JPH04354621A - Electric discharge machining gap control circuit - Google Patents

Abstract

PURPOSE:To prevent the disconnection of a wire electrode due to the uncertain elements such as the dispersion of the electric discharge of a working liquid and the vibration of a wire and increase the speed of electric discharge machining, by controlling the pulse width and repose time of the applied voltage pulse in correspondence to the generated electric discharge state. CONSTITUTION:An electric power source circuit consisting of dc power sources 8 and 9, transistors 10 and 11, and resistors 12 and 13 is connected between a wire electrode 15 and a workpiece 14, and the electric discharge for electric discharge machining is generated by switching the transistors 10 and 11 by two gate signals outputted by a pulse generating circuit 1 and preamplifiers 2 and 3. The first pulse between two outputted pulses of the pulse generating circuit 1 is utilized for confirming the normalcy of the electric discharge. The normal electric discharge state is detected by a comparator 5 and a differential circuit 6, and the short circuit state is detected by a comparator 4 and an AND gate 7, and the pseude between-electrode short circuit state similar to the short circuit state is detected by a counter 8 and a data comparison circuit 19. The width and repose time of the pulse voltage for electric discharge are controlled in correspondence with each state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical discharge machining control circuit, and more particularly to an electrical discharge machining control circuit for controlling an electrical discharge machining gap in wire electrical discharge machining in which a workpiece is electrically machined using a wire electrode.

0002

[Prior Art] Conventionally, this type of electrical discharge machining gap control has been performed to determine normal discharge when the electrical discharge machining gap formed by the wire electrode and the workpiece is discharged in a desired state, and when the wire electrode and the workpiece are electrically discharged. By distinguishing between a short-circuited state and a short-circuited state in which current is applied, and by controlling the magnitude of the voltage pulse applied to the machining gap and its pause time depending on the normal discharge and short-circuited states, the short-circuited state can be detected. This prevents the wire electrode from breaking.

0003

[Problem to be Solved by the Invention] In wire electrical discharge machining, wire electrode breakage generally occurs based on the relationship between the electrical discharge machining current and the machining gap length between the wire electrode and the workpiece. Discharge when the gap length is abnormally small has a large effect on wire electrode breakage.

Conventional electric discharge machining gap control only controls machining pulses during normal discharge and short circuit conditions, and does not control machining pulses in regions where the machining gap length is relatively small. There is a drawback that the wire electrode breaks frequently.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric discharge machining control device which eliminates the above-mentioned drawbacks and can significantly reduce the frequency of wire electrode breakage in areas where the machining gap length is relatively short and which is close to a short-circuit condition. .

[0006]

[Means for Solving the Problems] The electric discharge machining gap control circuit of the present invention provides an intermittent voltage pulse in the electric discharge machining gap between a machining electrode made of a wire electrode and a workpiece subjected to electric discharge machining by this machining electrode. An electric discharge machining gap control circuit that performs control to suppress the influence of fluctuations in the length of the electric discharge machining gap when performing electric discharge machining by applying a Is it in a state?
Alternatively, it is configured to include means for determining whether the wire electrode is in a pseudo short-circuit state that is very close to a short-circuit state, and controlling the pulse width and pause time of the voltage pulse to suppress disconnection of the wire electrode.

Further, the electrical discharge machining gap control circuit of the present invention applies a first voltage pulse to determine whether or not the electrical discharge machining gap is in a normal state, and if it is in a normal electrical discharge state, a predetermined pulse width is applied. Electrical discharge machining is performed by applying a second voltage pulse while taking a predetermined rest time, and when the normal discharge state is not established, the pulse width and rest time of the second voltage pulse are set such that the wire electrode does not become disconnected. It has a configuration that controls.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

The configuration of the embodiment shown in FIG. 1 includes a pulse generating circuit 1 that receives input data from the outside and sends out pulse source signals of a first voltage pulse and a second voltage pulse for electric discharge machining, and Preamplifiers 2 and 3 that set the second voltage pulse source signals to predetermined levels, DC power supplies 8 and 9, transistors 10 and 11 switched by the outputs of preamplifiers 2 and 3, and switched transistors 10 and 11. Resistors 12 and 13 that control the conduction current of Resistors 16 and 17, a comparator 5 and a differentiating circuit 6 that input a simulated interpole signal to determine a normal discharge state, a comparator 4 and an AND gate 7 that determine a short circuit state, and a pseudo interpole short circuit that is close to a short circuit state. A counter 18 and a data comparison circuit 19 are provided.

Next, the operation of this embodiment will be explained.

The positive electrode sides of the DC power supplies 8 and 9 are connected to a workpiece 14 via transistors 10 and 11 as switching elements and resistors 12 and 13 that limit the machining current, respectively. Further, the negative electrode sides of the DC power supplies 8 and 9 are connected to the wire electrode 15. Therefore, transistor 10,1
By turning on and off the gate signals VS1 and VS2 of 1, intermittent voltage pulses can be applied to the discharge machining gap. The simulated inter-electrode signal VGL is obtained by dividing the inter-electrode voltage using resistors 16 and 17.

The comparator 5 and the differentiator circuit 6 are circuits that detect the start of discharge after applying the first voltage pulse to the discharge machining gap, and the comparator 5 compares the simulated gap signal VGL with a predetermined threshold value VD. and its output is logic “1”
The discharge start signal DIS-P is obtained through the differentiating circuit 6 which outputs a pulse only when the value changes from "0" to "0".

The comparator 4 also outputs a simulated gap signal VGL and a predetermined threshold value VS for determining whether or not a voltage pulse is applied to the discharge machining gap when the discharge machining gap is extremely narrow, that is, in a short circuit state. A short-circuit signal S-P is obtained by comparing the two. The interpole short circuit signal SP and the discharge start signal DIS-P are supplied to the pulse generating circuit 1.

Input data P-DAT of pulse generation circuit 1
A is the pulse width of the machining current, depending on the purpose of various machining.
The rest time etc. are given by the upper central processing unit.

The first voltage pulse source signal VSC1 and the second voltage pulse source signal VSC2 output from the pulse generating circuit 1
is a pulse source signal that turns on and off the transistors 10 and 11, is amplified through the preamplifiers 2 and 3, and is input to the transistors 10 and 11.

The pulse generating circuit 1 first sends out a first voltage pulse source signal VSC1 to apply a first voltage pulse for the purpose of determining whether or not the electrical discharge machining gap is in a short-circuited state. The current generated by this first voltage pulse is generally set to be small. After that, when a normal discharge occurs in the discharge machining gap, that is, a discharge that is not in a short-circuit state, a second pulse of a predetermined pulse width is activated by the discharge start signal DIS-P described above.
Apply a voltage pulse of .

When the second voltage pulse is turned off, the first voltage pulse is also turned off. The off state of the first and second voltage pulses lasts for a predetermined pause time in order to deionize the electrical discharge machining gap. Thereafter, the workpiece 14 is machined while applying the first voltage pulse and repeating the operation.

However, in a short-circuit condition, the first
Even if a voltage pulse of By performing an AND operation at the gate 7, a short-circuit signal SP is generated. The short circuit detection pulse SP is output from the pulse generation circuit 1 after a predetermined delay time after the first voltage pulse is turned on.

Further, the counter 18 counts the search time from the application of the first voltage pulse until the start of discharge, and based on this count, determines whether or not a short-circuit condition is near. Yes, first voltage pulse source signal VS
Counting is started with a count start signal CST at the same timing as C1, and stopped with a discharge start signal DIS-P.

The data comparison circuit 19 uses the search time SE-TIME of the output data of the counter 18 and the search data SE-DATA set in advance from the host CPU.
When SE-TIME is smaller than SE-DATA, a pseudo short-circuit signal GN-P indicating a minimum gap state, although not a complete discharge state, is generated and is notified to the pulse generation circuit 1.

FIG. 2 is a time chart showing the operation of each part in FIG. 1, and shows the timing of generation of main signals during normal discharge, short circuit state, and pseudo short circuit in discharge state with an extremely small gap. .

In the normal discharge state, after the first voltage pulse source signal VSC1 is turned on, the simulated electrode gap signal VG
L rises to a predetermined voltage, discharge starts after a predetermined time, and as described above, the second voltage pulse is applied for a preset pulse width T-ON, and then for a predetermined rest time T-OFF. It's on hiatus.

[0024] In the short-circuit state, the pulse width of the second voltage pulse is T-ON x1, and the pause time is T-OFF x2.
and override each.

[0025] In the state of pseudo-electrode short circuit, the degree of influence of wire breakage is considered to be between the two states described above, so the pulse width of the second voltage pulse is set to T-ON·y1. , and the pause time is T-OFF・y2
In this way, the load conditions on the wire electrode 15 are significantly relaxed, and the pulse width and rest time of the discharge pulse voltage are controlled to eliminate uncertain factors such as variations in the discharge of machining fluid and wire vibration in electrical discharge machining using the wire electrode. This significantly reduces the possibility of wire electrode breakage.

[0026]

[Effects of the Invention] As explained above, the present invention enables the discharge machining to be carried out by applying a pulse voltage using a wire electrode. The pulse width of the applied voltage pulse is determined by determining whether the condition is a short circuit in which the workpiece is in contact with the workpiece, or a pseudo short circuit condition in which the discharge machining gap is extremely narrow although it is not a short circuit condition, and the pulse width of the applied voltage pulse is adjusted depending on each condition. By controlling the time and rest time, the possibility of wire breakage of the wire electrode is significantly reduced due to uncertain factors such as variations in the discharge of the machining fluid and wire vibration, and stable and high-speed electrical discharge machining can be performed. effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a time chart of main signals in the embodiment of FIG. 1;

[Explanation of symbols]

1 Pulse generation circuit 2, 3 Preamplifier 4, 5 Comparator 6 Differential circuit 7 AND gate 8, 9 DC power supply 10, 11 Transistor 12, 13, 16, 17 Resistor 14 Workpiece 15 Wire electrode 18 Counter 19 Data comparison circuit

Claims (2)

[Claims] 1. When electrical discharge machining is performed by applying intermittent voltage pulses to the electrical discharge machining gap between a machining electrode made of a wire electrode and a workpiece to be subjected to electrical discharge machining by this machining electrode, An electrical discharge machining gap control circuit that controls to suppress the influence of variation in gap length, the electrical discharge machining gap being in a normal discharge state, in a short circuit state, or in a pseudo-electrode gap extremely close to a short circuit state. An electrical discharge machining gap control circuit comprising means for determining whether a short circuit exists and controlling the pulse width and rest time of the voltage pulse to suppress disconnection of the wire electrode. 2. A first voltage pulse is applied to determine whether or not the discharge machining gap is in a normal state, and if the discharge machining gap is in a normal discharge state, a second voltage pulse of a predetermined pulse width is applied to a predetermined pause. A claim characterized in that electric discharge machining is performed by applying the voltage over time, and when the electric discharge is not in a normal electric discharge state, the pulse width and pause time of the second voltage pulse are controlled so as not to break the wire electrode. The electric discharge machining gap control circuit according to item 1.