# US 6,720,516 B2 · apparatus for electric discharge micromachining of a micro-diameter hole > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,720,516 B2 - Document ID: US6720516B2 - Status: Granted - Kind: B2 - Application number: 10/017,364 - Filed: 2001-12-12 - Published: 2002-08-29 - Granted: 2004-04-13 - Earliest claimed: 2000-12-12 - Assignees: Matsushita Electric Industrial Co., Ltd. - Inventors: Yoshio Yamada; Takeshi Masaki; Toru Nakagawa; Hiroyuki Nakata; Hirofumi Yasumoto; Toshihiko Wada - Web page: https://patentgrep.com/patent/US6720516B2 ## CPC - B23H 1/022: {for shaping the discharge pulse train (B23H1/024 takes precedence)} - B23H 1/024: {Detection of, and response to, abnormal gap conditions, e.g. short circuits (preventing short circuits or other abnormal discharges by altering machining parameters using adaptive control B23H7/16)} - B23H 9/00: Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects (heat treatment by cathodic discharge C21D1/38) - B23H 2300/20: Relaxation circuit power supplies for supplying the machining current, e.g. capacitor or inductance energy storage circuits - 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 An electrode discharge machining apparatus includes a first holder for holding a workpiece to be subjected to electro discharge machining, an electrode provided opposing the workpiece held by the first holder, a capacitor for supplying electric charge to the electrode and the workpiece so as to generate pulse electro discharge between the workpiece and the electrode, a power source for applying a voltage to the capacitor, a switching element provided between the capacitor, and at least one of the electrode, the workpiece and the power source, a switch controller for controlling on and off of the switching element, a current detecting element for detecting a current flowing between the workpiece and the electrode, and a control unit for, based on the current detected by the current detecting element, judging whether or not a short circuit occurs between the workpiece and the electrode. When it is judged that a short circuit occurs between the workpiece and the electrode, the switch controller switches off the switching element for a predetermined time. Use macro to add file identifier. ## Claims ### Claim 1 An electro discharge machining apparatus, comprising: a first holder for holding a workpiece; a tool electrode arranged opposite to the workpiece; a capacitor charged by a power source device through a resistor; a current detecting element for detecting a short circuit; a switching element intervening a discharge circuit between the capacitor, and at least one of the tool electrode, the workpiece and the power source; a control unit for controlling switching timing in accordance with a result of detecting a short circuit, wherein a short circuit detection signal is input, the switching element is turned off and, after predetermined time, the switching element is turned on. ### Claim 2 (depends on 1) An electro discharge machining apparatus according to claim 1, further comprising: a drive control unit for controlling movement of the tool electrode, wherein the short circuit detection signal is input, the tool electrode is moved to increase a gap between the tool electrode and the workpiece. ### Claim 3 (depends on 1) An electro discharge machining apparatus according to claim 1, further comprising: a motor for rotating the tool electrode; and a second holder for holding the motor and the tool electrode, wherein the second holder is made of a low thermal expansive substance. ### Claim 4 (depends on 3) An electro discharge machining apparatus according to claim 3, wherein the coefficient of thermal expansion of the low thermal expansive substance is 5×10−6 or less. ### Claim 5 (depends on 3) An electro discharge machining apparatus according to claim 3, wherein the low thermal expansive substance is an invar alloy. ### Claim 6 (depends on 1) An electro discharge machining apparatus according to claim 1, further comprising: a motor for rotating the tool electrode; and a second holder for holding the motor and the tool electrode, wherein an thermal isolator is equipped between the motor and the second holder. ### Claim 7 (depends on 1) An electro discharge machining apparatus according to claim 1, further comprising: a motor for rotating the tool electrode; and a second holder for holding the tool electrode, wherein space is set between the motor and the second holder. ### Claim 8 An electro discharge machining apparatus, comprising: a first holder for holding a workpiece; a tool electrode arranged opposite to the workpiece; a capacitor charged by a power source device through a resistor; and a switching element intervening a discharge circuit between the capacitor, and at least one of the tool electrode, the workpiece and the power source; and a switch controller for controlling on and off of the switching element, wherein the switching element alternatively is turned on and off so that duration of the pulse electro discharge is less than or equal to a predetermined time. ### Claim 9 (depends on 8) An electro discharge machining apparatus according to claim 8, wherein the predetermined time is a time from the beginning of the pulse electro discharge to the onset of electrolysis in one of the tool electrode and the workpiece. ### Claim 10 (depends on 8) An electro discharge machining apparatus according to claim 8, further comprising: a motor for rotating the tool electrode; and a second holder for holding the motor and the tool electrode, wherein the second holder is made of a low thermal expansive substance. ### Claim 11 (depends on 10) An electro discharge machining apparatus according to claim 10, wherein the coefficient of thermal expansion of the low thermal expansive substance is 5×10−6 or less. ### Claim 12 (depends on 10) An electro discharge machining apparatus according to claim 10, wherein the low thermal expansive substance is an invar alloy. ### Claim 13 (depends on 8) An electro discharge machining apparatus according to claim 8, further comprising: a motor for rotating the tool electrode; and a second holder for holding the motor and the tool electrode, wherein an thermal isolator is equipped between the motor and the second holder. ### Claim 14 (depends on 8) An electro discharge machining apparatus according to claim 8, further comprising: a motor for rotating the tool electrode; and a second holder for holding the tool electrode, wherein space is set between the motor and the second holder.