Effect of various factors influencing the generation of hemispherical micro features using non-conformal RMEDM

Abstract

Non-conformal reverse micro electrical discharge machining (NC-RMEDM) is a variant of conventional RMEDM developed by the present authors wherein modification in the tool is carried out to generate different shapes of micro features. In this study, the effect of various factors like flat bottom and taper bottom hole, inversing the position of tool and workpiece and changing the hole depth have been experimentally investigated to determine the optimal combination required for generating hemispherical shaped micro features. It was found that hemispherical shaped micro feature can be generated by employing tapered bottom blind hole as tool. Buoyancy assisted machining (BAM) with traverse of workpiece (anode) downwards into the tool (cathode) and vice versa, i.e., buoyancy opposed machining (BOM) with traverse of tool downwards into the workpiece were carried out to study the generation of hemispherical micro feature based on inversion of electrode positions. Although both BAM and BOM generated hemispherical shaped feature, BAM is preferred due to reduced machining time as opposed to BOM. Also, increasing the hole depths led to altering the shape of micro feature from hemispherical to cylindrical with hemispherical end and coni-spherical end. An array of hemispherical micro features was fabricated based on the finding from this study, and surface roughness analysis was carried out which showed that irrespective of the position of micro feature on the array, surface roughness at the tip and base of the micro feature is lower as compared to side portion.

Fabrication of array microelectrodes: achieving geometrical characteristics using reverse micro-EDM process

“…Rashed et al [12] used a reverse micro-EDM uses powder metallurgical green compact tool to create a predetermined star-shaped pattern on the aluminum 6061 work surface. Roy et al [13] have studied the influence of several elements, such as flat bottom and taper bottom hole, inverting the location of tool and workpiece, and modifying the hole depth was experimentally explored in this study to identify the ideal combination necessary for manufacturing hemispherical shaped micro features and also discovered that a hemispherical shape micro feature might be created using a tapered bottom blind hole as a tool. Mastud et al [14] concluded that the capacitance controlled the number of pulses per unit of time and energy of sparking and reverse micro-EDM is unstable at very low capacitance (pF) and very high capacitance value (μF).…”

Processing Characteristics of Micro Electrical Discharge Machining for Surface Modification of TiNi Shape Memory Alloys Using a TiC Powder Dielectric

“…Roy et al [ 18 ] analyzed the physical phenomenon behind occurrences of unusually high discharging points in reverse micro EDM by establishing a numerical model of ions and electrons’ movement in the dielectric during machining. To realize the micro-EDM machining of the three-dimensional structure, Roy et al [ 19 ] used reverse micro EDM to generate different shapes of protruded micro features, such as 3D hemispherical and 3D coni-spherical shapes. To study EDM’s surface characteristics, Hsieh et al [ 2 ] showed that the EDM process could successfully machine the ternary TiNiZr SMAs while ensuring its shape recovery ability.…”