JPS6260212B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining apparatus having an unmanned electric discharge machining operation device that can automatically set machining pulse conditions and machining stabilization conditions in electric discharge machining work.

The machining system in electric discharge machining is as follows. The electrode shape, electrode material, pulse current, and pulse width are selected and processed to satisfy the required conditions such as the shape of the workpiece, material, and surface roughness. In electrical discharge machining, the first step is usually rough machining with a predetermined machining allowance left under pulse conditions with high machining efficiency and low electrode consumption, then semi-finishing, and finally pulsed current and pulsed machining. Processing is performed by setting the finishing processing conditions that reduce the width, and the desired shape is completed. These are processed in advance according to the machining depth using a well-known program controller.
If the above-mentioned rough, semi-finishing, and finishing processing pulse conditions are set, it is possible to automatically switch settings. In addition, in each process such as roughing, semi-finishing, and finishing, electrodes may be replaced and conditions may be changed. Electrode replacement is performed automatically using a well-known method in which the NC device and electrode replacement device are linked. It is carried out in Furthermore, in a machining method in which the electrode or workpiece is moved relative to each other to change the gap between an arbitrary machining surface or a machining part, the pattern or amount of change is programmed using an NC device or the like. However, in addition to the above pulse conditions, machining stabilization conditions such as machining fluid pressure, machining voltage, pulse duty factor, and electrode reciprocating motion, which are necessary to perform efficient and stable electrical discharge machining, must be set to appropriate values. Must be.

Conventionally, there was no device that automatically controlled such processing stabilization conditions by following a program controller or NC device. Processing workers had to manually make the above settings, resulting in poor processing efficiency.

The present invention eliminates the drawbacks of the above-mentioned conventional techniques and enables unmanned operation of electric discharge machining.The present invention enables unmanned operation of electric discharge machining. , a program controller in which pulse conditions, etc. are programmed, and an optimum control device that automatically controls machining stability conditions other than the pulse conditions to optimal values are provided, and the pulse conditions are generated from the program controller or NC device. This electric discharge machine is characterized in that it is equipped with a coupling circuit that operates the optimum control device according to a switching signal such as a pulse condition.

An embodiment of the present invention will be explained in detail below using the drawings. FIG. 1 is a block diagram showing an embodiment of the electrical discharge machining apparatus according to the present invention. 1 is an electrode, 2
is a workpiece, 3 is a pulse power source, 4 is a program controller, 5 is a discharge state detection circuit, 6 is a machining stability control circuit, 7 is an electrode feed drive circuit, 8 is a machining fluid pressure drive circuit, 9 is a machining fluid supply nozzle, 10 is an NC device, 11 is an electrode exchange device, 12 is a table X-axis drive circuit, 13 is a table Y-axis drive circuit, 14
indicates an electrode feed amount detection processing device.

Next, the operation of the above block diagram will be explained. When machining starts, the electrodes programmed in the NC device 10 are set in the electrode feeding device by the electrode exchange device 11, and the workpiece is set at the programmed position by the table X-axis drive circuit 12 and table Y-axis drive circuit 13. . Further, a first processing condition command signal V for that electrode is sent to the program control 4. In advance by command signal V,
A pulse condition setting signal programmed in the program controller 4 is given to the pulse power source 3, and a predetermined pulse condition is outputted from the pulse power source 3 to the electrode 1.
and the workpiece 2 (hereinafter referred to as "between the electrodes"). From program controller 4 to pulse power supply 3
As shown in the figure, the pulse condition setting signal given to
C is the peak voltage of the pulse, D is a command signal indicating whether or not to use a capacitor circuit when supplying minute pulses, and E is for setting the polarity of the pulse voltage. Further, the program controller 4 outputs to the electrode feed drive circuit 7 a command signal N related to a selection signal indicating whether or not to perform the gain electrode pulling movement of the electrode feed servo system. The plurality of sets of conditions programmed in the program controller 4 are switched by the output signal X from the electrode feed amount detection processing device 14 in addition to the command signal V from the NC device 10 described above. The electrode feed amount detection processing device 14 is a device that outputs an output signal when the electrode is fed to a preset electrode feed amount, and is capable of setting a plurality of electrode feed amounts. Next, the discharge state detection circuit 5
As a result, the discharge state is detected based on the machining voltage waveform, and the detection signal W is given to the machining stability control circuit 6. The detection sensitivity of the discharge state, etc. is automatically determined based on the signal given from the program controller 4, the pulse peak voltage (symbol C), the capacitor circuit usage signal (symbol D), the polarity (symbol E), the processing material (symbol G), etc. selected. Further, the discharge state is detected for each machining pulse by the symbol I of the timing pulse signal synchronized with the pulse cycle generated from the pulse power source. Next, the machining stability control circuit 6 sets the optimum values of the machining voltage V and the pulse at the duty factor so that the discharge machining state becomes the best based on the signal detected by the discharge state detection circuit 6. Power supply 3, machining fluid pressure P
Electrical discharge machining is performed by applying the optimum value of to the machining fluid pressure drive circuit 8 and the electrode lifting period T to the electrode feed drive circuit 7. Here, the machining voltage U corresponds to the gap between the electrodes, and the electrode feed is controlled by the electrode feed drive circuit 7 so that the gap is set narrower when the machining voltage is lower. The processing stability control circuit 6 includes the program controller 4
A sequential pattern switching signal F, a material selection signal G, and a start signal H are given as command signals generated from the controller. The signals F and G are used to select an operating procedure pattern for finding the optimum value of the processing stability conditions. The start signal H starts the control operation by starting machining. This start signal H can be programmed to be generated only at the start of machining, or to be generated when transitioning from rough machining conditions to semi-finishing.

FIG. 2 shows a specific example of a method for detecting a discharge state when pulse voltages are different in the circuit configuration described above, and FIG. 3 shows details of the detection circuit. Here, the peak voltage of the pulse is the waveform J
A method of detecting a discharge state using a waveform _{L shown in FIG. 1 in which J T (} for example, 100 V) and a high voltage J _B (for example, 300 V) are superimposed with a phase difference will be described. When a pulse with a waveform J or L is applied from the pulse power supply 3 between the electrodes, the waveform during normal discharge becomes a waveform K or M between the electrodes. Timing pulse T ₁ or when applying pulse
The time T ₁ ' is higher than the detection level E ₃ or E ₃ ', and the ta during discharge is between the detection levels E and E ₂ , so these can be detected as normal discharge. Figure 2 shows only normal arc discharge, but in abnormal arc discharge, the voltage between the electrodes reaches the detection level at the position of the timing pulse T ₁ or T ₁ '.
Abnormal arc discharge can be detected when it is below E ₃ or E ₃ '. As described above, when the peak voltages of the pulses differ, it is necessary to switch the detection levels E ₃ and E ₃ ' and switch the timing pulses T ₁ and T ₁ '.
This switching is performed by a switching signal from the program controller. Next, the configuration of the discharge state detection circuit according to the above method shown in FIG. 3 will be explained. In FIG. 3, the same parts as in FIG. 1 are indicated by the same symbols. 501 and 502 are voltage dividing resistors for dividing the voltage between the electrodes into a low voltage to the extent that IC etc. are not damaged, and the divided voltage between the electrodes is passed through the first comparator 503 and the second comparator. 504
and each input of the third comparator 505. The other input of each of the comparators described above is connected to a third setting level switching device according to the detection levels E ₁ and E ₂ shown in FIG. 2 and the program signal C from the program controller 4 according to the peak value of the pulse. relay 513 is switched to provide E ₃ or E ₃ '. When the output of the first comparator 503 and the output of the second comparator 504 are applied to an AND gate 506, the time ta during which the discharge shown in FIG. 2 occurs is detected. On the other hand, if the peak voltage of the signal C from the program controller is a pulse like the waveform J shown in FIG.
3 is connected to the detection level _E3 , which is given to the third comparator 505, and the timing pulse is sent by the timing pulse switching relay 514.
Since T ₁ is selected, if it is in a normal discharge state, it is given to the third comparator 505,
As the timing pulse, _T1 is selected by the timing pulse switching relay 514, so if it is in a normal discharge state, an output is obtained from the third comparator 505, and this output is equal to the timing pulse _T1.
The output signal is applied to AND gate 507, which sets flip-flop 508. The reset input of the flip-flop 508 receives a timing pulse from a timing pulse generator 511 that is generated based on the pulse waveform of the pulse power supply.
Reset by _T2 . Note that 512 is a delay circuit for delaying T ₁ ' by a predetermined time to obtain a timing pulse T ₁ . the above,
When the output of the AND gate 506, the output Q of the flip 508, and a signal with the same pulse width as the pulse waveform J are applied to the AND gate 509, the waveform O shown in FIG. 2 is obtained, and the discharge time ta is 509 output. In addition, if an abnormal arc discharge state occurs, the third comparator 505
Since no output is obtained and the flip-flop 508 is not set, the inverted output Q of the flip-flop 508 becomes a logic "1" level, and as a result,
Although not shown, an abnormal arc discharge detection signal is obtained from the AND gate 510. If this abnormal arc discharge occurs continuously, the machining surface will be damaged and machining will become impossible. In addition, the program controller 4
If the peak voltage of the pulse is as shown in waveform L in FIG. ₂ by signal C from Then the timing pulse is automatically switched to T ₁ '.

Next, a specific example of detection using other pulse conditions will be described. FIG. 5 shows a detection circuit when finishing is performed using a minute pulse current. In FIG. 5, the same parts as in FIGS. 1 and 3 are indicated by the same symbols. Pulses generated from the pulse power source 3 pass through a current limiting resistor, are applied to a capacitor connected in parallel between the electrodes, and a current is accumulated. When a predetermined electrode gap is reached, discharge occurs and machining is performed. The interelectrode voltage is divided into predetermined values by voltage dividers 501 and 502 and applied to one input of the fourth, fifth, sixth, and seventh comparators, respectively. The detection level of the comparator is determined by operating the fifth setting level switching relay 531 in response to the processing material selection signal G from _E4 and the program controller 4, and selecting either the detection level _E5 or _E5 '. Level and E ₆ and E ₇ are given to each other input. If the discharge state is as shown in FIG. 4b, the outputs of the comparators will have waveforms A ₁ , A ₂ , A ₃ and A ₄ . Here, the points where discharge occurs are at each position of V ₁ , V ₂ , V ₃ , and V ₄ in waveform b, and among these, the voltage of V ₄ drops before reaching the predetermined voltage. Therefore, it is in an abnormal discharge state.
Furthermore, at the time point PT ₆ of the timing pulse T ₁ , a short-circuit state occurs as shown in the inter-electrode voltage waveform b. Although there are other non-discharge states, a detection method for normal discharge will be described here. The conditions for a normal discharge are that the voltage accumulated in the capacitor must exceed the detection level E ₃ (or E ₅ ' depending on the material) and that the voltage must not suddenly drop at the time of discharge. is necessary. The output of the first comparator 531 is applied to one input of an OR gate 536, and the output of the second comparator is applied to an input of a one-shot multivibrator 538 and one input of an AND gate 537. When the voltage between the electrodes falls below the detection level E ₅ (or E ₅ ') of the second comparator, a discharge occurs between the electrodes, and the voltage suddenly drops as shown in the waveforms V ₁ , V ₂ ..., the one-shot multi A check pulse width t ₁ shown in waveform MM ₁ is generated from the vibrator 538, and within the time of t ₁ , the detection level of the third comparator 534 is
When E ₆ or less, waveform G ₁ is obtained from the output of AND gate 540. The signal _G1 puts the D-type flip-flop 539 in the set state, and the signal obtained by inverting the timing pulse _T1 generated from the timing pulse generator 551 by the inverter 552 puts it in the reset state, so that the output of the flip-flop has a waveform of _FF3. It becomes like Q. Further, when this output signal is applied to the data input of another D-type flip-flop 538, the output of the flip-flop becomes a waveform FF ₂ Q in synchronization with the timing pulse T ₁ . In other words, V ₁ with normal discharge,
The _three points V ₂ and V are detected one cycle later in synchronization with the timing pulse T ₁ . For example, the output of the normal discharge detection signal FF ₂ Q that occurs between timing pulses PT ₁ and PT ₂ is the output of timing pulses PT ₂ and PT _3.
Appears in the interval. By passing a waveform of the same width as the pulse power source (waveform a in Figure 4) to the AND543, the detection signal generates a signal corresponding to the machining speed corrected by the duty factor of the machining pulse, as shown in waveform d. can get. Abnormal arc discharge can also be obtained from AND gate _G7 using a similar logic circuit, but the explanation of its operation will be omitted. In the above detection, if the signal G generated from the program controller 4 is made of iron, the fifth
The set level of the comparator is set by relay _531.
is selected, and if it is a cemented carbide, E ₅ ' is selected. In the case of normal shape, E ₅ is about 150V,
It is recommended to set the value of E ₅ ′ to 60V. These values can be obtained experimentally, and results have been obtained in which the detected normal discharge and the machining speed correspond exactly one-to-one.

Next, FIG. 6 shows another embodiment, which consists of the normal pulse power supply shown in FIG. 3, the detection signal from the capacitor power supply shown in FIG. 5, and the D signal (capacitor If the power supply is a normal pulse power supply, the detection signal from the normal discharge detection signal output terminal 515 in FIG.
60 and is applied to the optimum control device 6. Although not shown, similar switching can be performed for abnormal arc discharge, short circuit, and no discharge.

Next, another specific embodiment will be described with reference to FIG. 7. FIG. 7 shows the optimum control device 6 in detail. In the figure, 650 is an A/D converter for converting the analog value of the average DC voltage of normal discharge detected by the discharge state detection circuit into a digital value, and the converted digital value is stored in the memory A652. At the same time, it is also applied to the size discriminator 652. On the other hand, 660 indicates a machining fluid pressure control circuit, and the operation circuit 654 is controlled by the operation pulse from the operation pulse generator 653.
The operation signal F, G, H from the program controller 4 causes the reversible counter 656 to sequentially add or subtract pulses within a predetermined range by the operation signal generated from the operation circuit 654 at a predetermined period. D/A the output of the counter
The converter 557 converts it into an analog quantity, and the motor 658 rotates a machining fluid pressure control valve (not shown) to drive it to a predetermined pressure. In the process of manipulating the machining fluid pressure,
A size discriminator 6 determines that the normal discharge is the largest.
52, and the determination signal is sent to memory B655.
The optimal machining fluid pressure at which the normal discharge is maximized during the machining fluid pressure operation is stored, and at the same time as the operation ends, this optimal value is reset in the reversible counter 656 and electrical discharge machining is performed. The above explained the machining fluid pressure, but the machining voltage control circuit 67
0. The same applies to the duty factor control circuit 680 and the electrode lifting cycle control circuit 690, and the order of these operations is as programmed in advance by the control signals F, G, and H of the program controller. , R, S, and U in sequence.

Next, FIG. 8 shows a detailed diagram of the operation circuit 654. In the figure, 654-1 is a memory consisting of an LSI or the like, which uses address designation consisting of inputs _I1 to _I12 and 12 bits of outputs _O1 to _O11 . A signal F is applied from the program controller 4 to inputs I ₁ , I ₂ , and I ₃ , and a signal G is applied to input I ₄ . A program counter A for switching the order of machining fluid pressure P, machining voltage U, duty factor τ, and electrode lifting period T is provided at inputs I ₅ , I ₆ , I ₇ , and I ₈ . ₉ , _I10 , _I11 , and _I12 are provided with program counters B for executing programs such as the operation start value, operation range, and operation step width of the above conditions. Next, the operation of the above circuit is as follows. First, the G signal, that is, the sequential pattern selection signal, and the G signal, that is, the material selection signal, are sent from the program controller 4 to the memory 65.
4 inputs _I1 to _I4 . For example, as shown in Figure 9, the electrode material is copper, the workpiece material is iron,
An ordered pattern is given as I. On the other hand, when an H signal, ie, a reset signal, is applied from program controller 4 to program counters A and B through OR gate 654-8, both counters become operational. A pulse signal with a predetermined period generated from the oscillator 653 is applied to the timer 654-5, and clock signals with different periods are obtained from the output terminals, which are applied to the switch A 654-4 and the memory 654-1. The output of O ₈ ,
A clock pulse having a predetermined periodicity is selected from the switch 654-4 by the search speed switching signal of _O9 , and is inputted to the program counter B as a search signal and counted. Since order pattern I has been selected as described above, the search is first memorized so that the machining fluid pressure is selected, and the output
_{Switcher B654-}
6, the outputs O ₄ , O ₅ , O ₇ corresponding to the initial value of the machining fluid pressure appear at the terminal Q whose signal is indicated by a single line, and the machining fluid pressure shown in FIG. control circuit 660. The initial value of this machining fluid pressure is
Adjustment is made in advance using the D/A converter 557 in FIG. 7 so that the value becomes 0.05 Kg/cm ² . A search signal with a predetermined period generated from the switch A654-4 is applied to the program counter B,
The processing fluid pressure is controlled to vary in steps of approximately 0.1 Kg/cm ² and is operated up to a predetermined range of 0.3 Kg/cm ² as shown in FIG. Next, an output signal is obtained from the memory output O ₁ , and when the signal is given to the program counter A654-2, the counter A becomes 1.
The bit changes and the memory addressing inputs I ₅ , I ₆ , I ₇ , I ₈ accordingly switch to the duty factor S in a predetermined sequence as shown in FIG. At the same time, a reset signal is obtained from output O ₁ , and OR
It is stored in memory to pass through gate 654-8 and reset counter B 654-3. In the example of FIG. 9, the initial value of the duty factor τ ₁ is set to 10%, and the maximum value is set to 90%. Similarly, operations are performed sequentially using predetermined search signals. Hereinafter, in the same manner, the machining voltage U ₁ , the second duty factor τ ₂ , the second machining voltage
Operate U ₂ within the specified range. Depending on the machining shape, for example, as shown in the notes in Figure 9, if the liquid flow method is hole jet, the cycle of the operation signal generated from switch A is stored in memory in advance at 2 second intervals. Just do it. In addition, in order to repeat the above operation, program counter A,
B may be stored in memory so as to be reset sequentially by the output signals O ₁₀ and O ₁₁ of the memory.

As described above, by selecting the operation order pattern from the program controller 4 and selecting the material, each machining condition can be controlled from a predetermined value to a predetermined range by any operation, and the optimum conditions for the machining condition can be optimized. The value is automatically determined by the optimum control device shown in FIG.

Note that when the electrode feed drive is not performed by the circuit 7 but by the NC device 10, the electrode feed amount detection processing device 14 is used as a switching signal of the program controller 4.
Instead of the signal X from the NC device 10, a switching signal may be output. Further, in this case, the output N of the program controller 4 is input to the NC device 10. Processing in which the table X-axis drive circuit 12 and the table Y-axis drive circuit 13 are driven by the NC device 10 to move the electrode and the workpiece relative to each other to continuously and periodically change the gap of any machined surface or part to be machined. A command signal may also be output from the NC device 10 to the program controller 4 during the method.

As described above, the present invention is designed to adjust the machining depth and NC in advance so as to satisfy the desired machining shape and dimensions.
In response to equipment commands, a program controller in which pulse conditions, etc. are programmed, and an optimum control device that automatically controls processing stabilization conditions other than pulse conditions to optimal values are installed.
Since the electrical discharge machine is equipped with a coupling circuit for operating the optimum control device according to switching signals such as pulse conditions generated from the NC device, the present invention improves the efficiency of electrical discharge machining work, and Great effects can be obtained, such as the ability to set processing stability conditions without any skill. In addition, the program controller and optimum control device for stabilizing processing allow automatic setting of conditions, which has great economical effects such as unmanned operation at night.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. Fig. 2 is a discharge waveform diagram, Fig. 3 is a detailed circuit diagram showing a part of Fig. 1, Fig. 4 is a waveform diagram explaining the operation of Fig. 5, and Fig. 5 is another diagram of Fig. 3. FIG. 2 is a circuit diagram showing an example. 6 and 7 are detailed circuit diagrams showing a part of Fig. 1, Fig. 8 is a detailed circuit diagram showing a part of Fig. 7, and Fig. 9 is a detailed circuit diagram showing a part of Fig. 8. FIG. 3 is an explanatory diagram showing stored contents. 1... Electrode, 2... Workpiece, 3... Pulse power supply, 4...
Program controller, 5... discharge state detection circuit, 6... machining stability control circuit, 7... electrode feed drive circuit, 8... machining fluid pressure drive circuit, 513... third setting level switching relay, 514... timing pulse switching relay , 531...Fifth setting level switching relay, 560...Detection switching relay depending on the type of power source, 654...Operation circuit, 654-1...Memory, 6
54-2...Program counter A, 654-3...
Program counter B, 654-4...switcher A,
654-5...Timer.

Claims (1)

[Claims] 1 In electrical discharge machining equipment that processes a workpiece using electrical discharge generated between an electrode and a workpiece, pulse current, pulse width, pulse polarity, and pulse A program control device that controls command signals such as operation pattern selection signals and reset signals for optimal control of power supply type, workpiece material, machining method, and processing stability conditions, and a program control device that controls command signals such as the program control device or NC device. The discharge state detection circuit is equipped with a circuit that switches the detection sensitivity of the discharge state detection circuit to a detection circuit according to the type of machining power supply, and the machining fluid pressure and machining are controlled by the command signal from the program control device or NC device. An operating circuit is installed that repeatedly operates each of the processing stability conditions such as voltage, pulse duty factor, and electrode lifting period from a predetermined value to a predetermined range in a predetermined speed and order, and the optimum value of the processing stability conditions is established. An electric discharge machine characterized by being equipped with an optimal control device that automatically sets the