JP4550615B2 - Automatic wire electrode connection method - Google Patents

Description

  The present invention relates to a wire electrode automatic connection method for automatically stretching a wire electrode between upper and lower wire guides in wire cut electric discharge machining. Specifically, the present invention relates to an automatic wire electrode connection method in which a wire electrode is automatically inserted through a lower wire guide in a working fluid and the wire electrode is stretched.

  In wire-cut electrical discharge machining, a machining voltage is applied to a machining gap formed by a wire electrode stretched between a pair of wire guides and the workpiece to cause repeated discharge, and the workpiece is cut by the discharge energy. This is a processing method for processing. In a general wire cut electric discharge machining apparatus, wire guides are provided above and below with a workpiece interposed therebetween. Therefore, it is necessary to stretch the wire electrode between the upper and lower wire guides before processing. In order to reduce the burden on the operator and improve the work efficiency, many wire cut electric discharge machining apparatuses are equipped with an automatic wire connection device that automatically stretches a wire electrode between upper and lower wire guides.

  Among the methods for guiding a wire electrode when passing the wire electrode through a pair of wire guides, a method adopted in many automatic wire-bonding devices is that a liquid jet such as a machining liquid is directed to the direction in which the wire electrode is sent out. In this method, the wire electrode is guided from one wire guide to the other wire guide while being supplied coaxially and constraining the wire electrode with a liquid jet. In particular, a method of guiding only the liquid jet from the outlet of one wire guide to the other wire guide is called a jet method. A method of guiding the inlet of the machining start hole or the other wire guide to the guide pipe and a liquid jet supplied into the guide pipe is called a pipe jet method.

  In the wire-cut electric discharge machining method in which the workpiece is immersed in the machining fluid for electrical discharge machining, the upper and lower wire jet nozzle openings and the upper and lower wire guides provided as close as possible to the workpiece are being processed. Soaked in machining fluid. If the machining tank is filled with the machining fluid to the height at which the workpiece is immersed, the machining head and the equipment around the machining head cannot be submerged in the machining fluid. There is a limit to the distance at which the wire guide can approach. In particular, the upper wire guide that is separated from the lower wire guide by a length corresponding to the plate thickness of the workpiece, for example, when interference occurs between the stepped workpiece or the fixture and the upper wire guide. There are cases in which it is not possible to approach the lower wire guide any further. Therefore, when a liquid jet is supplied from the nozzle for automatic connection incorporated in the upper guide assembly and the wire electrode is restrained by the liquid jet to pass the wire electrode through the lower wire guide, the liquid jet is generated with a considerable liquid pressure. Even if is supplied, the momentum of the liquid jet rapidly declines due to the resistance of the machining fluid, the force that restrains the wire electrode is weakened, the straightness is lost, and the force that helps propel the wire electrode is lost. It becomes difficult to pass through the lower wire guide (see FIG. 4A).

  In the case where the guide pipe can reach the entrance of the lower wire guide, the wire electrode can be inserted almost without any problem. However, in actual processing, such a case is relatively rare. Further, in the jet method using a die guide through which the guide pipe cannot pass, the guide pipe cannot be lowered to the entrance of the lower wire guide. When using a relatively rigid wire electrode or annealing the wire electrode before insertion, the straightness of the wire electrode is slightly improved, but in practice, the plate thickness of the workpiece is extremely high. Limited when small. For this reason, when inserting the wire electrode, once the machining fluid is discharged and the wire electrode is inserted without the machining fluid, the machining fluid is supplied again to a height that satisfies the workpiece. Have been to.

  In order to automatically perform all wiring operations, the machining fluid must be discharged and re-supplied automatically. Generally, the NC program or the detection signal from the disconnection detector is used when discharging the machining fluid. Automatically lowers the weir plate of the processing tank or opens the discharge port, and simultaneously opens the drain control valve to discharge the processing liquid. When the processing liquid is resupplied, the liquid level is detected by moving together with the upper guide assembly. The machining fluid is supplied until the device detects the machining fluid. In addition, since the time required for the entire wiring work becomes longer due to the discharge and resupply of the machining fluid, the machining efficiency is lowered.For example, when the machining fluid is drained, all the machining fluid is not drained to the height of the work stand. It is considered to shorten the time by supplying the machining liquid to a required height at the time of supplying the machining liquid. In addition, the machining fluid is discharged while raising and lowering the machining tank, so that the amount of machining fluid discharged per unit time is increased, and the wiring work can be performed in parallel with the discharge and re-supply of the machining fluid. It is also considered to improve (see Patent Document 1).

  In addition, the machining head is raised and the upper nozzle ejection opening is taken out of the machining liquid and then the liquid jet is supplied, so that the liquid jet flows into the machining liquid and the attenuation of the momentum of the liquid jet is suppressed. (See FIG. 4B). In addition, a method of improving the success rate of automatic connection in machining fluid by advancing the wire electrode by sucking the machining fluid from the lower nozzle and generating a strong water flow in the lower hole to suck the wire electrode into the lower nozzle. Has been proposed. Thus, by enabling automatic connection in the working fluid, the time required for automatic connection can be shortened (see Patent Document 2).

JP 11-77435 A (page 7) JP-A-1-205931 (page 2)

  When automatic connection is performed in the absence of a working fluid, the insertion of the wire electrode into the lower wire guide is rarely failed, and in recent years, the success rate of the final automatic connection has reached almost 100%. On the other hand, in the method of performing automatic connection in the machining fluid that has been considered so far, the insertion often fails compared to the case of performing automatic connection in the absence of machining fluid, and sometimes it is repeatedly inserted many times. The actual situation is that the time required for automatic connection has not been shortened so much in view of the whole process of automatic connection. In addition, there is often a case where the automatic connection cannot be finally made and the work must be interrupted. For this reason, when wire cut electrical discharge machining is performed by immersing the workpiece in the machining fluid, the machining fluid is once drained and automatic connection is performed without the machining fluid, even if the time for one insertion operation is somewhat longer. It is advantageous.

  The main reason for the failure to insert the wire electrode in the machining fluid is that the momentum of the jet in the machining fluid is attenuated and the wire electrode cannot be restrained sufficiently and cannot be fed straight out. Although the success rate of insertion is improved even if an auxiliary action is added by sucking in, etc., unless the restraint force and straightness of the wire electrode of the liquid jet supplied from the upper nozzle are sufficiently exhibited, The disadvantageous situation is not improved as compared with the method of draining the machining fluid and performing the insertion work without the machining fluid.

  In view of the above-described problems, the present invention provides a wire electrode automatic connection that improves the success rate of the wire electrode insertion in the machining liquid by sufficiently exerting the restraint force and straightness of the wire electrode of the liquid jet in the machining liquid. It aims to provide a method.

In order to solve the above-described problem, the wire electrode automatic wire connection method of the present invention surrounds the wire electrode in the wire electrode automatic wire connection method in which the wire electrode is inserted into the lower wire guide in the working fluid. A liquid jet is supplied coaxially with the direction of feeding the wire electrode from the nozzle for automatic connection, and compressed air is supplied in the same direction as the liquid jet coaxial with the direction of feeding the wire electrode from the processing nozzle arranged outside the nozzle for automatic connection. The liquid jet is covered with compressed air, the wire electrode is restrained by the liquid jet surrounded by the compressed air, and the wire electrode is sent out and inserted into the lower wire guide, and the lower wire guide is inserted. The wire electrode inserted in is taken up by the take-up roller.

  Since the periphery of the liquid jet column for propelling while constraining the wire electrode is covered with compressed air flowing in the same direction as the liquid jet along the liquid jet, the liquid jet is in the initial stage immediately after being injected from the connection nozzle With the momentum, the surrounding air is drawn in with the compressed air while surrounding air is involved. Therefore, even if the liquid jet reaches a deep position in the machining liquid, air still exists around the liquid jet column. Therefore, even in the machining fluid, the liquid jet does not lose much momentum, and the liquid jet column does not spread as in the air, and is in a straight state, and the workpiece has a large plate thickness between the upper and lower wire guides. Even if the distance is long, a sufficient force for propelling straightly while restraining the wire electrode is maintained. As a result, the failure of inserting the wire electrode in the machining fluid can be greatly reduced, and the effect of improving the work efficiency of automatic connection can be obtained.

  First, a suitable wire-cut electric discharge machining apparatus capable of implementing the wire electrode automatic wire connecting method of the present invention will be described. FIG. 1 shows an example of the overall configuration of a wire cut electric discharge machining apparatus. FIG. 2 shows an upper guide assembly of the wire cut electric discharge machining apparatus shown in FIG. FIG. 3 shows an upper nozzle and a connection nozzle of the upper guide assembly shown in FIG.

  The wire cut electric discharge machining apparatus includes a machining power supply device (not shown) that supplies a machining current to a machining gap formed by the wire electrode 1 and the workpiece 2. The wire-cut electric discharge machining apparatus has a pair of wire guides provided above and below the workpiece 2. As shown in FIG. 2, the upper guide assembly 3 includes an upper wire guide (die guide) 31 that positions and guides the wire electrode 1, an upper energizer 32 that is connected to the machining power supply device and supplies power to the wire electrode 1, An upper nozzle 33 which is a machining nozzle for supplying a machining liquid jet to a machining site therein, and a connection nozzle 34 for supplying a liquid jet for guiding the wire electrode 1 during automatic connection are provided. The lower guide assembly 4 incorporates a lower wire guide, a lower electric current body, and a lower nozzle (not shown). The lower wire guide is substantially the same as the shape of the upper wire guide, and its inlet side is formed in a mortar shape, and is configured to guide the wire electrode to the center of the guide body.

  The wire-cut electric discharge machining apparatus includes a supply mechanism 5 for supplying the wire electrode 1 to a machining site, an automatic connection device 6 for automatically stretching the wire electrode 1 between upper and lower wire guides, and a wire electrode 1 used for machining. Is collected to the take-up roller and collected in a bucket. The feed roller 51 of the supply mechanism 5 feeds the wire electrode 1 to the processing site during processing. Further, the delivery roller 51 winds and feeds the wire electrode 1 that is intentionally cut or unintentionally disconnected during automatic connection. The winding roller 71 of the collection mechanism 7 winds up the used wire electrode that has been used for processing. The feeding roller 51 and the winding roller 71 cooperate to apply a predetermined tension to the wire electrode 1 during processing. The supply mechanism 5 and the recovery mechanism 7 can employ various configurations as long as they do not directly contradict the operational effects of the present invention, and detailed description thereof will be omitted.

  The automatic connection device 6 mainly includes a guide unit 10 including a guide pipe 11 that guides the wire electrode 1, a processing liquid supply unit 20 that introduces a processing liquid into the guide pipe 11, and the wire electrode 1 during automatic connection. It comprises a roller unit 30 for clamping and a tip processing unit 40 for adjusting the tip of the wire electrode 1 during automatic connection. The roller of the roller unit 30 can slightly wind and feed the wire electrode 1, or has a function of guiding the wire electrode 1 to the guide pipe 11. The tip processing unit 40 includes a cutting device 41 that cuts the tip portion of the wire electrode 1, a gripping device 42 that clamps and transports a cut piece of the wire electrode 1 that is cut by the cutting device 41, and a gripping device 42 that transports the tip processing unit 40. And a storage box 43 for storing a cut piece of the wire electrode 1 to be processed.

  The jet supply device 8 supplies a processing liquid having a predetermined pressure to the upper and lower processing nozzles during processing. The upper nozzle 33, which is a processing nozzle, has an ejection opening (nozzle cap) 35 having a circular horizontal section, and processes a machining liquid jet formed in a cylindrical shape coaxially in the direction (vertical direction) in which the wire electrode 1 is delivered. The spray is supplied to the site. Further, the jet supply device 8 supplies a liquid having a predetermined pressure such as a processing liquid to the guide pipe 11 through the processing liquid supply unit 20 during automatic connection, and a connection nozzle 34 provided in the upper guide assembly 3. A liquid having a predetermined pressure is supplied to the. The connection liquid jet ejected from the connection nozzle 34 restrains the wire electrode 1 when the wire electrode 1 is sent out in the automatic connection, and maintains the straightness of the wire electrode 1. Further, the liquid jet for connection gives a propulsive force to the wire electrode 1 when the wire electrode 1 is sent out during automatic connection.

  As shown in FIG. 3, the connection nozzle 34 is provided on the inner side of the upper nozzle 33, and is provided with an ejection opening having a circular horizontal section concentric with the upper nozzle 33 and having a diameter smaller than that of the upper nozzle 33. The wire electrode 1 is sent out from substantially the center of the ejection opening. The liquid of a predetermined pressure supplied from the jet supply device 8 to the connection nozzle 34 is narrowed down through the flow path 36 formed in the connection nozzle 34 and is directed downward in the direction in which the wire electrode 1 is sent out. Is injected into. Therefore, the connecting liquid jet jetted from the connecting nozzle 34 has a thinner liquid jet column and a diameter larger than the diameter of the wire electrode 1 as compared with the working liquid jet supplied from the upper nozzle 33 which is a processing nozzle. The periphery of the wire electrode 1 is covered so as to be wrapped. Further, the liquid jet for connection is stronger in straightness because the force of the jet is stronger than the machining liquid jet.

  The air supply device 9 is particularly provided for carrying out the wire cut electric discharge machining method of the present invention. The upper nozzle 33 serves both as a jet nozzle that ejects a machining fluid jet and an air nozzle that ejects compressed air. The compressed air from the air supply device 9 is supplied to the upper nozzle 33 through a supply path different from the flow path of the machining liquid from the jet supply device 8. The path for introducing the machining fluid and the path for introducing the compressed air in the upper nozzle 33 are provided separately, and as shown in FIG. 3, they are opened and merged in the reservoir space 37 of the upper nozzle 33. For example, a check valve is provided in the middle of the supply pipe that supplies the compressed air to the upper nozzle 33 to prevent the machining fluid supplied to the upper nozzle 33 from flowing back to the supply pipe that supplies the compressed air. is doing.

  Next, the process of the wire electrode automatic connection method according to the present invention will be specifically described by taking as an example a case where the wire electrode is disconnected while the workpiece is immersed. At this time, the working fluid is water having a specific resistance value required for wire-cut electric discharge machining or water appropriately mixed with an additive suitable for wire-cut electric discharge machining, and is a liquid with a predetermined pressure supplied from a jet supply device. Is the working fluid.

  As soon as the disconnection detector detects that the wire electrode 1 is disconnected, the delivery roller 51 is stopped. At the same time, the supply of the machining energy from the machining power supply device and the supply of the machining liquid jet from the upper and lower nozzles are stopped. A used portion of the wire electrode 1 that has been disconnected and fed from the processing site to the lower wire guide side is wound up by the winding roller 71. The unused portion remaining on the upper wire guide 31 side from the processed portion of the disconnected wire electrode 1 is wound up to a position where the tip of the wire electrode 1 is detected by the tip detector by the feed roller 51. The leading end portion of the wound wire electrode 1 is gripped by the gripping device 42 and cut by the cutting device 41. The cut pieces of the wire electrode 1 generated by the cutting are transferred to the storage box 43 while being clamped by the gripping device 42 and collected.

  When the cut piece of the wire electrode 1 is removed and the tip is trimmed, a working fluid having a predetermined pressure is supplied from the jet supply device 8 through the working fluid supply unit 20 to the guide pipe 11 in the direction of feeding the wire electrode 1. At this time, normally, the ejection opening 35 of the upper nozzle 33 and the ejection opening of the connection nozzle 34 inside the upper nozzle 33 are immersed in the processing liquid. In the automatic connection method of the present invention, the insertion work can be performed in this state. Although it is disadvantageous in terms of time, in order to make it easier to ensure the momentum of the liquid jet for connection, the processing head is moved to raise the upper guide assembly, and the liquid jet is supplied from the connection nozzle 34. At least the ejection opening of the connection nozzle 34 can be positioned above the processing liquid level.

  When the cut piece of the wire electrode 1 is removed, the remaining wire electrode 1 has a tip protruding from the length guide pipe 11 to the cutting device 41. In this state, the guide pipe 11 is lowered so that the tip of the wire electrode 1 fits in the guide pipe 11 or slightly protrudes. Then, the guide pipe 11 is lowered as it is, and the feeding roller 10 is operated to feed the wire electrode 1 in synchronization with the lowering of the guide pipe 11 so that the state where the wire electrode 1 is in the guide pipe 11 is maintained. The delivered wire electrode 1 is guided to the upper wire guide 31 by the guide pipe 11 and the machining liquid supplied to the guide pipe 11. Since the illustrated upper wire guide 31 is a die guide, the guide pipe 11 stops at the entrance of the upper wire guide 31. The wire electrode 1 passes through the wire guide 31 while being guided by the machining liquid jet that is fed out as it is and ejected from the outlet of the guide pipe 11.

  At this time, a processing liquid having a predetermined pressure is supplied from the jet supply device 8 to the connection nozzle 34 incorporated in the upper guide assembly 3, and the wire electrode 1 is sent out from the automatic connection nozzle 34 so as to surround the wire electrode 1. Supply the machining fluid jet coaxially with the direction. At the same time, the upper nozzle 33 is a processing nozzle that is disposed outside the connection nozzle 34 so as to surround the connection nozzle 34 and has a jet nozzle that is concentric with the connection nozzle 34 and has a circular cross section with a larger diameter than the connection nozzle 34. Compressed air is supplied coaxially in the direction in which the wire electrode 1 is fed out, and the periphery of the machining fluid jet for connection supplied by the connection nozzle 34 is covered with compressed air. Then, the tip of the wire electrode 1 that has passed through the upper wire guide 31 passes through the ejection opening of the connection nozzle 34 and is captured in the connection working fluid jet.

  The wire electrode 1 riding on the machining fluid jet for connection is constrained by the machining fluid jet column for connection, and is propelled in the direction in which the machining fluid jet flows by the force of the machining fluid jet to give straightness. At this time, the compressed air ejected from the upper nozzle 33 which is a processing nozzle is sent out coaxially with the direction in which the wire electrode 1 is sent out, in other words, in the same direction as the machining fluid jet for connection. For this reason, the machining fluid jet for connection forms a straight machining fluid jet column without being disturbed. At this time, as in the situation shown in FIG. 4B, the machining fluid jet for connection involves surrounding air when entering the machining fluid, but compressed air is also ejected in the same direction as the machining fluid jet for connection. As a result, not only the momentum of the machining fluid jet but also the momentum of the compressed air is energized when it is caught in the machining fluid jet for connection, and the machining fluid jet is encased in the compressed air together with the compressed air. It is sent deep inside.

  Therefore, air exists in the periphery of the machining fluid jet for connection even in the depth of the machining fluid, and the same situation as in the air is created even though it is in the machining fluid. Therefore, the machining liquid jet maintains the force that restrains the wire electrode 1 in the machining liquid, and has straight advanceability, and tries to feed the wire electrode 1 in the lower wire guide direction. Since the feed roller 51 continues to feed the wire electrode 1, the wire electrode 1 is guided by the machining liquid jet and reaches the lower wire guide through the opening of the lower nozzle. Since the machining fluid jet for connection forms a machining fluid jet column slightly larger than the diameter of the wire electrode 1 and surrounds the wire electrode 1, the machining fluid jet for connection is disturbed at the entrance of the lower wire guide. The wire electrode 1 can be smoothly guided to the lower wire guide without any problem, and the wire electrode 1 can pass through the lower wire guide together with the machining liquid jet for connection. In this manner, the wire electrode is fed out and inserted into the lower wire guide while supplying the machining fluid jet from the automatic connection nozzle and supplying the compressed air from the machining nozzle. The wire electrode 1 inserted through the lower wire guide is transported by the transport device of the recovery mechanism 7 and is captured by the winding roller 71.

  The present invention is applied to an automatic connection device of a wire cut electric discharge machining apparatus. According to the present invention, even when wire-cut electric discharge machining is performed in a machining fluid, the wire electrode can be automatically inserted and connected with a very high success rate in the machining fluid without removing the machining fluid. This will greatly improve work efficiency and contribute to improving the processing efficiency and productivity of precision molds and precision parts.

It is a whole lineblock diagram showing an example of a wire cut electric discharge machine which carries out an automatic wire electrode wiring method of the present invention. It is sectional drawing which shows the structure of the upper guide assembly of the wire cut electric discharge machining apparatus shown by FIG. FIG. 3 is a cross-sectional view showing an upper nozzle and a connection nozzle in the upper guide assembly shown in FIG. 2. It is a schematic diagram which shows the method of sending out a wire electrode in the conventional process liquid.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wire electrode 2 Work piece 3 Upper guide assembly 31 Upper wire guide 32 Upper electric current body 33 Upper nozzle 34 Connection nozzle 4 Lower guide assembly 5 Supply mechanism 51 Feed roller 6 Automatic connection device 7 Recovery mechanism 71 Take-up roller 8 Jet supply Device 9 Air supply device 10 Guide unit 11 Guide pipe 20 Processing fluid supply unit 30 Roller unit 40 Tip processing unit 41 Cutting device 42 Holding device 43 Storage box

Claims (1)

In a wire electrode automatic connection method in which a wire electrode is inserted into a lower wire guide in a processing liquid, a liquid jet is supplied coaxially with a direction in which the wire electrode is fed from an automatic connection nozzle so as to surround the wire electrode. In addition, the compressed air is supplied in the same direction as the liquid jet coaxially with the direction in which the wire electrode is sent out from the processing nozzle disposed outside the nozzle for automatic connection, and the periphery of the liquid jet is covered with the compressed air The wire electrode is sent out while being constrained by the liquid jet surrounded by the compressed air and inserted into the lower wire guide, and the wire electrode inserted into the lower wire guide is used as a winding roller. A method for automatically connecting wire electrodes to be captured.

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