JP2010155332A - Power supply die for wire electric discharge machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply die for preventing impurities from sticking even when the die is used for wire electric discharge machine causing discharge in a working liquid such as ion exchange water. <P>SOLUTION: The power supply die for the wire electric discharge machine includes a body made of cemented carbide and an organic insulating film uniformly coating the body. The carbon amount regarding the total weight of four elements of tungsten, cobalt, carbon and oxygen is 2.8-16 wt.% when energy dispersion type X-ray analysis is executed with acceleration voltage of 15 kV. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power feeding die for a wire electric discharge machine. More specifically, the present invention relates to a power feeding die for a wire electric discharge machine that has an organic insulating film on the surface and is less likely to have impurities attached even when electric discharge machining is repeated in a machining liquid.

  The wire electric discharge machine is a machine that mainly processes a conductive workpiece (metal workpiece) such as metal using a wire as thick as hair. The processing principle is based on melting the target metal workpiece and cutting it using electric power (mainly heat generated by the discharge phenomenon). That is, wire electrical discharge machining is non-contact machining and melt machining that does not contact the workpiece.

  A general configuration of a wire electric discharge machine is shown in FIG. The wire 2 fed out from the supply reel 1 travels in the direction of → in FIG. 1 and is discharged to the discharge unit 5 through the upper power supply die 3a, the upper guide 4a, the lower guide 4b, and the lower power supply die 3b. The moving direction of the wire is as indicated by the arrow in FIG.

  The upper power supply die 3 a and the lower power supply die 3 b are connected to the power supply device 6. Since the upper feeding die 3a and the lower feeding die 3b are in contact with the wire 2, the wire 2 is also charged.

  On the other hand, the work table 7 is also connected to the power supply device 6. And the metal workpiece 8 installed on the work table 7 is also charged. As a result, a discharge spark 9 is generated at a portion where the wire 2 and the workpiece 8 are closest to each other, and the surface of the workpiece is melted, scattered, removed, and processing such as cutting is performed.

  Usually, when electric discharge machining is performed, machining is performed in a state in which the workpiece 8 is completely submerged by the ion exchange water 10 (machining liquid). This is for maintaining insulation in the vicinity of the discharge spark 9 and removing machining waste (see Patent Document 1).

  In this case, since the workpiece is positively charged, electrolytic corrosion of the surface layer is likely to occur, and the surface layer of portions other than the processed portion may deteriorate during electric discharge machining. In order to prevent such deterioration of the surface layer of the workpiece, a technique for applying a rust preventive agent such as wax to the workpiece is disclosed in Patent Document 2.

  In addition, since the feed die needs durability, the material is generally a cemented carbide, but the cemented carbide has a large specific electric resistance value, so that the cemented carbide feed die and the wire are used. A part of the electric power supplied from the power source is dissipated as Joule heat, and a part of the energy is wasted.

  As means for solving this problem, Patent Document 3 discloses that a power supply die is made of a conductive material having an electric resistance smaller than that of cemented carbide.

JP-A-6-320339 JP 59-169715 A Japanese Patent Laid-Open No. 4-105821

  The ion-exchanged water is almost free of impurities. However, in the case of electric discharge machining in which the workpiece is submerged in ion-exchanged water as disclosed in Patent Document 1, the workpiece is cut and the like. Metal ions derived from the workpiece are eluted in the ion exchange water. In the wire electric discharge machine, as shown in FIG. 1, the wire 2 runs vertically from the upper side to the lower side with respect to the workpiece 8, and the lower power feeding die 3 b is also submerged in the ion exchange water.

  Since the lower power feeding die 3b is negatively charged, a phenomenon occurs in which metal ions eluted in ion-exchanged water and impurities existing in a very small amount are electrically attracted and adhere to the surface layer. These impurities are difficult to peel off and have high electrical resistance.

  In the wire electric discharge machine as shown in FIG. 1, the wire and the power feeding die are in contact with each other in the state shown in FIG. Here, the wire 2 is moving from top to bottom as indicated by the arrow, but the contact portion of the power feeding die 11 with the wire 2 is worn by friction. When the first machining is finished in this state and the second machining is brought into contact with the worn portion and the machining is resumed, the wire and the power feeding die do not come into good contact with each other and the discharge becomes unstable. For this reason, when the first machining shown in FIG. 2 (a) is completed, the feeding die as shown in FIG. 2 (b) is used so that the groove 12 and the wire 2 generated by the first machining do not contact each other. 2 is rotated to perform the second processing.

  Further, when the second machining is completed, the feeding die 2 is rotated again as shown in FIG. 2C so that the groove 13 and the wire 2 generated by the second machining are not in contact with each other. Perform the second machining. In this way, if the power feeding die is rotated so that the unused portion and the wire 2 are in contact each time, one power feeding die can be used repeatedly.

  However, when impurities derived from metal ions or the like eluted in ion-exchanged water adhere to the surface of the power supply die, even if the power supply die is rotated as shown in FIG. It is lowered by. Then, at the start of electric discharge machining, appropriate power supply from the power feeding die to the wire cannot be performed, and the machining accuracy is lowered. As a result, it is necessary to replace an expensive power supply die without waiting for the original life, leading to an increase in electric discharge machining cost.

  An object of the present invention is to provide a power feeding die that hardly adheres to impurities even when used in a wire electric discharge machine that generates electric discharge in a machining fluid such as ion exchange water.

  The present inventors tried to cover the power supply die made of cemented carbide with an organic insulating film as disclosed in Patent Document 2, but prevented adhesion of impurities to the power supply die having negative electricity. It was difficult to do. On the other hand, if the thickness of the organic insulating film is increased in order to prevent the adhesion of impurities, the organic insulating film cannot be completely removed even when the wire is brought into contact with the power supply die during electric discharge machining, and discharge is not achieved. It has become stable.

  However, as a result of earnest research, the surface of the power die made of cemented carbide is covered with an organic insulating film so as to exhibit a specific parameter, so that impurities do not adhere in ion-exchanged water and the like, and The inventors have found that the discharge is stable and have completed the present invention.

Specifically, the present invention
A body made of cemented carbide,
An organic insulating film that uniformly covers the main body,
The amount of carbon when energy dispersive X-ray analysis is performed at an acceleration voltage of 15 kV is 2.8 wt% to 16 wt% with respect to the total weight of the four elements consisting of tungsten, cobalt, carbon and oxygen And

  When a power supply die made of cemented carbide is coated with an organic insulating film, as described above, there is a problem whether the organic insulating film is thin or thick. In addition, the amount of impurities attached to the organic insulating film and the conductivity are affected by the material of the feed die body (the cemented carbide itself), so simply adjusting the thickness of the organic insulating film will prevent the adhesion of impurities. It is impossible to stabilize the discharge performance while preventing this.

  However, analysis is performed under the condition of an acceleration voltage of 15 kV with the cemented carbide body covered with an organic insulating film, and the carbon content under the measurement conditions is the total weight of four elements consisting of tungsten, cobalt, carbon and oxygen. If the amount of carbon in the power supply die and the thickness of the organic insulating film are adjusted so that they are 2.8 wt% or more and 16 wt% or less relative to It becomes possible for the first time to stabilize the performance.

  As the organic insulating film, polyester, epoxy resin, phenol resin, or the like can be used, and the material is not particularly limited. The thickness of the organic insulating film is limited by the ratio of carbon weight by X-ray analysis and is not limited by a specific thickness.

  The power supply die for the wire electric discharge machine of the present invention is less likely to cause impurities to adhere to the surface even when continuously used in ion-exchanged water, and has high discharge performance.

  The surface of a commercially available cemented carbide power supply die (wire electric discharge machine manufactured by Mitsubishi Electric Corporation, power supply die of genuine part number PX05, model number DP478A) is coated with polystyrene resin as an organic insulating film, and a plurality of insulating dies are coated. Produced.

  The produced insulating die was measured for carbon, tungsten, cobalt, and oxygen using an energy dispersive X-ray analyzer EX-220 manufactured by HORIBA, Ltd. under the conditions of an acceleration voltage of 15 kV and a viewing magnification of 500 times (total of these four elements). The weight was measured to be 100%). In addition, five places were measured for one insulating die, and the average value was calculated.

  Thereafter, two insulating dies (an upper feeding die and a lower feeding die) were attached to the wire electric discharge machine. Ion exchange water was used as machining water, and electric discharge machining was performed for 100 hours in a state in which the workpiece (carbide) and the lower feed die were submerged in the ion exchange water. The wire used was a brass wire (Oki Electric Cable Co., Ltd., wire diameter 0.2 mm, model number OB-10P (φ0.1 mm)).

  Regarding the discharge performance, whether or not the power supply was stable at the start of electric discharge machining was confirmed by a method of determining whether or not a short circuit occurred using an oscilloscope. In addition, regarding the presence or absence of deposits, after the processing was completed, the lower feeding die was removed, the surface state was visually observed, and when there was discoloration, it was determined that deposits were present.

  Table 1 shows the average carbon content (% by weight), presence / absence of discoloration, and discharge performance of the produced insulating dies. Note that neither Conventional Example 1 nor Conventional Example 2 in Table 1 has an organic insulating film.

  The feeding dies of Conventional Example 1 and Conventional Example 2 do not have an organic insulating film, and the average carbon content indicates the carbon content of cemented carbide only. The power supply die of Comparative Example 1 has an average carbon content intermediate between Conventional Example 1 and Conventional Example 2. Although these power feeding dies have stable discharge performance, discoloration is recognized, and therefore, when used continuously, there is a problem that the power feeding dies cannot be used after the second rotation.

  The feed dies of Examples 1 to 11 having an organic insulating film and having an average carbon content of 2.8 wt% or more and 15.9 wt% showed no discoloration after electric discharge machining. Moreover, the discharge performance was stable.

  On the other hand, the feeding dies of Comparative Examples 2 to 4 having an organic insulating film and an average carbon content of 16.1% by weight or more showed no discoloration after electric discharge machining, but the discharge performance was unstable. Met. For this reason, it was judged that the power supply dies of Comparative Examples 2 to 4 have low practicality.

  In addition, the thickness of the organic insulating film of the power supply dies of Examples 1 to 11 was in the range of 0.5 μm to 5 μm.

  As described above, the power supply die for the wire electric discharge machine according to the present invention prevents the adhesion of impurities in the ion-exchanged water by covering the cemented carbide body with the organic insulating film so as to show the specific parameter. Can be used for a long time. In addition, there is no adverse effect on the discharge characteristics due to the organic insulating film.

  The power feeding die for the wire electric discharge machine of the present invention is useful in the field of metal working and the like.

It is a figure explaining the general structure of a wire electric discharge machine. It is an enlarged view of a contact portion between a wire and a power supply die of a wire electric discharge machine, where (a) is the first machining, (b) is the second machining, and (c) is the third machining. Indicates the time.

1: Supply reel 2: Wire 3a: Upper feed die 3b: Lower feed die 4a: Upper guide 4b: Lower guide 5: Ejector 6: Power supply device 7: Work table 8: Work piece 9: Discharge spark 10: Ion exchange Water (working fluid)
11: Feeding die 12: Groove generated during the first machining 13: Groove generated during the second machining

Claims (1)

A body made of cemented carbide,
A power supply die for a wire electric discharge machine having an organic insulating film covering a main body,
When energy dispersive X-ray analysis is performed at an acceleration voltage of 15 kV, the carbon content of the surface layer is 2.8 wt% to 16 wt% with respect to the total weight of the four elements consisting of tungsten, cobalt, carbon, and oxygen. A power feed die for a wire electric discharge machine.

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