KR20020064534A - Vibration control apparatus for electrode of wire-cut discharge machine using electro-rheological fluid - Google Patents

Abstract

PURPOSE: An apparatus for controlling vibration of electrodes in a wire cut electric discharging machine is provided which is capable of improving straightness of a machined surface of a workpiece by controlling uneven vibration of a wire using electrorheological fluid. CONSTITUTION: A wire guide(4) makes a wire(2) has an even straightness. A reel(18) for transferring a wire(2) provides tensile force to the wire(2). A servomechanism is controlled by a CNC system(8). A detector(14) for checking a vibration of the wire(2) during cutting of a workpiece(7), of which detected signal is amplified by an amplifier(15). A voltage amplifier(16) applies a high voltage to a controller(17) for controlling the electrorheological fluid. When the wire is released by a motor(10) from a reel(1) for supplying the wire, the wire(2) is guided by a reel(18) for transferring the wire(2) and the wire guide(4) to cut the work piece(7), which is finally wound around a winding reel(11).

Description

VIBRATION CONTROL APPARATUS FOR ELECTRODE OF WIRE-CUT DISCHARGE MACHINE USING ELECTRO-RHEOLOGICAL FLUID}

The present invention relates to an electrode vibration control apparatus for a novel wire cut discharger employing an electrofluid fluid, which is one of smart materials.

In general, a wire cut discharger is a kind of machine tool that cuts a workpiece by discharge while a wire having a diameter of 0.05 mm-0.33 mm is continuously transferred.

1 is a schematic diagram showing a general wire cut discharger, in which the wire 2 wound on the wire delivery reel 1 is released, cutting the work piece 7 placed on the transfer table 5, and winding the wire continuously. It is a structure wound around the reel 11, the transfer reel (3a) (10a) is provided to give a tensile force to the wire 2, the wire guide 4 for maintaining the straightness of the wire (2) is installed do.

In addition, the transfer table 5 is moved in the front, rear, left and right directions by the X-axis servomotor 6 and the Y-axis servomotor 9, and the X-axis servomotor 6 and the Y-axis servomotor 9 Numerical control device (CNC SYSTEM) (8) is provided.

Reference numeral 12 is a discharge device.

At this time, a winding motor is installed on the winding reel 11 and the transfer reel 10a to wind the wire 2 while pulling.

The wire cut discharger having such a structure can maintain a considerable accuracy, but vibration occurs in the wire 2 during machining, and the vibration causes the straightness of the cutting surface of the work piece 7 to be bent.

That is, as shown in FIGS. 2A and 2B, a gap S is generated between the wire 2 and the cut surface of the work piece 7 due to the vibration of the wire 2, thereby damaging the straightness of the cut face of the work piece 7. There is a problem that must be post-processed by grinding, such as after cutting the wire.

The main causes of wire vibration are wire transfer speed, wire diameter size, discharge repulsion force generated during processing, and the flow rate and flow rate when the processing liquid is discharged. In order to solve this problem, a research on a method of controlling and moving a wire tension has been conducted. A study for controlling tension by a speed numerical control device using a DC motor as an actuator by Phu Hwang Jung Woong of Japan and others. Was first released in 1990. In addition, Japan's FANUC, the world's largest manufacturer of wire cut dischargers, measures the load of the wire transfer motor 10 pulling the wire 2 and checks the number of revolutions as shown in FIG. A tension control device for the wire 2 was used in which the electromagnetic brake 3 was controlled to the set value.

Reference numeral 13 denotes a power control device of the electromagnetic brake 3.

However, this system does not adapt to irregular external factors due to changes in wire diameter size, discharge repulsion force and processing liquid discharge, and maintains constant tension value at all times and does not allow real time control. .

Accordingly, there is a need for an apparatus capable of controlling the vibration change of the wire generated in accordance with the magnitude of the vibration of the wire during the wire cut discharge operation.

Therefore, the present invention devised a braking device using a new type of electrofluid fluid capable of real-time control after measuring the vibration of the wire to control the irregular vibration of the wire to improve the straightness of the machined surface of the workpiece It is an object of the present invention to provide an apparatus for controlling vibration of electrodes of a discharger.

In order to achieve the above object, the present invention provides a wire cut discharge device, which detects vibration of a wire cutting a workpiece, and applies a voltage to the electrofluid fluid braking device filled with the electrofluid fluid according to the detected signal. An electrode vibration control apparatus for a wire cut discharger, characterized in that the electrofluid fluid braking device operates to control the amplitude of the wire in real time.

1 is a schematic diagram of a typical wire cut discharger.

2A and 2B are cross-sectional and longitudinal cross-sectional views showing wire vibration and workpiece cut surfaces;

3 is a device configuration diagram of a conventional wire cut discharger.

4 is a device configuration diagram of a wire cut discharger to which the present invention is applied.

5 is a cross-sectional view showing the configuration of the electrofluid fluid braking apparatus of the present invention.

Figure 6a illustrates the structure of the particles when no electric field is applied to the electrofluid fluid.

Figure 6b shows the structure of the particles upon application of an electric field to the electrofluidic fluid.

<Explanation of symbols for the main parts of the drawings>

1: wire delivery reel 2: wire

3: electromagnetic brake 3a: feed reel

4: wire guide 5: feed table

6: X axis servomotor 7: Workpiece

8: Numerical Control System (CNC SYSTEM) 9: Y-axis Servo Motor

10: wire feed motor 10a: feed reel

11 wire wound reel 12 discharge device

13: electronic brake power control device 14: vibration detector

15 amplifier 16 voltage amplifier

17: electrofluid braking device 17a: fixture

17b: ball bearing 17c: insulating rubber

17d: outer diameter electrode 17e: column

17f: packing 17g: packing

17h: Ball bearing 17i: Nut for bearing

17j: Washer for bearing nut 17k: Electric fluid

17l: (+) terminal 17m: (-) terminal

17p: internal diameter electrode 18: transfer reel

19: Particles dispersed in a non-conductive solvent of the electrofluid fluid

Hereinafter, with reference to the accompanying drawings, the electrode vibration control device of the wire cut discharger using the electric fluid fluid of the present invention will be described in detail.

The present invention is a novel system for applying a braking device operated by an electro-Rheological fluid, which is a smart material, to the wire vibration control of a wire cut discharger, which is characterized by an electric field. It is possible to change the braking force of the system only by changing the strength, and real-time continuous control is possible with fast response speed of several milliseconds (ms). In addition, the mechanically simple structure enables the device to be simplified.

Meanwhile, electro-rheological fluid is a colloidal solution in which strong conductive particles are dispersed in a non-conductive solvent. The electro-rheological fluid generally refers to a fluid whose mechanical properties such as yield shear stress and viscosity vary depending on the size of the electric field being loaded. In addition, the reaction rate of the electrofluid fluid is very fast, such as several milliseconds, and shows a continuous and reversible response to the electric field load.

In general, the electrofluid fluid has a characteristic that the yield shear stress of the fluid increases with increasing electric field, and its behavior is very complicated, but it is known to have a Bingham behavior which can be expressed by the following equation.

here Represents the shear stress of the fluid Is the shear rate ratio Represents the viscosity of the fluid. Represents the yield stress of a fluid, With increase of It is known to increase in relation to. Wow Is a characteristic value according to the compositional conditions of the electrofluid fluid, such as the type and viscosity of the solvent used in the preparation of the electrofluid fluid, the kind and weight ratio of the conductive particles, the water content of the particles, and the temperature of the fluid, and can be obtained by experiments. .

As shown in FIG. 6A, the electrofluid fluid has an isotropic mechanical property due to free movement of the particles 19 dispersed in a non-conductive solvent as shown in FIG. 6A, and characteristics of the Newtonian fluid. However, at the time of electric field load (FIG. 6b), the dispersed conductive particles are charged to have an anisotropic physical and mechanical property which forms a chain structure that is bonded to each other toward the electrode. As such, the chain-like structure of the particles formed in the electric field direction under electric field load may limit the flow of the fluid by providing resistance to the shear force applied from the outside by the binding force of the particles.

4 is a block diagram showing the wire cut discharger of the present invention, wherein the structure of the wire cut discharger of the present invention has a mechanism for transferring the wire 2, i.e., the wire delivery reel 1, as in the prior art. , A wire wound reel 11 and a wire transfer motor 10 are installed, a transfer reel 18 for imparting tensile force to the wire 2, and a wire guide for maintaining the straightness of the wire 2 ( 4) is installed.

In addition, a servo mechanism for transferring the transfer table 5, a numerical control device (CNC SYSTEM) 8 for controlling the servo mechanism, and a discharge device are provided, similarly to a general wire cut discharger.

In the present invention, in addition to the existing tension control device is provided with a vibration detector 14 for detecting the vibration of the wire (2) for cutting the workpiece (7), the signal detected by the vibration detector 14 An amplifier 15 for amplifying is provided, and the numerical control device 8 receives the signal amplified by the amplifier 15 and comprises a voltage amplifier 16 for supplying a high voltage to the electrofluid braking device 17. .

The wire 2 is a wire winding reel 11 which is rotated after the new wire is released from the wire delivery reel 1 by the rotational force of the wire transfer motor 10 and the workpiece 7 is cut by the discharge phenomenon in the middle. It is continuously wound on, the specific transport path of the wire (2) is as follows.

When the wire is released from the wire delivery reel 1, the workpiece 7 is cut through the feed reel 18, passed through the wire guide 4, and subjected to tension by the wire feeding motor 10, and finally, the wire wound reel. It is wound around (11).

During the processing, the vibration detector 14 detects the amplitude of the wire 2 and transmits it to the numerical controller 8 through the amplifier 15, and analyzes it to supply a high voltage to the result controlled by the control algorithm ( 16) to control the electrofluid braking device (17).

Discharge machining occurs repeatedly on and off several times per second, and the wire gets vibration force by discharge force during discharge. In order to control this, a reaction speed of several milliseconds (ms) is required, and the developed brake is difficult to use due to the problem of reaction speed due to the configuration of the machine and mechanism. Therefore, we proposed a control device that uses electrofluid fluid, which is a fluid whose mechanical properties such as yield shear stress and viscosity change according to the size of the electric field being loaded. The reaction rate of the electrofluid fluid is very fast, such as several milliseconds (ms), and the present invention is most suitable for the vibration control of the wire because it exhibits a continuous and reversible response to the electric field load.

The electrofluid braking device 17 has a cylindrical shape as shown in FIG. 4 and is installed to be external to the transfer reel 18 so as to apply tension to the wire 2 when the wire 2 is transferred. The structure thereof will be described in detail with reference to the accompanying drawings.

As shown in FIG. 5, the electrofluid braking device 17 has a structure in which an electrofluid fluid 17k is filled between two electrode cylinders composed of an inner diameter electrode 17p and an outer diameter electrode 17d, The inner diameter electrode is connected to the (+) terminal 17l and the outer diameter electrode is connected to the (-) terminal 17m.

The inner diameter electrode 17p and the outer diameter electrode 17d must be insulated, and the outer diameter electrode 17d is coated with an insulating rubber 17c so as not to be energized with the wire 2.

The outer diameter electrode 17d is installed to be rotated in the conveying direction when the wire 2 is conveyed, and smoothly polishes the inner surface to reduce the discharge phenomenon. The inner diameter electrode 17p is coupled to the fixture 17a to be attached to the apparatus body.

At this time, the fixture 17a is made of an insulating material so that high voltage electricity does not flow to the apparatus main body.

As such, while the inner diameter electrode 17p is fixed, the outer diameter electrode 17d must be rotated and must be completely insulated from the inner diameter electrode 17p so as not to discharge the high voltage applied to the electric fluid 17k.

In the drawings, reference numerals 17b and 17h are ball bearings installed between the inner diameter electrode 17p and the outer diameter electrode 17d, 17e is a column, 17f and 17g are packings, 17i is a bearing nut, and 17j is a bearing nut. It is a dragon washer.

The ball bearings 17b and 17h are preferably made of a good conductive material, and the column 17e should be made of a nonconductive material.

When the positive and negative voltages of thousands of volts are applied to the inner diameter electrode 17p and the outer diameter electrode 17d of the electrofluid fluid braking device 17 having such a configuration, the electrofluid fluid 17k is caused to increase the electric field. Accordingly, as shown in FIG. 6B, the yield shear stress of the fluid is increased to generate a repulsive force for the rotation of the outer diameter electrode 17d, thereby performing braking. This braking force causes the outer diameter electrode 17d to act as a brake.

Therefore, when a repulsive force is generated with respect to the rotation of the outer diameter electrode 17d as described above, the braking force for the transfer of the wire 2 is generated when the outer diameter electrode 17d and the transfer reel 18 are bitten and rotated. By adjusting the tension of (2) it is possible to adjust the amplitude of the wire (2). As such, the electrofluid braking device 17 generates the desired braking force by the applied electric field, thereby actively damping the vibration of the wire 2.

The electrode vibration control device of the wire cut discharger of the present invention measures the vibration of the wire (2) to control the magnitude of the voltage in accordance with the measured value and supply the voltage to the electrofluidic fluid braking device (17) 2) is a feedback system to control the amplitude.

As described above, the present invention devised a braking device using an electrofluid fluid capable of real-time control after measuring the vibration of the wire, thereby controlling the irregular vibration of the wire, thereby improving the processing surface straightness of the workpiece. have.

Claims (6)

In the wire cut discharger, Install a vibration detector to detect the vibration of the wire cutting the workpiece, and install an electrofluid fluid braking device filled with the electrofluid fluid to apply tension to the conveyed wire when voltage is applied according to the detected vibration width. Electrode vibration control device of the wire cut discharge, characterized in that for controlling the amplitude of the. 2. The apparatus of claim 1, wherein the electrofluid fluid control device comprises a cylindrical inner diameter electrode, a tubular outer diameter electrode rotatably installed outside the inner diameter electrode, an electrofluid fluid filled between the inner diameter electrode and the outer diameter electrode, and (+) (-) Terminals connected to the inner diameter electrode and the outer diameter electrode, respectively, and an insulating rubber coated on the outer surface of the outer diameter electrode, and applying a voltage to the inner diameter electrode and the outer diameter electrode for the rotation of the outer diameter electrode Electrode vibration control device of the wire-cut discharge, characterized in that braking is made by the reaction force. In a wire cut discharger having a structure in which a wire wound on a wire feeding reel cuts a workpiece placed on a transfer table and is continuously wound on a wire winding reel, a vibration detector for detecting a vibration of the wire, and the vibration detector A numerical control device that amplifies the signal, a voltage amplifier that generates a high voltage by receiving the signal output from the numerical control device, and an electric fluid fluid that applies tension to the wire to which the high voltage generated by the voltage amplifier is applied and operated. Electrode vibration control device of a wire cut discharge, characterized in that comprising a control device. 4. The apparatus of claim 3, wherein the electrofluid fluid control device comprises a cylindrical inner diameter electrode, an outer diameter electrode rotatably installed outside the inner diameter electrode, an electrofluid fluid filled between the inner diameter electrode and the outer diameter electrode, and the inner diameter. (+) (-) Terminals connected to the electrode and the outer diameter electrode, respectively, and comprising an insulating rubber coated on the outer surface of the outer diameter electrode, and installed so that the wire is surrounded on the outer surface according to the signal detected by the vibration detector When the high voltage is applied to the electrode and the outer diameter of the electrode vibration control device of the wire cut discharge, characterized in that the braking is generated by the repulsive force for the rotation of the outer diameter electrode. The apparatus of claim 4, wherein the inner diameter electrode is coupled to a fixture fixed to the apparatus body. 6. The apparatus of claim 5, wherein the fixture is an insulating material.