Machining with electrochemical discharges is an unconventional technology able to machine several electrically non-conductive materials like glass or some ceramics. After almost 40 years of its first mention in literature, this technology remains an academic application and was never applied in industrial context. The knowledge about machining of non-conducting materials using electrochemical discharge phenomenon is reviewed up to this date with some particular attention to the electrochemical point of view. Some main limiting factors are highlighted and possible solutions are discussed.

Machining of non-conducting materials using electrochemical discharge phenomenon – An overview

The capability of machining intricate features with high dimensional accuracy in hard and difficult-to-cut material has made electrodischarge machining (EDM) process as an inevitable and one of the most popular non-conventional machining processes. In recent years, both EDM and micro-EDM processes are being used extensively in the field of mould making, production of dies, cavities and complex 3D structures using difficult-to-cut tungsten carbide and its composites. The objective of this paper is to provide a state of the art in the field of EDM and micro-EDM of tungsten carbide and its composites. The review begins with a brief introduction on the EDM and micro-EDM processes. The research and developments in electrodischarge machining of tungsten carbide are grouped broadly into conventional EDM of tungsten carbide, micro-EDM of tungsten carbide and current research trends in EDM and micro-EDM of tungsten carbide. The problems and challenges in the area of conventional and micro-EDM of tungsten carbide and the importance of compound and hybrid machining processes are discussed. A summary of the future research directions based on the review is presented at the final section.

A review on the conventional and micro-electrodischarge machining of tungsten carbide

The electrochemical micromachining in non-conventional machining which suffers from process control in micro level. In addition, the work material i.e. stainless steel provides high strength, high toughness and adherence to tool material, hence machining of such material is arduous. However, the use of stainless steel offers its availability in the field of aerospace fuel injection and orthodontic application, since it possess superior qualities. In this paper, the optimization of micro drilling process is carried out in stainless steel by considering certain metrics like feed rate, voltage and duty ratio. The geometric characteristics to drill the tool depends on response parameters like overcut, removal rate of material and conicity. Such parameter determines both the geometric and machining characteristics of the drill bit. The study is evaluated to observe the effect of response and duty ratio parameters such as material removal rate (MRR), machining time and overcut. Further, the conicity is analyzed using VMS images. Finally, the proposed work establishes duty cycle in pulsed electrochemical micromachining domain of hard materials and tests its performance.

Experimental investigation of machined hole and optimization of machining parameters using electrochemical machining

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Advanced Modeling and Optimization of Manufacturing Processes

The electrochemical discharge machining (ECDM) process has a potential in the machining of silicon nitride ceramics. This paper describes the development of a second order, non-linear mathematical model for establishing the relationship among machining parameters, such as applied voltage, electrolyte concentration and inter-electrode gap, with the dominant machining process criteria, namely material removal rate (MRR), radial overcut (ROC) and thickness of heat affected zone (HAZ), during an ECDM operation on silicon nitride. The model is developed based on response surface methodology (RSM) using the relevant experimental data, which are obtained during an ECDM micro-drilling operation on silicon nitride ceramics. We also offer an analysis of variance (ANOVA) and a confirmation test to verify the fit and adequacy of the developed mathematical models. From the parametric analyses based on mathematical modelling, it can be recommended that applied voltage has more significant effects on MRR, ROC and HAZ thickness during ECDM micro-drilling operation as compared to other machining parameters such as electrolyte concentration and inter-electrode gap.

Parametric analysis on electrochemical discharge machining of silicon nitride ceramics

The basic mechanism of the electrochemical discharge machining process is not yet completely understood and is still a subject of investigations. In the present work an attempt has been made to identify the underlying mechanism through experimental observations of time-varying current in the circuit. Based on these observations the basic mechanism of temperature rise and material removal is proposed.

An experimental study of discharge mechanism in electrochemical discharge machining

This paper presents the experimental investigation of pulse-current shaped-tube electrochemical deep hole drilling (PC-STED) of nickel-based superalloy. Influence of five process variables (voltage, tool feed rate, pulse on-time, duty cycle, and bare tip length of tool) on the responses, namely, depth-averaged radial overcut (DAROC), mass metal removal rate (MRRg) and linear metal removal rate (MRRl) have been discussed. Mathematical models have been developed to express the effects of the process parameters on DAROC, MRRg and MRRl. The proposed model permits quantitative evaluation of the hole quality and process performance simultaneously. The results have been confirmed for the profile of the drilled hole and MRRl obtained experimentally. In all the experiments, through holes of 26 mm depth and diameters ranging from 2.205 mm to 3.279 mm were drilled. The results have been explained by the interelectrode gap dynamics prevailing during pulse electrochemical deep hole drilling. Optimum parameters determined from these experiments can be used to efficiently drill high-quality deep holes of high aspect ratio in nickel-based superalloys.

Hole quality and interelectrode gap dynamics during pulse current electrochemical deep hole drilling

In the present work the concepts of dynamic template matching and frame differencing have been used to implement a robust automated single object tracking system. In this implementation a monochrome industrial camera has been used to grab the video frames and track a moving object. Using frame differencing on frame-by-frame basis, a moving object, if any, is detected with high accuracy and efficiency. Once the object has been detected it is tracked by employing an efficient Template Matching algorithm. The templates used for the matching purposes are generated dynamically. This ensures that any change in the pose of the object does not hinder the tracking procedure. To automate the tracking process the camera is mounted on a pan-tilt arrangement, which is synchronized with a tracking algorithm. As and when the object being tracked moves out of the viewing range of the camera, the pan-tilt setup is automatically adjusted to move the camera so as to keep the object in view. Here the camera motion is limited by the speed of the stepper motors which mobilize the pan-tilt setup. The system is capable of handling entry and exit of an object. Such a tracking system is cost effective and can be used as an automated video conferencing system and also has application as a surveillance tool.

Implementation of an Automated Single Camera Object Tracking System Using Frame Differencing and Dynamic Template Matching

The electrochemical discharge machining (ECDM) process is described, along with applications, and the results of the experimental studies are presented. The authors’ experimental set‐up is described, and data from original measurements of synchronized time varying current and temperature are presented. The mechanism which produces the discharge and removes the material is clearly described and evaluated.

Anjali V. Kulkarni

Papers

An experimental study of discharge mechanism in electrochemical discharge machining

Hole quality and interelectrode gap dynamics during pulse current electrochemical deep hole drilling

Implementation of an Automated Single Camera Object Tracking System Using Frame Differencing and Dynamic Template Matching

Measurement of Temperature Transients in the Electrochemical Discharge Machining Process

Electrochemical Spark Micromachining: Present Scenario