Control device and electrical discharge machine

Abstract

An embodiment of the present disclosure is a control device for controlling an electrical discharge machine comprising an electrical discharge machining unit that performs electrical discharge machining on a workpiece in a machining liquid, and a filter that removes sludge contained in the machining liquid, the control device comprising: an acquisition unit that acquires information pertaining to the amount of sludge mixed in the machining liquid; and an addition control unit that, if the workpiece is made of an aluminum-based material, performs, on the basis of the information pertaining to the amount of sludge, control for adding, to the machining liquid, a chemical agent for inhibiting generation of aluminum hydroxide.

Description

Control device and electric discharge machine

[0001] The present disclosure relates to a control device and an electric discharge machine.

[0002] Japanese Patent Application Laid-Open No. 2016-43422 discloses a machining fluid supply device for an electric discharge machine, in which machining fluid containing sludge (machining debris) is filtered through a filter before being supplied to a machining tank.

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

[0004] A first aspect of the present disclosure is a control device for controlling an electric discharge machine having an electric 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, and the control device includes an acquisition unit that acquires information regarding the amount of sludge mixed in the machining fluid, and an addition control unit that, when the workpiece is made of an aluminum-based material, controls the addition of an agent to the machining fluid to suppress the generation of aluminum hydroxide based on the information regarding the amount of sludge.

[0005] A second aspect of the present disclosure is an electric discharge machine comprising the control device of the first aspect, a container for storing the chemical agent, and an actuator that operates in response to a signal output from the control device and can adjust the amount of the chemical agent added from the container to the machining fluid.

[0006] Fig. 1 is a schematic diagram of an electric discharge machine. Fig. 2 is a schematic diagram of a chemical dosing device according to a first embodiment. Fig. 3 is a schematic diagram of a chemical dosing device according to a second embodiment. Fig. 4 is a functional block diagram of a control device. Fig. 5 is a flowchart of a chemical dosing process. Fig. 6 is a flowchart of a notification process.

[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 filter filters the machining fluid, 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 filter life 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 has a relatively high viscosity, and it is thought that adhesion of the aluminum hydroxide to the filter shortens the filter life. The filter life when electric discharge machining is performed on a workpiece made of an aluminum-based material is 10% to 25% of the filter life when electric discharge machining is performed on a workpiece made of an iron-based material.

[0010] The life of the filter can be extended by adding a chemical to the machining fluid to suppress the generation of aluminum hydroxide. The chemical reacts with the sludge generated by electrical discharge machining, reducing the chemical concentration. The technology disclosed herein aims to provide a control device and an electrical discharge machine that can appropriately add the chemical.

[0011] 1 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 processing section 14, a control device 16, and an alarm device 18. The electric discharge machine 10 is a wire electric discharge machine.

[0012] The electric discharge machining unit 12 has a machining tank 20. The electric discharge machining unit 12 performs electric discharge machining on a workpiece in a machining fluid stored in the machining tank 20.

[0013] The machining fluid treatment section 14 has a waste fluid tank 22, a clean fluid tank 24, a chemical addition section 26, and an ion exchange resin 28. The machining fluid treatment section 14 also has a drainage path 30, a filtration path 32, a circulation path 34, and a supply path 36. The machining fluid treatment section 14 also has a first pump 38, a filter 40, a second pump 42, a first valve 44, and a third pump 46.

[0014] The machining fluid used in the electric discharge machining is discharged from the machining tank 20 through the drainage path 30 into the waste fluid tank 22. The machining fluid discharged from the machining tank 20 contains sludge generated during the electric discharge machining.

[0015] The machining fluid stored in the waste fluid tank 22 is sent to the clean fluid tank 24 through a filtration path 32. A first pump 38 and a filter 40 are provided on the filtration path 32. The first pump 38 sends the machining fluid from the waste fluid tank 22 to the clean fluid tank 24. The filter 40 filters the machining fluid sent from the waste fluid tank 22 to the clean fluid tank 24 and removes sludge from the machining fluid.

[0016] The machining fluid stored in the clean fluid tank 24 circulates between the clean fluid tank 24 and the ion exchange resin 28 through a circulation path 34. A second pump 42 and a first valve 44 are provided in the circulation path 34. The second pump 42 supplies the machining fluid in the clean fluid tank 24 to the ion exchange resin 28.

[0017] The ion exchange resin 28 captures specific ions contained in the machining fluid passing through the ion exchange resin 28 and releases other ions.

[0018] The machining fluid stored in the clean fluid tank 24 is sent to the machining tank 20 through a supply path 36. A third pump 46 is provided in the supply path 36. The third pump 46 sends the machining fluid from the clean fluid tank 24 to the machining tank 20.

[0019] The chemical adding section 26 adds a chemical that inhibits the formation of aluminum hydroxide to the machining fluid in the waste fluid tank 22. Examples of chemicals that can be added to the machining fluid include sodium hydrogen sulfite, sodium carbonate, sodium sulfate, calcium hydroxide, sodium disulfite (sodium pyrosulfite), potassium disulfite (potassium pyrosulfite), magnesium sulfate, magnesium sulfate heptahydrate, etc. Adding such chemicals to the machining fluid can inhibit sludge in the machining fluid from converting into aluminum hydroxide.

[0020] By adding the chemical to the machining fluid, the machining fluid contains at least one of the following cations: potassium ion, calcium ion, sodium ion, and magnesium ion. Furthermore, by adding the chemical to the machining fluid, the machining fluid contains at least one of the following anions: sulfate ion, sulfite ion, disulfite ion, bisulfite ion, hydroxide ion, nitrate ion, and nitrite ion.

[0021] 2 is a schematic diagram of a chemical supplying device 48 according to the first embodiment. The chemical supplying device 48 according to the first embodiment includes a control device 16, an alarm device 18, and a chemical supplying unit 26.

[0022] The chemical addition unit 26 according to the first embodiment includes a chemical solution tank (container) 50, an addition path 52, a second valve 54, a solenoid (actuator) 56, and a liquid level sensor 58. The chemical addition device 48 according to the first embodiment uses a solution containing a chemical. A solution containing a chemical is called a chemical solution. However, instead of a chemical solution, a powdered chemical or a solid chemical may be used.

[0023] The chemical solution is stored in the chemical solution tank 50. The chemical solution tank 50 is disposed above the waste liquid tank 22. The chemical solution tank 50 is connected to the waste liquid tank 22 via an addition path 52. A second valve 54 is provided in the addition path 52. The second valve 54 is, for example, a solenoid valve or an electric valve. When the second valve 54 is a solenoid valve, the second valve 54 opens and closes in response to the supply and cut-off of current to a solenoid 56. When the second valve 54 opens, the chemical solution stored in the chemical solution tank 50 falls through the addition path 52 toward the waste liquid tank 22. In this way, the chemical is added to the machining fluid.

[0024] The liquid level sensor 58 detects the liquid level of the liquid medicine in the liquid medicine tank 50. The liquid level sensor 58 outputs a signal indicating the detected value of the liquid level to the control device 16. The detected value of the liquid level sensor 58 is used to calculate the remaining amount of the medicine.

[0025] Figure 3 is a schematic diagram of a chemical addition device 48 according to the second embodiment. The chemical addition device 48 according to the second embodiment has a control device 16, an alarm device 18, and a chemical addition section 26. In the chemical addition device 48 shown in Figure 3, the same components as those in the chemical addition device 48 shown in Figure 2 are denoted by the same reference numerals. Regarding the chemical addition device 48 according to the second embodiment, the differences from the chemical addition device 48 according to the first embodiment will be described.

[0026] Similar to the drug addition unit 26 according to the first embodiment, the drug addition unit 26 according to the second embodiment has an addition path 52, a second valve 54, and a solenoid 56. The drug addition unit 26 according to the second embodiment further has a cylinder (container) 60, a piston rod 62, and a piston moving mechanism 64.

[0027] The chemical liquid is stored in a liquid chamber 60r of the cylinder 60. The liquid chamber 60r of the cylinder 60 is defined by the inner wall of the cylinder 60 and the end face of the piston rod 62. A discharge port 60d is formed in the liquid chamber 60r. The discharge port 60d is connected to the waste liquid tank 22 via the addition path 52. The piston rod 62 is slidable inside the cylinder 60. When the piston rod 62 moves toward the first end of the cylinder 60, the liquid chamber 60r is narrowed and the chemical liquid in the liquid chamber 60r is pressurized. Then, the chemical liquid in the liquid chamber 60r flows out from the discharge port 60d into the addition path 52. The piston rod 62 moves by the operation of the piston moving mechanism 64.

[0028] The piston moving mechanism 64 has a nut portion 66, a screw portion 68, a pair of bearings 70, a motor (actuator) 72, and a rotation sensor 74. The nut portion 66 and the screw portion 68 form a ball screw. The nut portion 66 is connected to the piston rod 62. The screw portion 68 is journaled by the pair of bearings 70. One end of the screw portion 68 is connected to the rotation shaft of the motor 72. The piston moving mechanism 64 converts the rotational motion of the motor 72 into linear motion of the piston rod 62. That is, when the motor 72 rotates in one direction, the piston rod 62 moves linearly in a first direction, and when the motor 72 rotates in the other direction, the piston rod 62 moves linearly in a second direction.

[0029] The rotation sensor 74 detects the number of rotations or the rotation angle of the motor 72. The rotation sensor 74 outputs a signal indicating the detected value of the number of rotations or the rotation angle to the control device 16. The detected value of the rotation sensor 74 is used to calculate the remaining amount of the medicine.

[0030] The piston moving mechanism 64 may have another mechanism that converts the rotational motion of the motor 72 into linear motion of the piston rod 62. For example, the piston moving mechanism 64 may have a rack and pinion.

[0031] FIG. 4 is a functional block diagram of the control device 16. The control device 16 has a calculation unit 76 and a memory unit 78. The calculation unit 76 is a processor such as a central processing unit (CPU) or a graphics processing unit (GPU). The calculation unit 76 includes a processing control unit 80, a distribution control unit 82, an addition control unit 84, a notification control unit 86, an acquisition unit 88, and a clock unit 90. The processing control unit 80, the distribution control unit 82, the addition control unit 84, the notification control unit 86, the acquisition unit 88, and the clock unit 90 are realized by executing a program stored in the memory unit 78 in the calculation unit 76. At least a portion of the processing control unit 80, the distribution control unit 82, the addition control unit 84, the notification control unit 86, the acquisition unit 88, and the clock unit 90 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 processing control unit 80, the distribution control unit 82, the addition control unit 84, the notification control unit 86, the acquisition unit 88, and the timing unit 90 may be realized by an electronic circuit including a discrete device.

[0032] The storage unit 78 is configured by 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), a flash memory, etc. Data, etc., are stored in the volatile memory. Programs, tables, maps, etc., are stored in the non-volatile memory, for example. At least a portion of the storage unit 78 may be provided in the processor, integrated circuit, etc. described above. At least a portion of the storage unit 78 may be mounted on a device connected to the electric discharge machine 10 via a network. The storage unit 78 stores a machining program 92.

[0033] The machining control unit 80 controls the electric discharge machining in the electric discharge machining unit 12. The circulation control unit 82 controls the circulation of the machining fluid in the machining fluid treatment unit 14. The addition control unit 84 controls the addition of chemicals to the machining fluid. The notification control unit 86 controls notifications to the user. The acquisition unit 88 acquires information regarding the amount of sludge mixed in the machining fluid. The timing unit 90 measures the elapsed time from the timing of the start of discharge or the timing of the addition of chemicals to the machining fluid.

[0034] 1, the description of the electric discharge machine 10 will continue. The notification device 18 notifies the user in accordance with a notification signal output from the control device 16. The notification device 18 includes, for example, a display, a speaker, and the like.

[0035] [Chemical Addition Process] Figure 5 is a flowchart of the chemical addition process. The chemical addition process is executed when a workpiece made of an aluminum-based material is machined. When a user performs an operation to start electrical discharge machining, the machining control unit 80 starts electrical discharge machining by the electrical discharge machine 10 in accordance with the machining program 92 stored in the memory unit 78. The circulation control unit 82 circulates the machining fluid in the machining fluid treatment unit 14 during electrical discharge machining. Specifically, the circulation control unit 82 controls the operation of the first pump 38, the second pump 42, the first valve 44, and the third pump 46. Furthermore, the control device 16 executes the chemical addition process, which will be described below, during electrical discharge machining.

[0036] In step S1, the timer 90 starts timing. The timer 90 measures the elapsed time from the timing of the start of discharge or the timing of adding the chemical to the machining fluid. Hereinafter, this elapsed time will be referred to as the measured time.

[0037] In step S2, the machining control unit 80 determines whether or not the electric discharge machining is to be continued. If the machining of the workpiece has not finished, the machining control unit 80 determines that the electric discharge machining is to be continued. If the electric discharge machining is to be continued (step S2: YES), the process proceeds to step S3. On the other hand, if the electric discharge machining is to be finished (step S2: NO), the chemical addition process shown in FIG. 5 ends.

[0038] When the process proceeds from step S2 to step S3, the addition control unit 84 determines whether the time measured by the timer unit 90 is equal to or greater than a predetermined time. The predetermined time is pre-stored in the memory unit 78. If the measured time is equal to or greater than the predetermined time (step S3: YES), the process proceeds to step S4. In this case, in the processes from step S4 onwards, the chemical agent is added to the machining liquid. On the other hand, if the measured time is less than the predetermined time (step S3: NO), the process returns to step S2.

[0039] When moving from step S3 to step S4, the acquisition unit 88 acquires information regarding the amount of sludge mixed in the machining fluid. The amount of aluminum hydroxide generated increases as the amount of sludge increases. The sludge increases as the machining of the workpiece progresses. Therefore, the acquisition unit 88 acquires the machining amount of the workpiece as information regarding the amount of sludge. The acquisition unit 88 calculates the machining amount of the workpiece from the time of the previous chemical addition (or the start of machining) to the present based on the progress of the electric discharge machining and the machining program 92. For example, the acquisition unit 88 can calculate the machining amount of the workpiece by multiplying the machining speed by the electric discharge machining unit 12, the thickness of the workpiece, and the groove width of the machined groove, etc. The acquisition unit 88 may also acquire the machining time as information regarding the amount of sludge.

[0040] In step S5, the addition control unit 84 determines the amount of chemical that needs to be added to the machining fluid. For example, the addition control unit 84 determines the amount of chemical that needs to be added to the machining fluid based on the information about the amount of sludge (the amount of workpiece processed, the machining time of the workpiece) acquired in step S4. Information showing the relationship between the information about the amount of sludge and the amount of chemical that needs to be added is stored in advance in the storage unit 78. For example, the greater the amount of workpiece processed (or the longer the machining time of the workpiece), the greater the amount of sludge generated and the greater the amount of chemical that needs to be added.

[0041] In step S6, the addition control unit 84 performs control (addition control) to add the chemical to the machining fluid. The addition control unit 84 calculates the injection amount of the chemical based on the amount of chemical to be added determined in step S5. The addition control unit 84 controls the actuator (solenoid 56, motor 72, etc.) of the chemical addition unit 26 so that the calculated injection amount of the chemical is injected from the chemical addition unit 26 into the machining fluid. The addition control unit 84 stops the injection of the chemical after the calculated injection amount of the chemical has been injected from the chemical addition unit 26 into the machining fluid.

[0042] In step S7, the timer unit 90 resets the measured time. When step S7 ends, the process returns to step S1.

[0043] [Notification Process] Fig. 6 is a flowchart of the notification process. The control device 16 executes the notification process shown in Fig. 6 during electric discharge machining. The notification process is performed in parallel with the chemical doping process shown in Fig. 5.

[0044] In step S11, the notification control unit 86 determines whether the remaining amount of medicine is equal to or less than a predetermined amount. The notification control unit 86 estimates the remaining amount of medicine based on the detection value of the liquid level sensor 58 shown in Fig. 2 or the detection value of the rotation sensor 74 shown in Fig. 3. If the remaining amount of medicine is equal to or less than the predetermined amount (step S11: YES), the process proceeds to step S12. On the other hand, if the remaining amount of medicine is greater than the predetermined amount (step S11: NO), the process proceeds to step S13.

[0045] When the process proceeds from step S11 to step S12, the notification control unit 86 performs notification control. The notification control unit 86 outputs a notification signal indicating a notification instruction to the notification device 18. The notification device 18 displays a warning or emits a warning sound in accordance with the notification instruction.

[0046] In step S13, the machining control unit 80 determines whether or not the electric discharge machining is to be continued. If the electric discharge machining is to be continued (step S13: YES), the process returns to step S11. On the other hand, if the electric discharge machining is to be ended (step S13: NO), the notification process shown in FIG. 6 is ended.

[0047] [Modifications] In the above description, the chemical adding unit 26 injects a solution containing a chemical (chemical solution) into the machining fluid, but a powder or solid chemical may be added directly to the machining fluid.

[0048] In the above description, the chemical addition section 26 injects chemical liquid into the machining fluid stored in the waste fluid tank 22, but the chemical liquid may also be injected into the machining fluid in other locations within the machining fluid treatment section 14 (such as the machining tank 20 or the clean fluid tank 24).

[0049] In the above description, the addition control unit 84 may add a predetermined amount of chemical to the machining fluid at the start of electric discharge machining, thereby making it possible to suppress the generation of aluminum hydroxide immediately after the start of electric discharge machining.

[0050] [Effects of the above disclosure] In the above disclosure, the control device 16 controls the chemical additive unit 26 to add an appropriate amount of chemical to the machining fluid to suppress the generation of aluminum hydroxide. This makes it difficult for highly viscous aluminum hydroxide to be generated in the machining fluid, thereby preventing adhesion of aluminum hydroxide to the filter 40. As a result, the life of the filter 40 can be extended.

[0051] According to the above disclosure, the control device 16 controls the addition of chemicals to the machining fluid based on information about the amount of sludge, so that an appropriate amount of chemicals can be added to the machining fluid. This prevents the chemicals from being used more than necessary, thereby reducing chemical consumption. In other words, the above disclosure provides a control device 16 and an electric discharge machine 10 that can appropriately add chemicals.

[0052] [Supplementary Note] The following supplementary note is further disclosed regarding the above embodiment and modified examples.

[0053] (Supplementary Note 1) An aspect of the present disclosure is a control device (16) for controlling an electric discharge machine (10) including an electric discharge machining unit (12) that performs electric discharge machining on a workpiece in machining fluid and a filter (40) that removes sludge contained in the machining fluid, the control device (16) including an acquisition unit (88) that acquires information regarding the amount of sludge mixed in the machining fluid, and an addition control unit (84) that, when the workpiece is made of an aluminum-based material, performs control to add an agent to the machining fluid to suppress the generation of aluminum hydroxide based on the information regarding the amount of sludge.

[0054] (Supplementary Note 2) In the control device described in Supplementary Note 1, the agent may include one or more cations selected from the group consisting of potassium ions, calcium ions, sodium ions, and magnesium ions, and one or more anions selected from the group consisting of sulfate ions, sulfite ions, disulfite ions, bisulfite ions, hydroxide ions, nitrate ions, and nitrite ions.

[0055] (Supplementary Note 3) An aspect of the present disclosure is an electric discharge machine (10) comprising: a control device according to Supplementary Note 1 or 2; a container (50, 60) for storing the chemical; and an actuator (56, 72) that operates in response to a signal output from the control device and can adjust the amount of the chemical added from the container to the machining fluid.

[0056] (Supplementary Note 4) In the electric discharge machine described in Supplementary Note 3, the control device may include a notification control unit (86) that performs notification control when the remaining amount of the agent in the container becomes equal to or less than a predetermined amount.

[0057] 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.

[0058] REFERENCE SIGNS LIST 10... Electric discharge machine 12... Electric discharge machining section 16... Control device 40... Filter 50... Chemical solution tank (container) 56... Solenoid (actuator) 60... Cylinder (container) 72... Motor (actuator) 84... Addition control section 86... Notification control section 88... Acquisition section

Claims

1. A control device for controlling an electric discharge machining machine having an electric 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, the control device comprising: an acquisition unit that acquires information regarding the amount of sludge mixed into the machining fluid; and an addition control unit that, when the workpiece is made of an aluminum-based material, controls the addition of an agent for suppressing the generation of aluminum hydroxide to the machining fluid based on the information regarding the amount of sludge.

2. A control device according to claim 1, wherein the chemical agent comprises one or more cations selected from the group consisting of potassium ions, calcium ions, sodium ions and magnesium ions, and one or more anions selected from the group consisting of sulfate ions, sulfite ions, disulfite ions, hydrogen sulfite ions, hydroxide ions, nitrate ions and nitrite ions.

3. An electric discharge machine comprising: a control device according to claim 1 or 2; a container for storing the chemical; and an actuator that operates in response to a signal output from the control device and can adjust the amount of the chemical added from the container to the machining fluid.

4. An electric discharge machine according to claim 3, wherein the control device is provided with an alarm control section which performs alarm control when the remaining amount of the drug in the container falls below a predetermined amount.

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