Showing papers on "Electrical discharge machining published in 1980"

Method and apparatus for orienting the wire guidance heads on spark erosion cutting equipment for eroding with a great wire slope

Abstract: To permit machining of workpieces on spark erosion cutting equipment with large angles of inclination, the guidance heads which guide the wire electrode in the cutting zone with respect to the workpiece are pivotably arranged and controlled, by being mounted on individual gimbal suspensions so that it is possible to provide for a controllable slope angle up to large amounts. Individual drive motors control movement about the respective gimbal axes.

Wire electrode for cutting an electrode workpiece by electrical discharges

Abstract: A metallic wire, for cutting a workpiece by electrical discharge machining, coated with at least one layer of a metal having a low temperature of vaporization and a film of a metal oxide on the metal layer. The metallic coating is preferably made of zinc and is subjected to an oxidizing thermal or electrolytic treatment such as to form on the surface of the metallic layer a thin film of zinc oxide.

Method of and apparatus for electrical discharge machining a small and deep hole into or through a workpiece

Abstract: An improved method of and apparatus for the electrical discharge machining of a small and deep hole of a diameter of 1 mm or less and a depth-to-diameter ratio of at least 5 into or through a workpiece wherein a water machining fluid medium is used having a specific resistivity of at least 10 4 ohm-cm and is pumped through a tubular elongated electrode into the machining gap at a pressure of at least 20 kg/cm 2 , preferably 40 kg/cm 2 . An ultrasonic vibration is imparted to the elongated tubular electrode longitudinally thereof or transversely thereto.

Electrical discharge machine

Abstract: An electrical discharge machine control device which controls the displacement of the relative positions of a machining electrode and a workpiece so that the relative positions of the electrode and workpiece are changed not only in the main direction in which the workpiece is machined with the electrode but also in a plane perpendicular to the Z-axis without rotating the electrode while a predetermined machining discharge gap is maintained between the electrode and the workpiece The relative displacement in the perpendicular plane is displayed at an enlarged scale on an X-Y display device which may be a cathode-ray tube with the center of the displacement maintained at a predetermined origin point An optical encoder detects the movement in the X-Y plane to provide a detection signal The detection signal is applied through reversible counters to the horizontal and vertical deflection amplifiers of the display device

Apparatus and method for electrical discharge machining

Abstract: The disclosed method involves generating cartesian coordinate information representative of the electrode deflection from a rest position of a wire electrode electrical discharge cutting machine, feeding this information into an electronic processing system to convert it to appropriate control instructions, and then feeding the instructions into a drive system, which can then correct the relative positions of the wire electrode and the workpiece accordingly, so that the deflection of the wire electrode does not adversely influence the configuration of the cut made in the workpiece by it. The apparatus for performing the method comprises a wire electrode position pickup system, which can be a photoelectric system picking up the shadow of the wire or a system which measures the spacing between the wire and sensing electrodes by sensing the electrolytic current through a dielectric fluid which fills the space between them. The deflection information representative of the deflection is then fed as an input signal into an electronic processing unit which for each coordinate includes an analog computer with a summator, an inverter with amplification of one-half, a differentiator, and a division circuit to convert it to control instructions for a drive unit which makes the positional correction. The correction can be made by the main drive unit which moves the workpiece or by an auxiliary drive which moves the wire guides relative to the wire guide supporting structure.

Automatic electrode wire rethreading device for travelling wire EDM apparatus

Abstract: In a travelling wire EDM apparatus, the electrode tool in the form of a wire used for cutting an electrode workpiece is passed through a first zone in which the wire is straightened, preferably by exerting a pull on the wire while the wire is heated. The wire is subsequently cut-off at the bottom of the first zone, and the straightened portion of the wire is then threaded by a carriage through a hole pre-drilled in the workpiece, or through a cut in the workpiece in the event that the wire ruptures during machining, until the end of the wire is engaged in the wire conveyor mechanism.

Apparatus and process for preventing rupture of the wire electrode of an EDM travelling wire apparatus

Abstract: An arrangement for detecting abnormal concentration of electrical discharges between a travelling wire electrode and a workpiece in a travelling wire EDM apparatus The abnormal electrical discharge detector of the invention comprises a circuit measuring the voltage across a pair of contacts supplying machining current to the electrode wire The length of the electrode wire between the two contacts forms a pair of variable resistors connected in a branch of a Wheatstone bridge circuit The voltage measuring circuit, connected across a diagonal of the bridge, in turn controls some of the machining parameters such as to prevent damages, as for example rupture of the wire electrode, when an abnormal concentration of electrical discharges is detected at a given point of the machining zone between the wire electrode and the workpiece

EDM Process and apparatus for machining cavities and slots in a workpiece

Abstract: Process and apparatus for cutting by electrical discharge machining cavities and slots in an electrode workpiece by means of an electrode tool, the electrodes being displaced one relative to the other in translation along a predetermined path. The translation motion is controlled such as to maintain predetermined machining conditions in the machining zone between the electrodes, and for additionally displacing the electrodes relative to each other in a direction different from the direction of the cutting path. The additional relative displacement of the electrode may be linear, non-linear, slanted or curvilinear.

Process and apparatus for controlling the concentration of solid particles in suspension in an EDM machining fluid

Abstract: A method and apparatus for machining, by electrical discharges, an electrode workpiece by means of an electrode tool, wherein machining fluid supplied by a nozzle to the machining zone between the electrode tool and the electrode workpiece is returned to a tank and circulated by a pump from the tank to the nozzle through two lines, one provided with a filter and the other having no filter but controlling the flow of fluid therethrough and comprising a solid particle proportioning device. The flow rate and proportioning device is controlled by an electrical signal for regulating the concentration of solid particles in suspension in the fluid, and the adjustment for the concentration of solid particles is effected on the basis of measuring the average delay of triggering of the machining electrical discharges.

Servo system and method for controlling the gap spacing between a tool and workpiece electrodes in an EDM machine

Abstract: An improved servo system and method in an EDM machine for controlling the relative electrode displacement or the gap spacing between a tool electrode and a workpiece, wherein the electrodes are brought to a machining position to permit a succession of electrical discharges to be developed therebetween across the machining gap. A counter is used to count the number of machining pulses and, when the number reaches a value preset in conjunction with the machining area defined by the confronting electrodes, to provide an "advance" or "advance-enabling" signal. Only upon development of this signal or concurrent development of it and a usual servo "advance" signal from a gap sensor/servo signal generator responsive to a gap variable, e.g. gap voltage, a servo drive circuit acting on a motor or actuator for driving the movable electrode is actuated to allow the electrode to be advanced or stepped forward to a next machining position. The preset level of the discharge counter is varied from one value to another in response to a change in the machining area, setting or gap condition during the course of the machining operation.

Traveling wire EDM apparatus with automatic wire rethreading mechanism

Abstract: An automatic wire rethreading mechanism for traveling wire EDM apparatus wherein the workpiece is cut by electrical discharges by an electrode in the form of a wire, comprising a mechanism for automatically threading the electrode wire through a pre-drilled hole in the workpiece, the automatic wire threading mechanism being adapted to thread the wire at the beginning of a cutting operation and any time the electrode wire is ruptured in the course of a cutting operation. The position of the pre-drilled hole is memorized, as well as the relative position of the wire and workpiece at the instant of wire rupture. The workpiece and the electrode wire holders are returned to their start position along a predetermined path and, after threading the wire again through the pre-drilled hole, the electrode wire and the workpiece are displaced relative to each other, without applying electrical discharges between the electrodes, along the already cut path until the wire electrode and the workpiece are positioned relative to each other in the same position as occupied when the electrode wire ruptured.

Electric discharge machining apparatus

Abstract: An electric discharge machining apparatus for cutting and shaping a workpiece into an article having a desired configuration in which the period of time required until the speed of a table carrying the workpiece becomes constant is made quite short. Comparator means compares a gap voltage between a wire-shaped electrode and a workpiece with a reference voltage to produce an error voltage. In one embodiment, a non-linear amplifier is disposed between the output of the comparator means and the input of an integrator. In the integrator, a clamping diode is coupled across an integrating capacitor so as to prevent the output of the integrator from becoming negative.

Electrical discharge machining device

Abstract: PURPOSE:To enhance the accuracy of machining, by providing electrostrictive members that may be slightly displaced in the direction in which a detecting electrode approaches a machining electrode, at the front end of a position detecting member for detecting the relative position of the machining electrode and a workpiece, so that the contact of the machining electrode is detected to be controlled CONSTITUTION:A machining electrode 1 is removably attached to a quill 2, and a workpiece 3 is secured to a machining bed 4 A machining tank 5 surrounds the machining bed 4 and the workpiece 3, and machining liquid is reversed therein to such a depth that the workpiece 3 is submerged therein In this condition an electrical discharge machining is carried out Position detectors 7, 8 are positioned so that they have a predetermined positional relation with respect to the reference plane of the workpiece 3 The electrode 1 is relatively moved on the center axis between the position detectors 7, 8 The electrode 1 is moved by a motor driven device The feed control of the electrode 1 is turned into the control by electrostrictive members 74, 84 just before the position where the electrode 1 comes to be contact with detecting electrodes 73, 83, and therefore, the electrostrictive members 74, 84 are applied with a voltage Therefore, due to elongation of the members 74, 84 the detection and control of approach and contact of the electrode 1 may be carried out

Method of and apparatus for detecting gap conditions in EDM process with monitoring pulses

Abstract: Method of and apparatus for controlling electric discharge machining processes in which machining pulses are applied across a machining gap with a pulse duration and peak current preselected to attain a predetermined machining consequence or result. At least one monitoring pulse is interposed in the succession of machining pulses and is time-spaced from and totally independent of the machining pulses while being dimensioned to give rise to a current pulse in the machining gap. The current pulse is measured as to at least one characteristic and the gap condition is determined in response to this measurement. sp CROSS REFERENCE TO RELATED APPLICATION This application is a continuation of copending application Ser. No. 860,164 filed Dec. 13, 1977 (U.S. Pat. No. 4,236,057).

System for manufacturing tire molding metal molds with electrical discharge machining

Abstract: A system for manufacturing tire molding metal molds with electrical discharge machining is disclosed, which makes possible the rotation, longitudinal and cross feeding of a work table on which a workpiece to be machined into a tire molding metal mold is placed and the rotation, lifting and lowering of a machining head, whereby the workpiece is discharge-machined by feeding a discharge machining electrode in a plurality of different directions corresponding to a plurality of projections protruding essentially vertical to the tire molding surface of the tire molding metal mold to be machined, and by changing electrodes having such profiles as to prevent the excess metal removal of the projections in accordance with each of the electrode feeding directions.

Travelling wire EDM apparatus

Abstract: A correction system for a travelling wire EDM machine cutting a workpiece by means of a travelling electrode wire stretched between two guide members and comprising a pair of servo motors for effecting displacement of the guide members relative to their respective support arms, such as to incline the electrode wire relative to the workpiece for providing the cut in the workpiece with an appropriate predetermined conicity or draft. One of the servo motors providing such displacement is, in addition, controlled such as to compensate for thermally-induced expansions or contractions of one of the support arm guide members relative to the other.

Methods and apparatus for monitoring the condition of dielectric liquid in electric discharge machining

Abstract: Methods and apparatus for monitoring the condition of dielectric fluid used in EDM are described. A continuous sample of dielectric liquid is withdrawn from a tank containing the EDM electrode and workpiece and is passed between electrodes of a capacitance cell before being returned to the tank. The capacitance between the electrodes gives an indication of the amount of metal particles resulting from EDM in the dielectric liquid. In another arrangement a magnetic field is used to direct most ferrous particles through a capacitance cell or part of a capacitance cell while most non-ferrous particles pass through another cell or another part of the cell. Measurement of the capacities of the cells or parts of cells provides an indication of the relative amounts of ferrous and non-ferrous particles in the dielectric liquid. The relative concentrations of particles of different sizes can be measured by passing the sample dielectric through a number of cells with each cell having a different pore-size filter at its inlet. The capacitance of each cell then indicates the amount of particles within a predetermined range in the dielectric liquid.

Super-fine finish EDM method and apparatus

Abstract: An EDM method and apparatus wherein a tool electrode is spacedly juxtaposed with a conductive workpiece across a machining gap filled with a dielectric liquid and a succession of localized, time-spaced, repetitive and randomly dispersed machining electrical discharges are effected between the tool electrode and the workpiece across the machining gap to remove stock from the workpiece uniformly over the surface thereof juxtaposed with the tool electrode. The surface finish of the stock-removed surface of the workpiece is improved by discharging electrical charge stored due to a stray capacitance across the tool electrode and the workpiece, through an electrical shunt circuit in parallel with the machining gap immediately prior to initiation of each of the machining electrical discharges across the machining gap.

Process and apparatus for electrical discharge machining by means of a wire electrode

Abstract: A method and apparatus for cutting a workpiece by electrical discharges by means of a travelling wire electrode according to a path determined by a numerical control program without reducing the machining speed or the current flowing into the wire electrode. At least one of the support and guiding members of the wire electrode is displaced relative to the workpiece along a path resulting from shifting each point of the desired cutting path a predetermined distance in the direction of machining along a tangent to each point of such path. The angle between the tangent at each point of the path relative to the coordinate axes is determined, and each point of the path is shifted relative to the programmed path along coordinates having values proportional respectively to the sine and cosine of the angle.

Traveling-wire EDM method

Abstract: In an EDM method, a continuous wire electrode with an original radius is continuously transported through a machining zone of a workpiece. The machining zone is flushed with a liquid while a succession of electrical machining current pulses are passed between the electrode and the workpiece. Because of these machining pulses, discharge craters with raised formations are formed on the wire electrode. The method includes the step of controlling at least one parameter of the electrical machining current pulses so that the radius of the wire electrode at the location of the raised formations does not exceed the original radius of the wire electrode.

Electrical discharge machining apparatus

Abstract: A device adapted for use with electrical discharge machining apparatus generates tapped holes in a workpiece using a threaded, hollow carbon tool. The tool is releasably connected to a reversible hydraulic motor by a coupling which feeds dielectric fluid through the interior of the tool into the space between the machining tip of the tool and the workpiece. The motor is mounted on a vertically reciprocable slide arrangement carried by a support which is mounted on the head of the conventional electrical discharge machine. The tool extends downwardly through a threaded guide which is held in spaced relationship to the workpiece by the support, thereby allowing fluid emanating from the tip of the tool to carry machined fragments upwardly out of the tapped hole. The slide includes a slide plate mounted on a pair of upright guide posts carried by the support. The weight of the slide plate and the motor apply constant downward pressure on the tool, thereby precisely controlling the spacing between the tool tip and the workpiece, even during motor reversal. A plurality of aligning elements removably mounted on the support allow rapid set-up and alignment of the tool relative to the workpiece.

Guide unit for wireecut spark erosion electrode

Abstract: PURPOSE:To make a good machining liquid column which does not suffer from interference due to a liquid overflow, by providing a flow guide so that the machining column wrapping an electricity feed section and the flow of other liquid do not interfere with each other. CONSTITUTION:A cap 30 is provided with a skirt portion 32 as a flow guide to conduct a liquid flow such as an overflow except a liquid flow toward an electricity feed section. The skirt portion 32 is an annular projecting portion concentrical with a nozzle 30a. The liquid overflow A and a machining liquid column ejected from the nozzle 30a do not join each other and are surely prevented from interfering with each other. Therefore, the machining liquid column is protected from disturbance. Because the electricity feed section of a wire electrode is wrapped with the stable machining liquid column, good cooling and gaseous discharge prevention or chip removal are enabled and the wire electrode is protected from shapping.

Arc monitor for electrical discharge machining

Abstract: Apparatus for monitoring EDM is described in which the voltage across the gap between an electrode and a workpiece is passed through a filter which selects those frequencies which are present only during sparking across the gap. The voltage across the gap is also applied to a comparator which detects discharge across the gap by determining whether the gap voltage is between two levels. The proportion of discharge time in which arcs occur is derived by a time-divider circuit which receives signals after processing from the filter and the comparator.

Electric discharge machining method

Abstract: PURPOSE:To form a desired relief pattern on a curved surface by means of electrical discharge machining process by electrically discharging between a metallic flat plate base mold cut with a plane developing pattern having ruggedness corresponding to desired relief pattern and a workpiece to be machined. CONSTITUTION:When teeth 5a, 5b are formed on the outer periphery of a workpiece 2 to be machined, a metallic rack member 3 having projections 4a, 4b obtained by developing the shape of the teeth 5 on a plane is prepared, and there is electrically discharged between the workpiece 2 and the rack member 3. When the workpiece 2 is moved in the direction B while rotating the workpiece 2 in the direction A, the teeth 5a, 5b are sequentially formed. When a raised character A is formed on the peripheral surface of a workpiece 21 of cylindrical shape, there is electrically discharged between the metallic flat plate base mold 20 formed in recess with the character A and the workpiece 21 to then move the workpiece 21 in the direction D while rotating it in the direction C.

Method for assembling photographic self-processing apparatus

Abstract: A method for assembling photographic processing systems of the type for advancing integral, self-processable film units to the exterior of a camera while simultaneously spreading a fluid processing composition in a uniformly thin layer between selected layers of a film unit. A number of processing rollers which comprise the system are provided with a partially textured surface by using an electric discharge machining process having predetermined conditions, and then a number of test processing systems are assembled with these rollers and other pieceparts randomly selected from lots of all other pieceparts which comprise the system. Characteristic film units are processed through the test processing systems, and the fluid layer thickness in each of these film units is afterwards measured and compared with a predetermined standard. If the combination of test system parts provides acceptable fluid layer thickness control performance, the remaining pieceparts of each lot are used in combination with rollers having the predetermined texturing to manufacture additional systems. If the test system performance is not acceptable, the electric discharge machining process conditions are adjusted by a predetermined amount which is sufficient to effect minor changes in fluid layer thickness control that can result in acceptable performance. Rollers are then textured with the adjusted electric discharge machining process and systems are then assembled using the piecepart lots in combination with rollers having surfaces textured according to the adjusted electric discharge machining process.

Wire cut electric discharge machining control method

Abstract: A command average machining current It(n) corresponding to change of a workpiece thickness is given by the following equations: ##EQU1## wherein the reference Ia(n) designates an actual average machining current Ia(n) at the workpiece thickness (Tn); It(n) designates an average machining current of the control command; Fn designates an actual machining feed rate; Ia(o) designates an actual average machining current at the initiation of the machining; S(o) designates a machining width; and To designates a workpiece thickness. The command average machining current It(n) is compared with the actual average machining current and the electric condition is changed and controlled to approach the actual average machining current to the command average machining current It(n) thereby controlling the work groove width to be constant in an electric discharge machining of the workpiece with a wire electrode.