Abstract: A process and apparatus for an EDM machine provided with an overcut drive mechanism for orbiting the electrode tool relative to the electrode workpiece in a cyclical motion, comprising a control for the orbital mechanism which varies the velocity of the cyclical orbital motion as a function of the difference between the orbital path actually obtained and a reference orbital path, such as to simultaneously provide a control of the workpiece shape and maintain the machining gap and, therefore, the machining current substantially constant.

Abstract: A control installation for two or more hydraulic turbines enabling switching between individual control of each turbine and common control of some or all of the turbines, without interruption of operation for adjustments.

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 3-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, such that the shape of the machined position is an image of the tool shape. The cyclic translational movements can be obtained with an eccentric member whose eccentricity relative to a shaft is controlled by limiting axial movement of the shaft at a position corresponding to a predetermined penetration.

Abstract: Process and apparatus for eliminating short circuits occurring in the machining zone between an electrode workpiece and an electrode tool in the course of an electrical discharge machining operation. Short circuits, caused by bridging of the electrodes by metallic particles, are burnt by an auxiliary high intensity electrical discharge across the gap between the electrodes applied after a predetermined time interval, or time delay, from the beginning of a normal current pulse.

Abstract: An arrangement for connecting the terminals of the pulse generator of an EDM apparatus across an electrode wire and an electrode workpiece for effecting a cut applied in the machining zone between the electrode wire and the electrode workpiece. The machining current pulses are fed across the machining zone through a pair of sliding contacts, a capacitor being connected across the sliding contacts. One of the sliding contacts is engaged with the electrode wire and the other is connected to the workpiece. The capacitor is alternatively charged by the pulse generator and discharged through a low inductance circuit, thus providing in the machining zone current pulses each of short duration and having a sharp and steep leading edge.

Abstract: An EDM apparatus for cutting a groove in the wall of a recess in an electrode workpiece by means of an electrode tool. One of the electrodes is mounted on a movable support displaceable along the feed axis and along a path in the plane perpendicular to the feed axis, the other electrode being mounted on a movable support displaceable on the feed axis from a pre-determined reference position.

Abstract: The present invention relates to a machining process especially suitable for facilitating the construction of large turbines wherein displaceable guide blades for directing fluid to the rotor have to be provided on the downstream side of the volute or spiral tank of the turbine. Hitherto the whole unit had to be machined and assembled in the workshop and then transported to site.

Abstract: A hydraulic machine including a turbine and a pump oriented for the same direction of rotation and axially spaced apart on a common shaft, and having a casing extending between the external turbine strut ring and the external pump strut ring in which a pump inverter is housed, the casing having an internal separating wall dividing it into two chambers, into one of which the pump inverter discharges.

Abstract: A process and apparatus for controlling the retraction of the electrode tool of an EDM machine such as to maintain the material removal rate to a value approaching the maximum theoretical value. The control system comprises monitoring the machining rate for providing an average value of the material removal rate during at least a time interval corresponding to a single retraction period of the electrode, and varying the frequency of subsequent retractions of the electrode as a function of that average value such as to consistently maintain a material removal rate which is self-adaptive and tends to reach a maximum theoretical value.

Abstract: A hydraulic installation includes a gate valve and an injector rectilinearly mounted in series in a water inlet conduit which feeds a turbine. The injector includes a central body portion in which first and second servo-motors are housed. The first servo-motor controls the tip of the injector and the second servo-motor controls the movement of the plug of the gate valve. A single crosspiece secures the injector to an outer annular casing and also absorbs hydraulic forces otherwise exerted on the gate valve and the injector.

Abstract: An apparatus for displacing at least one of the electrodes of an electrical discharge machine laterally in a plane perpendicular to the axis of relative longitudinal feed of the electrodes, with an amplitude proportional to the longitudinal displacement of the electrodes. The apparatus comprises a rotatable shaft longitudinally controlled as a function of the axial position of one of the electrodes. An eccentric member is driven in rotation by the shaft, and the amount of eccentricity of rotation of the eccentric member is controlled by a moveable camming member supported at three points, one of the points being a fixed pivot point on the axis of the shaft and the two other points having an axial position and a radial position varying as a function of the longitudinal displacement of the shaft and defining the amount of eccentricity of the eccentric member.

Abstract: A control system, in an EDM machine, for simultaneously displacing the electrode tool and the electrode workpiece relative to each other along both an axis of penetration of the electrode tool into the workpiece and a translation motion in a plane perpendicular to the axis of penetration of the electrode tool into the workpiece. The control system consists of logic circuitry providing a variable signal obtained by integrating as a function of time the difference between a signal representative of the machining condition and a reference signal, apportioning the variable signal between a first and a second electrical signal and interrelating the apportionment with a control of the relative position of the electrodes along the axis of penetration and of the eccentricity of the relative translation movement, respectively, as a function of the first electrical signal and of the second electrical signal.

Abstract: A process and apparatus for electrically machining an electrode workpiece by means of an electrode tool, in which the electrode workpiece is first machined by EDM by way of electrical discharges occuring across a dielectric fluid. The electrode workpiece is subsequently subjected to a finishing pass in the course of which it is machined by electrochemical machining (ECM) through a conductive electrolyte replacing the dielectric fluid. The machining phase by ECM is effected by means of the same electrode tool or by means of an electrode tool of the same dimensions as is used during the machining phase with EDM. During machining by EDM, the electrode tool is orbited, or translated, in a direction perpendicular to the axis of feed of the electrode tool relative to the electrode workpiece, with an amplitude larger than the amplitude during machining by ECM.

Abstract: The present invention is an EDM (Electrical discharge machining) process and apparatus for machining an electrode workpiece by means of an electrode tool wherein the electrodes are displaced relative to each other along a principal feed axis while, simultaneously, the electrodes are displaced relative to each other along an orbital path in a plane perpendicular to the principal feed axis, such as to produce between the electrodes a three-dimensional translation motion, and for providing between the electrodes an average machining gap wider than the gap width sustaining electrical discharges. The invention provides a control of the amplitude of the relative translation motion of the electrodes while displacing the direction of said motion as soon as a predetermined orbiting path limit is reached such as to allow a rapid increase of the gap between the electrodes when the electrode tool is retracted.

Abstract: A support and guiding arrangement for a wire electrode for electro-erosion machining apparatus comprising at least a bearing surface for the wire electrode disposed between the wire guides for damping the vibrations or oscillations of the wire unsupported length in the course of a single oscillation, thus preventing resonant oscillations of the wire electrode.

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, a method whereby 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 3-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 such that the shape of the machined portion is an image of the tool shape. The cyclic translational movements can be obtained with an eccentric member whose eccentricity relative to a shaft is controlled by limiting axial movement of the shaft at a position corresponding to a predetermined penetration.

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.

Abstract: A process and apparatus for monitoring the efficiency of an EDM machine by providing an electrical magnitude or signal representing the current flow actually used for machining or, in the alternative, the actual material removal rate. Several circuits are disclosed permitting to provide the operator of an EDM machine with a visual display of the practical efficiency of the machine during a machining operation.

Abstract: In an EDM process and apparatus, an arrangement for automatically correcting machining errors while effecting a cut in a workpiece by means of a wire electrode when the cutting path of the wire electrode relative to the workpiece is along a curve or an angle, for example, rather than along a straight line. The speed of relative displacement between the wire electrode and the workpiece electrode is automatically varied as a function of the shape of the cutting path, such that the distance between the longitudinal axis of the wire electrode and of one of the cut surfaces of the workpiece is maintained constant, irrespective of the curvature or angularity of the cutting path.

Abstract: A process and apparatus for achieving relative displacement between the electrode tool and the electrode workpiece of an EDM apparatus about a closed or looped path at a speed varying as a function of the machining gap width, such as to remove material from the machined surfaces at a substantially constant material removal rate.