Showing papers on "Electrical discharge machining published in 1985"

Studies of the discharge mechanisms in electrochemical arc machining

Abstract: The electrochemical arc machining (ECAM) process combines features of ECM and EDM by application of a pulsed voltage between a cathode-tool and anode-workpiece in a liquid electrolyte. The new process offers rates of metal removal as much as five and fifty times greater than ECM and EDM, respectively. The study reported in this paper explores some of the fundamental processes which occur during ECAM. Experimental apparatus was constructed to enable single pulse discharges to be studied. Results are presented for 200μs pulses between 2 mm diameter silver steel electrodes in NaNO3 and NaCl electrolytes over a gap range of 10 to 90μm. Four stages of electrical phenomena were distinguished within a pulse: (a) high frequency voltage and current oscillations, (b) high rate electrochemical action, (c) low rate electrochemical action, and (d) electrodischarge action. The relative durations of the electrochemical and discharge phases, respectively, increase and decrease with increasing gap width, and vary with electrolyte type and concentration. High speed photography with an image-converter camera was used to record the occurrence of both spark and arc discharge in an electrolyte.

Electrode wire for use in electric discharge machining and process for preparing same

Abstract: An electrode wire for wire electric discharge machining a workpiece at high speed and high accuracy and a process for preparing the same are provided. The electrode wire comprises a core wire made of a copper clad steel wire, 10 to 70% of the sectional area of the copper clad steel wire being occupied by copper, and a copper-zinc alloy layer covering the core wire. The copper-zinc alloy layer is prepared by coating the core wire with zinc by electroplating or hot galvanizing, followed by heating to disperse copper in the zinc layer to convert the same into a copper-zinc alloy layer wherein the concentration of zinc is increased gradually along the radially outward direction. The preferable thickness of the copper-zinc alloy layer ranges from 0.1 to 15 microns and the average concentration of zinc in the copper-zinc alloy layer is preferably less than 50% by weight but not less than 10% by weight.

Power source for electric discharge machining

Abstract: A power source for electric discharge machining, which performs a semi-mirror-finish machining operation with a surface roughness of 1 μm Rmax or less. The power source includes either a resonance circuit or an impedance matching circuit so that the electric discharge is carried out under the condition that resonance is caused to occur with the capacitance of an interelectrode gap between an electrode and a workpiece to be machined or the impedance-matching is effected in response to variation in interelectrode condition. With such a power source, it is possible to eliminate the effect of the stray capacitance exsiting in a current supplying line and also to eliminate the shortcoming due to variation on the interelectrode condition, and therefore a mirror-finished machining operation can be stably carried out to provide machined surfaces excellent in surface roughness.

Process and mechanism for threading the electrode wire of an EDM apparatus

Abstract: A method and apparatus for threading the electrode wire of a travelling wire EDM apparatus through an aperture in a workpiece. Prior to automatically threading the wire through the aperture in the workpiece, the wire is continuously straightened by pulling longitudinally on the wire, and the wire is passed through a guide tube and through a nozzle to which fluid under pressure is supplied for forming a jet stream at the outlet of the nozzle. Prior to a threading or rethreading operation the wire is cut off proximate to the outlet of the nozzle. The nozzle outlet is brought in close proximity to the aperture in the workpiece and the jet stream is aimed at the aperture in the workpiece for guiding the wire through the aperture, while being maintained coaxially by the jet stream. The consecutive steps for feeding the end of the wire through an aperture in the workpiece are effected in sequence for initial threading of the wire through a pre-drilled stating hole in the workpiece, or for rethreading the wire through a cut in the workpiece after accidental rupture of the wire during a cutting operation.

Inert-Gas Electrical Discharge Machining

Abstract: Holes in complicated hardware successfully drilled by dry EDM process that uses tubular copper electrode and argon or helium gas as dielectric medium.

Mirror-Like Finishing by EDM (Multi Divided Electrode Method)

Abstract: This paper describes the new methods of fine finishing by electro discharge machining (EDM).

Selective power supply for travelling wire EDM apparatus

Abstract: In a travelling wire EDM apparatus the thermal stresses of the electrode wire are substantially reduced by detecting the position of the triggering electrical discharges preceding the machining electrical discharges, and by controlling the supply of the machining electrical discharge current at one end of the machining zone, at the other end of the machining zone or at both ends of the machining zone. When a machining electrical discharge is located between one end of the machining zone and a first reference position, the machining current is applied at that end. When the electrical discharge is located between the other end of the machining zone and a second reference position, machining current is supplied at that second end. When the electrical discharge is located between the two reference positions, the machining current is applied simultaneously at both ends of the machining zone.

Wire cut electrical discharge machining device

Abstract: PURPOSE:To prevent the accuracy of machining from lowering, by detecting variations in the electrical resistance between the electrical power supply point and electrical discharge point of a wire electrode so that a position where electrical discharge occures is detected, and as well by controlling, in accordance with the position, the mean machining current or discharge pulse energy between the electrode and a workpiece. CONSTITUTION:A wheatstone bridge is balanced so that no current runs through resistances 15, 16 when electrical discharge occurs at the mid-point of a wire electrode 2 between electrical power rollers 3, 4 in such a condition that the resistant values of resistances 13, 14 are equal together. However, when electrical discharge occurs at a point remote from the mid-point of the electrode 2, unbalanced current runs through resistances 15, 16. When an electrical discharge point detector 17 detects satisfactory electrical discharge, randomly and uniformly in the vicinity of the mid-point of the electrode 2, a control circuit controls a switching element 8 to make large the width of voltage pulses fed between the workpiece 1 and the electrode 2 or to increase discharge current or the number of pulses, thereby satisfactory machining may be made with a high degree of efficiency in the vicinity of the center section of the workpiece 1 so that any defects are prevented from occuring.

Structure for and method of electrical discharge machining

Abstract: Structure for and method of electrical discharge machining with a wire electrode to produce small holes including completely controlling electrical discharge machining parameters such as voltage, reactance, current and servo speed with a programmable microprocessor, central processing unit sensing first sparking between the wire electrode and the workpiece and controlling depth of cut from the position of the electrode on spark initiation electrode feeding to replenish eroded electrode through clamping sequencing between an electrical discharge machine head and an electrode carrying slide thereon. In accordance with the invention there is also provided ultrasonic vibration of at least one of the workpiece, a wire electrode guide and the electrode during machining. Also, the slide is driven by a screw and nut combination including a plastic extruded between the screw and nut to remove backlash therefrom and the tapered end of the wire electrode is removed prior to electrical discharge machining therewith by machining with the tapered end of the electrode with a reverse polarity, that is with a high wear polarity, between the electrode and workpiece, and splitting of the wire electrode is substantially eliminated by increasing the pulse time of the cutting parameters and lowering the current thereof while flushing at a low velocity.

EDM apparatus provided with means for holding a portion cut off from the workpiece

Abstract: In a travelling wire EDM apparatus for effecting a cut by electrical discharges on a workpiece blank by an electrode wire, the workpiece blank is supported by two support members mounted on a rotary table, one support member being disposed in the interior of the perimeter of the cutting path and the other support member being disposed exteriorly to the perimeter of the cutting path such as to support the two portions of the workpiece blank severed from each other during the cutting operation. A partial cut is first effected through the workpiece blank and the workpiece blank is subsequently angularly oriented to a different position by rotating the rotary table such that collision between any one of the electrode wire support arms and the workpiece blank support member disposed within the perimeter of the cutting path is prevented. The cut is continued along a cutting path corrected as a function of the new angular position of the workpiece, and at the end of the cut the portion severed from the workpiece blank is supported by the support member disposed within the perimeter of the cutting path and the remaining of the workpiece blank is supported by the other support member.

Electrical discharge boring machine

Abstract: An electrical discharge boring machine including: a main unit (12) which is moved vertically relative to a workpiece (W); a rotary chuck (14) attached to the lower part of the main unit (12) for holding a hollow bar electrode (16); a guide (36) for slidably guiding the hollow bar electrode (16) near the workpiece (W); a nozzle unit (40) provided on the lower part of the guide for supplying a machining liquid; a rotary joint (28) for introducing the machining liquid into the hollow bar electrode; and a connection (34) for supplying electric power for electrical discharge machining to the hollow bar electrode.

Process and apparatus for determining the electroerosive completion of a starting hole

Abstract: The completion of a starting hole produced by spark erosion in a workpiece by use of a starter electrode in an electroerosion machine is automatically detected by a sudden change in a sensed process parameter when the starter electrode has passed through the workpiece.

Electric discharge machining electrode

Abstract: An electrode for precision electric discharge machining having an improved machining rate and surface smoothness with respect to conventional graphite and copper electrodes. The electrode is formed by silicon or other materials which has the same characteristics as silicon, a base of a low melting point metal or an alloy of such a low melting point metal is covered with a layer composed of a mixture of the metal and a high resistivity inorganic compound. The outer layer may be formed by adhesion or by thermal spraying or by a powder metal sintering technique.

Laser-beam operated machining apparatus

Abstract: A laser-beam operated machining apparatus capable of performing machining operations on a high-reflectivity material such as aluminum or copper. A nozzle is provided for applying a focused laser beam together with an assist gas to a surface of a workpiece to be machined. An annular electrode is provided on the end of the nozzle confronting the workpiece with the electrode being coaxial with the laser beam. An arc discharge is created between the annular electrode and the workpiece by applying a voltage between the annular electrode and the workpiece so as to cause an arc discharge therebetween.

Method of measuring flexure value of wire electrode

Abstract: A method of automatically measuring the flexure value of a wire electrode 1 in a wire-cut electric discharge machine is disclosed. At a measurement point in the course of electric discharge machining, the electric discharge is temporarily stopped, and whether or not the wire electrode 1 and a workpiece 2 come into contact is sensed by a contact sensing device 107a. The wire electrode 1 and the workpiece 2 are moved relatively to advance or retreat in accordance with the sensed touch signal TS, and the distance e1 of movement until the contact state changes, is measured. The flexure value e is obtained calculatively from the measured movement distance e1.

Method and device for controlling the tool electrode in an electrical discharge machine tool

Abstract: The up and down movement of the tool electrode of an electrical discharge machine is controlled by a circuit arrangement including an electrical discharge condition judgment circuit monitoring the electrical discharge between a tool electrode and a workpiece from the waveform of the discharge and outputting a pulse signal in the event the discharge is abnormal, a motion command circuit which receives and counts the judgment circuit output signal and generates a command signal when the count reaches a set value, and an electrode control circuit responsive to the command signal and causing the tool electrode to move up and down

Method and apparatus for electric discharge machining with adaptive feedback for dimensional control

Abstract: Electric discharge machining of workpieces on a mass production basis is accomplished with adaptive feedback control to achieve accurate machining of a feature to a specified size. After machining a feature, it is measured to obtain a value which represents its size. An EDM process parameter is adjusted in accordance with the measurement value so that the next feature will be machined with the size closer to the specified size. Multiple features are machined in succession and the measurement values of successive features are analyzed to determine the trend of change of the values with respect to the specified size. The parameter, such as spark energy, is adjusted in a sense which tends to cause the succeeding features to machined more accurately to the specified size.

Method and device for wire-cut electric discharge machining

Abstract: PURPOSE:To have quick loading of a wire electrode by carrying out formation of a machining start hole and threading of wire electrode automatically using a mounting chuck for electrode in the form of a thin tube, installed with possibility of rising and falling freely. CONSTITUTION:In this wire-cut electric discharge machining device, an electrode 1 in the form of a thin tube is installed on a mounting chuck 25 for this thin tubed electrode, wherein the chuck can rise and fall freely, and a wire electrode 2 is threaded through this thin tubed electrode 1. This wire electrode 2 is grasped by a holder 22 so as to be fed in the axial direction together with the thin tubed electrode 1. Then the tip of the wire electrode 2 is cut off so as to be in a plane with the tip of the thin tubed electrode 1, and the machining liquid is supplied to the center hole 1a in the electrode 1. Now pulsed voltage is impressed with the tips of electrode 1, 2 fronting to the work to be machined 35, and small hole for insertion of electrode is machined while appropriate feed is given to the thin tubed electrode 1 using a hydraulic cylinder 29. Then the electrode 2 is released from grasp to be sent to a wire electrode receipt device so as to provide stretching over, and the electrode 1 is drawn out of this small hole.

Wire electric discharge machine

Abstract: PURPOSE:To permit the unmanned operation in wire electric discharge machining by applying an impact onto a workpiece forming the cut inside part by a working-liquid feeding nozzle and removing the workpiece by moving a receiving metal vertically and blowing-off the workpiece by the working liquid. CONSTITUTION:When a workpiece 20 forming the inside shape is cut from a workpiece 21 forming the outside shape, wire electric discharge machining is completed, leaving a cut rest part in 0.5mm. or so. After an electrode is cut-off, a liquid pressure is applied by feeding working liquid 22 over the range from the upper surface of the workpiece 20 to an upper working-liquid feeding nozzle 1 and a receiving metal 2 from a working-liquid feeding hose 3, and then the upper working-liquid feeding nozzle 1 shifts in the direction of arrow A, and applies an impact onto the workpiece 20, and beats-down the workpiece 20 from the workpiece 21. A lower working-liquid feeding nozzle 1 receives the workpiece 20, and a screw 101 is turned by a motor and a gear 100, and the receiving metal 2 is shifted upward, and the workpiece 20 is pulled-out from the workpiece 21 by the lower working-liquid feeding nozzle 1. At last, the working liquid 22 is allowed to collide with the workpiece 22 through an auxiliary hose, and blows-off the workpiece outside the surface plate of a table.

Method of making a drill-shaped cutting tool and thread rolling dies

Abstract: A method of making the drill-shaped cutting tool and its thread rolling die by which the workpiece such as the wire rod is rolled. The thread rolling die has a majority of uneven parts for forming the drill part formed by an electric discharge. The electrode for electric discharge machining is equipped with a pair to undergo the electric discharge and is formed to be approximately drill-shaped by forming the groove like uneven parts at least on the approximately cylindrical body possessing the diameter approximately equal to that of the drill part of the cutting tool to be made, and is then rotated and moved in parallel with the thread rolling die.

Wire EDM method for preventing wire lagging during machining of an angular corner and workpiece position control

Abstract: A machining control method for an electrical discharge machine compensates for the lagging of the wire electrode as the electrode is advanced from a straight line portion to a change of direction portion of the outline to be machined. The wire electrode is advanced from the straight line portion of the outline until it reaches the change of direction point of the outline and is then halted until the wire electrode lag is corrected. During the halt, machining takes place under a different set of conditions. When the lag is corrected, the wire electrode is advanced along the change of direction portion under a third set of machining conditions. When the wire electrode reaches another straight line portion, the outline machining of the workpiece is resumed under the first set of machining conditions. Also disclosed is a method of controlling the positioning of a workpiece by trial positioning a large number of workpieces having a variety of weights under a variety of load conditions of the control motor. The positioning accuracy of the trial positionings are measured and a table of correction values for positioning according to the desired positioning is calculated and stored. When positioning a workpiece to be machined, the weight and motor load are compared to the stored correction values, a correction value is determined, and the workpiece is positioned using the determined correction value.

Wire-cut electric discharge machining method

Abstract: PURPOSE: To prevent an unsatisfactory discharge or an impossible discharge due to residual chips and an open wire or unsatisfactory machining accuracy caused by biased dissipation of an electrode by melting a traveling wire electrode while rotating it centering its axis. CONSTITUTION: A wire electrode 1 is extracted from a feed reel 2 and travels at a fixed speed and passes a work 7 while being rotated in the positive direction and negative direction centering its axis by a rotary driving device 9 made of rollers 10 reciprocating in opposite directions to each other after passing a die guide 8. A machining liquid is sprayed through a nozzle 11, the voltage is applied across an electrode 1 and the work 7 serving as both poles, an electric discharge is generated, and the molten portion is scattered as chips. The work 7 is moved by a table 6, and chips scattered at the gap section between the electrode 1 and machining section 12 are exhausted and removed so as to be gradually extracted to a wide space section on the opposite side to the machining side because the electrode 1 is being rotated. COPYRIGHT: (C)1987,JPO&Japio

Power source for electric discharge machining

Abstract: PURPOSE:To make the ascending and descending inclination of interpole current steep, by providing a capacitor on the power source load side through the inter mediary of diodes to temporarily accumulate the electromagnetic energy of inductance of a circuit upon turn-off so that thus accumulated energy is used upon turn-on. CONSTITUTION:When switching transistors 4, 5 are turned off from a turnon condition, electromagnetic energy accumulated in drift inductances 8a, 8b in a circuit may be used as machining energy between an electrode 2 and a workpiece 3. Simultaneously, a capacitor 10 is charged through diodes 6, 7 so that a terminal voltage Vc rises, and therefore, the time during which interpole current iG drops to zero after the turn-off is made shorter than that during which no charge is made. Accordingly, the descending inclination becomes steep. Upon turn-on a voltage charged in a capacitor 10 is applied in addition to a voltage E exerted to the switching circuit through diodes 9a, 9b, and therefore, the ascending inclination of the interpole current iG becomes steep.

Process and apparatus for monitoring thermal stresses in an electrode wire in an EDM apparatus

Abstract: In a travelling wire EDM apparatus in which a workpiece is cut by an electrode wire by electrical discharges between the wire and the workpiece, a detector circuit detecting each electrical discharge occuring in each sector along the length of the wire in the machining zone. The information detected by the detector circuit is supplied to a circuit simulating the increase of heat of the wire, and the convection of heat into the ambient and into adjoining wire sectors. A control signal for modifying a machining parameter is supplied when the simulator circuit provides an indication of abnormal heating of the wire in one of the wire sectors. Accidental rupture of the wire is thus avoided while assuring that machining is effected at maximum efficiency.

Wire cut electric discharge machining method

Abstract: PURPOSE:To correct a wire electrode to be straightened and improve its machining accuracy and speed, by repeating the process, which feeds the wire electrode and a work by a predetermined distance at a predetermined speed injecting machining fluid at a predetermined pressure, and the process moving the wire electrode and the work by the predetermined distance by decreasing the predetermined pressure and the predetermined speed. CONSTITUTION:If a pair of positioning wire guides 3, 3' move from a point A to B by a distance alpha, a wire electrode 1 is placed in a condition that it flexes the central part in a bow shape in a direction reverse to the machining feed direction by an electric discharge pressure or the like, therefore a device, decreasing a machining feed speed in this position smaller than the predetermined speed simultaneously converting the pressure of machining fluid in machining fluid injection nozzles 4, 4' into a pressure smaller than the predetermined pressure, performs machining while removing by the pressure of fluid the generated gas, sludge, etc. in a machining gap and contaminated machining fluid. Here the device, reducing a vibration of the wire electrode and the machining feed speed in a slow level, performs machining holding accuracy with a less increase of a machining groove width. Further the wire electrode 1, providing strong tension acting, is placed almost to a linear condition from the bow-shaped flexed condition, maintaining the accuracy.

Wire discharge machining power source

Abstract: A wire discharge machining power source controls an average machining voltage value applied between a wire electrode (P) and a workpiece (W) to be zero to prevent galvanic corrosion of the workpiece (W). A reverse voltage application time control circuit (2) detects the average machining voltage value and generates a pulse (S5) having a pulse width corresponding to a detected value. A reverse voltage regulating circuit (1) detects a difference between a reference voltage and a voltage applied between a transistor (T2) and a resistor (R2) upon application of the reverse voltage through the transistor (T2) and the resistor (R2), and supplies a difference signal, which corresponds to the detected difference, as an ON control signal to the transistor (T2) for a period corresponding to the width of the pulse (S5), thereby controlling the reverse voltage value and setting the average machining voltage value to zero.

Wire cutting type electrical discharge machining system

Abstract: A wire cutting type electrical discharge machining system includes a wire supply device, an upper and lower electrode guides, and a wire take-up device for feeding a wire electrode so as to carry out the discharge machining on an electrically conductive workpiece. An improved wire-disconnection detecting device attached to the system includes a first and second wire-slack detecting members of metallic tube through which the wire is passed with a small distance formed therebetween, a wire-disconnection detecting circuits connected between the detecting members and the wire, including a power supply, and a sensor for sensing a flow of current from the power supply through the detecting members and the wire upon contact of the two due to a slack of the wire. A disconnection of the wire is detected when the flow of current is sensed by the sensor.

Wire-cut electric-discharge machining apparatus

Abstract: PURPOSE:To permit the correct corresponding control by measuring the electric-conduction characteristic according to the variation of the dimension, shape, material, surface state, etc. of each part in the longitudinal direction of a wire electrode and obtaining the necessary information for controlling working conditions. CONSTITUTION:In order to increase/decrease-control the tension of a working- part wire electrode 3 according to the electric-conduction characteristic of the wire electrode 3 which is detected between electric-conduction rollers 12a and 12b, a detection signal is applied onto a controller 9 by a detection power source 11, and a capstan roller 6 and a brake roller 6' are driven so that the applied tension is increased or decrease by a prescribed amount by increasing or decreasing the difference of the set number of revolution between the driving motors 7 and 7', and the working apparatus is operated through the detection feedback control by the rotary encoder of the rotary shafts of the electric motors 7 and 7' or pointer speed generators 8 and 8'. The detection electric- conduction characteristic is detected by the electric-conduction pins 12a' and 12b' and the power source 11, and compared with the electric-conduction characteristic between the electric-conduction pins 12a and 12b, and a detection signal is used as the switching control signal for the working condition.