Effects of Side Flushing and Multi-Aperture Inner Flushing on Characteristics of Electrical Discharge Machining Macro Deep Holes

This research investigates the effect of machining parameters on material removal rate, electrode wear ratio, and gap clearance of macro deep holes with a depth-to-diameter ratio over four. The experiments were carried out using electrical discharge machining with side flushing and multi-aperture flushing to improve the machining performance and surface integrity. The machining parameters were pulse on-time, pulse off-time, current, and electrode rotation. Response surface methodology and the desirability function were used to optimize the electrical discharge machining parameters. The results showed that pulse on-time, current, and electrode rotation were positively correlated with the material removal rate. The electrode wear ratio was inversely correlated with pulse on-time and electrode rotation but positively correlated with current. Gap clearance was positively correlated with pulse on-time but inversely correlated with pulse off-time, current, and electrode rotation. The optimal machining condition of electrical discharge machining with side flushing was 100 µs pulse on-time, 20 µs pulse off-time, 15 A current, and 70 rpm electrode rotation; and that of electrical discharge machining with multi-aperture flushing was 130 µs, 2 µs, 15 A, and 70 rpm. The novelty of this research lies in the use of multi-aperture flushing to improve the machining performance, enable a more uniform GC profile, and minimize the incidence of recast layer.

INFLUENCE OF THE CONSUMABLE ELECTRODE ROTATION DURING ELECTROSLAG REMELTING ON HYDRODYNAMICS OF A SLAG BATH

Slag melt is a current-carrying medium with intense currents induced by gravitational and electromagnetic forces. The remelted electrode rotation leads to a change in hydrodynamic processes proceeding in a slag bath of the ESR installation and associated primarily with the occurrence of a centrifugal force. The flow pattern, which is developed in the slag bath under this force action, is different from that developed at a stationary consumable electrode. A mathematical model is proposed to assess the impact of consumable electrode rotation on hydrodynamics in a slag bath during electroslag melting. A computer program is created to determine the projections of the flow velocities for a liquid flux near a rotating electrode, the moment of its hydraulic resistance, and the renewal time for the slag bath while being stirred. The critical speed of the rotation of the electrode is determined as a function of its diameter at a transitional flow regime for ANF-6 flux. The dependence of the flux flow velocity on the electrode rotation speed is presented. The moment of the rotating electrode resistance in a slag bath is determined at various electrode diameters and various depths of the electrode immersion into the slag. An expression is proposed for estimating the time of the slag bath renewal. It is also shown that at a small depth in the bath due to its intensive mixing under the action of centrifugal forces, the temperature and chemical composition over the slag bath volume during the ESR process can be considered as constant. The ratio of centrifugal and electromagnetic forces is estimated. The results determine a flow pattern of the liquid slag and th

Pengaruh Putaran Elektroda EDM-Mikro terhadap Ketirusan Lubang pada Penggurdian Baja SKD 61

<p class="MS-ABSTRAK">Micro Electrical Discharge Machining is the development of EDM machines. The purpose of this study is about tapering holes, the results of the drilling process with a micro-EDM machine equipped with a rotating electrode. The difficulty of machining with micro-EDM is that there is often a short circuit between the electrode and the workpiece. For this reason, this research was carried out with a rotating electrode to minimize short circuit. However, electrode rotation can cause deviation or deflection of the electrode tip. The effect of this deviation in the drilling process can cause holes to become taper. The data obtained does indicate this. Furthermore the data is to complement the characteristics of the developed EDM micro machines.</p>

Micro-Drilling of Sapphire Using Electro Chemical Discharge Machining

Electrochemical discharge machining (ECDM) refers to a non-traditional machining method for performing effective material removal on non-conductive hard and brittle materials. To increase the ECDM machining efficiency, traditionally, the method of increasing the machining voltage or increasing the electrolyte concentration is used. These methods can also cause overcut reaming of the drilled holes and a rough surface on the heat affected area. In this study, an innovative combinational machining assisted method was proposed and a self-developed coaxial-jet nozzle was used in order to combine two assisted machining methods, tool electrode rotation and coaxial-jet, simultaneously. Accordingly, the electrolyte of the machining area was maintained at the low liquid level and the electrolyte was renewed at the same time, thereby allowing the spark discharge to be concentrated at the contact surface between the front end of the tool electrode and the machined material. In addition, prior to the machining and micro-drilling, the output of the machining energy assisted mechanism was further controlled and reduced. For the study disclosed in this paper, experiments were conducted to use different voltage parameters to machine sapphire specimens of a 640 μm thickness in KOH electrolyte at a concentration of 5 M.

Experimental Study on Machining Engineering Ceramics by Electrochemical Discharge Compound Grinding

Since engineering ceramics have many characteristics, including hardness, brittleness, and high melting point, traditional machining methods can no longer play a useful role in precision machining. Based on this situation, a platform of electrochemical discharge compound mechanical grinding was constructed and is presented in this paper, and machining experiments of micro-grooves were carried out in alumina ceramics. Grooves were observed by scanning electron microscope (SEM), and the morphology and the groove width of micro-grooves under different machining parameters were compared and analyzed. Furthermore, in order to study the improvement effect of mechanical grinding on machining quality, the surface roughness of micro-grooves was measured by a confocal material microscope. The results show that as the pulse power supply voltage increases or the frequency decreases, the width of the micro-grooves increases, and the morphology of the micro-grooves first improves and then deteriorates. With the increase of tool electrode rotation speed, the width of micro-grooves first increases and then remains unchanged, and the morphology and the surface roughness of micro-grooves first improves and then remains stable. Finally, the optimal parameters (power voltage of 20 V, pulse frequency of 400 Hz, electrode rotation speed of 600 rpm) were chosen to machine micro-grooves with good quality.

Effect of deep cryogenic treatment on copper electrode for non-traditional electric discharge machining (EDM)

In the last few decades, non-traditional machining made the machining process easier than the traditional machining method. Electric discharge machining (EDM) is one of the most prominent methods of non-traditional machining processes. By the use of EDM, a complex profile and high hardness materials can be easily machined, which cannot easily be machined by the traditional machining method. EDM is widely used by the industries. This paper investigates an experiment with the cryogenically treated copper electrode and an ordinary copper electrode with various input parameters like the electrode rotation, gap voltage and discharge current for an EN24 (a high-strength and wear-resistant steel) material. An experiment was performed with electric discharge machining. Designs of an experiment are carried out using the Taguchi approach. An orthogonal L16 array prepared and used the different combination of the three input parameters (current, electrode rotation and gap voltage) to find an optimum value of the factors. The output factors are the overcut (OC), the tool wear rate (TWR) and surface roughness (Ra). The optimal level and importance levels of each of these parameters are obtained statically using an analysis-of-variance (ANOVA) table through the analysis of the S∕N ratio. The study also compares the theoretical and experimental values of the overcut, tool wear rate and surface roughness for traditional and non-traditional EDM. The following research finds optimal or dominating factors (current and rotational speed) for the TWR and Ra in both traditional and non-traditional electric discharge machining; moreover there was a reduction of approximately 9 % in overcut, 13.25 % in the tool wear rate and 15.75 % in surface roughness for the deep cryogenic and non-traditional machining process.