Abstract:
A high-hardness and high-strength carbon material is produced by disposing a body of graphite carbon, e.g. precompacted graphite or a mass of powdery graphite carbon, of a predetermined shape and dimension in a collapsible receptacle shaped and dimensioned to tightly retain the body therein, the receptacle being collapsible at least one-dimensionally under external pressure while holding the body against expansion. High pressure is applied to the body while the body is heated to an elevated temperature and for a sufficient period such as to cause a central region of the body to be liquefied and the remainder thereof to be sintered. While under continuous pressure, the body is cooled to give in carbon material.
Abstract:
An EDM method and apparatus wherein a localized magnetic field is produced so as to be concentrated at least predominantly on a region of the EDM gap which constitutes only a limited portion of a preselected entire area of juxtaposition between the tool and workpiece electrodes. The region of concentration of the localized magnetic field is successively shifted to sweep it over the entire area of juxtaposition between the electrodes. A control device is provided to control at least one parameter of production and sweeping of the localized magnetic field in response to at least one process parameter of the EDM process.
Abstract:
An EDM method utilizing an improved tool electrode made of a sintered carbonaceous body consisting essentially of 50 to 90% graphitized carbon and the balance nongraphitized carbon uniformly distributed therein. The body may be prepared by sintering a mass of graphitized carbon particles and nongraphitized carbon particles mixed uniformly together in an optimum proportion under pressure. During sintering, the mass may be compressed bi-axially but is preferably tri-axially or isostatically compressed. The carbonaceous body of the invention may be prepared by sintering together graphitized carbon particles and a predecessor of the nongraphitized carbon, by sintering a uniform mixture of a predecessor of graphitized carbon and a predecessor of nongraphitized carbon. The predecessor of nongraphitized carbon is advantageously constituted by phenol and/or furan.
Abstract:
An EDM method and apparatus in which a continuous DC voltage is applied across the EDM gap via a first switch held conductive, and a stray capacitance distributed in the supply circuit including the EDM gap is recurrently charged and discharged to produce successive electrical discharges between the tool electrode and the workpiece. A gap sensor monitors the magnitude of high-frequency signals contained in the successive discharges and, when the sensed magnitude falls below a threshold level, provides a trigger signal which is used to turn on a second switch connected across the EDM gap in parallel with the DC source to short-circuit the EDM gap, thereby terminating the successive discharges. The conducting second switch serves to discharge the residual charge on the stray capacitance and prevents charge build-up thereon. Then the first switch may be turned off. The time interval in which the gap is free from current flow continues until the first switch is turned on following the turn-off of the second switch. The cycle is repeated.
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.
Abstract:
An inverter-type power supply circuit for electrical machining comprising a plurality of AD-DC-HF-DC (PULSE) inverters jointly connected between a common source of commercial alternating current and a single electrical machining gap. A common pulsing means is provided for the individual switches in these plural inverter circuits for providing thereto in unison a succession of time-spaced groups (Ton, Toff) of elementary signal pulses to provide across said gap concurrent occurring channels of time-spaced groups (Ton, Toff) of elementary machining pulses (.tau.on, .tau.off) which channels are superimposed upon one another across the machining gap. The plural inverter circuits include individual high-frequency transformers each of which, or a portion of which, has a plurality of settings for transforming the original voltage to a desired output voltage level which settings are selectively established to selectively establish the desired voltage and current characteristics of the superimposed elementary machining pulses in time-spaced groups.
Abstract:
A method of and apparatus for electrodepositing a metal onto a workpiece wherein an electric potential is applied between an anodic electrode and the cathodic workpiece in the presence of an electrodepositing solution. A narrow thermal light beam is directed onto the workpiece and intercepted by a localized area thereon to activate an interface between the area and the electrodepositing solution. The metal in the solution is thereby electrodeposited selectively on that localized area. The beam and the workpiece are relatively displaced to successively shift the area of interception of the beam until a desired surface region on the workpiece is electrodeposited. Preferably, the thickness of the solution traversed by the beam incident upon the localized area is limited not to exceed a preselected dimension. The apparatus preferably comprises a mirror for reflecting the beam from a source thereof which is fixed in position onto the workpiece and a drive unit for displacing the mirror to achieve the required displacement of the incident beam relative to the workpiece. A lens is disposed in the optical path for the beam and the position thereof is controlled to maintain its focal plane coincident with the beam-intercepting localized area.
Abstract:
An improved method of and apparatus for electrically machining a workpiece wherein the machining surface of an electrode is spacedly juxtaposed with the workpiece and supplied with a machining liquid. The liquid is carried into a machining gap between the electrode and the workpiece and a wave-emitting member with a continuous annular vibrant surface is disposed adjacent to the workpiece whereby to position the said surface to spacedly surround the electrode. Ultrasonic waves are produced with this surface by virtue of a mechanical vibratory activation of the member by a transducer and such waves are emitted against at least a portion of the machining electrode surface isotropically whereby to effect a uniform activation of the electrode surface and the machining liquid medium on the latter in the machining zone.
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.
Abstract:
A particulate mass to be sintered is imbedded in a mold which comprises a porous mass of particulate refractory material enclosed within a flexible membrane. Six press units are provided for applying compressive pressures externally to the mold, together or in sequence, whereby to subject the sinterable mass to pressures in the respective directions, under the control of a preprogrammed control unit which receives clock pulses from a source and stimulates the respective press units. A flexible heating coil imbedded in the mold is supplied with alternating current from a source to inductively heat up the sinterable mass and the adjacent mold material, to enable sintering to occur. The sinterable mass may have been precompacted into a self-supporting so-called "green compact", or it may be supported in a self-supporting shell carried within and forming part of the mold. The mold preferably comprises three layers having characteristics chosen so as to assist in heating up the sinterable mass uniformly.