JPH0375289B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a wire electrode (hereinafter referred to as a wire) automatic supply method for a wire cut electric discharge machining device, in which a supply failure due to a trouble during automatic wire supply is detected, and the wire is automatically supplied again. It's about how to rework supply and make it successful.

First, the configuration of a conventional automatic wire feeding device will be explained based on FIG.

In the figure, reference numeral 1 denotes a wire supply reel, which is connected to a torque motor (not shown), and is configured to apply reverse torque to obtain a braking force sufficient to prevent the wire electrode 2 from slackening. A brake roller 3 is connected to an electromagnetic brake (not shown). Reference numeral 4 denotes a presser roller, which is pressed against the brake roller 3 by a spring force. The wire electrode 2 is sandwiched between the brake roller 3 and the presser roller 4, and a constant tension is applied to the wire electrode 2 without slipping. 5 is a direction conversion roller, 6 is a positioning die, and the inner diameter is the wire electrode 2.
It is slightly larger than the diameter of. 7 is a pinch roller for feeding the wire, and 8 is a presser roller for feeding the wire. The roller 7 is rotated by a pinch roller motor 10 attached to the elevating plate 9 only during automatic wire feeding. Also, roller 8
is pressed against the roller 7 by a spring force, and during automatic wire feeding, the wire electrode 2 is sandwiched between the rollers 7 and 8 and is fed downward in the figure without slipping. . The positioning die 6 prevents the wire electrode 2 from coming off between the rollers 7 and 8.

The lifting plate 9 is raised and lowered by rotation of a ball screw 13 connected to a lifting motor 11 by a coupling 12. A ball nut for converting the rotation of the ball screw 13 into vertical linear motion is attached to the back side of the elevating plate 9 in the figure. This ball screw 13 is supported at one end by a motor mounting portion 15 attached to the lifting guide 14, and the other end is supported by a bearing 16, so that it is supported at both ends. Incidentally, since the elevating plate 9 is supported in elevating and lowering by the elevating guide 14, accurate vertical linear movement is possible.

Further, a pipe guide 17 is fixed to the elevating plate 9 via a guide fixing plate 18. Since the pipe guide 17 moves up and down as the elevating plate 9 moves up and down, it is supported by a bearing 19 to prevent it from wobbling. Furthermore, a die guide 20 for supporting the wire electrode 2 is provided at the tip of the pipe guide 17.
is installed. In addition, bearings 16, 19,
The lifting guide 14 is attached to a fixed plate 21.

Next, 22 is a cutting motor, and 23 is an arm rotation motor, both of which are fixed to a box 24. 25 is a wire cutting section, 26 is a cutting arm,
27 is a tray for discarding wire scraps after cutting the wire. The cutting device 24 and the saucer 2
7 is attached to the fixed plate 21. In addition,
Details of the cutting device 24 and the wire cutting section 25 will be described later.

The pipe guide 17 is connected to the reference V-groove plate 28 during processing.
It is pressed against and fixed by a pressing plate 29. This reference V-groove plate 28 is received by the V-groove surface so that the pipe guide 17 fits therein, and its position is determined. In addition, the reference V groove plate 28
is always fixed to the box 30, and the box 30 is attached to the fixing plate 21. Further, a nozzle 33 is attached to the box 30 for supplying a jet of machining liquid 31 to the machining section 32.

In addition, the pipe guide 17 has three notches as shown in the figure, and during machining, power supply pins 34 and 35 are located in these notches and are in contact with the wire electrode 2 at three points, from which power is supplied. supply Power supply pin 34
is fixed to the moving plate 36, and the pipe guide 1
When 7 moves up and down, move it to the right in the figure to avoid contact. Similarly, the power supply pin 35 is connected to the moving plate 3
7, and is adapted to move to the left in the figure together with the pressing plate 29. 38 is a workpiece, and 39 is a table.

Next, 40 is a lower die guide, and 41 is a lower power feeding die. Both are fixed to the box 42 and attached to the lower arm 43. In the box 42, the machining liquid 31 is jetted into the machining section 32.
A nozzle 78 for feeding the wire electrode 2 is attached thereto, and a guide nozzle 44 for guiding the wire electrode 2 is attached.

The wire electrode 2 passing through the guide nozzle 44 is
It travels while being sandwiched between a lower belt 47 stretched between belt rollers 45 and 46 and a lower roller 48, and is guided to a wrapper tube 49. Thereafter, the wire electrode 2 passes through the collection pipe 50, is sandwiched between a collection belt 53 stretched between collection rollers 51 and 52, and a collection roller 54, and is led to a collection box 55, as shown in the figure. The wire electrode 2 is discarded in a circular manner. Note that the feeding speed of the wire electrode 2 is variable by the rotation of a motor with a reduction gear attached to the back side of the collection roller 54 in the figure, and furthermore, the collection roller 54 and the lower roller 48 are transmitted by a belt on the back side. Moreover,
Since the two rollers 48 and 54 have the same diameter, they rotate synchronously. Therefore, wire electrode 2
is pulled without slipping by the frictional force of the lower roller 48 part and the collection roller 54 part, and is collected into the collection box 55.

Next, devices 22, 23 for cutting the wire electrode 2,
The configuration of 24, 25, and 26 will be explained using FIG.

56 is a cutter for cutting the wire electrode 2, and is fixed to the movable rod 58 with a screw 57. A wire electrode 2 is attached to the tip of the moving rod 58.
A support rod 59 that supports the material so that it does not move when cutting.
is fixed, and rubber 60 is adhered to the contact portion to prevent slipping. Further, 61 is a cutting receiving plate, which is fixed to the cutting arm 26 with screws 62. The cutting receiving plate 61 has a rubber 6
4 is glued to prevent slipping. When cutting the wire electrode 2, the movable rod 58 moves to the left in the figure between the cutting receiving plate 61 and the cutter 56, and at the same time the rubber 60 is cut.
and 64. The right end of the movable rod 58 in the figure is threaded, and after a compression spring 65 is inserted, a locking nut 66 is screwed in to fix it. The horizontal movement of the moving rod 58 is performed by an eccentric cam 67.
This is done by a half-rotation motion. The figure shows a case where the eccentric cam 67 is at the rightmost end, and the moving rod 58 is also at the right end due to the restoring force of the compression spring 65. Conversely, when cutting the wire electrode, the eccentric cam 67 rotates half a turn to the leftmost position, so the movable rod 58 and locking nut 66 are positioned at the leftmost position and the cutter 56 and the cutting receiving plate 61 are connected to each other. disconnected between.

Next, the rotation of the cutting arm 26 will be explained.

When the arm rotation motor 23 attached to the box 24 rotates, the gear 70 is rotated by the gear 69 attached to its shaft. The gear 70 is fixed to an arm rotating rod 71 and further connected to the cutting arm 26. The arm rotation rod 71 is supported by bearings 72 and 73. However, as the arm rotation motor 23 rotates approximately half a turn, the cutting arm 26 rotates 180° in the opposite direction in the figure and then stops. The position 180° opposite to the position shown in the figure can be determined by detecting it with a limit switch or the like.

Next, the rotation of the eccentric cam 67 will be explained.

An eccentric cam rotation rod 74 is inserted into the center of the arm rotation rod 71, as can be seen in the cut-off section of the figure, and is rotatable. An eccentric cam 67 is fixed to the lower end of the eccentric cam rotating rod 74, and can be smoothly rotated by a bearing 75. Further, a cutting motor 2 is connected to the upper end via a coupling ring 76.
It is connected to 2. Therefore, the cutting arm 26
When the arm rotation motor 23 is rotated to position it on the opposite side by 180 degrees, the cutting motor 22 is also activated at the same time and rotated by 180 degrees. As a result, the relationship between the eccentric cam 67 and the locking nut 66 does not change as shown in the figure, so the wire electrode 2 is located between the cutter 56 and the cutting receiving plate 61. Thereafter, by further rotating only the cutting motor 22 by 180 degrees, the movable rod 58 moves toward the cutting receiving plate 61, and the wire electrode 2 can be cut as described above. Thereafter, when the arm rotation motor 23 is rotated 180 degrees in the opposite direction, the cutting motor 22 is also activated at the same time, thereby returning to the position shown in the figure, and the moving rod 58 is at the leftmost position. Then, by rotating the cutting motor 23 by 180 degrees, the state shown in the figure can be restored.

Next, referring to FIG. 3, the operation of cutting the wire electrode 2 will be explained.

First, in FIG. 3a, the wire electrode 2 is connected to the workpiece 38.
This is a case where the cutting operation is started by initializing the state in which the hole 77 passes through the machining start hole 77. That is, the first
The figure shows the initial settings. First, moving plates 36 and 3 to which power supply pins 34 and 35 are attached in order for the pipe guide 17 to rise in the direction of the arrow in the figure.
7 and the pressing plate 29 to which the moving plate 37 is attached moves in the direction of the arrow in the figure.

Note that the pipe guide 17 rises to a certain predetermined position and then stops.

At this time, as described in FIG. 1, the wire feeding pinch roller 7 and the wire feeding press roller 8
The pipe guide 17 rises and stops together with the pipe guide 17, and also rotates from the direction shown by the arrow in the figure.

The reference V-groove plate 28 is always fixed, and when the pipe guide 17 moves up and down, it rubs against it. Note that the nozzle 33 is always fixed. The die guide 20 has enough clearance to rub against the wire electrode 2 when the pipe guide 17 rises. The lower end position of the die guide 20 in figure a will be referred to as the cutting position.

Next, FIG. 3b shows the state in which the cutting arm 26 has been rotated 180° and brought to the cutting position. As a result, the wire electrode 2 is positioned at the cutting portion 25. The operation of the cutting motor 22 and arm rotation motor 23 is as described in FIG. At this time, the wire feeding pinch roller 7 and the wire feeding press roller 8 are stopped. Moreover, a one-way clutch (not shown) is attached to the pinch roller 7 to prevent it from rotating in the direction opposite to the direction of the arrow in FIG. 3a.

Next, FIG. 3c shows the state after the wire electrode 2 is actually cut. That is, as described in FIG. 2, after cutting, the cutting arm 26 rotates 180°
It rotates and returns to normal. The lower part of the wire electrode 2 after cutting is recovered by detecting that the cutting motor 22 has further rotated 180 degrees as described in FIG. 2, and the recovery roller 54 shown in FIG. It is collected into box 55.

Next, FIG. 3d shows a state in which the wire electrode 2 has actually been completely cut. That is, after the state shown in FIG. 3c is completed, the pipe guide 17 descends until it reaches the state shown in FIG. 3d. In this state, the movable plates 36 and 37 are still moved in the initial state shown in FIG. 3a, and the pipe guide 17 is now in the first position.
It is in the same position as in the figure. Dice guide 2 at this time
The lower end of 0 will be called the home position.

Note that while the pipe guide 17 is descending, the wire electrode 2 is sandwiched between the wire feeding pinch roller 7 and the wire feeding press roller 8.
Moreover, a one-way clutch is attached to the pinch roller 7, so that the pinch roller 7 does not reverse rotation, so that it does not slip out of the tip of the die guide 20 and come out upward. Cutting is completed when the state shown in Figure 3d is reached.
During the cutting operations shown in FIGS. 3a to 3d, the braking force of the electromagnetic brake connected to the brake roller 3 shown in FIG. 1 is extremely weakened.

Next, referring to FIG. 4, the insertion operation of passing the wire electrode 2 through the processing start hole and the lower die guide will be described.

Here, the process of passing the wire electrode through the machining start hole, then the lower die guide, and sending it to the collection box 55 in FIG. 1 will be referred to as the insertion operation of the wire electrode 2. First, the state shown in FIG. 4a is the initial state of the wire insertion operation. This is the same state as the final state of the cutting operation in FIG. That is, the upper die guide 20, the machining start hole 77, and the lower die guide 40 are aligned in the vertical direction.

Next, as shown in FIG. 4b, the pipe guide 17 is lowered and passed through the machining start hole 77, and the upper die guide 20 and lower die guide 4
0 is placed opposite. The lower end of the upper die guide 20 in this state will be referred to as the lower limit.
This position is detected by a limit switch or the like.

Next, as shown in FIG. 4c, the wire electrode 2 sandwiched between the wire feeding pinch roller 7 and the wire feeding press roller 8 starts to advance due to the rotational force of the wire feeding pinch roller 7 and the wire feeding press roller 8. Figure 4c shows the lower die guide 40.
The wire electrode 2 is shown passing through.

Thereafter, as seen in FIG. 1, the wire electrode 2 passes through the feeding die 41, the guide nozzle 44, and is guided to the lower belt 47. Note that the lower roller 48 and the recovery roller 54 start rotating at the same time as the pinch roller 7 and the press roller 8 rotate in FIG. 4. The lower roller 48
The collection rollers 54 and 54 are synchronized by belt transmission. Therefore, when the wire electrode 2 advances to the entrance of the lower belt 47 and the lower roller 48, it is drawn in between them and guided.
It is collected into a collection box 55 as shown in the figure. By sensing the contact between the power feeding die 41 and the collection box 55, it is possible to determine whether the wire electrode 2 has been led to the collection box 55. After the contact is sensed in this way, the pipe guide 17 rises to a fixed position and stops as shown in FIG.
moves in the direction of the arrow in the figure to fix the pipe guide 17, and the power supply pins 34 and 35 become capable of supplying power to the wire electrode 2. This makes it possible to start machining, and at the same time the insertion operation is completed in the state shown in FIG. 4(d). In addition, during the insertion operation shown in FIG. 4, the brake roller 3 shown in FIG.
The braking force of the electromagnetic brake connected to is extremely weakened.

As described above, the conventional wire automatic feeding method is a method in which a cutting operation is performed every time the machining start hole changes, and then an insertion operation is performed to automatically bring the wire into a state ready for machining.

Next, we will discuss the drawbacks of this conventional automatic wire feeding method during the insertion operation.

First, "during insertion operation" refers to steps a to d in FIG. 4. There are many different kinds of troubles that may occur during the insertion operation, but the trouble that makes it impossible to continue the insertion operation will be explained with reference to FIGS. 5 and 6. Consider a case where the distance between the lower surface of the workpiece 38 and the upper end surface of the lower nozzle 78 is large, as shown in FIGS. 5a and 5b. The figure also corresponds to the state shown in Figure 4c, where the pipe guide 17 is in the machining start hole 7.
7, which is at the lower limit. The lower die guide 40 is shown in cross section, and a die 79 of jewelry such as diamond or sapphire is embedded in the center.

In the case of FIG. 5a, the wire electrode 2 is connected to the die 7
9, but instead enters the gap between the lower die guide 40 and the lower nozzle 78. This is because the initial state of the wire electrode 2 is due to internal strain or curl. On the other hand, in the case of FIG. 5b, the curl is even more curly, and the curl is so large that it protrudes outside the lower nozzle 78. In both cases, since the wire electrode 2 has not passed through the die 79, the insertion of the wire electrode 2 naturally fails, and subsequent electric discharge machining cannot be performed, making it impossible to continue.

Next, as shown in FIG. 6, let us consider a case where the shortcoming of FIG. 5, which is that the distance between the lower surface of the workpiece 38 and the upper end surface of the lower nozzle 70 is large, is solved.
Other situation settings are the same as in FIG.

In the case of FIG. 6a, the wire electrode 2 passes through the die 79 successfully. As expected, the fifth
It can be said that the wire electrode 2 is more easily guided to the position of the lower die guide 40 in FIG. 6 than in the figure.

However, when the wire electrode 2 is bent at a substantially right angle to the introduction taper portion of the lower die guide 40 as shown in FIG. 6b, the wire electrode 2 becomes stuck and cannot advance any further. Further, as shown in FIG. 6c, machining chips generated by electrical discharge machining may accumulate on the introduction taper portion of the lower die guide 40 over a long period of time. This is because the deposits 80 are hard and irregular because they are not constantly immersed in the machining fluid and are repeatedly dried at intervals. In this case, compared to FIG. 6b, the jammed state occurs more often, and the wire electrode 2 is prevented from advancing as in FIG. 6b. In the cases shown in FIGS. 6b and 6c, the progress of the wire electrode 2 is not only hindered, but also large bends or breaks occur when trying to move the wire electrode 2 in the direction of the arrow with a stronger force, as shown in FIG. Similarly, insertion of the wire electrode 2 will fail, making it impossible to continue.

In view of the above-mentioned drawbacks, the present invention attempts to significantly improve the probability of a successful wire electrode insertion operation by detecting a failure, causing the insertion operation to be restarted, and ultimately succeeding.

First, we will describe the principle of classifying failures during insertion operations and detecting each failure. Let's consider the two types of failure as shown below.

(1) Cases in which the advancement of the wire electrode is impeded The main cases shown in Figure 6 are the cases where a high load is applied to the advancement ability of the wire electrode, so we separately describe the case in Figure 6. It includes, but is not limited to, anything that impedes progress.

(2) When the wire insertion operation is not completed Mainly as shown in Figure 5, unlike in (1) above, the progress of the wire electrode is not hindered, but the wire electrode advances in a direction other than the insertion path. There is.

First, regarding failure (1) above, we will discuss the detection principle in that case.

FIG. 7a corresponds to the state of FIG. 4c. That is, the wire feed pinch roller 7 is driven, and the wire electrode 2 is sandwiched between the wire feed presser rollers 8 and moves in the direction of the arrow in the figure. The wire electrode 2 has a small clearance with the die 81, so it slides. In addition, the wire feeding presser roller 8 is attached to a fixed plate 82.
In contrast, the wire electrode 2 is pressed against the wire feeding pinch roller 7 by the force of the spring 83. Here, the force for advancing the wire electrode 2 is as follows. From the figure, the vertical force N due to the force of spring 83,
If the coefficient of friction between the rollers 7 and 8 and the wire electrode 2 is μ, then the frictional force exerted by the rollers 7 and 8 to advance the wire electrode 2 is μN. In addition, the wire electrode 2 above the rollers 7 and 8 has
A tensile force T _p is acting. However, T _p is the first
This is due to the braking force acting on the supply reel 1 and the braking force acting on the brake roller 3 in the figure, but during the insertion operation, the braking force of the brake roller 3 is weakened to the minimum in order to reduce T _p . . Therefore, the force for advancing the wire electrode 2 is μN-T _p from the figure. It goes without saying that μN>T _p .

Next, FIG. 7b shows a case where there is an obstacle 84 on the traveling path of the wire electrode 2. However, in reality, it refers to the high load shown in Figure 6, but for the sake of simplicity, it will be treated as an obstacle in Figures 7 and onwards.

FIG. 7b shows a state in which the wire electrode 2 is deformed by bending force inside the pipe guide 17 because its progress is obstructed by the obstacle 84. Therefore, it is an elastic deformation that opposes the bending rigidity, so F in the figure
As shown, a reaction force acts in the direction of reversing the deformation. Therefore, the wire feeding pinch roller 7 continues to rotate because it is a one-way clutch that can freely rotate in the direction of the arrow, but it slips between it and the wire electrode 2, and the wire feeding presser roller 8 stops rotating.

In other words, the state is F+T _p =μN.

To explain in more detail, as shown in FIG. 7c, the inner wall 85 of the pipe guide and the wire electrode 2
If the friction coefficient of is μ ₁ and the normal force pressing against the inner wall 85 is n, then the force μN that tries to insert the wire electrode 2 into the pipe guide (range indicated by L in the figure) is
_-Tp , the wire electrode 2 is deformed and comes into contact with the inner wall 85 at multiple points as shown in the figure, generating a frictional force of μ _1o at each point. Due to these, the wire electrode 2 generates a spring-like action inside the inner wall 85, and as the contact progresses at multiple points, the wire electrode 2 progresses to deformation at a short portion. , the resultant force F of the reaction force of the bending deformation
is increasing. Its final form is the seventh
In Figure b, F=μN−T _p . That is, in the state shown in FIG. 7b, the advance of the wire electrode 2 is completely stopped.

Therefore, the inventor actually conducted an experiment to confirm FIG. 7. As a result of various experiments, it was found that although the wire electrode 2 may come to a complete stop, there are interruptions in its progress.

This will be explained using FIG. 8.

FIG. 8a shows a case where the wire electrode 2 has not yet reached the obstacle 84. 86 is the wire electrode 2
87 is the position of the die portion. Even in this case, a frictional force f _p occurs when the wire electrode 2 passes through the die portion. That is, the state is μN-T _p >F _p , and the wire electrode 2 is drawn in the direction of the arrow 88.

Next, FIG. 8b shows a case where the wire electrode 2 comes into contact with an obstacle 84, and f _p increases to f ₁ (>f _p ). However, since μN−T _p >f ₁ , the arrows 88 are still in the same direction.

Next, c and d are states in which the bending deformation of the wire electrode 2 is increasing within the pipe guide inner wall 85, and the reaction forces are increasing to f ₂ and f ₃ , but still μN−
Since T _p > f ₂ , f ₃ , the direction of the arrow 88 does not change.

Next, as the bending of the wire electrode 2 progresses to e in Figure 8, the reaction force increases to f ₄ and becomes μN-T _p = f ₄ , which is the same as in Figure 7 b, and the wire electrode The progress of 2 will stop. Ideally, the wire feeding pinch roller 7 rotates while sliding on the two surfaces of the wire electrode. However, in reality, due to play in the one-way clutch and drive transmission gear attached to the pinch roller 7, changes in the concentricity of the pinch roller, changes in the surface texture of the outer periphery of the pinch roller 7, etc., the pinch roller 7 is reversed and the μN As a result of the change in , as shown by f, it is reversed by the reaction force f ₄ and returns to f ₄ −Δf.

That is, at f, the direction of the arrow 88 changes and the wire electrode 2 returns. However, the reaction force drop Δf can be considered to correspond to the decrease in μN.

Next, the direction of the arrow 88 is changed again as shown in FIG. 8g, and the wire electrode 2 is fed. and the eighth
By repeating the cycle shown in FIG. e → FIG. 8 f → FIG.

The length of the wire electrode 2 fed into the range L in so-called e, f, and g of FIG. 8 causes a spring vibration accompanied by a change in the reaction force f ₄ (Δf). This movement continues as long as the wire in the range _L1 in the figure does not buckle.

At this time, the direction changing pulley 5 shown in FIG. You can judge whether it is hot or not. This type of detection will be termed high load detection during wire electrode advancement.

Next, we will describe the detection principle for the second failure mentioned above.

FIG. 9 shows a case where the upper die guide 20 and the lower die guide 40 are at the farthest position during the wire insertion operation. In this case, contact is sensed between the pipe guide 17 and the workpiece 38 (they are electrically connected through the die guide 20), and the wire electrode 2 begins to advance. The plate thickness of the workpiece 38 is set at the maximum H _nax . Furthermore, the length of L in the figure is unique to the machine and can be uniquely determined.

First, the wire electrode 2 indicated by a solid line is a case where the insertion is successful, and the upper die guide 2
The wire electrode 2 fed from the machining start hole 77
, passes through the nozzle 78 , the lower die guide 40 , the power supply die 41 , and the guide nozzle 44 in order, and is sent between the belt roller 45 and the lower belt 47 and the lower roller 48 , and is then pulled by the lower roller 48 . go. This is the regular wire insertion route, and the time and distance required for this are almost uniquely determined. The wire electrode 2 indicated by a broken line is an example of a failed insertion, and has come off the insertion path. Therefore, the present inventor devised a failure detection method based on the fact that the speed at which the wire electrode is advanced by the wire feeding pinch roller 7 shown in FIG. 1 and the speed at which the wire electrode is advanced by being pulled by the lower roller 48 are different. I found it. That is, the advancing speed by the lower roller 48 is the same as the speed during electrical discharge machining, and the speed by which the wire feeding pinch roller 7 passes through a small clearance such as the die guide 40 is slowed down.

Next, the detection principle will be explained using FIG. 10.
The vertical axes of a and b are the advancing speed V of the wire electrode 2, where V ₂ is due to the lower roller 48 and V ₁ is due to the wire feeding pinch roller 7. Also, on the horizontal axis, S is the length along the wire insertion path from the die guide 20 in FIG. 9, and T is the elapsed time from when the wire electrode 2 first advances by the wire feeding pinch roller 7.

First, a is a graph of V and S, where 89 indicates successful insertion and 90 indicates failed insertion.

As you can see from this graph, on the insertion path
After progressing a distance of H _nax +L, if successful, V ₁ to V ₂
The speed increases to, and in case of failure, it remains at V ₁ . The reason why the speed does not increase immediately from V ₁ to V ₂ at the L position is due to the deviation due to the time taken to draw the belt into the lower belt.

Next, as can be seen from the graph in Figure 10b, the first
The time T _L for the speed to increase from V ₁ to V ₂ in Figure 0a is uniquely determined. Therefore, if the wire electrode 2 is advanced by the wire feeding pinch roller 7 and the advancing speed has not increased from V ₁ to V ₂ after a maximum of T _L has elapsed since the first time, it is determined that the wire has deviated from the wire insertion path and is treated as a failure. can be handled.

In this way, failure can be detected by detecting a change in the advancing speed after a certain period of time after the wire electrode 2 first advances. This type of detection will be referred to as detection of wire electrode 2 coming off from the wire insertion path.

Next, an example of a circuit that actually detects failure will be described. First, a high load detection circuit when the wire electrode 2 is advanced will be described.

First, as explained in FIG.
In order to detect the intermittent movement of the progress of the movement, the intermittent movement of the rotation of the direction changing pulley 5 shown in FIG. FIG. 11 shows a detection device for this purpose.
In FIG. 11a, the direction changing pulley 5 includes:
An encoder 91 is attached. When the wire electrode 2 moves intermittently, the direction changing pulley 5 rotates intermittently. FIG. 11b also explains how to use the encoder 91. P5
(+5V) External power supply is shared between the diode side and the transistor side. R is a resistor that limits the current flowing to the diode. The output side A and B terminals are connected to a detection circuit.

Next, the detection circuit will be explained using FIG. 12. Note that the A and B input terminals correspond to those shown in FIG. 11, and the B side is the diode side.

In this Figure 12, the encoder output is 0
Since it is AC in the range of ~5V, first connect the capacitor.
C ₁ and resistor R ₁ cut off the DC component and leave only the AC component. Next, R3/R2 is set by OP amplifier 92.
Perform double amplification. Then the diodes D ₁ , D ₂
Clamps in the range of 0 to 5V. The waveform of W2 after passing through the inverter is converted into a pulse in the range of 0 to 5V by shaping the alternating current of W1. 93 is a one shot for high load detection, and the output pulse has a width of T _c1 . Relay coil _L1 is for high load detection, and D3 is a protection diode. Also, 94 is a one shot for failure detection outside the insertion path, which will be described later, and the output pulse is T _c2
This is the width.

Relay coil L ₂ is for detection outside the insertion path, D4
is a protection diode.

Using the waveforms of W1, W2, and W3 in Fig. 12,
A schematic timing chart is shown in Fig. 13,
A high load detection method will be explained.

W1 in FIG. 13a is the output waveform of the encoder. This is the rotation of the direction changing roller by the wire feeding pinch roller, and is the case when the wire is inserted. At this time, the waveform of W2 is a square wave pulse with a period T _i . Since the waveform of W3 generates a one-shot pulse at the rising edge of the pulse of W2, it is always at a high level of 5V while the wire is being inserted because T _i <T _c1 .

Therefore, it can be seen that the relay coil _L1 in FIG. 12 is in the ON state. This state is a state where no high load is occurring.

Next, under the situations e, f, and g in Figure 8, the first
This becomes the waveform of W2 in Figure 3b. That is, a pulse with a normal pulse width and period T ₁ and a pulse with a short pulse width and a long pause period T ₂ repeatedly appear. this is,
In order to output pulses even if the encoder is reversed, if the wire electrode 2 is returned by the spring force as shown in Figure 8f, the reverse rotational force acts instantly and the pause at T ₁ in Figure 13b occurs. is shorter, and the pulse of T ₂ is also shorter. On the other hand, in the case of Fig. 8g, the rotation of the pinch roller for wire feeding is when the forward rotation is started, so it takes the maximum startup time, so the first
This results in a longer pause, as shown at T ₂ in Figure 3b. When the detection circuit was actually observed with a synchroscope, a waveform corresponding to W2 of b was confirmed.

As a result, a zero level with a width of T _f1 occurs in the waveform of W3. At this time, relay coil _L1 in FIG. 12 is in an OFF state. In this way, the occurrence of intermittent rotational movement of the direction conversion pulley can be detected by changing the state of relay coil _L1 from ON to OFF.

Next, a failure detection circuit outside the insertion path and a timing chart will be explained.

The detection circuit is the same as that shown in FIG. 12.

FIG. 14 is a timing chart when inserting the wire. The section of T _s seen at W1 in FIG. 14a is the same as the state in FIG. 13a, and is caused by the rotation of the wire feeding pinch roller 7 It is. The subsequent high frequency portion in FIG. 9 shows a state in which the wire electrode 2 is drawn into the lower belt 47 and the advancing speed of the wire electrode 2 increases.

Therefore, as seen in Figure 14b,
The period of T _s is the period T _i and thereafter changes to the period T _n . At this time, since the one-shot width of the waveform W4 is T _c2 (T _i > T _c2 > T _n ), the pulse width is T _c2 during the T _s period, and is at a high level thereafter. Therefore, since T _s corresponds to the time when the insertion is successful, the state of W4 is always at a high level after a time _TD such that, for example, T _s < _TD .
In other words, the relay coil _L2 in Fig. 12 is activated after the wire feeding pinch roller 7 starts rotating.
After T _D, it is always in the ON state.

Next, when the wire electrode 2 advances out of the wire insertion path, as shown in FIG. 14b, the waveform of W2 continues as a pulse with a period of T _i and the waveform of W4 continues as a pulse with a pulse width of T _c2 . So after T _D (T _D > T _s ), W4
By looking at the waveform of , we can see that there is a pause called T _f2 .

At this time, the relay coil _L2 in FIG. 12 is in the OFF state. In this way, if the wire electrode 2 comes off the insertion path during insertion, it can be detected by determining whether the relay coil _L2 is turned OFF or OFF from ON after _TD .

Next, a relay sequence circuit that generates a failure detection signal from the states of the relay coils L ₁ and L ₂ will be explained using FIG. 15.

The coils of timer relays RT ₁ , RT ₂ and relays f ₁ , f ₂ operate on P24 (+24V). #M20 is a relay for a wire insertion command given by a computer or the like or manually, and #WF is a relay that is turned ON while the wire feeding pinch roller is rotating.

First, in the case of a high load failure, relay #WF is turned ON by the start of wire insertion, and timer RT ₁
is set. Relay # _RT1 turns ON after 2 seconds. The back contact of relay #1RA is open during normal operation and closes when a failure occurs, resulting in a short circuit, so failure detection relay # _f1 is turned ON and held. Relay #RT ₁
has a detection inhibiting function to prevent false detection at the start of the wire electrode 2's movement.

Next, in the case of failure outside the insertion path, timer _RT2 is set from the start of wire insertion. Relay #RT ₂ turns ON after TD. Since relay #2RA is short-circuited in the event of a failure, similar to the failure of variable load, failure detection relay # _f2 is turned ON and held.

Therefore, relay #f ₁ or #f ₂ is turned ON in response to either failure. So P5 (+
When relays #f ₁ and #f ₂ are connected in parallel to 5V), the F output changes to high level in response to either failure. This F signal may be transported to a computer or the like.

Next, when processing the F signal using a computer, the processing method to be used will be explained using the flowchart shown in FIG. 16.

First, by flow start, an insertion command is issued to perform an insertion operation. Unless a failure is detected (the F signal is at a high level), the insertion is completed.
If a failure is detected, it is determined whether the number of failures has reached N times. If the number of times has reached N, it is assumed that there is an abnormality in the mechanical device and the function is stopped. If the number of times has not reached N, a cutting command is issued to cause the cutting operation to be performed. The cutting and insertion mentioned here means the series of operations shown in FIGS. 3 and 4. That is, the wire electrode 2 that was required to fail in the cutting operation is cut by the cutting device shown in FIG.
The cut portion of the wire electrode (cut portion of the wire electrode) is removed, and then the insertion is performed with a new wire electrode 2, ie, the wire electrode from which the cut portion of the wire electrode described above has been removed.

After the cutting is completed, the insertion command is issued again and the cycle of issuing the insertion operation is repeated. In this way, the first
The flow shown in FIG. 6 is repeated until the insertion is successful, that is, until the number of failures reaches n times.

Here I will explain why I am counting the number of failures.

If the probability of failure when inserting the wire electrode 2 is x, then the probability of failure N times in succession is ^xN . Therefore, the probability P that the wire insertion is successful at the m-th time is as follows.

P(m)=1−x ^m (Example) () When x=50% m=5 times P(5)=97% m=7 times P(7)=99% () When x=30% m = 3 times P(3) = 97% m = 4 times P(4) = 99% As you can see from the above example, the success rate of one insertion is 50
% (x = 50%), the success rate increases to 99% by detecting failure seven times and retrying the insertion. Also, if the success rate for one attempt is 70% (x = 30%), it increases to 99% by reinserting it four times.
In this way, even if the probability of successful insertion at one time is low, the success rate increases by repeating insertion several times. In other words, it can be said that the reliability of insertion has been significantly improved.

In summary, the present invention detects failure during wire insertion and leads to success by re-inserting the wire, thereby providing a highly reliable automatic wire feeding method.

Further, according to the present invention, since reinsertion is performed using a new wire electrode, the success rate is extremely high.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional automatic wire feeding device, FIG. 2 is a block diagram of a conventional cutting device, FIG. 3 is a diagram showing a conventional cutting operation, and FIG. 4 is a diagram showing a wire insertion operation. 5 and 6 are diagrams showing the conventional drawbacks, FIGS. 7 to 10 are diagrams explaining the reasons for the drawbacks and the ripple effects, and FIGS. 11 and 12 are diagrams showing the drawbacks of the conventional technology. Embodiment diagrams of detection means and circuits,
13 and 14 are timing charts of the detection circuit and the detection principle, FIG. 15 is a relay sequence diagram for generating an insertion failure signal, and FIG. 16 is a flowchart for implementing the present invention by computer. It is a diagram. In the figure, 2 is a wire electrode, 5 is a direction conversion pulley, 91 is an encoder, 92 is an OP amplifier, 9
3.94 is a one shot. Note that the same reference numerals in the figures indicate the same parts.

Claims (1)

[Scope of Claims] 1. A method for automatically supplying wire electrodes in wire cut electric discharge machining, which automatically supplies wire electrodes used in wire cut electric discharge machining in the following process order. (a) A first step of passing the wire electrode from the wire electrode supply section to the machining start hole of the workpiece. (b) A second step of supplying the wire electrode toward a wire electrode recovery section after the first step. (c) During the second step, detecting that the wire electrode does not engage with the wire electrode collection part after a predetermined period of time has elapsed, or detecting that the wire electrode cannot advance due to load during propulsion. Step 3. (d) A wire electrode cutting device is operated based on the detection signal in the third step, and the wire electrode supplied from the wire electrode supply unit up to the detection is cut by the cutting device, and the wire electrode is cut. The fourth step is to eliminate the parts. (e) After the fourth step, a fifth step of again supplying the wire electrode from which the cut portion of the wire electrode has been removed toward the wire electrode recovery section.