Micro-texturing on flat and cylindrical surfaces using electric discharge micromachining

The present work discusses micro-texturing on flat and cylindrical surfaces using the electric-discharge micromachining (EDMM) process. The arrays of micro-dimples are generated on flat Ti-6Al-4V surfaces using a block–electric discharge grinding (block-EDG)–fabricated microtools of an average diameter of 148 µm and 105 µm. Large-area surface texturing on flat Ti-6Al-4V and aluminium surfaces are performed to analyse the variation in water contact angle with varying depths of dimples. Adopting the electric discharge–milling (ED-milling) strategy, micro-pillars of dimensions 242 µm × 166 µm × 50 µm are machined on flat Ti-6Al-4V surfaces. The EDMM process for non-flat surfaces, such as curved (internal and external), spherical and freeform surfaces, is receiving attention in various applications. Machining of the aforementioned surfaces using the EDMM process appears to be problematic, due to the continuous change in curvature, which results in the subsequent spark gap variation. In the present work, processing of cylindrical surfaces for micro-features generation, such as micro-dimple arrays, has been attempted. Arrays of micro-dimples are machined on copper and Ti-6Al-4V cylindrical surfaces. A precise indexing setup is fabricated to hold and index the workpiece at the desired angular positions. Unlike machining on flat surfaces, the relative dimensions of the tool and the workpiece’s curvature result in non-uniform wear at the tool’s end cross-section. Owing to this non-uniform wear of tool electrode caused by the curvature effect of the workpiece, the formation of a microscopic bump/spike is observed on the dimple’s bottom. The depth of the dimple up to which the entire bottom surface of the tool is not exposed to the sparks is defined as its critical depth. For a combination of a tool and a workpiece of diameters 500 µm and 5 mm, respectively, the critical depth of the dimple is found to be 12.53 µm. However, the critical depth increases with a decrease in workpiece diameter, provided the diameter of the tool is constant.

Correlation of Three-Dimensional Roughness Parameters With the Crater Dimensions in μED-Milling of Cryogenic-Treated Tool and Workpiece

Microfluidics is one of the rapidly growing markets in the present era of miniaturization. Microchannels have wide applications in various fields such as biomedical, mechanical, electrical, and chemical sciences. Machining microfeatures with high aspect ratio in metals is difficult by mechanical and lithography-based processes. Micro-electric discharge milling is a suitable process to machine microcavities and microchannels in all electrically conductive materials. The main disadvantage of this process is its very low material removal rate. Improving the machining performance of micro-electric discharge machining (μEDM) is a research area that attracts researchers and remains as an unfulfilled agenda. The aim of this study is to improve the machining performance of micro-electric discharge milling process by investigating the performance of cryogenically treated tool and workpiece materials. Since surface roughness determines the minimum feature size machinable by any micromachining process and also it is an important factor in determining the flow characteristics of microchannels, a detailed comparative study was conducted on the three-dimensional (3D) surface quality parameters along with machining performance while using all four different combinations of untreated and cryogenically treated tool and workpiece, and the roughness parameters are correlated with the erosion behavior. The study revealed significant change in material removal rate and erosion pattern due to cryogenic treatment.

Modeling of Material Removal Mechanism in Micro Electric Discharge Milling of Ti-6Al-4V

Micro EDM milling process is accruing a lot of importance in micro fabrication of difficult to machine materials. Any complex shape can be generated with the help of the controlled cylindrical tool in the pre determined path. Due to the complex material removal mechanism on the tool and the work piece, a detailed parametric study is required. In this study, the influence of various process parameters on material removal mechanism is investigated. Experiments were planned as per Response Surface Methodology (RSM) – Box Behnken design and performed under different cutting conditions of gap voltage, capacitance, electrode rotation speed and feed rate. Analysis of variance (ANOVA) was employed to identify the level of importance of machining parameters on the material removal rate. Maximum material removal rate was obtained at Voltage (115V), Capacitance (0.4μF), Electrode rotational Speed (1000rpm), and Feed rate (18mm/min). In addition, a mathematical model is created to predict the material removal