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In the current research work, in-house developed and fabricated multi-axis near-dry Electrical Discharge Machine (near-dry EDM) has been used having different tool positions, i.e. tool electrodes in horizontal position (Case-I) and vertical positions (Case-II) as a novel machining techniques in hard-to-reach places and also to improve the process performance. Design of Experiment tool has been used with three process parameters: voltage, discharge current, and pulse-on-time for experimentation purposes. In order to maximize Material Removal Rate (MRR), it was necessary to compare and enhance these parameters in both cases, i.e. Case-I, and Case-II. The machining process is significantly influenced by the vertical tool positions, as indicated by the largest percentage contribution in the Analysis of Variance results. The voltage has the least influence, while the pulse-on time is relatively less. In contrast, for the horizontal tool position, the voltage proved the most prominent factor in terms of influence, while the current ranked second in significance. Conversely, the pulse-on time exhibited the least impact among the three factors. The highest MRR 2.45 mm3/min was achieved in the vertical tool position while in horizontal machining, the highest MRR 0.144 mm3/min was observed. These findings provide valuable insights into the multi-axis near-dry EDM with proposed methodology. [ABSTRACT FROM AUTHOR]

Micro Electro-Discharge Machining is a precision machining process that uses electrical discharge to produce small-scale components with high accuracy. A metal workpiece is machined in this process by repeatedly generating spark between a tool electrode and the workpiece, removing material in a controlled manner. The significance of µ-EDM lies in its ability to produce highly accurate and complex components with a high surface finish, making it ideal for use in various industries, including aerospace, medical, and electronics. The critical parameters to the success of µ-EDM include the electrical discharge energy, voltage, current, pulse duration, and spark gap between the tool electrode and workpiece, including the shape and size of the tool electrode. This review article discusses the µ-EDM process used to machine biological materials and also examines the µ-EDM, dry µ-EDM procedure, and the features of biomedical materials for biocompatibility, 3D micro shape machining with tool wear composition, and thin film coating for microelectrodes. The impact of introducing nanoparticles to dielectric fluids is further clarified in this article. This study addresses the prospective future research subjects and application areas for the µ-EDM process in order to fulfill the demanding criteria for biomaterials and their usage in the production of bioimplants. [ABSTRACT FROM AUTHOR]

The shaping of the electrically insulating ceramic component in post sintered state has always been a difficulty in developing ceramic applications. Wire electrical discharge machining is an ascertained option to produce near net shape products in conductive materials. When it comes to insulating ceramics, sustaining the threshold electrical conductivity comes into the picture. This paper explores the feasibility of wire electrical discharge machining of Y2O3 stabilized ZrO2 with graphite powder additive mixed distilled water to replace the kerosene. In this research, the assisting electrode method has been employed to provide electrical conductivity to the work material to have initial electrical contact. Sparking initiates at assisting electrode coating and further conservation of electrical contact leads to successful engraving. Along with graphite concentration, the servo reference voltage is varied to study the kerf width variation deciding the accuracy of the component. The optimum graphite concentration was found to be in the range of 3 to 5 g/ltr. For this range, the ceramic erosion experienced to be most stable through optimum kerf width. Continuous increase in the kerf was observed with increasing gap voltage for individual graphite concentration. [ABSTRACT FROM AUTHOR]

A strong microjet is generated in an electro-conjugate fluid between a positive and a ground electrode in a high external electric field. We here elucidate the mechanism and characteristics of this strong microjet by means of lattice Boltzmann simulations. In this analysis, we assume that charges are injected from the surface of a positive electrode at the position of a locally high concentrated electric field. When the effect of the Coulomb force is much more dominant than the viscous force, a strovnng microjet between the positive and the ground electrode is generated. This microjet attains a maximum velocity, collides with the ground electrode and disperses in oblique directions. The flow rate resulting from the appearance of a microjet increases with increasing electric field strength in a proportional manner. The present numerical results in respect to the visualisation of a microjet are in good agreement with a corresponding experiment. [ABSTRACT FROM AUTHOR]

In this study, machining of AA6061/10%SiC composite fabricated by mechanical stir casting process has been experimentally investigated using electrodischarge machining (EDM) process with tungsten-powder-mixed dielectric fluid (PMEDM). Peak current, pulse on-time, pulse off-time, and gap voltage are selected as machining parameters. Mathematical relation has been established for response quality characteristics like surface roughness with and without tungsten powder dielectric fluid using Central Composite Rotatable Design (CCRD) through response surface methodology (RSM). Surface characteristics like microhardness, surface topography, and white recast layer have been evaluated through scanning electron microscope (SEM), electrodispersive X-ray spectroscopy (EDS), and micro-Vicker hardness. Results have also been compared with simple EDM of AA6061/10%SiC composite without powder-mixed dielectric fluid. The existence of tungsten powder in dielectric fluid increases surface quality owing to decrease in number, size, and depth of craters formed while machining. Thickness of white recast layer is reduced whereas surface hardness is increased when machined with powder-mixed EDM. [ABSTRACT FROM AUTHOR]

Local and systemic effects associated with polychlorobiphenyl (PCB) exposure are well established in animal and human studies. PCBs are highly resistant to dechlorination and persist for long periods of time in the environment. Documented spills of PCB-contaminated fluids occurred at a federal scrap yard, where, historically, capacitors containing PCB dielectric fluid were crushed. The purposes of this investigative, industrial hygiene study were: (1) to evaluate the potential occupational health hazards and associated impacts experienced by environmental personnel involved in site investigation and environmentalsampling activities at the federal scrap yard; (2) to characterize environmental personnel exposures to airborne concentrations of PCBs (42 and 54% chlorine); and (3) to determine airborne concentrations ofPCBs at specific worksite locations of maximum anticipated air contaminant concentration. Air samples were collected and analyzed in accordance with National Institute for Occupational Safety and Health Method 5503 and U.S. Army Environmental Hygiene Agency Technical Guide No. 141. Sampling media consisted of 13-mm glass fiber filters (without binders) in Swinnex cassettes, followed by glass tubes (7-cm length, 6-mm outer diameter, 4-mm inner diameter) containing two sections of 30/48 mesh deactivated Florisil(r). Sampling involved 30-minute time-weighted average (TWA) excursion limit (TWAEL) and 8-hour TWA (TWA.) periods. For personal breathing zone (BZ) air samples, the calculated TWAEL concentrations of PCBs ranged from <0.0859 to <0.0896 mg/m3 [n =14, geometric mean (GM) <0.0873 mg/m3, geometric standard deviation (GSD) -1.01151 and thecalculated TWA8 concentrations of PCBs ranged from <0.0110 to <0.0127 mg/m3 (n = 12, GM < 0.0121 mg/m3, GSD = 1.0422). For environmental general area (GA) air samples, the calculated TWA, concentrations of PCBs ranged from <0.0120 to <0.0147 mg/ [ABSTRACT FROM AUTHOR]