JP5067951B2 - Die-sinker EDM - Google Patents

Description

  The present invention relates to a die-sinking electric discharge machining apparatus provided with a machining power supply apparatus having a booster power supply apparatus. In particular, the present invention relates to a sculpting electric discharge machining apparatus including a machining control device that controls switching between a main power supply device and a booster power supply device when a discharge current is amplified by the booster power supply device.

  Die-sinking electrical discharge machining is a process in which a spark electrode is repeatedly generated by applying a voltage pulse at a predetermined frequency to a machining gap formed by a tool electrode and a workpiece with the tool electrode and the workpiece facing each other. It is known as a metal processing method for removing a material from a workpiece by energy and processing a desired processing shape.

  Since the discharge energy for each discharge depends on the discharge current flowing between both electrodes of the tool electrode and the workpiece when the discharge occurs, the amount of discharge per discharge increases as the current of the discharge current pulse increases. Become more. Moreover, since the discharge trace becomes larger as the amount taken per discharge is larger, the processed surface roughness becomes rougher. Therefore, in order to shorten the machining time as much as possible, a discharge current pulse having a larger current value is supplied to the machining gap within a range in which the required machining surface roughness can be obtained.

  In the case of machining with a so-called general-purpose tool electrode having a shape reversed with respect to a target machining shape in each machining process, a tool electrode having a size corresponding to the machining area is used. When performing sculpting EDM with a relatively large tool electrode, from roughing to roughly remove the material from the unprocessed workpiece to finishing machining to reduce the surface roughness. Since there is a large difference in the amount taken between the machining steps, the machining power supply device is required to be able to supply a discharge current pulse from a small current value of several hundred mA to a large current value of several hundred A to the machining gap. .

  When the machining power supply device is configured to process with a single power supply device that substantially supplies a discharge current to the machining gap with a single discharge circuit, a discharge current pulse having a large difference in current value is generated with the same discharge circuit. Therefore, when processing is performed with a small discharge current, it may be impossible to stably supply a discharge current pulse having a waveform and a current value due to the influence of circuit elements of the discharge circuit. In addition, since a discharge circuit that can withstand a large current is provided, overall energy loss increases.

  For this reason, a sculpting electric discharge machining apparatus capable of machining using a large tool electrode generally compensates for a current deficient in the main power supply apparatus in a main power supply apparatus whose maximum current value that can be supplied is several tens of A. A booster power supply device is juxtaposed. The booster power supply devices are provided in a number corresponding to the required maximum current value. EDM EDM with machining power supply with booster power supply can be supplied simply by adding a booster power supply to the power supply installed in a small EDM EDM that processes relatively small machining shapes The maximum current value can be increased, which is advantageous in terms of design and manufacturing.

  The main power supply device and the booster power supply device have basically the same configuration except for differences related to constants of some circuit elements in the discharge circuit, such as protection resistance of the protection circuit. Therefore, although the patent document clearly showing the configuration of the sculpting electric discharge machining device provided with the machining power supply device having the booster power supply device is not confirmed, as the configuration of the machining power supply device in which a plurality of power supply devices are arranged in parallel, Reference is made to the electrical discharge machining apparatus disclosed in Patent Document 1.

  By the way, in the machining power supply device having the booster power supply device, when the discharge current is increased beyond the maximum current value that can be supplied by the main power supply device by adaptive control, or the current is supplied stepwise as disclosed in Patent Document 2. When supplying a gradually rising discharge current pulse with a peak current value larger than the maximum current value, the discharge current exceeds the maximum current value while the discharge current is supplied to the machining gap. It is necessary to turn on the booster power supply at the same time as shutting off the main power supply.

  For example, as shown in FIG. 3, when supplying a discharge current pulse with a smooth rise, a plurality of switching circuits of the main power supply device are selectively turned on to increase the current stepwise. When the maximum current value is to be supplied, the main power supply device is shut off as shown in FIG. 3A and at the same time the booster power supply device is turned on as shown in FIG. 3B. At this time, the waveforms in FIG. 3A and FIG. 3B show the continuity of the switching circuit in a step-like manner compared to the level of the parameter value IP of the machining conditions, and the waveform of the discharge current that actually flows through the machining gap is shown in FIG. Shown in 3D. Also, the voltage between the electrodes is shown in FIG. 3C, and the detection signal of the voltage between the electrodes is shown in FIG. 3E.

JP 63-123618 A Japanese Patent Publication No. 4-50122

  When the main power supply device and the booster power supply device are switched while the discharge current is flowing in the machining gap, it takes time for the current supplied from the booster power supply device to rise due to the characteristics of the booster power supply device that outputs a large current. At the same time as the main power supply is shut off, a large drop in current occurs during a short period immediately after the booster power supply is turned on. A discharge current pulse having a desired waveform cannot be obtained because the discharge current pulse is interrupted by a decrease and vibration of the discharge current. For this reason, the tool electrode is abnormally consumed or the processing speed is lowered, which significantly affects the processing result.

  In addition, since a counter electromotive force is generated when the plurality of switching elements of the main power supply device are turned off and the output voltage is cut off, an instantaneous drop occurs in the voltage between the electrodes in the machining gap. For this reason, a detection device that detects the voltage between the electrodes erroneously recognizes the voltage between the electrodes, and outputs a vibrational and unauthorized detection signal including a sudden large fluctuation in amplitude. As a result, the adaptive control for changing and setting the machining conditions in accordance with the machining status cannot be performed accurately, and the machining results are seriously affected.

  The present invention relates to a sculpture electric discharge machining provided with a machining power supply device having a booster power supply device capable of minimizing a rapid drop in inter-electrode voltage and a large drop in discharge current that occur when current is supplied from the booster power supply device. An object is to provide an apparatus. Other advantages of the present invention will be described in detail each time a specific embodiment is disclosed.

In order to solve the above-mentioned problem, an electric discharge machining apparatus of the present invention is an electric discharge machining apparatus provided with a machining power supply device (1) having a main power supply device (5) and a booster power supply device (6). A plurality of switching elements (TR1-TR16) of the power supply device (5) are selectively turned on / off to supply a discharge current to the machining gap and at least a maximum current value (imax) that can be supplied by the main power supply device (5). When supplying the current, a plurality of switching elements (TR32) of the booster power supply device (6) are supplied so as to supply the current of the maximum current value (imax) while supplying the discharge current from the main power supply device (5). selectively after turning on the maximum current value due to a reduction in current immediately after the booster power supply (6) is turned generated depending on the rising characteristics of the current supplied from the booster power supply (6) current error current which is the difference between the current value of the discharge current flowing in the actual machining gap and imax) is supplied from the primary power supply apparatus to replenish a current supplied (5) from the main power supply (5) Is provided with a machining control device (2) for selectively turning on / off the switching elements (TR1-TR16) of the main power supply device (5) so as to reduce the power consumption.

  Specifically, the above sculpted electric discharge machining apparatus has a current value when the machining control device (2) superimposes the current supplied from the booster power supply (6) on the current supplied from the main power supply (5). Switching of the main power supply device (5) so as to reduce the current supplied from the main power supply device (5) in a stepwise manner so that the sum of the current values becomes a required peak current value that matches the waveform of the desired discharge current pulse. The elements (TR1-TR16) are selectively on / off controlled.

Further, the electric discharge machining apparatus of the present invention selectively turns on and off the plurality of switching elements (TR1-TR16) of the main power supply device (5) based on the machining conditions for a predetermined first time (ta). Each time the current is increased by unit current value (ia) to supply a discharge current pulse with a smooth rise to the machining gap, and a current equal to or greater than the maximum current value (imax) that can be supplied by the main power supply device (5) is supplied. case, the discharge current from the main power supply maximum current value (5) unit current value to the (imax) (ia) low current first time from the time of supplying the (ta) the main power supply after (5) selectively turn on a plurality of switching elements (TR32) of the booster power supply (6) to supply a current of the maximum current value in a state where the supply (imax), is supplied from the booster power supply (6) Ru Error booster power supply generated depending on the rising characteristics of the flow (6) is the difference between the current value of the discharge current flowing in the actual machining gap between the maximum current value (imax) by reduction immediately after the current is turned A predetermined second time such that a current lower than the maximum current value (imax) corresponding to the current value (ie) by a predetermined first current reduction value (ib) is supplied from the main power supply device (5). (Tb) The current supplied from the main power supply device (5) is decreased after that , and then predetermined every third time (tc) until the rise time (td) of the current supplied from the booster power supply device (6) elapses. The current supplied from the main power supply (5) is decreased stepwise by the second current reduction value (ic) of the current and gradually changes depending on the rising waveform of the current supplied from the booster power supply (6). error current (ie) Processing for selectively turning on / off the switching elements (TR1-TR16) of the main power supply device (5) so as to increase the current by unit current value (ia) at the same time as replenishing with the current supplied from the main power supply device (5). A control device (2) is provided.

  The above sculpted electric discharge machining device is used until the machining control device (2) reaches the peak current value (ipeak) according to the machining conditions after the rise time (td) of the current supplied from the booster power supply device (6). The switching elements (TR1-TR16) of the main power supply device (5) are selectively controlled to be turned on / off so as to increase the current by a unit current value (ia) every first time (ta).

  Since the electric discharge machining apparatus of the present invention supplements a decrease in current during the rising period of the current supplied from the booster power supply device when the booster power supply device is turned on, the current of the discharge current pulse is reduced. A discharge current pulse having a desired waveform can be obtained without a significant decrease. As a result, a desired processing result can be obtained. In addition, since it becomes possible to turn on the booster power supply without shutting off the main power supply, there is no instantaneous drop in the voltage between the electrodes due to the counter electromotive voltage, and the detection device can output a correct detection signal. . As a result, adaptive control can be accurately performed with a sculpting electric discharge machining apparatus including a machining power supply device having a booster power supply device, and excellent machining results can be obtained.

It is a block diagram which shows the outline | summary of the process power supply apparatus and process control apparatus which are provided in the profile electric discharge machining apparatus of this invention. It is a timing chart which shows the conduction | electrical_connection state of a switching circuit, the voltage between electrodes, and the waveform of a discharge current pulse in the die-sinking electrical discharge machining apparatus of this invention. It is a timing chart which shows the waveform of the detection signal of the conduction | electrical_connection state of a switching circuit, an interelectrode voltage, a discharge current pulse, and an interelectrode voltage in the conventional sculpture electric discharge machine.

  FIG. 1 shows the overall configuration of a machining power supply device and a machining control device. The die-sinking electric discharge machining apparatus includes a main machine including a driving device (not shown), a power supply control device, and a machining fluid supply device. The power supply control device includes a numerical control device, a drive control device, a machining control device, and a machining power supply device. The machining power supply device 1 is operated by the machining control device 2. The tool electrode 3 and the workpiece 4 are attached to the machine body side. The machining power supply device 1 intermittently applies a voltage pulse to a machining gap formed by the tool electrode 3 and the workpiece 4 and repeatedly supplies a discharge current pulse to the machining gap.

  The machining power supply device 1 includes a main power supply device 5 and a booster power supply device 6. The booster power supply 6 augments the current exceeding the maximum current value that can be supplied by the main power supply 5. A plurality of booster power supply devices 6 can be added corresponding to the required maximum current value. The booster power supply device 6 is provided in parallel to the main power supply device 5, and is connected in series between the electrode of the tool electrode 3 and the workpiece 4. Therefore, the main machining discharge circuit including the main power supply device 5 and the current increasing discharge circuit including the booster power supply device 6 share only between the electrodes including the tool electrode 3 and the workpiece 4, and substantially. Formed independently.

In the sculpture electric discharge machining apparatus of the embodiment, when machining only with the discharge current supplied from the main power supply device 5, the booster power supply device 6 is completely removed from the main power supply device 5 by a mechanical switch such as a relay switch 7. It is made to separate. Therefore, the discharge current supplied from the main power supply circuit is not affected by the current increasing discharge circuit including the booster power supply device 6, and particularly when a relatively small discharge current is supplied for processing, a discharge current having a desired waveform is obtained. This is advantageous in that the pulse is supplied stably.

  The main machining discharge circuit includes the main power supply device 5, the polarity switching device 51, the inter-electrode wire 52, and the gap between the tool electrode 3 and the workpiece 4 formed in the machining gap. The main power supply device 5 and the polarity switching device 51 are provided on the power supply control device side. The power control device side and the machine main unit side are connected by an output cable 53 such as a coaxial cable. A protection circuit 54 including a protection resistor having a predetermined resistance value is provided between the main power supply device 5 and the polarity switching device 51.

  The discharge circuit for increasing current includes the booster power supply device 6, the polarity switching device 61, the interelectrode line 62, and the interelectrode. The booster power supply device 6 and the polarity switching device 61 are provided on the power supply control device side. The power supply control device side and the machine main unit side are connected by an output cable 63. A protection circuit 64 including a protection resistor having a predetermined resistance value is provided between the booster power supply device 6 and the polarity switching device 61.

  The main power supply device 5 is composed of a plurality of power supply units. Each of the plurality of power supply units includes a DC power supply PS, a plurality of switching circuits SC connected in series to the DC power supply PS and in parallel with each other, and a reverse current blocking diode provided in series between the plurality of switching circuits SC and the poles. DR.

  The main power supply device 5 in the embodiment has three power supply units. The first power supply unit 10 and the second power supply unit 20 do not include a current limiting resistor that defines a peak current value in each of the switching circuits SC1 to SC16, and each switching element TR1 to TR16 is caused to respond to the detected current. A current having a peak current value determined by a specified current value applied to the switching circuits SC1 to SC16 is supplied. The third power supply unit 30 includes a series circuit in which each switching circuit SC0.5R-SC8R includes a switching element TR0.5R-TR8R and a current limiting resistor RS0.5-RS8 that defines a peak current value.

  The first power supply unit 10 includes a variable DC power supply PS1 of 60V to 120V, a plurality of switching circuits SC1-SC8 provided in series between the DC power supply PS1 and the poles, and the switching circuits SC1-SC8 and the poles. And a reverse current blocking diode DR1 provided in series. Switching circuits SC1-SC8 are connected in parallel to each other. The plurality of switching circuits SC1-SC8 include switching elements TR1-TR8 connected in series to DC power supply PS1 and a detection resistor (not shown).

  The second power supply unit 20 has basically the same configuration as the first power supply unit 10. The second power supply unit 10 includes a DC power supply PS1 common to the first power supply unit 10, a plurality of switching circuits SC16 provided in series between the DC power supply PS1 and the poles, and the switching circuit SC16 and the poles. And a reverse current blocking diode DR2 provided in series. The plurality of switching circuits SC16 are connected in parallel to each other. Switching circuit SC16 includes a switching element TR16 connected in series to DC power supply PS1 and a detection resistor (not shown).

  The plurality of switching elements TR1 to TR16 are selectively controlled to be turned on and off in a binary count manner. The first power supply unit 10 can supply the current from IP1 to IP16 with the parameter values of the processing conditions by the combination of the switching circuits SC1 to SC8. The second power supply unit 20 basically supplies a current of IP16 by turning on the plurality of switching circuits SC16. Therefore, the first power supply unit 10 and the second power supply unit 20 can supply the current from IP1 to IP32 in the unit of the parameter value IP1 in the combination of the switching circuits SC1-SC16.

  The third power supply unit 30 is applied to processing with a relatively small discharge current. The third power supply unit 30 includes a variable DC power supply PS2 of 60V to 200V, a plurality of switching circuits SC0.5R-SC8R provided in series and in parallel between the DC power supply PS2 and the poles, and switching circuits SC0. 5R-SC8R and a backflow prevention diode DR3 provided in series between the poles. Switching circuits SC0.5R-SC8R are series circuits of switching elements TR0.5R-TR8R and current limiting resistors RS0.5-RS8 having a predetermined resistance value for defining a peak current value and supplying a constant current. It becomes.

  The plurality of switching elements TR0.5R-TR8R are selectively turned on and off in a synchronous manner by a binary count method. The third power supply unit 30 can supply a current having a parameter value IP0.5 from the switching circuit SC0.5R. Further, the current from IP1 to IP16 can be supplied in the unit of the parameter value IP1 by the combination of the switching circuits SC1R to SC8R.

  In addition to the power supply unit, a power supply unit that forms an attached discharge circuit can be added to the main power supply device 5. Alternatively, the attached discharge circuit can be incorporated in the circuit of the power supply unit. For example, a high voltage superposition circuit comprising a series circuit of a 270V high voltage DC power supply, a switching element, and a current limiting resistor is provided.

  The booster power supply device 6 shares only the poles including the main power supply device 5, the tool electrode 3, and the workpiece 4, and is arranged substantially in parallel. The booster power supply device 6 includes a variable DC power supply PS3 of 60V to 120V, a plurality of switching circuits SC32 provided in series between the DC power supply PS3 and the poles, and provided in series between the switching circuit SC32 and the poles. And a reverse current blocking diode DR4. Each switching circuit SC32 is connected in parallel to each other. Each switching circuit SC32 includes a switching element TR32 connected in series to DC power supply PS3 and a detection resistor (not shown).

  The plurality of switching elements TR32 are selectively controlled to be turned on and off in a binary count manner. The booster power supply device 6 basically turns on the plurality of switching elements TR32 simultaneously to turn on the plurality of switching circuits SC32 and supplies the current of the parameter value IP32 to thereby supply the first power supply unit of the main power supply device 5. 10 and the output current of the second power supply unit 20 are augmented.

  The detection device 8 includes a detection circuit 81 provided at a position as close as possible to the machining gap formed by the tool electrode 3 and the workpiece 4. The detection circuit 81 includes a detection resistor 82 and outputs a voltage across the detection resistor 82 to the detection device 8. The detection device 8 inputs the inter-electrode voltage obtained by the detection circuit 81 and outputs a plurality of types of detection signals to the machining control device 2. The detection device 8 smoothes and converts the voltage between the electrodes into a digital signal, and outputs voltage waveform, voltage level, or average machining voltage data as a detection signal, or outputs a comparison signal as a detection signal compared with the set reference data. To do.

  The processing control device 2 includes a setting device 40, a pulse generator 50, and a gate circuit 60. The machining control device 2 sets the machining condition data output from the numerical control device in the setting device 40. The pulse generator 50 outputs a command signal corresponding to the processing condition data set in the setting device 40 to the gate circuit 60. The gate circuit 60 outputs a gate signal to each switching element TR of the main power supply device 5 and the booster power supply device 6 based on a command signal output from the pulse generator 50.

  The gate circuit 60 is detected through a detection resistor (not shown) in each of the switching circuits SC1 to SC32 in the first power supply unit 10, the second power supply unit 20, and the booster power supply device 6 of the main power supply device 5 that does not include a current limiting resistor. A switching signal TR1- is inputted by a logical product of a command signal output from the pulse generator 50 and a comparison signal. The TR 32 is turned on and off at high speed, and currents having peak current values determined by the specified current values are supplied from the switching circuits SC1 to SC32.

  The machining control device 2 applies each of the plurality of switching circuits SC in the first power supply unit 10 to the third power supply unit 30 in the main power supply device 5 based on the data of the set machining conditions output from the numerical control device. The switching element TR provided is selectively turned on and off in a synchronous manner by a binary count method, and a discharge current according to the machining conditions is supplied to the machining gap.

  The machining control device 2 turns on / off each switching element TR in response to a detection signal output from the detection device 8 indicating the occurrence of discharge, and the pulse width of the discharge current pulse is made constant according to the on time of the machining conditions set. To be. Further, the machining control device 2 changes the peak current value of the discharge current according to the machining conditions in response to the detection signal indicating the machining state output from the detection device 8, or interrupts the supply of the discharge current. Alternatively, the machining control device 2 changes and sets the reference value in adaptive control in response to a detection signal indicating the voltage level of the interelectrode voltage output from the detection device 8.

  The processing control device 2 switches the variable DC power supply PS between the main power supply device 5 and the booster power supply device 6, switches the polarity of the polarity switching device 51 or the polarity switching device 61, and turns on / off the booster power supply device 6 by opening and closing the relay switch 7. Alternatively, the circuit element or circuit device in the discharge circuit is operated such as switching of a variable resistor (not shown) and turning on / off of the inductance element.

  The processing control device 2 supplies the discharge current from the main power supply device 5 without shutting off the main power supply device 5 when attempting to supply a discharge current pulse that is greater than or equal to the maximum current value that can be supplied by the main power supply device 5. In this state, the plurality of switching elements TR32 of the booster power supply device 6 are selectively turned on. Then, an error depending on the rising characteristic of the current supplied from the booster power supply device 6 after a delay time shorter than the time from when the booster power supply device 6 is turned on until the discharge current actually flowing through the machining gap reaches the maximum current value. The switching elements TR1-TR16 of the main power supply device 5 are selectively turned on / off so that the current is supplemented with the current supplied from the main power supply device 5.

  Specifically, the machining control device 2 determines that the sum of the current values actually flowing in the machining gap when the current supplied from the booster power supply device 6 is superimposed on the current supplied from the main power supply device 5 is a desired discharge current pulse. The switching elements TR1-TR16 of the main power supply device 5 are selectively turned on / off so that the current supplied from the main power supply device 5 is reduced in steps so that the required peak current value conforming to the waveform of FIG. To adjust the waveform of the discharge current pulse.

  When supplying the discharge current pulse having a smooth rise, the machining control device 2 determines in advance the plurality of switching elements TR1-TR16 of the main power supply device 5 in accordance with the rising waveform of the desired discharge current pulse based on the machining conditions. The on-off control is selectively performed by shifting the time every predetermined first time, and the current is increased by the unit current value every first time in accordance with the slope of the rising waveform of the desired discharge current pulse.

  When trying to supply a smooth discharge current pulse that rises above the maximum current value that can be supplied by the main power supply device 5, the machining control device 2 has a unit current value lower than the maximum current value from the main power supply device 5. The current corresponding to the maximum current value is obtained by selectively turning on the plurality of switching elements TR32 of the booster power supply device 6 while the discharge current is supplied from the main power supply device 5 after the first time from when the current is supplied. Is supplied from the booster power supply device 6.

  The machining control device 2 supplies the maximum current after a predetermined second time which is a delay time shorter than the time from when the booster power supply device 6 is turned on until the discharge current actually flowing in the machining gap reaches the maximum current value. A current corresponding to the error current value generated depending on the rising characteristic supplied from the booster power supply device 6 that is lower by the first current reduction value set in advance than the value is supplied from the main power supply device 5. The current supplied from the main power supply 5 is reduced.

  Next, the machining control device 2 superimposes the error current value and the incremental current value that increases by the unit current value every first time until the rise time of the current supplied from the booster power supply device 6 elapses. The current supplied from the main power supply 5 is decreased stepwise by a second current reduction value set in advance every predetermined third time that is predetermined in accordance with the slope of the change in current, thereby causing an error current. Are supplemented with the current supplied from the main power supply device 5 and at the same time, the switching elements TR1 to TR16 of the main power supply device 5 are selectively turned on / off so as to increase the current by a unit current value.

  Subsequently, the machining control device 2 actually processes the current supplied from the booster power supply device 6 on the current supplied from the main power supply device 5 after the rise time of the current supplied from the booster power supply device 6. The plurality of switching elements TR1 to TR16 of the main power supply device 5 are selectively shifted on and off at each first time until the discharge current flowing in the gap reaches the peak current value according to the processing conditions, and the desired discharge is performed. The current is increased by a unit current value every first time in accordance with the slope of the rising waveform of the current pulse.

  Then, the machining control device 2 maintains the peak current value until the on-time according to the machining condition is reached after the discharge current has reached the peak current value according to the machining condition, and supplies the discharge current. All the switching elements TR1 to TR32 of the main power supply device 5 and the booster power supply device 6 are turned off to stop the supply of the discharge current, and a discharge current pulse having a smooth desired rise is supplied to the machining gap.

  FIG. 2 shows a waveform of a discharge current pulse in which a current value larger than the maximum current value that can be supplied by the main power supply device is set as a processing condition. The waveforms in FIGS. 2A and 2B show the continuity of the switching circuit in a step-like manner by comparing the level of the parameter value IP of the machining conditions. The waveform of the discharge current that actually flows through the machining gap is shown in FIG. 2D. It is. Also, the interelectrode voltage is shown in FIG. 2C. Hereinafter, the operations of the machining control device 2 and the main power supply device 5 and the booster power supply device 6 when the discharge current pulse having a peak current value exceeding the maximum current value that can be supplied smoothly by the main power supply device is supplied will be described. Explained.

  The machining control device 2 causes the pulse generator 50 to output a command signal for commanding on / off of the switching element after the off time according to the machining conditions set in the setting device 40. Based on the command signal, the gate circuit 60 of the machining control device 2 outputs a gate signal to the switching element TR1 of the switching circuit SC1 in the first power supply unit 10 to turn on the switching element TR1 and to bring the switching circuit SC1 into a conductive state. To do.

  When the switching circuit SC1 becomes conductive, the voltage of the DC power source PS1 is applied to the machining gap as shown in FIG. 2C, and the voltage between the electrodes rises to the voltage of the DC power source PS1. A discharge occurs between both electrodes of the tool electrode 3 and the workpiece 4 after an irregular no-load time tw after the voltage is applied to the machining gap, and a current starts to flow between the electrodes through the switching circuit SC1. When a discharge current flows between the electrodes, the voltage between the electrodes drops and reaches a constant discharge voltage. When the inter-electrode voltage drops below the reference voltage, the detection device 8 outputs a detection signal indicating the occurrence of discharge to the pulse generation device 50.

  The pulse generator 50 starts counting the on time ton according to the machining conditions set in the setting device 40. The switching element TR1 is repeatedly turned on and off in response to the detected current of the switching circuit SC1 so that the peak current value according to the specified current value is maintained, and the current of the specified current value is supplied from the switching circuit SC1. As a result, the machining power supply device 1 supplies a current having a parameter value IP1 corresponding to the unit current value ia to the machining gap.

  The pulse generator 50 outputs the next command signal after a predetermined first time ta after the occurrence of discharge. The gate circuit 60 outputs a gate signal to the switching element TR2 of the switching circuit SC2 in accordance with the command signal to bring the switching circuit SC2 into a conductive state and stops outputting the gate signal of the switching element TR1 to make the switching circuit SC1 nonconductive. To do.

  The switching element TR2 is repeatedly turned on and off in response to the detected current of the switching circuit SC2 so that the peak current value according to the specified current value is maintained, and the current of the specified current value is supplied from the switching circuit SC2. As a result, the machining power supply device 1 supplies a current having a parameter value IP2 to the machining gap.

  The pulse generator 50 outputs the next command signal after a first time ta after the switching circuit SC2 is turned on. The gate circuit 60 outputs a gate signal to the switching element TR1 of the switching circuit SC1 according to the command signal to turn on the switching circuit SC1, and keeps outputting the gate signal of the switching element TR2 to turn on the switching circuit SC2. To do.

  Since both the switching circuit SC1 and the switching circuit SC2 are in a conductive state, currents having specified current values are supplied from the switching circuit SC1 and the switching circuit SC2, respectively. The switching circuit SC1 supplies a current having a parameter value IP1 corresponding to the unit current value ia. The switching circuit SC2 supplies a current having a parameter value IP2 corresponding to a current value that is twice the unit current value ia. As a result, the machining power supply device 1 supplies a current having a parameter value IP3 corresponding to a current value three times the unit current value ia to the machining gap.

  The first time ta and the unit current value ia are determined corresponding to the slope of the rising waveform of the desired discharge current pulse. However, the unit current value ia is basically set to the current of the parameter value IP1, which is the minimum current value that can be supplied by the main power supply device 5, unless there is a special reason for obtaining an arbitrary waveform more freely. Is done. Therefore, the first time ta substantially determines the rising waveform of the discharge current pulse. In the embodiment, the first time ta is set to 2 μs.

  The pulse generator 50 in the embodiment in which the first time ta is set to 2 μs and the unit current value ia is set to the current of the parameter value IP1 outputs a command signal every 2 μs, and a plurality of switching of the main power supply device 5 is performed. The elements TR1 to TR16 are selectively turned on and off in a time-shifted manner in a binary count manner, and the discharge current supplied to the machining gap by the combination of the switching circuits SC1 to SC16 to be conducted is stepped by the parameter value IP1. Raise. As a result, the discharge current that actually flows between the electrodes gradually rises as shown in FIG. 2D.

  When trying to supply a smooth discharge current pulse that rises above the maximum current value imax that can be supplied by the main power supply device 5, a current having a unit current value ia lower than the maximum current value imax was supplied from the main power supply device 5. After a first time ta, a booster power supply is supplied in a state where a gate signal is output from the pulse generator 50 to the plurality of switching elements TR32 of the booster power supply device 6 through the gate circuit 60 and a discharge current is supplied from the main power supply device 5. The plurality of switching elements TR32 of the device 6 are selectively turned on, and a current corresponding to the maximum current value imax is supplied from the booster power supply device 6.

  The maximum current value imax that can be supplied by the main power supply device 5 in the embodiment is the current of the parameter value IP32. Therefore, as shown in FIG. 2, the current is supplied from the main power supply 5 by increasing the parameter value IP1 step by step every 2 μs, and the main power supply 5 supplies the IP31 lower than the parameter value IP32 by the parameter value IP1. The switching elements TR32 are all turned on 2 μs after the current is supplied, the booster power supply device 6 is turned on, and the current of the parameter value IP32 starts to flow from the booster power supply device 6 to the machining gap.

  As shown in FIG. 2A, the pulse generator 50 outputs a command signal after a predetermined second time tb to turn on / off the switching elements TR1-TR16 of the main power supply device 5 and to control a plurality of switching circuits SC1-SC16. From the main power supply 5 so that a current lower than the maximum current value imax by a predetermined first current reduction value ib is supplied from the main power supply 5. Reduce the current supplied.

  A rise time td of about several tens of μs is required until the current supplied from the booster power supply 6 rises to the peak current value according to the specified current value of the booster power supply 6, specifically, the current of the parameter value IP32. Therefore, during the rise time td, the current value of the discharge current that actually flows between the electrodes is a value obtained by superimposing the current during the rise of the booster power supply device 6 on the current supplied from the main power supply device 5. Therefore, as shown in FIG. 3D, there is an error current value ie depending on the rising characteristics of the current supplied from the booster power supply device 6 with respect to the current value that is assumed ignoring the rising time td.

  From this, it can be said that when the error current value ie is supplemented with the current supplied from the main power supply device 5, the discharge current that actually flows in the machining gap becomes the required current value. The peak current value required when the booster power supply device 6 is turned on is the maximum current value imax. Therefore, the first current reduction value ib can be determined by subtracting the error current value ie from the maximum current value imax. The rise characteristic of the current supplied from the booster power supply device 6 mainly depends on the characteristics of the discharge circuit for increasing current including the booster power supply device 6, the material of the tool electrode 3 and the workpiece 4, and the processing area. Therefore, the first current reduction value ib is set based on the actual error current value ie.

  The second time tb is a delay time shorter than the time required for the current supplied from the booster power supply device 6 to rise sufficiently and sufficiently. Since the booster power supply device 6 is turned on while a current lower than the maximum current value imax is supplied from the main power supply device 5, the current supplied from the booster power supply device 6 exceeds the unit current value ia. When the current rises, the discharge current that actually flows through the machining gap becomes larger than the maximum current value imax, and the rising waveform of the desired discharge current pulse is lost. Therefore, the second time tb is precisely the time when the discharge current actually flowing in the machining gap reaches the maximum current value imax.

  In the embodiment, the error current value ie immediately after the current supplied from the booster power supply 6 starts flowing is equivalent to the parameter value IP24, and the first current reduction value ib is set to the parameter value IP8. Further, the second time tb is set to 1 μs from the observed rising waveform of the current supplied from the booster power supply device 6. Therefore, in the profile electric discharge machining apparatus of the embodiment, the current supplied from the main power supply 5 after a delay time of 1 μs after the booster power supply 6 is turned on is the parameter value IP24 obtained by subtracting IP8 from the parameter value IP32. The main power supply 5 is operated so that an electric current is supplied to the machining gap.

  The pulse generator 50 outputs a command signal after a third time tc after reducing the current supplied from the main power supply 5 so as to supply the current corresponding to the error current value ie from the main power supply 5. Then, the switching elements TR1-TR16 of the main power supply device 5 are selectively turned on / off in synchronism so as to reduce the current supplied from the main power supply device 5 by a preset second current reduction value ic.

  Thereafter, until the rise time td of the current supplied from the booster power supply 6 elapses, the current supplied from the main power supply 5 is decreased stepwise by the second current reduction value ic every third time tc. Thus, the error current is supplemented with the current supplied from the main power supply device 5 and at the same time, the discharge current that actually flows through the machining gap is increased by the unit current value ia every first time ta.

  When a desired discharge current pulse waveform having a smooth rise is obtained by increasing the unit current value ia every predetermined first time ta, during the rise time td of the current supplied from the booster power supply device 6 At any point in time, only the current supplied from the booster power supply device 6 increases the error current value ie and the unit current value ia for each first time ta with respect to the current in the waveform of the desired discharge current pulse. It can be seen that only the increment current value is insufficient.

  Therefore, the third time tc and the second current reduction value ib are determined by the slope of the current change in which the error current value ie and the incremental current value are superimposed during the rise time td. However, the second current reduction value ic is basically a parameter value IP1 that is the minimum current value that can be supplied by the main power supply device 5 unless there is a special reason for obtaining an arbitrary waveform more freely. Set to current. Therefore, the third time tc substantially determines the rising waveform of the discharge current pulse.

  When the above is seen from another viewpoint, as can be seen in FIG. 2A, the machining control device 2 starts the main power supply device every first time ta from when the current of the maximum current value imax is supplied from the booster power supply device 6. When the current supplied from 5 is increased by unit current value ia, the switching elements TR1-TR16 of the main power supply 5 are controlled to be turned on and off so as to coincide with the incremental current value io reached after the rising time td. In other words, it can be said that the current supplied from the main power supply device 5 is decreased stepwise by the second current reduction value ic every third time tc.

  Therefore, at the third time tc, the first current reduction value ib is subtracted from the maximum current value imax with the second current reduction value ic as the unit current value ia that is the minimum current value that can be supplied by the main power supply device 5. The difference between the error current value ie immediately after the booster power supply 6 is turned on and the incremental current value io after the rise time td of the current supplied from the booster power supply 6 is divided by the unit current value ia to obtain the step number n. Thus, the rise time td can be obtained by dividing by the number of steps n. In the embodiment shown in FIG. 2, since the number of steps n is 16 and the rise time td is 16 μs, the third time tc is set to 1 μs.

  At this time, since the third time tc and the second current reduction value ic are constant, the change in the current supplementing the error current value ie supplied from the main power supply device 5 and the booster power supply device 6 are supplied. It is conceivable that the actual change in the error current value ie depending on the rising waveform of the current does not exactly match. However, the rising waveform of the discharge current pulse that is actually supplied to the machining gap does not become inappropriate to the extent that it has a significant effect on the machining result, and is within the error range, so there is no practical problem.

  As shown in FIG. 3D, the error current value ie gradually decreases during the rising time td, and the incremental current value increases by the unit current value ia every first time ta. When the current supplied from the main power supply device 5 is reduced stepwise by the second current reduction value ic every time tc, as a result, the error current is supplemented with the current supplied from the main power supply device 5. At the same time, the current is increased by the unit current value ia every first time ta. As a result, a desired discharge current pulse waveform having a smooth rise is obtained.

  After the rise time td when the current supplied from the booster power supply device 6 rises to the maximum current value imax, the pulse generator 50 outputs a command signal, and the plurality of switching elements TR1 to TR16 of the main power supply device 5 are binary counted. The switching circuits SC1 to SC16 are selectively turned on or off by shifting them in time, thereby matching the slope of the desired rising waveform of the discharge current until the discharge current reaches the peak current value according to the machining conditions. The current is increased stepwise by the parameter value IP1 corresponding to the unit current value ia.

  After the discharge current reaches the peak current value ipeak according to the machining conditions, the discharge current is supplied while maintaining the peak current value ipeak. Then, after the discharge occurs and the discharge current begins to flow in the machining gap, after reaching the on time ton according to the machining conditions, all the switching elements TR1-TR32 are turned off to make the switching circuits SC1-SC32 non-conductive. As a result, the supply of the discharge current from the main power supply device 5 and the booster power supply device 6 is stopped, and the discharge current is extinguished after the fall time.

  As described above, by repeatedly supplying a discharge current pulse with a smooth rise, machining with reduced consumption of the tool electrode is performed. At this time, the current suddenly drops drastically during the supply of the discharge current, and the waveform of the discharge current pulse does not become incorrect. Absent. In addition, since it is possible to simultaneously turn on the booster power supply 6 without shutting off the main power supply 5, there is no instantaneous drop in the voltage between the electrodes due to the generation of the back electromotive force, and the detection device can accurately Accurate adaptive control can be performed by detecting the voltage.

  The electric discharge machining apparatus of the present invention is not required to have the same configuration as the specific electric discharge machining apparatus shown in the embodiment, and can be applied without departing from the technical idea of the present invention. Is possible. Moreover, it can implement in combination with the other sculpture electric discharge machining apparatus and processing method which are not disclosed by detailed description of the invention suitably. The present invention includes a sculpted electric discharge machining apparatus that can be achieved by substantially the same means or technique without being restricted by the names or expression methods described in the detailed description of the invention.

  The present invention is applied to a die-sinking electric discharge machining apparatus. In particular, it is useful for a sculpting electric discharge machining apparatus having a machining power supply device having a booster power supply device. The present invention suppresses and drastically reduces a discharge current generated when a booster power supply is turned on, and suppresses and improves a sudden drop in a voltage waveform due to a counter electromotive voltage. The present invention achieves a desired machining result, enables adaptive control of machining accurately, and contributes to the advancement of the technology of electric discharge machining.

DESCRIPTION OF SYMBOLS 1 Processing power supply device 2 Processing control device 3 Tool electrode 4 Workpiece 5 Main power supply device 6 Booster power supply device 7 Relay switch 8 Detection device 10 First power supply unit 20 Second power supply unit 30 Third power supply unit 40 Setting device 50 Pulse Generator 51 Polarity Switching Device 52 Interpolar Line 53 Output Cable 54 Protection Circuit 60 Gate Circuit 61 Polarity Switching Device 62 Interpolar Line 63 Output Cable 64 Protection Circuit PS DC Power Supply SC Switching Circuit TR Switching Element DR Reverse Current Blocking Diode RS Current Limiting resistor

Claims (4)

In a die-sinking electric discharge machining apparatus having a machining power supply device having a main power supply device and a booster power supply device, a plurality of switching elements of the main power supply device are selectively turned on / off to supply a discharge current to a machining gap and when the power supply to supply a maximum current value or a current that can be supplied, a plurality of the booster power supply device to supply a current of the maximum current value in a state that from the main power supply supplies the discharge current the switching element from oN selectively in fact with the maximum current value due to a reduction in the current immediately after the booster power supply is turned generated depending on the rising characteristics of the current supplied from the booster power supply device the machining gap flows the discharge current error current the main power supply so as to supplement a current supplied from the main power unit which is the difference between the current value of the Die sinking electric discharge machining apparatus having a machining control apparatus for selectively turning on and off the said switching element of said main power supply so as to reduce the current being et supplied.   The processing control device has a required peak current value in which a sum of current values when a current supplied from the booster power supply device is superimposed on a current supplied from the main power supply device matches a desired discharge current pulse waveform 2. The profile according to claim 1, wherein the switching element of the main power supply device is selectively turned on / off so as to reduce the current supplied from the main power supply device in a stepwise manner. Electric discharge machine. In a sculpting electric discharge machining apparatus having a machining power supply device having a main power supply device and a booster power supply device, a plurality of switching elements of the main power supply device are selectively turned on and off based on machining conditions, for a predetermined first time. when the main power supply with rising raises the current one by unit current value to supply a smooth discharge current pulses to the machining gap to supply a maximum current value or a current that can be supplied to each from the main power unit The current of the maximum current value is supplied in a state where a discharge current is supplied from the main power supply device after the first time from when the current having a unit current value lower than the maximum current value is supplied. said booster power selectively on a plurality of switching elements of the booster power supply, generated depending on the rising characteristics of the current supplied from the booster power supply device The first predetermined relative to the maximum current value location corresponds to the error current which is the difference between the current value of the discharge current flowing to the maximum current value actually the machining gap due to a reduction in the current just after being introduced The current supplied from the main power supply is reduced after a predetermined second time so that a current lower by the current reduction value is supplied from the main power supply , and then the rise of the current supplied from the booster power supply Depending on the rising waveform of the current supplied from the booster power supply, the current supplied from the main power supply is reduced stepwise by a predetermined second current reduction value every third time until the time elapses. gradually changing the switching element of the main power supply to raise the current one by the unit current value at the same time the error current is supplemented with current supplied from the main power supply Te Die sinking electric discharge machining apparatus having a machining control device for selectively off control.   The machining control device increases the current by the unit current value every first time until the discharge current reaches the peak current value according to the machining conditions after the rising time of the current supplied from the booster power supply device. 4. The electric discharge machining apparatus according to claim 3, wherein the switching element of the main power supply device is selectively turned on / off.

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