Abstract: A method and apparatus for determining the amount of deflection, or curvature height, of an electrode wire during machining of a workpiece by the electrode wire in a travelling wire EDM apparatus. A parametr affecting the curvature height of the electrode wire is varied from a first value to a second value and the resulting variation .DELTA.f of the curvature height is measured. The measuring is effected by determining the difference between the length of the path travelled by the wire guide members and the length of the path travelled by the active portion of the wire. The ratio between the curvature height of the wire and the inverse of the relative variation of the parameter is subsequently determined. Preferably, a parameter independent of the machining speed is selected, such as the force of longitudinal traction exerted on the wire or the distance separating the two wire guide members.

Abstract: An apparatus and method for preventing machining errors due to changes in the inclination of the electrode wire in a travelling wire EDM apparatus wherein the electrode wire effectuates a cut on a workpiece such that the workpiece is provided with a bevel or taper on its peripheral surface. A test or trigger electrical pulse of low power is applied between the electrode wire and the workpiece in the machining zone and the location where the trigger electrical pulse occurs along the length of the electrode wire in the machining zone is detected and the trigger electrical pulse is converted into a machining electrical discharge, or not converted, according to the speed of feed of the electrode wire at such location while being displaced transversely along the cutting path in the course of a change of inclination of the electrode wire.

Abstract: In a travelling wire EDM apparatus having orientable swivelling wire guide and support members, or wire guide heads, the orientation of each wire guide head is effected by a pair of hydraulic slave cylinders each connected to a master cylinder. Each master cylinder has an input member displaceable along one direction and the desire inclination of each wire guide head is the resultant of the composite motions of the output members of the corresponding slave cylinders.

Abstract: An EDM device includes two support bars bearing on the same reference surfaces as the workpiece. Gibs are provided which engage into driving units able to displace them axially while holding them at a small distance under one support bar. The other support bar carries the receiving units wherein the gibs engage at the end of their stroke. Each driving unit may push the gib engaged therein against the lower surface of the respective bar. Whenever one or several such gibs are stopped under a part cut out of the workpiece, the part will lie thereon and remains fixed even after the electrode has completed a closed path cutout by electroerosion separating the cut-out part from the workpiece. The cut-out part may then be automatically removed by means of a mobile member equipped with a suction cup.

Abstract: A device installed on a traveling wire EDM apparatus for straightening the electrode wire and providing the electrode wire with a needle point end for facilitating manual threading of the electrode wire through close tolerance closed wire guide members. The device takes the form of a pair of spaced-apart current conductive metallic studs, a heat shield being located at some intermediate portion between the metallic studs. The metallic studs are connected across a source of electrical power. A length of wire proximate its end is held manually over the metallic studs, with an intermediate portion of the wire disposed within the heat shield, and a pull is manually exerted on the wire beyond the metallic studs while the wire is being heated by electrical current flow through the wire between the two metallic studs. The wire is heat-straightened and ruptures at its portion within the heat shield, with sharp needle point ends being formed at the point of rupture.

Abstract: A method and apparatus for holding an electrically conductive workpiece in a machine tool by forming at least one positioning cavity or recess on a face of the workpiece by a holder having a tip used for machining the cavity or recess by a conventional EDM sinking operation. Subsequently to forming the cavity, the tip is used as one of the holding members for the workpiece. Two tips may be used to sink cavities or recesses on opposite surfaces of the workpiece, or the tips may take the form of fingers sunk into the workpiece from one side only. The tips form part of support members mounted on the end of displaceable arms for enabling the workpiece to be positioned relative to a tool or to be displaced. The tip-provided supports may be used for supporting a portion of the workpiece being cut off or severed from the workpiece.

Abstract: A contact device for an electrical current supply of an electrode wire operating in an electro-erosion machine having an electrical conducting part, mounted in free rotation and solidly attached to a shaft extending perpendicularly to the plane of rotation. The shaft is, preferably, also conducting and extends through a leakproof cavity, containing a conductive fluid, such as mercury for example. The conducting part is preferably a steel roller, provided either with a V-shaped groove on its periphery, or animated with a back and forth movement parallel at its axis of rotation.

Abstract: An EDM apparatus having a first support member for the workpiece and a second support member for the guide members of an electrode wire. A cross-slide provides relative linear motions between the two support members for effecting a cut in the workpiece by the electrode wire. A third support member carrying a form electrode tool is arranged to be selectively held stationary either relative to the first support member, by an appropriate first coupling member, or relative to the second support member, by a second coupling member. Under the first condition, the cross-slide provides the necessary relative linear displacements between the electrode wire and the form electrode tool for cutting the electrode tool by the electrode wire and, under the second condition, the same cross-slide provides the necessary displacements for sinking the electrode tool into the workpiece.

Abstract: The rethreading mechanism of a travelling wire EDM apparatus has a scrap wire disposal mechanism for disposing of the unusable length of electrode wire, or scrap, remaining in the machining zone after accidental rupture of the wire. The wire scrap disposal mechanism takes the form of a shaft having a bifurcated end defining tines between which the wire passes. Upon accidental rupture of the wire, the bifurcated shaft is automatically set in rotation such as to wind the length of wire between the shaft bifurcated end and the point of rupture of the wire in a bundle around the bifurcated end, and simultaneously exert a pull on a length of unused wire, which is also caused to wind around the shaft bifurcated end, such as to straighten the wire upstream of the bifurcated shaft. After cutting off the wire, the bundle of scrap wire around the bifurcated shaft is pushed off such as to fall in a disposal chute.

Abstract: In a travelling wire EDM apparatus, the electrode wire is divided into a plurality of sectors disposed along the active length of the electrode wire, and the numbers of electrical discharges occurring in each of the sectors from a predetermined starting time is detected. Those numbers are compared to reference values to determine the difference between the numbers of detected electrical discharges and corresponding reference values. In its simplest form, all the reference values are equal to the average value of the number of electrical discharges per sector. If one or more of the differences is higher than a predetermined threshold, an adequate modification of the machining parameters is effected as a function of the difference.

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.

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.

Abstract: An arrangement for applying an electromagnetic force on the electrode wire of a travelling wire EDM apparatus by passing through the workpiece an auxiliary current parallel to the current flowing through the electrode wire, in one direction or the other. The points of application of the auxiliary current on the surface of the workpiece are disposed opposite to the front of a cut relative to the electrode wire in order to obtain a resultant force which either pulls the electrode wire away from the front of the cut or draws it closer to the front of the cut.

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.

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.

Abstract: An EDM electrode wire changer has a plurality of conduits, one for each available electrode wire, all conduits converging towards the threading axis of a selected electrode wire through the workpiece or, alternatively, disposed substantially parallel on a slide that is indexable such as to dispose the outlet of a selected one of the conduits in alignment with the threading axis. A common motor-driven threading roller is disposed proximate the inlet of the conduits in a stationary position relative to the conduits, and a pinch roller for each wire co-operates with the threading roller for feeding the selected one of the wires through its corresponding conduit by forcing the selected wire against the peripheral surface of the common threading roller, while the other pinch rollers are remaining in a position away from the threading roller.

Abstract: A method and apparatus for polishing a workpiece by electrical discharges by way of an electrode tool, machining pulses of relatively low power being obtained from a machining pulse generator. A cross-slide table provides the workpiece with a translation cyclical motion during polishing. Input control circuits enable the machine operator to program a chosen speed of translation for the cyclical motion, the radius of circular translation and the time of duration of machining. A counter counts the number of cycles being effected and a discriminator stops the pulse generator as soon as the chosen number of desirable cycles is obtained, such number being inversely proportional to the amplitude chosen for the translation motion.

Abstract: An apparatus and method for improving the surface finish of a workpiece machined by an EDM apparatus having an electrode tool mounted in a tool holder insulated from the rest of the apparatus structure, the EDM apparatus comprising a pulse generator applying electrical discharges across the electrode tool and the workpiece, and wherein a parasitical capacitor is formed by the tool holder insulated from the rest of the apparatus. The parasitical capacitor, connected across the pulse generator output, is charged and discharged during operation of the pulse generator, and the discharge energy of the parasitical capacitor is added to the energy of the electrical discharge supplied by the pulse generator. For the purpose of obtaining a smooth surface finish on the workpiece with decreased energy of the machining electrical pulses, a compensating inductance is placed in series in the discharge circuit.

Abstract: A travelling wire EDM apparatus wherein a workpiece is cut by electrical discharges by a travelling wire electrode, relative motion of the workpiece and the wire electrode being controlled by a numerical control unit which, in addition, controls transverse oscillations of the electrode wire relative to the workpiece along the cutting path. The energy of the electrical discharges is varied as a function of the amplitude of the transverse oscillations of the electrode wire relative to the workpiece such as to obtain maximum electrical discharge energy when the amplitude of vibration of the electrode wire is at a minimum and minimum energy when the amplitude of vibration of the electrode wire is at a maximum.

Abstract: In a travelling wire EDM apparatus, the location of an electric discharge along the portion of the electrode wire in the machining zone between the electrode wire and the workpiece, in the course of a cut being effected on the electrode workpiece by electrical discharges, is measured by measuring the currents flowing through each of the two lines connecting one output of the pulse generator associated with the EDM apparatus to the electrode wire on one side and the other of the machining zone. The measured currents are added and subtracted and the position, or location, of an electrical discharge is determined by a signal proportional to the quotient of the difference by the sum of the currents.