Electric discharge machine and electric discharge machining method

Abstract

This electric discharge machine is provided with: a discharge machining unit that performs electric discharge machining on a workpiece in a machining fluid; and a filter that removes sludge contained in the machining fluid. When the workpiece is made of an aluminum-based material, electric discharge machining is performed using a machining fluid in which the specific resistivity has been reduced to a prescribed value or less due to addition of a chemical agent, and the prescribed value is equal to or less than 30,000 [Ωcm].

Description

Electric discharge machining machine and electric discharge machining method

[0001] The present disclosure relates to an electric discharge machine and an electric discharge machining method.

[0002] WO 2006 / 126248 discloses an electric discharge machine.

[0003] Recently, there has been a demand for better electrical discharge machines and electrical discharge machining methods.

[0004] A first aspect of the present disclosure is an electric discharge machine for electric discharge machining of a workpiece, the electric discharge machine comprising: an electric discharge machining section that performs electric discharge machining on the workpiece in a machining fluid; and a filter that removes sludge contained in the machining fluid; and when the workpiece is made of an aluminum-based material, the electric discharge machining is performed using the machining fluid whose resistivity has been reduced to a predetermined value or less by adding an agent, the predetermined value being 30,000 Ωcm or less.

[0005] A second aspect of the present disclosure is an electric discharge machining method using an electric discharge machine including an electric discharge machining unit that performs electric discharge machining on a workpiece in machining fluid and a filter that removes sludge contained in the machining fluid, the electric discharge machining method comprising: a resistivity value acquisition step of acquiring information indicating a resistivity value of the machining fluid; an addition step of adding a chemical to the machining fluid to reduce the resistivity value of the machining fluid to the predetermined value or less, if the workpiece is made of an aluminum-based material and the resistivity value of the machining fluid is higher than a predetermined value; and an electric discharge machining step of performing the electric discharge machining on the workpiece made of the aluminum-based material in the machining fluid whose resistivity has been reduced to the predetermined value or less, wherein the predetermined value is a value of 30,000 Ωcm or less.

[0006] FIG. 1 is a schematic diagram of an electric discharge machine. FIG. 2 is a block diagram showing the configuration of a control device. FIG. 3 is a flowchart showing a chemical addition process executed by the control device. FIG. 4 is a graph showing the relationship between the resistivity of the machining fluid and the lifespan of a filter. FIG. 5 is a graph showing the relationship between the resistivity of the machining fluid and the lifespan of a filter. FIG. 6 is a graph showing the relationship between the resistivity of the machining fluid and the lifespan of a filter. FIG. 7 is a graph showing the relationship between the resistivity of the machining fluid and the lifespan of a filter. FIG. 8 is a graph showing the relationship between the resistivity of the machining fluid and the lifespan of a filter. FIG. 9 is a graph showing the relationship between the resistivity of the machining fluid and the lifespan of a filter. FIG. 10 is a graph showing the relationship between the resistivity of the machining fluid and the lifespan of a filter. FIG. 11 is a graph showing the relationship between the resistivity of the machining fluid and the lifespan of a filter. FIG. 12 is a schematic diagram of an electric discharge machine. FIG. 13 is a block diagram showing the configuration of the control device. FIG. 14 is a flowchart showing a chemical addition process executed by the control device.

[0007] Electrical discharge machines perform electrical discharge machining on a workpiece in machining fluid. The machining fluid used in electrical discharge machining contains sludge generated during the machining process. The machining fluid used in electrical discharge machining is reused after the sludge is removed using a filter. As the machining fluid is filtered, sludge adheres to the filter.

[0008] When the filter becomes clogged with sludge and the filter resistance increases, the user must replace the filter. After use, the filter is usually discarded without being reused. To reduce the frequency of filter replacement and the amount of discarded filters, it is necessary to extend the filter's lifespan.

[0009] When an electric discharge machine performs electric discharge machining on a workpiece made of an aluminum-based material, the life of the electric discharge machine filter is shorter than when the electric discharge machine performs electric discharge machining on a workpiece made of an iron-based material. When electric discharge machining is performed on a workpiece made of an aluminum-based material, aluminum hydroxide is produced in the machining fluid. Aluminum hydroxide gels when in contact with water for a long period of time, and it is thought that the gelled aluminum hydroxide adheres to the filter, shortening the filter's life. The life of an electric discharge machine filter when electric discharge machining is performed on a workpiece made of an aluminum-based material is 10% to 25% of the life of an electric discharge machine filter when electric discharge machining is performed on a workpiece made of an iron-based material.

[0010] Therefore, when an electric discharge machine performs electric discharge machining on a workpiece made of an aluminum-based material, there is a problem that the user has to replace the filter more frequently and the amount of filter waste increases. An object of the technology disclosed herein is to provide an electric discharge machine and an electric discharge machining method that can extend the life of the filter of the electric discharge machine when electric discharge machining is performed on an aluminum-based material.

[0011] 1 is a schematic diagram of an electric discharge machine 10. The electric discharge machine 10 has an electric discharge machining unit 12, a machining fluid treatment unit 14, and a control device 16. The electric discharge machine 10 is a wire electric discharge machine.

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

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

[0014] The machining fluid used in the electric discharge machining is discharged from the machining tank 18 through a drainage path 30 into the waste fluid tank 20. The machining fluid discharged from the machining tank 18 contains sludge generated during the electric discharge machining.

[0015] The machining fluid stored in the waste fluid tank 20 is sent to the clean fluid tank 22 through a filtration path 32. A first pump 34 and a filter 36 are provided in the filtration path 32. The first pump 34 sends the machining fluid from the waste fluid tank 20 to the clean fluid tank 22. The filter 36 filters the machining fluid sent from the waste fluid tank 20 to the clean fluid tank 22 and removes sludge from the machining fluid.

[0016] The machining fluid stored in the clean liquid tank 22 circulates through a circulation path 38 between the clean liquid tank 22 and the ion exchange unit 24, or between the clean liquid tank 22 and the adding unit 26. A second pump 40 is provided in the circulation path 38. The second pump 40 supplies the machining fluid in the clean liquid tank 22 to the ion exchange unit 24 or the adding unit 26.

[0017] The ion exchange unit 24 has a first valve 42 and an ion exchange resin 44. 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 42 is opened and a second valve 46, which will be described later, is closed. This allows the machining fluid to be supplied from the clean fluid tank 22 to the ion exchange unit 24. The ion exchange resin 44 captures specific ions contained in the machining fluid passing through the ion exchange resin 44 and releases other ions.

[0018] The adding section 26 has a second valve 46 and a chemical reservoir 48. When the electric discharge machining section 12 performs electric discharge machining on a workpiece made of an aluminum-based material, the second valve 46 is opened and the first valve 42 is closed. This allows the machining fluid to be supplied from the clean fluid tank 22 to the chemical reservoir 48.

[0019] The chemical reservoir 48 adds a chemical that reduces the resistivity of the machining fluid to the machining fluid passing through the chemical reservoir 48. Examples of the chemical added to the machining fluid include sodium bisulfite, calcium hydroxide, magnesium sulfate, sodium bisulfate, potassium disulfite (potassium pyrosulfite), sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, calcium sulfate, potassium sulfite, calcium sulfite, sodium sulfite, potassium hydrogen sulfate, calcium hydrogen sulfate, potassium bisulfite, calcium hydrogen sulfite, sodium bisulfite, sodium thiosulfate, tripotassium citrate, calcium citrate, sodium citrate, monosodium citrate, disodium citrate, trisodium citrate, magnesium citrate, sodium nitrate, magnesium nitrate, magnesium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, sodium percarbonate, magnesium percarbonate, potassium hydrogen carbonate, calcium hydrogen carbonate, calcium peroxide, potassium phosphate, monophosphate, Potassium, dipotassium phosphate, tripotassium phosphate, calcium phosphate, sodium phosphate, trisodium phosphate, magnesium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, calcium hydrogen phosphate, dicalcium hydrogen phosphate, disodium hydrogen phosphate, sodium monohydrogen phosphate, potassium alginate, sodium alginate, sodium oleate, potassium acetate, calcium acetate, calcium acetate monohydrate, sodium acetate, sodium acetate trihydrate, magnesium acetate, magnesium acetate tetrahydrate, potassium tartrate, sodium tartrate, sodium tartrate dihydrate, sodium potassium tartrate, potassium hydrogen tartrate, sodium hydrogen tartrate, sodium hydrogen tartrate monohydrate, sodium benzoate, sodium stearate, magnesium stearate, potassium formate, sodium formate, potassium permanganate, and calcium iodate.

[0020] By adding the agent to the machining fluid, the machining fluid contains one or more types of cations of metals 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, cesium ions, rubidium ions, potassium ions, barium ions, strontium ions, calcium ions, sodium ions, magnesium ions, thorium ions, and beryllium ions. That is, the machining fluid may contain one or more types of cations of lithium ions, cesium ions, rubidium ions, potassium ions, calcium ions, sodium ions, and magnesium ions. The machining fluid may also contain cations other than potassium ions, barium ions, strontium ions, calcium ions, sodium ions, magnesium ions, thorium ions, and beryllium ions.

[0021] Furthermore, by adding a chemical to the machining fluid, the machining fluid contains one or more of the following anions: sulfate ions, sulfite ions, disulfite ions, hydroxide ions, and hydrogen sulfate ions. That is, the machining fluid may contain one or more of sulfate ions, sulfite ions, disulfite ions, hydroxide ions, and hydrogen sulfate ions. The machining fluid may also contain anions other than sulfate ions, sulfite ions, disulfite ions, hydrogen sulfate ions, and hydroxide ions.

[0022] The resistivity measuring unit 28 measures the resistivity of the machining fluid stored in the clean fluid tank 22. The adding unit 26 is controlled by the control device 16 based on the resistivity. The machining fluid whose resistivity has been adjusted is sent from the clean fluid tank 22 to the machining tank 18 through a supply path 50. The resistivity measuring unit 28 may measure the resistivity of the machining fluid stored in the dirty fluid tank 20. The resistivity measuring unit 28 may measure the resistivity of the machining fluid stored in the machining tank 18.

[0023] [Configuration of Control Device] Fig. 2 is a block diagram showing the configuration of the control device 16. The control device 16 has a calculation unit 52 and a storage unit 54. The calculation unit 52 is a processor such as a central processing unit (CPU) or a graphics processing unit (GPU). The calculation unit 52 includes a resistivity value acquisition unit 56 and a control unit 58. The resistivity value acquisition unit 56 and the control unit 58 are realized by the calculation unit 52 executing a program stored in the storage unit 54. At least a portion of the resistivity value acquisition unit 56 and the control unit 58 may be realized by an integrated circuit such as an application specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). At least a portion of the resistivity value acquisition unit 56 and the control unit 58 may be realized by an electronic circuit including discrete devices.

[0024] The storage unit 54 is configured with a volatile memory (not shown) and a non-volatile memory (not shown), which are computer-readable storage media. The volatile memory is, for example, a random access memory (RAM). The non-volatile memory is, for example, a read-only memory (ROM) or a flash memory. Data, for example, is stored in the volatile memory. Programs, tables, maps, for example, are stored in the non-volatile memory. At least a portion of the storage unit 54 may be provided in the processor, integrated circuit, etc. described above. At least a portion of the storage unit 54 may be mounted on a device connected to the electric discharge machine 10 via a network.

[0025] The resistivity value acquiring unit 56 acquires information indicating the resistivity value of the machining fluid from the resistivity value measuring unit 28. The control unit 58 controls the adding unit 26. A control method for the adding unit 26 will be described in detail later.

[0026] [Regarding the relationship between the resistivity of the machining fluid and the filter life] When the electric discharge machine 10 performs electric discharge machining on a workpiece made of an aluminum-based material, the life of the filter 36 is shorter than when the electric discharge machine 10 performs electric discharge machining on a workpiece made of an iron-based material.

[0027] The inventors of the present invention have experimentally confirmed that the filter life is longer when electric discharge machining is performed on a workpiece made of an aluminum-based material in a machining fluid in which a chemical has been added to reduce the resistivity to 30,000 [Ωcm] or less, compared to when electric discharge machining is performed on a workpiece made of an aluminum-based material in a normal machining fluid with a resistivity of approximately 70,000 to 100,000 [Ωcm].

[0028] The life of the filter 36 is indicated by the total time during which the workpiece is machined in the electric discharge machining section 12 during the period from when an unused filter 36 is attached to the electric discharge machine 10 until the discharge pressure of the machining fluid discharged from the first pump 34 reaches a predetermined pressure.

[0029] Sodium bisulfite, calcium hydroxide, magnesium sulfate, sodium sulfate, potassium disulfite (potassium metabisulfite), sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, calcium sulfate, potassium sulfite, calcium sulfite, sodium sulfite, potassium hydrogen sulfate, calcium hydrogen sulfate, potassium hydrogen sulfite, calcium hydrogen sulfite, sodium disulfite, sodium thiosulfate, tripotassium citrate, calcium citrate, sodium citrate, monosodium citrate, disodium citrate, trisodium citrate, magnesium citrate, sodium nitrate, magnesium nitrate, magnesium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, sodium percarbonate, magnesium percarbonate, potassium bicarbonate, calcium bicarbonate, calcium peroxide, potassium phosphate, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, calcium phosphate The resistivity of the machining fluid can be reduced by adding an agent containing a compound such as ammonium, sodium phosphate, trisodium phosphate, magnesium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, calcium hydrogen phosphate, dicalcium hydrogen phosphate, disodium hydrogen phosphate, sodium monohydrogen phosphate, potassium alginate, sodium alginate, sodium oleate, potassium acetate, calcium acetate, calcium acetate monohydrate, sodium acetate, sodium acetate trihydrate, magnesium acetate, magnesium acetate tetrahydrate, potassium tartrate, sodium tartrate, sodium tartrate dihydrate, sodium potassium tartrate, potassium hydrogen tartrate, sodium hydrogen tartrate, sodium hydrogen tartrate monohydrate, sodium benzoate, sodium stearate, magnesium stearate, potassium formate, sodium formate, potassium permanganate, or calcium iodate to the machining fluid.

[0030] When electrical discharge machining is performed on a workpiece made of an aluminum-based material in a normal machining fluid, aluminum hydroxide is generated in the machining fluid. Aluminum hydroxide gels when in contact with water for a long period of time, and the gelled aluminum hydroxide adheres to the filter 36, shortening the life of the filter 36.

[0031] When sodium bisulfite is added as a chemical to the machining fluid, aluminum oxide and aluminum oxide trihydrate are produced in the machining fluid during electrical discharge machining of an aluminum-based workpiece. It is believed that the addition of sodium bisulfite to the machining fluid produces aluminum oxide and aluminum oxide trihydrate instead of aluminum hydroxide, which shortens the life of the filter 36.

[0032] Machining fluids include calcium hydroxide, magnesium sulfate, sodium hydrogen sulfate, potassium disulfite (potassium pyrosulfite), sodium bicarbonate, sodium carbonate, sodium sulfate, potassium sulfate, calcium sulfate, potassium sulfite, calcium sulfite, sodium sulfite, potassium hydrogen sulfate, calcium hydrogen sulfate, potassium hydrogen sulfite, calcium hydrogen sulfite, sodium disulfite, sodium thiosulfate, tripotassium citrate, calcium citrate, sodium citrate, monosodium citrate, disodium citrate, trisodium citrate, magnesium citrate, sodium nitrate, magnesium nitrate, magnesium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, sodium percarbonate, magnesium percarbonate, potassium hydrogen carbonate, calcium hydrogen carbonate, calcium peroxide, potassium phosphate, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, phosphoric acid It is believed that the production of aluminum hydroxide is also suppressed when calcium, sodium phosphate, trisodium phosphate, magnesium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, calcium hydrogen phosphate, dicalcium hydrogen phosphate, disodium hydrogen phosphate, sodium monohydrogen phosphate, potassium alginate, sodium alginate, sodium oleate, potassium acetate, calcium acetate, calcium acetate monohydrate, sodium acetate, sodium acetate trihydrate, magnesium acetate, magnesium acetate tetrahydrate, potassium tartrate, sodium tartrate, sodium tartrate dihydrate, sodium potassium tartrate, potassium hydrogen tartrate, sodium hydrogen tartrate, sodium hydrogen tartrate monohydrate, sodium benzoate, sodium stearate, magnesium stearate, potassium formate, sodium formate, potassium permanganate, and calcium iodate are added.

[0033] 3 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 electric discharge machining unit 12 is machining a workpiece made of an aluminum-based material.

[0034] In step S1, the resistivity value acquiring unit 56 acquires information indicating the resistivity value of the machining fluid from the resistivity value measuring unit 28. Then, the process proceeds to step S2.

[0035] In step S2, the control unit 58 determines whether the resistivity of the machining fluid is equal to or less than a predetermined value based on the information indicating the resistivity acquired by the resistivity acquisition unit 56 in step S1. If it is determined that the resistivity of the machining fluid is equal to or less than the predetermined value, the chemical addition process ends. If it is determined that the resistivity of the machining fluid is higher than the predetermined value, the process proceeds to step S3.

[0036] The predetermined value is set to a value of 30,000 Ωcm or less. The predetermined value is set depending on the chemical to be added to the machining fluid. Setting of the predetermined value will be described in detail later.

[0037] In step S3, the control unit 58 controls the adding unit 26 to add the chemical to the machining fluid, and then the process proceeds to step S4.

[0038] In step S4, the resistivity value acquiring unit 56 acquires information indicating the resistivity value of the machining fluid from the resistivity value measuring unit 28. Thereafter, the process proceeds to step S5.

[0039] In step S5, the control unit 58 determines whether the resistivity of the machining fluid is equal to or less than a predetermined value based on the information indicating the resistivity acquired by the resistivity acquisition unit 56 in step S4. If it is determined that the resistivity of the machining fluid is equal to or less than the predetermined value, the chemical addition process ends. If it is determined that the resistivity of the machining fluid is higher than the predetermined value, the process returns to step S3.

[0040] [Setting of Predetermined Value] When the resistivity of the machining fluid is higher than a predetermined value, the control unit 58 controls the addition unit 26 to add a chemical to the machining fluid. This predetermined value is set depending on the chemical to be added to the machining fluid.

[0041] (When Sodium Bisulfite is Added to Machining Fluid) FIG. 4 is a graph showing the relationship between the resistivity of the machining fluid and the life of the filter 36 when sodium bisulfite is added to the machining fluid as a chemical.

[0042] As shown in Figure 4, the life of the filter 36 is significantly longer when the resistivity is 30,000 [Ωcm] or less than when the resistivity is higher than 30,000 [Ωcm]. Therefore, when sodium bisulfite is used as the chemical, the predetermined value is set to 30,000 [Ωcm]. To further extend the life of the filter 36, when sodium bisulfite is used as the chemical, the predetermined value may be set to a value less than 30,000 [Ωcm]. Furthermore, to further extend the life of the filter 36, when sodium bisulfite is used as the chemical, the predetermined value may be set to a value less than 25,000 [Ωcm].

[0043] (When calcium hydroxide is added to machining fluid) FIG. 5 is a graph showing the relationship between the resistivity of the machining fluid and the life of the filter 36 when calcium hydroxide is added to the machining fluid as a chemical.

[0044] As shown in Figure 5, the life of the filter 36 is significantly longer when the resistivity is 30,000 [Ωcm] or less than when it is higher than 30,000 [Ωcm]. Therefore, when calcium hydroxide is used as the chemical, the predetermined value is set to 30,000 [Ωcm]. To further extend the life of the filter 36, when calcium hydroxide is used as the chemical, the predetermined value may be set to a value less than 30,000 [Ωcm]. Furthermore, to further extend the life of the filter 36, when calcium hydroxide is used as the chemical, the predetermined value may be set to a value less than 20,000 [Ωcm].

[0045] (When Magnesium Sulfate is Added to Machining Fluid) FIG. 6 is a graph showing the relationship between the resistivity of the machining fluid and the life of the filter 36 when magnesium sulfate is added to the machining fluid as a chemical.

[0046] 6, the life of the filter 36 is significantly longer when the resistivity is 23,000 Ωcm or less than when it is higher than 23,000 Ωcm. Therefore, when magnesium sulfate is used as the chemical, the predetermined value is set to 23,000 Ωcm. To further extend the life of the filter 36, when magnesium sulfate is used as the chemical, the predetermined value may be set to a value less than 23,000 Ωcm.

[0047] (When Sodium Hydrogen Sulfate is Added to Machining Fluid) FIG. 7 is a graph showing the relationship between the resistivity of the machining fluid and the life of the filter 36 when sodium hydrogen sulfate is added to the machining fluid as a chemical.

[0048] 7, the life of the filter 36 is significantly longer when the resistivity is 25,000 Ωcm or less than when it is higher than 25,000 Ωcm. Therefore, when sodium bisulfate is used as the chemical, the predetermined value is set to 25,000 Ωcm. To further extend the life of the filter 36, when sodium bisulfate is used as the chemical, the predetermined value may be set to a value less than 25,000 Ωcm. Furthermore, to further extend the life of the filter 36, when sodium bisulfate is used as the chemical, the predetermined value may be set to a value less than 20,000 Ωcm.

[0049] (When potassium disulfite is added to machining fluid) FIG. 8 is a graph showing the relationship between the resistivity of the machining fluid and the life of the filter 36 when potassium disulfite is added to the machining fluid as a chemical.

[0050] 8, the life of the filter 36 is significantly longer when the resistivity is 30,000 Ωcm or less than when it is higher than 30,000 Ωcm. Therefore, when potassium disulfite is used as the chemical, the predetermined value is set to 30,000 Ωcm. To further extend the life of the filter 36, when potassium disulfite is used as the chemical, the predetermined value may be set to a value less than 30,000 Ωcm.

[0051] (When Sodium Bicarbonate is Added to Machining Fluid) FIG. 9 is a graph showing the relationship between the resistivity of the machining fluid and the life of the filter 36 when sodium bicarbonate is added to the machining fluid as a chemical.

[0052] 9, the life of the filter 36 is significantly longer when the resistivity is 30,000 Ωcm or less than when it is higher than 30,000 Ωcm. Therefore, when sodium bicarbonate is used as the drug, the predetermined value is set to 30,000 Ωcm. To further extend the life of the filter 36, the predetermined value may be set to a value less than 30,000 Ωcm when sodium bicarbonate is used as the drug.

[0053] (When Sodium Carbonate is Added to Machining Fluid) FIG. 10 is a graph showing the relationship between the resistivity of the machining fluid and the life of the filter 36 when sodium carbonate is added to the machining fluid as a chemical.

[0054] 10 , the life of the filter 36 is significantly longer when the resistivity is 30,000 Ωcm or less than when it is higher than 30,000 Ωcm. Therefore, when sodium carbonate is used as the chemical, the predetermined value is set to 30,000 Ωcm. To further extend the life of the filter 36, when sodium carbonate is used as the chemical, the predetermined value may be set to a value less than 30,000 Ωcm. Furthermore, to further extend the life of the filter 36, when sodium carbonate is used as the chemical, the predetermined value may be set to a value less than 20,000 Ωcm.

[0055] (When Sodium Sulfate is Added to Machining Fluid) FIG. 11 is a graph showing the relationship between the resistivity of the machining fluid and the life of the filter 36 when sodium sulfate is added to the machining fluid as a chemical.

[0056] 11 , the life of the filter 36 is significantly longer when the resistivity is 30,000 Ωcm or less than when the resistivity is higher than 30,000 Ωcm. Therefore, when sodium sulfate is used as the chemical, the predetermined value is set to 30,000 Ωcm. To further extend the life of the filter 36, when sodium sulfate is used as the chemical, the predetermined value may be set to a value less than 30,000 Ωcm. Furthermore, to further extend the life of the filter 36, when sodium sulfate is used as the chemical, the predetermined value may be set to a value less than 20,000 Ωcm.

[0057] 12 is a schematic diagram of an electric discharge machine 10. The electric discharge machine 10 has an electric discharge machining section 12, a machining fluid treatment section 14, and a control device 16.

[0058] The electric discharge machine 10 of this embodiment differs from the electric discharge machine 10 of the first embodiment in that the addition unit 26 ( FIG. 1 ) of the first embodiment is not provided in the machining fluid treatment unit 14. The electric discharge machine 10 of this embodiment also differs from the electric discharge machine 10 of the first embodiment in that it has a notification unit 60.

[0059] In the first embodiment, the adding unit 26 adds the chemical to the machining fluid. In the present embodiment, the user adds the chemical to the machining fluid. The notifying unit 60 notifies the user and prompts the user to add the chemical to the machining fluid.

[0060] The user may add a chemical to the machining fluid stored in the clean fluid tank 22. The user may add a chemical to the machining fluid stored in the waste fluid tank 20. The user may add a chemical to the machining fluid stored in the machining tank 18.

[0061] The notification unit 60 may be an acoustic device that generates sound, such as a speaker. The notification unit 60 may be a lighting device that turns on or blinks a light, such as a bulb. The notification unit 60 may be a display device that displays still images, moving images, etc., such as a liquid crystal display.

[0062] 13 is a block diagram showing the configuration of the control device 16. The control device 16 has a calculation unit 52 and a storage unit .

[0063] The control device 16 of this embodiment differs from the control device 16 of the first embodiment in that the control unit 58 controls the notification unit 60. The method of controlling the notification unit 60 will be described in detail later.

[0064] 14 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 electric discharge machining unit 12 is machining a workpiece made of an aluminum-based material.

[0065] In step S11, the resistivity value acquiring unit 56 acquires information indicating the resistivity value of the machining fluid from the resistivity value measuring unit 28. Then, the process proceeds to step S12.

[0066] In step S12, the control unit 58 determines whether the resistivity of the machining fluid is equal to or less than a predetermined value based on the information indicating the resistivity acquired by the resistivity acquisition unit 56 in step S11. If it is determined that the resistivity of the machining fluid is equal to or less than the predetermined value, the chemical addition process is terminated. If it is determined that the resistivity of the machining fluid is higher than the predetermined value, the process proceeds to step S13.

[0067] The method for setting the predetermined value for each drug is the same as the method for setting the predetermined value for each drug in the first embodiment.

[0068] In step S13, the control unit 58 controls the notification unit 60 to notify the user, and then the process proceeds to step S14.

[0069] In step S14, the resistivity value acquiring unit 56 acquires information indicating the resistivity value of the machining fluid from the resistivity value measuring unit 28. Thereafter, the process proceeds to step S15.

[0070] In step S15, the control unit 58 determines whether the resistivity of the machining fluid is equal to or less than a predetermined value based on the information indicating the resistivity acquired by the resistivity acquisition unit 56 in step S14. If it is determined that the resistivity of the machining fluid is equal to or less than the predetermined value, the chemical addition process is terminated. If it is determined that the resistivity of the machining fluid is higher than the predetermined value, the process returns to step S13.

[0071] The electric discharge machine 10 and electric discharge machining method of the present disclosure can extend the life of the filter 36 even when electric discharge machining is performed on a workpiece made of an aluminum-based material in machining fluid.

[0072] The following additional notes are further disclosed regarding the above embodiment.

[0073] (Note 1) An electric discharge machine (10) for electric discharge machining of a workpiece, the electric discharge machine comprising: an electric discharge machining section (12) for electric discharge machining of the workpiece in machining fluid; and a filter (36) for removing sludge contained in the machining fluid; and when the workpiece is made of an aluminum-based material, the electric discharge machining is performed using the machining fluid whose resistivity has been reduced to a predetermined value or less by adding an agent, the predetermined value being 30,000 Ω cm or less.

[0074] (Supplementary Note 2) In the electric discharge machine according to Supplementary Note 1, when the agent is sodium hydrogen sulfite, the predetermined value may be a value of 25,000 [Ωcm] or less.

[0075] (Supplementary Note 3) In the electric discharge machine according to Supplementary Note 1, when the agent is calcium hydroxide, the predetermined value may be a value of 20,000 [Ωcm] or less.

[0076] (Supplementary Note 4) In the electric discharge machine according to Supplementary Note 1, when the agent is magnesium sulfate, the predetermined value may be a value of 23,000 [Ωcm] or less.

[0077] (Supplementary Note 5) In the electric discharge machine according to Supplementary Note 1, when the agent is sodium hydrogen sulfate, the predetermined value may be a value of 25,000 [Ωcm] or less.

[0078] (Supplementary Note 6) In the electric discharge machine according to Supplementary Note 1, when the agent is sodium hydrogen sulfate, the predetermined value may be a value of 20,000 [Ωcm] or less.

[0079] (Supplementary Note 7) In the electric discharge machine according to Supplementary Note 1, when the agent is sodium carbonate, the predetermined value may be a value of 20,000 [Ωcm] or less.

[0080] (Supplementary Note 8) In the electric discharge machine according to Supplementary Note 1, when the agent is sodium sulfate, the predetermined value may be a value of 20,000 [Ωcm] or less.

[0081] (Appendix 9) The electric discharge machine described in any one of Appendices 1 to 8 may further include a resistivity value acquisition unit (56) that acquires information indicating the resistivity value of the machining fluid, and a control unit (58) that performs control to add the agent to the machining fluid when the resistivity value of the machining fluid is higher than the predetermined value.

[0082] (Supplementary Note 10) An electric discharge machining method using an electric discharge machine equipped with an electric discharge machining unit that performs electric discharge machining on a workpiece in machining fluid and a filter that removes sludge contained in the machining fluid, the electric discharge machining method comprising: a resistivity value acquisition step of acquiring information indicating a resistivity value of the machining fluid; an addition step of adding a chemical to the machining fluid to make the resistivity value of the machining fluid equal to or less than the predetermined value when the workpiece is made of an aluminum-based material and the resistivity value of the machining fluid is higher than a predetermined value; and an electric discharge machining step of performing the electric discharge machining on the workpiece made of the aluminum-based material in the machining fluid whose resistivity has been made equal to or less than the predetermined value, wherein the predetermined value is equal to or less than 30,000 Ωcm.

[0083] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0084] REFERENCE SIGNS LIST 10... Electric discharge machine 12... Electric discharge machining unit 36... Filter 56... Resistivity value acquisition unit 58... Control unit

Claims

1. A wire electrical discharge machining apparatus for performing electrical discharge machining on a workpiece, comprising: an electrical discharge machining unit that performs electrical discharge machining on the workpiece in a machining fluid; and a filter that removes sludge contained in the machining fluid. When the workpiece is made of an aluminum-based material, the electrical discharge machining is performed using the machining fluid whose specific resistance value has become a predetermined value or less by adding a chemical agent. The predetermined value is a value of 30,000 [Ωcm] or less.

2. The wire electrical discharge machining apparatus according to claim 1, wherein when the chemical agent is sodium bisulfite, the predetermined value is a value of 25,000 [Ωcm] or less.

3. The wire electrical discharge machining apparatus according to claim 1, wherein when the chemical agent is calcium hydroxide, the predetermined value is a value of 20,000 [Ωcm] or less.

4. The wire electrical discharge machining apparatus according to claim 1, wherein when the chemical agent is magnesium sulfate, the predetermined value is a value of 23,000 [Ωcm] or less.

5. The wire electrical discharge machining apparatus according to claim 1, wherein when the chemical agent is sodium bisulfite, the predetermined value is a value of 25,000 [Ωcm] or less.

6. The wire electrical discharge machining apparatus according to claim 1, wherein when the chemical agent is sodium bisulfite, the predetermined value is a value of 20,000 [Ωcm] or less.

7. The wire electrical discharge machining apparatus according to claim 1, wherein when the chemical agent is sodium carbonate, the predetermined value is a value of 20,000 [Ωcm] or less.

8. The wire electrical discharge machining apparatus according to claim 1, wherein when the chemical agent is sodium sulfate, the predetermined value is a value of 20,000 [Ωcm] or less.

9. The wire electrical discharge machining apparatus according to any one of claims 1 to 8, further comprising: a specific resistance value acquisition unit that acquires information indicating the specific resistance value of the machining fluid; and a control unit that performs control to add the chemical agent to the machining fluid when the specific resistance value of the machining fluid is higher than the predetermined value.

10. A wire electrical discharge machining method using a wire electrical discharge machine including a wire electrical discharge machining unit that performs wire electrical discharge machining on a workpiece in a machining fluid and a filter that removes sludge contained in the machining fluid, the method comprising: a specific resistance value acquisition step of acquiring information indicating a specific resistance value of the machining fluid; an addition step of adding a chemical to the machining fluid to make the specific resistance value of the machining fluid equal to or less than a predetermined value when the workpiece is made of an aluminum-based material and the specific resistance value of the machining fluid is higher than the predetermined value; and a wire electrical discharge machining step of performing the wire electrical discharge machining on the workpiece made of the aluminum-based material in the machining fluid having the specific resistance value equal to or less than the predetermined value, wherein the predetermined value is a value of 30,000 [Ωcm] or less.

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