JPH11347846A - Monitor device in wire electric discharge machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To indicate and monitor the sheet thickness change and current density of a work by a real time. SOLUTION: A machining distance calculation device 13 outputs a signal at every time when a prescribed distance machining is proceeded. A main pulse number memory device 14 calculates the main pulse number for discharge machining outputted from a main pulse generator 1 during this signal. A sheet thickness calculation device 16 finds out the sheet thickness from the basic main pulse number when the basic sheet thickness memorized to a basic main pulse number memory device 15 is machined and the main pulse number and basic sheet thickness memorized in a main pulse number memory device 14 at every receiving time of the signal. The found out sheet thickness is indicated on an indicator 12. Further, a machining current, machining speed and machining current density are indicated. As the sheet thickness is indicated by a real time, after looking at this sheet thickness change and changing a machining condition, the machining current can be adjusted and the wire snapping by the sheet thickness change can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine, and more particularly, to a monitoring device for a wire electric discharge machine capable of monitoring a change in a thickness of a workpiece and a change in a machining current density.

[0002]

2. Description of the Related Art FIG. 13 is a diagram showing an outline of a conventional wire electric discharge machine. Reference numeral 1 denotes a main pulse generator which applies a voltage to a gap between the wire electrode 4 and the workpiece 5 for performing electric discharge machining, and is composed of a circuit including a switching element such as a DC power supply and a transistor, and a charge / discharge circuit for a capacitor. ing. A detection voltage generator 2 applies a pulse voltage (a voltage lower than the main pulse voltage) between the wire electrode 4 and the workpiece 5 to detect whether or not a gap between the wire electrode 4 and the workpiece 5 can be discharged. And a circuit including an active element such as a transistor and a resistor and a capacitor, a DC power supply, and the like.

[0003] Reference numeral 3 denotes an energizing brush for energizing the wire electrode 4, and includes a main pulse generator 1 and a detection voltage generator 2.
Are connected to one terminal. The workpiece 5 is connected to the other terminal of the main pulse generator 1 and the detection voltage generator 2, and the main pulse generator 1 and the detection voltage generator are provided between the traveling wire electrode 4 and the workpiece 5. 2 is applied.

A circuit 6 is connected to the workpiece 5 and the wire electrode 4 for determining whether or not the discharge gap is in a dischargeable state due to a decrease in the detection pulse voltage. This is a discharge gap detection device that sends a signal and outputs it to the pulse calculation device 7. The feed pulse calculation device 7 generates a pulse train based on the signal for servo feed, in which the feed pulse interval is controlled so that the average gap voltage is normally constant so that the repetition of discharge is optimal, and the feed pulse distribution is performed. Output to the device 8. The feed pulse distribution device 8 distributes X-axis and Y-axis drive pulses from the pulse train based on a machining program, and drives an X-axis motor control device 9 and a Y-axis motor control device for driving a table on which the workpiece 5 is mounted. Output to 10 A current detection circuit 11 detects a main pulse current and outputs an average machining current value during a predetermined period. Reference numeral 12 denotes a display device. The display device 12 displays the average machining current output from the current detection circuit 11, the average machining voltage output from the discharge gap detection device 6, and the feed speed output from the feed pulse calculation device 7 as data such as numerical values or levels. And display it.

First, in order to detect whether or not discharge is possible between the workpiece 5 and the wire electrode 4, a detection voltage generator 2 is provided.
A detection pulse voltage is further generated and applied to the gap between the workpiece 5 and the wire electrode 4. When a current flows between the workpiece 5 and the wire electrode 4 and a voltage drop occurs between the workpiece 5 and the wire electrode 4, the discharge gap detecting device 6 detects the voltage drop and discharges. The main pulse generator 1 sends a main pulse input signal to the main pulse generator 1 to generate a main pulse. The main pulse current (discharge machining) is applied to the gap between the workpiece 5 and the wire electrode 4. Current). Then, after an appropriate pause time for cooling the gap, the detection pulse is applied to the gap again. This operation cycle is repeatedly performed to perform electric discharge machining.

The state of the repetitive discharge is determined by the discharge gap detecting device 6 and the feed pulse calculating device 7 so that the repetition of the discharge in the gap is usually optimized, and the feed pulse interval is usually set so that the average voltage of the gap is constant. Is generated from the feed pulse calculating device 7, and the feed pulse distributing device 8 uses this pulse train to generate X based on a machining program.
The driving pulse is distributed to the driving pulses of the X-axis and the Y-axis, and output to the X-axis motor controller 9 and the Y-axis motor controller 10, respectively. The table on which the workpiece 5 is placed is driven. Performs machining specified by the machining program. And
By displaying the average machining current detected by the current detection circuit 11, the average machining voltage detected by the discharge gap detection device 6, and the feed speed determined by the feed pulse calculation device 7 on the display device 12, the state at the time of machining is displayed. Is displayed.

[0007]

FIG. 11 shows the average machining voltage and average machining voltage when the workpiece 5 having the cross section shown in FIG. 10 is sliced by the control device of the above-mentioned conventional wire electric discharge machine. It is a monitor waveform of a current. FIG.
As shown by 0, the workpiece 5 has a change in plate thickness, and the average processing voltage changes so as to be substantially constant as a whole with respect to the change in plate thickness. Similarly, the average machining current is almost constant.

Usually, when the thickness of the workpiece 5 changes,
In particular, immediately after the processing is shifted from a thick portion to a thin portion, many disconnections of the wire electrode 4 occur. It is considered that the reason is that the pulse current tends to concentrate at one place in the thin portion. Therefore, conventionally, the pulse current is not concentrated in a thin portion of the plate, and the processing is performed by reducing the processing conditions according to the thin portion of the plate from the start of the processing so that an appropriate average processing current is obtained. ing. This causes a significant reduction in the processing speed.

If the change in the plate thickness is known in advance, for example, if the processing current can be reduced when the plate thickness is reduced, and the current can be increased when the plate thickness is large, the processing time can be shortened accordingly. Conventionally, as a method of knowing a change in plate thickness and adjusting the machining current, a method of reading thickness information from a drawing, inserting machining current increase / decrease information into a machining program, etc., and displaying this at the time of machining is displayed. Has been devised. However, thickness information is not always available directly from the drawing dimensions.
Therefore, when creating a machining program, it is necessary to specifically calculate and instruct thickness information in advance. In addition, when performing wire electric discharge machining after a cutting process such as a cut model or a workpiece has already been roughened by machining, the thickness information may be specially calculated and instructed in advance. , Such work itself is very difficult.

[0010] The electric discharge in electric discharge machining is performed by searching for a minute conductive path such that a gap formed between the electrode and the object to be processed is several tens μm or less by means of a detection pulse or the like, and then using a main pulse. It begins by passing an electric current and forcibly evaporating or melting the minute conductive path or the electrode or the minute part of the workpiece in contact with the minute conductive path by the heat energy generated there. Then, a series of electric discharge machining cycles is completed by the suspension of the current and the cooling action of the machining fluid.

[0011] For the magnitude of the main pulse current peak value having a steep rise, thermal related properties such as heat of dissolution and thermal conductivity of electrodes and workpiece materials, and cooling such as latent heat of vaporization and viscosity of insulating liquid. Processing environment characteristics such as related characteristics determine the degree of evaporation or melting and scattering in both minute portions.

When the plate thickness of the above-mentioned workpiece is small, the period until the next discharge occurs in the vicinity of the discharge portion is shorter than when the plate thickness is large, so that this portion is not sufficiently cooled. Next, the next main pulse current is supplied. Therefore, depending on the above-mentioned machining environment characteristics, heat concentrates on the discharge portion without being completely cooled.
Then, when the next main pulse is applied, it appears whether or not it is still in a molten state. In this case, evaporation or melting and scattering of the electrode and the minute portion of the workpiece cannot be performed, the processing efficiency is extremely reduced, and no further electrical discharge machining can be performed. Even so, when the main pulse is further applied, the wire serving as an electrode is damaged by heating, and eventually loses the tensile strength of the wire during running, leading to disconnection.

Accordingly, an object of the present invention is to provide a wire discharger capable of displaying a workpiece thickness or a machining current density in real time so that a machining current can be adjusted according to a change in the thickness of the workpiece. An object of the present invention is to provide a monitoring device for a processing machine.

[0014]

According to the present invention, a ratio of input energy in machining at a predetermined distance is determined by a ratio of the number of main pulses or an integrated value of an electric discharge machining current in machining at a predetermined distance, and the ratio of input energy is determined by the ratio. Determine the rate of change of the thickness of the workpiece, provided means for detecting the thickness of the workpiece being processed based on the rate of change and the thickness of the workpiece set at the start of processing, the moving distance of the processing path or The relationship between the processing time and the detected thickness of the workpiece is displayed on the display screen of the display device.

Further, means for detecting the thickness of the work being processed by means for detecting the thickness of the work being processed, means for detecting the processing current, and means for detecting the processing current and the detected work thickness and the detected processing current. Means for obtaining a processing current density with respect to the processing surface of the workpiece is provided, and the relationship between the moving distance or processing time of the processing path and the detected processing current density is displayed on the display screen of the display device. Further, a means for detecting the processing speed is provided, and the detected processing speed is displayed on the display screen.

[0016]

FIG. 1 is a functional block diagram of a preferred embodiment of a wire electric discharge machine according to the present invention and its monitor apparatus. The same components as those of the conventional wire electric discharge machine shown in FIG. 13 are denoted by the same reference numerals. The difference from the conventional wire electric discharge machine is that it is connected to the X-axis motor control device 9 and the Y-axis motor control device 10 and inputs a feedback signal from a position detector attached to the motor of each axis to reduce the machining distance. The machining distance calculating device 13 that outputs a signal every time it moves for a predetermined machining distance, the main pulse number storage device 14 that counts the main pulse application command signal from the discharge gap detecting device 6, and the reference main pulse number are set and stored. The reference main pulse number storage device 15, which calculates the plate thickness change rate of the workpiece based on the output of the main pulse number storage device 14 and the output of the reference main pulse number storage device 15 as described later, and calculates the plate thickness. The arithmetic unit 16 receives the calculated plate thickness, the average machining current output from the current detection circuit 11, and the average machining feed speed output from the feed pulse arithmetic unit 7. And, in that the display device 12 for displaying these are provided.

A detection pulse voltage is generated by the detection voltage generator 2 and applied to the gap between the workpiece 5 and the wire electrode 4. When a current flows between the workpiece 5 and the wire electrode 4 and a voltage drop occurs between the workpiece 5 and the wire electrode 4,
The discharge gap detector 6 detects this voltage drop, determines that discharge is possible, sends a main pulse application command signal to the main pulse generator 1, causes the main pulse generator 1 to generate a main pulse, and Workpiece 5 and wire electrode 4
Main pulse current (Electric discharge machining current) with a predetermined width in the gap
Flow. The main pulse application command signal is input to the main pulse number storage device 14 and counted.

Thereafter, after an appropriate pause time for cooling the gap, an operation cycle in which the detection voltage is applied to the gap again by the detection voltage generator 2 is repeatedly executed. Further, the discharge gap detecting device 6 outputs a signal for servo feeding to the sending pulse calculating device 7, and outputs the signal to the sending pulse calculating device 7.
In the present embodiment, a pulse train in which the feed pulse interval is controlled so that the machining average voltage coincides with the set voltage (servo voltage) so as to optimize the repetition of discharge in the gap is generated by the feed pulse distribution device 8. Output to The feed pulse distributor 8 uses this pulse train to generate X based on a machining program.
X-axis motor control device 9 and Y-axis motor control device 10, respectively, and drive the table on which workpiece 5 is mounted. And perform the processing specified by the processing program.

The processing distance calculating device 13 calculates and sets a relative moving distance of the wire electrode 4 with respect to the workpiece 5 based on a position feedback signal from a position detector attached to the X-axis and Y-axis motors. A signal is output to the main pulse number storage device 14 and the plate thickness calculation device 16 every time the predetermined processing distance is moved. Main pulse number storage device 14
Receives this signal, resets the stored value, and starts counting the main pulse input signal again. Further, the thickness calculating device 1
4 receives the signal and obtains the plate thickness based on the number of main pulses stored in the main pulse number storage device 14 before being reset and the reference main pulse number set and stored in the reference main pulse number storage device 15. The obtained thickness is output to the display device 12, and the display device 12 graphically displays the thickness as a function of the processing time or the processing distance. Further, the average machining current from the current detection circuit 11 and the average machining speed from the feed pulse calculation device are input to the display device 12, and these data are also displayed as a graph as a function of machining time or machining distance.

Therefore, a method of calculating the sheet thickness performed by the sheet thickness calculating device 14 will be described. FIG. 2 shows that the sheet thickness is T (n).
FIG. 4 is an explanatory diagram of a method of calculating a plate thickness in wire electric discharge machining for a workpiece which changes from T to (n + 1). ΔL: set predetermined machining distance g: machining allowance A: wire diameter P: number of effective discharge pulses generated during machining for ΔL Q: number of short-circuit discharge pulses generated during machining for ΔL w1: effective discharge pulse 1 Machining amount per shot w0: machining amount per one short-circuit discharge pulse Given that the wire electrode 4 moves relative to the workpiece 5 by a set predetermined machining distance ΔL, the machined amount is equal to the machined amount. Since the processed amounts are equal, the following relational expression is obtained. (2g + A) × T × ΔL = P × w1 + Q × w2 (1) Here, T means T (n) or T (n + 1) in FIG.

If machining is proceeding with high machining efficiency, the number of short-circuit discharge pulses is small and P >> Q, and the machining amount w0 per short-circuit discharge pulse is Since the processing amount w1 is very small compared to the processing amount w1 and w1 >> w0, the plate thickness T can be approximated by the following two expressions by rearranging the above expression (1). T = [w1 / (2g + A)] × (P / ΔL) (2) In the above two expressions, w1 and g are values which are substantially determined by the materials of the workpiece and the wire electrode, the pulse current peak value, and the current pulse width. Yes, it can be regarded as constant as long as the processing proceeds under the same conditions. In addition, since the value of the wire diameter A is uniformly determined by the wire electrode used, if these values are set in advance, the thickness T can be calculated from the above equation by measuring (P / ΔL). You can ask.

In FIG. 2, the plate thickness at the position Ln is represented by Tn,
And the number of effective discharge pulses counted when machining for a predetermined machining distance ΔL is P (n), the plate thickness at the position Ln + 1 is T (n + 1), and the number of effective discharge pulses is P (n + 1). ), Tn = [w1 / (2g + A)] × (P (n) / ΔL) T (n + 1) = [w1 / (2g + A)] × (P (n + 1) / Δ
L) Therefore, if the plate thickness change rate is β, β = T (n + 1) / Tn = P (n + 1) / P (n). In addition, P (n + 1) and P (n) mean the input energy amount when performing the processing of the predetermined processing distance ΔL if the pulse current peak value and the current pulse width are constant. Therefore, the number of main pulses (the number of effective discharge pulses) generated when the reference plate thickness Ts is processed by the set predetermined processing distance ΔL is stored in the reference main pulse number storage device 15 as the reference pulse number Ps. Each time the distance calculating device 13 detects that the set predetermined processing distance ΔL has been moved, the number of main pulses P counted and stored by the main pulse number storage device 14 during the moving distance is obtained. And the reference pulse number Ps, that is, β = P / Ps can be obtained from the input energy amount (P) and the reference energy input amount (Ps).

Here, the rate of change of the sheet thickness with respect to the reference sheet thickness is β =
T / T (s), the obtained thickness change rate β (= P
/ Ps) is multiplied by the reference thickness Ts to determine the thickness T of the workpiece 5 being processed. T = Ts × (P / Ps). FIG. 4 is a block diagram of a main part of an embodiment of the present invention. In this embodiment, the control device 100
As shown in FIG.
15 are executed by the control device 100. The same elements as those shown in FIG. 1 are denoted by the same reference numerals.

The control device 100 includes a monitor CPU (monitor processor) 102 for monitoring discharge, calculating a servo feed amount, monitoring the number of main pulses of discharge, and the like, and the work piece 5.
Servo CPU for driving and controlling the X-axis and Y-axis servomotors for moving the laser beam relative to the wire electrode 4
(Servo control processor) 105, creation of display data, control of drawing and display, and furthermore, PMCCPU (processor for programmable machine controller) 109 for sequence control of the wire electric discharge machine, and control of a machining position based on a machining program. A CNC CPU (Numerical Control Processor) 112 is provided.
16 are connected. Further, an input / output circuit 101 and a display device & MID (manual input device with display device) 105 are connected to the bus 116.

A bus 103 includes a ROM 103 storing a system program for a monitor CPU and a RAM 104 provided with a table for storing detection monitor data to be described later.
06, and the digital servo CPU 105
A ROM 106 for storing a system program for performing servo control, a RAM 107 used for temporary storage of various data, and a servo amplifier 108 for driving and controlling the X-axis and Y-axis servo motors are connected by a bus. Also,
The servo amplifier 108 is connected to a servomotor for each axis, but FIG. 4 shows only one servomotor 20. Although not shown, a position / speed detector for detecting the relative position and speed of the workpiece 5 with respect to the wire electrode 4 is attached to each servomotor.

The PMC CPU 109 also has the CPU 109
110 for storing a system program for the CPU 112, a RAM 111 used for temporary storage of data, etc., are connected to the bus, and a ROM 113 for storing a system program for the CPU 112, a RAM 114 used for temporary storage of data for the CNC CPU 112, etc. Are connected to the bus. Control device 100 constituted by the above-described CNC device
Is the same as the conventional control device without any difference.

As with the conventional control device, the CNC CPU 1
12 controls the feed pulse interval based on the processing program stored in the RAM 114 so that the average processing voltage of the gap between the workpiece 5 and the wire electrode 4 is constant (controls the feed speed). ) Distribute the movement command to each axis, digital servo CPU, the distributed movement command and the position from the position / speed detector attached to each servo motor,
The position and speed feedback control is performed based on the speed feedback signal, and the servo motors 20 of the respective axes are drive-controlled via the servo amplifier 108. Also,
The discharge gap detecting device 6 detects that the discharge gap is in a dischargeable state due to a decrease in the detection pulse voltage, as in the related art, and the main pulse generator 1 and the input / output circuit 101
The main pulse generator 1 generates a main pulse and causes a main pulse current (electric discharge machining current) to flow through a gap between the workpiece 5 and the wire electrode 4. Further, the current detection circuit 11 detects the machining current and outputs an average machining current I during a predetermined cycle to the input / output circuit 101. The above operation is the same as that of the conventional control device.

The present invention is characterized in that in such a control device 100, the thickness and the like of the workpiece 5 can be displayed and monitored in real time. 5 and the flowchart shown in FIG.

FIG. 5 is a flowchart of a monitor data fetching process executed by the monitor CPU 102 at predetermined intervals by a multitask process. First, the operator inputs the thickness of the workpiece 5 at the start of processing as the reference thickness Ts, and stores it in the table 30 provided in the RAM 104 as shown in FIG. Then, when the machining command is input, the CNC CPU 112 distributes the movement command to each axis based on the machining program to start the machining, but the monitor CPU 102 executes the writing for designating the address of the table 30 storing the monitor data. The register storing the index n, the flag F, the timer t, and the number of main pulses P is reset to "0" (step A1), and it is determined whether the electric discharge machining is completed (step A2).
It is determined whether the machining distance has advanced the set distance ΔL (step A3). Steps A2 and A3 are repeated until it is detected that the set distance ΔL has been advanced.

Although the calculation of the distance ΔL is not shown in the flowchart, the digital servo CPU
In the process of 105, each axis current value register for accumulating the position feedback signals fed back from the X / Y axis position / velocity detector and storing the current position is stored in the RAM.
107. The value of each axis current value register is stored at the start of machining and each time movement of the predetermined distance ΔL is detected, and the value of each axis current value register detected at each processing cycle and the stored value are stored. The movement amount is obtained from the difference, and it is determined whether the movement amount is equal to or greater than the set distance ΔL.

The monitor CPU 102 simultaneously monitors the main pulse application command signal output from the discharge gap detecting device 6 in parallel with the processing shown in FIG. Is stored in the register inside.

If it is detected in step A3 that the amount of movement has exceeded the set distance ΔL, the monitor CPU
Reference numeral 102 denotes the main pulse number P and the value of the timer t stored at that time, the processing speed (feed speed) V at this time calculated by the CNC CPU 112, and the average processing output from the current detection circuit 11. Current I
Is read (step A4). Next, the flag F is set to “0”.
If the flag F is “0” and it is detected that the machining has been started and the machining of the first set distance ΔL has been completed,
The number of main pulses P read in step A4 is stored in the table 30 as the reference number of main pulses Ps (step A6), the flag F is set to "1", and the register for storing the number of main pulses P is reset (step A6).
7), the process proceeds to step A2.

If it is detected that the set distance .DELTA.L has been moved during the repetitive execution of the processing of steps A2 and A3, the operation proceeds to step A4, where the number of main pulses P, the value of the timer t,
The processing speed V and the average processing current I are read, and since the flag F is set to "1", the process proceeds from step A5 to step A8. Then, the index n is incremented by "1", and the number of main pulses P read at step A4 is
The value of the timer t, the machining speed V, and the machining current I are respectively stored in the address of the table 30 indicated by the index n as Pn, tn, V
Stored as n and In (step A9). Next, the register storing the number of main pulses P is reset (step A10), and the process returns to step A2. Hereinafter, steps A2
The processes of A5 and A8 to A10 are repeatedly executed, and the main pulse number P, the value of the timer t, the machining speed V, and the machining current I each time machining of the set distance ΔL progresses until electric discharge machining is completed.
Are stored in the table 30 as shown in FIG.

FIG. 6 is a flowchart of the monitor data display processing executed by the PMC CPU 109. When the monitor data display screen is selected. The PMC CPU 109 starts the process of FIG. 6, first sets a reading index i designating an address for reading data from the table 30 to “1” (step B1), and stores the reference plate thickness stored in the table 30. Ts and the reference main pulse number Ps are read (step B2). Next, it is determined whether the data reading index i is larger than the index n specifying the data write address (step B3). If the value of the index i is smaller than the value of the index n, the horizontal axis of the display screen indicates the distance. It is determined whether or not the time is set (step B4). If the horizontal axis is set to time, the process proceeds to step B5, and the table 30 is set.
From the data P stored at the address indicated by the index i
Read i, ti, Vi, and Ii. Then, as described above, the value obtained by dividing the read main pulse number Pi by the reference main pulse number Ps (this value means the plate thickness change rate β as described above) is multiplied by the reference plate thickness Ts. Sheet thickness Ti
(Step B6). Further, a current density Di is obtained by dividing the read average processing current Ii by the thickness Ti obtained in step B6 (step B7).

Next, the horizontal axis represents time, the vertical axis represents plate thickness, current density, machining speed, and machining current (see FIG. 7), the horizontal axis represents the position corresponding to the read timer value ti, and the vertical axis represents the time. Obtained sheet thickness Ti, current density Di, processing speed Vi, processing current I
The position corresponding to i is obtained, and the plate thickness Ti, the current density Di, the processing speed Vi, and the processing current Ii are displayed on the display screen of the display device & MDI 105 at the positions where the obtained positions of the horizontal axis and the vertical axis intersect. (Step B8). Thereafter, the index i is incremented by "1" (step B9), and it is determined whether the screen has been switched (step B10). If the screen has not been switched from the monitor screen, it is determined whether the horizontal axis has been switched and the distance has been set. (Step B16) If the switching is not performed and the horizontal axis indicates time, the process proceeds to (Step B3. If no screen switching or horizontal axis switching is performed, the reading index i is replaced with the writing index. The processing of steps B3 to B10 and B16 is repeatedly executed until the number exceeds n, and the display screen of the display device & MDI 105 uses the horizontal axis as a time axis, the plate thickness, the current density, the processing speed, and the processing as shown in FIG. The current is displayed.

When the index i exceeds the index n, (from step B3 to (step B10, the new drawing processing is stopped. On the other hand, as shown in FIG. 5, the index n becomes "1" by the processing of step A8). Is incremented and new monitor data is added to the table 30. Since the values of the index i and the index n match in step B3, the processing is performed in steps B4 and B5, and the display processing described above is performed, The current density, the processing speed, and the processing current are additionally displayed on the display screen (steps B6 to B6).
8). That is, every time the machining distance advances by ΔL, the monitor data P
i, ti, Vi, and Ii increase, and based on the increased monitor data, the plate thickness Ti, the current density Di, and the processing speed V
i and the processing current Ii are obtained and additionally displayed on the display screen, and these data are displayed in real time.

When the distance is set on the horizontal axis, the process shifts from step B4 to step B11, and the same processing as step B1 to step B1 described above is performed in step B1.
1 to B13, the sheet thickness Ti and the current density Di
And the horizontal axis represents the distance, and these data are placed at positions corresponding to the plate thickness Ti, current density Di, machining speed Vi, and machining current Ii on the vertical axis at the horizontal axis position corresponding to the position obtained by multiplying the index i by ΔL. Is displayed in a graph (step B14). Then, the index i is incremented by "1", and step B1 is performed.
0, and if there is no screen switching or horizontal axis switching, steps B3 and B3 are performed until the index i exceeds the value of the index n.
The processes of 4, B11 to B15, B10, and B16 are repeated, and as shown in FIG. 8, the thickness is displayed on the horizontal axis, the plate thickness Ti, the current density Di, the processing speed Vi, and the processing current Ii are displayed.

In this case as well, the display stops when the reading index i exceeds the value of the writing index n, but the writing index n is incremented and new monitor data is written in the table 30. Immediately, the processing of steps B3, B4, B11 to B15 is executed, and the new sheet thickness Ti, current density Di, processing speed Vi,
The machining current Ii is displayed and is displayed in real time.

Further, when the operator changes the horizontal axis from time to distance or from distance to time, the PMC
The CPU 109 detects this in step B16, returns to step B1, executes the display processing from the beginning, and re-executes drawing according to the horizontal axis set to time or distance.

As described above, the thickness Ti, current density Di, machining speed Vi, and machining current Ii are displayed in real time on the display screen. Changes, the plate thickness on the display screen also changes. FIGS. 7 and 8 show monitor display screens obtained when processing the workpiece 5 whose thickness changes as shown in FIG. 10. When the thickness decreases, FIGS. As shown in FIG. 8, the display plate thickness also decreases. Further, as is apparent from FIG. 11, the average processing current is almost constant and does not change. Therefore, the current density Di obtained by dividing the average processing current Ii by the obtained plate thickness Ti increases (FIG. 7, FIG. 7). 8, this increased current density Di is not shown). Therefore,
The operator confirms that the thickness has changed on the display screen, and determines the pause time of the pulse applied to the gap between the workpiece 5 and the wire electrode 4 or the feed speed (between the workpiece 5 and the wire electrode 4). The servo voltage in the servo feed control for controlling the feed rate so that the average machining voltage of the gap becomes the set servo voltage) or the voltage of the applied pulse is adjusted so that the displayed current density Di is constant, Adjust the machining current so that there is no change before and after the thickness change. 7 and 8
Indicates the current density Di after this adjustment.

7 and 8, the current density Di is adjusted so that it does not change even if the plate thickness changes. If the plate thickness decreases, the average processing current value also decreases, and conversely, the processing speed decreases. It can be seen that it has increased. FIG. 12 shows that, when the workpiece 5 whose thickness changes as shown in FIG. 10 is processed, the processing current is adjusted when the thickness changes according to the present invention, and the thickness decreases by 50% in accordance with the thickness change. FIG. 12 is a graph showing the processing average voltage and the processing average current when the processing current is reduced by 50% at the time. FIG. 12 is compared with FIG. 11 when the processing is performed by the conventional method. In the present invention shown in FIG. 12, processing conditions (processing current) more suitable for the plate thickness can be used, so that the processing time is short and the processing is completed in about 14 minutes. However, according to the conventional method, since the processing conditions (processing current) are determined according to the case where the plate thickness is small,
When the plate thickness is large, the processing time becomes long, and a processing time of about 20 minutes is required.

When the thickness changes in three steps as shown in FIG. 10, the thickness to be processed first is Ts,
The reference main pulse number at that time is Ps, and the thickness of the second stage is T
1. If the thickness of the third stage is T2 and the number of main pulses when the thickness changes from Ts to T1 is P1, the thickness T1 of the second stage is T1 = Ts · (P1 / Ps (3) Therefore, it is assumed that the number of main pulses when the machining current is adjusted and the second thickness is machined is P2. However, before and after adjusting the machining current, although the machining speed changes, the machining amount is constant because the plate thickness is constant and the moving distance ΔL is machined, and the input energy is constant.
The relationship of 1 = P2 holds. Further, if the number of main pulses when the thickness changes from the second stage to the third thickness is P3, then from the relationship between the second stage and the third stage,
The reference plate thickness is T1 and the reference main pulse number is P2. From the above three equations, the plate thickness T3 of the third stage is: T3 = T1 · (P3 / P2) = Ts · (P1 / Ps) ·
(P3 / P2) As described above, since P2 = P1, T3 = Ts. (P3 / Ps) (4), and the plate thickness changes many times, and the machining current is adjusted each time. However, the sheet thickness Ti can be obtained from the initially set and obtained reference sheet thickness Ts, the reference main pulse number Ps, and the number of main pulses Pi each time the ΔL processing proceeds. <Second Embodiment> In the above-described embodiment, a voltage lower than the main pulse voltage is applied to the gap between the workpiece 5 and the wire electrode 4 by the detection voltage generator 2, and the voltage in this gap decreases. And the power supply for applying the main pulse is determined. Thereby, the energy of the discharge by one main pulse is constant. Therefore, by counting the number of main pulses applied between the workpiece 5 and the wire electrode 4, the input energy amount for electric discharge machining could be obtained. Instead of counting the number of main pulses, the discharge current may be integrated to determine the input energy amount. Then, the integrated value of the discharge current every time the machining proceeds by ΔL is obtained, and the sheet thickness can be obtained from the integrated value.

In particular, the method of determining the input energy amount based on the integrated value of the discharge current and detecting the sheet thickness based on the input energy amount (the integrated value of the discharge current) is the same as the above-described embodiment. Although it can be applied to the case where the value and the time width are constant, it is rather suitable when the values and the time widths of the respective discharge currents are different. For example, an electric discharge machining power supply using a conventionally known capacitor discharge as a power supply, or an electric discharge machining power supply in a case where a DC voltage is simply applied between a workpiece 5 and a wire electrode 4 by a switching element or the like to wait for discharge. Suitable when using. For example, as shown in FIG. 9, a gate is opened for a set ON time by a switching element or the like between the workpiece 5 and the wire electrode 4 to apply a capacitor charging voltage or a DC power supply voltage. Workpiece 5 and wire electrode 4
In the case of an electric discharge machining power supply that performs electric discharge machining when a discharge occurs during the discharge, the peak and time width of the discharge current fluctuate depending on the discharge start time, and as shown in FIG. Will have different amounts of energy in the discharge current. For this reason, instead of counting the discharge pulses, the integrated value of the discharge current is obtained to obtain the input energy amount consumed for the electric discharge machining, and is used instead of the main pulse number P in the above-described embodiment.

In this case, the monitor CPU of the control device 100
The process executed by 102 does not count the number of main pulse application commands from the discharge gap detection device, that is, the number of main pulses P, but reads the average machining current output from the current detection circuit 11 at predetermined intervals and stores the average machining current in the register. The present embodiment is the same as the above-described embodiment except that the integration is performed and this current integrated value is used instead of the main pulse number P. In the monitor data acquisition process shown in FIG. 5, it is only necessary that P be an integrated current value. Also, in the monitor data display processing shown in FIG. 6, P may be the current integrated value. <Third Embodiment> In the first and second embodiments described above, as a method for obtaining the plate thickness, (Step B6 in FIG. 6)
As shown by B12, the reference plate thickness Ts and the reference input energy amount Ps (the number of main pulses or the integrated discharge current) corresponding to the reference plate thickness were used. Instead of processing the set distance Δ
Every time L advances, the sheet thickness Ti of the current time may be obtained from the previously obtained sheet thickness Ti-1 and the input energy amount Pi-1. In this case, the processing shown in FIG. 5 is performed by setting the sheet thickness set before the start of machining as an initial value in a register for storing the previous sheet thickness, and in step A6, the obtained input energy amount P
(The number of main pulses or the integrated value of the discharge current) is stored in a register that stores the amount of energy input last time. Otherwise, the same processing as the processing shown in FIG. 5 is performed to create a table 60 as shown in FIG.

On the other hand, in the process of FIG. 6, the process of step B2 is not performed, and the process proceeds from step B1 to step B3. In the processes of steps B5 and B11, the data Pi, ti, Vi, and Ii stored in the table 30 are stored. And the sheet thickness and the input energy amount are read from the register storing the previous sheet thickness and the input energy amount. The read sheet thickness and input energy amount are set as T
i-1 and Pi-1. In the sheet thickness calculation processing in steps B6 and B12, the following equation is obtained: Ti = Ti-1 · (Pi / Pi-1) (5) to obtain the sheet thickness Ti.

Then, the obtained sheet thickness Ti and the current input energy amount Pi are stored in a register for storing the previous sheet thickness and input energy amount, and the process proceeds to steps B7 and B1.
Move to 3. Subsequent steps are the same as the processing in FIG.

By the above processing, if the plate thickness of the workpiece 5 does not change, the processing amount of the processing distance ΔL does not change and the input energy amount does not change, so that the previous input energy amount Pi− 1 and the input energy amount Pi of the current cycle are substantially equal, and the thickness Ti obtained from the above equation is the same as the previous thickness Ti-1. On the other hand, when the plate thickness changes, a difference occurs in the processing amount when processing is performed by the processing distance ΔL according to the change in the plate thickness. The difference in the amount of processing also causes a difference in the input energy amount, so that there is a difference between Pi and Pi-1. As a result, the thickness Ti changed by the above equation (5) is obtained, and this thickness is stored in the register for storing the previous thickness. In this way, the previous sheet thickness,
And the sheet thickness can be sequentially obtained based on the input energy.

[0048]

According to the present invention, since the plate thickness or the current density is detected and displayed, a change in the plate thickness can be immediately known and the processing conditions can be adjusted. Thereby, wire breakage at the time of a change in plate thickness can be prevented. Further, by displaying the feed speed and the processing current in addition to the sheet thickness, the processing state can be grasped in real time.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an embodiment of a wire electric discharge machine according to the present invention and a monitor device thereof.

FIG. 2 is an explanatory diagram for explaining a method of detecting a plate thickness according to the present invention.

FIG. 3 is an explanatory diagram of a table for storing monitor data according to the first embodiment of the present invention.

FIG. 4 is a main part block diagram of the first embodiment of the present invention.

FIG. 5 is a flowchart of monitor data acquisition in the first embodiment.

FIG. 6 is a flowchart of a monitor data display process according to the first embodiment.

FIG. 7 is a diagram showing a display example of monitor data with the horizontal axis representing time according to the first embodiment;

FIG. 8 is a diagram showing a display example of monitor data with a horizontal axis as a distance in the first embodiment.

FIG. 9 is an explanatory diagram of a discharge current in an electric discharge machining power supply in which the peak value and the width of the discharge current are not constant.

FIG. 10 is an explanatory diagram of a workpiece whose thickness changes.

11 is a monitor diagram of a processing average current, a processing average voltage, and the like when the workpiece illustrated in FIG. 10 is processed by a conventional method.

12 is a monitor diagram of a processing average current, a processing average voltage, and the like when the workpiece illustrated in FIG. 10 is processed according to the present invention.

FIG. 13 is an explanatory diagram showing a functional configuration of a conventional electric discharge machining control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main pulse generator 2 Detection voltage generator 3 Electric brush 4 Wire electrode 5 Workpiece 6 Discharge gap detection device 7 Feed pulse calculation device 8 Feed pulse distribution device 9 X-axis motor control device 10 Y-axis motor control device 11 Current detection Circuit 12 Display device 13 Processing distance calculation device 14 Main pulse number storage device 15 Reference main pulse number storage device 16 Plate thickness calculation device 20 Servo motor 30 Table 100 Control device

Claims (8)

[Claims] 1. A monitor device for a wire electric discharge machine, which detects a thickness of a workpiece during machining, and displays a relationship between a moving distance or machining time of a machining path and the detected thickness of the workpiece. A monitor device in a wire electric discharge machine that is displayed on a display screen of the device. 2. A monitoring device for a wire electric discharge machine, wherein a machining current density on a machining surface of a workpiece being machined is detected, and a relationship between a moving distance or machining time of a machining path and the detected machining current density. Monitor device in a wire electric discharge machine, which displays on a display screen of a display device. 3. At least one of a processing current, a processing speed, and a processing current density with respect to a processing surface of a workpiece during processing.
2. A monitor device in a wire electric discharge machine according to claim 1, wherein the relationship between the moving distance or machining time of the machining path and the detected machining current, machining speed, or machining current density with respect to the machining surface of the workpiece is detected. . 4. The relationship is graphically displayed with the moving distance or the processing time of the processing path as a horizontal axis.
A monitor device in the wire electric discharge machine according to claim 2 or 3. 5. The wire electric discharge machine according to claim 2, wherein the detection of the machining current density is performed by detecting a thickness of the workpiece during machining and a machining current, and obtaining from the detected machining current and the thickness of the detected workpiece. Monitor device. 6. The method for detecting the thickness of a workpiece includes determining a rate of change in the thickness of the workpiece based on a ratio of input energy in processing at a predetermined distance, and determining the rate of change and the workpiece set at the start of processing. 6. A monitor device in a wire electric discharge machine according to claim 1, wherein the monitor device is obtained from a thickness of an object. 7. A monitor device in a wire electric discharge machine according to claim 6, wherein the ratio of the input energy is obtained by a ratio of the number of main pulses for performing electric discharge machining. 8. The monitor device according to claim 6, wherein the ratio of the input energy is obtained by a ratio of an integrated value of the electric discharge machining current.