JP2009039817A - Electrical discharge machining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent positive electrodes from disturbing machining, and to prevent a lowering in a specific resistance value caused by the dissolution of positive electrodes in a water-based electrical discharge machining liquid. <P>SOLUTION: A workpiece 3 mounted and fixed to a workpiece stand 2 is connected to a negative electrode of a direct voltage source 21 of an electric protection circuit 20. The first positive electrode 23 is arranged higher than the workpiece 3 and in the vicinity of the workpiece 3 without disturbing machining so as to be dipped into the electric discharge machining liquid 11, and has a shape forming an electric line of a force between the whole upper surface of the workpiece 3 and the first positive electrode. The second carbon positive electrode 24 is formed of a sheetlike carbon material, deformably arranged along the outer shape of a strut to the strut of the workpiece stand 2, and has a shape forming an electric line of a force between the whole lower surface of the workpiece 3 and the second carbon positive electrode. The first carbon positive electrode 23 and the second carbon positive electrode 24 are connected to the positive electrode of the direct voltage source 21. A protection current flows between the first carbon positive electrode 23 and the whole upper surface of the workpiece 3 and between the second carbon positive electrode 24 and the whole lower surface of the workpiece 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric discharge machining apparatus provided with an anticorrosion circuit that prevents electric corrosion from occurring on a workpiece when the workpiece is immersed in an aqueous electric discharge machining liquid for electric discharge machining.

  When electric discharge machining is performed by immersing a workpiece in an aqueous electric discharge machining fluid, it is known that electric corrosion (electric corrosion) occurs in an iron-based or cemented carbide workpiece. Electrocorrosion in the work piece is caused by the fact that a brass wire electrode is used as the negative electrode, and a work piece made of iron or cemented carbide is used as the positive electrode. Corrosion current flows between the negative electrode and the positive electrode due to the potential difference between the negative electrode and the positive electrode. It is believed that the work piece is generated by oxidation.

  Since the electric discharge machining apparatus is configured to apply electric discharge machining voltage between the wire electrode and the workpiece from the machining power source to the machining gap to generate electric discharge and to discharge the workpiece. During machining, the voltage applied to the machining gap is a bipolar pulse voltage, so that the average machining voltage is maintained at 0 V and the potential difference between the wire electrode and the workpiece is eliminated, and the workpiece is not made positive. This prevents electrical corrosion of the work piece. However, when electric discharge machining is suspended, no voltage is applied from the machining power source to the machining gap, so that electric corrosion of the workpiece cannot be prevented.

  Generally, in order to prevent the occurrence of rust in an iron-based workpiece, a rust-preventing agent containing a saccharide is used by being mixed in a water-based electric discharge machining liquid. However, rust inhibitors are used because the components of the rust inhibitor may be harmful in other manufacturing processes such as plating performed after electrical discharge machining, and may adversely affect the ion exchange resin of the water purifier. There are cases where it is not possible. In addition, there is a system that does not contain additives and prevents the generation of rust by absorbing chloride ions and sulfate ions that are the cause of rust generation. When the finishing process is performed using an EDM fluid, residual sodium nitrite is a catalyst that reacts with metal ions and fatty acids generated in the oil-based EDM solution, so that it is an insoluble metal soap. Is generated, causing clogging of the water purifier and the filter. In addition, use of a rust preventive agent or a rust prevention system cannot be applied to a non-ferrous metal workpiece such as a cemented carbide.

  In view of this, a method for preventing the electrical corrosion of the workpiece by using an anticorrosion method has been considered. Well-known methods for preventing corrosion of steel materials are classified into a galvanic anode method (sacrificial anode method) and an external power source method. In the galvanic anode method, a metal having a lower natural potential than a metal material to be protected is used as a sacrificial anode, and the metal material to be protected is prevented from being corroded by preferentially oxidizing the metal material protecting the sacrificial anode. As the sacrificial anode, magnesium, zinc, and aluminum are mainly used. In the external power supply method, the metal material to be protected is connected to the negative electrode, the insoluble electrode is connected to the positive electrode, the anticorrosive current is supplied from the DC power supply, and the negative electrode potential is increased to the positive electrode potential or more by the polarization effect. The metal material is prevented from being dissolved by making the metal material to be extinguished and having a negative polarity so as not to be dissolved.

  In the galvanic anode method, since the water-based electrical discharge machining fluid is mainly ion-exchanged water, the metal of the sacrificial anode is dissolved in the water-based electrical discharge machining fluid, and metal ions flow into the water-based electrical discharge machining fluid, and the ratio of the water-based electrical discharge machining fluid Not only is the resistance value lowered, but the substantial anticorrosive effect is small, which is not suitable. The external power supply method has a high anticorrosion effect, and there is an electric discharge machining apparatus disclosed in Patent Documents 1 to 3 as an application of the external electrode method.

  In the electric discharge machining apparatus of Patent Document 1 or Patent Document 2, electric lines of force that exist when a corrosion-proof current flows between a workpiece that is an anode electrode and a cathode electrode are applied to the entire upper and lower surfaces of the workpiece. Therefore, there is a risk of partial electric corrosion. Further, in the electric discharge machining apparatus of Patent Document 1 or Patent Document 2, the metal of the anode electrode is dissolved in the aqueous electric discharge machining liquid, and metal ions flow into the aqueous electric discharge machining liquid to reduce the specific resistance value of the aqueous electric discharge machining liquid. There is a fear.

  In the electric discharge machining apparatus of Patent Document 3, the anode electrode made of a plate having a conductive layer provided on the upper surface and the lower surface side of the workpiece is disposed across the workpiece, so that the anticorrosion current is applied to the entire surface of the workpiece. By flowing and obtaining a uniform current density over the entire surface of the workpiece, the entire surface of the workpiece can be protected. In addition, since the electric discharge machining apparatus of Patent Document 3 uses an insoluble electrode such as platinum as the anode electrode, the metal of the anode electrode is dissolved in the aqueous electric discharge machining liquid, and metal ions flow into the aqueous electric discharge machining liquid. There is no possibility that the specific resistance value of the water-based electric discharge machining fluid will decrease.

JP 58-137524 A Japanese Patent No. 2705427 Japanese Patent No. 3132766

  Since the plate provided with the conductive layer is disposed on the upper surface and the lower surface side of the workpiece, the relative movement between the workpiece and the tool electrode is hindered during actual machining, and the plate hinders machining. In addition, it is necessary to prepare a plate provided with a conductive layer of a metal such as platinum in accordance with the upper and lower surfaces of the workpiece, but in reality, a plate provided with a conductive layer such as platinum is Expensive.

  In view of the above problems, the present invention can prevent electric corrosion on the entire upper surface and lower surface of a workpiece, does not hinder the processing, and the anode electrode is dissolved in the aqueous electric discharge machining liquid. The main object is to provide an electric discharge machining apparatus having an improved practical electro-corrosion protection circuit that does not lower the specific resistance value of the aqueous electric discharge machining liquid.

  In order to solve the above problems, the present invention provides a work stand (2) erected on a table (1), a workpiece (3) attached and fixed to the work stand (2), and a table (1). ) A processing tank (10) provided on the workpiece to surround the workpiece (3) and storing the electric discharge machining liquid (11); and the workpiece (3) so as to be immersed in the electric discharge machining liquid (11). The first carbon anode electrode (23) and a sheet-like charcoal having a shape that can form electric lines of force between the upper surface of the workpiece (3) and the entire upper surface of the workpiece (3). The work stand (2) is made of a raw material and is lower than the work piece (3). The work stand (2) is deformed and arranged along the outer shape of the work stand (3). Second carbon anode electrode (24) and first carbon anode electrode having shapes capable of forming electric lines of force 23) and a positive electrode connected to the second carbon anode electrode (24), a negative electrode connected to the workpiece (3), and a direct current power source (21) for supplying a corrosion protection current (20). .

  Preferably, the first carbon anode electrode (23) and the second carbon anode electrode (24) have a sufficient area for the anticorrosion current to flow between the entire upper surface of the workpiece (3).

  The electric discharge machining apparatus of the present invention is arranged at a position that is higher than the workpiece and does not hinder the machining so as to be immersed in the electric discharge machining liquid, and can form electric lines of force between the entire upper surface of the workpiece. The first carbon anode electrode having a shape and a work stand support positioned at a lower position than the work piece are formed of a sheet-like carbon material that is deformed and arranged along the outer shape of the work support. Since the second carbon anode electrode having a shape capable of forming electric lines of force between the entire lower surface is disposed, the anticorrosion current can be applied to the entire upper surface and lower surface of the workpiece, and it is ensured uniformly. It prevents electric corrosion of the workpiece and does not hinder processing. Therefore, it can be put to practical use and has an effect of high anti-corrosion effect.

  Further, the electric discharge machining apparatus of the present invention is provided with the first carbon anode electrode and the second carbon anode electrode, and the carbon is an insoluble electrode and is difficult to dissolve in the water-based electric discharge machining liquid. Carbonate ions are only generated. Therefore, the specific resistance value of the water-based electric discharge machining liquid is hardly lowered, and the life of the ion exchange resin of the pure water device is not shortened. Further, there is no problem that the filter is clogged due to the generation of impurities. As a result, there is almost no influence on processing, and the effect of excellent maintenance is achieved. And since a harmful | toxic substance does not exist in the next manufacturing process after electric discharge machining like a rust preventive agent, there exists an effect which improves work efficiency.

  The principal part of this machine of a wire cut electric discharge machining apparatus is shown by FIG. The wire cut electric discharge machining apparatus includes a table 1, and a work stand 2 is erected on the table 1. A workpiece 3 is attached and fixed to the work stand 2. The wire cut electric discharge machining apparatus includes a machining head 4, and an upper arm 5 is attached to the machining head 4.

  An upper guide assembly 6 is provided on the upper arm 5, and a lower guide assembly 8 is provided on the lower arm 7. The wire electrode 9 is stretched between an upper wire guide housed in the upper guide assembly 6 and a lower wire guide housed in the lower guide assembly 8. An upper energization body (not shown) is provided in the upper guide assembly 6, and a lower energization body (not shown) is provided in the lower guide assembly 8.

  A processing tank 10 for storing an electric discharge machining liquid is provided on the table 1 so as to surround the workpiece 3. The workpiece 3 is immersed in the electric discharge machining liquid 11 stored in the machining tank 10. The electric discharge machining liquid 11 may be a water-based electric discharge machining liquid or an oil-based electric discharge machining liquid. A machining fluid jet is supplied from a nozzle provided in the upper guide assembly 6 and a nozzle provided in the lower guide assembly 8. The workpiece 3 and the wire electrode 9 are relatively moved by moving either one or both of the table 1 and the processing head 4 directly or indirectly.

  The workpiece 3 is connected to the positive electrode side of the machining power supply circuit 12 through the energized portion of the work stand 2 made of stainless steel or the like, and the wire electrode 9 is connected to the negative electrode side through the energizer. The column part of the work stand 2 of the embodiment is made of insulating ceramics. The workpiece 3 and the wire electrode 9 are disposed to face each other, and a discharge current pulse is supplied from a machining power supply circuit 12 to a machining gap formed by the workpiece 3 and the wire electrode 9, so that the workpiece 3 is processed as desired. EDM is processed into a shape. Further, the machining power supply circuit 12 is provided with a polarity switching circuit (not shown) that reverses the connection polarity, and can switch the polarity of the workpiece 3 and the wire electrode 9 to supply bipolar pulses. .

  The anticorrosion circuit 20 includes a DC power source 21, a protective resistor 22, a first carbon anode electrode 23, a second carbon anode electrode 24, a cathode electrode that is a workpiece 9, and an aqueous electric discharge machining liquid 11. , Comprising. Accordingly, the anticorrosion current supplied from the DC power supply 21 flows from the first carbon anode electrode 23 and the second carbon anode electrode 24 to the workpiece 3 through the aqueous electric discharge machining liquid 11.

  In the DC power source 21, a plus electrode is connected to the first carbon anode electrode 23 and the second carbon anode electrode 24, and a minus electrode is connected to the workpiece 3, and supplies an anticorrosion current to the cathodic protection circuit 20. The DC power source 21 is several V to several tens V that supplies a sufficient and sufficient anticorrosion current to maintain the workpiece 3 in the negative polarity and obtain a polarization effect.

  The protective resistor 22 is configured so that the first carbon anode electrode 23 or the second carbon anode electrode 24 and the second carbon anode electrode 24 and the workpiece 3 that is the cathode electrode are short-circuited. Or for protecting a member constituting the anticorrosion circuit 20 such as a lead wire, and having a resistance value enough to obtain an anticorrosion current of several A (ampere) or less corresponding to the voltage of the DC power supply 21. A resistor is provided between the negative pole of the DC power supply 21 and the energized part of the work stand 2.

  The first carbon anode electrode 23 is connected to the positive electrode of the DC power supply 21. The first carbon anode electrode 23 is provided in the water-based electric discharge machining liquid 11 so as to be immersed in the water-based electric discharge machining liquid 11. The first carbon anode electrode 23 is disposed at a position that is higher than the workpiece 3 and does not hinder processing. The first carbon anode electrode 23 is preferably arranged perpendicular to the workpiece 3 placed horizontally on the work stand 2. In addition, it is preferable that the first carbon anode electrode 23 arranged vertically does not immerse the contact portion in the water-based electric discharge machining liquid 11 in order to prevent corrosion of the contact.

  The first carbon anode electrode 23 is disposed in the vicinity of the workpiece 3 within a distance sufficient to allow a corrosion-proof current to flow between at least the entire upper surface of the workpiece 3 and the first carbon anode electrode 23. The Since the first carbon anode electrode 24 is disposed in the processing tank 10 perpendicularly to the workpiece 3, the first carbon anode electrode 24 can be processed without obstructing the processing. Can be set as close as possible to the workpiece 3 within a sufficient distance that allows the anticorrosion current to flow between the entire upper surface of the second carbon anode electrode 23 and the second carbon anode electrode 23.

  The first carbon anode electrode 23 is a shape that can form electric lines of force between the entire upper surface of the workpiece 3, specifically, a flat plate or sheet-shaped carbon material, For example, it includes a material in which a carbon film is provided on a base material, such as a sheet-like material in which a carbon film is provided on a silicon rubber sheet. The first carbon anode electrode 23 is preferably a carbon fiber sheet, so-called carbon cloth. Here, the shape in which the lines of electric force can be formed between the entire upper surface of the workpiece 3 and the current density flowing between the workpiece 3 and the first carbon anode electrode 23 are required to be uniform. This indicates that the anticorrosion current can flow between at least the entire upper surface of the workpiece 3 and the first carbon anode electrode 23. Therefore, the first carbon anode electrode 23 is provided so as to substantially face the upper surface of the workpiece 3. Preferably, the first carbon anode electrode 23 has a sufficient area where a corrosion-proof current can flow between the upper surface of the workpiece 3.

  The second carbon anode electrode 24 is provided on the column of the work stand 2 at a position lower than the workpiece 3. The second carbon anode electrode 24 is made of a flexible sheet-like carbon material, and includes, for example, a material in which a carbon film is provided on a flexible substrate such as a sheet-like material in which a carbon film is provided on a silicon rubber sheet. . The second carbon anode electrode 23 is preferably a carbon fiber sheet, so-called carbon cloth. Therefore, the second carbon anode electrode 24 can be deformed unlike a plate-like or rod-like anode electrode. And the 2nd carbon anode electrode 24 is deform | transformed and arrange | positioned so that the external shape of the support | pillar of the work stand 2 may be followed. As described above, since the second carbon anode electrode 24 is disposed on the support column of the work stand 2, the second carbon anode electrode 24 can be formed on the entire upper surface of the workpiece 3 without interfering with processing. The workpiece 3 can be placed as close as possible to the workpiece 3 within a sufficient distance that allows the anticorrosion current to flow between the first carbon anode electrode 24 and the first carbon anode electrode 24.

  The second carbon anode electrode 24 has a shape capable of forming electric lines of force between the entire lower surface of the workpiece 3. Here, the shape capable of forming the lines of electric force does not require that the current density flowing between the workpiece 3 and the first carbon anode electrode 23 be uniform, and at least the workpiece 3 It shows that the anticorrosive current can flow between the entire upper surface of the electrode and the second carbon anode electrode 24. Therefore, the second carbon anode electrode 24 is provided so as to substantially face the lower surface of the workpiece 3. Preferably, the second carbon anode electrode 24 has a sufficient area where a corrosion-proof current can flow between the upper surface of the workpiece 3 and the second carbon anode electrode 24.

  In the embodiment, in order to dispose the second carbon anode electrode 24 as close to the work piece 3 as possible, the work stand 2 extends to the energized portion of the work stand 2 where the work piece 3 is energized. Therefore, an electrical insulating material 30 is provided between the energized part and the second carbon anode electrode 24 to insulate between the energized part and the second carbon anode electrode 24. In this way, by providing the second carbon anode electrode 24 extending to the energized portion of the work stand 2, rust is easily generated between the lower surface of the workpiece 3 and the energized portion of the work stand 2. It can be surely prevented.

  FIG. 2 shows a preferred embodiment of the first carbon anode electrode or the second carbon anode electrode. The main body 100 of the carbon anode electrode made of a sheet-like carbon material is a carbon cloth knitted in a cross shape. The main body 100 of the carbon anode electrode is affixed to a flexible insulating sheet 200 made of plastic or silicon with a water- and oil-resistant adhesive, double-sided tape, or the like, or is sewn with a synthetic fiber thread. Further, preferably, a plastic deep net-like flexible insulating net 300 made of plastic is affixed to the surface of the carbon cloth with a water- and oil-resistant adhesive, double-sided tape, or the like. Since the flexible net 300 has a mesh shape and does not shield the carbon anode electrode main body 100, electric lines of force are formed between the carbon anode electrode main body 100 and the entire surface of the workpiece 3. An anticorrosion current can be passed between the main body 100 of the carbon anode electrode and the entire surface of the workpiece 3. The insulating sheet 200 and the net 300 prevent the carbon anode electrode body 100 that is a carbon cloth from being broken.

  When used as the first carbon anode electrode 23, when the processing tank 10 is made of metal, the insulating sheet 200 causes a leakage current to flow between the main body 100 of the carbon anode electrode and the processing tank 10. Is prevented. Further, the net 300 prevents a conductive article from being sandwiched between the workpiece 3 and the main body 100 of the carbon anode electrode, thereby causing a short circuit. When used as the second carbon anode electrode 23, since the whole is flexible, it is not hindered to be deformed and disposed along the outer shape of the column. Moreover, since the insulating sheet 200 insulates the carbon anode electrode main body 100 from the current-carrying portion of the work stand 2, the insulating material 30 is unnecessary, and the second carbon anode electrode is covered as much as possible. It can be placed in the vicinity of the workpiece 3.

  The electric discharge machining apparatus according to the embodiment can be applied to an electric discharge machining apparatus including a machining liquid supply apparatus (not shown) that selectively supplies a water-based electric discharge machining liquid and an oil-based electric discharge machining liquid as the electric discharge machining liquid 11 to the machining tank 10. The anticorrosion circuit 20 supplies the anticorrosion current only when the water-based electric discharge machining liquid is supplied to the machining tank 10 from the machining liquid supply device.

  The electric discharge machining apparatus of the present invention is applied to electric discharge machining that uses an aqueous electric discharge machining liquid or electric discharge machining that switches between an aqueous electric discharge machining liquid and an oil electric discharge machining liquid. The electric discharge machining apparatus according to the present invention does not contain any harmful additive that adversely affects each member of the electric discharge machining or the machining liquid circuit that supplies the electric discharge machining liquid into the electric discharge machining liquid. It will surely prevent electric corrosion and contribute to the development of EDM.

1 is a side view partially including a cross section showing a main part in a preferred embodiment of an electric discharge machining apparatus of the present invention. It is a perspective view which shows preferable embodiment of the carbon anode electrode in the electric discharge machining apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Table 2 Work stand 3 Work piece 4 Processing head 5 Upper arm 6 Upper guide assembly 7 Lower arm 8 Lower guide assembly 9 Wire electrode 10 Processing tank 11 Electric discharge machining liquid 12 Power supply circuit 20 Processing corrosion protection circuit 21 DC power supply 22 Protective resistance 23 First carbon anode electrode 24 Second carbon anode electrode 30 Insulating material

Claims (2)

A work stand erected on the table; a workpiece fixedly attached to the work stand; a machining tank provided on the table so as to surround the workpiece; 1st carbon which has a shape which can be formed in the position which is higher than the above-mentioned work piece so as not to interfere with machining and can form electric lines of force between the entire upper surface of the work piece so as to be immersed in a working fluid Between the anode electrode and a sheet-like carbon material, the work stand column positioned lower than the workpiece is deformed along the outer shape of the column and disposed between the entire lower surface of the workpiece. The second carbon anode electrode having a shape capable of forming electric lines of force, the first carbon anode electrode, and the second carbon anode electrode are connected to a positive electrode, and the workpiece is connected to a negative electrode to prevent corrosion. DC power supply that supplies current Discharge machining apparatus provided with a cathodic protection circuit, the. 2. The electric discharge machining apparatus according to claim 1, wherein the first carbon anode electrode and the second carbon anode electrode have a sufficient area for a corrosion-proof current to flow between the entire upper surface of the workpiece.

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