Showing papers on "Electrical discharge machining published in 2001"

Electrical Discharge Machining

Abstract: This book is focused on electrical discharge machining (EDM) fundamentals. These are the items common to all EDM machines. Fundamentals are concerned with the spark, how the spark is controlled, what causes overcut, and the importance of the dielectric fluid. With regard to the workpiece, fundamentals consider what effect the spark has on the metallurgy and how the surface finish is produced and controlled. The book also describes the development of EDM, the EDM machining system and process, the EDM sparking system, the power supply (generator), spark voltage, electrode servo systems, dielectric systems, ionization and electrode wear, chips, the EDM surface, DC arcing, different kinds of EDM, automatic servo system operation, and electromagnetic radiation. This text will serve as the primer on the EDM machining process, allowing the people using EDM to become more efficient and the machines more productive.

Accretion of titanium carbide by electrical discharge machining with powder suspended in working fluid

Abstract: A surface modification method by electrical discharge machining (EDM) with a green compact electrode has been studied to make thick TiC or WC layer. Titanium alloy powder or tungsten powder is supplied from the green compact electrode and adheres on a workpiece by the heat caused by discharge. To avoid the production process of the green compact electrode, a surface modification method by EDM with powder suspended in working fluid is proposed in this paper. After considering flow of working fluid in EDM process, the use of a thin electrode and a rotating disk electrode are expected to keep powder concentration high in the gap between a workpiece and an electrode and to accrete powder material on the workpiece. The accretion machining is tried under various electrical conditions. Titanium powder is suspended in working oil like kerosene. TiC layer grows a thickness of 150 μm with a hardness of 1600 Hv on carbon steel with an electrode of 1 mm in diameter. When a disk placed near a plate rotates in viscous fluid, the disk drags the fluid into the gap between the disk and the plate. Therefore, the powder concentration in the gap between a workpiece and a rotational disk electrode can be kept high. A wider area of the accretion can be obtained by using the rotational electrode with a gear shape.

Predictions on surface finish in electrical discharge machining based upon neural network models

Abstract: Predictions on the surface finish of work-pieces in electrical discharge machining (EDM) based upon physical or empirical models have been reported in the past years. However, when the change of electrode polarity has been considered, very few models have given reliable predictions. In this study, the comparisons on predictions of surface finish for various work materials with the change of electrode polarity based upon six different neural-networks models and a neuro-fuzzy network model have been illustrated. The neural-network models are the Logistic Sigmoid Multi-layered Perceptron (LOGMLP), the Hyperbolic Tangent Sigmoid Multi-layered Perceptron (TANMLP), the Fast Error Back-propagation Hyperbolic Tangent Multi-layered Perceptron (Error TANMLP), the Radial Basis Function Networks (RBFN), the Adaptive Hyperbolic Tangent Sigmoid Multi-layered Perceptron, and the Adaptive Radial Basis Function Networks. The neuro-fuzzy network is the Adaptive Neuro-Fuzzy Inference System (ANFIS). Being trained by experimental data initially screened by the Design of Experiment (DOE) method, the parameters of the above models have been optimally determined for predictions. Based upon the conclusive results from the comparisons on checking errors among these prediction models, the TANMLP, RBFN, Adaptive RBFN, and ANFIS model have shown consistent results. Also, it is concluded that the further experimental results have agreed to the predictions based upon the above four models.  2001 Elsevier Science Ltd. All rights reserved. 1. Intrduction Electrical discharge machining (EDM), is a nontraditional machining process for metals removing based upon the fundamental fact that negligible tool force is generated during the machining

Semi-empirical model of surface finish on electrical discharge machining

Abstract: A semi-empirical model of surface finish on work for various materials has been established by employing dimensional analysis based upon pertinent process parameters in the electrical discharge machining process. The parameters of the model, such as peak current, pulse duration, electric polarity, and properties of materials, have been initially screened by the design of experiment procedure. Then, they have been systematically analyzed and later verified by making use of the Taguchi method. A model based on dimensional analysis of the model parameters has been established for verification. In addition, the predictions based on the semi-empirical model with the best-fitting parameters by nonlinear optimization methods are in good agreement with the experimental verifications.

Effect of electrical discharge machining on the characteristics of carbon fiber reinforced carbon composites

Abstract: This work investigated electrical discharge machining (EDM) of carbon fiber reinforced carbon composite material. The characteristics of composites machined by EDM were studied in terms of machining parameters. An empirical model of the composites was also proposed based on the experimental data. The composite material was produced by an electrical discharge sinker using a graphite electrode. The workpiece surface and resolidified layers were examined by scanning electron microscopy (SEM). Moreover, surface roughness was determined with a surface profilometer. Experimental results indicate that the extent of delamination, thickness of the recast layer, and surface roughness are proportional to the power input. The EDM process effectively produces excellent surface characteristics and high quality holes in composites under low discharge energy conditions.

Development of the Cylindrical Wire Electrical Discharge Machining Process

Abstract: Results of applying the wire Electrical Discharge Machining (EDM) process to generate precise cylindrical forms on hard, difficult-to-machine materials are presented. The design of a precise, flexible, and corrosion-resistant underwater rotary spindle is first introduced. A detailed spindle error analysis identifies the major sources of error at different frequency spectrum. The spindle has been added to a conventional two-axis wire EDM machine to enable the generation of free-form cylindrical geometries. The mathematical model for material removal rate of the free-form cylindrical wire EDM process is derived. Experiments were conducted to explore the maximum material removal rate for cylindrical and 2D wire EDM of carbide and brass work-materials. Compared to the conventional 2D wire EDM of the same work-material, higher maximum material removal rates may be achieved in the cylindrical wire EDM, possibly due to better debris flushing condition.

Surface Improvement Using a Combination of Electrical Discharge Machining with Ball Burnish Machining Based on the Taguchi Method

Abstract: This study investigates the feasibility of improving surface integrity via a novel combined process of electrical discharge machining (EDM) with ball burnish machining (BBM) using the Taguchi method. To provide burnishing immediately after the EDM process, ZrO 2 balls were attached to the tool electrode in the experiments. To verify the optimal process, three observed values, i.e. material removal rate, surface roughness, and improvement ratio of surface roughness were chosen. In addition, six independent parameters were adopted for evaluation by the Taguchi method. From the ANOVA and S/N ratio response graph, the significant parameters and the optimal combination level of machining parameters were obtained. Experimental results indicate that the combined process effectively improves the surface roughness and eliminates the micro pores and cracks caused by EDM. Therefore, the combination of EDM and BBM is a feasible process by which to obtain a fine-finishing surface and achieve surface modification.

Effects of workpiece rotation on machinability during electrical-discharge machining

Abstract: This work presents a novel rotary (EDM) electrical-discharge machining cutting process for a hard-to-machine cylindrical workpiece. An experimental analysis was carried out on an AISI D2 tool steel with a copper electrode. The effects of machining parameters such as pulsed current, pulse on-time, and workpiece rotation on material removal rate and surface roughness were analyzed. These effects were compared with those of conventional EDM without workpiece rotation. Experimental results indicated that the rotation enhanced the dielectric flow, thus effectively helping flush the debris from the gap between the electrodes. In addition, the material removal rate (MRR) increased with the rotation speed of the workpiece, whereas conventional EDM delivers only half the MRR. Surface roughness improves with increased rotation speed, a phenomenon that is attributed to the reduced recast layer during EDM.

Development of Optimum Electrodischarge Machining Technology for Advanced Ceramics

Abstract: In recent years, ceramic materials with improved properties have been developed to meet a large number of industrial applications. However, in most cases, the cost of the ceramic components is very high. On some occasions, the final machining of the component (especially if complex geometries are to be obtained) accounts for an important percentage of the final cost. The electrodischarge machining process can be a good choice if the material has at least a minimum electrical conductivity, since it can produce very complex shapes and it is not dependent on the hardness or abrasiveness of the material itself. In this paper, the development of sinking and wire electrodischarge machining technology for two ceramics with a promising future (boron carbide and silicon infiltrated silicon carbide) is described. The high removal rates, as well as the possibility of obtaining an excellent surface finish, prove the feasibility of the industrial application of this production method.

Surface modification of SKD 61 during EDM with metal powder in the dielectric

Abstract: This study investigates the influence of process parameters of electrical discharge machining (EDM) on machining performances with the addition of Al and Cr powder into kerosene. In addition, the effects of powder addition on surface fine-finish and modification are also discussed. The machining process parameters of this empirical investigation included peak current, pulse duration, as well as the type of powder added, its grain size, and mixing ratio. The machining performance, characterized by material removal rate (MRR), electrode wear rate (EWR) and surface roughness, was monitored as a function of process variables. Moreover, surface modifications were also explored thoroughly. The experimental results demonstrate that addition of Al and Cr powders into the dielectric enlarges the gap distance and divides discharge current, which promotes better EDM performance. Restated, adding a mixture of Al and Cr powders into dielectric yields the best results. Moreover, during EDM, the added powder migrates and penetrates the machined surface. Test results reveal that the corrosion resistance and surface hardness was improved by adding the proper powder into dielectric.

Influence of electrical discharge machining on the sliding contact response of cemented carbides

Abstract: The correlation between electrical-discharge machining (EDM) and surface integrity and its influence on the sliding contact response of a fine-grained WC-10% wt Co hardmetal have been studied. Different surface finish conditions were evaluated corresponding to sequential EDM as well as grinding and polishing employing diamond as abrasive. Surface integrity was characterized in detail for all conditions through scanning electron microscopy (SEM). Sliding contact response was determined through microscratch measurements using a nanoindentation system. Contrary to the results obtained from conventional hardness evaluation, the above testing technique allows discrimination of EDM effects on the contact behavior of the studied cemented carbide. The experimental results, given in terms of scratch penetration-load curves and friction coefficient, indicate that microscratch resistance increases with finer-executed EDM, up to values similar to those exhibited by the reference ground and polished condition. The findings are discussed in terms of contact damage features as related to surface integrity and intrinsic microstructural features.

Micro-hole Maching of Copper Using the Electro-discharge Machining Process with a Tungsten Carbide Electrode Compared with a Copper Electrode

Abstract: This paper describes micro-hole machining of a copper plate using the electro-discharge machining (EDM) process. Tungsten carbide was selected as the material for the electrode and compared with a copper-electrode. A precision centreless grinding process was employed to grind the electrode down to the desired diameter. A series of experiments were performed on a traditional EDM machine to investigate the effects of electrode material polarity setting and of a rotating electrode. Results have shown that electrode wear and hole enlargement are both smaller when positive polarity machining is selected; whereas electrode wear is larger and machining speed is higher when negative polarity machining is selected. High-quality micro-hole machining in copper can be achieved by the proposed method.

Laser machining method, laser machining apparatus, and its control method

Abstract: This is to present a laser machining method and a laser machining apparatus for drilling holes, capable of achieving conduction securely between adjacent conductive layers, by detecting the machining state of a workpiece adequately, and controlling the machining For this purpose, the number of laser pulse outputs capable of machining securely is preset During laser machining, reflected laser beam intensity from the workpiece and incident laser beam intensity are detected, and the machining state of the workpiece is detected As a result, when judging the workpiece has reached a desired machining state, laser machining is finished if the number of times of laser machining has not reached the set number of laser pulse outputs If it is judged that the workpiece has not reached the desired machining state, laser machining is finished when reaching the set number of laser pulse outputs As a result, the laser machining method and laser machining apparatus capable of drilling holes of high quality at high yield and shortening the machining cycle time can be realized

The Potential of Plating Techniques in the Development of Rapid EDM Tooling

Abstract: Electrodischarge machining (EDM) is a widely used process in the manufacturing of mould cavities for plastic products. EDM work typically accounts for a large portion of overall production time. A major cost and time element of EDM is electrode production, which can account for more than 50% of the total machining costs. A large complex electrode profile, which is very difficult to produce through machining and is also time consuming, can be easily produced using the rapid prototyping (RP) technique. The direct laser sintering of metal powders is a widely established RP process that can be employed for the rapid production of EDM electrodes. In this study, the above-mentioned technique has been employed. The powder mixture used in this process consists of copper, tin, nickel and phosphorus. An infra-red (IR) 200 W CO 2 laser is used to sinter the powdered metals layer-by-layer in order to form solid electrodes. Electroless copper and copper plating are then employed to improve the surface finishing and the conductivity of the sintered electrode as it deposits a uniform thickness of metal onto the substrate by chemical reaction, without building up at the edges and corners, and achieves unique physical characteristics. The performance of the newly developed electrode is very similar to that of conventional copper electrodes. It is found that integration of RP and electroless plating techniques can be a potential means of the rapid production of EDM electrodes at low cost.

FABRICATION AND CHARACTERIZATION OF Cu-SiCp COMPOSITES FOR ELECTRICAL DISCHARGE MACHINING APPLICATIONS

Abstract: Cu-SiCp composites made by the powder metallurgy method were investigated. To avoid the adverse effect of Cu-SiCp reaction, sintering was controlled at a reaction temperature less than 1032 K. Electroless plating was employed to deposit a copper film on SiCp powder before mixing with Cu powder in order to improve the bonding status between Cu and SiC particles during sintering. It was found that a continuous copper film could be deposited on SiCp by electroless copper plating, and a uniform distribution of SiCp in Cu matrix could be achieved after the sintering and extrusion process. The mechanical properties of Cu-SiCp composites with SiCp contents from 0.6 to 10 wt% were improved evidently, whereas electrical properties remained almost unchanged as compared with that of the pure copper counterpart. In the electrical discharge machining (EDM) test, the as-formed composite electrodes exhibited a character of lower electrode wear ratio, justifying its usage. The optimum conditions for EDM were Cu–2 wt% SiC...