Electrical discharge machine

Abstract

An electrical discharge machine (10) comprises a dirty water tank (14), a fresh water tank (16), a first pipeline (20), and a sludge filter (26). The sludge filter (26) is a porous material having pores through which fresh water passes, the fresh water being pumped up from the fresh water tank (16) and supplied from the first pipeline (20), which guides the fresh water. Machining waste is captured in the pores of the porous material.

Description

electrical discharge machine

[0001] The present invention relates to an electric discharge machine.

[0002] Electrical discharge machines use electrical discharges to machine a workpiece placed in a machining fluid. This machining process generates ions from the metal in the workpiece and other materials in the machining fluid. Ion exchange resins are generally used to reduce the concentration of metal ions in the machining fluid.

[0003] Japanese Patent Application Laid-Open No. 2013-132735 discloses that the resistivity of the machining fluid is maintained higher than a predetermined value using an ion exchange resin, thereby reducing the ion concentration in the machining fluid.

[0004] However, ion exchange resins have a limited lifespan and need to be replaced approximately every 300 hours. If the ion exchange resin is not replaced, machining accuracy becomes unstable, which tends to increase the running costs required to maintain machining accuracy. Therefore, efficiently improving the resistivity of machining fluids has been an issue.

[0005] The present invention aims to solve the above-mentioned problems.

[0006] One aspect of the present invention is an electric discharge machine that uses electric discharges to machine a workpiece placed in a machining fluid, and includes a wastewater tank that stores wastewater, which is the machining fluid containing machining chips generated by machining the workpiece, a freshwater tank that stores freshwater, which is the machining fluid from which the machining chips have been removed from the wastewater, a first pipeline that guides the freshwater pumped up from the freshwater tank, and a sludge filter that is a porous body having pores through which the freshwater supplied from the first pipeline passes, and in which the machining chips are captured in the pores.

[0007] According to the above-described embodiment, the resistivity of the clean water can be increased by intentionally passing the clean water from which the machining debris has been removed through the pores in which the machining debris has been trapped. Therefore, the resistivity of the clean water can be improved without using a commonly used ion exchange resin. As a result, the resistivity of the machining fluid can be efficiently improved.

[0008] The reciprocal of the resistivity value [Ωm] is the conductivity [S / m], and there is a correlation between the resistivity value [Ωm] and the conductivity [S / m]. Therefore, the resistivity value [Ωm] can be replaced with the conductivity [S / m]. When the resistivity value [Ωm] is replaced with the conductivity [S / m], the magnitude relationship between the values ​​is reversed. For example, "increasing the resistivity value [Ωm]" is synonymous with "decreasing the conductivity [S / m]."

[0009] Fig. 1 is a schematic diagram showing the configuration of an electric discharge machine according to an embodiment. Fig. 2 is a schematic diagram showing the configuration of an electric discharge machine according to a first modified example. Fig. 3 is a schematic diagram showing the configuration of an electric discharge machine according to a second modified example. Fig. 4 is a schematic diagram showing the configuration of an electric discharge machine according to a third modified example.

[0010] [Embodiment] Fig. 1 is a schematic diagram showing the configuration of an electric discharge machine 10 according to an embodiment. The electric discharge machine 10 uses electric discharge to machine a workpiece placed in a machining fluid. The electric discharge machine 10 may be a wire electric discharge machine or a die-sinker electric discharge machine. A wire electric discharge machine generates electric discharge between electrodes between a wire electrode and the workpiece. A die-sinker electric discharge machine generates electric discharge between electrodes between a die-sinker electrode and the workpiece.

[0011] The machining fluid is a liquid used to machine the workpiece. The machining fluid may be water. The workpiece is a metal such as an iron-based material, a superhard material, an aluminum-based material, a copper alloy-based material, a nickel-based material, or a titanium-based material. The electrode (wire electrode or die-sinking electrode) of the electric discharge machine 10 is a metal such as tungsten-based, copper alloy-based, brass-based, titanium-based, zinc-coated brass-based, or an iron-based, molybdenum-based, or carbon-based material used as a core material for brass-based materials. Note that carbon-based materials are used only when the electric discharge machine 10 is a die-sinking electric discharge machine.

[0012] The electric discharge machine 10 has a wastewater tank 14, a clean water tank 16, a first pump 18, a first pipeline 20, a second pump 22, a second pipeline 24, a sludge filter 26, an on-off valve 28, a resistivity meter 30, and a control device 32.

[0013] The wastewater tank 14 is a water tank that stores wastewater. The wastewater is a machining fluid that contains machining debris generated during the machining of the workpiece. The clean water tank 16 is a water tank that stores clean water. The clean water is a machining fluid obtained by removing the machining debris from the wastewater. The machining debris contains at least one of iron, aluminum, copper, zinc, cemented carbide, tungsten, molybdenum, carbon, titanium, silicon, manganese, chromium, phosphorus, sulfur, and nickel.

[0014] The first pump 18 pumps up the fresh water from the fresh water tank 16 and applies a flow force to the fresh water. The first pump 18 is provided in a first pipeline 20. The first pipeline 20 guides the fresh water pumped up from the fresh water tank 16. In this embodiment, the first pipeline 20 guides the fresh water to a sludge filter 26.

[0015] The second pump 22 pumps up wastewater from the wastewater tank 14 and imparts flow force to the wastewater. The second pump 22 is provided in the second pipeline 24. In this embodiment, the second pump 22 is provided in the second pipeline 24 between the wastewater tank 14 and the sludge filter 26. The second pipeline 24 guides the machining fluid from the wastewater tank 14 to the clean water tank 16. The second pipeline 24 has an upstream section 24-1 and a downstream section 24-2. The upstream section 24-1 guides the wastewater pumped up from the wastewater tank 14 to the sludge filter 26. The downstream section 24-2 guides the clean water flowing out from the sludge filter 26 to the clean water tank 16.

[0016] The sludge filter 26 is a porous body having pores. The pores capture processing debris generated during processing of the workpiece. The sludge filter 26 may be a porous body that has been used in the past to remove processing debris. Examples of porous bodies include filter paper and filter cloth. The sludge filter 26 is housed in a filter container 34. The sludge filter 26 housed in the filter container 34 may be joined to the filter container 34.

[0017] The filter container 34 has a first fluid inlet 34-1, a second fluid inlet 34-2, and a fluid outlet 34-3. The first fluid inlet 34-1, the second fluid inlet 34-2, and the fluid outlet 34-3 communicate with a filter accommodating space inside the filter container 34. The filter accommodating space is a space in which the sludge filter 26 is accommodated.

[0018] The first fluid inlet 34-1 and the second fluid inlet 34-2 are disposed, for example, on the upper wall of the filter container 34. The first fluid inlet 34-1 and the second fluid inlet 34-2 may be disposed on a side wall of the filter container 34. The fluid outlet 34-3 is disposed, for example, on the lower wall of the filter container 34. The fluid outlet 34-3 may be disposed on the side wall of the filter container 34. The first fluid inlet 34-1 is connected to an end (downstream end) of the first pipe 20. The second fluid inlet 34-2 is connected to an end (downstream end) of the upstream section 24-1 of the second pipe 24. The fluid outlet 34-3 is connected to an end (upstream end) of the downstream section 24-2 of the second pipe 24. When the machining fluid is allowed to flow into the clean water tank 16 by free fall from the fluid outlet 34-3, the downstream section 24-2 of the second pipe 24 may be removed.

[0019] Either wastewater or fresh water is selectively supplied to the sludge filter 26. Wastewater is supplied from the wastewater tank 14 via the second pipeline 24 and the second fluid inlet 34-2 in this order. Fresh water is supplied from the freshwater tank 16 via the first pipeline 20 and the first fluid inlet 34-1 in this order.

[0020] When wastewater is supplied to the sludge filter 26, the sludge filter 26 removes machining debris contained in the wastewater. In this case, the machining debris is captured in the pores of the sludge filter 26. The machining fluid (clean water) from which the machining debris has been removed by the sludge filter 26 is supplied to the clean water tank 16 from the fluid outlet 34-3.

[0021] On the other hand, when fresh water is supplied to the sludge filter 26, the sludge filter 26 makes the resistivity of the fresh water greater than the resistivity of the fresh water stored in the fresh water tank 16. In this case, the sludge filter 26 increases the resistivity of the fresh water by passing the fresh water through the pores in which the machining waste is captured.

[0022] The on-off valve 28 is provided in the first pipeline 20. The on-off valve 28 is configured to be able to switch between opening and closing the first pipeline 20. When the on-off valve 28 is open, the first pipeline 20 is opened. When the on-off valve 28 is closed, the first pipeline 20 is closed. The on-off valve 28 is opened and closed by a control device 32.

[0023] The resistivity meter 30 is provided in the fresh water tank 16. The resistivity meter 30 measures the resistivity value of the fresh water stored in the fresh water tank 16, and outputs a signal indicating the resistivity value to the control device 32.

[0024] The control device 32 controls the first pump 18, the second pump 22, and the on-off valve 28. The control device 32 has a processor such as a CPU or an MPU, and one or more memories such as a ROM, a RAM, or a hard disk. The control device 32 may be a numerical control device for the electric discharge machine 10. The control device 32 may be another control device provided separately from the numerical control device for the electric discharge machine 10. The other control device has a processor separate from the processor included in the numerical control device.

[0025] A filtering start command or a filtering end command is given to the control device 32. The filtering start command and the filtering end command are given in response to a user's operation from, for example, an input device connected to the control device 32. The input device may be a touch panel, a keyboard and mouse, or an operation panel.

[0026] When the control device 32 receives the filtration start command, it drives the second pump 22 to supply the wastewater stored in the wastewater tank 14 to the sludge filter 26. In this case, the control device 32 does not drive the first pump 18. The control device 32 also closes the on-off valve 28 to prevent wastewater from flowing into the clean water tank 16.

[0027] When the control device 32 receives the filtration end command, it stops the second pump 22 and stops the supply of wastewater to the sludge filter 26. In this case, the control device 32 compares the resistivity value measured by the resistivity meter 30 with a predetermined threshold value.

[0028] If the resistivity value is equal to or lower than a predetermined threshold, the control device 32 supplies the fresh water stored in the fresh water tank 16 to the sludge filter 26. In this case, the control device 32 drives the first pump 18 and opens the on-off valve 28 to pass the fresh water through the pores of the sludge filter 26 in which the machining debris is captured. As a result, the resistivity value of the fresh water becomes higher than the resistivity value of the fresh water stored in the fresh water tank 16. On the other hand, if the resistivity value exceeds the predetermined threshold, the control device 32 stops the first pump 18 and closes the on-off valve 28.

[0029] The inventors discovered that passing clean water through the pores of a porous body in which machining debris is trapped increases the resistivity of the clean water. In this embodiment, a sludge filter 26 is provided. The sludge filter 26 is a porous body having pores through which clean water supplied from the first pipeline 20 passes. These pores trap machining debris generated during machining of the workpiece. By intentionally passing clean water from which machining debris has been removed through the pores in which the machining debris is trapped, the resistivity of the clean water can be increased. Therefore, the resistivity of the clean water can be improved without using a commonly used ion exchange resin. As a result, the resistivity of the machining fluid can be efficiently improved.

[0030] Furthermore, in this embodiment, the sludge filter 26 is provided in the second pipe 24 that guides the machining fluid from the wastewater tank 14 to the fresh water tank 16, and the first pipe 20 guides the fresh water to the sludge filter 26. This allows the sludge filter 26, which increases the resistivity of the fresh water, to also function as a filtration filter. As a result, the resistivity of the machining fluid can be efficiently improved.

[0031] [Modifications] The above embodiment may be modified as follows.

[0032] (Modification 1) Fig. 2 is a schematic diagram showing the configuration of the electric discharge machine 10 according to Modification 1. In Fig. 2, the same components as those described in the embodiment are denoted by the same reference numerals. Note that in this modification, explanations that overlap with the embodiment will be omitted.

[0033] In this modification, a filtration filter 36 is newly provided in addition to the sludge filter 26. The filtration filter 36 is housed in a filter container 38. The filter container 38 has a fluid inlet 38-1 and a fluid outlet 38-2. The fluid inlet 38-1 is connected to an end (downstream end) of the upstream section 24-1 of the second pipeline 24. The fluid outlet 38-2 is connected to an end (upstream end) of the downstream section 24-2 of the second pipeline 24.

[0034] The filtration filter 36 is a porous body having pores. The filtration filter 36 removes processing debris contained in the wastewater. When the filtration filter 36 is used even once (when wastewater passes through the filtration filter 36 even once), the processing debris is captured in the pores of the filtration filter 36. When the used filtration filter 36 is replaced with an unused filtration filter 36, it is removed from the filter container 38. In this case, the used filtration filter 36 may be used as the sludge filter 26.

[0035] In this modified example, the first pipeline 20 is formed so that fresh water flows into the fresh water tank 16 via the sludge filter 26. That is, the first pipeline 20 is divided into an upstream section 20-1 and a downstream section 20-2. An end (downstream end) of the upstream section 20-1 is connected to a first fluid inlet 34-1 of the filter container 34. The upstream section 20-1 guides fresh water pumped up from the fresh water tank 16 to the sludge filter 26. An end (upstream end) of the downstream section 20-2 is connected to a fluid outlet 34-3 of the filter container 34. The downstream section 20-2 guides fresh water flowing out from the sludge filter 26 to the fresh water tank 16.

[0036] Furthermore, in this modified example, the control device 32 compares the resistivity value measured by the resistivity meter 30 with a predetermined threshold value regardless of whether wastewater is being supplied to the filtration filter 36. When the resistivity value falls below the predetermined threshold value, the control device 32 continues to supply clean water to the sludge filter 26 until the resistivity value exceeds the threshold value.

[0037] According to this modified example, even while wastewater is being filtered by the filtration filter 36, the fresh water stored in the fresh water tank 16 can be passed through the pores of the sludge filter 26, thereby improving the resistivity of the fresh water.

[0038] (Modification 2) Fig. 3 is a schematic diagram showing the configuration of the electric discharge machine 10 according to Modification 2. In Fig. 3, the same reference numerals are used to designate components equivalent to those described in the embodiment and Modification 1. Note that in this modification, explanations that overlap with the embodiment will be omitted.

[0039] In this modified example, only the first pipe 20 differs from modified example 1. In modified example 1, the first pipe 20 is formed so that fresh water flows into the fresh water tank 16 via the sludge filter 26. On the other hand, in this modified example, the first pipe 20 is formed so that fresh water flows into the wastewater tank 14 via the sludge filter 26. That is, in this modified example, the downstream portion 20-2 of the first pipe 20 guides the fresh water flowing out from the sludge filter 26 to the wastewater tank 14.

[0040] In this modified example, as in the first modified example, the resistivity value of the clean water can be improved.

[0041] (Modification 3) Fig. 4 is a schematic diagram showing the configuration of the electric discharge machine 10 according to Modification 3. In Fig. 4, the same reference numerals are used to designate components equivalent to those described in the embodiment and Modification 1. Note that in this modification, explanations that overlap with the embodiment will be omitted.

[0042] In this modified example, a machining tank 40 is newly provided. The machining tank 40 is a water tank that stores machining fluid for immersing the workpiece. The machining tank 40 is installed on the upper surface of an installation stand 42. In this modified example, the first pipeline 20 is formed so that fresh water flows into the machining tank 40 via the sludge filter 26. In other words, the downstream portion 20-2 of the first pipeline 20 guides the fresh water flowing out from the sludge filter 26 to the machining tank 40. In this modified example, as in modified example 1, the resistivity value of the fresh water can be improved.

[0043] In this modified example, a third pipe line 44 is connected to the machining tank 40. The third pipe line 44 guides the machining fluid stored in the machining tank 40 to the wastewater tank 14. An on-off valve 46 is provided in the third pipe line 44. The on-off valve 46 is configured to be able to switch between opening and closing the third pipe line 44. When the on-off valve 46 is open, the third pipe line 44 is open. When the on-off valve 46 is closed, the third pipe line 44 is closed. The on-off valve 46 is opened and closed by the control device 32.

[0044] The control device 32 opens the on-off valve 46 at a predetermined timing, such as when the machining of the workpiece is completed, to discharge the machining fluid stored in the machining tank 40 into the wastewater tank 14. In this case, the control device 32 may open the on-off valve 28 and drive the first pump 18 to supply clean water to the machining tank 40 in an amount equivalent to the amount of machining fluid discharged into the wastewater tank 14. This makes it possible to prevent a significant increase in the ion concentration of the machining fluid stored in the machining tank 40, and as a result, to prevent a decrease in machining accuracy.

[0045] (Variation 4) The resistivity meter 30 may be replaced with a conductivity meter. The conductivity meter measures the conductivity of the fresh water stored in the fresh water tank 16 and outputs a signal indicating the conductivity to the control device 32. In this variation, the control device 32 compares the conductivity measured by the conductivity meter with a predetermined threshold value. In addition, in this variation, when the conductivity is equal to or greater than the predetermined threshold value, the control device 32 drives the first pump 18 and opens the on-off valve 28. This variation is not limited to the embodiment, and can be applied to any of Variations 1 to 3.

[0046] (Variation 5) The control device 32 may control the inverter that drives the first pump 18 to adjust the flow rate of fresh water in the first pipeline 20. In this case, the on-off valve 28 may be removed. Furthermore, if the on-off valve 28 is a solenoid valve whose opening degree is adjustable, the control device 32 may control the opening degree of the on-off valve 28 to adjust the flow rate of fresh water in the first pipeline 20. This variation is not limited to the embodiment, and may be applied to any of Variations 1 to 3.

[0047] (Modification 6) The sludge filter 26 may be provided in the clean water tank 16. This modification is not limited to the embodiment, and can be applied to any of Modifications 1 to 3.

[0048] [Invention] The invention and its effects that can be understood from the above description will be described below.

[0049] (1) The present invention is an electric discharge machine (10) that uses electric discharges to machine a workpiece placed in a machining fluid, and includes a wastewater tank (14) that stores wastewater, which is the machining fluid containing machining chips generated by machining the workpiece, a freshwater tank (16) that stores freshwater, which is the machining fluid from which the machining chips have been removed from the wastewater, a first pipeline (20) that guides the freshwater pumped up from the freshwater tank, and a sludge filter (26) that is a porous body having pores through which the freshwater supplied from the first pipeline passes, and in which the machining chips are captured in the pores.

[0050] This allows the clean water, from which the machining debris has been removed, to be intentionally passed through the pores that capture the machining debris, thereby increasing the resistivity of the clean water. Therefore, the resistivity of the clean water can be improved without using a commonly used ion exchange resin. As a result, the resistivity of the machining fluid can be efficiently improved.

[0051] (2) The present invention is an electric discharge machine including a second pipeline (24) for guiding the machining fluid from the wastewater tank to the freshwater tank, and a filter (36) provided in the second pipeline for removing the machining debris from the wastewater, and the sludge filter may be separate from the filter. This makes it possible to improve the resistivity of the freshwater while removing the machining debris from the wastewater.

[0052] (3) In the electric discharge machine of the present invention, the first pipe may be formed so that the fresh water flows into the fresh water tank via the sludge filter, thereby stabilizing the resistivity of the fresh water stored in the fresh water tank.

[0053] (4) In the electric discharge machine of the present invention, the first pipe may be formed so that the clean water flows into the wastewater tank via the sludge filter, thereby stabilizing the resistivity of the wastewater stored in the wastewater tank.

[0054] [Correction based on Rule 91 05.07.2023] (5) In the present invention, the first pipe may be configured so that the clean water flows through the sludge filter into a machining tank (40) that stores the machining fluid for immersing the workpiece. This stabilizes the resistivity of the machining fluid stored in the machining tank. As a result, it is possible to prevent a significant increase in the ion concentration of the machining fluid and a decrease in machining accuracy.

[0055] (6) The present invention may be an electric discharge machine including a second pipeline that guides the machining fluid from the dirty water tank to the clean water tank, the sludge filter being provided in the second pipeline, and the first pipeline directing the clean water to the sludge filter. This allows the sludge filter, which increases the resistivity of the clean water, to be used as a filtering filter as well. As a result, the resistivity of the machining fluid can be efficiently improved.

[0056] (7) The present invention may be an electric discharge machine, and the sludge filter may be the porous body that was used to remove the machining debris. This allows the filtration filter to be recycled as a sludge filter.

[0057] (8) In the electric discharge machine of the present invention, the machining waste may contain at least one of iron, aluminum, copper, zinc, cemented carbide, tungsten, molybdenum, carbon, titanium, silicon, manganese, chromium, phosphorus, sulfur, and nickel, thereby appropriately increasing the resistivity of the clean water.

[0058] (9) The present invention may be an electric discharge machine including a resistivity meter (30) that measures the resistivity of the fresh water, a pump (18) that pumps the fresh water from the fresh water tank, and a control device (32) that controls the pump to pump the fresh water when the resistivity is equal to or less than a predetermined threshold. This makes it possible to reliably suppress an increase in the ion concentration of the fresh water.

[0059] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention.

[0060] REFERENCE SIGNS LIST 10... Electric discharge machine 14... Sewage tank 16... Fresh water tank 18... First pump 20... First pipeline 22... Second pump 24... Second pipeline 26... Sludge filter 28, 46... On-off valve 30... Resistivity meter 32... Control device 34, 38... Filter container 36... Filtration filter 40... Machining tank

Claims

1. An electric discharge machine that uses electric discharge to machine an object to be machined that is placed in a machining fluid, a wastewater tank for storing wastewater, which is the processing liquid including processing waste generated by processing the object to be processed; a fresh water tank for storing fresh water, which is the machining fluid obtained by removing the machining debris from the wastewater; A first pipeline for guiding the fresh water pumped from the fresh water tank; a sludge filter which is a porous body having pores through which the fresh water supplied from the first pipeline passes, and in which the processing waste is captured in the pores; An electric discharge machine comprising:

2. 2. The electric discharge machine according to claim 1, a second pipeline for conducting the machining fluid from the wastewater tank to the fresh water tank; A filter provided in the second pipeline for removing the processing waste from the wastewater; Equipped with The electric discharge machine, wherein the sludge filter is separate from the filtration filter.

3. 3. The electric discharge machine according to claim 2, The first pipeline is formed so that the fresh water flows into the fresh water tank via the sludge filter.

4. 3. The electric discharge machine according to claim 2, The first pipeline is formed so that the fresh water flows into the sewage tank via the sludge filter.

5. 3. The electric discharge machine according to claim 2, The first pipeline is formed so that the clean water flows through the sludge filter into a machining tank that stores the machining fluid in which the workpiece is immersed.

6. 2. The electric discharge machine according to claim 1, a second pipeline for conducting the machining fluid from the wastewater tank to the fresh water tank; The sludge filter is provided in the second pipeline, The first pipe guides the clean water to the sludge filter.

7. The electric discharge machine according to any one of claims 2 to 6, The sludge filter is the porous body used to remove the machining waste.

8. The electric discharge machine according to any one of claims 1 to 6, The scrap comprises at least one of iron, aluminum, copper, zinc, carbide, tungsten, molybdenum, carbon, titanium, silicon, manganese, chromium, phosphorus, sulfur, and nickel.

9. The electric discharge machine according to any one of claims 1 to 6, A resistivity meter for measuring the resistivity value of the fresh water; A pump for pumping the fresh water from the fresh water tank; A control device that controls the pump to pump the fresh water when the resistivity value is equal to or less than a predetermined threshold value; An electric discharge machine comprising: