JPS61209819A - Wire cut electric discharge machine - Google Patents

Abstract

PURPOSE:To know the diameter of a wire electrode, electrifying condition of electrifying parts, and feeding condition of a machining fluid by feeding a measuring current between said two electrifying parts to which different pulse power source parts for electric discharge machining pulses are connected respectively. CONSTITUTION:A first electrifying part 14 and a second electrifying part 15 are provided up and down across a workpiece 12, and first and second machining-pulse power sources 16, 17 are provided for the electrifying parts 14, 15 respectively. A detecting part 40 has a DC power source 41 the positive pole of which is connected to the electrifying part 14, while its negative pole is connected to the electrifying part 15 via a resistor 42 which serves as a detecting signal generator, and a measuring current Is flows in this loop. Since currents I1, I2 for electric discharge machining are mutually offset at the electrifying parts 14 and 15, any component of these electric discharge machining currents will not flow into the detecting part 40.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wire-cut electrical discharge machining apparatus.

(Prior Art) A conventional wire-cut electrical discharge machining device has a plurality of current-carrying parts such as current-carrying rollers arranged in the path of a wire electrode, and the wire electrode is connected to a single machining pulse generating part via these current-carrying parts. The structure is electrically connected to one of the output terminals, and the other output terminal is connected to the workpiece, whereby a machining pulse voltage is applied to the electrical discharge machining gap between the shear wire electrode and the workpiece. It becomes. In a wire-cut electric discharge machining device configured in this way, the electrical contact between the current-carrying roller and the wire electrode changes due to wear and tear of the current-carrying roller, and the diameter of the wire electrode varies. These are factors that cause the magnitude of the current flowing through the wire electrode to vary. By the way, in order to increase the machining speed of wire-cut electrical discharge machining equipment, it is necessary to increase the machining current flowing through the wire electrode into the machining gap, but for the above reasons, it is necessary to increase the machining current flowing into the machining gap through the wire electrode. In addition to the resistance value fluctuating when
The upper limit value of the machining current that can be passed through the wire electrode and the upper limit value of the frequency of the machining pulse are constantly changing.

Therefore, the voltage value generated between the current-carrying part and the workpiece and the value of the machining current flowing through the machining gap are measured, and based on these measurement results, the machining current applied from the machining pulse generating part to the machining gap is determined. By controlling the peak value etc. of
A wire-cut electric discharge machining device is used that is capable of applying a machining current as large as possible to a machining gap at a repetition period as short as possible within a range that does not cause the wire electrode to cut.

(Problem to be solved by the invention) However, when controlling the machining current for the above purpose in a wire-cut electrical discharge machining device, it is necessary to accurately detect the state of the resistance value when looking from the current-carrying part to the wire electrode side. However, with the conventional configuration described above, it is only possible to detect a preliminary state that takes into account the machining gap and the resistance value of the workpiece in addition to the resistance of each current-carrying part and wire electrode. The problem is that precise control cannot be performed.

Therefore, it is an object of the present invention to provide a wire-cut electric discharge machining apparatus in which the wire electrode can be seen from the current-carrying part and the state of the resistance value can be detected with high accuracy.

Another object of the present invention is to provide a wire-cut electrical discharge machining device that can accurately control the state of machining current supplied to a machining gap according to the electrical state between a wire electrode and a current-carrying part. There is a particular thing.

(Means for Solving the Problems) The configuration of the first invention for achieving the above object has a plurality of current-carrying parts that are in electrical contact with the wire electrode, and the wire electrode and the wire electrode are connected to each other through the current-carrying parts. In a wire-cut electrical discharge machining device configured to supply electrical discharge machining energy to the electrical discharge machining gap between the workpiece and the workpiece, the electrical discharge machining energy is separately supplied to the electrical discharge machining via the plurality of current-carrying parts. At least two electrical discharge machining nozzle power supply units for supplying power to the gap, and connected to any two current-carrying units.
A measurement power supply that supplies a measurement current to a wire electrode between two current-carrying parts, and a detection signal generating means provided between the measurement power supply and the current-carrying part to extract a detection signal corresponding to the magnitude of the measurement current. It is characterized by the following.

In a second invention, in the configuration of the first invention, each discharge is configured such that the machining pulse supplied to the machining gap is in a required optimum state in response to the detection signal from the detection signal generating means. The machining nozzle power supply unit is controlled.

(Function) The energy for electrical discharge machining output from the plurality of Noculus power supply units for electrical discharge machining is applied to the electrical discharge machining gap through the corresponding current-carrying parts and wire electrodes.
The current supplied from the pulse power supply does not flow to the measurement power supply connected between the two current-carrying parts. Then, the measurement current supplied from the measurement power supply returns to the measurement power supply via one current-carrying section, the wire electrode, and the other current-carrying section. Therefore, the detection signal generating means can detect only the magnitude of the measured current in G, and based on the detection signal obtained in this way, the diameter of the wire electrode, the energization state of each current-carrying part, the machining gap It is possible to know the supply status of the machining fluid being supplied to the machine.

As mentioned above, the detection signal indicates the resistance state when looking at the wire electrode side from the current-carrying part, and according to this detection signal, each discharge is Control of the machining/4' Lux power supply is performed with high precision.

(Example) Hereinafter, the present invention will be explained in detail with reference to the illustrated embodiments.

FIG. 1 shows a schematic configuration diagram of an embodiment of a wire-cut electric discharge machining apparatus according to the present invention.

The wire-cut electrical discharge machining apparatus 1 includes a wire around which a wire electrode 2 is wound, a wire 3, and a pair of rows 24°5. It has a wire feed mechanism 6 for feeding out the wire electrode 2 from the bin 3, and the wire electrode 2 fed out from the wire pickpocket 3 is guided by a wire guide 7.8 to a wire take-up rowia 9. .Feeded between 10 and taken up? It is configured to be wound up by a bottle 11. Since the above-described feeding and winding mechanism for the wire electrode 2 is well known,
Here, detailed illustration of the mechanism is omitted.

The workpiece 12 is placed approximately in the middle of the wire guide 7.8.
, a processing table 13 for moving in the Y direction is arranged, and the processing table 13 can be moved within the X-Y plane by a drive motor (not shown). . Then, the wire electrode 2 and the workpiece 12
By moving the workpiece 12 relative to the wire electrode 2, which is being fed out at a predetermined speed, while applying electric discharge machining pulses as described later between the The workpiece 12 is subjected to electrical discharge machining into a desired shape. Note that machining fluid 61 is supplied from a nozzle 60 to one machining gap.

In this device 1, a first energizing part 14 and a second energizing part 15 are provided above and below with the workpiece 12 in between. A/4-rus power supplies 16 and 17 for second processing are provided.

The first Noculus power supply 16 for processing has a Noculus pulse generator 18 that outputs a repetition/4' pulse signal Pt (see FIG. 2(, )) having a predetermined on time and off time,
The dulse signal PK is applied to each pace of two switching transistors 19 and 20 arranged in parallel.

The emitters of the switching transistors 19 and 200 are commonly connected to the workpiece 12 via the output current regulator 30, and the collectors of the switching transistors 19 and 20 are each connected to a corresponding current limiting resistor. 21.
22 to the positive electrode of a DC power supply 23, respectively.

The negative electrode of the DC power supply 23 is connected to the first current-carrying part 1'4 that is in electrical contact with the wire electrode 2, and the switching transistors 19 and 20 are activated in response to the pulse signal P10 becoming high level. is turned on,
The wire electrode 2 and the workpiece 12 are connected to each other via the first current-carrying section 14.
An electrical discharge machining current T, whose peak value is limited by the resistors 21 and 22 and the output current regulator 30, is applied to the electrical discharge machining gap between the (see C)) flows into the electrical discharge machining gap via the first current-carrying portion 14.

The second machining pulse power source 17 has the same configuration as the first machining Noculus power supply 18, and has a Noculus generator 24 that outputs the Noculus signal P3 shown in FIG. 2(b). Norrus signal P! Switching transistor 25.26
is controlled on and off, and the switching transistor 25
．． A current limiting resistor 27 connected to the collector of 26
．． 28 and an output current regulator 31 connected to the emitter, the discharge machining current Is (second
(see figure (d)) is from the DC power supply 29 to the second energizing section 15.
Flows into the electrical discharge machining gap through. Therefore, in the discharge machining gap, there is a machining current that is a composite current of the discharge machining current 11.11! (See Figure 2 (-)) will flow.

This apparatus 1 includes two machining power supplies 16. which are configured to extract independent electrical discharge machining energy.
The values of resistors 21, 22 and 27, 28 in each machining/main power supply 16, 17 are determined such that each machining/power source 17 carries 172 of the desired electrical discharge machining energy. Due to the electric discharge machining state 11+13 outputted from the machining system power supplies 16 and 17, each voltage drop component occurring in the wire electrode 2 and the corresponding current-carrying portion 14.15 is canceled out between the two current-carrying portions 14.15. It will be done.

In order to output a detection signal indicating the resistance state of the wire electrode 2 when viewed from the current-carrying part 14.15, the current-carrying part 14.
15 is provided with a detection section 40. The detection unit 40 is
It has a DC power supply 41 whose positive pole is connected to the current carrying part 14, and the negative pole of the DC power supply 41 is connected to the current carrying part 15 via a resistor 42 which functions as a detection signal generator. Therefore, the positive electrode of the DC power supply 41 is connected to the current-carrying part 14 and the wire electrode 2.
, is connected to its negative electrode via the current-carrying section 15 and the resistor 41, and the measured current ! ■ flows. As already explained, the electric discharge machining current ■1t11 is
Since these electrical discharge machining current components are canceled out between the current-carrying parts 14 and 15, these electric discharge machining current components do not flow into the detection part 40.

Measuring current! Level 3 is the contact resistance R1 between the current-carrying part 14 and the wire electrode 2, the contact resistance R2 between the current-carrying part 15 and the wire electrode 2, the resistance R3 of the wire electrode 2 between the current-carrying parts 14 and 15, and the resistance. It is determined by the resistance R4 of the device 42 and the voltage E of the DC power supply 41.

That is, the value of the measurement current ■3 is as follows, and the resistor 42 outputs the detection voltage ■1 of a level corresponding to the level of the above-mentioned measurement current.

The state of change in the level of the detection voltage (1) will be explained with reference to FIGS. 3(a) to 3(d). Machining current flowing through the machining gap! When the level of changes as shown in FIG. , the change in resistance value is the machining current! The shape almost corresponds to the waveform of , but at the rising time of the machining current , the rising time of the machining current is t&.

t, Yoshi also causes a predetermined time delay tl. This time t1
is caused by the heat capacity of the wire electrode 2. For example, electric current! If the value of increases for some reason, the wire electrode 2 becomes overheated, and as a result, the resistance R3 increases and the depth of the valley at the level of the detection voltage v1 becomes deeper as shown by the dotted line.

Furthermore, when the discharge stops at times tb, ta, . . . and the value of the electric current becomes zero, the temperature of the wire electrode 2 gradually decreases, so that the resistance R3 also gradually decreases. The rate of decrease at this time depends on the supply state of the machining fluid 60. That is, if the machining and supply conditions of the liquid 41 are good, the wire electrode 2 will be cooled quickly, the resistance R4 will also decrease rapidly as shown in FIG. 3(b), and the level of the detection voltage v1 will also decrease. Time t6-ta,...
It rises rapidly immediately after. If the supply state of the machining fluid 41 is poor, the wire electrode 2 will not be cooled properly, and therefore the rate of decrease in the resistance Rs after time t will be small, as shown by the dashed line in FIG. 3(d). ni, tb
From then on, it will slowly rise. Therefore, in such a case, it is sufficient to increase the hydraulic pressure of the machining fluid 41 and improve the supply state of the machining fluid 41. Furthermore, if the diameter of the wire electrode 2 becomes thin, it will cause the wire electrode 2 to overheat. As the steady state level LV, decreases, changes in the diameter of the wire electrode 2 can be monitored by monitoring the level LV.

Note that the value of the resistor 11sR1 also changes depending on the magnitude of the machining current I (see FIG. 3(, )), but the change in the resistance Ra is small.

Therefore, if the detected voltage v1 is observed using an oscilloscope or the like, the processing state can be clearly understood.

The wire-cut electric discharge machining apparatus l shown in FIG.
A control loop f50 is provided to control the pulse power supplies 16 and 17 and to keep the electric discharge machining state in a proper state at all times. This control roof '50 has a detection circuit 51 that detects desired information in response to the detection voltage v1, and in this detection circuit 51, the wire electrode 2 is heated by the detection voltage v1 valley level LVI and the processing current. After the detection voltage V is released, the level of the detection voltage V becomes the predetermined steady level LV.
, (see FIG. 3(d)) is detected in the time it takes to return to .

The signal S1 indicating the level LVI is output from the output current regulator 30.3.
1, whereby the level of the machining current 11+11 is automatically adjusted so as to obtain the maximum machining current level within limits without overheating the wire electrode 2.

On the other hand, the signal S indicating the time T is generated by the pulse generator 18.2.
4, and the processing/main system pulse width is controlled so that the off time of the pulse P1ePH does not become shorter than the time T. As a result, the next heating pulse is output before the wire electrode 2 is sufficiently cooled, thereby preventing the wire electrode 2 from being overheated. And based on the time T? The period of cis is controlled to be shortened to a state on the verge of overheating of the wire electrode 2, thereby making it possible to significantly improve processing efficiency.

As a result, it is possible to reliably prevent the wire electrode 2 from breaking due to overheating, and the processing efficiency can be significantly increased. Alternatively, the hydraulic pressure of the machining fluid 61 may be controlled so that the time T remains constant during machining.

(Effects) According to the present invention, as described above, the machining state of the wire-cut electrical discharge machining device can be grasped extremely accurately, so that the machining state can be accurately improved and various adjustments can be made smoothly. This can significantly improve processing efficiency.

In addition, if the configuration is such that each state of the processing pulse is automatically adjusted in response to a signal indicating the processing state, it is possible to maximize the ability of the wire electrode and perform extremely efficient processing. This provides excellent effects such as being able to reliably prevent disconnection of the wire electrode.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a wire-cut electric discharge machining apparatus according to the present invention, FIG. FIG. 2 is a waveform diagram showing signal waveforms of each part of the device shown in FIG. 1;

Claims (2)

[Claims] (1) It has a plurality of current-carrying parts that are in electrical contact with the wire electrode, and energy for electrical discharge machining is supplied to the discharge machining gap between the wire electrode and the workpiece through these current-carrying parts. A wire-cut electrical discharge machining apparatus configured with at least two electrical discharge machining pulse power supply units for separately applying electrical discharge machining energy to the electrical discharge machining gap via the plurality of current-carrying units, and any two electrical discharge machining pulse power supply units. A measuring power source connected to the current carrying part and supplying a measuring current to a wire electrode between these two current carrying parts, and a detection signal generating means for extracting a detection signal according to the magnitude of the measuring current. Characteristic wire cut electrical discharge machining equipment. (2) It has a plurality of current-carrying parts that are in electrical contact with the wire electrode, and energy for electrical discharge machining is supplied to the discharge machining gap between the wire electrode and the workpiece through these current-carrying parts. A wire-cut electrical discharge machining apparatus configured with at least two electrical discharge machining pulse power supply units for separately applying electrical discharge machining energy to the electrical discharge machining gap via the plurality of current-carrying units, and any two electrical discharge machining pulse power supply units. a measurement power source connected to the current carrying part and supplying a measuring current to a wire electrode between these two current carrying parts; a detection signal generating means for extracting a detection signal according to the magnitude of the measurement current; A wire-cut electric discharge machining apparatus comprising: means for controlling the electric discharge machining pulse power supply section so as to control the state of the machining pulses supplied to the electric discharge machining gap to an optimum state in response.