Abstract: An electrical discharge machining method for automatically updating machining conditions so that the discharge state agrees with a target value and an electrical discharge machining apparatus for carrying out the method. Initial machining conditions, a target discharge state (e.g., normal discharge rate) and a constant for computing new machining conditions are set. A register for storing actual machining conditions is loaded with the initial machining conditions, and machining operation is started under these machining conditions. The deviation between detected data indicative of the discharge state and the target discharge state is obtained. The new machining conditions are obtained by adding the product of the deviation and the constant to the current machining conditions. These processings are repeated in succession, and the machining conditions are updated so that the discharge state agrees with the target discharge state. The target discharge state is obtained by test machining.

Abstract: An insulating condition detecting apparatus for a wire-cut electrical discharge machine in which insulation between a wire electrode and a workpiece is detected without rising any other special power source than a power source for machining. A voltage between the wire electrode (6) and the workpiece (6) is detected during a period. A switching element (3) for electrical discharge, formed of a semicondctor, is turned off and a switching element for charging is turned on to charge the capacitor. When the detected voltage is lower than a reference value, it is determined that the insulation between the wire electrode and the workpiece is unsatisfactory, and a dielectric breakdown signal is outputted.

Abstract: A method of displaying an operation history of a machine, which permits quick and proper investigation of the causes of troubles and trouble-shooting therefor. A processor of a numerical control device mounted on the machine writes a block number in a corresponding address region of a memory every time one block of a machining program is read out, and executes the block after an index indicating the address region to be stored with the next block number is determined (S1 to S4, S6). If the determined index exceeds a value indicating the last address region, the index is reset to a value indicating the first address region (S5).

Abstract: A wire-cut electric discharge machine, which displays a workable time (T) of a currently used wire electrode (2). A wire length when the wire is mounted on a bobbin (B1) and a wire feed speed are input through a manual input unit (7) and are stored in memory (6). During working (i.e., machining), a CPU (5) calculates a new, remaining wire length (L) from the wire length when the wire is mounted on the bobbin or a remaining wire length (L) and a wire feed speed (V) for predetermined time periods (step S1). A workable time (T) is calculated from the new, remaining wire length (L) and the wire feed speed (V) by the CPU (5), and is displayed by a display unit (8) (steps S2 and S3).

Abstract: A wire-cut, electric discharge machining power supply unit charges a capacitor (4) by a DC power source (2) via a switching element (1), and discharges the stored charges of the capacitor (4) between a workpiece (6) and a wire electrode (7) via another switching element (5). A single-polarity discharge current of a small pulse width is supplied between the wire electrode (7) and the workpiece (6). A series circuit of an impedance element (50, 80) other than a capacitance and a diode (51), is connected in a backward direction with respect to a capacitor charging voltage to effect recharging of the capacitor (4) with high efficiency.

Abstract: A wire EDM circuit uses a references voltage connected to a short circuit detector for comparing an average voltage with a reference voltage. Whenever the average voltage is below the reference voltage the numeric controller causes the pulse oscillator to stop generating a pulse stream. In order to also finish machine the workpiece a reference voltage switching circuit is used to decrease the reference voltage. There is also provided an internal signal blocking circuit to block an interval signal oscillator to stop generation of the pulse stream when the wire electrode is temporarily in contact with the workpiece or when phenomena similar to a short circuit occurs.

Abstract: In an electric discharge machining power source having a capacitor discharge circuit with a switching element, charging of a capacitor is stopped through an OR gate (G1), a NOR gate (G2) and a preamplifier (A1) in response to an output from a charge voltage detecting circuit (1) for generating the output when a charge voltage across the capacitor exceeds a reference voltage. At the same time, the switching element is turned on through a preamplifier (A2). The switching element is kept on through the OR gate (G1) and the preamplifier (A2) until a discharge current detecting circuit (4) detects the discharge current and stops generating the output. When the capacitor is completely discharged, the switching element is turned off. When a predetermined period of time has elapsed under the control of a monostable multivibrator (3), the capacitor is recharged.

Abstract: The present invention is directed to an arrangement for wire-cut, electric discharge machining in which the charged voltage of a capacitor is applied across a wire electrode and a workpiece and the terminal voltage of the capacitor is controlled to perform electric discharge machining of the workpiece at an increased cutting speed.A capacitor (15) for applying a voltage across a workpiece (16) and a wire electrode (17) for electric discharge machining is charged from a DC power source (11) via a transistor (13) serving as a switching element; a transistor (24) serving as an auxiliary switching element is connected in parallel to the transistor (13); and the terminal voltage of the capacitor (15) is detected to control the transistor (24), by which the terminal voltage of the capacitor (15) is maintained at an intermediate level (H1), lowering the mean working voltage.