JP2684918B2 - EDM control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention connects a direct current voltage source and a switching element in series to a machining gap formed between a machining electrode and a workpiece, and Discharge in which a pulse voltage is applied to the machining gap by controlling the switching element
The present invention relates to improvement of a processing control device . 2. Description of the Related Art Conventionally, in electric discharge machining, machining has been performed by passing a rectangular pulse current, but recently, for example, disclosed in Japanese Patent Application Laid-Open No. 49-118097 proposed by the present applicant. As described above, a method of improving machining characteristics by a pulse current having a special shape such as a pulse current other than a rectangular pulse current, for example, a triangular pulse current, has been performed. In this case, a method as shown in FIG. 10 is used to obtain the specially shaped pulse current. That is, the switching elements 70a, 70b, 70c,.
, 70n are supplied to the respective bases by the control circuit 71 in a time-shifted manner, and the switching elements 70a, 70b, 70c,... , 70n, and the processing electrode 2 through the switching elements 70a, 70b, 70c,..., 70n and the collector resistors 72a, 72b, 72c,. This is a method in which the workpiece 3 is processed by flowing into a processing gap formed by the workpiece 3. In addition, 73 is a pause time setting circuit, 74 is a flip-flop, 75 is a switching element for applying a machining gap voltage,
76 and 77 are a base resistance and a collector resistance of the switching element 75, 78 is a discharge occurrence detecting device, and 79 is a clock pulse generating circuit. The operation of the device shown in FIG. 10 will be described. First, when a signal indicating the end of the rest time is output from the rest time setting circuit 73, the signal passes through the signal line A and enters the flip-flop 74. The switching element 75 is made conductive via the base resistor 76 of the switching element 75 .
As a result, a voltage is applied to the machining gap formed by the machining electrode 2 and the workpiece 3, and after a certain delay time, a transition is made to discharge. Here, the point when the transition to the discharge is detected by the discharge occurrence detecting device 78, and an impulse signal is sent to the flip-flop 74 via the signal line B to shut off the switching element 75. On the other hand, at the time of the transition to the discharge, the discharge generation detecting device 78 uses the signal line C to output the clock pulse generation circuit 7.
9 is sent to the control circuit 71, and the switching elements 70a, 70b, 7
, 70n are successively shifted in time to conduct. Here, the switching elements 70a, 70b, 70
, 70n are turned on, the DC voltage source 1 causes the switching elements 70a, 70b, 70c,.
0n, collector resistances 72a, 72b, 72c,.
A pulse current of a special shape flows through the processing gap through 72n. Next, the operation principle of the device shown in FIG.
1 will be described. Here, FIG. 11A shows a pause clock pulse, FIG. 11B shows a machining gap voltage waveform, and FIG.
11C shows the discharge detection impulse signal, FIG. 11D shows the conduction time of the switching element 75, FIG. 11E shows the discharge time clock pulse, and FIG. 11F shows the discharge current waveform.
Here, when the pause time clock pulse shown in FIG. 11A reaches a predetermined number, the switching element 75 is turned on as shown in FIG. 11D and the switching element 75 is turned on as shown in FIG. After the delay time, discharge occurs in the machining gap.
Due to this discharge, an impulse signal shown in FIG. 11C is generated, and the clock pulse generating circuit 79 shown in FIG. 10 is driven to generate a clock pulse as shown in FIG. 11E. Due to the generation of the clock pulse, the switching element 75 is cut off as apparent from FIG. Also,
When the clock pulse shown in FIG. 11E is generated, the switching elements 70a, 70
The discharge currents having waveforms as shown in FIG. 11 (f) are caused to flow through the machining gap at 0b, 70c,... [0006] As described above, the conventional apparatus connects in parallel a switching circuit equal to a step current value applied to a processing gap formed between a processing electrode and a workpiece. However, when the step current value is controlled to near the maximum value of the machining current, the number of switching circuits connected in parallel increases, and accordingly, a large number of switching elements are required. In particular, when it is desired to finely control the step current value (for example, in units of 0.5 A), the number of switching circuits connected in parallel and the number of switching elements are increased. The present invention has been made in view of the above problems, and the number of parallel connections of switching circuits and the number of switching elements are increased even when the step current is controlled close to the maximum value of the machining current and finely. It is an object of the present invention to provide an electric discharge machining control device that does not require the operation. The electric discharge machining control device according to the first invention is connected in series with a DC voltage source to a machining gap formed between a machining electrode and a workpiece. A switching circuit and a current supply means for supplying a current having a maximum value preset to the machining gap via the switching circuit, the switching circuit supplying a weighted current. And a plurality of switching circuits connected in parallel with each other,
The plurality of controls the switching circuit to change the combination of switching circuits which conducts during the duration of the discharge current pulse to be supplied to the machining gap, switches the plurality of
At least two switching circuits in a switching circuit
And a pulse shaping means for obtaining a discharge current pulse which has a desired initial current value and which increases stepwise with the passage of time. The electric discharge machining control device according to the second invention is an additional device.
Directly into the machining gap formed between the work electrode and the workpiece.
A switching circuit connected in series with a current source,
The maximum value is preset in the machining gap via the switching circuit.
Discharge with current supply means for supplying a set current
A processing control device, wherein the switching circuit is weighted
A plurality of parallel connected current sources
It is composed of a switching circuit.
The discharge electric power supplied to the machining gap by controlling the ching circuit
Set of switching circuits that conduct during the duration of a current pulse
By changing the matching and having a desired initial current value,
The discharge current pattern increases stepwise with the passage of time.
In an electric discharge machining control device equipped with pulse shaping means to obtain
In the above, a means provided with a means for changing the machining current of a desired initial current value in accordance with the maximum value of the preset maximum current supplied between the machining electrode and the workpiece Is. When a workpiece is machined by the electric discharge machining control device constructed as in the first and second inventions , a machining gap formed between the machining electrode and the workpiece is formed. By appropriately combining a plurality of switching circuits connected in parallel with each other for supplying a weighted current, the switching circuits are made conductive during the duration of the discharge current pulse, and a discharge current pulse having a predetermined shape is obtained. EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG.
1 shows an embodiment of the present invention, in which 1 is a DC voltage source set to a predetermined voltage V, 2 is a machining electrode connected to the positive electrode of the DC voltage source 1, and 3 is an electrode driving device 4. The workpiece 3 is subjected to electrical discharge machining by the provided machining electrode 2, and the workpiece 3 includes resistors R0 to R6 and a switching element S.
It is connected to the negative electrode of the DC voltage source 1 via a series body of 0 to S6. The switching element S0 is 1A, the switching element S1 is 0.5A, and the switching element S2 is 1A.
A, switching element S3 is 2A, switching element S
4 is 4A, the switching element S5 is 8A, and the switching element S6 is 16A. That is, the switching elements S0 to S6
Switching circuit 2 by the circuit in which each of
0-26 are configured, and the switching circuits 20-26
Are weighted. Reference numeral 6 is a step number comparison output circuit, and output terminals P0 to P6 turn on switching elements S0 to S6.
Or drive to OFF. The number of steps is between input terminals N0
Input a binary value to N5. A step period output circuit 5 outputs a step period pulse signal ST to a step number comparison output circuit 6. The step cycle is the input terminals T0 to T6
And outputs a reset signal LD indicating the start of the step operation. An oscillation circuit 7 outputs a pulse signal PS, a clock signal CK of 10 MHz, and a discharge detection signal DS between the machining electrode 2 and the workpiece 3. FIG. 2 is a circuit diagram showing details of the step cycle output circuit 5 in FIG. In FIG. 2, 9 is 7
A bit binary counter, 8 is a comparator for determining the magnitude of the binary value T0 to T6 of the step period and the output Q0 to Q6 of the binary counter 9, 10a to 10d are D flip-flops, and 11a to 11b are AND gates. , 12 is a 2-input N
AND gate, 13 is an inverter, 14 is a 3-input NAN
D gate. FIG. 3 is a circuit diagram showing details of the step number comparison output circuit 6 in FIG. In FIG. 3, 16
Is a 6-bit binary counter, 15 is the binary number N0 to N5 of the step number and the output Q0 to Q5 of the binary counter 16.
The comparator 17 determines the magnitude of the signal, 17 is a 3-input AND gate,
18a to 18g are switching element drivers.
The binary value of the number of steps (hereinafter referred to as a binary set step number) N0 to N5 is a binary integer value obtained by dividing 1A from the set value of the electric discharge machining current by 0.5A. . Next, the operation of the apparatus of the above embodiment will be described with reference to FIGS. 1 to 3 and 4 to 6. In FIG. 1, the peak current of the switching elements S0 to S6 is:
It is determined by the ratio between the resistors R0 to R6 and the machining voltage E obtained by subtracting the voltage between the discharge electrodes from the voltage V of the DC voltage source 1. These peak currents are 1 when the switching element S0 is turned on.
A, when the switching element S1 is turned on at the same time as the switching element S0, it becomes 1.5A, and thus increases by being turned on and off by the switching elements S0 to S6. In addition, O of the above-mentioned switching elements S0 to S6
N and OFF are the output P0 of the step number comparison output circuit 6.
To P6. Hereinafter, the output P of the step number comparison output circuit 6
An example of 0 to P6 will be described with reference to FIGS. In FIG. 2, PS is at logic 1H while a voltage is applied to the machining gap with a pulse signal. When discharge occurs in the machining gap and current starts flowing, the machining current signal DS becomes logic 1H. At this time, the logic 1H is latched in the D flip-flop 10C by the clock signal CK, and the initial reset signal L
D is output from the 3-input NAND gate 14. Thereafter, the binary counter 9 is loaded with the initial value 0, counted by a signal obtained by dividing the clock CK by 、, and the count data appears on the outputs Q0 to Q6 of the binary counter 9. 2
Data Q0 to Q6 of the binary counter 9 and the step cycle 2
When the binary data T0 to T6 are compared by the magnitude comparator 8 and the output data of the binary counter 9 becomes equal to or larger than the step period binary data, 0A ≦ B output of the magnitude comparator 8 becomes logic 1H. 0A> B output becomes logic 0L. As a result, the step period pulse ST becomes 2-
The binary counter 9 is loaded with 0 simultaneously with the output from the input NAND gate 12. This situation is shown in the time chart of FIG. The clock CK is 10MHz,
The step cycle binary data is 2, T0 = 0, T1 =
1, T2 = 0, T3 = 0, T4 = 0, T5 = 0, T6 =
In the case of 0, the step period pulse ST is 0.4 μS
Outputs periodically. The step period pulse ST is sent to a step number comparison output circuit 6 shown in detail in FIG.
In FIG. 3, PS is a pulse signal which controls the switching element drivers 18a to 18g and outputs a switch signal P0. LD and ST are signals from the step cycle output circuit 5, which are an initial reset pulse and a step cycle pulse, respectively. Binary counter 16
After 0 is loaded by the initial reset pulse LD,
It is counted up by the step cycle pulse ST.
The count-up number of the binary counter 16 is determined by the outputs Q0 to Q5 of the binary counter 16 and the binary setting step number N0.
Controlled by the output 0A> B of the magnitude comparator 15 that compares N5, the output data of the binary counter 16 becomes equal to or larger than the binary set step number data.
The operation of the binary counter 16 is stopped by closing the input AND gate 17. Switching element drivers 18b-18
The input to g is the output Q0 to Q5 of the binary counter and outputs to the switch signals P1 to P6. The time chart of FIG. 5 shows that N0 = 0, N1 = 1, N2
= 1, N3 = 0, N4 = 0, N5 = 0. The processing current flows by 1 A in the pulse signal PS, and then increases by 0.5 A as the counting proceeds. The seventh ST pulse is not counted. By the way, in the electric discharge machining control apparatus according to the first embodiment, the initial electric current value of the electric discharge machining current is shown in FIG.
As shown in the figure, the peak current value of the first step is set to a fixed constant value of 1 A, and the subsequent steps are increased in steps of 0.5 A. For this reason, when the set value of the electric discharge machining current is large, when controlling the step current value to near its maximum value, a considerable number of switching circuits and switching elements are required, and this has been further improved. Is Example 2. Example 2. Next, a second embodiment of the present invention will be described. 7 is a circuit diagram showing a step number comparison output circuit 6 in the second embodiment of the present invention, FIG. 8 shows an ideal waveform of an electric discharge machining current in the second embodiment of the present invention, and FIG. FIG. 8B is a waveform diagram when the number is 7 or less, FIG. 8B is a waveform diagram when the number of binary setting steps is 8 or more, and FIG. 9 is a diagram showing an actual waveform of the electric discharge machining current according to the second embodiment of the present invention. Is. In FIG. 7, the same symbols as those in FIG. 3 indicate the same parts, and 19 is a 3-input OR gate, which outputs a logic 1H when the binary value N0 to N5 of the step number is 8 or more. Logic 0L is output in the following cases. Of the binary input data D0 to D5 of the 6-bit binary counter 16, D0 is connected to logic 1H, and D1 is connected to the output of the OR gate 19. D2 to D5 are connected to logic 0L. In this embodiment, the circuit configuration of the step number comparison output circuit 6 shown in FIG. 7 is different from that shown in FIG. 3, but the overall configuration of the apparatus is the same as that of FIG. The circuit configuration of 5 is the same as that of the device shown in FIG. Next, the operation of the apparatus shown in the second embodiment will be described. In FIG. 7, PS controls the switching element drivers 18a to 18g with a pulse signal and outputs a switch signal P0. LD and ST are signals from the step cycle output circuit 5, which are an initial reset pulse and a step cycle pulse, respectively. 2
When the binary set step number N0 to N5 is 7 or less, that is, when the set value of the electric discharge machining current is 4.5 A or less, 1 is set to 2 by the initial reset pulse LD.
When the number of steps to set the advance is 8 or more, that is, when the set value of the electric discharge machining current is 5 A or more, 3 is loaded into D0 to D5, and then the step cycle pulse ST counts up. The count-up number of the binary counter 16 is the output 0 of the magnitude comparator 15 which compares the outputs Q0 to Q5 of the binary counter 16 with the binary setting step numbers N0 to N5.
Limited by A> B, the output data of binary counter 16 is 2
When it becomes equal to or larger than the number of steps set data, the 3-input AND gate 17 is closed and the operation of the binary counter 16 is stopped. The input to the switching element drivers 18b-18g is the output Q of the binary counter.
Switch signals P1 to P6 are output at 0 to Q5. As a result, the waveform of the electric discharge machining current is as shown in FIG. 8A or 8B in the ideal case where there is no floating capacitance between the machining electrode 2 and the workpiece 3. In addition, even when there is a floating capacitance between the machining electrode 2 and the workpiece 3, the peak current of the first step of the electric discharge machining current is increased as shown in FIG. As described above, according to the first invention, a switching circuit connected in series with a DC voltage source is provided in a machining gap formed between a machining electrode and a workpiece. In an electric discharge machining control device comprising a current supply means for supplying a current having a maximum value preset to the machining gap via the switching circuit, the switching circuits are connected in parallel to each other to supply a weighted current. And a plurality of switching circuits that are turned on to control the plurality of switching circuits and change the combination of the switching circuits that conduct during the duration of the discharge current pulse supplied to the machining gap . Small in switching circuit
Superimpose currents flowing through two switching circuits at least
The discharge current pulse has a desired initial current value, and the discharge current pulse increases stepwise with the passage of time. It is possible to provide an electric discharge machining control device that does not need to increase the number of switching circuits connected in parallel and the number of switching elements even when performing fine control of the step current value close to the maximum value of the machining current during the period. , In addition, the elapsed time and increase
By controlling the amount of steps
Emission with the advantage that the pulse shape can be formed into any shape
An electric processing control device can be provided . Also, multiple switches
Flow to at least two switching circuits in the switching circuit.
By superimposing the current that is generated,
The switching element to be inserted has a low current capacity and
An electric discharge machining control device with the advantage of obtaining the peak current value is proposed.
Can be provided. According to the second invention, a processing electrode and
In the machining gap formed between the workpiece and the DC voltage source
A switching circuit connected in series and the above switch
The maximum value has been preset in the machining gap via the
Electric discharge machining control device having current supply means for supplying current
And the switching circuit is weighted
Multiple switches connected in parallel to supply current
And a plurality of switching circuits described above.
Control of the discharge current pulse supplied to the machining gap.
Change the combination of switching circuits that conduct during the duration.
And has a desired initial current value and the passage of time
A discharge current pulse that increases stepwise with
In electric discharge machining control apparatus comprising a pulse forming means, the upper
Since the maximum value supplied between the machining electrode and the work piece is provided with a means for changing the machining current having a desired initial current value according to the maximum value of the preset current, Even when the set value of the electric discharge machining current supplied between the electrode and the workpiece is large and the step current value is controlled close to its maximum value, the number of switching circuits and switching elements is increased. It is possible to provide an electric discharge machining control device that does not require operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an example of an electric discharge machining control apparatus according to a first embodiment of the present invention. FIG. 2 is a circuit diagram showing details of a step cycle output circuit shown in FIG. FIG. 3 is a circuit diagram showing details of a step number comparison output circuit shown in FIG. FIG. 4 is a time chart of the operation of the step cycle output circuit shown in FIG. 5 is a time chart of the operation of the step number comparison output circuit shown in FIG. FIG. 6 is a diagram showing an ideal waveform of an electric discharge machining current in the electric discharge machining control device according to the first embodiment of the present invention. FIG. 7 is a circuit diagram showing a step number comparison output circuit according to a second embodiment of the present invention. FIG. 8 is an ideal waveform diagram of an electric discharge machining current according to the second embodiment of the present invention. FIG. 9 is a waveform diagram showing an actual waveform of an electric discharge machining current according to a second embodiment of the present invention. FIG. 10 is a configuration diagram showing a conventional electric discharge machining control device. FIG. 11 is a diagram illustrating an operation principle of a conventional electric discharge machining control device. [Description of Signs] 1 DC power supply 2 Processing electrode 3 Workpiece 4 Electrode driving device 5 Step period output circuit 6 Step number comparison output circuit 7 Oscillator circuits S0 to S6 Switch elements R0 to R6 Current limiting resistors

Claims (1)

(57) [Claims] In the machining gap formed between the machining electrode and the workpiece, a switching circuit connected in series with a DC voltage source, and a current whose maximum value is preset in the machining gap via the switching circuit is applied. In an electric discharge machining control device including a current supply means for supplying, the switching circuit comprises a plurality of switching circuits connected in parallel to supply a weighted current, and further controls the plurality of switching circuits. Te by changing the combination of switching circuits which conducts during the duration of the discharge current pulse to be supplied to the machining gap, the plurality of switches ing
Flow through at least two switching circuits in the circuit
An electric discharge machining control apparatus comprising pulse forming means for superimposing currents, having a desired initial current value, and obtaining a discharge current pulse that increases stepwise with the passage of time. 2. Machining gap formed between machining electrode and workpiece
A switching circuit connected in series with a DC voltage source
And the machining gap is maximal via the switching circuit.
A current supply means for supplying a current whose value is preset.
The electric discharge machining control device, wherein the switching circuit
Are connected in parallel with each other to provide a weighted current
It consists of multiple switching circuits, and
It is supplied to the machining gap by controlling the switching circuit of
Switching conducted for the duration of the discharge current pulse
Have a desired initial current value by changing the combination of circuits
Along with the passage of time, the release increases stepwise.
Electric discharge machining control equipped with pulse shaping means for obtaining electric current pulses
In control device, according to the maximum value of the current maximum value is set in advance to be supplied between the machining electrode and the workpiece, comprising means for varying the machining current of desired initial current value Characterized by
A discharge machining controller.