Showing papers on "Electrical discharge machining published in 1995"

Determination of optimal cutting parameters in wire electrical discharge machining

Abstract: Owing to the complexity of wire electrical discharge machining (wire-EDM), it is very difficult to determine optimal cutting parameters for improving cutting performance. The paper utilizes a feedforward neural network to associate the cutting parameters with the cutting performance. A simulated annealing (SA) algorithm is then applied to the neural network for solving the optimal cutting parameters based on a performance index within the allowable working conditions. Experimental results have shown that the cutting performance of wire-EDM can be greatly enhanced using this new approach.

Surface Generation Mechanism in Electrical Discharge Machining with Silicon Powder Mixed Fluid(共著)

Abstract: The surface generated by electrical discharge machining (EDM) appears to be generally mat. However, the machined surface in EDM with silicon powder mixed fluid becomes glossier and has a smaller surface roughness than that in conventional EDM with kerosine type fluid, which leads to the omission of finish hand lapping of metal mold. The quality of machined surface significantly depends on the kind of workpiece material, but the surface generation mechanism has not yet been made clear sufficiently.In this study, the effect of silicon powder mixing on the surface generation mechanism is experimentally investigated, analyzing the shape of crater generated by a single pulse discharge, the surface roughness, the machined surface and so on. Main conclusions obtained are as follows:(1) The gap distance in EDM with silicon powder mixed fluid is larger than that with kerosine type fluid, because of the lower resistivity of the former and the influence of silicon powder arrangement in the gap.(2) EDM with silicon powder mixed fluid leads to smaller undulation of a crater, because of the smaller impact force acting on the workpiece due to evaporation and expansion of machining fluid.(3) The more the precipitated carbides in the workpiece are, the larger the surface roughness is, since the carbides come off because of crack propagation due to the frequent heat impact during EDM.(4) EDM with silicon powder mixed fluid results in the stable machining without short circuit between the electrode and the workpiece.

Surface Generation Mechanism in Electrical Discharge Machining with Silicon Powder Mixed Fluid

Abstract: The surface generated by electrical discharge machining (EDM) appears to be generally mat. However, the machined surface in EDM with silicon powder mixed fluid becomes glossier and has a smaller surface roughness than that in conventional EDM with kerosine type fluid, which leads to the omission of finish hand lapping of metal mold. The quality of machined surface significantly depends on the kind of workpiece material, but the surface generation mechanism has not yet been made clear sufficiently.In this study, the effect of silicon powder mixing on the surface generation mechanism is experimentally investigated, analyzing the shape of crater generated by a single pulse discharge, the surface roughness, the machined surface and so on. Main conclusions obtained are as follows:(1) The gap distance in EDM with silicon powder mixed fluid is larger than that with kerosine type fluid, because of the lower resistivity of the former and the influence of silicon powder arrangement in the gap.(2) EDM with silicon powder mixed fluid leads to smaller undulation of a crater, because of the smaller impact force acting on the workpiece due to evaporation and expansion of machining fluid.(3) The more the precipitated carbides in the workpiece are, the larger the surface roughness is, since the carbides come off because of crack propagation due to the frequent heat impact during EDM.(4) EDM with silicon powder mixed fluid results in the stable machining without short circuit between the electrode and the workpiece.

Electrode for electric discharge machining, and metal surface treating method by electric discharge

Abstract: PURPOSE: To eliminate the breakableness of a green compact electrode and also apply secondary machining to an article to be treated through only changing an electric discharge electric condition, by forming an electric discharge electrode with compression-molding carbide such as WC and Ti, boride such as TiB2 and ZrB2, and nitride such as TiN and ZrN to perform temporary sintering at a temperature of sintering temperature or lower to form an electrode for electric discharge machining. CONSTITUTION: A simple substance or a mixture of two or more kinds, cited below, is compression-molded; carbide such as WC, TiC, TaC, ZrC, SiC, and VC; boride such as TiB2 and ZrB2, and nitride such as TiN and ZrN. Then, the compression molded body is temporarily sintered at a temperature of sintering temperature or lower to form an electric discharge electrode. In this electrode, the hardness of a surface layer is increased when machining is made by a plus electrode than by a minus electrode. This reason is estimated because of the fact that the electrode 1 in plus causes an article to be treated into minus to increase an electrode discharge trace current density to obtain the resulted article to be treated reheated at a high sintering temperature. Resultingly the breakableness of the electrode 1 is eliminated even in electric discharge machining having nonconsumptiveness. COPYRIGHT: (C)1996,JPO

Curved electrode and method for electrical discharge machining curved cooling holes

Abstract: An electrode for use in a rotary electrical discharge machining (EDM) device for producing at least one curved hole in an article includes at least one curved tooth. The curved tooth lies in a plane. A perpendicular line to that plane is parallel to the axis of rotation on the rotary EDM device. At least one curved cooling hole is machined in the article.

Method for making an electrode for electrical discharge machining by use of a stereolithography model

Abstract: The present invention provides an improved method for rapidly making an electrode for electrical discharge machining. According to the invention, a stereolithography process is used to make a cured resin model of the electrode and having a network of interconnected supporting members defining the shape of the electrode and leaving channels between the supporting members to drain away uncured resin from the model. After the model is fully cured and the uncured resin drained away, a slurry mixture of graphite and resin is infiltrated into the voids of the model. The resin is then heat cured so that the resin is burned away leaving the electrode of pure carbon. Alternatively, the graphite and resin mixture can be cured sufficiently to harden and then an electrically conductive metalized coating is applied on the outer surface.

Direct Synthesis and Sintering of Silicon Nitridenitanium Nitride Composite

Abstract: Electrical discharge machining is an attractive machining technique which requires electrically conductive ceramic materials. Silicon nitride based composites with 35–40% of TiN possess electrical conductivity high enough to use this machining technique. The composite powder was prepared by combustion synthesis and densified by pressure sintering (sintering aids 6 wt% of Y2O3 and 4 wt% of A1,03). High fracture toughness, Kc 10.5 MPa.m1/2, is typical for the composite. It can be expected that this material can compete with pure silicon nitride in applications requiring complex machining.

Wire-cut electric discharge machining apparatus and control method therefor

Abstract: A wire-cut electric discharge machining apparatus and a control method for the wire-cut EDM apparatus. The amount of current pulses supplied to a machining gap can be measured precisely without a detection delay to thereby detect the occurrence of faulty machining such as wire electrode breakage and centralized arcs.

Manufacturing linear and circular contours using CNC EDM and frame type tools

Abstract: In traditional electro discharge machining (EDM) the usual practice is to form a 3D female cavity in the work piece by making a corresponding male shaped tool and plunging this into the work piece. Recently, however, computer numerical control (CNC) EDM machines have become available which have the potential to generate a detailed shape without using complex electrodes. This paper describes a novel method of electro discharge machining which makes the generation of linear, circular and curved contours possible without any special electrodes. The experimental work employs CNC EDM, mild steel work pieces and inexpensive “frame type” copper tools. The results indicate, relative to the cavities produced, an improved effective material removal rate (MRR), a better surface finish and a lower powered machine. The paper also introduces the effect of EDM parameters on the process performance by modelling and analysing the experimental results using statistical techniques. Finally, a few applications are discussed.

Fabrication of titanium implant-retained restorations with nontraditional machining techniques.

Abstract: Traditional laboratory techniques are being supplemented by modern precision technologies to solve complex restorative problems. Electrical discharge machining combined with laser scanning and computer aided design-computer aided manufacturing can create very precise restorations without the lost wax method. A laser scanner is used to create a three-dimensional polyline data model that can then be converted into a stereolithography file format for output to a stereolithography apparatus or other rapid prototyping device. A stereolithography-generated model is used to create an electric discharge machining electrode via copper electroforming. This electrode is used to machine dental restorations from an ingot of titanium, bypassing the conventional lost wax casting process. Retaining screw access holes are machined using conventional drilling procedures, but could be accomplished with electric discharge machining if desired. Other rapid prototyping technologies are briefly discussed.

Fabrication of Surface Modification Layer on Stainless Steel by Electrical Discharge Machining

Abstract: A stainless steel (SUS 304) was machined by Electrical Discharge Machining (EDM) with a sialon and chromium electrode. According to the EDMed conditions, the deformed stainless steel surface turned to the coated surface with an electrode components. The following experimental factors were investigated to produce the modified surface: electrode polarity, work atmosphere, peak current, pulse duration and duty factor. In the suitable worked conditions, the modified layer had good corrosion and wear resistance.

Method and apparatus for electrical discharge machining using variable capacitance and variable inductance

Abstract: An electric discharge machine having a source of pulse power, optionally including bipolar pulses, which is connected to an electrode which forms a gap with a workpiece and is operative to provide both machining and finishing processes. Switching of power to the machining gap and impedance matching at the machining gap, in order to suppress the influence of the capacitance of the high-speed machining feeder cables connected to the machining gap in finishing, is provided so that machining can be performed at high accuracy with a properly timed and shaped discharge current. Impedance matching is provided by selectively switching among plural capacitances or inductances, which may be in the form of cables or printed patterns on a circuit board which have predetermined values, such as a geometric series values of which coefficient is 2.

Method and device for surface processing by electric discharge machining

Abstract: PROBLEM TO BE SOLVED: To form a hard and dense surface treatment layer easily by generating chemical reaction between a metal electrode substance and carbon in a processing liquid by a thermal action of electric discharge machining, and forming a reforming layer of metal carbide on a surface of a work to be processed. SOLUTION: A locus movement control device 12 controls transverse movement of a surface treatment electrode 2 on the basis of electrode pass information prepared by a CAM 13 for producing locus of electrode motion. During the processing, Ti as electrode material is put afloat in processing fluid by thermal energy generated by electric discharge and attached to a surface of a work to be processed 1. At the same time, C (carbon) in the processing fluid 3 is decomposed by the thermal energy of electric discharge and separated from the processing liquid. Carbide of Ti is formed by chemical reaction between a decomposed carbon and Ti in the fluid and on the surface of the work 1, and a hard film is formed on the surface of the work 1.

Surface layer forming process using electric discharge machining

Abstract: An apparatus and process for forming surface layers on electrodes by electron discharge machining. A machining gap, between an electrode and a workpiece is filled with a dielectric mixture containing metallic or submetallic powder. The apparatus uses a swinging mechanism to move the electrode during processing. The apparatus uses a high-voltage superposition circuit to superpose a voltage of 100-400 V across the gap. The apparatus uses a current limiting resistor of 100-300 Ω to ensure that the main circuit supplies a low voltage of approximately 100 V to the machining gap. In a second embodiment, the apparatus prevents electrode cracking by dispersing the discharges throughout, and widening, the machining gap.

Wire electrode for electro-discharge machining and method of manufacturing same

Abstract: A process of manufacturing spark erosion electrode particularly pertaining to electrode in wire form, for use in electrical discharge machining, the core of the electrode being of comparatively low zinc alpha brass with top layer of highly rich zinc beta and gama brass to facilitate better flashability of the electro-erosion process, and also to achieve comparatively higher tensile strength of the core material of the electrode, whereby relatively higher accurate vertical cut of the workpiece is possible, due to reduction of amplitude of high tension vibration of the core while cutting workpiece by electro discharge machining process (hereinafter referred to as EDM process).

High aspect ratio EDM electrode assembly

Abstract: An electrode assembly for electrical discharge machining (EDM) a slot in a wall includes a plurality of laterally abutting individual electrodes having a collective perimeter configuration complementary with the slot. The electrodes define a collective height equal to the sum of their individual heights which may be substantially greater than the individual widths thereof for machining a correspondingly high aspect ratio slot in the wall.

Combined machining of USM and EDM for advanced ceramics

Abstract: A combination of two or more machining processes may result in an increase in the productivity in the machining of so-called difficult-to-machine materials. In this paper, ultrasonic machining is combined with electrical discharge machining. This combined machining technigue can be applied to machine all conductive hard and brittle materials with high efficiency and surface integrity. The principle of this combined machining process, which combines the advantages of ultrasonic machining and electrical discharge machining, is described. This paper deals with the experimental study of the effect of this combined machining process on material removal rate. It is confirmed through the experiments that this new machining process is effective in attaining high material removal rates

The Production of Electrical Discharge Machining Electrodes Using SLS: Preliminary Results

Abstract: Electrical discharge machining (EDM) has become common place in the tool and die industry as an alternative to conventional machining and now accounts for 2% ofworldwide machining l , with a substantially greater concentration ofuse in the tool making industry.EDM has the advantage of allowing tool steel billets to be heat treated to full hardness before the cavity is produced, obviating the need for heat treatment after machining--a step that often results in the loss of dimensional accuracy due to distortion in the quenching from high temperature austenite to martensite at room temperature. Any material with less than 1 ohm-m ofelectrical resistivity, regardless ofhardness, can be machined using EDM. 1 EDM also allows the convenient production of complex shapes in the tool cavity, as complex topographies can often be more easily machined on the electrode than inside a cavity. Even certain simple shapes such as rectangular or square cavities are far easier to produce using EDM than conventional machining.

Wire-cut electrical discharge machine and method which automatically calculates the shape, number and arrangement of bridging members

Abstract: A method and apparatus for wire-cut electrical discharge machining which allows bridging members for securing a core to a workpiece after cutting to be fitted, without interference with adjacent cores, to ensure efficient machining when multiple cores are to be removed from a single workpiece. The disclosed procedure permits machining which can automatically avoid interference of bridging members with an upper nozzle and can automatically perform efficient machining up to finishing.

Study on mechanical pulse electric discharge machining

Abstract: In this paper, a mechanical pulse electric discharge machining (MPEDM) technique has been developed to produce holes in the conductive hard and brittle materials, and the mechanism of the MPEDM is described. The sparks of electric discharge in the MPEDM are caused by the ultrasonic vibration of the tool, which is used in place of the conventional special pulse generator. Ultrasonic vibration of the tool also acts as a gap-flushing method. Tap water is used as the working fluid in the MPEDM technique. It has been confirmed through the experiments that the MPEDM is effective to attain a higher material removal rate (MRR) for conductive difficult-to-machine materials.

Wire electric discharge machining method at a corner

Abstract: A wire electric discharge machining method capable of improving a machining accuracy of a corner portion. A machining feed speed is gradually reduced from a point A before entering a corner portion machining between points C and D, and in the corner portion between points C and D the machining is performed at a fixed feed speed. The feed speed is gradually increased from the point D, where the machining of the corner portion is completed, and is restored to the original speed. In accordance with the change of the feed speed, an off-state time of the voltage applied between a wire and a workpiece is increased from a point B and is reduced from a point E after completing the corner portion machining, to restore the original off-state time at a point F. Further, a flow rate of machining fluid is reduced depending on the corner portion. The feed speed, the off-state time and the flow rate of the machining fluid are controlled by automatically changing them in dependence on a curvature of the corner portion. A warp of the wire electrode is substantially prevented at the beginning of and during the corner portion machining, to thereby improve the machining accuracy of the corner portion.

Geometric Modeling of Manufacturing Processes Using Symbolic and Computational Conjugate Geometry

Abstract: The present paper describes a unified symbolic model of conjugate geometry. This model can be used to study the geometry of a cutting tool and the surface generated by it on a blank along with the kinematic relationships between the tool and the blank. A symbolic algorithm for modeling a variety of shape generating processes has been developed. It has been shown that using this algorithm one can develop geometric models for conventional machining processes such as milling, turning, etc. as well as unconventional or advanced machining techniques such as Electric Discharge Machining (EDM), Laser Beam Machining (LBM) etc. The proposed symbolic algorithm has been implemented using the symbolic manipulation software, MACSYMA. The algorithm is based on the concepts of envelope theory and conjugate geometry of a pair of mutually enveloping surfaces. A case study on the manufacture of a helicoidal surface and an illustrative example are given at the end of the paper.

Single Discharging Force and Machining Volume of Wire EDM

Abstract: Cutting previsions of Wire-EDM are spoiled by a wire vibration and a wire deflection during the machining. In some previous reports, wire behaviors were measured and discussed.As well known, the wire behavior is affected from a explosive force, a electrostatic force, a electromagnetic force by each discharging and a force caused by flushing of water.Especially in these forces, the explosive force by each discharging is the most important and fundamental force. But the strength of the force and the relation between the force and EDM conditions were not cleared in these reports.In this report we investigate about forces affecting on the wire behavior during Wire-EDM. These forces are obtained from wire deflections which are detected by a developed optical fiber slit system. The influence of the flushing pressure and the electrostatic force on wire deflections are discussed, and the strength of the explosive force by each discharging and a machined volume of workpiece by each discharging are obtained.

Methods and apparatus for making honeycomb extrusion dies

Abstract: A steel honeycomb extrusion die having an array of feedholes extending into a die inlet face and intersecting with an array of discharge slots on the die discharge face is made by a process wherein the slots are cut into blind feedholes by wire EDM slotting while dielectric fluid is provided in or flushed through the feedholes. The resulting improvements in EDM process stability reduce the number of wire electrodes broken during machining of the array, and in feedhole/slot intersection configuration and finish, provide dies with improved extrusion performance and extended service life.