Wire EDM

Abstract

A wire electric discharge machine (10) for machining a workpiece (W) by generating an electrical discharge by a wire electrode (60), comprises: an upper wire guide (64); a roller (78) that feeds the wire electrode; a pipe (110) through which the wire electrode is inserted and a refrigerant flows; a positive electrode (132) and a negative electrode (134) that contact the wire electrode between the pipe and the upper wire guide in a state in which the positive electrode and the negative electrode are spaced apart from each other in the feeding direction of the wire electrode; and a power supply (140) that applies a cutting voltage between the positive electrode and the negative electrode when cutting the wire electrode.

Description

[Technical Field]

[0001] The present invention relates to a wire electric discharge machine. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 6-304819 discloses a wire electric discharge machine in which a wire electrode is cut by Joule heat between first and second wire cutting electrodes. A wire feed pipe structure is provided between the first and second wire cutting electrodes. The inside of the wire feed pipe structure is constantly cooled by cooling water. An annealing effect is obtained for the wire electrode inside the wire feed pipe structure, thereby suppressing curling of the wire electrode. Summary of the Invention

[0003] The wire electric discharge machine disclosed in Japanese Patent Laid-Open No. 6-304819 has a problem in that when a relatively thin wire electrode is used, the straightness of the wire electrode after cutting is poor.

[0004] The present invention aims to solve the above-mentioned problems.

[0005] One aspect of the present invention is a wire electric discharge machine that processes a workpiece by generating an electric discharge using a wire electrode, and includes an upper wire guide that supports the wire electrode above the workpiece, a roller that feeds the wire electrode from above the upper wire guide to the upper wire guide, a pipe through which the wire electrode fed from the roller is inserted and through which a coolant flows, a positive electrode and a negative electrode that are spaced apart from each other in the wire electrode feeding direction and contact the wire electrode between the pipe and the upper wire guide, and a power source that applies a cutting voltage between the positive electrode and the negative electrode when the wire electrode is cut.

[0006] According to the present invention, the straightness of a relatively thin wire electrode is well maintained after cutting. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the configuration of a wire electric discharge machine according to one embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of how a cutting voltage is applied to a wire electrode. [Figure 3] FIG. 3 is a diagram illustrating an example of how a cutting voltage is applied to a wire electrode in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] FIG. 1 is a diagram showing the configuration of a wire electric discharge machine 10 according to one embodiment. The X, Y, and Z directions shown in FIG. 1 are perpendicular to one another, and the -Z direction is the direction of gravity. The wire electric discharge machine 10 has a main body 20, a machining power supply 30, and a control device 40. The machining power supply 30 applies a voltage to a gap formed between a wire electrode 60 and a workpiece (not shown) to generate an electric discharge. The workpiece is supported on a table 62. The wire electric discharge machine 10 generates an electric discharge between the gap using the wire electrode 60, thereby electric discharge machining the workpiece.

[0009] During electrical discharge machining, the wire electrical discharge machine 10 moves the wire electrode 60 relative to the workpiece along a machining path specified by a predetermined program. The relative movement between the wire electrode 60 and the workpiece is achieved, for example, by moving the table 62.

[0010] The wire electric discharge 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 die guide 70, and an upper nozzle (not shown). The lower wire guide 66 includes a lower guide block 72, a lower die guide 74, and a lower nozzle (not shown). The upper wire guide 64 supports the wire electrode 60 above the table 62 and the workpiece (+Z direction). The lower wire guide 66 supports the wire electrode 60 below the table 62 (-Z direction).

[0011] The wire electrode 60 is supplied from a wire bobbin 76 in the feeding direction at a predetermined speed. The wire electrode 60 is fed via rollers 78, an upper wire guide 64, and a lower wire guide 66. The rollers 78 include a guide roller (not shown), a brake roller 80, and a first pinch roller 82. The rollers 78 feed the wire electrode 60 from above the upper wire guide 64 to the upper wire guide 64. The wire electrode 60 is clamped between a second pinch roller 84 and a feed roller 86. The wire electrode 60 is collected in a collection box 88.

[0012] When wire electric discharge machining is performed, the machining tank 90 may store machining fluid. In this case, the table 62, the workpiece, the upper wire guide 64, and the lower wire guide 66 are immersed in the machining fluid. The machining tank 90 is installed on a bed 92.

[0013] The control device 40 controls the main body 20 to perform the above-described electric discharge machining. When the electric discharge machining is completed and the workpiece is replaced, the control device 40 controls the main body 20 to cut and connect the wire electrode 60. When the machining position on the workpiece is changed, the wire electrode 60 is also cut and connected. Furthermore, even if the wire electrode 60 breaks during electric discharge machining, a new wire electrode 60 is cut and connected at a position above the breakage position.

[0014] Fig. 2 is a diagram illustrating an example of how a cutting voltage is applied to a wire electrode 60. Fig. 2 shows a workpiece W placed on a table 62. An upper wire guide 64 supports the wire electrode 60 above the workpiece W.

[0015] The wire electrode 60 fed from the rollers 78 to the upper wire guide 64 is inserted into a pipe 110. A coolant flows through the pipe 110. When the wire electrode 60 is to be cut, the rollers 78 rotate in the opposite direction to when the wire electrode 60 was fed out, thereby pulling up the wire electrode 60 and applying tension to the wire electrode 60.

[0016] When the wire electrode 60 is cut, the positive electrode 132 and the negative electrode 134 are driven by the drive mechanism 136 and each come into contact with the wire electrode 60 below the pipe 110. The positive electrode 132 and the negative electrode 134 each come into contact with the wire electrode 60 while being spaced apart from each other in the feeding direction of the wire electrode 60. The positive electrode 132 and the negative electrode 134 come into contact with the wire electrode 60 between the pipe 110 and the upper wire guide 64. The wire electrode 60 and the positive electrode 132 come into contact with each other at a contact position PA. The wire electrode 60 and the negative electrode 134 come into contact with each other at a contact position PB.

[0017] The positive terminal of the cutting power supply 140 is connected to the positive electrode 132. The negative terminal of the cutting power supply 140 is connected to the negative electrode 134. The cutting power supply 140 applies a cutting voltage between the positive electrode 132 and the negative electrode 134. The wire electrode 60 is cut by Joule heat generated between a contact position PA of the positive electrode 132 and a contact position PB of the negative electrode 134.

[0018] The control device 40 has a processing circuit 200 and a storage unit 210. The processing circuit 200 includes a processor such as a CPU. The storage unit 210 includes a volatile memory such as a RAM and a non-volatile memory such as a ROM or flash memory. The storage unit 210 stores programs and the like. The processing circuit 200 executes the programs to implement a machining control unit 220, a drive control unit 222, and a cutting power supply control unit 224. At least some of the machining control unit 220, the drive control unit 222, and the cutting power supply control unit 224 may be implemented by an ASIC, an FPGA, or other integrated circuit.

[0019] While the workpiece W is being electric discharge machined, the machining control unit 220 controls a motor (not shown) to feed the wire electrode 60 from the upper wire guide 64 toward the lower wire guide 66. The machining control unit 220 controls a motor (not shown) to move the wire electrode 60 relative to the workpiece W. The machining control unit 220 controls the machining power supply 30 to generate an electric discharge between the electrodes.

[0020] 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 wire electrode 60. The cutting power supply control unit 224 controls the cutting power supply 140 to apply a cutting voltage between the positive electrode 132 and the negative electrode 134. Joule heat is generated between the contact position PA and the contact position PB.

[0021] For example, when using a conventional technique such as that disclosed in Japanese Patent Application Laid-Open No. 6-304819, Joule heat is generated in the section of the wire electrode 60 inserted into the pipe 110. A coolant flows along the wire electrode 60 in the pipe 110. Therefore, the wire electrode 60 is cooled in the section of the wire electrode 60 inserted into the pipe 110. Therefore, an annealing effect is obtained in this section, and it is expected that the straightness of the wire electrode 60 after cutting will be improved.

[0022] However, when the diameter of the wire electrode 60 is relatively small, for example, 0.1 mm or less, the annealing effect is small compared to when the diameter exceeds 0.1 mm, and the straightness of the wire electrode 60 after cutting is poor. In this embodiment, Joule heat is not generated in the section of the wire electrode 60 inserted into the pipe 110, and the straightness of this section of the wire electrode 60 is maintained after cutting.

[0023] The section of the wire electrode 60 where Joule heat is generated is limited to the section between the contact positions PA and PB. The length of the section of the wire electrode 60 inserted into the pipe 110 is several tens of centimeters, whereas the length of the section between the contact positions PA and PB is several centimeters. Therefore, the section of the cut wire electrode 60 where the straightness is lost is limited to the relatively short section between the contact positions PA and PB.

[0024] [Variations] The above embodiment may be modified as follows.

[0025] In the above embodiment, when cutting a wire electrode 60 having a relatively small diameter, the cutting power supply 140 applies a cutting voltage between the positive electrode 132 and the negative electrode 134. However, when cutting a wire electrode 60 having a standard diameter, for example, exceeding 0.1 mm, the cutting voltage may be applied to the section of the wire electrode 60 inserted into the pipe 110. If Joule heat is generated in the section inserted into the pipe 110, the wire electrode 60 is cooled, resulting in an annealing effect and improving the straightness of the wire electrode 60.

[0026] 3 is a diagram illustrating an example of how a cutting voltage is applied to wire electrode 60 in a modified example. Of the components shown in FIG. 3, those that are given the same reference numerals as those shown in FIG. 2 will not be described. A chuck 160 is disposed between roller 78 and piping 110. Chuck 160 has a pair of clamp electrodes 162 and 164.

[0027] When a wire electrode 60 having a standard diameter is cut, the chuck 160 clamps the wire electrode 60 with a pair of clamp electrodes 162 and 164 to hold the wire electrode 60. The cutting power supply 140 applies a cutting voltage between at least one of the pair of clamp electrodes 162 and 164 and the negative electrode 134. The wire electrode 60 is cut by Joule heat generated between the uncooled pipe 110 and the negative electrode 134.

[0028] When a wire electrode 60 having a relatively small diameter is cut, the wire electrode 60 is not clamped by the pair of clamp electrodes 162 and 164. As described in the above embodiment, the cutting power supply 140 applies a cutting voltage between the positive electrode 132 and the negative electrode 134.

[0029] 3 shows the connection switching control unit 226 and the switch 300. The connection switching control unit 226 is realized by the processing circuit 200 of the control device 40 executing a program. The connection switching control unit 226 may be realized by an ASIC, an FPGA, or another integrated circuit. The switch 300 switches whether the positive terminal of the cutting power supply 140 is connected to the positive electrode 132 or the clamp electrode 162. The switch 300 may also connect the positive terminal of the cutting power supply 140 to the clamp electrode 164 instead of or in addition to the clamp electrode 162.

[0030] When cutting a wire electrode 60, the user inputs wire diameter information relating to the diameter of the wire electrode 60 into the control device 40. The connection switching control unit 226 of the control device 40 controls the switch 300 to switch the connection destination of the positive terminal of the cutting power supply 140 in accordance with the wire diameter information. When cutting a wire electrode 60 having a relatively thin diameter of 0.1 mm or less, the connection switching control unit 226 controls the switch 300 to connect the positive terminal of the cutting power supply 140 to the positive electrode 132. When cutting a wire electrode 60 having a standard diameter of more than 0.1 mm, the connection switching control unit 226 controls the switch 300 to connect the positive terminal of the cutting power supply 140 to the clamp electrode 162.

[0031] The connection switching control unit 226 of the control device 40 may control the switch 300 to switch the connection destination of the positive terminal of the cutting power supply 140 in accordance with material information regarding the material of the wire electrode 60. When a wire electrode 60 made of a material with a low annealing effect is to be cut, the connection switching control unit 226 controls the switch 300 to connect the positive terminal of the cutting power supply 140 to the positive electrode 132. When a wire electrode 60 made of a material with a high annealing effect is to be cut, the connection switching control unit 226 controls the switch 300 to connect the positive terminal of the cutting power supply 140 to the clamp electrode 162. The material information is input to the control device 40 by a user.

[0032] [Inventions Obtained from the Embodiments] The invention that can be understood from the above-described embodiment and modifications will be described below.

[0033] (1) A wire electric discharge machine (10) that machines a workpiece (W) by generating an electric discharge using a wire electrode (60) includes an upper wire guide (64) that supports 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 passes and through which a coolant flows, a positive electrode (132) and a negative electrode (134) that are spaced apart in the wire electrode feeding direction and that contact the wire electrode between the pipe and the upper wire guide, and a power supply (140) that applies a cutting voltage between the positive electrode and the negative electrode when the wire electrode is cut. This allows the relatively thin wire electrode to maintain good straightness after cutting.

[0034] (2) The wire electric discharge machine may further include a drive mechanism (136) that brings the positive electrode and the negative electrode into contact with the wire electrode when the wire electrode is cut, thereby enabling a cutting voltage to be easily applied to the wire electrode.

[0035] (3) The wire electric discharge machine may further include a chuck (160) having a pair of clamp electrodes (162, 164) for clamping the wire electrode between the roller and the pipe, and a switch (300) for switching between connecting the positive terminal of the power supply to the positive electrode or to at least one of the pair of clamp electrodes. This allows the straightness of the wire electrode after cutting to be maintained at a good level regardless of the diameter of the wire electrode being cut.

[0036] (4) The wire electric discharge machine may further include a connection switching control unit (226) that controls the switch to switch the connection destination of the positive terminal depending on the diameter or material of the wire electrode. Switching depending on the type of wire electrode makes it possible to maintain good straightness of the wire electrode after cutting. [Explanation of symbols]

[0037] 10...Wire electric discharge machine 20...Main body 30...Processing power supply 40...Control device 60...wire electrode 62...table 64...Upper wire guide 66...Lower wire guide 68...Upper guide block 70...Upper die guide 72...Lower guide block 74...Lower die guide 76...Wire bobbin 78...Roller 80...Brake roller 82...First pinch roller 84...Second pinch roller 86...Feed roller 88...Collection box 90...Processing tank 92...Bed 110...Plumbing 132...positive electrode 134...negative electrode 136... Drive mechanism 140... Cutting power supply 160...Chuck 162, 164...Clamp electrodes 200... Processing circuit 210... Storage unit 220... Machining control unit 222... Drive control unit 224... Cutoff power supply control unit 226... Connection switching control unit 300...Switch

Claims

1. A wire electric discharge machine that processes a workpiece by generating an electric discharge using a wire electrode, an upper wire guide that supports the wire electrode above the workpiece; a roller that feeds the wire electrode from above the upper wire guide to the upper wire guide; a pipe through which the wire electrode fed from the roller is inserted and through which a coolant flows; a positive electrode and a negative electrode spaced apart from each other in a wire electrode feeding direction and in contact with the wire electrode between the piping and the upper wire guide; a power supply that applies a cutting voltage between the positive electrode and the negative electrode when the wire electrode is cut; a chuck having a pair of clamp electrodes, the chuck clamping the wire electrode by the pair of clamp electrodes between the roller and the piping; a switch that switches between connecting the positive terminal of the power supply to the positive electrode or to at least one of the pair of clamp electrodes; A wire electric discharge machine comprising:

2. 2. The wire electric discharge machine according to claim 1, a drive mechanism that brings the positive electrode and the negative electrode into contact with the wire electrode when the wire electrode is cut; The wire electric discharge machine further comprises:

3. 3. The wire electric discharge machine according to claim 1, a connection switching control unit that controls the switch to switch the connection destination of the positive electrode terminal in accordance with the diameter or material of the wire electrode; The wire electric discharge machine further comprises:

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