TWI540010B - Discharge processing device - Google Patents

Description

Electric discharge machining device

The present invention relates to an electric discharge machining apparatus for performing electric discharge machining on a machined surface of a workpiece facing the front end surface of the electrode by discharging between the electrode and the workpiece, and in the electric discharge machining, An electric discharge machining apparatus capable of accurately calculating the machining area of the machined surface or the electrostatic capacitance between the electrodes and the machined surface to set appropriate machining conditions.

Conventionally, the electrode is processed to form an electrode with the workpiece by causing the electrode to face the workpiece and discharge it at a gap between the advancing end face of the electrode in the traveling direction of the electrode and the machined surface of the workpiece. The same shape. In this electric discharge machining process, it is often caused by electrical processing conditions such as a peak current value of a discharge current, a pulse width (a pulse turn-on time, and an OFF time). Processing characteristics related to speed, machined surface roughness, machining shape accuracy, and electrode consumption are greatly affected. That is, in the case where a large machining current flows to a small processing area, damage or abnormal consumption of the electrode occurs, and in the case where a small machining current flows to a large processing area, the machining speed is high. Extremely slow, so the processing conditions are set based on the processing area.

In the electric discharge machining apparatus described in Patent Document 1, data (data) of the machining depth and the machining width of the workpiece is prepared in advance, and the width and the Y in the X-axis direction of the machining portion are respectively detected by moving the electrode during the machining. The processing area is calculated by the width in the axial direction, and a discharge gap (two-pole pitch) is set by the processing area.

In the electric discharge machining apparatus described in Patent Document 2, an electrostatic capacitance detecting device capable of detecting a total electrostatic capacitance between an electrode and a processed portion of the workpiece (a portion facing the electrode side surface and the electrode lower surface) is provided. When the electrostatic capacity increases, the polarity of the voltage is switched. By reducing the voltage applied between the two poles, reducing the distance between the two poles, and increasing the electrostatic capacitance between the two poles, the electrode consumption can be suppressed while preventing the processing speed from decreasing.

In the electric discharge machining apparatus described in Patent Document 3, a pulse discriminating unit that discriminates an effective discharge pulse and an ineffective discharge pulse, and a forward amount measuring device that measures an advance amount L of the machining process in the axial direction are provided; and the dividing unit discharges The pulse number n is divided by the unit time advancement amount L; and the machining area calculation unit calculates the machining based on the removal volume v and the division data n/L generated by the single pulse discharge. Area S. The machining area calculation unit calculates the machining area by the removal volume v generated by the single pulse discharge, the division data n/L, and the following equation to calculate the machining area, and approximates the machining current value and the machining area. Proportional to change processing conditions. If the processing amount is V, it can be expressed as V=S‧L=v‧n, that is, S=v‧n/L.

[Previous Technical Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-172526

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2000-84737

[Patent Document 3] Japanese Patent Laid-Open No. Hei 9-38829

In the electric discharge machining apparatus of Patent Document 1, since the electrode is moved in the X-axis direction and the Y-axis direction during processing, it is necessary to additionally perform processing for detecting the processing area in addition to the machining operation required for the electric discharge machining process. Detection action. Further, when the electrode has a simple shape of the advancing end face in the processing advancing direction, the error of the machining area can be slightly reduced. However, when the advancing end face has a complicated shape, that is, complicated processing in which irregularities are formed on the advancing end face, it is difficult to calculate High precision processing area.

In the electric discharge machining apparatus of Patent Document 2, since the electrostatic capacitance of the processing electrode and the processed portion of the workpiece is detected, the electrostatic capacitance between the electrode side surface and the workpiece that does not contribute to the processing actually is included in In the electrostatic capacitance detection value. That is, in order to set high-precision processing conditions, in addition to the electrostatic capacitance between the electrode side surface corresponding to the error and the workpiece, the electrostatic capacitance between the front end surface and the processed surface of the workpiece before the processing traveling direction (Electrostatic capacity between the two poles) needs to be detected.

In the electric discharge machining apparatus, the machining fluid flows through the gap between the electrode and the workpiece to discharge the machining debris, but the deeper the machining depth, the more difficult it is to process the debris from the gap.

In the electric discharge machining apparatus of Patent Document 3, when the machining debris is deposited on the processing surface, the error of the removal volume v and the effective discharge pulse number n becomes large due to the effective discharge between the machining debris and the electrode. Therefore, the deeper the processing depth, the larger the error in the processing area, so that the deviation from the appropriate value of the processing conditions set based on the processing area becomes large.

In order to perform electric discharge machining with high machining accuracy, it is necessary to set processing by considering error factors such as machining chips deposited on the machined surface of the workpiece or backlash of the gear moving mechanism of the electrode moving device. condition. However, there is no technique for setting the processing conditions by re-evaluating the error factors to determine the distance between the electrodes and the machined surface.

On the other hand, when the front end surface of the electrode has a complicated shape of irregularities, it is not easy to change the processing condition (discharge current or discharge pulse) by reliably detecting the processing area at a portion where the processing area is rapidly changed in the electric discharge machining. Therefore, in the past, a method of dividing an electrode into a plurality of pieces and performing processing by multiple discharge machining has been frequently used. However, at this time, since it is necessary to perform the electric discharge machining only for the same number of times as the number of electrodes after the division, there is a problem that the electric discharge machining time for a single workpiece increases and the electrode cost increases.

An object of the present invention is to provide an electric discharge machining apparatus capable of accurately calculating a machining area of a machined surface or a capacitance between two poles between an electrode advancing end surface and a machined surface during electric discharge machining, and can increase setting machining debris or An electric discharge machining apparatus that processes conditions such as a backlash in a moving drive mechanism that moves an electrode, or an electric discharge machining apparatus that can reduce the number of electric discharge machining operations without causing a machining failure.

(1) The electric discharge machining apparatus according to the present invention is an electric discharge machining apparatus that supplies a machining liquid at a gap between an electrode and a workpiece, and applies a discharge pulse from the electrode to the workpiece to electrically discharge the workpiece. The utility model is characterized in that: the mobile device is configured to move the electrode, and can change the distance between the advancing end surface of the processing direction of the electrode and the processing pole of the workpiece; the moving distance detecting device detects the moving distance of the electrode The capacitance measuring device is capable of measuring a total electrostatic capacitance between a processed portion of the workpiece facing the electrode and the electrode via the gap; and the calculation device is configured for each measurement cycle after the start of the electrical discharge machining Timing, moving the electrode to a plurality of positions through the mobile device in a state in which the electrical discharge machining is interrupted, and using a plurality of pole spacings detected by the moving distance detecting device, and borrowing Calculating a processing area of the processing surface or a pole that is proportional to the processing area by a plurality of total electrostatic capacitances measured by the capacitance measuring device Capacitance; and a machining condition setting means, based on the calculation between the processing area of the apparatus or the poles of the electrostatic capacity by calculation, to set the associated discharge machining pulses machining conditions.

A part of the structural elements of the present invention may also be constructed as follows.

(2) The processing condition setting device includes: a first processing condition table in which a peak current, a pulse ON time, and a pulse OFF time associated with an electric discharge machining pulse are set in advance with the processing area as a parameter, and The second processing condition table of the peak current, the pulse ON time, and the pulse OFF time associated with the electric discharge machining pulse is set in advance as the parameter.

(3) In the above (1) or (2), the calculation device is configured to: the first two-pole pitch h1 and the first total electrostatic capacitance C1 measured in a state where the electrode is moved to the first movement position a second two-pole pitch h2 and a second total electrostatic capacitance C2 measured in a state where the electrode is moved to the second moving position, and a third two-pole pitch measured in a state where the electrode is moved to the third moving position When h3 and the third total electrostatic capacitance C3, the permittivity ε of the working fluid and the processing area S, use

S=h1‧h2‧h3(h1(C2-C3)+h2(C3-C1)+h3(C1-C2))/(ε(h1-h2)(h2-h3)(h3-h1))

The expressed equation is used to calculate the processing area.

(4) In the above (1) or (2), the calculation device is configured to: the first two-pole pitch h1 and the first total electrostatic capacitance C1 measured in a state where the electrode is moved to the first movement position a second two-pole pitch h2 and a second total electrostatic capacitance C2 measured in a state where the electrode is moved to the second moving position, and a third two-pole pitch measured in a state where the electrode is moved to the third moving position H3 and the third total electrostatic capacitance C3, the fourth two-pole pitch h4 and the fourth total electrostatic capacitance C4 measured in a state where the electrode is moved to the fourth moving position, the error distance α of the two-pole pitch, and the permittivity of the working fluid ε and the processing area S, used

S=((h1+α)×(h2+α)×(h3+α)×(h1(C2-C3)+h2(C3-C1)+h3(C1-C2)))/(ε(h1- H2)×(h1-h3)×(h3-h2))

α=A/B

but,

A=h1 ² (h2(h3(C2-C3)+h4(C4-C2))+h3h4(C3-C4))-h1(h2 ² (h3(C1-C3)+h4(C4-C1))+ H2(h3+h4)(h3-h4)(C2-C1)+h3h4(h3(C1-C4)+h4(C3-C1)))-h2h3h4(h2(C3-C4)+h3(C4-C2) +h4(C2-C3))

B=h1 ² (h2(C3-C4)+h3(C4-C2)+h4(C2-C3))-h1(h2 ² (C3-C4)+h3 ² (C4-C2)+h4 ² (C2- C3))+h2 ² (h3(C1-C4)+h4(C3-C1))-h2(h3 ² (C1-C4)+h4 ² (C3-C1))+h3h4(h3-h4)(C1- C2)

The expressed equation is used to calculate the processing area.

(5) In the above (1) or (2), the calculation device is configured to: the first two-pole pitch h1 and the first total electrostatic capacitance C1 measured in a state where the electrode is moved to the first movement position a second two-pole pitch h2 and a second total electrostatic capacitance C2 measured in a state where the electrode is moved to the second moving position, and a third two-pole pitch measured in a state where the electrode is moved to the third moving position H3 and the third total electrostatic capacitance C3, the fourth two-pole pitch h4 and the fourth total electrostatic capacitance C4 measured in a state where the electrode is moved to the fourth moving position, and an angle between the electrode advancing end surface and the axis of the electrode θ, the error distance α of the two-pole pitch, the permittivity ε of the machining fluid, the processing area S, and the electrostatic capacitance C between the two poles are used.

S=((h1+α)×(h2+α)×(h3+α)×(h1(C2-C3)+h2(C3-C1)+h3(C1-C2))×sinθ)/(ε( H1-h2)×(h2-h3)×(h3-h1))

α=A/B

but,

A=h1 ² (h2(h3(C2-C3)+h4(C4-C2))+h3h4(C3-C4))-h1(h2 ² (h3(C1-C3)+h4(C4-C1))+ H2(h3+h4)(h3-h4)(C2-C1)+h3h4(h3(C1-C4)+h4(C3-C1)))-h2h3h4(h2(C3-C4)+h3(C4-C2) +h4(C2-C3))

B=h1 ² (h2(C3-C4)+h3(C4-C2)+h4(C2-C3))-h1(h2 ² (C3-C4)+h3 ² (C4-C2)+h4 ² (C2- C3))+h2 ² (h3(C1-C4)+h4(C3-C1))-h2(h3 ² (C1-C4)+h4 ² (C3-C1))+h3h4(h3-h4)(C1- C2)

C=εS/((h1+α)sinθ) or

C=εS/((h2+α)sinθ) or

C=εS/((h3+α)sinθ) or

C=εS/((h4+α)sinθ)

The calculated equation is used to calculate the processing area and the electrostatic capacitance between the two electrodes.

(6) The processing condition setting device according to any one of (2) to (5), wherein the measurement period is changed based on the calculated processing area or the capacitance between the two electrodes, the measurement period is by the static electricity The capacity measuring device measures the total electrostatic capacitance between the electrode and the processed portion of the workpiece to change the electrical discharge machining conditions.

(7) In any one of (2) to (5), the processing condition setting device sets a machining current to be supplied to the electrode to be substantially equal to the calculated machining area or the capacitance between the two poles. proportion.

(8) In the above (7), the processing condition setting device sets the current density of the machining current to be equal to or lower than a predetermined current density.

(9) In the above (8), the processing condition setting device is provided with a discharge pulse setting device that sets a discharge pulse corresponding to a machining current supplied to the electrode, the machining area, or an electrostatic capacitance between the two electrodes.

(10) In the above (4), the processing condition setting device includes a jump operation calculation device that sets at least one of a skip period and a jump amount of a jump operation based on the error distance α of the two-pole pitch.

According to the present invention, there is provided a moving device for moving a electrode, a moving distance detecting device for detecting a moving distance of the electrode, and a capacitance measuring device for measuring a total electrostatic capacitance between the electrode and a processed portion of the workpiece; The apparatus performs processing by using a plurality of pole pitches detected after moving the electrodes to a plurality of positions and a plurality of measured total electrostatic capacitances in a state in which the discharge machining is interrupted in the state of the measurement cycle after the start of each electrical discharge machining. a processing area of the surface or an electrostatic capacitance between the two electrodes proportional to the processing area; and a processing condition setting device that sets the correlation with the electric discharge machining pulse based on the processing area calculated by the calculation device or the electrostatic capacitance between the two electrodes The processing conditions are as follows, so that the following effects can be obtained.

The processing area of the processed surface of the workpiece facing the front end surface of the electrode or the electrostatic capacitance between the two poles proportional to the processing area can be calculated with high precision. In other words, since the processing area or the capacitance between the two electrodes is calculated by using the two-pole pitch at a plurality of positions where the electrodes are moved and the total electrostatic capacitance between the electrode and the processed portion of the workpiece, the processing area can be calculated with high precision or The electrostatic capacitance between the two electrodes proportional to the processing area, and based on the processing area obtained in the state of the electric discharge machining after the start of the interrupt discharge machining or the high-precision calculation value of the electrostatic capacitance between the two electrodes, the change in the processing area can be performed. Or the state between the two poles such as the occurrence of processing debris to appropriately set the processing conditions related to the electric discharge machining pulse.

Moreover, since the total electrostatic capacitance and the two-pole pitch actually measured are used, even in the case where the processing area is rapidly increased, the high-precision processing area or the electrostatic capacitance between the two electrodes can be calculated, and the electrode can be separated without The machining can be performed with high precision without causing machining failure, and the number of electric discharge machining can be reduced.

According to the configuration of the above (2), the peak current, the pulse ON time, and the pulse OFF time of the electric discharge machining pulse can be set by the electric discharge machining condition setting means based on the first and second machining condition tables.

According to the configuration of the above (3), even when the distance from the surface of the workpiece to the processing surface is unknown, the load of the calculation processing of the processing area can be reduced, so that the calculation processing speed can be accelerated and implemented correctly. The calculation of the processing area.

According to the configuration of the above (4), even when the distance from the surface of the workpiece to the processing surface is unknown, the calculation of the machining area and the calculation of the error distance can be performed. Moreover, by calculating the error distance, it is possible to set processing conditions in which processing debris or backlash are taken into consideration.

According to the configuration of the above (5), even when the distance from the surface of the workpiece to the processing surface is unknown, the capacitance between the electrodes between the forward end and the processing surface of the electrode formed into a complicated shape can be performed. That is, the calculation of the electrostatic capacitance and the error distance between the two poles which are correctly proportional to the processing area. Moreover, by calculating the error distance, it is possible to set processing conditions in which processing debris or backlash are taken into consideration.

According to the configuration of (6), since the measurement period is changed based on the processing area or the electrostatic capacitance between the electrodes, the measurement period is performed by the electrostatic capacitance calculation device to measure the total static electricity between the electrode and the processed portion of the workpiece. Since the electric discharge machining conditions are changed in capacity, the measurement cycle can be set so that appropriate electric discharge machining conditions can be set in accordance with the shape change of the electrode advancing end surface.

According to the configuration of the above (7), since the processing current value supplied to the electrode is controlled to be substantially proportional to the processing area calculated by the processing condition setting means or the electrostatic capacitance between the two electrodes, it is possible to prevent the current supply from being excessive. The electrode is abnormally consumed.

According to the configuration of the above (8), since the processing condition setting means controls the current density to be equal to or lower than a predetermined current density, it is possible to prevent an abnormal situation such as a decrease in the processing speed.

According to the configuration of the above (9), the discharge pulse setting means can set the discharge pulse corresponding to the machining current value supplied to the electrode and the machining area or the electrostatic capacitance between the two electrodes.

According to the configuration of the above (10), since the jump operation calculation device for setting at least one of the skip period and the jump amount of the jump operation based on the error distance of the two-pole pitch is provided, the cause can be surely cleared from the processed surface. Processing the generated machining debris can prevent the processing speed from decreasing.

Hereinafter, embodiments for carrying out the invention will be described based on the embodiments.

[Example 1]

Hereinafter, an embodiment of the present invention will be described based on Figs. 1 to 10 .

As shown in FIG. 1, the electric discharge machining apparatus M supplies a machining liquid at a gap between the electrode E and the workpiece W, and applies a discharge pulse from the electrode E to the workpiece W to perform a workpiece W. Electrical discharge machining device. This electric discharge machining apparatus M has a peripheral machine such as a processing machine main body 1, a control device 2, and a machining liquid tank 7. The processing machine body 1 is composed of a head 3 having an electrode E and a Z-axis moving mechanism 4 (moving device) as a feeding device capable of reciprocating the head 3 in the up and down direction (Z axis); The shaft moving mechanism 5 can reciprocate the machining liquid tank 7 containing the workpiece W horizontally in the horizontal direction (X-axis) of FIG. 1; the Y-axis moving mechanism 6 can move the machining liquid tank 7 along the right and left direction The front and rear directions (Y axis) are horizontally reciprocated; the machining liquid tank 7 can accommodate the workpiece W and store the machining fluid; the base 8; and the cable 26 and the like. The electrode E is fitted with a mounting plate that is detachably disposed at the lower end portion of the head 3.

The Z-axis moving mechanism 4 is constituted by a pair of Z-axis feed guides, a ball screw mechanism, a Z-axis motor, and the like which are disposed on the base 8 and extend in the Z-axis direction, and is numerically controlled by the control device 2. The Z-axis motor is driven to move the head 3 in the Z-axis direction.

The X-axis moving mechanism 5 is composed of an X-axis movable table, a pair of X-axis feed guides disposed on the base 8 and extending in the X-axis direction, a ball screw mechanism, an X-axis motor, and the like, and is transmitted through the control device 2 for numerical values. The control of the X-axis motor is driven to move the X-axis movable table in the X-axis direction. The Y-axis moving mechanism 6 is composed of a Y-axis movable table, a pair of Y-axis feed guides disposed in the Y-axis movable table and extending in the Y-axis direction, a ball screw mechanism, a Y-axis motor, and the like. The Y-axis movable table and the machining liquid tank 7 are moved and driven in the Y-axis direction by driving the Y-axis motor whose numerical control is performed by the control device 2.

The machining liquid tank 7 is fixed to the upper end of the Y-axis movable table of the Y-axis moving mechanism 6. The control device 2 is disposed adjacent to the processing machine body 1 and supplies power and control signals to the processing machine body 1 via the cable 26. As described above, the electrode E and the workpiece W are configured to be relatively movable in the X-axis direction and the horizontal X and Y-axis directions in the Z-axis direction.

The Z-axis moving mechanism 4 can change the position of the electrode E in the Z-axis direction by moving the head 3 in the Z-axis direction, and can change the advance end surface of the processing direction of the electrode E to the processing surface of the workpiece W. Two pole spacing. In the following, the surface portion of the workpiece W that faces the advancing end surface of the electrode E in the processing advancing direction is defined as "the processed surface of the workpiece W", and the area of the processed surface is defined as the "machined area". Further, the electrode E is made of copper or graphite, but when the workpiece W is a cemented carbide (superhard alloy), it may be made of copper or tungsten.

As shown in FIG. 2, the control device 2 includes an arithmetic processing unit 9 including a computer including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an interface, and the like. The processing power supply circuit 10 supplies DC power for electric discharge machining, the discharge detecting unit 11 detects a discharge state between the electrode E and the workpiece W, and the capacitance measuring unit 12 measures the gap. The electrostatic capacitance between the processed portion of the workpiece W and the electrode E in the gap and the side surface and the lower surface of the electrode E (hereinafter referred to as "total electrostatic capacitance"); the discharge control unit 13 supplies the discharge pulse for the electric discharge machining The electrode E and the workpiece W; the machining current measuring unit 14; and the calculation mode switching switch 15 and the like. In the following description, the electrostatic capacitance between the front end surface of the electrode E and the processed surface of the workpiece W facing the advancing end surface is taken as the electrostatic capacitance between the two electrodes.

As shown in FIG. 3, the capacitance measuring unit 12 includes a switching transistor 12s provided in a feed line derived from a power source Vc, a constant current circuit 12a connected to a transmission line, and the above-described transportation. The line is connected and can output a pulse output circuit 12b of a pulse of a certain period (the pulse ON time is equal to the OFF time), the transistor 12c, the resistor 12d, the voltage detecting circuit 12e, and the like.

The base side terminal 12x of the transistor 12s and the output terminal 12v of the voltage detecting circuit 12e are connected to the capacitance measuring control unit 17. The transistor 12s is turned on by the driving signal from the capacitance measuring control unit 17, and the capacitance measuring unit 12 is activated. Thereafter, the electrostatic capacitance measurement control unit 17 processes the output signal from the output terminal 12v of the voltage detecting circuit 12e to measure the total electrostatic capacitance. In other words, the capacitance measuring unit 12 and the capacitance measuring control unit 17 correspond to the "capacitance measuring device".

Since the electrode E and the processed portion of the workpiece W face each other with a gap therebetween, the gap between the two and the machining liquid in the gap constitute the capacitor 12f. In the electrostatic capacitance measuring unit 12, the processing portion (the portion facing the electrode side surface and the electrode advancing end surface) of the electrode E and the workpiece W is periodically supplied with the direct current i from the pulse output circuit 12b, and is transmitted through the voltage detecting circuit 12e. The voltage V of the detection electrode E is calculated by the capacitance measurement control unit 17 based on the average voltage Vm calculated by the voltage V, the direct current i, and the time to which the direct current i is supplied to the capacitor 12f. Total electrostatic capacity.

As shown in Fig. 4, when a pulse is output from the pulse output circuit 12b, the transistor 12c is turned on and the point P is grounded, and the voltage detected by the voltage detecting circuit 12e is zero and discharged from the capacitor 12f. When the transistor 12c is closed (OFF), the capacitor 12f continues to be charged during its closed period (time to), and the voltage V detected by the transmission voltage detecting circuit 12e linearly increases. The capacitance measuring control unit 17 receives the analog/digital (A/D) conversion from the voltage signal of the detection voltage V supplied from the output terminal 12v, and calculates the average voltage Vm. Then, when the total capacitance C and the amount Q of the capacitor 12f are set, since Q=i×2to, the total capacitance C can be obtained by the equation C=Q/Vm=i×2to/Vm.

Further, the capacitance measuring unit 12 is not limited to the above configuration, and various configurations can be employed as long as at least the total electrostatic capacitance C between the electrode E and the processed portion of the workpiece W can be measured.

The discharge control unit 13 supplies power from the power supply circuit 10, and applies a discharge pulse set in the processing condition setting unit 19 to be described later to the counter electrode E and the workpiece W. The machining current measuring unit 14 measures the current supplied by the discharge pulse via the ammeter 14a, and supplies the detected current to the arithmetic processing unit 9. In this manner, when a discharge pulse is applied, if the gap between the electrode advancing end faces and the machined surface of the workpiece W is formed to be a predetermined distance that can be discharged, the discharge is started and processing is started.

The calculation mode changeover switch 15 is configured to selectively select and set the machining area calculation mode and the capacitance calculation mode. The former is based on the calculation processing unit 9, and sets the machining conditions based on the machining area of the machining surface before the start of the electric discharge machining process. The latter sets the processing conditions based on the electrostatic capacity between the two poles. Further, the arithmetic mode switching switch 15 may be omitted, and the processing area of the processing surface may be calculated first, and when it is difficult to calculate the processing area, the electrostatic capacitance between the two electrodes is automatically calculated.

The calculation processing unit 9 is a position control unit 16 (moving distance detecting device) that controls the Z-axis moving mechanism 4, a capacitance measuring control unit 17, an arithmetic device 18, a machining condition setting unit 19 (processing condition setting device), and X, Y. The control unit 20 or the like is formed.

The position control unit 16 is formed such that the head 3 can be moved in the vertical direction by the Z-axis moving mechanism 4, thereby changing the pitch of the two poles from the front end surface of the electrode E to the processing surface. The position control unit 16 is formed to detect the two-pole pitch of the front end surface of the electrode E to the processing surface.

In addition to the above-described processing, the capacitance measurement control unit 17 receives a signal from the measurement period calculation unit 24 described later and measures the measurement period of the total capacitance by the capacitance measuring unit 12, and turns on the transistor 12s for each measurement period. The operation timing of the electrostatic capacitance measuring unit 12 is controlled. In the same manner as the general electrical discharge machining apparatus, the electric discharge machining apparatus M is configured to analyze the machining program by a numerical control program using a machining program for each workpiece, and to move the Z-axis by the position control unit 16. (4) Numerical control is performed, and the X and Y control units 20 numerically control the X-axis and Y-axis moving mechanisms 5 and 6, thereby controlling the position of the electrode E in the X, Y, and Z-axis directions. At the same time, electrical discharge machining. These structures are not directly related to the present invention, and detailed description thereof will be omitted. The X and Y control units 20 drive and control the X-axis moving mechanism 5 and the Y-axis moving mechanism 6 as described above.

The calculation device 18 is provided with a machining area calculation unit 21 that calculates the machining area when the machining area calculation mode is used, and a capacitance calculation unit 22 that calculates the electrostatic capacitance between the two electrodes in the capacitance calculation mode. As shown in FIG. 5, the machining area calculation unit 21 is configured to move the electrode E to a plurality of positions different in the vertical direction by the Z-axis moving mechanism 4 during the electric discharge machining (the time point during the electric discharge machining). The first and second movement positions d1 and d2 (the distance from the surface of the workpiece W to the electrode advancing end surface) of the plurality of positions which are different in the vertical direction detected by the position control unit 16 The second and second pole pitches h1, h2, and the first and second totals corresponding to the first and second pole pitches h1, h2 measured by the electrostatic capacitance measuring unit 12 and the capacitance measuring control unit 17 The processing area S of the processed surface Wf of the workpiece W is calculated by the electrostatic capacitances C1 and C2. Further, as the electrode E, for example, a columnar electrode having a substantially horizontal forward end surface Ef is described as an example, but the electrode E does not have to be columnar, and the processing area may be continuous or not in accordance with the progress of the electric discharge machining. An electrode that changes continuously.

Specifically, when the above description is made, the electrode E is brought into contact with the processed surface Wf of the workpiece W to initialize the pitch of the two poles to zero. Next, as shown in FIG. 5(a), the Z-axis moving mechanism 4 is driven and controlled to move the electrode E to the first moving position d1. In this case, the first total electrostatic capacitance C1, the interelectrode electrostatic capacitance Cp between the electrode advancing end surface Ef and the processed surface Wf, the processing area S of the processed surface Wf, the first two-pole pitch h1, and the side surface Es of the electrode E are The first total electrostatic capacitance C1 of the electrostatic capacitance Ca between the workpiece W and the capacitance ε of the machining liquid can be expressed by the following formula (1) and detected by measurement.

C1=Cp1+Ca ...(1)

However, Cp1 = εS/h1.

Next, as shown in FIG. 5(b), the Z-axis moving mechanism 4 is driven and controlled to move the electrode E to the second moving position d2. At this time, if the second total electrostatic capacitance C2, the interelectrode electrostatic capacitance Cp2 between the electrode advancing end surface Ef and the processed surface Wf, and the electrode advancing end surface Ef from the second bipolar distance h2 of the processing surface Wf, the second The total electrostatic capacitance C2 can be expressed by the following formula (2) and detected by measurement.

C2=Cp2+Ca‧d2/d1 ...(2)

However, Cp2 = εS/h2.

When the equations (1) and (2) are solved for the processing area S, the processing area S can be expressed by the following equation (3):

S=(h1‧h2(C2‧d1-C1‧d2))/(ε(d1‧h1-d2‧h2)) (3)

Further, since the distance from the surface of the workpiece W to the processing surface Wf in the position control unit 16 is known, the surface of the workpiece W can be calculated from the first and second pole pitches h1, h2 and the permittivity ε. The distance d1, d2 to the advancing end face of the electrode.

An example of a technique for detecting the permittivity ε of the working fluid will be described.

The permittivity ε of the working fluid is obtained by using the known standard electrode Ea. As shown in Fig. 6(a), the standard electrode Ea is brought into contact with the surface of the workpiece W to initialize the pitch of the electrodes Ea to zero. Next, as shown in FIG. 6(b), the standard electrode Ea is moved to a position at a distance h0 from the surface of the workpiece W, and the capacitance measuring unit 12 and the capacitance measuring control unit 17 measure the total of the positions. Static capacitance C0. When the area in which the standard electrode Ea and the workpiece W face each other is S0, the permittivity ε can be expressed by the following formula (4):

ε=h0‧C0/S0 (4)

By the above, the formula (3) is substituted into the first and second total electrostatic capacitances C1, C2, the first and second two-pole pitches h1, h2, the distance from the surface of the workpiece W to the electrode advancing end face Ef. The processing area S of the processed surface Wf of the workpiece W is calculated by d1, d2 and the permittivity ε.

Further, by calculating the electrostatic capacitances Cp1 and Cp2 between the first and second electrodes by using the calculated value of the processing area S, it is possible to detect the presence or absence of machining debris and the like by the tendency of increase or decrease in electrostatic capacitance between the two electrodes. In other words, when the Z-axis moving mechanism 4 is driven by a ball screw mechanism or a linear motor that does not generate a backlash, it is assumed that C1 = 2Cp2 when h1 = h2/2. Therefore, when the electrostatic capacitance Cp2 between the second electrodes is smaller than 1/2 of the electrostatic capacitance Cp1 between the first electrodes, it is possible to detect that machining debris is deposited on the processed surface of the workpiece W, and the second can be detected. The smaller the electrostatic capacitance Cp2 between the two electrodes is less than 1/2 Cp1, the larger the deposition amount of the processed debris on the processed surface of the workpiece W.

Next, in the case where the front end face of the electrode E is inclined with respect to the horizontal plane, an example of the electrostatic capacitance between the front end surface Ef and the processed surface Wf of the calculation electrode E will be described based on FIG. 7 in the capacitance calculation mode. . The electrostatic capacitance calculation unit 22 is configured to move the electrode E to a plurality of positions different in the vertical direction by the Z-axis moving mechanism 4 during the electric discharge machining, and to use the plurality of positions detected by the position control unit 16, for example, First and second pole pitches h21 and h22 at the second movement positions d21 and d22, and the first and second pole pitches h21 measured by the corresponding electrostatic capacitance measuring unit 12 and the capacitance measuring control unit 17. The first and second total electrostatic capacitances C21 and C22 at the two positions of h22 are used to calculate the electrostatic capacitance between the electrodes between the front end surface Ef of the electrode EA and the processed surface Wf of the workpiece W.

The electrode EA is, for example, a columnar shape having an angle θ (0° < θ < 90°) between the electrode advancing end surface Ef and the electrode axis, and the distance d21, d22 from the surface of the workpiece W to the processing surface is in position control. The part 16 is known.

First, the electrode EA is brought into contact with the machined surface of the workpiece W to initialize the pitch of the two poles to zero. Next, as shown in FIG. 7(a), the Z-axis moving mechanism 4 is driven and controlled to move the electrode EA to the first moving position d21. In this case, the first total electrostatic capacitance C21, the electrostatic capacitance Cp21 between the electrode advancing end surface and the processing surface, the processing area SA, the first two-electrode pitch h21 from the front end surface of the electrode EA to the processing surface, and the electrode EA are set. The electrostatic capacitance Ca between the side surface and the workpiece W, the permittivity ε of the machining liquid, and the angle θ between the electrode advancing end surface and the vertical surface, the first total electrostatic capacitance C21 can be the same as the above formula (1). It is indicated and detected by measurement. Then, by substituting the electrostatic capacitance Cp21 between the two electrodes shown in the following formula (5) into the formula (1), the first total electrostatic capacitance C21 can be expressed by the following formula (6):

Cp21=εSA/(h21‧sinθ) (5)

C21=εSA/(h21‧sinθ)+Ca (6)

Next, as shown in FIG. 7(b), the head 3 is moved upward by the Z-axis moving mechanism 4 to move the electrode EA to the second moving position d22. At this time, if the second total electrostatic capacitance C22, the interelectrode electrostatic capacitance Cp22 between the electrode advancing end surface and the processing surface, the second two-pole pitch h22, and the first and second movement positions d21 and d22, the second total static electricity is used. The capacity C22 can be expressed in the same manner as the above formula (2). Then, by substituting the inter-electrode capacitance Cp22 represented by the following formula (7) into the formula (2), the second total electrostatic capacitance C22 can be expressed by the following formula (8) and detected by measurement.

Cp22=εSA/(h22‧sinθ) (7)

C22=εSA/(h22‧sinθ)+Ca‧d22/d21 (8)

When the equations (6) and (8) are solved for the processing area SA of the processed surface of the workpiece W, the processing area SA can be expressed by the following formula (9):

SA=(h21‧h22(C22‧d21-C21‧d22))×sinθ/(ε(d21‧h21-d22‧h22)) (9)

Here, by substituting the above formula (9) into the equation (5), the inter-electrode capacitance Cp21 at the first movement position d21 can be expressed by the following formula (10):

Cp21=h22(C22‧d21-C21‧d22)/(d21‧h21-d22‧h22) ...(10)

By substituting the above formula (9) into the equation (7), the interelectrode capacitance Cp22 at the second movement position d22 can be expressed by the following formula (11):

Cp22=h21(C22‧d21-C21‧d22)/(d21‧h21-d22‧h22) ...(11)

By referring to the above formula (10) or (11), the first and second total electrostatic capacitances C21 and C22, the first and second two-pole pitches h21 and h22, and the workpiece W are applied to the electrode. The distances d21 and d22 of the front end of the EA and the permittivity ε can be used even when the electrode EA having a complicated shape of the forward end face having an angle θ between the electrode advancing end face and the axis of the electrode EA is provided. The equation of θ is used to calculate the first and second electrostatic capacitances Cp21 and Cp22. Since the interelectrode capacitances Cp21 and Cp22 are physical quantities proportional to the processing area SA, for example, the two-pole pitch h21 is set to the target two-pole pitch in advance, and the machining condition setting unit 19 is used based on the inter-electrode electrostatic capacitance Cp22. The electric discharge machining conditions are set as described later. Further, similarly to the above, the state of the two poles such as the state of occurrence of the machining debris can be detected by the tendency of the increase or decrease of at least one of the first and second interelectrode capacitances Cp21 and Cp22. Further, the electrode EA shown in FIG. 7 is described by taking a columnar electrode as an example, and the electrode is not necessarily required to have a columnar shape, and the processing area may be continuously or discontinuously changed in accordance with the progress of the electric discharge machining. electrode. Further, it may be an electrode having a plurality of inclined faces having equal inclination angles or different inclination angles on the front end face of the electrode.

The machining condition setting unit 19 includes a discharge pulse setting unit 23, a measurement cycle calculation unit 24, and a jump operation calculation unit 25. The discharge pulse setting unit 23 is provided with a processing condition table shown in Table 1 and a processing condition table shown in Table 2. In addition, Tables 1 and 2 show the processing conditions when the copper electrode, the steel workpiece, and the working fluid have a permittivity ε=15.9372×10 ^-12 F/m, and Table 2 shows the static electricity between the two poles at a pitch of 5 μm. capacity.

When the machining area calculation mode is set, the machining condition setting unit 19 applies the machining area S obtained by the calculation as described above to the machining condition table shown in Table 1, and sets the peak current and discharge of the discharge pulse. Pulse ON time and OFF time. The peak current is set to a value approximately proportional to the processing area S, and the current density is set to a value of 5 A/cm ² or less, that is, about 5 A/cm ² . Further, the voltage of the discharge pulse can be appropriately set by the discharge control unit 13. Thereafter, the data of the electric discharge machining conditions set as described above is supplied to the discharge control unit 13, and the electric discharge machining is performed based on the discharge pulse.

When the capacitance calculation mode is set, the processing condition setting unit 19 transmits the first and second inter-electrode capacitances Cp21 and Cp22 obtained by the calculation as described above, and the preferred first inter-electrode capacitance. Cp21 is applied to the processing condition table shown in Table 2 to set the peak current of the discharge pulse, the ON time and the OFF time of the discharge pulse. The peak current is set to a value approximately proportional to the electrostatic capacitance between the two electrodes, and the current density is set to a value of 25 A/nF or less, that is, about 25 A/nF. Thereafter, the data of the electric discharge machining conditions set as described above is supplied to the discharge control unit 13, and the electric discharge machining is performed based on the discharge pulse.

Further, the processing condition tables shown in Tables 1 and 2 are merely examples, and may be appropriately changed depending on the permittivity of the working fluid, the combination of the electrode material and the material to be processed, the processing conditions, and the like.

The measurement period calculation unit 24 includes a map in which the capacitance measurement unit 12 and the capacitance measurement control unit 17 measure the total capacitance and measure the measurement cycle in which the processing conditions are changed in advance. In the drawing, the measurement period is set with the processing areas S and SA (or the electrostatic capacitance between the electrode advancing end faces and the processing surfaces) as a parameter. Since the smaller the processing areas S and SA, the higher the electrode advance speed, the larger the measurement period is, the larger the processing area S and SA (or the electrostatic capacitance between the two electrodes) is.

The jump operation calculation unit 25 is configured to set the jump period and the jump amount of the jump operation of the electrodes E and A based on the error distance α of the two-pole pitch. In addition, the "jumping operation of the electrode" means "an operation of moving the electrode up and down in order to flow the machining debris deposited on the processing surface to the outside of the gap." As shown in FIG. 8 and FIG. 9, the relationship between the error distance α of the height of the machining debris deposited on the machined surface of the workpiece W, the jump period, and the amount of jump movement is previously in the form of a map or a table. Make settings and store them in memory.

However, the calculation technique of the error distance α of the two-pole pitch is described in the third and fourth embodiments. However, when the processing area or the capacitance between the two electrodes is calculated as shown in FIG. 5 or FIG. 7, the error distance is not calculated. In the case of α, the error distance of the default value (for example, 4 μm) can also be applied.

The graph of Fig. 8 is set such that the larger the error distance α is, the smaller the jump period is. The graph of Fig. 9 is set such that the larger the error distance α is, the larger the jump movement amount is. Incidentally, the drawings shown in Figs. 8 and 9 are merely examples, and may be appropriately changed depending on the processing shape, processing conditions, and the like.

Next, the electric discharge machining condition setting process performed by the machining condition setting unit 19 will be described based on the flow chart of FIG. Further, Si (i = 1, 2, ...) indicates each step. Moreover, this electric discharge machining condition setting process is a process performed in the processing area calculation mode with respect to the example shown in FIG. First, when the electric discharge machining apparatus M is started, various signals (S1) such as the permittivity ε of the machining liquid or the type of the selected calculation mode are read. S2 determines whether or not the start switch of the electric discharge machining process is turned on. As a result of the determination in S2, if the electric discharge machining process is started, the process proceeds to S3, and it is determined whether or not the permittivity data of the machining liquid is retained. As a result of the determination in S2, if the electric discharge machining process is not started, the process returns to S1.

As a result of the determination in S3, if the permittivity data is retained, the process proceeds to S4, and the two-pole pitch and the total electrostatic capacitance are measured. As a result of the determination in S3, if the permittivity data is not retained, the process proceeds to S5, and the permittivity of the machining liquid is detected by the standard electrode as described above, and then the process proceeds to S4.

S4 is driven by the position control unit 16 and the Z-axis moving mechanism 4 to sequentially drive the electrode advancing end faces to the first and second moving positions to measure the first and second pole pitches h1, h2 and the workpiece at the respective moving positions. The distance from the surface of W to the processing surface is d1, d2. Moreover, the electrostatic capacitance measuring unit 12 and the electrostatic capacitance measuring control unit 17 measure the first and second total electrostatic capacitances C1 and C2 at the first and second moving positions.

Next, it is determined in S6 whether or not the machining area calculation mode is selected. As a result of the determination in S6, if the machining area calculation mode is selected, the machining area calculation processing is performed in S7. The processing area calculation unit 21 calculates the processing area S by substituting the equation (3) into the first, second total electrostatic capacitances C1 and C2, the first and second two-pole pitches h1 and h2, and the distances d1 and d2. After calculating the processing area, move to S9.

The S9 system sets the processing conditions using the processing condition table of Table 1 based on the calculated processing area. The processing conditions set here include an electrical condition of electrical discharge machining such as a peak current value, a jump period of the electrode E, and a jump movement amount. After the processing conditions are set, the process proceeds to S10 to start the electric discharge machining process. Further, the measurement cycle for measuring the total electrostatic capacitance is calculated by the electrostatic capacitance measurement control unit 17.

After the start of the electric discharge machining process, it is determined whether or not the measurement cycle timing is determined (S11). As a result of the determination in S11, if it is the measurement cycle timing, the process proceeds to S4, and the measurement of the two-pole pitch and the total capacitance is performed in a state where the discharge machining process is interrupted. As a result of the determination in S11, if it is not the measurement cycle timing, the process proceeds to S12, and the determination of the end of the electric discharge machining process is performed. As a result of the determination in S12, the control is ended when the electric discharge machining process is completed, and when the electric discharge machining process is not completed, the process proceeds to S10 to continue the electric discharge machining process.

Further, with respect to the example shown in FIG. 7, the electric discharge machining condition setting processing performed in the electrostatic capacitance calculation mode is also substantially the same as described above.

When the capacitance calculation mode is selected as a result of the determination in S6, the process proceeds to S8 to perform the capacitance calculation process. The capacitance calculating unit 22 calculates the first by substituting the equation (10) or the equation (11) into the first, second total electrostatic capacitances C1 and C2, the first and second pole pitches h1 and h2, and the distances d1 and d2. At least one of the second interelectrode capacitances Cp1 and Cp2. In addition, the first two-pole pitch h1 is the target two-pole pitch.

After calculating the electrostatic capacitance between the two poles, the process moves to S9, and based on the calculated electrostatic capacitance between the two poles, the processing conditions are set using the processing condition table of Table 2. After the processing conditions are set, the process proceeds to S10, and the electric discharge machining process is started.

Next, the action and effect of the above-described electric discharge machining apparatus M will be described.

Since the first and second total electrode capacitances C1 and C2 between the measured electrode and the processed portion of the workpiece are used to calculate the processing area by using the measured first and second pole pitches h1 and h2, the measured area is high. The processing area S of the machined surface of the workpiece W is accurately determined. Further, even when it is difficult to calculate the processing area SA due to the complicated shape of the electrode advancing end surface, the first interelectrode capacitance Cp21 or the second pole which is substantially proportional to the processing area SA can be obtained with high accuracy as described above. Interstatic capacitance Cp22.

Therefore, the electric discharge machining conditions can be appropriately set based on the machining area S (or SA) or the high-precision calculation values of the first and second inter-electrode electrostatic capacitances Cp1, Cp2 (or Cp21, Cp22). Moreover, since the first and second pole pitches h1, h2 (or h21, h22) between the electrode advancing end face and the machined surface are utilized in the calculation, the height of the machining debris deposited on the machined surface can be used as an error. The distance is reflected by the values of the electrostatic capacitances Cp1 and Cp2 (or Cp21 and Cp22) between the first and second electrodes, and appropriate processing conditions can be set.

Furthermore, since the first and second total electrostatic capacitances C1, C2 (or Cp21, Cp22) actually measured and the first and second pole pitches h1, h2 (or h21, h22) are utilized, even When the machining area S (or SA) increases sharply, the high-precision machining area S (or SA) or the first and second inter-electrode capacitances Cp1 and Cp2 (or Cp21, Cp22) can be calculated. It is necessary to divide the electrodes and perform processing without causing processing defects, and the number of times of electric discharge machining can be reduced.

Since the machining condition setting unit 19 for setting the machining conditions of the electric discharge machining based on the first and second inter-electrode electrostatic capacitances Cp21 and Cp22 which replace the calculated machining area S, SA or the machining area SA is provided, it is possible to appropriately correspond The state of the processing area or the state of the two electrodes between the two electrodes of the working surface is set to an appropriate measurement cycle, electrical conditions of the electrical discharge machining, jump periods of the jump operation, and jump amount.

Since the machining area calculation unit 21 calculates the machining area S based on the equation (3), the calculation processing speed for the calculation can be reduced, and the calculation processing speed of the machining area can be accelerated.

Since the capacitance calculating unit 22 calculates the capacitances Cp21 and Cp22 between the electrodes based on the equations (9) to (11), even if the electrode advancing end surface has a complicated shape, the two poles proportional to the processing area SA can be accurately calculated. Interstatic capacitance Cp21, Cp22.

Since the processing condition setting unit 19 changes the measurement period based on the processing areas S and SA (or the first and second inter-electrode electrostatic capacitances Cp21 and Cp22 instead of the processing area SA), it is possible to change the shape suitable for the shape of the electrode advance end surface. The measurement cycle can be changed and the electrical conditions can be set, and appropriate processing conditions can be set. The processing condition setting unit 19 controls the machining current values to be supplied to the electrodes E and EA to be substantially proportional to the first and second interelectrode electrostatic capacitances Cp21 and Cp22 of the substitution processing area S, SA or the processing area SA, thereby preventing Abnormal consumption of electrodes E and EA due to excessive current supply. Thereafter, the current supplied to the electrodes E and EA is set to be equal to or lower than a predetermined current density, whereby occurrence of an abnormal situation such as a decrease in processing speed can be prevented.

[Example 2]

Next, Embodiment 2 will be described based on FIG.

The difference from the first embodiment is that the distance D from the surface of the workpiece W in the first embodiment to the processing surface is known, and the distance D in the second embodiment is unknown.

The columnar electrode EB is brought into contact with the processed surface of the workpiece W to initialize the moving position (two-pole pitch) of the electrode EB. Next, as shown in Fig. 11 (a), the electrode EB is moved upward by the Z-axis moving mechanism 4 to move the electrode EB to the first moving position. In this case, the first total electrostatic capacitance C31, the electrostatic capacitance Cp31 between the electrode advancing end surface and the processing surface, the processing area SB, the first electrode pitch h31 from the electrode advancing end surface to the processing surface, and the side of the electrode EB are set. The first total electrostatic capacitance C31 can be expressed by the following formula (12), and the electrostatic capacitance Ca between the workpiece W and the permittivity ε of the machining liquid and the distance D from the surface of the workpiece W to the processing surface. It was detected by measurement.

C31=Cp31+Ca(D-h31)/D ...(12)

However, the electrostatic capacitance between the two poles is Cp31 = εSB / h31.

Next, as shown in Fig. 11(b), the electrode EB is moved upward from the first moving position by the Z-axis moving mechanism 4 to move the electrode EB to the second moving position. At this time, if the second total electrostatic capacitance C32, the electrostatic capacitance Cp32 between the electrode advancing end surface and the processing surface, and the second electrode spacing h32 from the electrode advancing end surface to the processing surface, the second total electrostatic capacitance C32 is set. It can be represented by the following formula (13) and detected by measurement.

C32=Cp32+Ca(D-h32)/D ...(13)

However, the electrostatic capacitance between the two poles is Cp32 = εSB / h32.

Next, as shown in FIG. 11(c), the electrode EB is moved upward by the Z-axis moving mechanism 4 from the second moving position to move the electrode EB to the third moving position. At this time, if the third total electrostatic capacitance C33, the electrostatic capacitance Cp33 between the electrode advancing end surface and the processing surface, and the third electrode spacing h33 from the electrode advancing end surface to the processing surface, the third total electrostatic capacitance C33 is set. It can be represented by the following formula (14) and detected by measurement.

C33=Cp33+Ca(D-h33)/D ...(14)

However, the electrostatic capacitance between the two poles is Cp33 = εSB / h33.

When the equations (12) to (14) are solved for the machining area SB, the machining area SB can be expressed by the following equation (15):

SB=h31‧h32‧h33(h31(C32-C33)+h32(C33-C31)+h33(C31-C32))/(ε(h31-h32)(h32-h33)(h33-h31)) .. .(15)

The machining area calculation unit 21 calculates the distances D from the surfaces of the electrostatic capacitances Cp31, Cp32, and Cp33 between the two electrodes and the surface of the workpiece W to the processing surface based on the calculated machining area SB.

The discharge pulse setting unit 23 calculates the current density using the machining current value and the machining area SB detected by the machining current measuring unit 14, and controls the current density to be equal to or lower than a predetermined current density. Similarly to the first embodiment, the machining condition setting unit 19 applies the machining area SB to the machining condition table of Table 1 to set electrical processing conditions such as discharge pulses.

Next, the action and effect of the electric discharge machining apparatus M of the second embodiment will be described.

Basically, it exerts the same effects and effects as those of the first embodiment. Further, even when the distance D from the surface of the workpiece W to the processing surface is unknown, it is possible to set the appropriate polarity by detecting the two-pole pitches h31 to h33 at the first to third movement positions and the total capacitance C31 to C33. Processing conditions.

Further, although the electrode EB shown in FIG. 11 is described by taking a columnar electrode as an example, the electrode EB does not have to be in the shape of a column, and may be an electrode in which the processing area is continuously or discontinuously changed in accordance with the progress of the electric discharge machining. .

[Example 3]

Next, Embodiment 3 will be described based on Fig. 12 .

This is different from the first embodiment in that the distance D from the surface of the workpiece W in the first embodiment to the processing surface is known. In the third embodiment, the distance D is unknown and the measured two-pole pitch includes an error. Distance α. Further, the error distance α is caused by the machining debris deposited on the processing surface of the workpiece W or the backlash of the gear system of the Z-axis moving mechanism 4, etc., when the backlash is not generated, the machining surface is processed. The accumulation amount of the debris is represented by a positive value, and when the backlash is generated, the total value of the backlash amount of the negative value and the accumulation amount of the machining debris of the positive value is represented.

The columnar electrode EC is brought into contact with the processed surface of the workpiece W to initialize the moving position (two-pole pitch) of the electrode EC. Next, as shown in Fig. 12 (a), the electrode EC is moved upward by the Z-axis moving mechanism 4 to move the electrode EC to the first moving position. In this case, the first total electrostatic capacitance C41, the electrostatic capacitance Cp41 between the electrode advancing end surface and the processing surface, the processing area SC, the first electrode pitch h41 from the electrode advancing end surface to the processing surface, and the side of the electrode EC are set. The first total electrostatic capacitance C41 can be expressed by the following equation (16), the electrostatic capacitance Ca between the workpiece W, the permittivity ε of the machining liquid, the distance D from the surface of the workpiece W to the processing surface, and the error distance α. ) is indicated and detected by measurement.

C41=Cp41+Ca(D-h41-α)/D ...(16)

However, the electrostatic capacitance between the two electrodes Cp41 = εSC / (h41 + α).

Next, as shown in FIG. 12(b), the electrode EC is moved by the Z-axis moving mechanism 4 from the first moving position upward to move the electrode EC to the second moving position. At this time, if the second total electrostatic capacitance C42, the electrostatic capacitance Cp42 between the electrode advancing end surface and the processing surface, and the second electrode spacing h42 from the electrode advancing end surface to the processing surface, the second total electrostatic capacitance C42 is set. It can be represented by the following formula (17) and detected by measurement.

C42=Cp42+Ca(D-h42-α)/D ...(17)

However, the electrostatic capacitance between the two poles Cp42 = εSC / (h42 + α).

Next, as shown in FIG. 12(c), the electrode EC is moved by the Z-axis moving mechanism 4 from the second moving position to move the electrode EC to the third moving position. At this time, if the third total electrostatic capacitance C43, the electrostatic capacitance Cp43 between the electrode advancing end surface and the processing surface, and the third electrode pitch h43 from the electrode advancing end surface to the processing surface, the third total electrostatic capacitance C43 is set. It can be represented by the following formula (18) and detected by measurement.

C43=Cp43+Ca(D-h43-α)/D ...(18)

However, the electrostatic capacitance between the two poles Cp43 = εSC / (h43 + α).

Next, as shown in FIG. 12(d), the electrode EC is moved by the Z-axis moving mechanism 4 from the third moving position upward to move the electrode E to the fourth moving position. At this time, if the fourth total electrostatic capacitance C44, the electrostatic capacitance Cp44 between the electrode advancing end surface and the processing surface, and the fourth electrode spacing h44 from the electrode advancing end surface to the processing surface, the fourth total electrostatic capacitance C44 is set. It can be represented by the following formula (19) and detected by measurement.

C44=Cp44+Ca(D-h44-α)/D ...(19)

However, the electrostatic capacitance between the two poles Cp44 = εS / (h44 + α).

If the equations (16) to (19) are solved for the machining area SC, the machining area SC can be expressed by the equation (20) including the error distance α:

SC=((h41+α)×(h42+α)×(h43+α)×(h41(C42-C43)+h42(C43-C41)+h43(C41-C42)))/(ε(h41- H42)×(h41-h43)×(h43-h42)) (20)

If the error distance α is solved, it can be expressed by the following formula (21):

α=A/B ...(21)

but,

A=h41 ² (h42(h43(C42-C43)+h44(C44-C42))+h43h44(C43-C44))-h41(h42 ² (h43(C41-C43)+h44(C44-C41))+ H42(h43+h44)(h43-h44)(C42-C41)+h43h44(h43(C41-C44)+h44(C43-C41)))-h42h43h44(h42(C3-C4)+h43(C4-C2) +h44(C2-C3))

B=h41 ² (h42(C43-C44)+h43(C44-C42)+h44(C42-C43))-h41(h42 ² (C43-C44)+h43 ² (C44-C42)+h44 ² (C42- C43))+h42 ² (h43(C41-C44)+h44(C43-C41))-h42(h43 ² (C41-C44)+h44 ² (C43-C41))+h43h44(h43-h44)(C41- C42)

As shown in FIGS. 8 and 9, the jump operation calculation unit 25 sets the longer the error period α, the shorter the jump period of the electrode EC, and the larger the error distance α is, the larger the amount of movement caused by the jump is. Further, by measuring the position error of the electrode EC due to the backlash of the gear system in advance and correcting the error distance α by the backlash amount, the amount of accumulated machining debris deposited on the processing surface can be accurately calculated.

Next, the action and effect of the electric discharge machine M of the third embodiment will be described.

Basically, it exerts the same effects and effects as those of the first embodiment. Further, even when the distance D from the surface of the workpiece W to the processing surface is unknown, the two-pole pitches h41 to h4 of the first to fourth movement positions and the total capacitances C41 to C44 can be accurately calculated. By processing the area SC and setting appropriate machining conditions, it is possible to accurately calculate the machining area SC by calculating the error distance α and considering the machining debris or the backlash, and to appropriately set the machining conditions.

Further, although the electrode EC shown in FIG. 12 is described by taking a columnar electrode as an example, the electrode is not necessarily required to have a columnar shape, and may be an electrode in which the processing area is continuously or discontinuously changed in accordance with the progress of the electric discharge machining.

[Embodiment 4]

Next, a fourth embodiment will be described based on Fig. 13 .

This is different from the first embodiment in that the distance D from the surface of the workpiece W in the first embodiment to the processing surface is known. In the fourth embodiment, the distance D is unknown, and the measured two-pole pitch includes an error. The distance α and the electrode advancing end face have a complicated shape.

The columnar electrode ED having the angle θ (0° < θ < 90°) between the electrode advancing end surface and the electrode axis (vertical surface) is brought into contact with the processed surface of the workpiece W to move the electrode ED ( Two-pole spacing) initialization. Next, as shown in FIG. 13(a), the electrode ED is moved upward by the Z-axis moving mechanism 4, and the electrode ED is moved to the first moving position. At this time, it is assumed that the first total electrostatic capacitance C51, the electrostatic capacitance Cp51 between the electrode advancing end surface and the processing surface, the processing area SD, the first electrode pitch h51 from the electrode advancing end surface to the processing surface, and the side of the electrode ED The electrostatic capacitance Ca between the workpiece W, the permittivity ε of the machining liquid, the distance D from the surface of the workpiece W to the processing surface, the error distance α, and the angle θ between the electrode advancing end surface and the electrode, The total electrostatic capacitance C51 can be expressed by the following formula (22) and detected by measurement.

C51=εSD/((h51+α)sinθ)+Ca(D-h51-α)/D (22)

However, the electrostatic capacitance between the two poles Cp51 = εSD / ((h51 + α) sin θ).

Next, as shown in Fig. 13 (b), the electrode ED is moved upward by the Z-axis moving mechanism 4 from the first moving position to move the electrode ED to the second moving position. At this time, if the second total electrostatic capacitance C52, the electrostatic capacitance Cp52 between the electrode advancing end surface and the processing surface, and the second electrode spacing h52 from the electrode advancing end surface to the processing surface, the second total electrostatic capacitance C52 is set. It can be represented by the following formula (23) and detected by measurement.

C52=εSD/((h52+α)sinθ)+Ca(D-h52-α)/D (23)

However, the electrostatic capacitance between the two poles Cp52 = εSD / ((h52 + α) sin θ).

Next, as shown in FIG. 13(c), the electrode ED is moved by the Z-axis moving mechanism 4 from the second moving position to move the electrode ED to the third moving position. At this time, if the third total electrostatic capacitance C53, the electrostatic capacitance Cp53 between the electrode advancing end surface and the processing surface, and the third electrode pitch h53 from the electrode advancing end surface to the processing surface, the third total electrostatic capacitance C53 is set. It can be represented by the following formula (24) and detected by measurement.

C53=εSD/((h53+α)sinθ)+Ca(D-h53-α)/D (24)

However, the electrostatic capacitance between the two poles Cp53 = εSD / ((h53 + α) sin θ).

Next, as shown in FIG. 13(d), the electrode ED is moved upward by the Z-axis moving mechanism 4 from the third moving position to move the electrode ED to the fourth moving position. At this time, if the fourth total electrostatic capacitance C54, the electrostatic capacitance Cp54 between the electrode advancing end surface and the processing surface, and the fourth electrode spacing h54 from the electrode advancing end surface to the processing surface, the fourth total electrostatic capacitance C54 is set. It can be represented by the following formula (25) and detected by measurement.

C54=εSD/((h54+α)sinθ)+Ca(D-h54-α)/D (25)

However, the electrostatic capacitance between the two poles Cp54 = εSD / ((h54 + α) sin θ).

If the equations (22) to (25) are solved for the machining area SD, the machining area SD can be expressed by the equation (26) including the error distance α:

SD=((h51+α)×(h52+α)×(h53+α)×(h51(C52-C53)+h52(C53-C51)+h53(C51-C52))×sinθ)/(ε( H51-h52)×(h52-h53)×(h53-h51)) (26)

Further, by solving equations (22) to (25) for the error distance α, the error distance α can be obtained.

Here, by substituting the above formula (26) into the equation of the interelectrode capacitance Cp51, the interelectrode capacitance Cp51 at the first movement position d51 can be expressed by the following formula (27):

Cp51=((h52+α)×(h53+α)×(h51(C52-C53)+h52(C53-C51)+h53(C51-C52)))/((h51-h52)×(h52-h53 )×(h53-h51)) ...(27)

Similarly, the electrostatic capacitances Cp52 to Cp54 between the two electrodes can be calculated based on the processing area SD.

According to the above, even in the case where the electrode ED of the forward end surface having a complicated shape such as the angle θ is provided between the electrode advancing end surface and the axis of the electrode ED, the electrostatic capacitance between the electrodes can be calculated by the equation without θ. Cp51 ~ Cp54. Further, by calculating the error distance α, it is possible to set processing conditions in which processing debris or backlash are taken into consideration. Further, although the electrode ED of FIG. 13 is described by taking a columnar electrode as an example, the electrode is not necessarily required to have a columnar shape, and may be an electrode in which the processing area is continuously or discontinuously changed in accordance with the progress of the electric discharge machining. Further, it may be an electrode having a plurality of inclined faces having equal inclination angles or different inclination angles on the front end face of the electrode.

Hereinafter, a modification in which the embodiment is partially changed will be described.

(1) In the above-described embodiment, an example in which the electrode is moved in the vertical direction and processed is described. However, the present invention is also applicable to the processing of moving the electrode horizontally in the horizontal direction or the front-rear direction. Electric discharge machining device.

(2) In the above-described embodiment, an example in which the feeding mechanism of the electrodes in the X, Y, and Z-axis directions by the ball screw mechanism, the motor, and the like has been described, as long as the electrode can be at least X, Y, The Z-axis direction may be moved, and the feed mechanism may be constituted by a linear motor or the like.

(3) In the above-described embodiment, the processing condition setting unit has described an example in which the peak current value, the pulse-on time (pulse width), and the pulse-off time are controlled to be equal to or lower than a predetermined reference current density, but for processing. The roughness of the surface is stabilized, and can be controlled to be below the reference current density by setting the pulse on time to a certain width (time) and adjusting the pulse off time.

(4) In the above-described embodiment, an example in which the reference current density is 5 A/cm ² and 25 A/nF is described for the case where the electrode is copper and the workpiece is a combination of steel, but the electrode and the workpiece are When the combination is different materials, set the other processing conditions table. Moreover, it is also possible to prepare a plurality of processing condition tables in advance for a combination of the electrode material and the workpiece material, and select a processing condition table that matches the combination of the electrode and the workpiece.

(5) In the above-described embodiment, an example in which the two-pole pitch and the total electrostatic capacitance at the first to fourth moving positions are measured has been described, but the number of times of measurement may be appropriately set depending on the shape of the machined surface, and the arithmetic calculation may be performed. The ability to determine the pole spacing and total electrostatic capacity at more moving locations.

(6) In the above embodiment, an example of a calculation mode switching switch provided with a switchable processing area calculation mode and an electrostatic capacitance calculation mode has been described, but it may be configured to calculate both the processing area and the electrostatic capacitance between the two electrodes. It can also be configured to automatically select any one based on the processing program.

(7) In the above-described embodiment, an example in which the processing area based on the calculation of the total electrostatic capacitance and the calculation cycle of the processing area is used as the calculation result, etc., is described. However, it is also possible to set a certain distance each time. The workpiece is processed to perform measurement and calculation.

(8) Others, as long as they are those skilled in the art, may be implemented in various ways in which the various modifications are added to the embodiments, and the present invention also includes such variations. .

[Industrial Availability]

According to the present invention, in an electric discharge machining apparatus that discharges between an electrode and a workpiece to perform electrical discharge machining on a workpiece, the machining area of the electric discharge machining surface, or the electrode advancing end surface and the workpiece are accurately calculated in the electric discharge machining. The electrostatic capacitance between the two surfaces between the processed surfaces is set to a suitable processing condition corresponding to the change in the processing area and the generation of the machining debris to improve the production efficiency and the processing quality of the electric discharge machining.

1‧‧‧Processing machine body

2‧‧‧Control device

3‧‧‧ head

4‧‧‧Z-axis moving mechanism

5‧‧‧X-axis moving mechanism

6‧‧‧Y-axis moving mechanism

7‧‧‧Processing tank

8‧‧‧Abutment

9‧‧‧ Calculation and Processing Department

10‧‧‧Processing power circuit

11‧‧‧Discharge Detection Department

12‧‧‧Electrostatic capacity measurement department

12a‧‧‧Constant current circuit

12b‧‧‧ pulse output circuit

12c, 12s‧‧‧ transistor

12d‧‧‧resistance

12e‧‧‧voltage detection circuit

12f‧‧‧ capacitor

12v‧‧‧output terminal

12x‧‧‧ side terminal

13‧‧‧Discharge Control Department

14‧‧‧Processing Current Measurement Department

14a‧‧‧ galvanometer

15‧‧‧calculation mode switch

16‧‧‧Location Control Department

17‧‧‧Electrostatic capacity measurement control department

18‧‧‧calculation device

19‧‧‧Processing Condition Setting Department

20‧‧‧X, Y Control Department

21‧‧‧Processing Area Calculation Department

22‧‧‧Electrostatic Capacity Calculation Department

23‧‧‧Discharge pulse setting section

24‧‧‧Measurement Period Calculation Department

25‧‧‧ Jump Action Department

E~ED‧‧‧electrode

M‧‧‧Discharge processing device

W‧‧‧Processed objects

26‧‧‧ Cable

1 is an overall view of an electric discharge machining apparatus according to Embodiment 1 of the present invention; Figure 2 is a block diagram of an electric discharge machining apparatus; 3 is a circuit diagram showing a capacitance measuring unit; 4 is an explanatory view for explaining a voltage of a capacitance between an electrode and a processed surface of a workpiece; 5(a) and 5(b) are diagrams respectively illustrating elements for processing area calculation; 6(a) and 6(b) are diagrams for explaining a detection procedure of a permittivity of a working fluid; 7(a) and 7(b) are diagrams respectively illustrating elements used for capacitance calculation between two electrodes; Figure 8 is a diagram showing a graph of a skip period; Figure 9 is a line diagram showing a jump amount map; Figure 10 is a flow chart of processing condition setting processing; 11(a), (b), and (c) are diagrams each explaining elements of the processing area calculation used in the second embodiment; Figs. 12(a), (b), (c), and (d) are respectively A diagram illustrating elements used in the processing area calculation of the third embodiment; and FIGS. 13(a), (b), (c), and (d) are respectively explained for the capacitance calculation between the two electrodes for the fourth embodiment. The diagram of the element.

1. . . Processing machine body

2. . . Control device

3. . . head

4. . . Z-axis moving mechanism

5. . . X-axis moving mechanism

6. . . Y-axis moving mechanism

7. . . Processing tank

9. . . Calculation processing department

10. . . Processing power circuit

11. . . Discharge detection unit

12. . . Electrostatic capacity measuring unit

13. . . Discharge control unit

14. . . Processing current measurement unit

14a. . . Ammeter

15. . . Calculation mode switch

16. . . Position control unit

17. . . Electrostatic capacity measurement control unit

18. . . Arithmetic device

19. . . Processing condition setting unit

20. . . X, Y control department

twenty one. . . Processing area calculation department

twenty two. . . Electrostatic capacity calculation department

twenty three. . . Discharge pulse setting unit

twenty four. . . Measurement period calculation department

25. . . Jump action calculation department

E. . . electrode

M. . . Electric discharge machining device

W. . . Processed object

Claims (10)

An electric discharge machining apparatus that supplies a machining liquid at a gap between an electrode and a workpiece, and applies a discharge pulse to the workpiece from the electrode to perform electric discharge machining on the workpiece, and is characterized in that: a moving device is provided The electrode can be moved, and the distance between the advancing end surface of the processing direction of the electrode and the processing surface of the workpiece can be changed; the moving distance detecting device detects the moving distance of the electrode; and the electrostatic capacitance measuring device can measure a total electrostatic capacitance between the processed portion of the workpiece and the electrode facing the electrode, and a calculation device interrupting the electrical discharge machining at a measurement cycle timing after the start of each electrical discharge machining Moving the electrode to a plurality of positions through the moving device, and using a plurality of two-pole spacing detected by the moving distance detecting device and a plurality of total static electricity measured by the electrostatic capacitance measuring device Capacity, to calculate the processing area of the processing surface or the capacitance between the two poles proportional to the processing area; and processing conditions Setting means, based on the inter-calculation of the machining area by the calculation means or said bipolar electrostatic capacitance setting associated with the EDM machining pulse conditions. The electric discharge machining apparatus according to claim 1, wherein the machining condition setting device has a peak current, a pulse ON time, and a pulse OFF time associated with an electric discharge machining pulse by using the machining area as a parameter. The first processing condition table and the second processing condition table in which the peak current, the pulse ON time, and the pulse OFF time associated with the electric discharge machining pulse are set in advance using the electrostatic capacitance between the two electrodes as a parameter. The electric discharge machining apparatus according to claim 1 or 2, wherein the calculation device is configured to: a first two-pole pitch h1 measured in a state in which the electrode is moved to a first movement position; The first total electrostatic capacitance C1, the second two-pole pitch h2 measured in a state where the electrode is moved to the second movement position, and the second total electrostatic capacitance C2, and the state in which the electrode is moved to the third movement position When the third two-pole pitch h3 and the third total electrostatic capacitance C3, the permittivity ε of the working fluid, and the processing area S are measured, S=h1‧h2‧h3 (h1(C2-C3)+h2(C3- The processing area is calculated by the equation represented by C1)+h3(C1-C2))/(ε(h1-h2)(h2-h3)(h3-h1)). The electric discharge machining apparatus according to claim 1 or 2, wherein the calculation device is configured to: determine a first two-pole pitch h1 in a state in which the electrode is moved to a first movement position And the first total electrostatic capacitance C1, the second two-pole pitch h2 and the second total electrostatic capacitance C2 measured in a state where the electrode is moved to the second movement position, and the state in which the electrode is moved to the third movement position The measured third two-pole pitch h3 and the third total electrostatic capacitance C3, the fourth two-pole pitch h4 and the fourth total electrostatic capacitance C4 measured in a state where the electrode is moved to the fourth moving position, and the error distance between the two-pole pitch When α, the permittivity ε of the working fluid and the processing area S, use S=((h1+α)×(h2+α)×(h3+α)×(h1(C2-C3)+h2(C3 -C1)+h3(C1-C2)))/(ε(h1-h2)×(h1-h3)×(h3-h2))α=A/B only, A=h1 ² (h2(h3(C2) -C3)+h4(C4-C2))+h3h4(C3-C4))-h1(h2 ² (h3(C1-C3)+h4(C4-C1))+h2(h3+h4)(h3-h4 )(C2-C1)+h3h4(h3(C1-C4)+h4(C3-C1)))-h2h3h4(h2(C3-C4)+h3(C4-C2)+h4(C2-C3))B= H1 ² (h2(C3-C4)+h3(C4-C2)+h4(C2-C3))-h1(h2 ² (C3-C4)+h3 ² (C4-C2)+h4 ² (C2-C3))+h2 ² (h3(C1-C4)+h4(C3-C1))-h2(h3 ² (C1-C4)+h4 ² (C3-C1) The equation represented by +h3h4(h3-h4)(C1-C2) is used to calculate the processing area. The electric discharge machining apparatus according to claim 1 or 2, wherein the calculation device is configured to: determine a first two-pole pitch h1 in a state in which the electrode is moved to a first movement position And the first total electrostatic capacitance C1, the second two-pole pitch h2 and the second total electrostatic capacitance C2 measured in a state where the electrode is moved to the second movement position, and the state in which the electrode is moved to the third movement position The measured third two-pole pitch h3 and the third total electrostatic capacitance C3, the fourth two-pole pitch h4 and the fourth total electrostatic capacitance C4 measured in a state where the electrode is moved to the fourth moving position, and the electrode advancing end face and the electrode When the angle θ between the axes, the error distance α of the two-pole pitch, the permittivity ε of the machining fluid, the machining area S, and the electrostatic capacitance C between the two poles, use S=((h1+α)×( H2+α)×(h3+α)×(h1(C2-C3)+h2(C3-C1)+h3(C1-C2))×sinθ)/(ε(h1-h2)×(h2-h3) ×(h3-h1)) α=A/B only, A=h1 ² (h2(h2(C2-C3)+h4(C4-C2))+h3h4(C3-C4))-h1(h2 ² (h3 (C1-C3)+h4(C4-C1))+h2(h3+h4)(h3-h4)(C2-C1)+h3h4(h3(C1-C4)+h4(C3-C1)))-h 2h3h4(h2(C3-C4)+h3(C4-C2)+h4(C2-C3)) B=h1 ² (h2(C3-C4)+h3(C4-C2)+h4(C2-C3))- H1(h2 ² (C3-C4)+h3 ² (C4-C2)+h4 ² (C2-C3))+h2 ² (h3(C1-C4)+h4(C3-C1))-h2(h3 ² ( C1-C4)+h4 ² (C3-C1))+h3h4(h3-h4)(C1-C2) C=εS/((h1+α)sinθ) or C=εS/((h2+α)sinθ) The processing area and the electrostatic capacitance between the two poles are calculated by the equation represented by C=εS/((h3+α)sinθ) or C=εS/((h4+α)sinθ). The electric discharge machining apparatus according to claim 1 or 2, wherein the processing condition setting means changes the measurement period based on the calculated processing area or the electrostatic capacitance between the two poles, and the measurement period is The electrostatic capacitance measuring device measures the total electrostatic capacitance between the electrode and the processed portion of the workpiece to change the electrical discharge machining conditions. The electric discharge machining apparatus according to claim 1 or 2, wherein the machining condition setting device sets a machining current for the electrode to be set to the calculated machining area or static electricity between the two poles. The capacity is substantially proportional. The electric discharge machining apparatus according to claim 7, wherein the machining condition setting device sets the current density of the machining current to be equal to or lower than a predetermined current density. The electric discharge machining apparatus according to claim 8, wherein the machining condition setting device is provided with a discharge that sets a discharge pulse corresponding to a machining current supplied to the electrode, the machining area, or an electrostatic capacitance between the two electrodes. Pulse setting device. The electric discharge machining apparatus according to claim 4, wherein the machining condition setting device has a jump motion calculation for setting at least one of a jump period and a jump amount of the jump motion based on the error distance α of the two-pole pitch. Device.