# US 7,608,795 B2 · Device for machining by electroerosion > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,795 B2 - Document ID: US7608795B2 - Status: Granted - Kind: B2 - Application number: 10/551,688 - Filed: 2004-04-30 - Published: 2007-07-19 - Granted: 2009-10-27 - Earliest claimed: 2003-05-22 - Assignees: Charmilles Technologies S.A. - Inventors: Fabrice Jaques; Sebastian Dorthe; Maurizio Tognolini; Guy Demule; Ernesto Bühler - Web page: https://patentgrep.com/patent/US7608795B2 ## CPC - B23H 7/04: Apparatus for supplying current to working gap; Electric circuits specially adapted therefor - B23H 1/022: {for shaping the discharge pulse train (B23H1/024 takes precedence)} - B23H 2300/20: Relaxation circuit power supplies for supplying the machining current, e.g. capacitor or inductance energy storage circuits - B23H 2300/22: Circuits using or taking into account line impedance to shape the discharge pulse - B23H: WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL (processes for the electrolytic or electrophoretic production of coatings, electroforming, or apparatus therefor C25D; processes for the electrolytic removal of material from objects C25F; manufacturing printed circuits using precipitation techniques to apply the conductive material to form the desired conductive pattern H05K3/18) ## Abstract The electrical discharge machining device comprises a first voltage/current source (U1) for discharge initiation connected to the tool electrode (F) and a workpiece electrode (P) forming the poles of a machining gap (G) and a second voltage/current source (U2) that can be disconnected by way of two switches (SW1, SW2). Capacitive elements (C1, C5) are mounted in series in the lines (10, 11) connecting the first source to the poles of the machining gap (G). In addition, these poles can be connected by a self-induction coil (Lm) mounted in series with an adjustable DC source (Sm). Thanks to these features, the energy of the eroding discharges can be significantly reduced in order to obtain a superfine surface finishing process of high quality, while at the same time precisely controlling the mean voltage across the terminals of the machining gap. ## Claims ### Claim 1 An electrical discharge machining device comprising a tool electrode (F) and a workpiece electrode (P) forming the poles of a machining gap (G), at least one voltage/current source (U1) connected by an electrical circuit (E) to the tool electrode (F) and to the workpiece electrode (P) and configured for generating electrical pulses and for establishing the initiation of electrical discharges between the tool electrode (F) and the workpiece electrode (P), at least one capacitive element (C1) close to or within contacts (W1, W2) located between said electrical circuit (E) and the tool electrode (F), the capacitive element (C1) is connected in series between the source (U1) and one of the poles of the machining gap (G) wherein it prevents DC components of electrical pulses coming from the source (U1) from being applied across the machining gap (G) and to allow variable current components coming from the source (U1) to flow, wherein the total capacitance (Ceq) of said electrical circuit (E) is reduced with respect to the machining gap (G), wherein the tool electrode is a wire (F) and the capacitive element (C1) is formed by a wire guide (WG) one part of which, in contact with the wire (F), is made of insulating material and another part of which is made of conducting material. ### Claim 2 (depends on 1) The machining device as claimed in claim 1, further comprising a second capacitive element (C5) connected in series between a second pole (P2) of the first source (U1) and arranged close to the workpiece electrode (P). ### Claim 3 (depends on 2) The machining device as claimed in claim 2, further comprising at least one switch (SW3, SW4) installed across the terminals of the capacitive elements (C1, C5) and designed to short-circuit or to render active the capacitive elements across whose terminals it is installed. ### Claim 4 (depends on 1) The machining device as claimed in claim 1, wherein the workpiece electrode (P) is mounted on a holder (T) via an insulator (J). ### Claim 5 (depends on 1) The machining device as claimed in claim 1, wherein the source (U1) comprises a short-circuiting device for producing electrical pulses with steep voltage rising edge slopes. ### Claim 6 (depends on 1) The machining device as claimed in claim 1, wherein the source (U1) is configured so as to produce electrical impulses with a frequency in the range 0.1 to 10 MHz, with a voltage amplitude in the range 60 to 300 V and with a positive or negative voltage rising edge slope in the range 0.1 to 5 V/nS. ### Claim 7 (depends on 1) The machining device as claimed in claim 1, wherein a self-inductance element (Lm) is galvanically connected to the poles of the machining gap (G) ### Claim 8 (depends on 7) The machining device as claimed in claim 7, wherein an inductance value of said self-inductance element (Lm) is such that the resonance frequency (Fo) of the electrical circuit is low relative to the frequency of the electrical pulses of the first source (U1). ### Claim 9 (depends on 8) The machining device as claimed in claim 8, wherein the value of said inductance (Lm) is such that the ratio of the frequency of the electrical pulses to the resonance frequency (Fo) is in the range 50 and 150. ### Claim 10 (depends on 8) The machining device as claimed in claim 8, wherein the value of said inductance (Lm) is such that the ratio of the frequency of the electrical pulses to the resonance frequency (Fo) is in the range 10 to 500. ### Claim 11 (depends on 10) The machining device as claimed in claim 10, wherein an adjustable DC voltage source (Sm) is connected in series with the self-inductance element (Lm) between the two poles of the machining gap (G). ### Claim 12 (depends on 11) The machining device as claimed in claim 11, wherein a switch (SW5) is connected in series with the self-inductance element (Lm) between the poles of the machining gap (G).