JPH0425095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing vibration of a wire electrode in wire cut electrical discharge machining.

In wire cut electric discharge machining, the wire electrode at the machining section between a pair of positioning guides placed at a distance is placed opposite the workpiece, and the machining liquid is transferred between the wire electrode and the workpiece while continuously feeding in the axial direction of the wire electrode. Machining is performed by intermittent electric discharge via a wire electrode, and the wire electrode must be used in a state where it is as straight as possible, stretched taut with a predetermined tension, and with little vibration. However, when performing wire cut electrical discharge machining, the axial update feed while the wire electrode is in contact with the guide, etc.
Due to the pulsed discharge during electric discharge machining, or due to irregularities in the machining fluid jet or changes in the path at corners of the machining contour shape, etc., the wire electrode at the machining section between the pair of positioning guides vibrates with both guides as fulcrums at both ends. As a result, there is a drawback that overcutting of the machined portion of the workpiece, that is, the width of the cutting groove becomes large or changes locally, resulting in a decrease in processing accuracy.

In consideration of this point, in the present invention, a pair or a plurality of contact bodies preferably made of a low-friction material made of graphite, various composite materials, alloys containing low-friction materials, etc. are used to forcibly connect the wire electrodes. The device is designed to limit vibration by contacting the wire electrode in a pinch-like manner, and at least one of the contact members is a movable body to prevent the generation of vibration and absorb the generated vibration. or to prevent it.

Next, the present invention will be explained based on the drawings illustrating the invention. FIG. 1 schematically shows a wire cut electric discharge machining apparatus equipped with a vibration prevention device according to the present invention, in which an upper arm 103 and a lower arm 104 extend from a column 102 provided on a bed 101 to a bed 101 on which a workpiece described later is installed. The upper arm 103 extends toward the upper table, and supports a head 105 that can move up and down at the distal end of the upper arm 103. A guide holder 106 is supported at the lower part of the head 105 so as to be movable on a horizontal plane in X and Y directions perpendicular to each other by a numerical control device (not shown). A large number of guide rollers 3a, 3b are interposed between the wire electrode 1, which can be wound around the storage drum 2a of the wire electrode 1, and the wire electrode 1
For the axial update feed drive, brake is applied to the processing part wire electrode 1 between the positioning guides.
The part sandwiched between the pinch roller 4a and the brake roller 5a that applies a predetermined tension to the part is passed through this part, and one of the ship-shaped guides or die guides 6a for positioning the processing part is made to face the workpiece 7. .
This workpiece 7 is mounted on a stand 1 fixed to a table 107.
08 by a clamp plate 109. And this table 107 has a bet of 10
The guide holder 106 is supported by a numerical control device (not shown) and is moved in X and Y directions perpendicular to each other on a horizontal plane parallel to the fine adjustment movement horizontal plane of the guide holder 106. A machining voltage from a machining power source 8 is applied between the wire electrode 1 and the workpiece 7, and machining is performed under the injection of a machining fluid 9.

The wire electrode 1 subjected to electrical discharge machining in the machining section between the guides is connected to the other ship-shaped or die guide 6.
b, multiple guide rollers 3d and guide rollers 3e
The wire electrode 1 is wound around the winding drum 2b through the portion sandwiched between the renewal driving pinch roller 4b and the capstan 5b.

In FIG. 1, reference numeral 10 denotes a vibration prevention device according to the present invention, and FIG. 2 shows a sectional view perpendicular to the wire electrode 1 in the configuration of the main part of one embodiment thereof.

In FIG. 2, reference numeral 11 denotes a main magnetic structure, in which a bar-shaped movable iron piece 12 is inserted into a partially cut-out space so as to be movable in the axial direction, and is held in a predetermined position using a spring 13. The wire electrode 1 passes between a movable contact body 14 and a fixed contact body 15 which are integrally attached to the movable iron piece 12. Magnetic structure 1
1 is fixed to a stand 18 by a pillar 17, and the stand 18 to which the fixed contact body 15 is also fixed is a guide holder 106.
Alternatively, it can be attached to the tip of the lower arm 104.

Further, reference numeral 16 denotes an excitation wire ring, which is energized when it detects that vibration of a predetermined level or higher has occurred in the wire electrode 1 of the processing section having the guides 6a and 6b at both ends, or is energized at predetermined time intervals set in advance. or alternatively, the wire electrode 1 is connected to the fixed contact body 15 by being intermittently excited with a pulse wave having a frequency (including integers, multiples, and fractions of an integer) that approximates the resonant frequency of the wire electrode 1. and the movable contact body 14 momentarily contact each other in a clamping manner during excitation to change the vibration fulcrum of the processing part wire electrode 1 from the positions of both guides 6a and 6b to the position of at least one of the contact bodies 14 and 15. This effectively limits vibrations by damping, stopping, or changing them to higher frequency, lower amplitude vibrations. As an example, 0.2 mmφCu or Cu-Zn is usually used for the wire electrode 1.
A tension of approximately 1 kg is applied between the guides 6a and 6b,
The length between the guides depends on the thickness of the workpiece 7, but
For example, it is about 100mm.

What is illustrated in FIG. 3 is a longitudinal cross-sectional view of another embodiment of the present invention, in which the frequency F of the wire electrode 1 is However, n is the vibration order, L is the length between the supporting points (cm),
Since P is the tension (Kg), g is the gravitational acceleration of 981 cm/s ² , and δ is the weight per unit length of the wire electrode (Kg/cm), the contact member 14 may be instantaneously more than once due to vibrations, etc. , 15, the value of L (usually L is the length between the guides 6a and 6b) is a constant value _L0 .
The purpose is to ensure that vibration stops by allowing settings such as L ₁ and L ₂ to be made.

Therefore, in this embodiment, a pair of annular wire rings 19 and 20 are provided coaxially on a non-magnetic cylindrical support 21 at a predetermined distance apart in the axial direction of the wire electrode 1 so as to surround the wire electrode 1. , this support 21 is fixed to the stand 18. Contact bodies 23 and 24 made of magnetic material or permanent magnets are divided in the radial direction of the wire electrode 1 into pairs, three parts, four parts, etc. in the groove 22 of the support body 21 and are parallel to the axis of the wire electrode 1. It is inserted so that it can be guided and moved in both directions and in the orthogonal direction. And this contact body 2
3 and 24 are fixed to the other ends of springs 27 and 28 whose one ends are fixed to holes 25 and 26 provided in the support body 21, and are supported by the elasticity of the springs 27 and 28.

In this case, the springs 27 and 28 may be simple wire-wound springs, but the holes 25 and 26 may be annular concave portions that open on the inside, and a disk bellows-shaped spring may be used as the contact bodies 23 and 24. The outer periphery of the annular recesses 25 and 26 of the support body 21 is a fan-shaped bellows-shaped collection divided in the radial direction according to the number of parts.
It is preferable to have a structure fixed to the bottom of the case. By energizing these wire rings 19 and 20, the pair of contact bodies 23 and 24 are magnetized and attracted to each other with the wire electrode 1 as the axis, and the wire electrode 1 is momentarily clamped at least once. It is something that comes into contact from around the middle or above. That is, when the attraction force of the contact bodies 23 and 24 is lost by releasing the excitation of the wire rings 19 and 20, the contact body 2
3 and 24 are separated, and contact with the wire electrode 1 is also stopped.

In this device, the contact bodies 23, 20 are controlled by switching the selection of the wire ring 19 or 20 to be excited, or by changing the strength and direction of excitation applied to both the wire wheels 19, 20, for example, as shown in FIG. can be moved to a predetermined position along the axial direction of the wire electrode 1 and brought into contact with the wire electrode 1 in a clamping manner at that position. As a result, the length between the fulcrums of the wire electrode 1 can be changed according to the frequency of the wire electrode 1, and the contact can be made in a pinch-like manner, so that the wire electrode 1 can be reliably contacted regardless of the vibration state of the wire electrode 1. can be stopped. Another example of a device configured to change the length between the fulcrums of the wire electrode 1 according to the vibration state, frequency, etc. of the wire electrode 1 is illustrated in FIG.

This device is the device shown in FIG. 2, in which a stand 18 is slidably supported by a pair of guide rods 29 installed parallel to the wire electrode 1, and a screw 30 screwed onto the stand 18 is shown. The entire vibration prevention device can be moved by rotating it under numerical control using a servo motor. FIGS. 6 and 7 are block circuit diagrams of one embodiment for commanding the excitation of the coils 19 and 20 in the embodiments shown in FIGS. 3 and 4, respectively. 5 is a block circuit diagram of an embodiment for commanding and controlling the operation of a rotation control servo motor (for example, a pulse motor, not shown) of the screw 30 in the embodiments shown in FIGS. 1 and 5. FIG. In FIG. 6, 31 is a clock signal source with an appropriate frequency, and the frequency is divided by a frequency dividing circuit 32 whose frequency division ratio can be changed and control can be changed as necessary.
For example, a signal pulse is output every approximately 0.1S to 3S, and the output is input to each digit element of the monostable element 33 and the ring counter 34. In this embodiment, a ring counter 3 having six digit elements is used.
an output is provided for each 2nd, 4th and 6th digit element of 4;
Each is connected to one terminal of AND circuits 35-1, 35-2, and 35-3. Each of the AND circuits 35
The output of the monostable element 33 is input to the other input terminal of -1, 35-2, 35-3, and the AND circuit 35-1 is connected to the excitation command circuit 19' of the coil 19. The AND circuit 35-3 is configured to output an operation command signal based on the ring product to the excitation command circuit 20' of the wire ring 20, and the AND circuit 35-2 to both the circuits 19' and 20'.

That is, in the circuit of this embodiment, although it depends on the frequency of the clock 31 and the frequency division ratio of the frequency dividing circuit 32,
9. By repeating the order of both the wires 19 and 20, the wire 20, and the wire 19 again, the wires 19 and 20 are excited for about 0.05S each time, for example, at a time interval of about 0.9S, and the contact body 23 and 24 are on the wire ring 19 side,
The wire electrode 1 is brought into contact with the wire electrode 1 at an intermediate position between the wire rings 19 and 20, on the wire wire 20 side, and again on the wire wire 19 side so as to clamp the wire electrode 1 for a moment, thereby damping or stopping the vibration of the wire electrode 1. Or to prevent vibrations that are occurring.

In this case, by sequentially displacing the contact positions of the contact bodies 23 and 24 and the wire electrode 1 in the axial direction of the wire electrode 1 in the support body 21 which is in a fixed position, the pair of vibration prevention devices 10 are brought into contact with each other. body 2
The length between 3 and 24, that is, the wire electrode 1 of the relevant part
or, if the vibration isolating device 10 is provided only on one side, for example, the upper arm 103 side, the vibration isolating device 10 and the other lower arm 104
By changing the length between the wire electrode 1 and the guide 6b, that is, the length of the wire electrode 1 in the corresponding portion, various vibrations that are occurring or are about to occur in the wire electrode 1 portion between the guides 6a and 6b can be controlled. Characteristic vibrations can be reliably damped, stopped, or prevented from occurring.

That is, assuming that the position of the clamp-like contact between the contact bodies 23 and 24 and the wire electrode 1 is always a constant position between the guides 6a and 6b, depending on the generated vibration (high frequency vibration), the above contact position may change. The contact body 23 may not be able to attenuate or stop the vibration because it coincides with the node of the vibration, and this also occurs when the wire electrode 1 is vibrating at a relatively low frequency with a large amplitude. and 24 are relatively close to the vibration fulcrum portion, that is, the guide 6a or 6b, so that it may not be possible to quickly and efficiently attenuate or stop the vibration generated by the wire electrode 1. However, according to the present invention, , the position of the hook-like contact between the contact bodies 23 and 24 and the wire electrode 1 is determined by the guides 6a and 6.
Since the wire electrode 1 constantly moves and changes in the opposite direction of the wire electrode 1, that is, in the axial direction of the wire electrode 1, the above-described drawbacks of the conventional wire electrode 1 can be overcome.

In the above case, the order of excitation of the wire rings 19 and 20, the excitation switching speed, etc. depend on the purpose, the type and material of the wire electrode 1 used, the wire diameter, the length between the guides 6a and 6b, the thickness of the workpiece 7, etc. The settings can be changed as desired. Further, 36 is the frequency dividing circuit 32
This is an input terminal for a signal that increases or decreases the frequency division ratio of the oscillator, depending on the signal for detecting the quality of electrical discharge machining in the machining gap and the frequency and amplitude of the vibration generated in the wire electrode 1. The contact bodies 23 and 2 are arranged so that damping or stopping etc. can be carried out quickly and efficiently.
The contact repetition frequency between the wire electrode 1 and the wire electrode 1 can be changed.

In FIG. 7, parts with the same reference numerals as those in FIG. 6 indicate substantially the same parts or the same working elements, and this block diagram is for driving the screw 30 of the embodiment shown in FIG. 5. A stepping motor (not shown) is rotationally driven by a circuit 30' to move one or both of the vibration prevention devices 10 along the guide rod 29 to a relatively small desired distance in the axial direction of the wire electrode between the guides 6a and 6b. The aim is to perform upward and downward reciprocating movements at relatively short time intervals. Reference numeral 38 denotes an OR circuit, which in the illustrated case outputs a signal to the AND circuit 39 each time a signal enters each digit element of the second and fifth digits of the ring counter 34, and each time a monostable element 33' is triggered. a pulse oscillator 37' that outputs pulses of a desired frequency during the operation period of ';
The output pulse is passed through the AND circuit 39 and output. 40 is a polarity control circuit which inverts the polarity of the output pulse of the pulse generation circuit 37' outputted from the AND circuit 39 every time a signal is input to the third and fifth digit elements of the ring counter 34, and outputs it to the drive circuit 30'. It is something to do. Further, 16' is an excitation circuit to which a signal is input after a desired set delay time via a delay circuit 41 every time the element 33' is triggered, and pulse-excites the excitation wire ring 16. The ring counter 34 may be configured so that a signal is input from a desired digit element, and when the vibration prevention device 10 is at each of the upper and lower limit positions in the axial direction of the wire electrode 1, or when the vibration prevention device 10 is at the upper or lower limit position in the axial direction of the wire electrode 1, During the process, the wire ring 16 is energized so that the contact members 14 and 15 are brought into contact with the wire electrode 1 in a pinched manner.
In this case, the motor driven by the drive circuit 30' has been described as a stepping motor whose rotation angle is determined by the number of drive pulses. A DC motor or an AC motor equipped with a finger speed generator for speed detection control can be used as appropriate, and as in the case of FIG. The vibration prevention device 10 is activated depending on the input, etc., or the combination of use of the column elements of the ring counter 34, etc.
The time interval between the rise and fall of the wire electrode 1 can be changed in various ways, and the vibration of the wire electrode 1 between the guides 6a and 6b can be quickly controlled as in the case of the embodiments shown in FIGS. It is also clear that it can be reliably attenuated or stopped.

Although the movable contact members 14 and 15, 23 and 24 have been described as magnetic materials such as permanent magnets and iron cores, the contact surface side with the wire electrode 1 is made of graphite as mentioned at the beginning. It is desirable to use a low-friction material with low contact friction made of various composite materials, alloys containing low-friction materials, or a felt-like pad.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG.
The figure is a cross-sectional view of the main parts, FIG. 3 is a vertical cross-sectional view of another embodiment, FIG. 4 is a diagram of the operating state of FIG. 3, and FIG. 5 shows the vibration prevention device shown in FIG. The cross-sectional views of the configuration, which can be moved along the
FIG. 5 is a driving block circuit diagram of each vibration prevention device of the embodiment shown in the figure and the embodiments of FIGS. 2 and 5; In the figure, 1 is a wire electrode, 11 is a magnetic structure, 12 is a movable iron piece, 13 is a spring, 14 is a movable contact body, 15 is a fixed contact body, 16 is an excitation wire ring, 19,
20 is an annular wire ring, 23 and 24 are contact bodies, 27 and 2
8 is the spring.

Claims (1)

[Scope of Claims] 1. While a wire electrode is updated and moved in the axial direction between a pair of positioning guides arranged at intervals, a workpiece is moved relative to the workpiece from a direction perpendicular to the axial direction of the wire electrode through a minute gap. In wire cut electric discharge machining in which the wire electrodes are aligned and machined, a plurality of contact bodies are provided between the at least one wire electrode positioning guide and the workpiece so that the contact surfaces face each other in the perpendicular direction with the wire electrodes interposed therebetween. At least one of the contact bodies is provided as a movable contact body movable in the opposing direction, and the movable contact body is driven at predetermined time intervals or in response to detection of vibration of the wire electrode. A device for preventing vibration of a wire electrode in wire cut electric discharge machining, characterized in that the wire electrode is sandwiched between the contact surface of another contact member. 2. Claim 1, characterized in that the movable contact body is a magnetic body or a permanent magnet, moves by wire excitation, and pinches the wire electrode between it and another contact body. The device for preventing vibration of a wire electrode in wire cut electrical discharge machining according to item 1. 3. By sequentially selecting or combining excitation of a plurality of excitation wire rings provided on both sides of the wire electrode in the axial direction with the contact body in between, the pinching contact position of the contact body with respect to the wire electrode is moved in the axial direction of the wire electrode. A device for preventing vibration of a wire electrode in wire cut electrical discharge machining according to claim 1, wherein the device is movable. 4. A device for preventing vibration of a wire electrode in wire cut electrical discharge machining according to claim 1, wherein the holder of the contact body is moved in the axial direction of the wire electrode by a screw moving device.