Deionized Water Electrochemical Machining Hybridized with Alumina Powder Polishing for Microcavity of M-333 Mold Steel

An electrochemical machining (ECM) process for microcavity fabrication with deionized water (DI-water) and an ECM polishing hybrid with alumina powder of 1.0 μm grains on a single micro-EDM machine are proposed. The process adopts tungsten carbide as tool electrode and M-333 tool steel as the mold material. It reveals that employing the 30 μm/min feed rate with 50 mA and 0.2 ms of pulse-width is suitable for DI-water electrochemical machining. The DI-water ECM process can achieve an excellent surface roughness at Ra 0.169 µm on a semispherical round cavity. Combining the ECM with hybrid polishing with the alumina powder can achieve a better profile for a much deeper cavity than pure electrolytic discharge machining. The hybrid ECM polishing can efficiently finish a micro square insert of 0.6 mm length at 64 μm depth. Such ECM milling can achieve an S-shaped microchannel of radius 1.0 mm and a slot of 1.0 × 0.5 mm2 with 110 μm depth, demonstrating its feasibility and the surface integrity with accurate profile and roughness of Ra 0.227 μm. This study provides a cost-effective scheme for micro mold fabrication with a conventional micro-EDM machine tool and an intuitive and convenient optional process. However, some micro-electrical discharges occurred due to the breakdown of insulation, which creates micro craters on the surface of the parts.

Experimental investigations on the wear behaviour of micro-EDM-fabricated textured tools during dry turning of Ti6Al4V

Purpose This paper aims to focus on analysing the wear characteristics of tungsten carbide tools on which various micro patterns are fabricated to study its effect on the machinability of Ti-6Al-4V at dry turning conditions. Design/methodology/approach Micro-patterns such as dimples, linear grooves and a novel combination of dimples and linear grooves were fabricated on rake faces of uncoated tools by micro-EDM process. Impact of these patterns on tool wear and chip morphology characteristics under dry machining conditions were analysed, and their performances were compared with the non-textured tool (NTT). Findings Encouraging results in terms of minimal tool wear and favourable chip morphology characteristics were observed in case of all the textured tools, which demonstrated better tribological characteristics in contrast to NTT. The average flank wear was reduced by 43.5, 32 and 24.7% in dimple textured tool (DTT), linear textured tool (LTT) and hybrid textured tool (HTT), respectively, as compared to NTT. The average chip curl diameters measured for NTT, DTT, LTT, and HTT were observed to be 6.60, 3.51, 4.0 and 4.31 mm, respectively. Originality/value The contribution of this work lies in fabricating innovative patterns using cost-effective micro-EDM process and analysing how the patterns, depending upon their dimensional area and wear debris accumulation characteristics, influence the machinability of Ti-6Al-4V in the absence of any lubrication mediums.

A Study of Fabricating Nano-W Colloid by Discharge Energy Enhancement of the micro-EDM System

This study enhanced the discharge energy of an existing micro-electric discharge machining (EDM) system to provide the system with the ability to prepare nano-tungsten (nano-W) colloid. The energy- enhanced EDM system, referred to as the upgraded-micro-EDM system, enables spark discharge using tungsten wires immersed in deionized water to produce nano-W colloids. Compared with the chemical preparation method, the processing environment for preparing colloids will not have nanoparticle escape in this study. Among the nano-W colloids prepared using the upgraded-micro-EDM system and an industrial EDM system, the colloid prepared by the upgraded-micro-EDM system exhibited more favorable absorbance, suspensibility, and particle size. The colloid prepared by the upgraded-micro-EDM system with the pulse on time and off time of 10–10 µs had an absorbance of 0.277 at the wavelength of 315 nm, ζ potential of −64.9 mV, and an average particle size of 164.9 nm. Transmission electron microscope imaging revealed the minimum particle size of approximately 11 nm, and the X-ray diffractometer spectrum verified that the colloid contained only \({\text{W}}_{2.00}\) and W nanoparticles. Relative to industrial EDM applications for nano-W colloid preparation, the upgraded system boasts lower costs and smaller size, and produces nano-W colloid with superior performance. These advantages contribute to the competitiveness of electrical spark discharge method in the preparation of high-quality nano-W colloids.

Fabrication of hydrophobic surfaces on Titanium using Micro-EDM exhibiting antibacterial properties

Microbial contamination on medical assistive devices has been the major challenge for biomedical industries. The present work is focused on producing patterned surfaces on commercially pure Titanium (cp-Ti) using Micro-Electrical Discharge Machining (Micro-EDM) technique, and the feasibility of patterned surface in restricting bacterial growth. Geometrical patterning in form of micro-holes have been produced on cp-Ti biomaterials with Micro-EDM in two forms, one with 20 µm inter-distance forming a dense pattern and the other with 60 µm inter-distance forming a sparse pattern. The patterned surface establishes the degree of hydrophobicity as 130° and 106° for densely patterned and sparsely patterned surfaces respectively. Further, the effect of bacterial adhesion over the textured cp-Ti surfaces are challenged with model bacteria gram negative Escherichia coli (e.coli) in Luria broth (LB) agar media. The Colony Forming Unit (CFU) count obtained for densely patterned surface compared with that of non-patterned surface reflects 90% reduced bacterial growth. The instances of pattern formation and bacterial growth have been observed with Scanning Electron Microscopy. The enhanced material properties with micro-patterning that combat microbial activities on the biomaterial surface proves its efficacy in adoption for biomedical applications, with significant reduction in bacterial contamination on medical devices or implants, leading toward reduced healthcare risks and issues related to bacterial infections on the biomaterials.

Optimization of micro-EDM drilling on titanium alloy (Ti-6AL-4V) using RSM and Neural Network

In modern manufacturing industries, micro machining technology is widely used to machine micro parts for various applications such as in MEMS, die and tool industries, etc. Micro electric discharge machining (Micro-EDM) is widely used in die and tool making. This paper investigates three different input machining parameters such as pulse on time, pulse off time, and servo voltage of micro electric discharge machining performances of tool wear (TW) and Diametrical accuracy (DA) of a hole on titanium alloy (Ti-6Al-4V) using copper micro electrodes of ϕ 400μm. The experiments ate conducted out with the Box-Behnken design of Response Surface Methodology (RSM). The neural network is used for the optimization of multi response by fitting the regression model. ANOVA is also performed to find the significant contribution of the machining parameter. The predicted optimal machining values with the maximum error of 12.72% for tool wear and 8.78% for diametrical accuracy was achieved on comparing with experimental results.