Showing papers on "Electrical discharge machining published in 1981"

Role of Impurities in Electric Discharge Machining

Abstract: This paper summarizes the experimental and theoretical investigations to determine the effect of impurities in dielectric liquid on the Electric Discharge Machining performance.

Method for a shaping of polycrystalline synthetic diamond

Abstract: The present invention refers to a method for the shaping of polycrystalline, synthetic diamond and, in particular, to the production of profiled parts like tools The shaping process is performed by spark erosion with electrodes shaped accordingly

Analysis of Electro Discharge Machining of Cemented Carbides

Abstract: Summary The difficulties of correlating Electrical Discharge Machining (EDM) process parameters with the surface integrity aspects of machined cemented carbides have been recognized. These difficulties arise not only because of complex and random nature of spark phenomenon but also due to the complex composition and structure of the cemented carbide materials. This paper analyzes the surface profiles of spark eroded cemented carbide workpieces in the light of a recently introduced Data Dependent Systems approach to EDM. The parameters of a model obtained from such an analysis are shown to render fairly accurate values of technological factors such as material removal rate, surface roughness and electrode wear. Various grades of Kennametal cemented carbides are machined with conditions recommended by the CIRP's Scientific Technical Committee E. The application of a thermal model based on the Data Dependent Systems approach to predict material removal rate in this case is demonstrated. The possibility of relating the length of cracks with the machining parameters and material properties using such a thermal model is discussed.

Heat Transfer Modelling of Electric Discharge Machining

Abstract: In the presented research, Heat Transfer Modelling of Electric Discharge Machining (E.D.M.) is investigated, in detail. Two new models along with existing ones are presented. One of the new models is based on the uniformly-distributed-point-sources assumption. The other one is an approximate but general model, involving time variation of heat source and its radius. When simpler models are used, the agreement with the experimental results is less. More complex models with channel expansion required excessive computational times. Aggreement with the experimental data is shown to be satisfactory for all cases.

Electric discharge machining device

Abstract: PURPOSE:To obtain desired peak current value in an electric discharge machining even in the case of a finishing process where the electric discharge current pulse width is extremely short by improving the first transition of the electric discharge current with a compensating current and shortening the last transition period. CONSTITUTION:A low impedance circuit 14 for high frequency is provided in parallel to a machining pulse transmission circuits 10 and 11 to improve the first transition and the last transition delay of the electric discharge current wave figure due to the high frequency impedance in the circuits 10 and 11, a coaxial cable (the circuit 14) constituting a low impedance circuit for high frequency consisting of a machining gap 3 to a D.C. power source 4 and a current limiting resistor 6 via a capacitor 15. When a switching element 6 for the control is turned on by a signal from a control part 7 the voltage is applied to the gap 3 to start the electric discharge. Thus, desired peak current value can be obtained even when the discharge pulse width is extremely short.

Fluid jetstream threading mechanism and method for travelling wire EDM apparatus

Abstract: A method and apparatus for threading or rethreading the end of an electrode wire through an aperture in a workpiece in which a cut is to be effected, by electrical discharges in a machining zone between the electrode wire and the workpiece. While the end of the electrode wire is brought in proximity with the inlet of the aperture in the workpiece, the end of the electrode wire is disposed in a pressurized fluid flowing towards the inlet of the aperture in the workpiece such that the end of the electrode wire is automatically centered relative to the aperture, and threading the end of the wire through the aperture.

Wire cut electric discharge machining system

Abstract: PURPOSE:To prevent generation of dullness in a corner part, by drawing a perpendicular from a crossing point of cutting lines in the inside of a corner to a machining route and decelerating feed speed of a wire electrode about a crossing point of said perpendicular and machining route as the center. CONSTITUTION:When a work W and wire electrode P are moved along a corner route as shown by a chain line in the drawing, a corner point A, the foot C of a perpendicular, drawn from an intersecting point of cutting lines in the inside of a corner to a machining route, the middle point B between the points A and C, and a point D, with a distance to the point C equal to a distance from the point B to the point C, are calcutated and stored. At the point A where machining is transferred from a linear part to a corner part, machining voltage rises, and tension of the wire electrode P is increased to suppress oscillating amplitude of the wire electrode P. If the wire electrode P reaches the point B, a feed speed is decreased to about 0.7 times the feed speed Fo in the linear part, if the wire electrode reaches the middle point between the points B and C, the speed is decreased to about 0.5 times, if further reaches the middle point between the points C and D, the speed is increased to about 0.7 times, and if reaches the point D, the wire electrode is controlled to move at the initial speed Fo.

Electric discharge machining apparatus

Abstract: PURPOSE:To permit even a DC supply source of low voltage and small capacity to perform electric discharge machining of stable worked surface roughness by jointly using a switching element, an inductance coil and a capacitor. CONSTITUTION:A transistor 6 is turned on/off by a control circuit 13, and while the transistor 6 is conducting, an inductance coil 8 and a capacitor 10 are simultaneously charged with energy. Even after the charging of the capacitor 10 has been completed, a minute current due to a by-pass resistor is flowing through the inductance coil 8. When the transistor 6 is turned off, a high-voltage impulse due to a counter electromotive force generated in the inductance coil 8 is applied through a polarity switch 4 and a diode 9 to a working gap 3 to breakdown the insulation. Then, electric discharge machining is performed by the given amount of working energy stored in the capacitor 10. Thereby, excellent electric discharge machining, by which the worked surface roughness is also stabilized, is made possible.

Wire cutting electric discharge machining method

Abstract: PURPOSE:To correct the displacement of the machining starting hole where the wire electrode is automatically fed, by a method wherein when the wire electrode is difficult to automatically feed at the normal position owing to the displacement of the machining starting hole, it is detected by searching in the vicinity CONSTITUTION:In the case of the displacement of the machining starting hole 24 in a workpiece 20, if the automatic feed of the wire electrode is tried, a pipe guide 56 contacts or collides with the workpiece 20 Consequently, the automatic feed is impossible In such a case, the table mounted with the workpiece 20 is moved in the vicinity of the position where the normal machining starting hole should be located, radially, in the enlarging circle direction or in the specific rectilinear direction, in order to detect the actual machining starting hole 24 After it has been detected, the automatic feed of the wire electrode is performed

Manufacture of cooled aerofoil blades

Abstract: A method of manufacturing cooled aerofoil blades in which blade parts are bonded together to provide complete blades. The blade parts are provided with mating surfaces which are simultaneously spark erosion machined to match the same prior to the blade parts being brazed together. Spark erosion machining is performed by maintaining the mating surfaces to be matched at a constant distance apart from each other and translating a tensioned wire electrode along a path passing mid-way between the mating surfaces.

Device for electrical discharge machining with simultaneous relative advance and cyclic translational movement of the electrodes

Abstract: In the electrical discharge machining of the surface of a recess in a workpiece electrode to a shape corresponding to that of a tool electrode, the electrodes are relatively displaced, during a finishing phase of machining, along an axis of penetration and simultaneously in a plane perpendicular to the axis of penetration with a cyclic translational movement whose amplitude increases with the penetration of the tool in the workpiece. This provides a virtual three-dimensional dilatation of the tool as it advances, and enables control of the sparking in both the frontal and lateral parts of the machining zone. The cyclic translational movements are obtained from a rotatable shaft having an axis parallel to the axis of penetration and an eccentric member cooperating with the rotatable shaft to slide relative to the shaft in a direction forming a predetermined angle with the direction of penetration, the eccentric member being rotated in unison with the shaft about its axis.

Method and apparatus for threading an electrode wire through an aperture in a workpiece

Abstract: A method and apparatus for threading the electrode wire of a trailing wire EDM apparatus through a starter hole or aperture in the workpiece or through the machined slot, the workpiece being submerged in a machining fluid. A chamber is disposed in contact with the workpiece under the workpiece, the chamber being in communication with an end of the aperture through the workpiece. The chamber is connected to a source of suction, with the result that fluid being sucked through the aperture in the workpiece converges towards the inlet of the aperture and guides the end of the electrode wire into the inlet of the aperture.

Shape compensating method for wire-out electric discharge machining

Abstract: The flexure value of a wire electrode in a machining tangential direction and the flexure value in a radial direction are obtained by a computerized numerical control device using the wire electrode speed of an electric discharge machine, the width of a machined groove and the flexure value during straight machining The corrected position of the wire electrode is calculated using the above two flexure values Distributed pulses are provided by pulse distributors on the basis of the calculated movement values relative to a current position, and servo motors in the electric discharge machine are driven by the distributed pulses fed through moving direction controllers, thereby to perform shape compensation in wire-cut electric discharge machining

Method of reducing wire-cut electric discharge machining errors

Abstract: A method of controlling a wire-cut electric discharge machine to prevent cutting errors when cutting a corner CN which are caused by flexing of a wire electrode 1 during electric discharge cutting of a workpiece. Electric discharge is stopped when a rectilinear slot is cut to measure an amount of flexing of the wire electrode 1, and then the measured amount of flexing is used to effect an arithmetic operation to calculate a commanded speed or an interval of time in which relative movement between the wire electrode and the workpiece is arrested at the corner CN. The corner CN is cut under the control of the calculated commanded speed or interval of time in which the relative movement is arrested.

Electric discharge machining apparatus

Abstract: In an electric discharge machining apparatus for machining a workpiece by confronting an electrode and the workpiece through an insulating machining solution, feeding the electrode to the workpiece and causing electric discharge between the confronting electrode and workpiece the difference between the most advanced position of the electrode relative to the workpiece and the present position of the electrode is detected and a signal is outputted by identifying the interelectrode state in accordance with the detected result. Thus, the propriety of the interelectrode machining gap state in the electric discharge machining are accurately observed, and the workpiece is machined under preferable machining conditions.

Spark machining device

Abstract: PURPOSE:To enable free controlling and setting of the azimuth angle of a member forming a machining part within a certain range in the course of machining by constituting the main plane of a main guide to accord with the progressing direction of machining constantly during the electrospark machining. CONSTITUTION:A wire electrode 14 is pulled out from a feeding reel 4 and is passed between brake rollers 22 and 23, through subguides 17 and 18 and along the outer-peripheral part of the main guide 15, where it is turned back. Then, it is passed through a subguide 17', a capstan 24 and a pinch roll 25 and rolled up by a roll-up reel 6. Next, the machining feeding is given to a workpiece 41 only by translation operation so as for a point B on a machining curve to accord constantly with the turn-back point of the electrode, i.e. the origin 0, while the main plane of the guide 15 is rotated round a perpendicular axis containing the turn-back point of the electrode, i.e. an axis Z, and thus the azimuth angle of a machining member is controlled so that the tangent line TB of the machining curve may be located constantly on the main plane of the guide 15.

Wire cut electric discharge machining method

Abstract: PURPOSE:To make a filter reusable and its handling easy as well as to aim at a reduction in machining expenses, by dispensing with such a process that turns the machining solution reclaimed system to a double system, and prolonging the duration of a filter change period, while removing a workpiece body sticking to the filter in addition. CONSTITUTION:In case of an operation in machining solution circulating type wire-cut electric-discharge machining, a layer 2' composed of China clay is applied and formed with 2-3mm. in thickness onto the surface of a paper filter element 3 having a paper filter made up in petallike form, then dried up and settled on the filter surface. Afterward, the paper filter element 3 on which the said layer 2' is formed is inserted into an electric discharge machining solution circulating system, through which conventional wire-cut electro-discharge machining is performed. With this process of work, the China clay layer 2' is replaced with a new one every two weeks whereby the paper filter withstands the continuous use for nearly two months or so, thus not only its handling is every so easy but also it is advantageous from the economical standpoint.

Machining method and apparatus

Abstract: A method of and apparatus for machining, especially electroerosion machining, of a workpiece immersed in a machining liquid received in a worktank with a tool juxtaposed with the workpiece to define a machining interface therebetween filled with the machining liquid. A plurality of ultrasonic assemblies are disposed in the worktank in such a manner that they are spaced apart from each other and arranged to surround the region of the machining interface in a wave-transmitting relationship therewith through the machining liquid and individually energized to provide ultrasonic vibrations of a frequency of 0.05 to 10 MHz which are transmitted to the region of the machining interface through the machining liquid. Each of the ultrasonic assemblies is formed with a fluid injection nozzle and positionable to orient the latter in the direction of the machining interface, through which nozzle a forced flow of the machining liquid is provided from a liquid source. The ultrasonic vibrations are thus imparted at each nozzle to the machining liquid forced in the direction of the machining interface. The ultrasonic transducers are responsive to a gap parameter and an additional vibration of less than 50 KHz can be impressed on the machining liquid.

Electroerosive machining method and apparatus with discrete metallic electrode bodies

Abstract: A novel electroerosion machining method and apparatus makes use of an elongate, open-ended tubular casing of a heat-resistant material retaining therein discrete metallic bodies (e.g. granular particles, flakes, fine powdery particles or broken wires) in a packed state. The casing is axially juxtaposed with a workpiece to define a machining site in the region of the latter proximate to the open-end portion of the casing and traversed by a machining liquid. A conventional electroerosion power supply furnishes a machining current between the workpiece and the discrete metallic bodies in the casing successively fed into the machining site to electroerosively remove material from the region of the workpiece against the discrete metallic bodies functioning as continuously consumed eletroerosion electrodes in the machining liquid medium. The casing and the workpiece are relatively displaced three-dimensionally to cause the open-end portion of the casing to sweep over the workpiece to form a desired cavity of desired shape therein.

Electroerosive wire-cutting method and apparatus with a shaped wire electrode

Abstract: A method of and an apparatus for electroerosively wire-cutting a conductive workpiece with a continuous wire electrode supported to extend and axially transported to move between a supply site and a collection site through a cutting zone The moving wire electrode is juxtaposed in the cutting zone with the workpiece to form a machining gap therewith supplied with a machining liquid A machining current is passed through the gap to electroerosively remove material from the workpiece The moving wire electrode and the workpiece are relatively displaced along a predetermined path which defines the desired pattern of wire cut in the workpiece The wire electrode fed from a supply reel is of a regular cross-sectional contour (eg circular) which is, upstream of the cutting zone, shaped into a cross-sectional contour (eg square or triangular) preselected in conjunction with the desired pattern of cut to be formed in the workpiece The shaping means may take the form of a drawing die or an electroerosive wire-cutting electrode assembly

Traveling-wire electroerosion machining electrode and method

Abstract: An improved electrode and method for electroerosion machining both of traveling-wire type wherein an elongate element having a thickness of 0.05 to 0.5 mm is axially displaced to form a traveling-wire machining electrode therefrom. The traveling-wire machining electrode is juxtaposed with a workpiece across a machining gap flooded with a machining liquid issuing from a jet and a machining current from a source is passed between the electrode and the workpiece to electroerosively machine the latter. Gaseous bubbles formed by the electrical decomposition of the machining liquid tend to be adherent on the machining surface of the electrode and thus act as a thermal insulator between the electrode and the coolant machining liquid. The elongated element is formed with a rugged peripheral surface along a length thereof to facilitate the detachment of the gaseous bubbles from the machining surface of the electrode. Various ways of producing the rugged peripheral surface are described, e.g. by forming projections and recesses in a regular pattern on a cylindrical wire surface; twisting together a group of small diameter wires; winding a small diameter wire on a large diameter core wire; and forming a spiral groove in the smooth surface of a wire by means of a rotating die.

Threading and conveying device for an electrode wire in an EDM apparatus

Abstract: A threading mechanism for threading the electrode wire of a travelling wire EDM apparatus, the end of the electrode wire being passed through a starter hole or aperture in the workpiece prior to effecting a cutting operation in the workpiece, wherein the entrance throat to the wire conveying mechanism adapted to take hold of the wire after passage through the starter aperture is offset laterally relative to the axis of the starter hole such as to laterally displace the wire to engage the wire with a guiding surface and a current feeding surface which are also offset relative to the axis of travel of the wire through the starter aperture.

Wire cut discharge type machining device

Abstract: PURPOSE:To set the optimum distance between fulcrums in proportion to the thickness of a work automatically and with high accuracy by a method wherein the optimum distance between fulcrums is computed by a numerical control unit in proportion to the thickness of the work and the distance between the fulcrums is set by a driving device. CONSTITUTION:A holder 70 is fixed in a unitary body to a slider 44 on which an upper fulcrum 34 and an upper feeder plate 26 are fixed. A contactor 72 being supported by this 70 moves in a vertical direction together with the displacement of the slider 44 and a contact position data in the vertical direction is inputted to a numerical control unit 54 when the contactor comes in contact with the surface of a work 18. This numerical control unit 54 calculates backward the thickness of the work 18 in the electric discharge machining position, drives a Z-axis servomotor, moves the upper fulcrum 34 of the upper and lower fulcrums 34, 36 of a wire electrode 20 and sets a distance between these two fulcrums 34, 36 to the optimum in order to conduct precise electric discharge machining of the work 18.

Electric discharge machining apparatus

Abstract: PURPOSE:To make it possible to highly accurately perform the measurement of the work configuration and the position inspection by a method wherein the working electrode or the inspection electrode is made to face to the workpiece, a microvibration is applied to one, thereof, power is supplied therebetween in order to detect the contact state change at the gap control is so effected that said detection signal is constant at all times, and the vibration output is recorded or displayed. CONSTITUTION:A wire electrode 1 is vibrated by a vibrator 8. An inspection voltage is applied to the gap between the wire electrode 1 and a workpiece 11 by a power source 16, and the nearly contact state between the wire electrode 1 and the workpiece 11 is detected by a resistor 17 as a voltage signal. While the number of the vibrations N or energy E of the vibrator is being controlled by a control circuit 18 so that said voltage signal is kept constant, motors 13 and 14 are driven by an NC apparatus 15 in order to apply the relative movement control according to the configuration similar to that in machining between the wire electrode 1 and the workpiece 11. Said contact resistance is detected, and the signal of the result is applied to a head 20 to record it on a recording paper by means of a recording pen 21 for inspection of the machining position and accuracy.

Wire cut electric discharge machining electrode wire

Abstract: PURPOSE:To improve machining speed, by using a wire electrode in which a film of Al or alloy, contained with not more than 10% Zn to Al, is formed to the surface of a copper or copper alloy wire. CONSTITUTION:A strand (a) of Cu or Cu alloy in diameter of about 1mm. is fed from a supplying machine to pass through a degreasing tank 2, water tank 3, pickling tank 4 and water tank 5 then reach a plating tank 6. A film of Al or alloy, contained with not more than 10% Zn to Al, is formed to a surface of the strand (a) in the plating tank 6. The wire, after being processed work, is wound to a winding machine 9 through a water tank 7 and drying oven 8. This wire rod is finished to a desired diameter of about 0.1mm.-0.3mm. by the stretching work. Thickness of the film is preferable not more than 30mu, and the stretching work is difficult for the thickness if not less than 30mu. Such wire electrode is used to perform electric discharge machining, and its machining speed can be improved to about 20-40% as compared with the machining speed by a conventional electrode wire.

EDM Pulse generator with a variable output inductor for producing pulse with gradually rising edges

Abstract: An electrical discharge machine having a non-storage type power supply for generating working pulses to be applied across a gap between an electrode and a workpiece for cutting the workpiece comprises an induction coil for reducing the sharpness of the leading edge of the working pulses supplied from the power supply to obtain working pulses with a gradual rise. When electrical discharge machining is carried out using such pulses, the resulting concave portion produced by each pulse is shallower in depth and larger in diameter than those produced by conventional working pulses. As a result, the roughness of the machined surface becomes small.