JPH05305522A - Cutting off device for wire electrode in wire electric discharge machine - Google Patents

Abstract

(57) [Abstract] [Purpose] To form a pointed tip suitable for a wire electrode without damaging parts such as a wire guide of an electric discharge machine or a workpiece. A wire motor during electric discharge machining is equipped with a discharge motor for discharging while pre-tensioning the wire electrode between the feed side and the discharge side. Between the feed upstream side of the wire electrode and the workpiece,
By the powder brake, the feed roller and the second pinch roller, a constant tension is applied when the wire electrode is melted, and a fusing current is applied to the fusing part of the wire electrode by the wire fusing means. The discharge motor is controlled to discharge the wire electrode after a lapse of a predetermined time for applying a predetermined tension and a melting current to the melting portion of the wire electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting device capable of adjusting the shape of a wire cutting portion when a wire electrode in a wire electric discharge machine is stretched again.

[0002]

2. Description of the Related Art Conventionally, in this type of wire electric discharge machine, an electric discharge pulse for machining is applied to an electric discharge machining gap between a wire electrode and a workpiece to form an electric discharge such as a hole having an appropriate cross-section. When machining, for example, after the machining of one machining hole is completed and before machining the next machined portion, the wire electrode is forcibly cut once, and the tip of the wire electrode after this cutting is It is necessary to pass through a processing start hole or the like formed at the processing start position and stretch it again. At that time, in order to automate the re-stretching operation smoothly and with high reliability, the shape of the tip of the wire electrode after cutting should be smoothly inserted into the wire guide and the machining start hole of the workpiece. It is necessary that the shape is easy to do. That is, when the tip of the wire electrode 8 is bent as shown in FIG. 8, it is difficult to enter the processing start hole or the like, but as shown in FIG. 9, the tip of the wire electrode 8 is not bent and has a tapered tip. Ideally, it is a head shape.

In order to form the ideal pointed tip as described above, it is conceivable to use an essential mechanism in an electric discharge machine. That is, in general, in an electric discharge machine,
Feeding upstream side (feeding side) of the wire electrode across the work piece
The used brake electrode and the discharge mechanism by the drive roller arranged on the feed downstream side of the work piece discharge the used wire electrode to the outside of the machine while applying a predetermined pre-tension to the wire electrode during electric discharge machining. Is configured to.

Even when the pointed tip portion is melted, if the wire electrode is tensioned by the brake mechanism and the discharge mechanism, the wire electrode moves while receiving the tension because of the mechanism of the discharge mechanism. Since the constricted portion and eventually the fusing portion are not determined, there is an inconvenience that an appropriate pointed tip portion cannot be formed. As a conventional prior art for forming the above-mentioned ideal pointed tip, there is disclosed a structure as shown in Japanese Patent Publication No. 61-26455, which is a workpiece and the brake mechanism. An electric heating mechanism for melting and cutting the wire electrode and a pair of pinch rollers as a tension applying mechanism are provided between and.

That is, in this prior art, the wire diameter of the fusing part is changed by heating the wire electrode by the current-carrying heating mechanism while applying tension to the downstream side of the wire electrode feeding by the tension applying mechanism for a certain period of time. A so-called constricted portion is formed so as to be thin, and after the constricted portion is formed, tension application by the tension applying mechanism is released, and heating is further continued to form a pointed cutting portion. After that, the clamping of the wire electrode by the tension applying mechanism is released, and then the driving roller of the discharging mechanism is driven to control so as to discharge the wire electrode on the downstream side of the feeding to the outside of the machine.

However, it takes time to cut the wire electrode because the wire is cut only by heating after the application of the tension by the tension applying means is released. Therefore, in order to shorten the cutting time, a technique in which tension is continuously applied by the tension applying mechanism until the wire electrode is cut may be considered. In other words, while applying tension to the wire electrode by the tension applying mechanism, the wire is heated and cut by the electric heating mechanism, and after detecting the cutting by the sensor, the driving roller of the discharging mechanism is driven to feed the cut feed. The configuration is such that the wire electrode on the downstream side is discharged to the outside of the machine.

[0007]

However, until the sensor detects the cut end of the wire electrode, the wire electrode on the feed downstream side cut by the tension applying mechanism is sent to the discharge side (feeding downstream side). Therefore, the cut wire electrode bends in the gap of the processed portion of the workpiece or the insertion path of the wire guide, and buckles in the gap of the wire guide or the already processed portion. Therefore, in this buckled state, if the wire electrode is forcibly pulled to the downstream side in order to eject the wire electrode by the drive roller of the ejection mechanism, there is a problem that the surface of the wire guide or the processed portion of the workpiece is damaged. It was

The present invention solves such a problem and is capable of forming an optimum pointed tip portion on a wire electrode, but does not damage parts such as a wire guide of an electric discharge machine or a workpiece. It is an object of the present invention to provide a wire electrode cutting device for a wire electric discharge machine.

[0009]

In order to achieve the above object, a wire electrode cutting device in a wire electric discharge machine according to the present invention comprises a wire electrode which is being electric discharge machined between a feed side and a discharge side. A discharging means for discharging while applying a pre-tension, a wire fusing means for applying a fusing current to a fusing part of the wire electrode, and a wire electrode feeding upstream side and a workpiece, at the time of fusing the wire electrode. The wire electrode is discharged by the discharging means after the elapse of a certain time period in which a predetermined tension and a fusing current are applied to the fusing part of the wire electrode by the tension applying means for applying a tension and the tension applying means and the wire fusing means. And a control means for controlling so.

[0010]

Embodiments Next, embodiments embodying the present invention will be described with reference to FIGS. A machining tank 2 is placed on a base 1 of a wire electric discharge machine, and a workpiece W fixed and placed on a work table 3 fixed to the machining tank 2 in the machining tank 2. Is immersed in an insulating processing liquid (fresh water or oil) 5. The processing liquid 5 is supplied from the processing liquid supply device 4, and the processing liquid 5 polluted by the processing is collected by the processing liquid supply device 4, filtered through a filter or the like, and then circulated again to be supplied.

Further, between the base 1 and the processing tank 2 is shown in FIG.
XY for moving the workpiece W on the XY plane as shown in
A table 6 is arranged and driven and controlled by a drive mechanism (not shown). At the top of column 7, wire electrode 8
A wire bobbin 9 wound around the upper nozzle 1 is attached to the upper arm 10 supported on the upper portion of the column 7.
1 is formed. Further, a lower nozzle 13 is arranged on a lower arm 12 supported on the lower portion of the column 7. The wire electrode 8 drawn out from the wire bobbin 9 is stretched from the upper nozzle 11 to the lower nozzle 13 through the workpiece W in a substantially vertical shape, and is connected to the wire electrode 8 and the workpiece W from a power source and a conduction electron (not shown). A pulse current is applied to the wire electrode 8 and electric discharge machining is performed in a minute electric discharge machining gap (electric discharge machining portion) between the wire electrode 8 and the workpiece W that pass vertically downward.

The upper nozzle 11 and the lower nozzle 13 are
The machining liquid 5 is ejected from either or both of them to the electric discharge machining section to remove metal scraps in the electric discharge machining and cool the electric discharge machining section. The diameter of the wire electrode 8 is 0.
It is as thin as 05 mm to 0.3 mm. The wire electrode 8 may be conveyed at various speeds (moving speeds) depending on the electrical discharge machining conditions, the thickness of the workpiece W, etc.
It is 300 mm / sec.

The direction changing pulley 14 is arranged below the lower nozzle 13, and a pair of upper and lower rollers 15 and 16 arranged behind the lower nozzle 13 are used by the direction changing pulley 14 to change the conveying direction in the lateral direction. The completed wire electrode 8 is forcibly sandwiched and discharged into the collection box 18 for collection. The discharging means of the present invention is composed of a pair of upper and lower rollers 15 and 16. The pair of upper and lower rollers 15,
At least one of the rollers 16 has a discharge motor 17
(See FIG. 2). During the electric discharge machining, a pre-tension for applying a predetermined pre-tension to the wire electrode 8 passing through the location of the workpiece W by the powder brake 23 as a brake mechanism described later and the pair of rollers 15 and 16. It functions as an application mechanism.

Next, the supply unit of the wire electrode 8 will be described with reference to FIGS. 2 and 3. The drive motor 20 that applies a rotational force to the wire bobbin 9 generates a rotational force in a direction opposite to the rotating direction of the wire bobbin 9 during electric discharge machining, applies a pre-tension to the wire electrode 8 during electric discharge machining, and causes a wire tension during wire breakage. A force for unwinding the electrode 8 is applied. Powder brake 2 as a brake mechanism including a rotation sensor 22
As a result of the braking force being applied to the pulley 21 connected to 3, the pulley 21 applies tension to the wire electrode 8.

As shown in FIG. 3, the direction changing table 25 is supported on the frame 24 via a pivot 26 so that the upper end thereof can swing and rotate. The wire guide 27 is provided on the frame 24 above the pivot 26, and the feed roller 28 is provided on the frame 24 below the wire guide 27. The feed roller 28 is rotated by a conveyance motor 29 composed of a step motor via a transmission mechanism such as an endless belt (not shown).

The first pinch roller 30 is the feed roller 2
8, a first pinch roller 30 is connected to a rotary plate of a rotary first solenoid 31 via a lever 33 that rotates around a pivot 32, and
When the coil of the solenoid 31 is excited, the rotary plate of the solenoid 31 rotates by a certain angle, and when the wire electrode 8 is sandwiched by the feed roller 28 by the first pinch roller 30 via the lever 33 that rotates about the pivot 32. , The wire electrode 8 is conveyed downward. When the excitation of the coil of the rotary first solenoid 31 is stopped, the built-in return spring has a self-recovery function of returning the rotary plate to the original position in the opposite direction.
A wire guide 34 is arranged on the direction changing table 25 near the pivot 26.

The wire fusing means 35 of the present invention provided on the direction changing table 25 is the holder 3 provided on the rotary support shaft 36.
9, a pair of current carrying members 37 and 38, and a rotary second solenoid 40 for rotating the holder 39 around the rotary support shaft 36. The rotary second solenoid 40 is excited to form a pair. In the state in which the conduction electrons 37, 38 of the above are in contact with the wire electrode 8, the wire electrode 8 between the conduction electrons 37, 38 is fused by the energization from the fusing power source 70 (see FIG. 5). In addition,
The rotary second solenoid 40 also has a self-recovery function like the rotary first solenoid 31.

A sensor 41 for detecting a wire electrode is provided on the direction changing table 25 below the wire fusing means 35, and wire guides 42 and 43 are provided above and below the sensor 41. Even when the wire electrode 8 is disconnected due to an accident, the pair of wire guides 42, 4
The position of the wire electrode 8 in 3 is to hold the wire electrode 8 so as not to be out of the detectable range of the sensor 41.

The feed roller 44 and the second pinch roller 45 function as a tension applying mechanism of the present invention that forms a pointed tip portion 8a of the wire electrode 8 which will be described later, and the wire electrode 8 due to an unexpected accident. It functions as a processing means at the time of disconnection. The feed roller 44 is provided on the direction changing table 25, and is rotated by a feed motor 46 including a step motor via a transmission mechanism such as an endless belt (not shown).

The second pinch roller 45 is connected to a rotary plate of a rotary third solenoid 49 having a self-recovery function similar to that described above via a lever 48 which rotates about a pivot shaft 47. When the coil is excited, the rotary third solenoid 49 rotates its rotating plate by a certain angle, and the second pinch roller 45 sends the wire electrode 8 to the roller via a lever 48 which rotates around a pivot shaft 47. When it is rotated so as to be sandwiched by 44, the wire electrode 8 is conveyed downward.

Further, the wire guide 50 is attached to the direction changing table 2.
It is provided at the lower end of 5. Rotating fourth solenoid 51
Is for swinging and rotating the direction changing table 25 to the left and right around the pivot 26, and is connected to the direction changing table 25 via a swing lever 52. When the coil of the rotary fourth solenoid 51 is excited, the rotary plate thereof is rotated by a certain angle and the swing lever 52 is pulled. As a result, the direction changing table 2 is arranged so that the lower end opening of the wire guide 50 at the lower end of the direction changing table 25 faces the upper direction of the waste box 53 of the wire electrodes.
5 rotates (see FIG. 4).

On the contrary, when the excitation of the coil of the rotary fourth solenoid 51 is stopped, the built-in return spring has a self-recovery function for returning the rotary plate to the original position in the opposite direction. Accordingly, the direction changing table 25 is arranged so that the lower end opening of the wire guide 50 faces the upper end opening of the tubular guide body 54 arranged adjacent to the waste box 53.
Position returns (see FIG. 3). The lower end of the guide body 54 is for guiding the wire electrode 8 toward the upper guide 62 during processing.

As shown in FIG. 5, a central processing unit (CPU) 55 as a control device for the wire electric discharge machine has a control program for the entire wire electric discharge machine, a control program for forming the pointed tip portion, and the like. A read-only memory (ROM) 56 in which a control program or the like for cutting and discarding the wire electrode 8 which has not been described in advance is stored, a correspondence table of wire electrode diameters and fusing current values described below, and a roller 1 for discharging.
A readable / writable memory (RAM) 57 for storing various values such as a tension value applied to the wire electrode 8, a set time value, and a machining program by 5 and 16 is connected to an interface (not shown). Further, the sensor 41 for detecting the wire electrode and the rotation sensor 22 are connected to the CPU 55, and the discharge motor 17, the drive motor 20, the powder brake 23, the conveyance motor 29, the delivery motor 46, and the rotation are connected via the drive circuit 59. Solenoid 31,
40, 49 and 51 are connected. Further, a work start switch 58 (see FIG. 5) for forming the pointed tip of the wire electrode 8 is connected to the CPU 55.

Next, in the wire electric discharge machine configured as described above, control of electric discharge machining and cutting of the wire electrode 8 after completion of electric discharge machining at one location will be described with reference to flowcharts shown in FIGS. 6 to 7. When a start button (not shown) is operated, electrical discharge machining is executed (S2) following the initial setting (S1). In this state, the drive motor 20 is provided with a rotational force that applies a pre-tension to the wire electrode 8. The value of this pre-tension is much larger than the value of the tension given by the tension applying means at the time of fusing described later. Further, since the wire electrode 8 is detected by the wire electrode detecting sensor 41, the output signal of the sensor 41 is ON. At this time, during the processing, it is always judged whether or not the wire electrode 8 is broken at the position of the workpiece W (S3).

When it is judged that the wire electrode 8 is broken (S3, yes), the discharge motor 17 is driven to collect the wire electrode 8 on the downstream side of the feeding, which is broken by the rollers 15 and 16, in the collection box. 18, while the fourth solenoid 51 is excited to change the position of the direction changing table 25 so that the lower end opening faces the waste box 53,
Wire fusing means 35 provided on the direction changing table 25
Then, the cutting / discarding control is executed in which the broken wire tip of the wire electrode 8 on the upstream side of the wire feed is cut by a predetermined length, and the cut portion is sent toward the waste box 53. Then, the excitation of the fourth solenoid 51 is stopped, the direction changing table 25 is returned to the original state as shown in FIG. 3, and the wire electrode 8 is sent downward by the carrying motor 29 and the sending motor 46,
The machining liquid 5 is jetted from the upper nozzle 11 to reconnect the wire electrode 8 (S4).

On the other hand, when the wire 8 is not broken (S3, no), the control of the electric discharge machining is continued (S).
2). Then, it is determined whether or not the electric discharge machining at one location is completed (S5). If it is determined that the electric discharge machining has been completed (S5, yes), in preparation for the next electric discharge machining,
Control is performed to melt and cut the wire electrode 8 on the upstream side of the work W to be fed, and to form the tip of the wire electrode 8 into a pointed shape (S6). In the electric discharge machining operation accompanied by the worker, the operation of forming the tip portion of the wire electrode 8 may be started by pressing the switch 58.

FIG. 7 shows a subroutine flow chart of control for fusing the wire electrode 8 to form a pointed tip. First, the powder brake 23 is turned on, the third solenoid 49 is turned on (excitation), the delivery motor 46 is turned on to rotate forward (S71), the second solenoid 40 is turned on immediately after that, and the fusing power source 70 is almost simultaneously turned. Turn on (S7
2). When the powder brake 23 is turned on, the feeding upstream side of the wire electrode 8 is held, and when the third solenoid 49 is turned on, the wire electrode 8 can be held between the feeding roller 44 and the second pinch roller 45. The forward rotation of the delivery motor 46 causes the delivery roller 44 to rotate in the forward direction, so that tension is applied to the wire electrode 8 toward the downstream side of the delivery. The tension at this time is 500 g, regardless of the diameter of the wire electrode 8. Further, by turning on the second solenoid 40, the conduction electrons 37, 38 are pressed in the vicinity of the fusing point of the wire electrode 8. Then, when the fusing power source 70 is turned on, a fusing current flows through the wire electrode 8 between the pair of conducting electrons 37, 38, and the fusing is performed. The optimum fusing current value at this time is, according to various embodiments, the diameter (0.1, 0.15, 0.2) of the wire electrode 8.
0,0.25,0.30) mm, (1.5,2.0,4.0,5.0,
7.0) It is A.

Next, in steps S71 and S72, a predetermined tension is applied to the wire electrode 8 and a fusing current is applied, and the wire electrode 8 is held for a predetermined time T1 (S73). This fixed time is the time from when a fusing current is applied until the wire electrode 8 is actually blown, and the tip 8a of the blown wire electrode 8 has a tapered shape without bending as shown in FIG. This is the time required for fusing under the above-mentioned optimum fusing conditions (tension value and fusing current value). This fixed time T
1 is constant regardless of the diameter of the wire electrode 8. According to the experiment, about 3 seconds was optimal.

Immediately after the elapse of the predetermined time T1, the discharge motor 17 is immediately rotated forward (S74). By the rotation of the discharge motor 17, the part of the wire electrode 8 that has been melted and separated and located on the downstream side of the feeding is sandwiched by the rollers 15 and 16 and begins to be discharged to the recovery box 18. In this state, the feed roller 44 as the tension applying means and the second pinch roller 4
5, the wire electrode 8 is sandwiched, and the delivery motor 46
Is also in a driving state. However, since the driving force of the discharging motor 17 is larger than that of the discharging motor 46, substantially the same tension as the pre-tension value at the time of electric discharge machining is applied to the wire electrode 8. Therefore, the pair of the feed roller 44 and the second pinch roller 45, the roller 15,
The wire electrode 8 between the 16 pairs does not loosen, and the wire electrode 8 can be smoothly discharged without buckling in the gap between the wire guides 62, 63 and the processed portion of the workpiece W.

Next, at step S75, it is judged if the sensor 41 is turned off, that is, if the wire electrode 8 is cut. Here, if the sensor 41 is not turned off, the end portion of the cut wire electrode 8 on the downstream side of the feeding is the sensor 4
Since the point 1 has not passed, the drive of the discharge motor 17 is continued. When the sensor 41 is turned off in step S75, the second solenoid 40 is turned off and the fusing power source 70 is turned off (S76). By turning off the second solenoid 40, the contacts 37, 38 with the wire electrode 8 are released at the fusing portion.

Next, in step S77, a fixed time (T
2) Just wait. During the waiting time (T2), the discharge motor 17 continues to be driven. The fixed time (T2) is
Of the cut wire electrode 8, the feeding downstream side (workpiece W
(Side) is the time until all the parts are collected in the collection box 18, and is appropriately set from the distance from the fusing part to the collection box 18 and the discharge speed of the wire electrode 8 by the rollers 15 and 16. The fixed times T1 and T2 are stored in the readable / writable memory (RAM) 57 in advance at any time.

After the elapse of the predetermined time (T2), the third solenoid 49 is turned off, and the feed motor 46 and the discharge motor 1
7 is stopped (S78), and the control for forming the pointed tip portion is ended. The rotary solenoid 3
It goes without saying that 1, 40, 49 may be replaced by a direct-acting electromagnetic solenoid, and the wire fusing means may be of another type.

[0033]

As described in detail above, the present invention provides a discharge means for discharging a wire electrode during electric discharge machining while applying a pre-tension between the feed side and the discharge side, and a wire electrode. A wire fusing means for applying a fusing current to the fusing part, a tension applying means for applying a tension between the wire electrode feeding upstream side and the workpiece at the time of fusing the wire electrode, and the tension applying means and the wire. By applying a predetermined tension and a fusing current to the fusing part of the wire electrode for a certain period of time by the fusing means, it is possible to provide the fusing part of the wire electrode with an optimum tension for forming a tip portion having an appropriate shape. .. Then, since the wire electrode is controlled to be discharged by the discharging means after the elapse of the predetermined time, the wire is ejected to the outside of the machine at a good timing and without causing slack in the wire electrode on the downstream side of the feed after fusing. The electrode can be ejected. As a result, the remarkable effect that the used wire electrode can be collected without damaging the parts of the electric discharge machine or the work piece while the shape of the tip of the wire electrode can be formed in an optimum shape Is played.

[Brief description of drawings]

FIG. 1 is a schematic side view of a wire electric discharge machine.

FIG. 2 is a side sectional view of a wire electrode cutting and collecting unit.

FIG. 3 is a side cross-sectional view of a wire electrode cutting and collecting unit during electric discharge machining.

FIG. 4 is an explanatory diagram showing a state in which the position of the direction changing table is changed.

FIG. 5 is a block diagram showing a control device.

FIG. 6 is a flowchart of control.

FIG. 7 is a flowchart of a control subroutine.

FIG. 8 is a diagram showing a tip portion of a wire electrode in a defective state.

FIG. 9 is a diagram showing an appropriate shape of the tip portion of the wire electrode.

[Explanation of symbols]

 15, 16 Roller 17 Discharge motor 20 Drive motor 23 Powder brake 27, 34, 42, 43, 50 Wire guide 31, 40, 49, 51 Solenoid 35 Wire fusing means 37, 38 Conductor 41 Sensor 46 Sending motor 55 Central processing unit (CPU) 56 Read-only memory (ROM) 57 Read / write memory (RAM) at any time

Claims (1)

[Claims] 1. A wire electric discharge machine for machining a workpiece by applying a machining electric discharge pulse to an electric discharge machining gap between the wire electrode and the workpiece, and feeding the wire electrode to the wire electrode during electrical discharge machining. Discharge means for discharging while applying a pre-tension between the discharge side and the discharge side, a wire fusing means for applying a fusing current to a fusing part of the wire electrode, a feed upstream side of the wire electrode and a workpiece. In between, a tension applying means for applying a tension at the time of melting the wire electrode, and by the tension applying means and the wire fusing means, after a lapse of a fixed time of applying a predetermined tension and a fusing current to the fusing part of the wire electrode, A device for cutting a wire electrode in a wire electric discharge machine, comprising: a control unit that controls the discharge unit to discharge the wire electrode.