KR20120094904A - Electrical discharge machining device - Google Patents

Abstract

The electric discharge machining apparatus (M) of the present invention includes a Z-axis moving mechanism (4) capable of precisely moving the electrode (E), a position control unit (16) for detecting a moving distance of the electrode (E), and a workpiece. The capacitance measuring unit 12 and the capacitance measuring control unit 17 capable of measuring the total capacitance between the machining portion of (W) and the electrode E, and the Z-axis moving mechanism 4 during discharge processing. The electrode E is moved to the first and second moving positions, and the first and second inter-pole distances h1 and h2 detected by the position controller 16 and the capacitance measuring unit 12 and the capacitance measurement. Between the processing area calculating part 21 and the electrode advance cross section and processing surface which calculate the processing area S of a processing surface using the 1st, 2nd total capacitance C1, C2 measured by the control part 17. And a capacitance calculating section 22 for calculating the first and second inter-pole capacitances Cp1 and Cp2. By the above, the electrical processing conditions, such as a discharge pulse, are set based on the processing area S or the 1st, 2nd intercapacitance capacitance Cp1, Cp2, and the machining conditions are changed by the appropriate measuring period according to the interphase states. To control the jump operation.

Description

ELECTRICAL DISCHARGE MACHINING DEVICE

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electric discharge machining apparatus for discharging a machining surface of a workpiece facing the forward end face of the electrode by discharging between the electrode and the workpiece. The present invention relates to an electric discharge machining apparatus which calculates an appropriate interelectrode capacitance with good accuracy and sets an appropriate processing condition.

Background Art Conventionally, a work has been performed in which a workpiece is processed into an electrode-like shape by opposing an electrode and a workpiece, discharging the gap between the electrode forward direction in the processing direction of the electrode and the workpiece surface. In such discharge processing, machining speed, surface roughness, processing shape accuracy, and electrode consumption are determined by electrical processing conditions such as peak current value of discharge current and discharge pulse width (pulse on time, off time). Processing characteristics related to the back are greatly affected. That is, when a large processing current is sent for a small processing area, breakage or abnormal consumption of the electrode occurs, and a small processing current is sent for a large processing area, and the processing speed becomes extremely slow. Machining conditions are set based on the machining area.

In the electrical discharge machining apparatus described in Patent Document 1, data of a processing depth and a processing width of a workpiece are prepared in advance, and electrodes are moved during processing to detect widths in the X-axis direction and Y-axis direction of the machining site, respectively. The processing area is calculated, and the discharge gap (interval distance) is set from this processing area.

In the electrical discharge machining apparatus described in Patent Document 2, the electrostatic capacitance detecting means capable of detecting the total capacitance between the electrode and the processing portion (the portion facing the electrode side surface and the lower surface of the electrode) of the workpiece is provided. When this is increased, the voltage polarity is configured to be switched. By lowering the applied voltage between the poles to reduce the distance between the poles and increasing the capacitance between the poles, it is possible to suppress the consumption of the electrodes and at the same time prevent the decrease in the processing speed.

In the discharge processing apparatus described in Patent Literature 3, a pulse discrimination unit for discriminating between effective discharge pulses and invalid discharge pulses, a traveling amount measuring device for measuring an amount of movement L in the axial direction of the processing, and the number of discharge pulses The processing area S is calculated based on the division unit for dividing (n) by the progress amount L of the unit time, the removal volume v by the single discharge, and the division data (n / L). The processing area calculating part is provided. The machining area calculating unit calculates the machining area by expressing the machining area during the discharge machining by the removal volume (v) and division data (n / L) by the single discharge and the following equation, and the machining current value is determined by the machining area. Machining conditions are changed to be nearly proportional. When the processing amount is set to V, it can be expressed as V = S? L = v? N, that is, S = v? N / L.

Japanese Patent Laid-Open No. 2002-172526 Japanese Patent Laid-Open No. 2000-84737 Japanese Patent Laid-Open No. H9-38829

In the electric discharge machining apparatus of the said patent document 1, in order to move an electrode to an X-axis direction and a Y-axis direction during a process, it is necessary to perform a detection operation for detecting a process area separate from the machining operation required for an electric discharge machining process. have. Furthermore, when the electrode has a simple forward cross-section in the machining progress direction, the error of the machining area can be reduced to a small extent, but when the forward cross-section is complicated, that is, when a complicated machining is formed in which the unevenness is formed in the forward cross-section. It is difficult to calculate the machining area with good precision.

In the electric discharge machining apparatus of the said patent document 2, since the capacitance of the process part of an electrode and a to-be-processed object is detected, the capacitance between the electrode side surface and a to-be-processed object which does not actually contribute to a process is included in the capacitance detection value. have. That is, in order to set the machining conditions with good accuracy, the capacitance between the forward end surface in the machining progress direction of the electrode and the machined surface of the workpiece (except the capacitance between the electrode side surface and the workpiece corresponding to the error) Capacity).

In the above discharge processing apparatus, the processing liquid flows through the gap between the electrode and the workpiece, and the processing waste is discharged. However, the deeper the processing depth, the less the processing waste is discharged from the gap.

In the discharge processing apparatus of Patent Literature 3, when the processing waste is deposited on the processing surface, an effective discharge is generated between the processing waste and the electrode, so that the error of the removal volume v and the number of effective discharge pulses n Gets bigger For this reason, the deeper the machining depth, the larger the error of the machining area, and the larger the deviation from the appropriate value of the machining conditions set based on the machining area.

In order to perform electric discharge machining with good machining accuracy, it is necessary to set machining conditions in consideration of error factors such as machining waste deposited on the machining surface of the workpiece and backlash of the gear mechanism of the electrode moving means. . However, there is no suggestion on the technique of obtaining the inter-pole distance between the electrode and the working surface by setting such an error factor and setting the processing conditions.

On the other hand, in the case where the forward end surface of the electrode has a complicated shape having irregularities, it is not easy to suddenly change the processing conditions (discharge current or discharge pulse) by reliably detecting the processing area at the site where the processing area during the discharge machining changes rapidly. Thus, conventionally, a method of dividing an electrode into a plurality of processes and processing by a plurality of discharge machining processes is also frequently used. In this case, however, discharge processing must be performed for the same number of times as the number of divided electrodes, which causes problems such as an increase in the discharge processing time for one workpiece and an increase in the price of the electrode.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an electric discharge machining apparatus capable of calculating the processing area of the machining surface or the interelectrode capacitance between the electrode forward end face and the machining surface with good accuracy during discharge machining, machining dregs, or a moving drive mechanism for moving the electrode. The present invention provides an electric discharge machining apparatus capable of setting processing conditions including backlash and the like, and an electric discharge machining apparatus capable of reducing the number of electric discharge machining operations without generating machining defects.

(1) The discharge machining factory of the present invention supplies a processing liquid to a gap between an electrode and a workpiece, and applies a discharge pulse from the electrode to the workpiece to discharge-process the workpiece. A moving means capable of moving the electrode and changing the distance between the electrodes from the processing forward direction end surface of the electrode to the processing surface of the workpiece, and a movement distance for detecting the movement distance of the electrode. Detection means, capacitance measuring means capable of measuring the total capacitance between the electrode and the processing portion of the workpiece to be opposed to each other with the gap therebetween, and the discharge at each measurement cycle timing after discharge processing starts. In the state where the processing was interrupted, the electrodes were moved to a plurality of positions by the moving means, and the plurality of gaps detected by the moving distance detecting means. Calculation means for calculating the interfacial capacitance proportional to the machining area or the machining area of the machined surface, using a plurality of total capacitances measured by the controller and the capacitance measuring means; And processing conditions setting means for setting processing conditions relating to the discharge processing pulses based on the processing area or the interelectrode capacitance.

Some of the components of the present invention may be configured as follows.

(2) The processing condition setting means includes: a first processing condition table in which the peak current, the pulse ON time, and the pulse OFF time relating to the discharge machining pulse are set in advance, using the processing area as a parameter; And a second processing condition table in which the peak current, the pulse ON time, and the pulse OFF time relating to the discharge machining pulse are preset.

(3) In the above (1) or (2), the computing means removes the first inter-pole distance h1 and the first total capacitance C1 and the electrode measured in a state where the electrode is moved to the first moving position. 2nd interpole distance h2 and 2nd total capacitance C2 measured in the state which moved to 2 moving positions, 3rd interpole distance h3 and 3rd total capacitance C3 which were measured in the state which moved said electrode to 3rd moving position, When the dielectric constant ε of the processing liquid is set and the processing area is S,

S = h1? H2? H3 (h1 (C2-C3) + h2 (C3-C1) + h3 (C1-C2)) / (ε (h1-h2) (h2-h3) (h3-h1)) The machining area is calculated using the following equation.

(4) In the above (1) or (2), the computing means removes the first inter-pole distance h1 and the first total capacitance C1 and the electrode measured while the electrode is moved to the first moving position. Distance between the second pole h2 and the second total capacitance C2 measured in the state of moving to the second movement position; distance between the third pole h3 and the third total capacitance C3, measured while the electrode is moved to the third movement position; When the fourth interpolar distance h4 and the fourth total capacitance C4 measured in the state where the electrode is moved to the fourth moving position, the error distance α of the interpolar distance, and the dielectric constant ε of the processing liquid are set to the processing area S,

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

Where 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 processing area is calculated using the equation shown by.

(5) The method according to (1) or (2), wherein the computing means removes the first inter-pole distance h1 and the first total capacitance C1 and the electrode measured while the electrode is moved to the first moving position. The second inter-pole distance h2 and the second total capacitance C2 measured in the state of moving to the second movement position, the third inter-pole distance h3 and the third total capacitance C3, measured in the state of moving the electrode to the third movement position; The fourth inter-pole distance h4 and the fourth total capacitance C4 measured while the electrode is moved to the fourth moving position, the angle θ between the electrode forward end face and the axis of the electrode, the error distance α between the poles, and the dielectric constant of the processing liquid. When ε is set and the processing area S and the interelectrode capacitance C 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

Where 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 processing area and inter-pole capacitance are calculated using the equation shown by.

(6) The processing condition setting means according to any one of (2) to (5), wherein the processing condition setting means measures the total capacitance between the electrode and the processing part of the workpiece by the capacitance measuring means to determine the discharge processing condition. The changing measurement period is changed based on the calculated machining area or inter-pole capacitance.

(7) In any one of (2) to (5), the processing condition setting means sets the processing current supplied to the electrode so as to be substantially proportional to the calculated processing area or inter-pole capacitance.

(8) In (7), the processing condition setting means sets the current density of the processing current to a predetermined current density or less.

(9) In the above (8), the processing condition setting means includes discharge pulse setting means for setting the processing current supplied to the electrode and the discharge pulse corresponding to the processing area or the interelectrode capacitance.

(10) The jump operation calculation means according to (4), wherein the processing condition setting means sets at least one of a jump period and a jump amount of the jump operation based on the error distance α of the inter-pole distance. Has

According to the present invention, there is provided a moving means capable of moving an electrode, a moving distance detecting means for detecting a moving distance of the electrode, a capacitance measuring means capable of measuring a total capacitance between the electrode and a workpiece, and At the timing of the measurement cycle after the start of the discharge machining, the electrode is moved to a plurality of positions while the discharge machining is interrupted, and the plurality of interpolar distances detected and the measured total capacitance are applied to the machining area or the machining area of the machining surface. Since the calculating means for calculating the proportional interpolar capacitance and the processing condition setting means for setting the processing conditions for the discharge processing pulse based on the processing area calculated by the calculating means or the interpolar capacitance, The same effect can be obtained.

The interfacial capacitance proportional to the processing area or the processing area of the processing surface of the workpiece opposite to the forward end surface of the electrode can be calculated with good accuracy. That is, since the processing area or inter-pole capacitance is calculated using the inter-pole distance at the plural positions at which the electrodes are moved and the total capacitance between the electrode and the processing site of the workpiece, Capacitance between the poles can be calculated with good accuracy, and based on the machining area obtained in the state of discontinuing the discharge machining after the start of discharge processing or the calculation value of the high-precision capacitance between the poles, the change of the machining area and the generation of machining waste, etc. According to the inter-pole state of, the processing conditions related to the discharge machining pulse can be set appropriately.

In addition, since the measured total capacitance and the inter-pole distance are used, even if a sudden increase in the machining area occurs, the machining area or inter-electrode capacitance can be calculated with good precision, and the machining is performed without dividing the electrode. It is possible to process with good precision without causing defects, and furthermore, the number of discharge machining can be reduced.

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

According to the above configuration (3), even when the distance from the surface of the workpiece to the machining surface is unknown, the load of the calculation processing for calculating the machining area can be reduced, so that the calculation processing speed is high and the calculation of the machining area is performed. You can run

According to the above configuration (4), even when the distance from the surface of the workpiece to the machining surface is unknown, the calculation of the machining area and the calculation of the error distance can be performed. In addition, by calculating the error distance, it is possible to set processing conditions in consideration of processing waste, backlash, and the like.

According to the above configuration (5), even when the distance from the surface of the workpiece to the processing surface is unknown, the inter-electrode capacitance in proportion to the processing area as the inter-electrode capacitance between the electrode advance end formed in a complicated shape and the processing surface and Accurate calculation of the error distance can be performed. Further, by calculating the error distance, it is possible to set the processing conditions in consideration of processing waste, backlash and the like.

According to the configuration of (6), the measurement period for changing the discharge processing condition by measuring the total capacitance between the electrode and the workpiece of the workpiece by the capacitance calculating means is changed based on the processing area or the inter-pole capacitance. Therefore, the measurement period can be set so as to follow the shape change of the electrode advance cross section, and an appropriate electric discharge machining condition can be set.

According to the configuration of (7) above, since the processing current value supplied to the electrode is controlled to be substantially proportional to the processing area or the inter-pole capacitance calculated by the processing condition setting means, abnormal consumption of the electrode due to the excessive supply of current Can be prevented.

According to the above arrangement (8), the processing condition setting means controls the current density to be less than or equal to the predetermined current density, and thus can prevent problems such as a decrease in processing speed.

According to the configuration of (9) above, the discharge pulse setting means can set the processing current value supplied to the electrode and the discharge pulse corresponding to the processing area or the inter-pole capacitance.

According to the above configuration (10), since the jump operation calculating means for setting at least one of the jump period and the jump amount of the jump operation based on the error distance of the distance between the poles is provided, the processing residue generated by the machining is processed on the machining surface. Can be reliably excluded, and the fall of the processing speed can be prevented.

1 is an overall view of a discharge machining apparatus according to a first embodiment of the present invention.
2 is a block diagram of an electric discharge machining apparatus.
3 is a circuit diagram illustrating a capacitance measuring unit.
It is explanatory drawing explaining the voltage of the capacitor | condenser between an electrode and the process surface of a to-be-processed object.
5 (a) and 5 (b) are diagrams for describing specifications for calculating the machining area, respectively.
6 (a) and 6 (b) are diagrams for explaining the procedure for detecting the dielectric constant of the processing liquid.
7 (a) and 7 (b) are diagrams describing specifications for calculating the inter-pole capacitance, respectively.
8 is a diagram showing a jump period map.
9 is a diagram showing a jump amount map.
10 is a flowchart of processing condition setting processing.
11A, 11B, and 11C are diagrams for describing specifications for calculating the machining area according to the second embodiment.
(A), (b), (c), (d) is a figure explaining the specifications for the calculation of the processing area which concerns on Example 3, respectively.
13A, 13B, 13C, and 13D are diagrams for describing specifications for calculating the inter-pole capacitance according to the fourth embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on an Example.

(Example 1)

EMBODIMENT OF THE INVENTION Hereinafter, the Example of this invention is described based on FIG.

As shown in FIG. 1, the electric discharge machining apparatus M supplies the processing liquid to the gap between the electrode E and the workpiece W, and discharges discharge pulses from the electrode E to the workpiece W. FIG. It is an apparatus which applies and discharge-processes the to-be-processed object W. This electric discharge machining apparatus M has the processing apparatus main body 1, the control apparatus 2, and peripheral devices, such as the processing liquid tank 7. As shown in FIG. The main body 1 of the machine 1 includes a head 3 equipped with an electrode E and a Z-axis moving mechanism 4 as a transfer device capable of reciprocating the head 3 in the vertical direction (Z-axis). ), An X-axis moving mechanism 5 capable of horizontally reciprocating the processing liquid tank 7 containing the workpiece W in the horizontal direction (X axis) of FIG. 1, and the processing liquid tank 7 Y-axis moving mechanism 6 capable of horizontally reciprocating in the front-rear direction (Y-axis) orthogonal to the left-right direction, and a processing liquid tank for accommodating the workpiece W and storing the processing liquid 7 ), A base 8, a cable 25, or the like. The electrode E is attached to an attachment plate detachably equipped at the lower end of the head 3.

The Z-axis moving mechanism 4 is composed of a pair of Z-axis feed guides, a ball screw mechanism, a Z-axis motor, and the like, which are mounted on the base 8 and extend along the Z-axis direction. The head 3 is driven to move in the Z-axis direction in accordance with the drive of the Z-axis motor which is numerically controlled.

The X-axis moving mechanism 5 is composed of an X-axis movable table, a pair of X-axis feed guides extending along the X-axis direction provided in the base 8, a ball screw mechanism, an X-axis motor, and the like. According to the drive of the X-axis motor numerically controlled by the apparatus 2, the X-axis movable platform is driven to move 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, a ball screw mechanism, a Y-axis motor, and the like extending along the Y-axis direction provided in the X-axis movable table. According to the drive of the Y-axis motor numerically controlled by the controller 2, the Y-axis movable table and the processing liquid tank 7 are driven to move in the Y-axis direction.

The processing liquid tank 7 is fixed to the upper end of the Y-axis movable table of the Y-axis moving mechanism 6. The control apparatus 2 is provided adjacent to the processing machine main body 1, and supplies electric power and a control signal to the processing machine main body 1 via the cable 25. As mentioned above, the electrode E and the to-be-processed object W are comprised so that relative movement is possible in the X- and Y-axis directions parallel to a 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 the workpiece ( It is possible to change the distance between the poles to the machining surface of W). Hereinafter, the surface portion of the workpiece W facing the machining advance direction end surface of the electrode E is defined as the machining surface of the workpiece W, and the area of the machining surface is defined as the machining area. On the other hand, although the electrode E is made of copper or graphite, although the workpiece W is a cemented carbide, it may be made from copper tungsten.

As shown in Fig. 2, the control device 2 is composed of a computer including a CPU, a ROM, a RAM, an interface, and the like, and an arithmetic processing unit 9 for executing various arithmetic processing, and a processing power supply for supplying DC power for electric discharge machining. The workpiece W which faces the circuit 10, the discharge detection part 11 which detects the discharge state which generate | occur | produced between the electrode E, and the to-be-processed object W, and the gap between the side surface and the lower surface of the electrode E is opposed. The capacitance measuring unit 12 for measuring the capacitance (hereinafter referred to as "total capacitance") between the machining portion of the electrode and the electrode (E), and the discharge pulse for the discharge processing the electrode (E) and the workpiece And a discharge control section 13, a processing current measuring section 14, a calculation mode changeover switch 15, and the like, which are supplied to (W). On the other hand, the capacitance between the forward end surface of the electrode E and the processing surface of the workpiece W opposed to the forward end surface is referred to as interpolar capacitance and will be described below.

As shown in FIG. 3, the capacitance measuring unit 12 includes a switching transistor 12s mounted between a power supply line from a power supply Vc, a constant current circuit 12a connected to the power supply line, A pulse output circuit 12b, a transistor 12c, a resistor 12d, and a voltage detection circuit 12e, which are connected to the feed line and are capable of outputting a pulse of a predetermined period (same pulse ON time and OFF time). Etc. are provided.

The base side terminal 12x of the transistor 12s and the output terminal 12v of the voltage detection circuit 12e are connected to the capacitance measurement control unit 17. The transistor 12s is turned on by the drive signal from the capacitance measurement control unit 17, and the capacitance measurement unit 12 is operated. The capacitance measurement control unit 17 processes the output signal from the output terminal 12v of the voltage detection circuit 12e to measure the total capacitance. That is, the capacitance measurement part 12 and the capacitance measurement control part 17 correspond to "capacitance measurement means."

Since the processing site | part of the electrode E and the to-be-processed object W opposes through the clearance gap, the capacitor | condenser 12f is comprised through the clearance gap between them and the process liquid in the clearance gap. In the capacitance measuring unit 12, a direct current (i) is periodically applied from the pulse output circuit 12b to a machining portion (a portion opposite to the electrode side surface and the electrode forward end surface) of the electrode E and the workpiece W. Supply voltage to detect the voltage V of the electrode E by the voltage detection circuit 12e, and the average voltage Vm calculated from the voltage V in the capacitance measurement control unit 17 and the direct current ( The total capacitance is calculated based on i) and the time to supply the direct current i to the capacitor 12f.

As shown in Fig. 4, when the pulse is output from the pulse output circuit 12b, the transistor 12c is turned on, the point P is grounded, and the voltage detected by the voltage detection circuit 12e is zero. Then, it discharges from the capacitor | condenser 12f. When the transistor 12c is turned off, the capacitor 12f is charged while it is off (to), and the voltage V detected by the voltage detection circuit 12e linearly increases. The capacitance measurement control unit 17 receives the voltage signal of the detection voltage V supplied from the output terminal 12v, performs A / D conversion, and calculates the average voltage Vm. When the total capacitance C and the electric quantity Q of the capacitor 12f are Q = i × 2to, the total capacitance C can be obtained by the formula C = Q / Vm = i × 2to / Vm. There is a number.

In addition, the capacitance measuring part 12 is not limited to the above-mentioned structure, If the total capacitance C between at least the electrode E and the workpiece | work part of the to-be-processed object W can be measured, various structures are taken into consideration. It can be adopted.

The discharge control unit 13 feeds power from the power supply circuit 10 and applies discharge pulses set by the processing condition setting unit 19 described later to the electrode E and the workpiece W. FIG. The processing current measuring unit 14 measures the current supplied to the discharge pulse through the ammeter 14a and supplies the detected current to the calculation processing unit 9. In this way, when the discharge pulse is applied, when the gap between the electrode advance end surface and the processing surface of the workpiece W reaches a predetermined distance that can be discharged, the discharge is started to start processing.

The arithmetic mode changeover switch 15 sets a machining area calculation mode in which the arithmetic processing unit 9 sets machining conditions based on the machining area of the machining surface, and sets machining conditions based on the interelectrode capacitance before the discharge machining starts. The capacitance calculation mode is configured to be selected and set alternatively. On the other hand, the calculation mode switching switch 15 may be omitted, and the machining area of the machining surface may be initially calculated, and the inter-electrode capacitance may be automatically calculated when the machining area is difficult to calculate.

The calculation processing unit 9 includes a position control unit 16 (moving distance detecting means) for controlling the Z-axis moving mechanism 4, a capacitance measurement control unit 17, a calculating means 18, and a processing condition setting unit ( 19; processing condition setting means), X, Y control unit 20 and the like.

The position control part 16 is formed so that the inter-pole distance from the forward end surface of the electrode E to a process surface can be changed by moving the head 3 to an up-down direction by the Z-axis moving mechanism 4. The position control part 16 is formed so that the inter-pole distance from the forward end surface of the electrode E to a process surface can be detected.

In addition to the above-described processing, the capacitance measurement control unit 17 receives a signal of a measurement period for measuring the total capacitance by the capacitance measurement unit 12 from the measurement cycle operation unit 24 described later, and the measurement cycle The transistor 12s is turned on every time to control the operation timing of the capacitance measuring unit 12. The discharge machining apparatus M uses the machining program for each workpiece, similarly to a general discharge machining apparatus, and the Z-axis moving mechanism 4 is operated by the position controller 16 while interpreting the machining program as a numerical control program. Is controlled numerically, and the X, Y, and Z axes are moved by the X and Y controllers 20 to numerically control the X and Y axis moving mechanisms 5 and 6, respectively. It is comprised so that an electric discharge machining may be carried out while controlling a position in a direction. Since such a configuration is not directly related to the present invention, detailed description thereof will be omitted. As described above, the X and Y control units 20 drive control the X-axis moving mechanism 5 and the Y-axis moving mechanism 6, respectively.

The calculating means 18 is provided with the processing area calculating part 21 which calculates a processing area in a processing area calculation mode, and the capacitance calculating part 22 which calculates inter-pole capacitance in the capacitance calculation mode. As shown in Fig. 5, the machining area calculating part 21 moves the electrode E to a plurality of different positions in the vertical direction by the Z-axis moving mechanism 4 during electric discharge machining (middle point of the electric discharge machining). In the first and second moving positions d1 and d2 (distances from the surface of the workpiece W from the surface of the workpiece W), which are a plurality of different positions in the vertical direction detected by the position controller 16, and moved. 2 corresponding to the first and second inter-pole distances h1 and h2 measured by the first and second inter-pole distances h1 and h2 and the capacitance measuring unit 12 and the capacitance measuring control unit 17. It is formed to calculate the processing area S of the processing surface Wf of the to-be-processed object W using the 1st, 2nd total capacitance C1 and C2 of a position. On the other hand, as the electrode E, for example, a columnar electrode having a substantially horizontal forward end surface Ef will be described as an example, but the electrode E does not necessarily have to be a columnar shape, Therefore, the electrode may be such that the processing area is changed continuously or discontinuously.

Specifically, the electrode E is brought into contact with the processing surface Wf of the workpiece W to initialize the inter-pole distance to zero. Next, as shown in Fig. 5A, the Z-axis moving mechanism 4 is drive controlled to move the electrode E to the first moving position d1. At this time, the first total capacitance C1, the interpolar capacitance Cp1 between the electrode forward end surface Ef and the working surface Wf, the processing area S of the working surface Wf, the first interpolar distance h1, and the side surface of the electrode E When the capacitance Ca between (Es) and the workpiece W is set as the dielectric constant? Of the processing liquid, the first total capacitance C1 can be expressed by the following equation (1), and is detected by measurement.

C1 = Cp1 + Ca... (One)

However, Cp1 = epsilon S / h1.

Next, as shown in FIG. 5B, the drive control of the Z-axis moving mechanism 4 is performed to move the electrode E to the second moving position d2. At this time, when the second total capacitance C2, the interelectrode capacitance Cp2 of the electrode forward end surface Ef and the working surface Wf, and the second inter-pole distance h2 from the electrode forward end surface Ef to the processing surface Wf are defined, 2 total capacitance C2 can be represented by following formula (2), and it is detected by a measurement.

C2 = Cp2 + Ca? D2 / d1... (2)

However, Cp2 = εS / h2.

When said Formula (1) and Formula (2) are calculated | required with respect to the processing area S, the processing area S can be represented by following Formula (3).

S = (h1? H2 (C2? D1-C1? D2)) / (? (D1? H1-d2? H2))... (3)

In addition, the distance d1, d2 from the surface of the workpiece W to the electrode advance cross section has already been recognized by the position control unit 16 from the surface of the workpiece W to the workpiece surface Wf. Therefore, it can calculate using the 1st, 2nd inter-pole distances h1, h2, and permittivity (epsilon).

An example of the technique of detecting the dielectric constant [epsilon] of the processing liquid will be described.

The dielectric constant epsilon of the processing liquid is obtained using the standard electrode Ea in which the processing area is already recognized. As shown in FIG. 6A, the distance between the electrodes Ea is initialized to zero by bringing the standard electrode Ea into contact with the surface of the workpiece W. FIG. Then, as shown in Fig. 6B, the standard electrode Ea is moved from the surface of the workpiece W to a position of distance h0, and the total capacitance C0 at this position is electrostatic Measurement is performed by the capacitance measuring unit 12 and the capacitance measuring control unit 17. If the area facing the workpiece W of the standard electrode Ea is S0, the dielectric constant? Can be expressed by the following equation (4).

[epsilon] = h0? C0 / S0? (4)

By the above, with respect to said Formula (3), the electrode advance cross section (1) from the surface of the 1st, 2nd total capacitance C1, C2, the 1st, 2nd interpolar distance h1, h2, and the to-be-processed object W The machining area S of the machining surface Wf of the workpiece W is calculated by substituting the distances d1 and d2 and the dielectric constant epsilon to Ef.

Further, by calculating the first and second inter-pole capacitances Cp1 and Cp2 using the calculated value of the machining area S, it is possible to detect the presence or absence of machining residues from the tendency of increase and decrease of the inter-electrode capacitance. That is, when the drive of the Z-axis moving mechanism 4 is performed by a ball screw mechanism, a linear motor, or the like which does not cause backlash, theoretically Cp1 = 2Cp2 when h1 = h2 / 2. For this reason, when the 2nd inter-pole capacitance Cp2 is smaller than the value of 1/2 of the 1st inter-pole capacitance Cp1, it can be detected that the process waste is deposited on the process surface of the to-be-processed object W. As the second inter-pole capacitance Cp2 is smaller than 1 / 2Cp1, it is possible to detect that the deposition amount of the processing waste on the processing surface of the workpiece W is large.

Next, in the capacitance calculation mode, such as when the forward end surface of the electrode E is inclined with respect to the horizontal plane, the inter-pole capacitance between the forward end surface Ef and the processing surface Wf of the electrode E is calculated. An example will be described based on FIG. 7. The electrostatic capacitance calculating section 22 moves the electrodes E to a plurality of different positions in the vertical direction by the Z-axis moving mechanism 4 during discharge machining, and the plurality of positions detected by the position control unit 16. For example, the first and second inter-pole distances h21 and h22 at the first and second moving positions d21 and d22, the capacitance measuring unit 12 and the capacitance measuring control unit 17 are measured. The forward end face Ef of the electrode EA and the workpiece by using the first and second total capacitances C21 and C22 at two positions corresponding to the first and second interpolar distances h21 and h22. It is comprised so that the inter-pole capacitance of the process surface Wf of (W) may be calculated.

The electrode EA is, for example, a columnar shape having an angle (θ; 0 ° <θ <90 °) between the electrode forward end surface Ef and the electrode axis center, and from the surface of the workpiece W to the processing surface. The distances d21 and d22 are already recognized by the position control unit 16.

First, the electrode EA is brought into contact with the working surface of the workpiece W to initialize the distance between the poles to zero. Subsequently, as shown in FIG. 7A, the drive control of the Z-axis moving mechanism 4 is performed to move the electrode EA to the first moving position d21. At this time, the first total capacitance C21, the electrode forward end surface and the interelectrode capacitance Cp21 of the working surface, the processing area SA, the first inter-pole distance h21 from the forward end surface of the electrode EA to the processing surface, and the side surface of the electrode EA; When the capacitance Ca of the workpiece W, the dielectric constant ε of the processing liquid, and the angle θ of the electrode advance cross section with respect to the vertical plane, the first total capacitance C21 can be expressed as shown in the above formula (1). It is detected by Then, when the inter-pole capacitance Cp21 shown in the following formula (5) is substituted into the formula (1), the first total capacitance C21 can be represented by the following formula (6).

Cp21 =? SA / (h21? Sin?)... (5)

C21 =? SA / (h21? Sin?) + Ca... (6)

Next, as shown in FIG. 7B, the head 3 is driven to move upward by the Z-axis moving mechanism 4, and the electrode EA is moved to the second moving position d22. . At this time, when the second total capacitance C22, the interelectrode capacitance Cp22 of the electrode forward end face and the working surface, the second interpolar distance h22, the first and second moving positions d21 and d22, the second total capacitance C22 is It can be represented as equation (2). Subsequently, when the interelectrode capacitance Cp22 represented by the following equation (7) is substituted into the equation (2), the second total capacitance C22 can be expressed by the following equation (8), and is detected by measurement. do.

Cp22 = εSA / (h22? Sin?)... (7)

C22 =? SA / (h22? Sin?) + Ca? D22 / d21... (8)

When said Formula (6) and Formula (8) are solved with respect to the process area SA of the process surface of the to-be-processed object W, the process area SA can be represented by following formula (9).

SA = (h21? H22 (C22? D21? C21? D22)) × sin? / (? (D21? H21 -d22? H22))... (9)

Here, by substituting said Formula (9) into said Formula (5), the interelectrode capacitance Cp21 in the 1st moving position d21 can be represented by following Formula (10).

Cp21 = h22 (C22? D21-C21? D22) / (d21? H21-d22? H22)... (10)

By substituting said Formula (9) into said Formula (7), the interelectrode capacitance Cp22 in the 2nd moving position d22 can be represented by following Formula (11).

Cp22 = h21 (C22? D21-C21? D22) / (d21? H21-d22? H22)... (11)

As described above, the first and second total capacitances C21 and C22, the first and second inter-pole distances h21 and h22, and the workpiece W may be applied to the equation (10) or (11). EA) The electrode EA having a complicated forward end face having an angle θ between the electrode forward end face and the axis center of the electrode EA by substituting the distances d21 and d22 to the tip and the permittivity ε. In this case, the first and second inter-pole capacitances Cp21 and Cp22 can be calculated by not including θ. Since the interelectrode capacitances Cp21 and Cp22 are physical quantities proportional to the machining area SA, for example, the interelectrode distance h21 is set to a target interelectrode distance, and the machining conditions are based on the interelectrode capacitance Cp22. The setting unit 19 sets discharge processing conditions as described later. In addition, in the same manner as described above, the inter-state state such as the occurrence state of the processing residue can be detected from the increase or decrease of at least one of the first and second inter-electrode capacitances Cp21 and Cp22. On the other hand, although the electrode EA shown in FIG. 7 was demonstrated using the columnar electrode as an example, the electrode does not necessarily need to be columnar, but the electrode whose process area changes continuously or discontinuously with progress of electric discharge machining. It may be. Further, the electrode may have a plurality of inclined surfaces having the same inclination angle or the same inclination angle as the forward end face of the electrode.

The processing condition setting unit 19 includes a discharge pulse setting unit 23, a measurement cycle calculating unit 24, and a jump operation calculating 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. On the other hand, Table 1 and Table 2 show processing conditions in the case where the dielectric constant ε = 15.9372 × 10 ^-12 F / m of the electrode made of copper, the steel workpiece, and the processing liquid, It is an interelectrode capacitance when it is 5 micrometers.

[Table 1]

[Table 2]

When the machining area setting 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, thereby providing a peak current of the discharge pulse. Then, the ON time and the OFF time of the discharge pulse are set. The peak current is set to a value substantially proportional to the processing area S. This current density is 5 A / cm 2 or less and is set to about 5 A / cm 2. On the other hand, the voltage of the discharge pulse is appropriately set by the discharge control unit 13. Then, the data on the discharge processing conditions set as described above is supplied to the discharge control unit 13, and discharge processing is performed based on the discharge pulses.

When the capacitance calculation mode is set, the machining condition setting unit 19 is one of the first and second inter-pole capacitances Cp21 and Cp22 obtained by the calculation in the machining condition table shown in Table 2 as described above. Preferably, by applying the first inter-pole capacitance Cp21, the peak current of the discharge pulse, the ON time and the OFF time of the discharge pulse are set. The peak current is set to a value almost proportional to the interelectrode capacitance. The current density is set to about 25 A / nF as a value of 25 A / nF or less. Then, the data on the discharge processing conditions set as described above is supplied to the discharge control unit 13, and discharge processing is performed based on the discharge pulses.

The processing conditions tables shown in Tables 1 and 2 are merely examples, and can be appropriately changed according to the permittivity of the processing liquid, the combination of the material of the electrode and the workpiece, or the processing conditions.

The measurement cycle calculator 24 includes a map in which the capacitance measurement unit 12 and the capacitance measurement control unit 17 measure the total capacitance and change the processing conditions in advance. In the map, a measurement period is set by using the machining area (S, SA (or inter-electrode capacitance between the electrode forward end face and the machining surface) as a parameter). Since the processing speed of the electrode is larger as the processing areas S and SA are smaller, the map is set so as to increase the measurement period as the processing area S and SA (or the inter-electrode capacitance) increases.

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 EA based on the error distance α between the poles. On the other hand, the jumping operation of the electrode refers to an operation of vertically moving the electrode in order to flow the processing residue deposited on the processing surface and to discharge it out of the gap. The relationship between the error distance α as the height of the work residue deposited on the work surface of the workpiece W, the jump period, and the jump movement amount is previously set in the form of a map or a table as shown in FIGS. 8 and 9. Stored in memory.

However, the calculation technique of the error distance α of the distance between the poles will be described in Examples 3 and 4, and as shown in FIG. 5 and FIG. In the case of not calculating, an error distance (for example, 4 µm) of a default value may be applied.

The map of FIG. 8 is set so that a jump period may become smaller, so that the error distance (alpha) increases, and the map of FIG. 9 is set so that a jump movement amount may increase, so that the error distance (alpha) increases. 8 and 9 are only examples, and can be appropriately changed according to the processing shape, processing conditions, and the like.

Next, the discharge machining condition setting processing performed by the machining condition setting unit 19 will be described based on the flowchart of FIG. On the other hand, Si (i = 1,2 ...) represents each step. The discharge machining condition setting process is a process executed in the machining area calculation mode with respect to the example shown in FIG. 5. First, when the electric discharge machining apparatus M is started, various signals, such as the dielectric constant (epsilon) of a process liquid and the kind of the selected calculation mode, are read (S1). In S2, it is determined whether the start switch of the discharge machining process is operated ON. As a result of the determination in S2, when the electric discharge machining process is started, the process proceeds to S3 to determine whether or not the dielectric constant data of the processing liquid is held. As a result of the determination in S2, when the 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 flow advances to S4 to measure the distance between the poles and the total capacitance. As a result of the determination in S3, when the dielectric constant data is not retained, the process proceeds to S5. After detecting the dielectric constant epsilon of the processing liquid as described above using the standard electrode, the process proceeds to S4.

In S4, the electrode advance cross section is sequentially driven to the 1st, 2nd movement position by the position control part 16 and the Z-axis movement mechanism 4, and the 1st, 2nd pole distance h1 in each movement position is carried out. , h2) and the distances d1 and d2 from the surface of the workpiece W to the processing surface are measured. In addition, the capacitance measuring unit 12 and the capacitance measuring control unit 17 measure the first and second total capacitances C1 and C2 at the first and second moving positions.

Next, in S6, it is determined whether or not the machining area calculation mode is selected.

As a result of the determination in S6, when the machining area calculation mode is selected, the machining area calculation processing is performed in S7. The machining area calculating unit 21 substitutes the first and second total capacitances C1 and C2, the first and second inter-pole distances h1 and h2 and the distances d1 and d2 into Equation (3). Calculate the machining area (S). After calculating the machining area, the process proceeds to S9.

In S9, the machining conditions are set using the machining condition table shown in Table 1 based on the calculated machining area. The processing conditions set here include electrical conditions of electric discharge machining such as peak current value, jump period of the electrode E, the amount of jump movement, and the like. After setting the processing conditions, the process proceeds to S10 to start the discharge machining process. On the other hand, the measurement period for measuring the total capacitance is calculated by the capacitance measurement control unit 17.

After the start of the discharge machining process, it is determined whether or not it is the measurement cycle timing (S11). As a result of the determination in S11, in the case of the measurement cycle timing, the flow advances to S4, and measurement of the distance between the poles and the total capacitance is performed while the discharge machining process is stopped. As a result of the determination in S11, when it is not the measurement cycle timing, the flow advances to S12 to determine the end of the discharge machining process. As a result of the determination in S12, when the discharge machining process is finished, the control ends. When the discharge machining process is not finished, the process proceeds to S10 and the discharge machining process is continued.

On the other hand, with respect to the example shown in Fig. 7, the discharge processing condition setting processing performed in the capacitance calculation mode is almost the same as above.

As a result of the determination in S6, when the capacitance calculation mode is selected, the flow advances to S8 to perform the capacitance calculation process. The capacitance calculating unit 22 has the first and second total capacitances C1 and C2, the first and second inter-pole distances h1 and h2 and the distance d1, relative to equation (10) or equation (11). By substituting d2), it calculates about at least one of 1st, 2nd intercapacitance capacitance Cp1, Cp2. On the other hand, the first inter-pole distance h1 is the target inter-pole distance.

After calculation of the interelectrode capacitance, the process proceeds to S9, and the machining conditions are set using the machining condition table shown in Table 2 based on the calculated interelectrode capacitance. After setting the processing conditions, the process proceeds to S10 to start the discharge machining process.

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

Since the processing area is calculated using the measured first and second inter-pole distances h1 and h2 and the first and second total capacitances C1 and C2 between the measured electrode and the workpiece of the workpiece, The machining area S of the machining surface of the workpiece W can be obtained with good accuracy. In addition, even when the electrode advance cross section has a complicated shape and it is difficult to calculate the machining area SA, the first interelectrode capacitance Cp21 or the second interelectrode capacitance Cp22, which is almost proportional to the machining area SA, may be used. As described above, it can be obtained with good precision.

For this reason, the electric discharge machining conditions can be appropriately set based on the processing area S (or SA) or the highly accurate calculation value of the first and second interelectrode capacitances Cp1 and Cp2 (or Cp21 and Cp22). . Furthermore, since the first and second interpolar distances h1 and h2 (or h21 and h22) between the electrode forward end face and the working surface are used for the calculation, the first and second interpolar capacitances Cp1 and Cp2 (or With respect to the values of Cp21 and Cp22)), the height of the processing residue deposited on the processing surface can be reflected as the error distance, so that an appropriate processing condition can be set.

Furthermore, since the first and second total capacitances C1 and C2 (or Cp21 and Cp22) actually measured and the first and second inter-pole distances h1 and h2 (or h21 and h22) are used, abrupt machining Even if an increase in the area S (or SA) occurs, the machining area S (or SA) or the first and second inter-pole capacitances Cp1 and Cp2 (or Cp21 and Cp22) can be calculated with good accuracy. It is possible to perform processing without dividing the electrode and without causing processing failure, thereby reducing the number of discharge machining.

And a machining condition setting unit 19 for setting machining conditions for electric discharge machining based on the first and second interpolar capacitances Cp21 and Cp22 instead of the calculated machining areas S and SA or SA. Therefore, it is possible to appropriately set an appropriate measurement cycle, electrical conditions for electric discharge machining, jump cycle of jump operation, jump movement amount, etc. according to the interphase state based on the size of the machining area and the interelectrostatic capacitance of the machining surface.

Since the machining area calculating unit 21 calculates the machining area S based on Equation (3), the control load for the calculation can be reduced, and the calculation processing speed of the machining area can be increased.

Since the capacitance calculation unit 22 calculates the inter-pole capacitances Cp21 and Cp22 based on the formulas (9) to (11), even if the electrode forward cross-section is a complicated shape, the inter-pole proportional to the processing area SA is obtained. The capacitances Cp21 and Cp22 can be calculated accurately.

Since the machining condition setting unit 19 changes the measurement period based on the machining area S, SA (or the first and second interelectrode capacitances Cp21 and Cp22 instead of the machining area SA), the electrode The electrical conditions can be changed and set in a measurement cycle suitable for the shape change of the forward cross-section, and the appropriate machining conditions can be set.The machining condition setting unit 19 is made of a workpiece instead of the machining area S or SA or SA. Since the processing current value supplied to the electrodes E and EA is controlled to be substantially proportional to the first and second interelectrode capacitances Cp21 and Cp22, the abnormal consumption of the electrodes E and EA due to the excessive supply of current is eliminated. In addition, since the supply current to the electrodes E and EA is set to be equal to or less than a predetermined current density, generation of defects such as a decrease in processing speed can be prevented.

(Example 2)

Next, Example 2 will be described based on FIG. 11.

The difference from the first embodiment is that in the first embodiment, the distance D from the surface of the workpiece W to the processed surface is already recognized. In the second embodiment, the distance D is not known. .

The column-shaped electrode EB is brought into contact with the working surface of the workpiece W to initialize the movement position (interval distance) of the electrode EB. Subsequently, as shown in Fig. 11A, the electrode EB is driven to move upward by the Z-axis moving mechanism 4 to move the electrode EB to the first moving position. At this time, the first total capacitance C31, the interelectrode capacitance Cp31 of the electrode forward end face and the working surface, the processing area SB, the first interpolar distance h31 from the electrode forward end surface to the working surface, the side surface of the electrode EB and the workpiece W When the capacitance Ca of), the dielectric constant ε of the processing liquid, and the distance D from the surface of the workpiece W to the processing surface, the first total capacitance C31 can be expressed by the following equation (12), It is detected by measurement.

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

However, inter-pole capacitance Cp31 = εSB / h31.

Subsequently, as shown in FIG. 11B, the electrode EB is further driven to move upward from the first moving position by the Z-axis moving mechanism 4, thereby moving the electrode EB to the second moving position. Move to At this time, when the second total capacitance C32, the electrode forward end face and the interelectrode capacitance Cp32 of the working surface, and the second inter-pole distance h32 from the electrode forward end surface to the working surface, the second total capacitance C32 is expressed by the following equation ( 13) and can be detected by measurement.

C32 = Cp32 + Ca (D−h32) / D... (13)

However, the interelectrode capacitance Cp32 = εSB / h32.

Then, as shown in Fig. 11C, the Z-axis moving mechanism 4 moves the electrode EB further upwardly from the second moving position to drive the electrode EB to the third moving position. Move it. At this time, when the third total capacitance C33, the electrode forward end face and the interelectrode capacitance Cp33 of the working surface, and the third interpole distance h33 from the electrode forward end surface to the working surface, the third total capacitance C33 is expressed by the following equation ( 14) and can be detected by measurement.

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

However, the interelectrode capacitance Cp33 = εSB / h33.

When said Formula (12)-Formula (14) is solved with respect to the processing area SB, the processing area SB can be represented by following Formula (15).

SB = h31? H32? H33 (h31 (C32-C33) + h32 (C33-C31) + h33 (C31-C32)) / (? (H31-h32) (h32-h33) (h33-h31)) (15)

The machining area calculating unit 21 calculates the inter-pole capacitances Cp31, Cp32 and Cp33 and the distance D from the surface of the workpiece W to the machining surface based on the calculated machining area SB. .

The discharge pulse setting unit 23 calculates the current density using the machining current value detected by the machining current measuring unit 14 and the machining area SB, and controls the current density to be equal to or less than a predetermined current density. Doing. The machining condition setting unit 19 sets electrical machining conditions such as discharge pulses by applying the machining area SB to the machining condition table in Table 1, similarly to the first embodiment.

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

Basically, the same effects and effects as in Example 1 are obtained. Furthermore, even when the distance D from the surface of the workpiece W to the machining surface is unclear, the inter-pole distances h31 to h33 and the total capacitances C31 to C33 of the first to third moving positions are detected. It is possible to set appropriate processing conditions by

On the other hand, although the electrode EB shown in FIG. 11 was explained using the columnar electrode as an example, the electrode EB does not necessarily need to be a columnar shape, and a process area changes continuously or discontinuously with progress of electric discharge machining. The electrode may be used.

(Example 3)

Next, Example 3 will be described based on FIG. 12.

The difference from the first embodiment is that in the first embodiment, the distance D from the surface of the workpiece W to the processed surface is already recognized. In the third embodiment, the distance D is not known. Also, the error distance α is included in the measured inter-pole distance. On the other hand, the error distance α is due to the processing waste deposited on the processing surface of the workpiece W, the backlash of the gear system of the Z-axis moving mechanism 4, and the like. As a value, the accumulation amount of the processing waste on a processing surface is shown, and when backlash generate | occur | produces, the sum total of the accumulation amount of the processing waste as a positive value and the amount of backlash as a negative value is shown.

The column-shaped electrode EC is brought into contact with the working surface of the workpiece W to initialize the moving position (interval distance) of the electrode EC. Then, as shown in Fig. 12A, the electrode EC is driven to move upward by the Z-axis moving mechanism 4 to move the electrode EC to the first moving position. At this time, the first total capacitance C41, the interelectrode capacitance Cp41 between the electrode forward end face and the working surface, the processing area SC, the first interpole distance h41 from the electrode forward end surface to the working surface, the side surface of the electrode EC and the workpiece W ), The dielectric constant ε of the processing liquid, the distance D from the surface of the workpiece W to the processing surface, and the error distance α, the first total capacitance C41 is expressed by the following equation (16). Can be displayed and detected by measurement.

C41 = Cp41 + Ca (D-h41-α) / D... (16)

However, the interelectrode capacitance Cp41 = epsilon SC / (h41 + α).

Next, as shown in Fig. 12B, the Z-axis moving mechanism 4 moves the electrode EC further upward from the first moving position to move the electrode EC to the second moving position. Let's do it. At this time, assuming that the second total capacitance C42, the interelectrode capacitance Cp42 of the electrode forward end face and the working surface, and the second interpolar distance h42 from the electrode forward end face to the working surface, the second total capacitance C42 is expressed by the following equation ( 17) and can be detected by measurement.

C42 = Cp42 + Ca (D−h42−α) / D... (17)

However, the interelectrode capacitance Cp42 = epsilon SC / (h42 + α).

Then, as shown in Fig. 12C, the Z-axis moving mechanism 4 moves the electrode EC further upwards from the second moving position to move the electrode EC to the third moving position. Move it. At this time, when the third total capacitance C43, the electrode forward end face and the interelectrode capacitance Cp43 of the working surface, and the third interpole distance h43 from the electrode forward end surface to the working surface, the third total capacitance C43 is expressed by the following equation ( 18) and can be detected by measurement.

C43 = Cp43 + Ca (D−h43−α) / D... (18)

However, the interelectrode capacitance Cp43 = εSC / (h43 + α).

Then, as shown in Fig. 12D, the Z-axis moving mechanism 4 moves the electrode EC further upwards from the third moving position to move the electrode E to the fourth moving position. Move it. At this time, assuming that the fourth total capacitance C44, the interelectrode capacitance Cp44 of the electrode forward end face and the working surface, and the fourth interpolar distance h44 from the electrode forward end face to the working surface, the fourth total capacitance C44 is expressed by the following equation ( 19) and can be detected by measurement.

C44 = Cp44 + Ca (D-h44-α) / D... (19)

However, the interelectrode capacitance Cp44 = εS / (h44 + α).

When said Formula (16)-Formula (19) is solved with respect to the processing area SC, the processing area SC can be represented by following Formula (20) containing an error distance (alpha).

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

When the error distance α is found, it can be expressed by the following equation (21).

α = A / B. (21)

Where 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 Fig. 8 and Fig. 9, the jump operation calculation unit 25 sets the jump period of the electrode EC shorter as the error distance α is larger, and while the error distance α is larger as a result of the jump. The amount of movement is set large. Further, by measuring the position error of the electrode EC due to the backlash of the gear system in advance, the error distance α is corrected by this amount of backlash, and the amount of deposition of the processing residue deposited on the processing surface can be calculated with good accuracy. There is a number.

Next, the operation and effect of the discharge machining apparatus M according to the third embodiment will be described.

Basically, the same effects and effects as in Example 1 are obtained. Further, even when the distance D from the surface of the workpiece W to the machining surface is unclear, the distance between the poles h41 to h44 and the total capacitances C41 to C44 of the first to fourth moving positions are detected. By this, the machining area SC can be calculated with good accuracy and the appropriate machining conditions can be set. Further, by calculating the error distance α, the processing area SC can be calculated with good accuracy in consideration of processing waste, backlash, and the like, and the processing conditions can be set appropriately.

In addition, although the electrode EC shown in FIG. 12 was demonstrated using the columnar electrode as an example, the electrode does not necessarily need to be a columnar shape, and may be an electrode whose process area changes continuously or discontinuously with progress of electric discharge machining. Do.

(Example 4)

Next, Example 4 will be described with reference to FIG.

The difference from Example 1 is that in Example 1, the distance D from the surface of the workpiece W to the machining surface has already been recognized. In Example 4, the distance D is not known. The error distance α is included in the measured inter-pole distance and the electrode forward cross section is a complicated shape.

Moving position of the electrode ED by bringing the column-shaped electrode ED having an angle θ between the electrode forward end surface and the electrode axis center (vertical surface) into contact with the machining surface of the workpiece W; Initialize (Interval distance). Then, as shown in Fig. 13A, the electrode ED is moved upward by the Z-axis moving mechanism 4 to move the electrode ED to the first moving position. At this time, the first total capacitance C51, the interelectrode capacitance Cp51 of the electrode forward end face and the working surface, the processing area SD, the first interpolar distance h51 from the electrode forward end surface to the working surface, the side surface of the electrode ED and the workpiece W ), The dielectric constant ε of the processing 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 forward end face and the electrode, the first total capacitance (C51). ) Can be represented by the following equation (22) and is detected by measurement.

C51 = epsilon SD / ((h51 + α) sinθ) + Ca (D-h51-α) / D. (22)

However, the interelectrode capacitance Cp51 = epsilon SD / ((h51 + α) sinθ).

Next, as shown in FIG. 13B, the electrode ED is moved upward from the first moving position by the Z-axis moving mechanism 4 to move the electrode ED to the second moving position. Let's do it. At this time, assuming that the second total capacitance C52, the interelectrode capacitance Cp52 of the electrode forward end face and the working surface, and the second interpolar distance h52 from the electrode forward end face to the working surface, the second total capacitance C52 is expressed by the following equation ( 23) and can be detected by measurement.

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

However, the interelectrode capacitance Cp52 = εSD / ((h52 + α) sinθ).

Then, as shown in Fig. 13C, the Z-axis moving mechanism 4 moves the electrode ED further upwards from the second moving position to move the electrode ED to the third moving position. Move it. At this time, when the third total capacitance C53, the electrode forward end face and the interelectrode capacitance Cp53 of the working surface, and the third interpole distance h53 from the electrode forward end surface to the working surface, the third total capacitance C53 is expressed by the following equation ( 24) and can be detected by measurement.

C53 = epsilon SD / ((h53 + α) sinθ) + Ca (D-h53-α) / D... (24)

However, the interelectrode capacitance Cp53 = εSD / ((h53 + α) sinθ).

Subsequently, as shown in Fig. 13D, the Z-axis moving mechanism 4 moves the electrode ED further upwardly from the third moving position to move the electrode ED to the fourth moving position. Move it. At this time, assuming that the fourth total capacitance C54, the interelectrode capacitance Cp54 of the electrode forward end face and the working surface, and the fourth interpolar distance h54 from the electrode forward end face to the working surface, the fourth total capacitance C54 is 25) and can be detected by measurement.

C54 = epsilon SD / ((h54 + α) sinθ) + Ca (D-h54-α) / D... (25)

However, the interelectrode capacitance Cp54 = εSD / ((h54 + α) sinθ).

When the above formulas (22) to (25) are solved with respect to the machining area SD, the machining area SD can be expressed by the following 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) x (h52-h53) x (h53-h51)). (26)

Similarly, equations (22) to (25) can be solved for the error distance α to obtain the error distance α.

Here, by substituting the formula (26) into the formula of the inter-pole capacitance Cp51, the inter-pole capacitance Cp51 at the first moving position d51 can be represented 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 inter-pole capacitances Cp52 to Cp54 can be calculated based on the processing area SD.

As described above, even in the case of the electrode ED having a complicated forward cross section such as having an angle θ between the electrode forward end face and the axis center of the electrode ED, the interelectrode capacitance is not included in the above manner. (Cp51 to Cp54) can be calculated. Further, by calculating the error distance α, it is possible to set processing conditions in consideration of processing waste, backlash, and the like. On the other hand, as the electrode ED of FIG. 13, the pillar-shaped electrode has been described as an example. However, the electrode does not necessarily have to be a columnar shape, and may be an electrode in which the processing area is changed continuously or discontinuously with the progress of electric discharge machining. Do. Further, the electrode may have a plurality of inclined surfaces having the same inclination angle or the same inclination angle as the forward end face of the electrode.

Next, the modified example which changed the said embodiment partially is demonstrated.

1] In the above embodiment, an example in which the processing is performed by moving the electrode in the up and down direction has been described, but the present invention is also applicable to an electric discharge machining apparatus in which the processing is performed by moving the electrode horizontally in the left and right directions or in the front and rear directions. Do.

2] In the above embodiment, an example in which the transfer mechanism of the electrodes in the X, Y, and Z axis directions is constituted by a ball screw mechanism and a motor, has been described. It is also possible to configure the transfer mechanism by a linear motor or the like.

3] In the above embodiment, an example of controlling the peak current value, the pulse on time (pulse width) and the pulse off time so that the machining condition setting unit is equal to or less than a predetermined reference current density has been described. By setting the pulse on time to a constant width (time), it is also possible to control the pulse off time to a reference current density or less.

4] In the above embodiment, since the electrode is copper and the workpiece is a combination of steel, an example in which the reference current densities are 5 A / cm 2 and 25 A / nF has been described, but the combination of the electrode and the workpiece is For other materials, separate processing condition table should be set. Further, a plurality of types of processing condition tables may be prepared in advance for the combination of the electrode material and the workpiece material, and the processing condition table corresponding to the combination of the electrode and the workpiece may be selected.

5] In the above embodiment, an example of measuring the distance between the poles and the total capacitance of the first to fourth moving positions has been described. It is also possible to measure the distance between the poles and the total capacitance at the moving position.

6] In the above embodiment, an example in which an operation mode switch for switching between the machining area calculation mode and the capacitance calculation mode has been described has been described. However, the configuration may be used to calculate both the machining area and the capacitance between the poles. In addition, it is good also as a structure which selects either one automatically based on a machining program.

7] In the above embodiment, an example in which calculation cycles such as the total capacitance measurement and the machining area, etc. are set based on the machining area as a calculation result, etc. has been described. It is also possible to carry out.

8] Others skilled in the art can implement the above-described embodiments in the form of various modifications without departing from the spirit of the present invention, and the present invention includes such modifications.

The present invention provides a discharge processing apparatus for discharging a workpiece by discharging it between an electrode and a workpiece, wherein the discharge area of the discharge machining surface or the interelectrode capacitance between the electrode forward end face and the workpiece surface is good during discharge machining. By calculating with accuracy and setting the appropriate processing conditions according to the interphase conditions, such as the change of the processing area and the generation of processing debris, the productivity and processing quality of electric discharge machining are improved.

M: discharge processing equipment
W: Workpiece
E ~ ED: Electrode
1: machine body
2: controller
4: Z axis moving mechanism
9: arithmetic processing unit
12: capacitance measuring unit
13: discharge control unit
16: position control
17: capacitance measurement control unit
18: calculation means
19: machining condition setting part
21: machining area calculation unit
22: capacitance calculation unit
23: discharge pulse setting unit
24: measuring cycle calculator
25: jump operation calculation unit

Claims (10)

A discharge processing apparatus for supplying a processing liquid to a gap between an electrode and a workpiece, and discharging the workpiece by applying discharge pulses from the electrode to the workpiece.
Moving means capable of moving the electrode and changing an inter-pole distance from the processing forward direction end surface of the electrode to the processing surface of the workpiece;
Moving distance detecting means for detecting a moving distance of the electrode;
A capacitance measuring means capable of measuring a total capacitance between the electrode and the processed portion of the workpiece to be opposed to each other with the gap therebetween;
At each measurement cycle timing after the start of discharge processing, the electrodes are moved to a plurality of positions by the moving means, and the plurality of inter-pole distances and the capacitance measured by the moving distance detecting means are measured. Calculating means for calculating inter-pole capacitance proportional to the machining area of the machined surface or the machined area, using a plurality of total capacitances measured by the means;
Machining condition setting means for setting machining conditions relating to discharge machining pulses based on the machining area or the interelectrode capacitance calculated by the computing means;
Discharge processing apparatus characterized in that it comprises a. The method of claim 1,
The processing condition setting means includes: a first processing condition table in which the peak current, the pulse ON time, and the pulse OFF time relating to the discharge machining pulse are set in advance using the processing area as a parameter; And a second processing condition table in which peak currents related to pulses, pulse ON times, and pulse OFF times are set in advance. 3. The method according to claim 1 or 2,
The calculating means includes a first interpole distance h1 and a first total capacitance C1 measured in a state where the electrode is moved to a first moving position, and a second interpole distance measured when the electrode is moved to a second moving position. When h2 and the 2nd total capacitance C2, the 3rd pole distance h3 measured in the state which moved the said electrode to the 3rd moving position, and the 3rd total capacitance C3, and the dielectric constant (epsilon) of a processing liquid are made into the said processing area S, ,
S = h1? H2? H3 (h1 (C2-C3) + h2 (C3-C1) + h3 (C1-C2)) / (ε (h1-h2) (h2-h3) (h3-h1))
The electric discharge machining apparatus, characterized in that for calculating the processing area using the formula represented by. 3. The method according to claim 1 or 2,
The calculating means includes a first inter-pole distance h1 and a first total capacitance C1 measured in a state where the electrode is moved to a first moving position, and a second inter-pole distance measured when the electrode is moved to a second moving position. h2, the second total capacitance C2, the third inter-pole distance h3 measured in the state where the electrode was moved to the third movement position, and the third total capacitance C3, the state measured in the state where the electrode was moved to the fourth movement position. When the fourth inter-pole distance h4 and the fourth total capacitance C4, the error distance α between the inter-pole distances, the dielectric constant ε of the processing liquid, and the processing area S,
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
Where 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 electric discharge machining apparatus, characterized in that for calculating the processing area using the formula represented by. 3. The method according to claim 1 or 2,
The calculating means includes a first interpole distance h1 and a first total capacitance C1 measured in a state where the electrode is moved to a first movement position, and a second interpole distance measured when the electrode is moved to a second movement position. h2 and the second total capacitance C2, the third inter-pole distance h3 measured in the state where the electrode is moved to the third movement position, and the third total capacitance C3, measured in the state where the electrode is moved to the fourth movement position. The fourth interspace distance h4 and the fourth total capacitance C4, the angle θ between the electrode forward end surface and the axis of the electrode, the error distance α between the interpole distances, the dielectric constant ε of the processing liquid, and the processing area S and the interelectrode capacitance C When we did,
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
Where 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 electric discharge machining apparatus, characterized in that for calculating the processing area and the inter-pole capacitance using the equation represented by. 6. The method according to any one of claims 2 to 5,
The processing condition setting means may measure the total capacitance between the electrode and the workpiece of the workpiece by the capacitance measuring means to change the discharge processing condition based on the calculated processing area or inter-pole capacitance. Discharge processing apparatus characterized in that for changing. 6. The method according to any one of claims 2 to 5,
And said processing condition setting means sets a processing current supplied to said electrode so as to be substantially proportional to said calculated processing area or interelectrode capacitance. 8. The method of claim 7,
And said processing condition setting means sets the current density of said processing current to a predetermined current density or less. The method of claim 8,
And said processing condition setting means comprises discharge pulse setting means for setting a processing current supplied to said electrode and a discharge pulse corresponding to said processing area or interelectrode capacitance. The method of claim 4, wherein
And said processing condition setting means has jump operation calculating means for setting at least one of a jump period and a jump amount of a jump operation based on the error distance α of the inter-pole distance.

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