Showing papers on "Electrical discharge machining published in 1996"

Mechanism of material removal in electrical discharge diamond grinding

Abstract: The paper presents the mechanism of material removal in electrical discharge diamond grinding, which integrates electrical discharge machining and diamond grinding for machining electrically conducting hard materials. The role of current and wheel speed on the material removal rate, the grinding forces and power is studied to elucidate the issue. The spark discharges thermally soften the work material in the grinding zone, and consequently decrease the normal force and the grinding power. The improved grinding performance is due to continuous, in-process dressing and declogging of the wheel surface.

Using rapid prototyping to produce electrical discharge machining electrodes

Abstract: Presents the background to and efforts being made to find a direct production route using rapid prototype (RP) parts as the electrodes for electrical discharge machining (EDM). It would have the double effect of unlocking the potential of the EDM die sinking process and expanding the role of RP in the production environment. Thin coated stereolithography (SL) models have been used to erode hardened tool steel to a depth of 4mm. Machining efficiency of these copper coated RP models is not comparable to that of conventional machined solid copper electrodes. Parametric optimization has been applied, achieving substantial improvements in machining efficiency. At present these electrodes are suitable for semi‐roughing or finishing cuts in EDM die sinking. Electroforming copper into SL cavities shows potential for manufacture of electrodes with comparable performance to that of solid copper.

The temperature of a plasma used in electrical discharge machining

Abstract: The temperature in an electrical discharge machining (EDM) plasma was determined from measurements of relative intensities of the 411.85 and 413.29 nm Fe I spectral lines. The time-dependence of the plasma temperature was measured for individual electrical machining pulses. Under our experimental conditions (electrodes of C6(+) and M1E(-), cosmetic paraffin as the dielectric liquid) the measured plasma temperature ranged from 8000 to 10 000 K for different current pulses. We observed higher temperature values during the initial phase of the discharge. Temporal characteristics of discharge electric parameters, light emission and the plasma temperature are presented.

Microelectro discharge machining as a technology in micromachining

Abstract: In recent years, machine facilities for Electro Discharge Machining (EDM) have been dramatically improved. Enormous progress has been obtained with respect to form accuracy and structure precision even in the submicron domain, which qualifies EDM as a technology for microfabrication ((mu) EDM). (Mu) EDM therefore extends the family of existing microtechniques e.g. the LIGA process or silicon surface micromachining. The EDM-technology offers 3D microfabrication of conductive materials independent of their mechanical properties like hardness, brittleness, etc. This capability offers new fields of application for the microfabrication of components made e.g. from stainless steel or titanium. In order to demonstrate the successful application of various (mu) EDM processes components and devices like micro gearwheels, microreactors, micro punching tools and mould inserts for micro injection molding of an optical fiber connector are presented, which have been fabricated by EDM in close cooperation between the Institute of Microtechnology Mainz GmbH and the Swiss EDM-manufacturer AGIE Losone. Based on their know-how the partners aim to optimize (mu) EDM for microfabrication purposes.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Current problems and future directions for ceramic machining

Abstract: Monolithic ceramics, such as silicon nitride, silicon carbide, aluminum nitride, zirconia, and alumina; particulate- and whisker-reinforced ceramic-matrix composites; and ceramic coatings pose difficulties in machining. Because of the high hardness and low toughness of these materials, diamond grinding is often the method of choice in machining. One advantage of grinding is that machine tools are readily available for ceramic grinding at almost all machining and manufacturing companies, irrespective of their size.

An Examination of Wire Electrical Discharge Machining (WEDM) of Al2O3 Particulate Reinforced Aluminum Based Composites

Abstract: The material removal mechanism in wire electrical discharge machining of an alumina particulate reinforced aluminum based composite and the related machined surface morphologies were investigated. Under the two cutting conditions of this study, fine and coarse cuttings, the surface roughness measurements on the machined surfaces of the composite material did not show a significant difference, but their corresponding surface topographies were found to be intrinsically different. Besides, surface bandings were observed on the machined surfaces of some fine cut specimens and was believed to be caused by shifting of the wire. Based on these observations and the measured profiles, a material removal scheme for the two cutting conditions was proposed.

Three-dimensional electrical discharge machining method and apparatus utilizing NC control

Abstract: To obtain high machining speed and machining accuracy in three-dimensional machining by using of an electrode of simple shape. Applying voltage between an electrode of simple shape and a workpiece, performing three-dimensional control by an NC control while synthesizing a feed of a Z-axis direction for correcting longitudinal consumed amount of an electrode with an X-Y plane feed, storing amount equivalent to an X-Y moving distance in an X-Y plane corresponding to correcting moving amount of the Z-axis direction in an electrical discharge machining method for machining a desired three-dimensional shape and performing a feed of correcting moving amount in the Z-axis direction each time a moving distance in the X-Y plane on a moving locus during machining reaches the above stored amount.

Electrical Discharge Machining of ZrB2 -Based Ceramics

Abstract: The objective of this study is to investigate the possibility of fabricating ZrB2-based materials using wire-cutting and die-sinking electrical discharge machines. Compared to diamond saw machining, which machined ZrB2-based materials at a relatively low rate, electrical discharge machining is very attractive. Based on the experimental results under different machining conditions, the higher the energy input, the higher will be the material removal rate. ZrB2-Cu is difficult to machine due to partial surface oxidation, which was confirmed by x-ray diffraction and microprobe analysis. The extremely low workpiece removal rate makes ZrB2-Cu appealing for machine tool use.

Monitoring and self-learning fuzzy control for wire rupture prevention in wire electrical discharge machining

Abstract: Wire breaking is a serious problem in the application of wire electrical discharge machining (WEDM). A WEDM sparking frequency monitoring and control system based on the characteristics of the voltage waveform of WEDM is developed. A new self-learning fuzzy controller is proposed to control the sparking frequency at a safe level by regulating the pulse off-time in real time for avoiding wire rupture and maintaining a state of high metal removal rate. The developed control strategy is tested under the conditions of cutting a workpiece with continuous sharp angles, a change in workpiece height during machining process, and machining with a high feed-rate. Experimental results show that this monitoring and control system can control the sparking frequency at a predetermined level without the risk of wire rupture.

Wire electrode and process for producing a wire electrode, particular for a spark erosion process

Abstract: In order to produce a wire electrode having a core consisting of a copper/zinc alloy and to produce a specific sheath layer, the sheath layer is coated onto the core at a temperature at which no diffusion occurs. The wire electrode is subsequently heated at a heating speed higher than 10° C. per second, briefly annealed at temperatures above 500° C. and subsequently cooled again very rapidly at cooling speeds higher than 10° C. per second.

Cutting method and device of semiconductor ingot for epitaxial wafer semiconductor

Abstract: PROBLEM TO BE SOLVED: To reduce a cutting margin to reduce the cutting time by applying a voltage between each wire and a semiconductor ingot for every wire of wire electrode to thereby generate electric discharge, resulting in cutting of the ingot into several pieces. SOLUTION: A wire electrode 9 is wound around between a guide roller 4, 5 through an aligning roller 13 and moves along a guide groove in order to reach a take-up reel 14, and a plurality of wires of wire electrode 9 are formed in parallel between the roller 4, 5. A d.c. power source voltage is applied between each wire of the electrode 9 and a semiconductor ingot 7, then the ingot 7 mounted on a work table 6 is raised, and the ingot 7 is cut into several pieces with a specified thickness by electric discharge machining.

Electric discharge machine

Abstract: An electric discharge machine using a machining liquid both for cooling an electric discharge machining region and removing chips from the electric discharge machining region and for lubricating hydrostatic bearings included in guide mechanisms of a machine unit, and having a fluid circuits and a machining liquid processing unit A pressurizing liquid processing unit having a pump (42) and a machining liquid filter (43) pressurizes and filters the machining liquid The pressurized and filtered machining liquid is supplied through lubrication-purpose machining liquid supply lines (53 to 56) to the hydrostatic bearings (59) of the hydrostatic guide mechanisms, and through a machining-purpose machining liquid supply line (53) to the electric discharge machining region in which an electric discharge machining electrode (30) processes the work (32) The same electric discharge machining liquid is used both for lubricating the guide mechanisms and for cooling the electric discharge machining region and removing chips from the electric discharge machining region

Properties of compacted, pre-sintered and fully sintered electrodes produced by powder metallurgy for electrical discharge machining

Abstract: The performance of electrodes is an important aspect in electrical discharge machining (EDM). For any particular set of working conditions, the tool electrode performance is mainly determined by the electrical, thermal, physical and mechanical properties of the electrode material. Although an ideal material that can function as a perfect electrode does not exist, powder metallurgy provides a means of combining the desirable characteristics of different materials. In this process, powder char- acteristics, interaction between powder and compacting die as well as sintering conditions are deci- sive factors. Dependence of the physical, electrical and thermo-mechanical of the com- pacts on the conditions used during powder metallurgy processing of the electrodes for EDM has been investigated. Electrical discharge machining (EDM) is an im- perties which, to some extent are mutually incom- portant process for manufacturing die and mould patible, namely high electrical conductivity and which is based on the controlled erosion of mate- specific heat, good machinability and high erosion rial by 'discrete electric discharges between tool resistance7. It is clear that none of the materials and workpiece submerged in a dielectric medium. singly can meet these diverse requirements. How- It employs high frequency electric pulses for ma- ever, the powder metallurgy route enables combi- chining electrically conducting materials which are nation of desirable properties of different materi- otherwise difficult to machine due to their ex- also Due to the extreme flexibility in composition treme hardness. During this process, shape of the control of elecrode material and ease of fabrica- tool is accurately replicated on the workpiece. tion, powder metallurgy technique promises defi- The provision of computer control coupled with nite advantages as a method for EDM tool fabri- advances in EDM controller units has led to the cation. Research has been carried out recently to development of CNC EDM1. In spite of the deve- investigate possibilities of tool electrode material lopments in hardware and technology, basic re- transfer on to material surface using P/M elec- search on erosion mechanisms and the associated trodes and this was found to occur under specific phenomena is still lagging behind. Scarcity of suit- conditions8. The present work aims at a more de- able tool electrodes is one of the important prob- tailed study in terms of the conditions of manu- lems in EDM-die sinking. Since its introduction in facture of P/M electrode to understand their 1946, several researchers have attempted to cor- probable behaviour in actual EDM. relate the performance of electrical discharge ma- chining with the properties of tool electrodes2-6. Experimental Procedure An exhaustive study has been conducted on the P/M electrodes for electrical discharge machip- mechanism of electrical discharge machining ~d ing were prepared under different compacting and it is found that both tool and work materials play sintering conditions and their properties were a significant role in electrical discharge machin- evaluated. The basic material used was electrolyt- ing5. The machining performance is controlled by ic copper powder with apparent density 2.9 g several physical properties of the electrodes and cm-3 and with rate 40 s/50 g. The chemical pur- their relative importance on it depends on the ity of the powder was estimated as 99.7% with machining set-up employed. An ideal tool elec- 0.03% acid insoluble contents (ASTM E-194). trode in EDM should combine a number of pro- The particle size distribution is shown in Fig. 1. The average size of the particles was around 75 .Author to whom correspondence should be addressed. ,urn. Microscopic examination of crushed powders

Development of process technology in wire-cut operation for improving machining quality

Abstract: Many of the quality problems have their origin either in the product design or process design. The statistical design of experiments is a scientific method for optimization of design parameters. This paper highlights an application of improving process design in the metal cutting operation by the wire-cut EDM (electro discharge machining) process on a hi-tech Japax Machine. An experiment was conducted on nine process parameters as per the L16 (215) orthogonal array layout. The responses considered were precision in machined dimensions and surface roughness. The data were then analyzed for mean and signal-to-noise ratio. All the nine factors turned out to be significant in at least one of the analyses and the best operating conditions were found considering the results of different analyses. Implementation of the results showed that the dimensional variability ( 3 sigma ) is reduced from 0.015 to 0.007 and the surface roughness from 4 mu m to 2 mu m. Other benefits were increased tool life by over 10% and ...

Contouring electrical discharge machining with on-machine measuring and dressing of a cylindrical graphite electrode

Abstract: This paper presents a new approach of contouring electric discharge machining (EDM) by means of the on-machine measuring and dressing of a ball-nosed cylindrical graphite electrode. The on-machine measuring is done in order to detect electrode wear by a laser range sensor. The on-machine dressing is carried out by turning the electrode with a disk shaped cutting tool fixed in the EDM machine. Machining experiments by contouring EDM have been performed and their results are compared with those by diesinking EDM in terms of the total machining time, electrode cost and machining error. Their results support the efficiency and validity of contouring EDM.

Wire electrical discharge machining of Al2O3 particle and short fibre reinforced aluminium based composites

Abstract: The wire electrical discharge machining behaviour of alumina particle and short fibre reinforced aluminium based composites was studied. Under the two cutting conditions of this study, namely coarse and fine cutting, the average surface roughness Ra of the particle reinforced composite was found always to be higher than that of the corresponding machined matrix surfaces, however, the opposite was found to be true for the fibre reinforced composite. Comparing the surface quality of the two composites, in terms of roughness measurements, the fibre reinforced composite was superior to the particle reinforced composite. Although cutting conditions have little effect on the overall Ra of the two composites, their corresponding surface topographies were found to be intrinsically different. Surface banding was observed on the fine cut surfaces of the particle reinforced specimens, which was believed to be caused by shifting of the wire. Based on the machined surface morphology and the measured surface pr...

Genetic synthesis of a fuzzy pulse discriminator in electrical discharge machining

Abstract: In this paper, a sensor system, called a fuzzy pulse discriminator, is developed to classify various discharge pulses in electrical discharge machining (EDM). The fuzzy rules of the pulse discriminator are obtained based on the features of the gap voltage and gap current between the tool workpiece. The membership functions of the fuzzy pulse discriminator are automatically synthesized by using genetic algorithms. The effectiveness of this approach is verified under different cutting parameters.

Wire electric discharge machining method

Abstract: A wire electric discharge machining method capable of carrying out a machining in a first step and a cutting in a second step using one machining program comprising the steps of setting and inputting programs for machining routes for cutting respective male molds (A1 to A3), an accumulation alpha and a reverse amount beta , stopping an electric discharge machining so as to leave the accumulation alpha in a first machining and storing a position where the machining is stopped, and carrying out in a second step an automatic wire connection at a wire connecting position that is way back along a machining groove by the reverse amount beta from the machining stop position in the first step and cutting the respective male molds (A) by effecting electric discharge machining from the wire connecting position. A wire electric discharge machine comprises an annealing/fusing device that anneals and fuses the wire by heating the wire with a current supplied to the wire, whereby linearity is provided to a wire by annealing and a semi-spherical configuration is provided to a wire leading end by fusion, thereby making it possible for a wire to easily be introduced into the machining groove at the wire connecting position.

Internal teeth spark erosion appts.

Abstract: In an appts. for spark eroding internally toothed workpieces (as described in DE application number 4324271), the electrode is a copy of the hollow workpiece interior and has the shape of an externally toothed gear wheel which is subjected to pilgrim step oscillatory motion.

Wire cut electrical discharge machine

Abstract: A wire-cut electrical discharge machine for machining a workpiece using a wire electrode tensioned between a first and second wire guide, in a state where the gap between the wire electrode and the workpiece is filled with a machining fluid, is provided with a work tank (WT) which holds the workpiece (WP), a guide mechanism (N) which guides the movement of a first wire guide (14) in an X-Y plane formed by mutually perpendicular X and Y axes arrayed within the work tank, and a sealing member (16) which covers the guide mechanism (N) and blocks against leakage of machining fluid from the work tank (WT); the sealing member (16) is connected to a pressurized fluid supply device (401, 402, 403, A1, A2) for the purpose of supplying a pressurized fluid therein, and the pressurized fluid supply device responds to a signal from a sensor (404) mounted on the sealing member (16) which detects fluid pressure, thus regulating the pressure inside the sealing member to be the same as the external fluid pressure of the pressurized machining fluid.

Simulation of Erosions in a Single Discharge EDM Process

Abstract: A model developed for simulation of the electrical discharge machining processes was used to evaluate the importance of pulse waveforms. In a case study that involves a. single discharge, periodical variations in both the spark pressure and spark temperature resulted in predictions that will be significant in the development of future commercial electrical discharge machines. The predicted oscillation in the temperature of the spark causes a repetitive increase and decrease in the size of anode melt-cavity. The multiple melting and resolidification of the anode surface is described to be effective in growth of the new, thermally protective surface layers detected by other researchers.

Method of fabricating precise cast or noncast implant-retained dental restorations using electrical discharge machining

Abstract: A method of fabricating a precise implant-retained dental restoration from a casting or solid metal body by fabricating multiple electrodes, which are negatives of the surfaces of the desired restoration, and machining the casting or solid metal body against the electrodes by electrical discharge machining.