Showing papers on "Electrical discharge machining published in 1991"

Analysis and optimization of parameter combinations in wire electrical discharge machining

Abstract: This paper presents a formulation and solution of a multi-objective optimization problem for the selection of the best control settings on a wire electrical discharge machine. The measures of performance for the model are taken to be metal removal rate and surface finish quality. A factorial design model is used to predict the measures of performance as a function of a variety of control settings. To aid in selecting the best combination of settings the concept of a non-dominated point is introduced. The non-dominated points are related to two important complementary optimization problems. Two techniques for the computation of non-dominated points are presented—one using explicit enumeration and the other based on the principles of dynamic programming.

Experimental Investigations into Traveling Wire Electrochemical Spark Machining (TW-ECSM) of Composites

Abstract: Experiments are carried out on glass-epoxy and kevlar-epoxy composites, using sodium hydroxide (NaOH) as electrolyte. The wire and the workpiece were kept in physical contact with each other by the use of a gravity feed mechanism. The effects of voltage and concentration of the electrolyte on material removal rate, average diametral overcut, tool wear rate, and wire erosion ratio are reported

Brittle material cutting method

Abstract: In a method of cutting a workpiece of brittle material with a wire by using a machining solution containing abrasive grains, the workpiece is pushed against the wire from above, and a machining solution pooling vessel is disposed below the workpiece, to immerse the cut portion of the workpiece in the machining solution in the vessel, and an ultrasonic oscillator is provided for the machining solution pooling vessel to apply ultrasonic waves to the machining solution during machining, whereby difficulties that the machined surface is scratched or cracked by the abrasive grains, and the machining solution is deteriorated in cutting capacity are eliminated, and the machining accuracy and efficiency are improved.

Treatment for surface of metallic material

Abstract: PURPOSE: To inexpensively form a rigid coated layer with a sufficient thickness free from defects such as dimensional changes, deterioration in the hardness (strength) of a base metal and film peeling caused by holding the temp. of the whole body of the metallic materials of a base metal to a high one. CONSTITUTION: The surface of a base metal constituted of metallic materials is coated with metallic or nonmetallic materials. After that, the deposits are remelted for each minute area by pulse electric discharge machining in liq., gas or vacuum, by which the base metal and the coated materials, are diffused and mixed to form a dense coated layer on the surface of the base metal. As the coating materials, metals, alloys, nonmetallic elements, ceramics, carbides, nitrides, borides or the like are used. As the coating means for the coating materials, a thermal spraying method, an electrodepositing method, a low temp. depositing method, a discharge precipitating method using an electrode easy to consume or the like are used. As for the pulse electric discharge machining, it is executed preferably by using an electrode hard to consume as a minus electrode. The material called as a functionally gradient material in which the coating of the coating materials and pulse electric discharge machining are executed per layer and the coated layer is provided with gradient properties can also be manufactured. COPYRIGHT: (C)1993,JPO&Japio

Some characteristics of electrical discharge machining of conductive ceramics

Abstract: Recent successes on the EDM machining of ceramic materials have been quite encouraging in the area of theoretical modeling of the cutting process. However, in order to really make use of this know-how, further investigation is necessary. This paper aims to identify the mechanisms behind the EDM machining of conductive composite ceramic and to correlate the various properties with this removal process. Subsequently, a better understanding of the process can be realized and used to explain some of the phenomena resulting from the process.

Wire cut electrical-discharge machining apparatus

Abstract: An apparatus for a wire cut electrical discharge machine for preventing breakage of the wire electrode during machining, and thereby increasing machining performance Since wire electrode breakage accidents during machining are often the result of a concentration of spark discharges in the machining area, the present invention controls machining conditions to prevent wire electrode breakage by detecting any continuous generation of spark discharges in a specific zone of the machining zone and discriminating normal concentration phenomenon from a truly bias sparking condition based on the position of the detected sparks Appropriate control over the machine or machining conditions to relieve the problem may be exerted in response to a detected biased spark discharge condition A biased spark discharge condition is detected and discriminated when spark discharges continue to occur within a set bias area, defined as a predetermined area which is set around the position of a spark discharge If subsequent spark discharges are detected outside the bias area, then a non-biased state is determined and a new bias area is set Thereafter, this procedure is repeated

Modeling of Thermal Spalling During Electrical Discharge Machining of Titanium Diboride

Abstract: Erosion in electrical discharge machining has been described as occurring by melting and flushing the liquid formed. Recently, however, thermal spalling was reported as the mechanism for machining refractory materials with low thermal conductivity and high thermal expansion. The process is described in this paper by a model based on a ceramic surface exposed to a constant circular heating source which supplied a constant flux over the pulse duration. The calculations were based on TiB{sub 2} mechanical properties along a and c directions. Theoretical predictions were verified by machining hexagonal TiB{sub 2}. Large flakes of TiB{sub 2} with sizes close to grain size and maximum thickness close to the predicted values were collected, together with spherical particles of Cu and Zn eroded from cutting wire. The cutting surfaces consist of cleavage planes sometimes contaminated with Cu, Zn, and impurities from the dielectric fluid.

Electric discharge machining

Abstract: PURPOSE:To extensively improve machined surface roughness while maintaining stability of machining and machining capacity by connecting a current limiting resistance between an electric source and an interpole space and specifying a current value supplied to the interpole space CONSTITUTION:A workpiece 5 is machined by interposing a working fluid mixed with silicon powder in an interpole space 7 formed by the workpiece 5 and an electrode 4 To the interpole space 7, superimposed voltage of a main electric source 10a and an auxiliary electric source 10b, for example, high voltage of about 180-480V is supplied After electric discharge is caused as the high voltage by the auxiliary electric source 10b is supplied to the interpole space 7 as a transistor TR1 is ON, a transistor TR2 is ON, and a discharge cutter for about several musec is supplied by the electric source 10a This discharge current is decided by a limiting resistance R1 As the high voltage is applied, the interpole space 7 extends and machining is stably maintained An electric current by the auxiliary electric source 10b is limited to 10A-20A by an electric current limiting resistance R2

Surface damage in ZrB2-based composite ceramics induced by electro-discharge machining

Abstract: Electro-conductive ZrB2-based composite ceramics, containing SiC and B4C, were machined with an electro-discharge machining (EDM) process The EDMed surfaces were covered with resolidified ZrB2 layers Many open pores and surface cracks were observed on the surfaces The strength degradation of the ceramics caused by machining was evaluated by three point bending tests of the partially EDMed bending specimens The effects of pulsed current, pulse duration and duty factor on the strength and the roughness of EDMed surfaces are discussed The strength of EDMed specimens was increased with decreases in pulse current, pulse duration and duty factor The roughness of EDMed surfaces was decreased with decreases in pulse current, pulse duration and duty factor The reliability of the ceramics EDMed with the appropriate conditions was as high as that of the ceramics ground with a 400 grit diamond wheel It would be possible to use the carefully EDMed ZrB2-based composite ceramics as structural components without any additional finishing processes

Laser-chemical three-dimensonal writing of multimaterial structures for microelectromechanics

Abstract: A patterning machine capable of 5*10/sup 4/ pixel per second random access scanning has been developed as a tool for laser microchemical fabrication of three-dimensional parts. The tool is designed to implement precision laser deposition and etching reactions through a direct interface to solid modeling CAD/CAM (computer-aided design/manufacturing) software. Initial results with the three-dimensional laser patterning machine demonstrate clean etching of germanium and silicon with micrometer depth control and speeds one to two orders of magnitude faster than electric discharge machining. High material selectivity has been exploited to write buried flow channels under oxide membranes. >

Wire electric discharge machining method for machining entrance lines and apparatus therefor

Abstract: A machining method and apparatus for avoiding the double machining by a wire electrode (1) of the same point on the desired contour of a workpiece (2), particularly the point where a predetermined entrance line intersects with the desired contour. The predetermined entrance line locus is automatically modified on the basis of the parameters of the workpiece (2) and electrode (1) such that at least a portion of the modified entrance line locus intersects the desired contour at an obtuse angle or a tangent, that portion of the modified locus being a curve or a straight line. The return locus from the desired contour to the entrance line also may be modified in addition or instead of the entrance line. The electrical parameters of the machining may further be monitored and modified in order to avoid intrusions of the desired contour.

Electric discharge machining device

Abstract: PURPOSE:To reduce bad influence or irregular electric discharging by suppressing generation of electric discharge at side faces and the secondary discharge through the splashing powder from machining likely to occur when the discharge machining involves instability. CONSTITUTION:A switching element 7 and a capacitor 3 are connected in series to a DC power supply 1, and a current suppressing resistance 6 is connected in parallel with this switching element 7 while a machining electrode 4 and a work to be processed 5 are connected with the capacitor 3. The switching element 7 is turned off with the off signal prepared by a switch control circuit according to eventual instability of electric discharge, and the charging current to the capacitor 3 is lessened by the resistance 6. When machining becomes unstable, the charging current from the capacitor 3 to the machining electrode 4 and the work 5, i.e., supply energy, is decreased so as to suppress generation of electric discharge phenomenon.

Workpiece processing functions, monitoring esp. for spark erosion machine - using multiple window screens showing functions and setting values in separate screens

Abstract: The method monitors and plans workpiece machining functions by displaying individual functions in a window of a display screen, selecting one or more functions and setting values for them in a further window. Only functions to be performed are released for selection. Functions which can be performed and those which cannot are characterised differently. The setting of the function values is monitored in a sketching window associated with the further window. USE/ADVANTAGE - Esp. for spark erosion machine, improved dialogue is achieved between user and machine.

Wire electric discharge machining device

Abstract: PURPOSE:To restrain consumption of a feeding element and to stabilize electric discharge machining by restraining electric discharge between a wire electrode and the feeding element. CONSTITUTION:A wire electrode pressing guide 19 is provided in the neighborhood of a feeding element 9a, and a wire electrode 3 is sufficiently pressed on the feeding element 9a by this wire electrode pressing guide 19. Consequently, oscillation of the wire electrode 3 is restrained, and electric discharge between the wire electrode 3 and the feeding element 9a is restrained. Additionally, imperfect contact between the wire electrode 3 and the feeding element 9a is detected by a detection circuit 21, electric discharge energy of a machining power source 17 is restrained and electric discharge by oscillation is restrained. Furthermore, breaking of wire is quickly detected by recognizing a sudden decrease of tensile force at the time of breaking of wire and electric supply is stopped, and damage of the feeding elements 9a, 9b due to breaking of wire electric discharge is reduced.

Target for sputtering

Abstract: PURPOSE: To improve the cladding properties by welding of a target alloy by adding a specified small, amt. of B to a sputtering target for a Cr-Pt-Co magnetic alloy. CONSTITUTION: As a magnetic material, a Co-Cr-Pt-B alloy having a compsn. constituted of, by weight, 5 to 20% Cr, 10 to 55% Pt, 0.001 to 0.5% B and the balance Co is melted in vacuum or in an atmosphere of inert gas or reducing gas and is cast into a mold having heat resistance, and after that, the alloy ingot is subjected to cutting to form its shape into a prescribed one by wire cutting, electric discharge machining or the like, is thereafter sintered by hot isostatic pressing, is furthermore annealed and is thereafter rolled into a sintered alloy body having a prescribed thickness. This sintered alloy body is subjected to heat treatment at about 1000°C for 1hr to remove strains in the sintered alloy body, is subjected to machining or the like to straighten its shape and is subjected to specular finishing into a target. Owing to the presence of a trace amt. of B, the objective Co-Cr-Pt alloy target excellent in cladding properties by welding can be obtd. COPYRIGHT: (C)1993,JPO&Japio

Jump control system for an electric discharge machine

Abstract: A jump control system for an electric discharge machine for controlling a jump of the electrical discharge machine. A discharge state is estimated from a discharge voltage (Vn, Vm, Tn) and a discharge current (In) between an electrode (34) and a workpiece (35), and a fuzzy inference is effected by a fuzzy control unit (12) using the estimated discharge state as an input, thereby obtaining an increment (δT) of a jump period and an increment (δD) of a jump distance. A jump period/distance modifying means (23) is used to obtain the jump period (T) and the jump distance (D), and a jump control means (24) executes a jump control based on these values, to thereby effect an electrical discharge machining. Thus, the machining speed can be increased, and the electrical discharge machining state can be improved.

Method and apparatus for electrical discharge machining

Abstract: For electrical discharge machining, voltage pulses are applied through a working liquid in the gap between a working electrode and a workpiece. Pulses of one polarity are applied to the working gap for a first period of time corresponding to a predetermined first number of pulses. Then, pulses of the opposite polarity are applied to the working gap for a second period of time corresponding to a predetermined second number of pulses. The first and second periods are repeated alternately so that high speed working can be performed with low wear of the electrode.

Control device for water system machining liquid for electric discharge machine

Abstract: PURPOSE:To sufficiently eliminate machining chips and so on, to hold cleanliness and resistivity value of machining liquid at a satisfactory level and to prolong life of an ion exchange resin by measuring the resistivity value and turbidity or a pH value and by circulating necessary and sufficient amount of machining liquid based on the result. CONSTITUTION:When turbidity or a pH value of machining liquid in electric discharge machining becomes more than a predetermined value, a circulation pump P1 for feeding the machining liquid to a filter F is activated. Next, the turbidity or the pH value becomes less than the predetermined value, the circulation pump P1 is stopped. Due to this, machining chips and so on can be sufficiently eliminated and life of an ion exchange resin can be prolonged with the holding cleanliness and resistivity value of the machining liquid at a satisfactory level, and thus, without affecting machining, cost and labor for exchanging the ion exchange resin can be reduced.

Electric discharge machine using linear motor

Abstract: PURPOSE:To enable high precision electric discharge machining and to make an electric discharge machine compact and facilitate maintenance of the machine by controlling the anode-cathode distance between a tool electrode and a work to a desired value of machining clearance according to rectilinear drive by linear motors. CONSTITUTION:An electric discharge machine has at least linear motors 3, 5 each of which drives the rectilinear movement of a main spindle 1, a guide mechanism 6 for smoothly guiding the rectilinear movement of the main spindle 1, and a linear encoder 4 serving as a detection means for detecting the rectilinearly moved position of the main spindle 1, the main spindle 1 moving rectilinearly relative to the column 2 of the electric discharge machine and holding a tool electrode 7. A control means is provided for controlling the linear motors 3, 5 so that the machining clearance between the tool electrode 7 and work 8 is adjusted to a desired value, and the anode-cathode distance between the tool electrode 7 and the work 8 is controlled to the desired value of the machining clearance according to the rectilinear drive by the linear motors 3, 5.

Electrochemical machining process and electrochemical machining equipment

Abstract: A method for electrochemical machining a work piece using an electrochemical machining device including a tool electrode opposing the workpiece across a predetermined machining gap and a device (11, 12) for supplying a pulse current to the machining gap via electrolyte provided in the machining gap includes the steps of determining a predetermined pulse current having a predetermined pulse width, selecting a plurality of partial pulse currents each having a predetermined partial pulse period, calculating a plurality of rest periods based on said partial pulse widths and applying the partial pulse currents, each of the partial pulse periods separated by at least one of the rest periods. According to the method of the present invention, the predetermined pulse width is in the range of about 10 - 50 msec. An electrochemical machining device, which includes a control unit (12), a tool electrode, a machining tank and circuitry (7, 12) for supplying a predetermined amount of the electrolyte to the machining gap during a dwell time between two sequential pulse currents to remove residual electrolytic products from the machining gap and the tool electrode is also disclosed.

Application of ion nitriding to wire-electrical-discharge-machined blanking dies

Abstract: The effects of ion nitriding on wire-electrical-discharge-machined (wire-EDMd) surfaces are examined and discussed. The hardness of the softened surface layer caused by wire electrical discharge machining was increased up to the matrix value when hardened by ion nitriding, and the wear resistance was significantly improved. As a result of blanking tests in the industrial field, the ion-nitriding process would seem to be very effective for prolonging the service life of wire-EDMd dies.

Initial hole machining device for a wire-cut electric discharge machine

Abstract: An initial hole machining device for a wire-cut electric discharge machine, which is capable of efficiently performing initial hole machining over the entire electric discharge machinable region determined by the mechanical structure of the electric discharge machine, without the need of shifting a machine coordinate system or correcting position command data and of providing a separate machining liquid feed device. The initial hole machining device has a body removably fitted in a nozzle hole of an upper wire guide of the electric discharge machine for movement between an initial hole machining position where it is fitted in the nozzle hole and a set-aside position where it is spaced from the upper wire guide. A pipe electrode for initial hole machining is mounted to the body coaxially with a wire electrode. After setting in any desired position within the machinable region by using the machine coordinate system and the position command data common to those for ordinary electric discharge machining, the pipe electrode, electrically connected to an electric discharge machining power supply through a connecting route having a small inductance, is moved toward a workpiece, so as to produce an electric discharge between the pipe electrode and the workpiece to form an initial hole, with a machining liquid supplied through the nozzle hole and a machining liquid passage of the body communicated therewith.

Control unit for electrical discharge machine

Abstract: An adaptive control unit for an electrical discharge machine having a movable electrode for machining a workpiece, the adaptive control unit including a processing circuit for detecting several machining conditions between a time when the movable electrode begins machining the workpiece and a time when the movable electrode is moved away from the workpiece, a first memory for storing the detected machining conditions, a second memory for storing information representing several rules for defining a changing a machining state; and a determination circuit for determining a value representing a machining instability condition in accordance with the machining conditions stored in the first memory, and the rules stored in the second storage means. The rules stored in the second memory include fuzzy set representations, and the second memory further stores membership functions for the fuzzy set representations.

Electrical discharge machine with machining gap voltage control

Abstract: In an electrical discharge machining apparatus, the average machining gap voltage is controlled to be a predetermined value even if a discharging operation is interrupted. This is accomplished by providing a bypass circuit (101) or an inverse voltage providing circuit that responds to an interruption in the discharging operation. By controlling the average machining gap voltage, electrolytic corrosion and magnetization of the workpiece is minimized.