JPS59115123A - Wire cut electric discharge machining device - Google Patents

Abstract

PURPOSE:To carry out electric discharge machining with high accuracy and high efficiency by providing a means of continuously applying voltage, in addition to the intermittent discharge voltage, to a place between a workpiece and a wire electrode. CONSTITUTION:The machining power supply circuit of a wire-cut electric discharge machining device consists of an auxiliary power supply 12 connected between the circuit and a terminal which is connected to a workpiece, a diode 13 being connected with the polarity as shown in the figure, etc. This power supply 12 is connected to a DC power supply 7 in such a way that the same polarity sides are connected to each other. Also, the voltage of the power supply 12 is set lower than that of the power supply 7. Due to such construction, the voltage applied to a place between the workpiece and the wire electrode during the process of machining is a voltage, in which the pulse voltage provided at certain intervals from the DC power supply 7 is overlapped with a constant continuous voltage from the auxiliary power supply 12. Thereby electric discharge machining can be performed with high accuracy and high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire-cut electric discharge machining apparatus that performs machining such as cutting on a workpiece by intermittently generating electrical discharge between a wire and a workpiece. , the wire is placed opposite the workpiece placed on the table at a minute interval, one end of the machining power source is brought into contact with the wire, and the other end is connected to the workpiece, and the wire is connected to the workpiece. This is a device that cuts a workpiece into an arbitrary shape by generating electrical discharge at predetermined intervals.

FIG. 1 is an electrical circuit diagram of a conventional wire-cut electric discharge machining apparatus.

In the figure, 1 is a workpiece fixed on a numerically controlled table, 2 is a wire electrode facing the workpiece 1 with a minute interval, 3 is a wire reel around which the wire electrode 2 is wound, and 4 is a wire electrode. A wire take-up reel for winding the wire electrode 2; 5, a guy 7 of the wire electrode 2; a DC power supply; 8, a switching element that connects the voltage of the DC power supply 7 on and off at a predetermined cycle; 10 is a current limiting resistor that limits the current flowing through the switching element. Reference numeral 11 denotes a current-carrying terminal that connects one terminal of the machining power source 6 and the wire electrode 2, and the other terminal of the machining power source 6 is connected to the workpiece 1. A machining fluid such as water or oil is filled between the workpiece 1 and the wire electrode 2 to remove machining debris.

The switching element 8 is turned on at predetermined intervals by the pulse power supply 9.
When the switching element 8 is turned OFF, a discharge occurs between the workpiece 1 and the wire electrode 2, and the workpiece 1 is thereby cut. The wire electrode 2 that has undergone discharge is sequentially wound onto a wire take-up reel 4.

By moving the table, the workpiece 1 is cut into an arbitrary shape.

In such a conventional wire-cut electrical discharge machining device, the wire electrode 2 is supposed to be stretched straight between the guides P and 25 during electrical discharge machining, but it is damaged by discharge force, machining fluid pressure, etc. 2. When the wire electrode 2 is deformed into an arcuate shape in the direction of being pulled away from the workpiece l, the cut surface of the workpiece l also becomes an arcuate shape.2. Particularly, when cutting a complicated shape, the accuracy of a portion of the corner decreases, making high-precision machining impossible. In addition, in conventional wire-cut electric discharge machining equipment, in order to improve the machining speed, a method was often adopted to vibrate the wire electrode 2 to smoothly disperse the discharge points. Since fc is a means of mechanical vibration, it has the disadvantage of being extremely complex and expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wire-cut electric discharge machining apparatus that can perform machining with high precision and high efficiency, while eliminating the above-mentioned conventional drawbacks.

In order to achieve this object, the present invention is characterized in that a voltage applying means is provided between the workpiece and the wire electrode for continuously applying a voltage in addition to the intermittent discharge voltage.

The present invention will be described below based on the illustrated embodiments. FIG. 2 is a circuit diagram of a machining power source of a wire-cut electric discharge machining apparatus according to an embodiment of the present invention. In FIG. 2, parts that are the same as those shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. 12 is an auxiliary power supply connected between a terminal connected to the workpiece 1 and a terminal connected to the wire electrode 2, and 13 is a diode connected with the polarity shown. Auxiliary power supply 12
The connection is such that the sides of the same polarity as the DC power supply 7 are connected to each other. Further, the voltage of the auxiliary power supply 12 is set to a voltage lower than the voltage of the DC power supply 7. With such a configuration, during machining, the voltage applied between the workpiece l and the wire electrode 2 is composed of a pulse voltage at predetermined intervals from the DC power source 7 and a continuous constant voltage from the auxiliary power source 12. The voltage will match.

Figure 3 shows such a voltage waveform between the workpiece 1 and the wire electrode 2, where the horizontal axis represents time T and the vertical axis represents voltage E.
It's great. Period T. n is the period during which the switching element 8 is in a conductive state by the pulse power source 9, and this period T
. At step n, a voltage -EO of the DC power supply 7 is applied between the workpiece 1 and the wire electrode 2. Period T. ff is a period during which the switching element 8 is in a non-conductive state by the pulse power source 9; this period is T. In ff, the voltage -Eo of the DC power supply 7 is not applied between the workpiece 1 and the wire electrode 2, and only the voltage -El of the auxiliary power supply 12 is applied. Period T. Electric discharge machining is performed at n.

Here, if the average voltage 't' applied between the workpiece 1 and the wire electrode 2 is 't' ElLV, then the following equation is obtained. By the way, in normal wire cut electrical discharge machining, the period T. n
is 1 to 5 μS, while the period Toff is several hundred
μS to several tens of m5. Therefore, the period T. n is the period T. Since it is an almost negligible value for ff,
The average voltage E&V is EhV=]EI. That is, during the machining period, the workpiece 1 and the wire electrode 2
The voltage applied between the two is approximately equal to the voltage of the auxiliary power supply 12.

As is well known, the Coulomb force acting between objects is a function of the distance and voltage between them, so in this case,
The Coulomb force acting between the workpiece 1 and the wire electrode 2 is
The gap between the two and the average voltage, that is, the auxiliary power supply 12
is a function of the voltage −El, l) (fc, and the dielectric constant of the machining fluid is constant). As a result, the Coulomb force acting between the two can be controlled by the voltage of the auxiliary power supply 12. Since the direction in which this Coulomb force acts is opposite to the direction in which the aforementioned discharge force acts, the auxiliary power supply 12
By applying this voltage between the workpiece 1 and the wire electrode 2, it is possible to prevent the wire electrode 2 from deforming into an arched shape due to the discharge force.

FIG. 4 is a circuit diagram showing a specific example of the auxiliary power supply shown in FIG. 2. 12a is a variable voltage power supply, and 12b is a diode connected in series thereto. In this way, the auxiliary power supply 12
By making the voltage variable, the Coulomb force acting between the workpiece l and the wire electrode 2 can be adjusted in accordance with the discharge force.

Here, to give a specific example, the voltage E of the DC power supply 7.

30Off), and the voltage E1 of the auxiliary power supply 12 is
When changing between 50 (V) and 200 (V),
The difference in the amount of displacement of the center portion of the wire electrode 2 in normal wire-cut electrical discharge machining ranges from several μm to several tens of μm.

That is, the voltage of the auxiliary power supply 12 is set to 50 (V) to 200 (V).
+7) Range A: Variable IC: The amount of deformation of the layer electrode 2 can be controlled within the range of several μm to several tens of μm.

In this way, in this example, an auxiliary power source was provided separately from the DC power source, and a voltage was continuously applied between the workpiece, the wire electrode, and □, so that the Coulomb force acting between them was reduced. It is possible to prevent deformation of the wire electrode by generating it, and to perform highly accurate processing.

FIG. 5 is a circuit diagram of a machining power source of a wire-cut electric discharge machining apparatus according to another embodiment of the present invention. In the figure, the same parts KI/i as the parts shown in FIG. 2 are given the same reference numerals, and the explanation will be omitted. 14 is an auxiliary power source of this embodiment. The auxiliary power supply 14 includes a variable voltage power supply 14a, a diode 14b, and a counter 1.
It is composed of a 4c2 arithmetic processing unit 14d. Now, if we consider the discharge force from the DC power supply 7, the discharge force acts as a force to separate the wire electrode 2 from the workpiece 1 as described above, and if we look at this force on average, it is the discharge repetition frequency, that is, Period T shown in FIG. It is a function of the discharge energy at n. Since the discharge energy is within a fixed value depending on the voltage of the DC power source 7, etc., the discharge power can be obtained by detecting the discharge repetition frequency and performing a predetermined calculation. In this embodiment, the discharge repetition frequency is measured by the counter 14.
c, and based on the value, the arithmetic processing unit 14d
The discharge power is calculated by Further, the processing unit 14d calculates a Coulomb force (a force in the opposite direction to the discharge force) that is equal to the obtained discharge force, and calculates an average machining voltage for obtaining the obtained Coulomb force. In this way, if the variable voltage power source 14a is controlled based on the voltage determined by the arithmetic processing unit [14d] so as to generate a voltage equal to this voltage, deformation of the wire electrode 2 due to the discharge force can be completely prevented. I can do it.

In this example, since the discharge force, Coulomb force, and average machining voltage are determined accurately, even more precise machining can be performed, and in particular, the accuracy of corner machining of the workpiece can be significantly improved. I can do it.

FIG. 6 is a circuit diagram of a machining power source of a wire-cut electric discharge machining apparatus according to another embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 2 are given the same reference numerals, and explanations thereof will be omitted.

Reference numeral 15 is an auxiliary power supply of this embodiment, which is a variable voltage power supply 15a.
It is composed of one diode 15b and one function generator 15c. A signal with a predetermined frequency is output from the function generator 15c, and the variable voltage power supply 15a is controlled at a frequency corresponding to this signal.
change the voltage. As a result, the auxiliary power supply 15 outputs a DC voltage in which an alternating current voltage is superimposed on a voltage at a constant level. Many means are known as means for generating such a DC voltage, and an appropriate one can be selected and used from these means.

In the above specific example, the voltage of the DC power supply 7 is 300 (V).
In this case, the output voltage of the auxiliary power supply 15 is set to an amplitude of 7, for example.
If the voltage is changed by alternating current at a predetermined frequency of 5 (V), the central portion of the wire electrode 2 will be repeatedly displaced in accordance with the predetermined frequency by a displacement amount of several tens of micrometers. That is, the wire electrode 2 vibrates, and as a result, the discharge points are dispersed smoothly, making it possible to increase the machining speed during rough machining.Thus, in this embodiment, the output voltage of the auxiliary power source is Since the alternating current component is superimposed on the direct current voltage, the present invention does not have the same effect as the previous embodiment, and it is possible to further improve the processing efficiency.

In each of the above embodiments, the auxiliary n-source variable voltage power supply is independent, but an existing DC power supply may also be used.

As described above, in the present invention, since a continuous voltage is applied between the workpiece and the wire electrode in addition to the intermittent discharge voltage, high accuracy and high efficiency can be achieved. Can be processed.

[Brief explanation of drawings]

Fig. 81 is an electric circuit diagram of a conventional wire-cut electric discharge machining device, Fig. 2 is a circuit diagram of a machining power source of a wire-cut electric discharge machining device according to an embodiment of the present invention, and Fig. 3 is a diagram showing the electrical circuit diagram between a workpiece and a wire electrode. 4 is a circuit diagram showing a specific example of the auxiliary power supply shown in FIG. 2, and FIGS. 5 and 6 are wire-cut electrical discharge machining apparatuses according to other embodiments of the present invention, respectively. FIG. 2 is a circuit diagram of a processing power source. l... Workpiece, 2... Group wire electrode, 6...
...Processing power supply, 7. Old... DC power supply, 8...
...Switching element, 9...Pulse source, 1
2.14.15... Group/auxiliary power supply. Figure 1 Figure 2 Figure 4 Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] (1) A wire that generates an electrical discharge between the wire and the workpiece, and a power source that intermittently applies a discharge voltage between the wire and the workpiece. . A wire-cut electric discharge machining apparatus, characterized in that a voltage applying means for continuously applying a voltage in addition to the discharge voltage between the wire and the workpiece. (2. In claim 1, the voltage applying means has a device for making the applied voltage variable. (3) In claim 1, . A wire-cut electrical discharge machining apparatus, wherein the voltage applying means includes a device that periodically varies the applied voltage.