Electric discharge machine and chemical adding method

Abstract

This electric discharge machine is provided with: an electric discharge machining unit that performs electric discharge machining on a workpiece in a machining fluid; and a filter for removing sludge contained in the machining liquid, the electric discharge machine performing electric discharge machining using the machining liquid containing cations of a metal having a lower standard electrode potential than the standard electrode potential of aluminum when the workpiece is made of an aluminum-based material.

Description

Technical Field

[0001] The present invention relates to an electrical discharge machine and a method for adding a chemical. Background Art

[0002] International Publication No. 2006 / 126248 discloses an electrical discharge machine. Summary of the invention

[0003] Recently, there is a desire for better electrical discharge machines and chemical adding methods.

[0004] The first embodiment of the present invention is an electric discharge machine comprising: an electric discharge machining section which performs electric discharge machining on a workpiece in a machining fluid; and a filter which removes sludge contained in the machining fluid. When the workpiece is composed of an aluminum-based material, the electric discharge machine uses the machining fluid containing cations of a metal whose standard electrode potential is lower than that of aluminum to perform the electric discharge machining.

[0005] A second aspect of the present invention is a method for adding a chemical to a machining fluid of an electric discharge machine, the electric discharge machine comprising: an electric discharge machining section that performs electric discharge machining on a workpiece in the machining fluid; and a filter that removes sludge contained in the machining fluid, wherein the machining fluid contains cations of a first metal having a standard electrode potential lower than that of aluminum by adding a first chemical to the machining fluid, and the machining fluid contains cations of a second metal having a standard electrode potential lower than that of the first metal by adding a second chemical to the machining fluid, the method comprising: a chemical determination step of determining the chemical to be added to the machining fluid; and an adding step of increasing the amount of the first chemical to be added to the machining fluid compared to the amount of the second chemical to be added to the machining fluid, and decreasing the amount of the second chemical to be added to the machining fluid compared to the amount of the first chemical to be added to the machining fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 This is a schematic diagram of an electrical discharge machine. Figure 2 This is a block diagram showing the configuration of a control device. Figure 3 This is a graph showing the standard electrode potential of the metal of the cation contained in the machining fluid and the life of the filter. Figure 4 This is a flowchart showing the drug addition process executed in the control device. DETAILED DESCRIPTION

[0007] The EDM machine performs electrical discharge machining on a workpiece in a machining fluid. The machining fluid used in the EDM contains sludge generated during the EDM. The machining fluid used in the EDM is filtered to remove the sludge and is reused. When the machining fluid is filtered, the sludge adheres to the filter.

[0008] When the filter mesh is clogged due to the adhesion of sludge and the resistance of the filter increases, the user needs to replace the filter. The used filter is usually not reused but discarded. In order to reduce the number of times the filter is replaced and the amount of filter discarded, it is required to extend the life of the filter.

[0009] Compared with the case where the EDM machine performs EDM on a workpiece made of an aluminum material, the life of the filter for the EDM machine becomes shorter when the EDM machine performs EDM on a workpiece made of an iron material. When the EDM machine performs EDM on a workpiece made of an aluminum material, aluminum hydroxide is generated in the machining fluid. It is believed that aluminum hydroxide gels when in contact with water for a long time, and the gelled aluminum hydroxide adheres to the filter, thereby shortening the life of the filter. The life of the filter for the EDM machine when performing EDM on a workpiece made of an aluminum material is 10% to 25% of the life of the filter for the EDM machine when performing EDM on a workpiece made of an iron material.

[0010] Therefore, when an electric discharge machine is used to perform electric discharge machining on a workpiece made of an aluminum material, there is a problem that the number of times a user replaces the filter increases and the amount of filter waste increases. The technical subject of the present invention is to provide an electric discharge machine and a reagent adding method, which can extend the life of the filter of the electric discharge machine when performing electric discharge machining on an aluminum material.

[0011] [Implementation Method] [Structure of electrical discharge machine] Figure 1 1 is a schematic diagram of an electrical discharge machine 10. The electrical discharge machine 10 includes an electrical discharge machining unit 12, a machining fluid treatment unit 14, and a control device 16. The electrical discharge machine 10 is a wire electrical discharge machine.

[0012] The electrical discharge machining unit 12 has a machining groove 18 . The electrical discharge machining unit 12 performs electrical discharge machining on a workpiece in a machining fluid stored in the machining groove 18 .

[0013] The machining fluid treatment unit 14 includes a dirty fluid tank 20 , a clean fluid tank 22 , an ion exchange unit 24 , an addition unit 26 , and a resistivity measurement unit 28 .

[0014] The machining fluid used in the electrical discharge machining is discharged from the machining tank 18 to the dirty liquid tank 20 through the drainage path 29. The machining fluid discharged from the machining tank 18 contains sludge generated during the electrical discharge machining.

[0015] The machining fluid stored in the dirty liquid tank 20 is sent to the clean liquid tank 22 through the filter path 30. The filter path 30 includes a first pump 32 and a filter 34. The first pump 32 delivers the machining fluid from the dirty liquid tank 20 to the clean liquid tank 22. The filter 34 filters the machining fluid sent from the dirty liquid tank 20 to the clean liquid tank 22 to remove sludge from the machining fluid.

[0016] The machining liquid stored in the clean liquid tank 22 circulates between the clean liquid tank 22 and the ion exchange unit 24 or between the clean liquid tank 22 and the adding unit 26 through the circulation path 36. A second pump 38 is provided on the circulation path 36. The second pump 38 supplies the machining liquid in the clean liquid tank 22 to the ion exchange unit 24 or the adding unit 26.

[0017] The ion exchange unit 24 includes a first valve 40 and an ion exchange resin 42. When the electric discharge machining unit 12 performs electric discharge machining on a workpiece made of a material other than an aluminum-based material, the first valve 40 is opened and the second valve 44 described later is closed. Thus, machining fluid is supplied from the clean fluid tank 22 to the ion exchange unit 24. The ion exchange resin 42 captures specific ions contained in the machining fluid passing through the ion exchange resin 42 and releases other ions.

[0018] The adding unit 26 includes a second valve 44 and a chemical storage unit 46. When the electrical discharge machining unit 12 performs electrical discharge machining on a workpiece made of an aluminum material, the second valve 44 is opened and the first valve 40 is closed.

[0019] The reagent storage section 46 adds a reagent for reducing the resistivity value to the machining fluid passing through the reagent storage section 46. The reagent added to the machining fluid is, for example, sodium bisulfite, sodium carbonate, sodium sulfate, calcium hydroxide, sodium disulfite (sodium pyrosulfite), potassium disulfite (potassium pyrosulfite), magnesium sulfate, magnesium sulfate heptahydrate, etc. The reagent may also be a compound other than the above compounds. The reagent may include one compound. The reagent may include two or more compounds.

[0020] By adding the agent to the machining fluid, the machining fluid contains one or more cations of metal cations having a standard electrode potential lower than that of aluminum. The metal cations having a standard electrode potential lower than that of aluminum are lithium ions, potassium ions, calcium ions, sodium ions, and magnesium ions. That is, the machining fluid may contain one or more cations of lithium ions, potassium ions, calcium ions, sodium ions, and magnesium ions.

[0021] In addition, by adding a chemical to the machining fluid, one or more of the following anions are contained in the machining fluid. Anions include sulfate ions, sulfite ions, disulfite ions, bisulfite ions, hydroxide ions, nitrate ions, and nitrite ions. That is, the machining fluid may contain one or more of the following anions: sulfate ions, sulfite ions, disulfite ions, bisulfite ions, hydroxide ions, nitrate ions, and nitrite ions.

[0022] The resistivity measuring unit 28 measures the resistivity of the machining fluid stored in the clear fluid tank 22. The adding unit 26 is controlled by the control device 16 based on the resistivity. The machining fluid with adjusted resistivity is sent from the clear fluid tank 22 to the machining tank 18 through the supply path 48.

[0023] [Control device configuration] Figure 2 1 is a block diagram showing the structure of the control device 16. The control device 16 has a computing unit 50 and a storage unit 52. The computing unit 50 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The computing unit 50 includes a resistivity value acquisition unit 54, a drug addition amount information acquisition unit 56, and a control unit 60. The resistivity value acquisition unit 54, the drug addition amount information acquisition unit 56, and the control unit 60 are implemented by executing a program stored in the storage unit 52 in the computing unit 50. At least a part of the resistivity value acquisition unit 54, the drug addition amount information acquisition unit 56, and the control unit 60 can be implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). At least a part of the resistivity value acquisition unit 54, the drug addition amount information acquisition unit 56, and the control unit 60 can be implemented by an electronic circuit including discrete devices.

[0024] The storage unit 52 is composed of a volatile memory (not shown) and a non-volatile memory (not shown) as a computer-readable storage medium. Examples of the volatile memory are RAM (Random Access Memory) and the like. Examples of the non-volatile memory are ROM (Read Only Memory), flash memory and the like. Data and the like are stored in the volatile memory, for example. Programs, tables, mappings and the like are stored in the non-volatile memory, for example. At least a portion of the storage unit 52 may also be provided in the above-mentioned processor, integrated circuit and the like. At least a portion of the storage unit 52 may also be mounted on a device connected to the electrical discharge machine 10 via a network.

[0025] The resistivity value acquisition unit 54 acquires information on the resistivity value of the machining fluid stored in the clear fluid tank 22 from the resistivity value measurement unit 28. The reagent addition amount information acquisition unit 56 acquires the reagent addition amount information from the storage unit 52. The reagent addition amount information is information on the amount of reagent added to the machining fluid when the workpiece is made of an aluminum-based material. The reagent addition amount information of each reagent is stored in the storage unit 52. The control unit 60 controls the adding unit 26. The control method of the adding unit 26 will be described in detail later.

[0026] [About experimental results] The inventors of the present invention conducted an experiment in which an aluminum-based workpiece was subjected to electrical discharge machining in a plurality of machining fluids containing different cations, and the life of the filter 34 was determined.

[0027] Figure 3 This is a graph showing the standard electrode potential of the metal of the cation contained in the machining fluid and the life of the filter 34. The machining fluid containing the cation of each metal has the same resistivity value.

[0028] like Figure 3 As shown, it was confirmed that the life of the filter 34 was longer when the machining fluid contained cations of a metal having a standard electrode potential lower than that of aluminum than when the machining fluid contained aluminum ions.

[0029] In addition, if Figure 3 As shown, it was confirmed that the lower the standard electrode potential of the metal of the cation contained in the machining fluid, the longer the life of the filter 34.

[0030] When sodium bisulfite is added to the machining fluid, aluminum oxide and aluminum trihydrate are generated in the machining fluid during electrical discharge machining of a workpiece made of an aluminum material. On the other hand, when sodium bisulfite is not added to the machining fluid, aluminum hydroxide is generated in the machining fluid during electrical discharge machining of a workpiece made of an aluminum material. It is considered that by adding sodium bisulfite to the machining fluid, aluminum oxide and aluminum trihydrate are generated to replace aluminum hydroxide that shortens the life of the filter 34.

[0031] When sodium carbonate, sodium sulfate, calcium hydroxide, sodium disulfite (sodium metabisulfite), potassium disulfite (potassium metabisulfite), magnesium sulfate, or magnesium sulfate heptahydrate is added to the working fluid, the generation of aluminum hydroxide can be suppressed.

[0032] [Drug Addition Processing] Figure 4 2 is a flowchart showing the chemical addition process executed by the control device 16. The chemical addition process is repeatedly executed at a predetermined cycle while the workpiece made of an aluminum-based material is being machined by the electric discharge machining unit 12.

[0033] In step S1, the resistivity value acquisition unit 54 acquires information on the resistivity value of the machining fluid from the resistivity value measurement unit 28. Then, the process moves to step S2.

[0034] In step S2, the control unit 60 determines whether the resistivity value of the machining fluid is below a predetermined value based on the resistivity value information acquired by the resistivity value acquisition unit 54. If the resistivity value of the machining fluid is below the predetermined value, the process moves to step S3, and if the resistivity value of the machining fluid is greater than the predetermined value, the chemical addition process ends.

[0035] In step S3 , the control unit 60 determines the chemical to be added to the machining fluid. Then, the process moves to step S4 . The chemical to be added to the machining fluid may be input to the control device 16 by the user of the electrical discharge machine 10 .

[0036] In step S4, the chemical addition amount information acquisition unit 56 acquires chemical addition amount information from the storage unit 52. The chemical addition amount information, which is information on the amount of each chemical added to the machining fluid, is stored in the storage unit 52. Then, the process moves to step S5.

[0037] In step S5, the control unit 60 controls the adding unit 26 according to the drug addition amount information. Then, the drug addition process is terminated. The control unit 60 controls the drug supply device (not shown) to supply the drug in the amount of drug addition corresponding to the drug determined in step S3 to the drug storage unit 46. Then, the control unit 60 opens the second valve 44. Thus, the drug in the amount of drug addition based on the drug addition amount information is added.

[0038] [About the amount of medicine added] The amount of the reagent to be added is determined based on the standard electrode potential of the metal constituting the compound contained in the reagent. The amount of the reagent to be added is described below using the first and second reagents as examples.

[0039] The standard electrode potential of the metal constituting the compound contained in the first agent is lower than the standard electrode potential of aluminum. For example, an agent containing magnesium sulfate can be selected as the first agent. By adding the agent containing magnesium sulfate to the machining fluid, magnesium cations are contained in the machining fluid. The standard electrode potential of magnesium is lower than the standard electrode potential of aluminum.

[0040] The standard electrode potential of the metal constituting the compound contained in the second agent is lower than the standard electrode potential of the metal constituting the compound contained in the first agent. For example, an agent containing sodium sulfate can be selected as the second agent. By adding the agent containing sodium sulfate to the machining fluid, sodium cations are contained in the machining fluid. The standard electrode potential of sodium is lower than the standard electrode potential of magnesium.

[0041] The storage unit 52 stores information on the amount of chemical added when the second chemical is added to the machining fluid, indicating that the amount of the second chemical added is smaller than the amount of the first chemical added when the first chemical is added to the machining fluid.

[0042] like Figure 3 As shown in FIG. 1 , even when the resistivity value of the machining fluid is the same, the life of the filter 34 is longer when the machining fluid contains sodium cations than when the machining fluid contains magnesium cations. Therefore, when the first agent is added to the machining fluid, the amount of the first agent added is increased compared to the amount of the second agent added when the second agent is added to the machining fluid, thereby ensuring the length of the life of the filter 34. In addition, when the second agent is added to the machining fluid, the amount of the second agent added is reduced compared to the amount of the first agent added when the first agent is added to the machining fluid, thereby ensuring the length of the life of the filter 34.

[0043] In the above description, the control device 16 controls the adding unit 26 to add the chemical to the machining fluid, but the user of the electrical discharge machine 10 may add the chemical to the machining fluid.

[0044] When the user adds a chemical to the machining fluid, the user determines the chemical to be added. When the first chemical is added to the machining fluid, the user increases the amount of the first chemical added compared to the amount of the second chemical added when the second chemical is added to the machining fluid. On the other hand, when the second chemical is added to the machining fluid, the user decreases the amount of the second chemical added compared to the amount of the first chemical added when the first chemical is added to the machining fluid.

[0045] The following additional remarks are disclosed in relation to the above-mentioned embodiment.

[0046] (Note 1) An electric discharge machine (10) comprises: an electric discharge machining section (12) for performing electric discharge machining on a workpiece in a machining fluid; and a filter (34) for removing sludge contained in the machining fluid. When the workpiece is made of an aluminum-based material, the electric discharge machine performs the electric discharge machining using the machining fluid containing cations of a metal having a standard electrode potential lower than that of aluminum.

[0047] (Note 2) In the electrical discharge machine according to Supplementary Note 1, the machining fluid may contain one or more anions of sulfate ion, sulfite ion, disulfite ion, hydrogensulfite ion, hydroxide ion, nitrate ion, and nitrite ion.

[0048] (Note 3) In the electric discharge machine described in Note 1 or 2, a first agent can be added to the machining fluid, wherein the machining fluid contains cations of a first metal whose standard electrode potential is lower than that of aluminum, and a second agent can be added to the machining fluid, wherein the machining fluid contains cations of a second metal whose standard electrode potential is lower than that of the first metal. The electric discharge machine comprises: an agent addition amount information acquisition unit (56), which acquires agent addition amount information from a storage unit (52), wherein the storage unit stores information on the amount of agent added to the machining fluid when the workpiece is made of the aluminum-based material, i.e., the agent addition amount information; an adding unit (26), which adds the agent to the machining fluid; and a control unit (60), which controls the machining process based on the agent addition amount information. The adding unit stores the following information on the amount of the agent added in the storage unit, namely, when the second agent is added to the machining fluid, the amount of the second agent added is less than the amount of the first agent added to the machining fluid; when the first agent is added to the machining fluid, the control unit controls the adding unit based on the information on the amount of the agent added to increase the amount of the first agent added compared to the amount of the second agent added when the second agent is added to the machining fluid; and when the second agent is added to the machining fluid, the control unit controls the adding unit based on the information on the amount of the agent added to decrease the amount of the second agent added compared to the amount of the first agent added when the first agent is added to the machining fluid.

[0049] (Note 4) A method for adding a chemical to a machining fluid of an electric discharge machine, the electric discharge machine comprising: an electric discharge machining section for performing electric discharge machining on a workpiece in the machining fluid; and a filter for removing sludge contained in the machining fluid, wherein the machining fluid contains cations of a first metal having a standard electrode potential lower than that of aluminum by adding a first chemical to the machining fluid, and the machining fluid contains cations of a second metal having a standard electrode potential lower than that of the first metal by adding a second chemical to the machining fluid, the method comprising: a chemical determination step for determining the chemical to be added to the machining fluid; and an adding step for increasing the amount of the first chemical to be added to the machining fluid compared to the amount of the second chemical to be added to the machining fluid, and decreasing the amount of the second chemical to be added to the machining fluid compared to the amount of the first chemical to be added to the machining fluid.

[0050] Although the present invention has been described in detail, the present invention is not limited to the above-mentioned embodiments. These embodiments may be variously added, replaced, changed, partially deleted, etc. without departing from the scope of the main idea of ​​the present invention, or without departing from the scope of the main idea of ​​the present invention derived from the contents recorded in the claims and their equivalents. In addition, these embodiments may also be implemented in combination. For example, in the above-mentioned embodiments, the order of each action and the order of each processing are shown as an example, and are not limited thereto. In addition, the same applies to the case where numerical values ​​or mathematical formulas are used in the description of the above-mentioned embodiments. Explanation of symbols

[0051] 10…Electrical discharge machine 12…Electrical discharge machining unit 26 ... Adding unit 34 ... Filter 52 ... storage unit 56 ... medicine addition amount information acquisition unit 60…Control Department.

Claims

1. An electrical discharge machine comprising: an electrical discharge machining unit for performing electrical discharge machining on a workpiece in a machining fluid; and a filter for removing sludge contained in the machining fluid, wherein: When the workpiece is made of an aluminum-based material, the electrical discharge machining is performed using the machining fluid containing cations of a metal having a standard electrode potential lower than that of aluminum.

2. The electrical discharge machine according to claim 1, characterized in that The working fluid contains one or more anions of sulfate ion, sulfite ion, disulfite ion, hydrogensulfite ion, hydroxide ion, nitrate ion, and nitrite ion.

3. The electrical discharge machine according to claim 1 or 2, characterized in that: By adding the first agent to the machining fluid, the machining fluid contains cations of a first metal having a standard electrode potential lower than that of aluminum, By adding a second agent to the machining fluid, the machining fluid contains cations of a second metal having a standard electrode potential lower than that of the first metal, The electrical discharge machine comprises: a reagent addition amount information acquisition unit that acquires reagent addition amount information from a storage unit that stores information on the amount of reagent added to the machining fluid when the workpiece is made of the aluminum-based material, that is, the reagent addition amount information; an adding unit that adds the agent to the machining fluid; and a control unit that controls the adding unit based on the drug addition amount information, The storage unit stores the agent addition amount information such that the addition amount of the second agent when the second agent is added to the machining fluid is less than the addition amount of the first agent when the first agent is added to the machining fluid, When the first agent is added to the machining fluid, the control unit controls the adding unit based on the agent addition amount information to increase the addition amount of the first agent compared to the addition amount of the second agent when the second agent is added to the machining fluid. When the second agent is added to the machining fluid, the control unit controls the adding unit based on the agent addition amount information to reduce the amount of the second agent added compared to the amount of the first agent added when the first agent is added to the machining fluid.

4. A method for adding a chemical, comprising adding a chemical to a machining fluid of an electrical discharge machine, the electrical discharge machine comprising: an electrical discharge machining unit for performing electrical discharge machining on a workpiece in the machining fluid; and a filter for removing sludge contained in the processing fluid, wherein the agent adding method is characterized in that: By adding the first agent to the machining fluid, the machining fluid contains cations of a first metal having a standard electrode potential lower than that of aluminum, By adding a second agent to the machining fluid, the machining fluid contains cations of a second metal having a standard electrode potential lower than that of the first metal, The drug adding method comprises: A reagent determination step, determining the reagent to be added to the processing fluid; as well as The step of adding: when the first agent is added to the machining fluid, the amount of the first agent added is increased compared to the amount of the second agent added to the machining fluid; and when the second agent is added to the machining fluid, the amount of the second agent added is reduced compared to the amount of the first agent added to the machining fluid.

Images