaining suitable surface texture. In this paper, appropriate machining parameters along with optimal electrolyte combination have been utilized for achieving patterned arrays in the form of micro-dimples and micro-square features. Low aspect ratio mask made of a negative PR (AZ 4903) is being introduced during TMEMM due to its low cost, availability and chemical resistance. Pattern of micro-holes with an average diameter of 65μm as well as micro-squares with a side length of 65μm imprinted on the mask are being replicated over SS304 substrate with substantial repeatability. The influence of two major Electrochemical Micromachining (EMM) parameters viz. duty cycle and machining time are investigated on the machining accuracy and surface properties of the micro-dimples generated with mask of lean thicknesses. Circular micro-dimples with an undercut of 29.15μm, depth 44.10μm and R a 0.091μm and square micro-dimples possessing 32.63μm undercut, 40.24μm depth and 0.081μm R a have been successfully fabricated on SS304 by this process of TMEMM.
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