Ateliers Des Charmilles S.a.

Charles Frei

Jean Pfau

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.

Process and apparatus for controlling the concentration of solid

A process and apparatus for monitoring the concentration of electrically conductive solid particles in suspension in a fluid by circulating the fluid between a pair of electrodes opposed surfaces disposed at a fixed distance from each other, the electrodes being connected across a DC power supply. Electrical discharges occur across the gap between the electrodes, and the concentration of solid particles is determined as an inverse function of the average delay time interval required for triggering the electrical discharges, which is in turn measured by counting the number of electrical discharges occurring within a predetermined time interval.

A method for machining materials difficult to cut by EDM conventional processes and consisting in providing contamination of the machining or dielectric fluid used in the course of electrical discharge machining with particles of a metal or metallic alloy of low vaporization temperature selected, for example, from the group consisting of zinc, cadmium, tin, lead, antimony and bismuth. The contamination particles are obtained directly from a surface coating placed directly on the electrode tool or from an additional piece of metal or metallic alloy which is electro-eroded at the same time as a cut is effected by the electrode tool in an electrode workpiece, and the contaminated fluid is circulated in the machining zone between the electrodes, the contaminated fluid facilitating the triggering of the electrical discharges in the machining zone and providing an increase of the machining rate, or material removal rate.

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Geneva, Switzerland

Charles Frei