Wire electric discharge machine

Abstract

The wire EDM machine (10) that processes the workpiece (W) by generating a discharge from the wire electrode (60) includes an upper wire conductor (64), a roller (78) for feeding the wire electrode, a piping (110) for inserting the wire electrode and for supplying refrigerant, a positive electrode (132) and a negative electrode (134) of the wire electrode that contact the wire electrode between the piping and the upper wire conductor when the wire electrode is fed out in a spaced-out manner, and a power supply (140) that applies a cutting-off voltage between the positive electrode and the negative electrode when the wire electrode is cut off.

Description

[Technical Field]

[0001] This invention relates to a wire electrical discharge machining (EDM) machine. [Previous Technology]

[0002] Japanese Patent Publication No. Hei 06-304819 discloses a wire electrical discharge machining (EDM) machine that cuts a metal wire electrode by Joule heating between a first and a second metal wire cutting electrode. A metal wire delivery tube structure is provided between the first and second metal wire cutting electrodes. The interior of the metal wire delivery tube structure is continuously cooled with cooling water. Since an annealing effect on the metal wire electrode can be obtained inside the metal wire delivery tube structure, the curling of the metal wire electrode can be suppressed. [Summary of the Invention]

[0003] The wire EDM machine disclosed in Japanese Patent Publication No. Hei 06-304819 has the problem of poor straightness after the metal wire electrode is cut when the metal wire electrode is relatively thin.

[0004] The purpose of this invention is to solve the above-mentioned problems.

[0005] One aspect of the present invention is a wire EDM machine for processing a workpiece by generating a discharge from a wire electrode. The machine includes a wire conductor supporting the wire electrode above the workpiece, a roller that feeds the wire electrode from above the wire conductor to the wire conductor, a piping through which the wire electrode fed from the roller is inserted and through which a refrigerant flows, a positive electrode and a negative electrode of the wire electrode that are in contact between the piping and the wire conductor when the wire electrode is fed out in a spaced-apart manner, and a power supply that applies a cutting-off voltage between the positive electrode and the negative electrode when the wire electrode is cut off.

[0006] According to the present invention, the straightness of relatively thin metal wire electrodes can be well maintained after cutting.

[0007] The above-mentioned objectives, features and advantages should be readily understood from the following description of the embodiments with reference to the attached drawings.

Implementation Method

[0011] Figure 1 is a diagram showing the structure of a wire electrical discharge machining (EDM) machine 10 according to one embodiment. The X, Y, and Z directions shown in Figure 1 are orthogonal to each other, with the Z direction representing the direction of gravity. The EDM machine 10 includes a body 20, a processing power supply 30, and a control device 40. The processing power supply 30 applies a voltage to the electrode space formed between the wire electrode 60 and the workpiece (not shown in the figure) to generate a discharge. The workpiece is supported on a platform 62. The EDM machine 10 discharges the wire electrode 60 between the electrodes to perform EDM processing on the workpiece.

[0012] During electrical discharge machining, the wire EDM machine 10 moves the wire electrode 60 relative to the workpiece along a machining path specified by a predetermined program. The relative movement of the wire electrode 60 and the workpiece is performed, for example, by moving the stage 62.

[0013] The wire EDM machine 10 has an upper wire guide 64 and a lower wire guide 66. The upper wire guide 64 includes an upper guide block 68, an upper small block guide 70, and an upper nozzle (not shown). The lower wire guide 66 includes a lower guide block 72, a lower small block guide 74, and a lower nozzle (not shown). The upper wire guide 64 is located above the stage 62 and the workpiece (+Z direction) and supports the wire electrode 60. The lower wire guide 66 is located below the stage 62 (–Z direction) and supports the wire electrode 60.

[0014] The metal wire electrode 60 is supplied from the metal wire winding tube 76 in the delivery direction at a predetermined speed. The metal wire electrode 60 is delivered via roller 78, upper metal wire guide 64, and lower metal wire guide 66. Roller 78 includes a guide roller (not shown), a brake roller 80, and a first pressure roller 82. Roller 78 delivers the metal wire electrode 60 to the upper metal wire guide 64 from above. The metal wire electrode 60 is held by the second pressure roller 84 and the feed roller 86. The metal wire electrode 60 is recovered in the recovery box 88.

[0015] During wire EDM, the machining tank 90 may also store machining fluid. At this time, the stage 62, the workpiece, the upper wire conductor 64, and the lower wire conductor 66 are immersed in the machining fluid. The machining tank 90 is provided on the base 92.

[0016] The control device 40 controls the main body 20 to perform the above-mentioned electrical discharge machining. When the workpiece is changed after the electrical discharge machining is completed, the control device 40 controls the main body 20 to cut and connect the metal wire electrode 60. When the processing position of the workpiece is changed, the metal wire electrode 60 is also cut and connected. Furthermore, if the metal wire electrode 60 breaks during the electrical discharge machining, it is also cut and reconnected at a position above the break point.

[0017] Figure 2 is an illustration of the state in which a cutting voltage is applied to the metal wire electrode 60. Figure 2 shows the workpiece W mounted on the stage 62. The upper metal wire conductor 64 supports the metal wire electrode 60 above the workpiece W.

[0018] The metal wire electrode 60, fed from the roller 78 to the upper metal wire guide 64, is inserted into the piping 110. Refrigerant flows through the piping 110. When the metal wire electrode 60 is cut off, the roller 78 rotates in the opposite direction to when the metal wire electrode 60 is fed out, pulling the metal wire electrode 60 upward and applying tension to the metal wire electrode 60.

[0019] When the metal wire electrode 60 is cut, the positive electrode 132 and the negative electrode 134 are driven by the drive mechanism 136 and respectively contact the metal wire electrode 60 below the piping 110. The positive electrode 132 and the negative electrode 134 contact the metal wire electrode 60 with a distance between them in the direction of the metal wire electrode 60's delivery. The positive electrode 132 and the negative electrode 134 contact the metal wire electrode 60 between the piping 110 and the upper metal wire conductor 64. The metal wire electrode 60 and the positive electrode 132 are in contact at contact position PA. The metal wire electrode 60 and the negative electrode 134 are in contact at contact position PB.

[0020] The positive terminal of the power supply 140 is connected to the positive electrode 132. The negative terminal of the power supply 140 is connected to the negative electrode 134. The power supply 140 applies a cutting voltage between the positive electrode 132 and the negative electrode 134. The metal wire electrode 60 is cut off by the Joule heat generated between the contact position PA of the positive electrode 132 and the contact position PB of the negative electrode 134.

[0021] The control device 40 includes a processing circuit 200 and a memory unit 210. The processing circuit 200 includes a processor such as a CPU. The memory unit 210 includes volatile memory such as RAM, and non-volatile memory such as ROM and flash memory. The memory unit 210 stores programs, etc. The processing circuit 200 executes the program to realize the processing control unit 220, the drive control unit 222, and the power cut-off control unit 224. At least a part of the processing control unit 220, the drive control unit 222, and the power cut-off control unit 224 can also be implemented using an ASIC, FPGA, or other integrated circuits.

[0022] During electrical discharge machining (EDM) of the workpiece W, the machining control unit 220 controls a motor (not shown in the diagram) to feed the metal wire electrode 60 from the upper metal wire guide 64 to the lower metal wire guide 66. The machining control unit 220 controls the motor (not shown in the diagram) to move the metal wire electrode 60 relative to the workpiece W. The machining control unit 220 controls the machining power supply 30 to generate discharge between the electrodes.

[0023] The drive control unit 222 controls the drive mechanism 136 to bring the positive electrode 132 and the negative electrode 134 into contact with the metal wire electrode 60, respectively. The power cut-off control unit 224 controls the power cut-off unit 140 to apply a cut-off voltage between the positive electrode 132 and the negative electrode 134. Joule heating is generated between the contact position PA and the contact position PB.

[0024] When using, for example, the prior art disclosed in Japanese Patent Publication No. Hei 6-304819, Joule heating is also generated in the section through which the piping 110 is inserted. In the piping 110, the refrigerant flows along the metal wire electrode 60. Therefore, in the section through which the piping 110 is inserted, the metal wire electrode 60 is cooled. Consequently, an annealing effect can be obtained in this section, and the straightness of the cut metal wire electrode 60 can be expected to be improved.

[0025] However, when the diameter of the metal wire electrode 60 is relatively small, for example, less than 0.1 mm, the annealing effect is smaller than that of a standard diameter exceeding 0.1 mm, and the straightness of the cut metal wire electrode 60 is poor. In this embodiment, no Joule heating is generated in the section where the metal wire electrode 60 is inserted into the conduit 110, and the straightness of the metal wire electrode 60 in this section can be maintained after cutting.

[0026] The area of ​​the metal wire electrode 60 that generates Joule heating is limited to the area between contact position PA and contact position PB. The length of the section of the metal wire electrode 60 that is inserted through the conduit 110 is tens of centimeters, while the length of the area between contact position PA and contact position PB is several centimeters. Therefore, the area in the cut metal wire electrode 60 where the integrity is destroyed is limited to the shorter area between contact position PA and contact position PB.

[0027] [Modifications] The above-described embodiments can also be modified as follows.

[0028] In the above embodiment, when cutting a metal wire electrode 60 with a smaller diameter, the power supply 140 applies a cutting voltage between the positive electrode 132 and the negative electrode 134. However, when cutting a metal wire electrode 60 with a standard diameter exceeding, for example, 0.1 mm, a cutting voltage can also be applied to the section of the metal wire electrode 60 that is inserted into the conduit 110. When Joule heating is generated in the section of the conduit 110, an annealing effect can be obtained by cooling the metal wire electrode 60, thereby improving the straightness of the metal wire electrode 60.

[0029] Figure 3 is an example of applying a cutting-off voltage to the metal wire electrode 60 in a modified example. Components shown in Figure 3 that are labeled with the same symbols as those shown in Figure 2 are omitted from the description. A chuck 160 is disposed between the roller 78 and the pipe 110. The chuck 160 has a pair of clamping electrodes 162 and 164.

[0030] When cutting a metal wire electrode 60 of standard diameter, the chuck 160 clamps the metal wire electrode 60 using a pair of clamping electrodes 162 and 164. The power supply 140 applies a cutting voltage between at least one of the clamping electrodes 162 and 164 and the negative electrode 134. The metal wire electrode 60 is then cut by the Joule heat generated between the uncooled piping 110 and the negative electrode 134.

[0031] When cutting the metal wire electrode 60 with a smaller diameter, the metal wire electrode 60 is not clamped by a pair of clamping electrodes 162 and 164. As described in the above embodiment, the power supply 140 applies a cutting voltage between the positive electrode 132 and the negative electrode 134.

[0032] Figure 3 shows the connection switching control unit 226 and the switching switch 300. The connection switching control unit 226 is implemented by executing a program through the processing circuit 200 of the control device 40. The connection switching control unit 226 can also be implemented using an ASIC, FPGA, or other integrated circuits. The switching switch 300 switches between connecting the positive terminal of the power cut-off 140 to the positive electrode 132 or to the clamping electrode 162. The switching switch 300 can also connect the positive terminal of the power cut-off 140 to the clamping electrode 164 instead of the clamping electrode 162, or connect it to both the clamping electrode 162 and the clamping electrode 164.

[0033] When cutting the metal wire electrode 60, the user inputs the metal wire diameter information of the metal wire electrode 60 to the control device 40. The connection switching control unit 226 of the control device 40 controls the switching switch 300 according to the metal wire diameter information to switch the connection object of the positive terminal of the power supply 140. When cutting a metal wire electrode 60 with a smaller diameter of 0.1 mm or less, the connection switching control unit 226 controls the switching switch 300 to connect the positive terminal of the power supply 140 to the positive electrode 132. When cutting a metal wire electrode 60 with a standard diameter of more than 0.1 mm, the connection switching control unit 226 controls the switching switch 300 to connect the positive terminal of the power supply 140 to the clamping electrode 162.

[0034] Furthermore, the connection switching control unit 226 of the control device 40 can also control the switching switch 300 to switch the connection object of the positive terminal of the power cut-off power supply 140 according to the material information of the metal wire electrode 60. When cutting the metal wire electrode 60 of a material with low annealing effect, the connection switching control unit 226 controls the switching switch 300 to connect the positive terminal of the power cut-off power supply 140 to the positive electrode 132. When cutting the metal wire electrode 60 of a material with high annealing effect, the connection switching control unit 226 controls the switching switch 300 to connect the positive terminal of the power cut-off power supply 140 to the clamping electrode 162. The user inputs the material information to the control device 40.

[0035] [Inventions derived from embodiments] The inventions described below can be understood from the above embodiments and variations.

[0036] (1) A wire EDM machine (10) for processing a workpiece (W) by generating a discharge from a wire electrode (60) includes an upper wire guide (64) supporting the wire electrode above the workpiece, a roller (78) that feeds the wire electrode from above the upper wire guide to the upper wire guide, a pipe (110) through which the wire electrode fed from the roller is inserted and through which a refrigerant flows, a positive electrode (132) and a negative electrode (134) of the wire electrode that contact the pipe and the upper wire guide when the wire electrode is spaced apart in the feeding direction, and a power supply (140) that applies a cutting voltage between the positive electrode and the negative electrode when the wire electrode is cut. In this way, the straightness of a relatively thin wire electrode after cutting can be maintained well.

[0037] (2) The wire EDM machine may also be equipped with a drive mechanism (136) that, when cutting the wire electrode, makes the positive electrode and the negative electrode contact the wire electrode. In this way, a cutting voltage can be easily applied to the wire electrode.

[0038] (3) The wire EDM machine may further include a pair of clamping electrodes (162, 164), a chuck (160) between the roller and the piping, which clamps the wire electrode with the pair of clamping electrodes, and a switch (300) that switches between connecting the positive terminal of the power supply to the positive electrode or to at least one of the pair of clamping electrodes. In this way, the straightness of the cut wire electrode can be maintained well regardless of the diameter of the cut wire electrode.

[0039] (4) The wire EDM machine may also be equipped with a connection switching control unit (226), which controls the switching switch to switch the connection object of the positive terminal according to the diameter or material of the wire electrode. It can switch according to the type of wire electrode, and maintain the straightness of the wire electrode after cutting. [Simplified Explanation of the Diagram]

[0008] Figure 1 is a diagram showing the structure of a wire electrical discharge machining machine according to one embodiment.

[0009] Figure 2 is an illustration of the state of applying a cut-off voltage to a metal wire electrode.

[0010] Figure 3 shows a modified example of the state in which a cutting voltage is applied to the metal wire electrode.

Claims

1. A wire electrical discharge machining (10) for processing a workpiece (W) by discharging a metal wire electrode (60), and comprising: an upper wire conductor (64) supporting the metal wire electrode above the workpiece; a roller (78) for conveying the metal wire electrode from above the upper wire conductor; a pipe (110) through which the metal wire electrode conveyed from the roller is inserted and through which a refrigerant flows; a positive electrode (132) and a negative electrode (134) in contact between the pipe and the upper wire conductor, with the metal wire electrode spaced apart from each other in the direction of its delivery; and a power cut-off voltage (140) for applying a cut-off voltage between the positive electrode and the negative electrode when the metal wire electrode is cut off. The chuck (160) has a pair of clamping electrodes (162, 164) that clamp the metal wire electrode between the roller and the piping; and a switch (300) that switches between connecting the positive terminal of the power cut-off power supply to the positive electrode or to at least one of the pair of clamping electrodes.

2. The wire EDM machine of claim 1 further comprises: a drive mechanism (136) that, when the wire electrode is cut, causes the positive electrode and the negative electrode to contact the wire electrode.

3. The wire EDM machine as requested in item 1 or 2 further includes: a connection switching control unit (226) that controls the switching switch to switch the connection object of the positive terminal according to the diameter of the wire electrode or the material of the wire electrode.

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