JPWO2020031251A1 - Electric discharge machining apparatus and electric discharge machining method - Google Patents

Abstract

The electric discharge machine (100) applies a voltage between the wire electrode (10) and the work piece (25), and in the working liquid, a gap between the wire electrode (10) and the work piece (25). The work piece (25) is processed by causing an electric discharge to. The electric discharge machining apparatus (100) has a first dimension for cutting a target shape from a workpiece (25) with a first dimension accuracy and a first dimension for the workpiece (25) subjected to the first dimension. A machining control unit that controls the second machining that cuts out a target shape with a second dimensional accuracy higher than the precision, and an adjustment that causes the amount of oxygen contained in the machining fluid to be larger in the first machining than in the second machining. And an oxygen amount adjusting unit for performing.

Description

The present invention relates to an electric discharge machining apparatus and an electric discharge machining method for performing electric discharge machining on a workpiece.

2. Description of the Related Art There is known an electric discharge machining apparatus that melts a workpiece by using heat generated by an electric discharge between a wire electrode and the workpiece to machine the workpiece. Patent Document 1 discloses an electric discharge machining apparatus that performs machining by including fine bubbles containing oxygen in a machining liquid. According to the technique of Patent Document 1, the electric discharge machining apparatus can increase the machining speed by increasing the vaporization and explosion of the machining fluid by adding the heat of oxidation to the heat of oxidation.

JP-A-2-100823

Conventionally, an electric discharge machining apparatus may be used for machining a workpiece whose main component is tungsten carbide (WC) which is a cemented carbide. Among the materials targeted for electrical discharge machining, WC has a very high melting point of approximately 2900°C. Therefore, in electrical discharge machining of cemented carbide, the proportion of the portion melted by receiving electrical discharge from the workpiece. Has been reported to stay below 10%. In electric discharge machining of cemented carbide, most of the melted portion is solidified again and remains on the workpiece, so that the electric discharge machine requires time for machining the cemented carbide.

In the processing of cemented carbide, when the processing liquid contains fine bubbles as in the technique of Patent Document 1, the presence of oxygen causes a decomposition reaction of WC at a temperature lower than the melting point of WC. Since the decomposition of WC progresses at a temperature closer to room temperature than the melting point, the processing by decomposition progresses more easily than the processing by melting. Therefore, the processing speed can be improved by adding the processing by decomposition to the processing by melting. The electric discharge machining apparatus can shorten the time required for machining the cemented carbide by improving the machining speed. However, since the processing by disassembly proceeds while collapsing the surface of the workpiece, it becomes difficult to obtain a high-quality machined surface by the processing by disassembly. For this reason, when the technique of Patent Document 1 is applied to the processing of the workpiece, the processing time can be shortened, but it may be difficult to obtain a high-quality processed surface. there were.

The present invention has been made in view of the above, and an object of the present invention is to obtain an electric discharge machining apparatus that can shorten the machining time and can obtain a high-quality machined surface.

In order to solve the above-mentioned problems and to achieve the object, an electric discharge machining apparatus according to the present invention applies a voltage between a wire electrode and a workpiece, and in a machining fluid, the wire electrode and the workpiece. The work piece is processed by generating an electric discharge in the gap between and. The electric discharge machining apparatus according to the present invention includes a first machining for cutting a target shape from a workpiece with a first dimensional accuracy, and a first machining with a first dimensional accuracy higher than a first dimensional accuracy. A machining control unit that controls the second machining for cutting out the target shape with a dimensional accuracy of 2, and an oxygen amount adjustment that adjusts the amount of oxygen contained in the machining fluid to be larger in the first machining than in the second machining. And a section.

INDUSTRIAL APPLICABILITY The electric discharge machining apparatus according to the present invention has an effect that machining time can be shortened and a high quality machining surface can be obtained.

The figure which shows the schematic structure of the electrical discharge machining apparatus concerning Embodiment 1 of this invention. Block diagram showing a functional configuration of a control device included in the electric discharge machining apparatus shown in FIG. The flowchart which shows the procedure of the electrical discharge machining method which the electrical discharge machining apparatus shown in FIG. 1 performs. The figure which shows the modification of the structure for the supply of bubbles in the electric discharge machine shown in FIG. The figure which shows schematic structure of the electrical discharge machining apparatus concerning Embodiment 2 of this invention. The flowchart which shows the procedure of the electrical discharge machining method which the electrical discharge machining apparatus shown in FIG. 5 performs. The figure which shows schematic structure of the electrical discharge machining apparatus concerning Embodiment 3 of this invention. The flowchart which shows the procedure of the electrical discharge machining method which the electrical discharge machining apparatus shown in FIG. 7 performs.

Hereinafter, an electric discharge machine and an electric discharge method according to an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a schematic configuration of an electric discharge machine 100 according to a first embodiment of the present invention. The electric discharge machining apparatus 100 applies a voltage between the wire electrode 10 and the workpiece 25 to generate an electric discharge in a gap in which the wire electrode 10 and the workpiece 25 face each other in the machining fluid, and The workpiece 25, which is a hard alloy, is processed. The workpiece 25 is a tungsten carbide-cobalt (WC-Co)-based alloy that has WC as a main component and is mixed with cobalt (Co) that is a binder and sintered.

The electric discharge machine 100 has a wire bobbin 11 on which a linear wire electrode 10 is drawn. The wire electrode 10 fed from the wire bobbin 11 is hung on the pulley 12 and then passed through the upper guide portion 13 and the lower guide portion 14. The upper guide portion 13 and the lower guide portion 14 are guide portions that guide the traveling of the wire electrode 10. The wire electrode 10 is hooked on the pulley 17 in the lower guide portion 14 and then wound up by a wire collecting bobbin provided outside the lower guide portion 14. In FIG. 1, the wire recovery bobbin is not shown.

The workpiece 25 is placed on a stage arranged between the upper nozzle 15 of the upper guide portion 13 and the lower nozzle 16 of the lower guide portion 14 in the processing tank 19. The stage moves in a plane orthogonal to the traveling direction of the wire electrode 10 between the upper guide portion 13 and the lower guide portion 14. In FIG. 1, the illustration of the stage is omitted. In the processing tank 19, deionized water as a processing liquid is stored. The surface of the processing liquid in the processing tank 19 reaches the upper guide portion 13. A lower end portion of the upper guide portion 13 including the upper nozzle 15 is immersed in the working liquid. In the processing tank 19, the lower guide portion 14, the stage, and the workpiece 25 are submerged in the processing liquid below the upper nozzle 15.

At least one of the upper nozzle 15 of the upper guide portion 13 and the lower nozzle 16 of the lower guide portion 14 jets the working liquid toward the working groove 26. In FIG. 1, the illustration of the structure for jetting the working fluid is omitted. By the electric discharge machining on the workpiece 25, a machining groove 26 is formed on the workpiece 25 along the traveling direction of the wire electrode 10 between the upper guide portion 13 and the lower guide portion 14.

The upper guide portion 13 is provided with a power supply 18 that connects the wire electrode 10 and the processing power supply 21. The processing power source 21 is connected to the power supply terminal 18 and the workpiece 25, and supplies the processing energy in a pulse shape between the power supply terminal 18 and the workpiece 25.

The electric discharge machining apparatus 100 has a gas supply device 22 and an opening/closing valve 23, which are oxygen amount adjusting units that adjust the amount of oxygen contained in the machining fluid. The gas supply device 22 has a gas cylinder filled with oxygen gas. The gas supply device 22 supplies the oxygen gas to the inside of the processing tank 19 by sending the oxygen gas to the pipe 24. A nozzle 27 for releasing oxygen gas is provided at an end of the pipe 24 opposite to the gas supply device 22. The nozzle 27 is arranged below the wire electrode 10 that runs between the lower nozzle 16 and the pulley 17 in the lower guide portion 14. The on-off valve 23 provided in the pipe 24 switches between an open state in which oxygen gas passes and a closed state in which oxygen gas is shut off.

The control device 20 controls the entire electric discharge machine 100. The control device 20 controls the application of the pulse voltage by the processing power supply 21, and also controls the supply of oxygen gas by the gas supply device 22 and the opening/closing of the opening/closing valve 23.

FIG. 2 is a block diagram showing a functional configuration of the control device 20 included in the electric discharge machine 100 shown in FIG. The control device 20 includes a processing control unit 31 that is a functional unit that controls the processing of the workpiece 25, a gas supply control unit 32 that is a functional unit that controls the gas supply device 22 and the opening/closing valve 23, and the wire electrode 10. It has a wire supply speed control unit 33 which is a functional unit for controlling the supply speed.

The wire supply speed control unit 33 controls the supply speed of the wire electrode 10 by controlling the operation of the wire bobbin 11 and the wire recovery bobbin. The processing control unit 31 controls the relative position of the wire electrode 10 on the workpiece 25 by controlling the operation of the stage. The machining control unit 31 controls rough machining, which is the first machining, and finish machining, which is the second machining, according to the machining program. Roughing is a process of cutting out a target shape from the workpiece 25 with the first dimensional accuracy. The finishing process is a process of cutting out a target shape from the workpiece 25 that has been rough-processed with a second dimensional accuracy higher than the first dimensional accuracy.

The electric discharge machining apparatus 100 performs cutting by rough machining from the workpiece 25 in the initial state before machining is performed to a rough intermediate shape in which a removed amount is left until the final shape is obtained. The first dimensional accuracy may be any dimensional accuracy with which a rough intermediate shape can be obtained. The finishing process is a process after obtaining the final shape after the roughing process. The second dimensional accuracy is the dimensional accuracy required to obtain the final shape. Finishing includes not only final finishing for obtaining a final shape, but also intermediate finishing performed between roughing and final finishing.

The gas supply control unit 32 performs an operation of sending out oxygen gas from the gas supply device 22 and opening the on-off valve 23 during rough machining. By sending out oxygen gas from the gas supply device 22 and opening the on-off valve 23, bubbles of oxygen gas are generated from the nozzle 27. Oxygen gas bubbles are bubbles larger than micro bubbles, which are bubbles having a diameter of about 1 μm to 50 μm, and are bubbles that can easily float and disappear on the liquid surface as compared with micro bubbles. ..

When the bubbles are discharged from the nozzle 27 in the lower guide portion 14, the bubbles rise along the wire electrode 10 due to the buoyancy force received from the working liquid. The bubbles emitted from the lower nozzle 16 float between the wire electrode 10 and the wall of the processing groove 26. As a result, the gas supply device 22 and the on-off valve 23 supply oxygen to the machining liquid in the gap between the wire electrode 10 and the workpiece 25.

The gas supply control unit 32 performs an operation of stopping the supply of oxygen gas to the gas supply device 22 and closing the opening/closing valve 23 during the finishing process. The gas supply device 22 and the opening/closing valve 23 stop the emission of bubbles from the nozzle 27.

The gas supply device 22 and the opening/closing valve 23 supply oxygen gas to the gap between the wire electrode 10 and the workpiece 25 in rough machining, and to the gap between the wire electrode 10 and workpiece 25 in finishing. Stop the supply of oxygen gas. In this way, the gas supply device 22 and the opening/closing valve 23 perform adjustment so that the amount of oxygen contained in the working liquid in the gap between the wire electrode 10 and the workpiece 25 is greater in rough machining than in finish machining. .. In the first embodiment, the amount of oxygen is the amount of bubbles in the working fluid or the amount of oxygen dissolved in the working fluid.

During rough machining, the electric discharge machining apparatus 100 decomposes WC into tungsten (W) and carbon (C) by generating electric discharge while supplying oxygen to the gap between the wire electrode 10 and the workpiece 25. .. The presence of oxygen causes a decomposition reaction of WC represented by the following chemical reaction formula.
WC→W+C
2W+3O ₂ → 2WO ₃
C+O ₂ → CO ₂ ↑

The decomposition reaction of WC occurs at 600° C. to 700° C., which is lower than the melting point of WC, which is approximately 2900° C. Since the decomposition of WC progresses at a temperature closer to room temperature than the melting point, the processing by decomposition progresses more easily than the processing by melting. Therefore, in the electric discharge machining apparatus 100, in rough machining, machining by melting is added to machining by melting, so that the machining speed can be improved. The electric discharge machining apparatus 100 can shorten the time required for machining the workpiece 25 by improving the machining speed in rough machining.

The electric discharge machine 100 stops the supply of oxygen to the gap between the wire electrode 10 and the workpiece 25 during the finishing process. The amount of oxygen contained in the working fluid is returned to the original amount before the oxygen gas was supplied to the working fluid during rough machining. Since the bubbles released into the working fluid during rough machining can be easily eliminated as described above, it is possible to easily switch from the state in which bubbles are present to the state in which there are no bubbles. ..

In the electric discharge machining apparatus 100, in the finishing machining, the electric discharge is generated in the machining liquid in which the amount of oxygen is smaller than that in the rough machining so that the machining by the decomposition of the WC is not performed and the machining by the dissolution of the WC is performed. The electric discharge machining apparatus 100 can perform the machining while suppressing the deterioration of the quality of the machined surface by performing the machining only by melting the WC without performing the machining by disassembling the WC. The electric discharge machining apparatus 100 can obtain a high-quality machined surface in the final shape by suppressing deterioration of the quality of the machined surface in the finishing machining.

Although oil may be used as a machining fluid for electric discharge machining in addition to water, water can dissolve oxygen more easily than oil. Since the machining liquid used for machining the work piece 25 is water, the electric discharge machining apparatus 100 can easily perform an adjustment to increase the amount of oxygen contained in the machining liquid in rough machining rather than finish machining. ..

FIG. 3 is a flowchart showing a procedure of an electric discharge machining method performed by the electric discharge machine 100 shown in FIG. In step S1, the electric discharge machining apparatus 100 starts supplying oxygen gas to the gap between the workpiece 25 and the wire electrode 10 by sending out oxygen gas from the gas supply device 22 and opening the opening/closing valve 23. In step S2, the electric discharge machining apparatus 100 rough-machines the workpiece 25 according to the machining program.

After finishing the rough machining in step S2, the electric discharge machine 100 stops the supply of oxygen gas from the gas supply device 22 and closes the on-off valve 23 to stop the supply of oxygen gas in step S3. In step S4, the electric discharge machine 100 finishes the workpiece 25 according to the machining program. The electric discharge machine 100 ends the operation shown in FIG. 3 after finishing the finishing in step S4.

The function of the control device 20 included in the electric discharge machine 100 is realized by a processing circuit. The processing circuit is dedicated hardware mounted in the control device 20 of the electric discharge machine 100. The processing circuit may be a processor that executes a program stored in the memory.

The processing circuit that is dedicated hardware is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. Is.

The function of the control device 20 may be realized by a processor that executes a program stored in the memory. The processor and memory are communicatively connected to each other. The processor is a CPU (Central Processing Unit), a processing device, a computing device, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor). Each function of the processing control unit 31, the gas supply control unit 32, and the wire supply speed control unit 33 included in the control device 20 is realized by a processor, software, firmware, or a combination of software and firmware. The software or firmware is described as a program and stored in the memory. The memory is nonvolatile or volatile such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (registered trademark) (Electrically Erasable Programmable Read-Only Memory). Built-in memory such as semiconductor memory.

Part of the function of the control device 20 may be realized by dedicated hardware, and the other part of the function of the control device 20 may be realized by software or firmware. Thus, the function of the control device 20 can be realized by hardware, software, firmware, or a combination thereof.

The gas supplied to the gap between the wire electrode 10 and the workpiece 25 is not limited to oxygen gas, which is a pure substance, and may be any mixed gas containing oxygen. The gas supply device 22 may supply air. In this case, the gas supply device 22 adjusts the amount of oxygen contained in the working fluid by supplying air. The gas supply device 22 may be a pump that takes in air from around the electric discharge machine 100 and sends out the taken-in air.

The configuration for supplying bubbles to the lower guide portion 14 may be changed as appropriate. FIG. 4 is a diagram showing a modification of the configuration for supplying bubbles in the electric discharge machine 100 shown in FIG. FIG. 4 shows a cross-sectional configuration of the lower guide portion 51 having the configuration according to the modified example. In the modified example shown in FIG. 4, the ventilation path 53 and the ventilation port 54, which are configurations for transporting the wire electrode 10 passed through the lower guide portion 51, are diverted to supply air during roughing.

The lower guide portion 51 is provided with a traveling path 55 for the wire electrode 10 from the lower nozzle 16 to the tip of the pulley 17. The end portion 52 of the traveling path 55 on the lower nozzle 16 side has a funnel shape in which the diameter becomes smaller as it goes downward. The lower guide portion 51 is provided with a vent hole 54 through which air passes, and a vent passage 53 connecting the vent hole 54 and the end portion 52.

In preparation for processing, when the wire electrode 10 fed from the wire bobbin 11 is passed through the lower guide portion 51, air is sent from the gas supply device 22 connected to the ventilation port 54 to the end portion 52 via the ventilation path 53. By sending the air to the end portion 52, the working fluid is pushed out from the end portion 52 toward the end of the travel path 55, and a flow of the working fluid toward the end of the travel path 55 is generated. The wire electrode 10 is conveyed toward the end of the traveling path 55 along with the flow of the working liquid, so that the wire electrode 10 is passed through the lower guide portion 51. When the wire electrode 10 is transported, the pressure of the air supplied to the end portion 52 is adjusted to a pressure that allows the working fluid to advance toward the end of the traveling path 55 together with the air.

In the rough machining, the electric discharge machine 100 sends air from the pump to the end portion 52 through the ventilation passage 53. In the case of rough machining, the pressure of the air supplied to the end portion 52 is weakened as compared with the case of carrying the wire electrode 10. Since the pressure of the air is weakened, most of the bubbles discharged from the air passage 53 to the end portion 52 rise to the lower nozzle 16 due to buoyancy. Accordingly, the electric discharge machine 100 supplies air to the gap between the wire electrode 10 and the workpiece 25 by using the configuration for transporting the wire electrode 10 in the lower guide portion 51. As described above, the electric discharge machining apparatus 100 can perform adjustment so that the amount of air contained in the machining liquid in the gap between the wire electrode 10 and the workpiece 25 is larger in rough machining than in finishing machining. According to the present modification, the electric discharge machining apparatus 100 uses the ventilation passage 53 and the ventilation port 54 for transporting the wire electrode 10 to supply air in rough machining, and thus is configured to supply air in rough machining. It is possible to reduce the number of parts as compared with the case of separately providing.

The electric discharge machine 100 is not limited to the one that supplies oxygen from below to the gap between the wire electrode 10 and the workpiece 25. The electric discharge machine 100 may supply bubbles to the gap between the wire electrode 10 and the workpiece 25 from above. The electric discharge machine 100 may supply bubbles from above to the gap between the wire electrode 10 and the workpiece 25 by ejecting bubbles together with the machining liquid from the upper nozzle 15 of the upper guide portion 13. The electric discharge machining apparatus 100 may inject bubbles together with the machining liquid from the lower nozzle 16 of the lower guide portion 14 in order to supply the bubbles from below. The electric discharge machining apparatus 100 may supply air bubbles to the gap between the wire electrode 10 and the workpiece 25 from both below and above during rough machining. The electric discharge machining apparatus 100 supplies air bubbles to the gap between the wire electrode 10 and the workpiece 25 from at least one of the lower side and the upper side, so that the amount of oxygen contained in the machining fluid is made rougher than in the finishing machining. It can be increased in processing.

According to the first embodiment, the electric discharge machining apparatus 100 uses the gas supply device 22 and the opening/closing valve 23 to make adjustment so that the amount of oxygen contained in the machining fluid is larger in rough machining than in finishing machining. The electric discharge machining apparatus 100 accelerates the decomposition of the cemented carbide by increasing the amount of oxygen during rough machining, thereby improving the machining speed. The electric discharge machining apparatus 100 performs the machining by melting the cemented carbide instead of decomposing the cemented carbide by reducing the amount of oxygen in the finishing machining as compared with the rough machining. The electric discharge machining apparatus 100 can perform machining in finish machining while suppressing deterioration of the quality of the machined surface. As a result, the electric discharge machine 100 has an effect that the machining time can be shortened and a high quality machined surface can be obtained.

Embodiment 2.
FIG. 5 is a diagram showing a schematic configuration of an electric discharge machine 101 according to the second exemplary embodiment of the present invention. The electric discharge machine 101 includes a first tank 61 and a second tank 62 for supplying machining liquids having different amounts of oxygen. In the second embodiment, the same parts as those in the first embodiment are designated by the same reference numerals, and configurations different from the first embodiment will be mainly described.

The first tank 61 is provided with a bubble generator for increasing dissolved oxygen contained in the working fluid. The amount of dissolved oxygen in the first working liquid, which is the working liquid stored in the first tank 61, is higher than that in the normal working liquid due to the operation of the bubble generator. The second tank 62 stores a second working fluid which is a normal working fluid in which the dissolved oxygen is not increased. The amount of oxygen contained in the first working fluid is made larger than that of the second working fluid stored in the second tank 62. In the second embodiment, the amount of oxygen is the amount of dissolved oxygen in the working fluid.

The electric discharge machine 101 includes pumps 63 and 64, which are oxygen amount adjusting units, and open/close valves 65, 66, 67, and 68. The pump 63 sends the first working liquid stored in the first tank 61 to the pipe 71. The pipe 71 is branched into two. The on-off valve 65 is provided on one of the two pipes 71 that are branched. The on-off valve 66 is provided on the other of the two pipes 71 that are branched. The pump 64 sends out the second machining liquid stored in the second tank 62 to the pipe 72. The pipe 72 is branched into two. The on-off valve 67 is provided in one of the two pipes 72 that are branched. The on-off valve 68 is provided on the other of the two pipes 72 that are branched.

The pipe 71 provided with the open/close valve 65 and the pipe 72 provided with the open/close valve 67 are joined together into one pipe 60. The pipe 60 is connected to the upper guide portion 13. The pipe 71 provided with the open/close valve 66 and the pipe 72 provided with the open/close valve 68 are joined together into one pipe 70. The pipe 70 is connected to the lower guide portion 14. The first working liquid and the second working liquid that have passed through the pipe 60 are supplied to the upper guide portion 13. The first working liquid and the second working liquid that have passed through the pipe 70 are supplied to the lower guide portion 14.

The gas supply control unit 32 shown in FIG. 2 controls the operation of the pumps 63 and 64 and the opening and closing of the open/close valves 65, 66, 67 and 68. During rough processing, the gas supply control unit 32 operates the pump 63 and stops the pump 64. Further, the gas supply control unit 32 performs an operation of opening the open/close valves 65 and 66 and an operation of closing the open/close valves 67 and 68. The opening/closing valve 65 is opened along with the operation of the pump 63, so that the first machining liquid supplied to the upper guide portion 13 through the pipe 60 is jetted from the upper nozzle 15 of the upper guide portion 13. When the opening/closing valve 66 is opened along with the operation of the pump 63, the first machining liquid supplied to the lower guide portion 14 through the pipe 70 is jetted from the lower nozzle 16 of the lower guide portion 14.

At the time of finishing, the gas supply control unit 32 stops the pump 63 and operates the pump 64. Further, the gas supply control unit 32 performs an operation of closing the opening/closing valves 65 and 66 and an operation of opening the opening/closing valves 67 and 68. When the opening/closing valve 67 is opened along with the operation of the pump 64, the second machining liquid supplied to the upper guide portion 13 through the pipe 60 is jetted from the upper nozzle 15 of the upper guide portion 13. When the opening/closing valve 68 is opened as the pump 64 operates, the second machining liquid supplied to the lower guide portion 14 through the pipe 70 is ejected from the lower nozzle 16 of the lower guide portion 14.

The pumps 63, 64 and the on-off valves 65, 66, 67, 68 supply the first machining liquid to the gap between the wire electrode 10 and the workpiece 25 in rough machining, and the wire electrode 10 and workpiece in finishing machining. The second working liquid is supplied to the gap with the object 25. As a result, the pumps 63, 64 and the on-off valves 65, 66, 67, 68 change the amount of oxygen gas contained in the working liquid in the gap between the wire electrode 10 and the workpiece 25 in rough machining rather than finish machining. Make more adjustments.

FIG. 6 is a flowchart showing a procedure of an electric discharge machining method performed by the electric discharge machine 101 shown in FIG. In step S11, the electric discharge machining apparatus 101 starts supplying the first machining liquid to the gap between the workpiece 25 and the wire electrode 10 by operating the pump 63 and opening the opening/closing valves 65 and 66. In step S12, the electric discharge machining apparatus 101 rough-machines the workpiece 25 according to the machining program.

After finishing the rough machining in step S12, the electric discharge machining apparatus 101 stops the operation of the pump 63 and closes the opening/closing valves 65 and 66 to stop the supply of the first machining fluid in step S13. Further, in step S13, the electric discharge machining apparatus 101 starts supplying the second machining liquid to the gap between the workpiece 25 and the wire electrode 10 by operating the pump 64 and opening the opening/closing valves 67 and 68. To do. In step S14, the electric discharge machining apparatus 101 finishes the workpiece 25 according to the machining program.

After finishing the finishing process in step S14, the electric discharge machining apparatus 101 stops the operation of the pump 64 and closes the opening/closing valves 67 and 68 to stop the supply of the second machining liquid in step S15. As a result, the electric discharge machine 101 ends the operation shown in FIG.

The electric discharge machine 101 is not limited to one that supplies the first machining liquid and the second machining liquid from both the upper guide portion 13 and the lower guide portion 14. The electric discharge machine 101 may supply the first machining liquid and the second machining liquid from one of the upper guide portion 13 and the lower guide portion 14. The electric discharge machining apparatus 101 supplies the first machining fluid and the second machining fluid from at least one of the upper guide section 13 and the lower guide section 14 to reduce the amount of oxygen contained in the machining fluid. More can be done in roughing than in finishing.

According to the second embodiment, the electric discharge machining apparatus 101 supplies the first machining liquid in the rough machining and supplies the second machining liquid in the finishing machining, so that the gap between the wire electrode 10 and the workpiece 25 is increased. Adjustment is performed so that the amount of oxygen contained in the working fluid in step 2 is larger in roughing than in finishing. As a result, the electric discharge machining apparatus 101 has an effect that the machining time can be shortened and a high quality machined surface can be obtained.

Embodiment 3.
FIG. 7 is a diagram showing a schematic configuration of an electric discharge machine 102 according to the third exemplary embodiment of the present invention. The electric discharge machining device 102 includes a cooling device 82 that cools the machining fluid by increasing the cooling strength in rough machining rather than finish machining. In the third embodiment, the same parts as those of the first and second embodiments are designated by the same reference numerals, and the configuration different from those of the first and second embodiments will be mainly described.

The electric discharge machine 102 includes a tank 80 that stores a machining liquid. The tank 80 stores the working liquid before being passed through the cooling device 82. The pump 81 sends the machining liquid stored in the tank 80 to the pipe 73 via the cooling device 82. The cooling device 82 cools the working liquid from the tank 80. The pipe 73 is branched into two pipes 60 and 70. The pipe 60 is connected to the upper guide portion 13. The pipe 70 is connected to the lower guide portion 14. The working liquid that has passed through the pipe 60 is supplied to the upper guide portion 13. The working liquid that has passed through the pipe 70 is supplied to the lower guide portion 14.

It is known that the lower the temperature of the working fluid, the greater the amount of dissolved oxygen in the working fluid. The cooling device 82, which is an oxygen amount adjusting unit, lowers the temperature of the working liquid in the roughing process rather than the finishing process by cooling the working liquid in the roughing process and stopping the cooling of the working liquid in the finishing process. The cooling device 82 adjusts the amount of oxygen contained in the working fluid to be larger in the roughing than in the finishing by lowering the temperature of the working fluid in the roughing than in the finishing. When cooling the machining fluid in both rough machining and finishing machining, the cooling device 82 cools the machining fluid by increasing the cooling strength in the rough machining rather than the finishing machining so that the machining fluid is rougher than the finishing machining. Lower the temperature of the working fluid. In the second embodiment, the amount of oxygen is the amount of dissolved oxygen in the working fluid.

The gas supply controller 32 shown in FIG. 2 controls the operation of the pump 81 and the operation of the cooling device 82. The gas supply control unit 32 causes the cooling device 82 to perform cooling during rough machining and stops cooling by the cooling device 82 during finish machining. Alternatively, the gas supply control unit 32 controls the cooling strength of the cooling device 82 in rough machining to be higher than the cooling strength of the cooling device 82 in finish machining.

FIG. 8 is a flowchart showing a procedure of an electric discharge machining method performed by the electric discharge machine 102 shown in FIG. In step S21, the electric discharge machining device 102 starts to supply the machining fluid cooled by the cooling device 82. The electric discharge machine 102 supplies the machining liquid to the gap between the workpiece 25 and the wire electrode 10. In step S22, the electric discharge machine 102 rough-machines the workpiece 25 according to the machining program.

After finishing the rough machining in step S22, the electric discharge machine 102 weakens the cooling intensity of the cooling device 82. In step S23, the electric discharge machining apparatus 102 starts supplying the machining fluid whose strength has been weakened and which has been cooled. The electric discharge machine 102 supplies the machining liquid to the gap between the workpiece 25 and the wire electrode 10. In step S24, the electric discharge machine 102 finishes the workpiece 25 according to the machining program.

After finishing the finishing process in step S24, the electric discharge machining device 102 stops the cooling of the machining liquid by the cooling device 82 and the supply of the machining liquid by the pump 81 in step S25. The cooling device 82 may stop cooling the working fluid in step S23 described above. As a result, the electric discharge machine 102 ends the operation shown in FIG.

The electric discharge machine 102 is not limited to one that supplies the machining liquid from both the upper guide portion 13 and the lower guide portion 14. The electric discharge machine 102 may supply the machining liquid from one of the upper guide portion 13 and the lower guide portion 14. The electric discharge machining device 102 supplies the machining fluid from at least one of the upper guide portion 13 and the lower guide portion 14 and changes the temperature of the machining fluid to finish the amount of oxygen contained in the machining fluid. More can be done in roughing than in machining.

In the third embodiment, the electric discharge machining apparatus 102 lowers the temperature of the machining fluid in the rough machining rather than the finishing machining to reduce the amount of oxygen contained in the machining fluid in the gap between the wire electrode 10 and the workpiece 25. Make adjustments that increase the amount of roughing rather than finishing. As a result, the electric discharge machining apparatus 102 has an effect that the machining time can be shortened and a high quality machined surface can be obtained.

The configurations described in the above embodiments are examples of the content of the present invention, and can be combined with another known technique, and the configurations of the configurations are not deviated from the scope not departing from the gist of the present invention. It is also possible to omit or change parts.

10 wire electrode, 11 wire bobbin, 12,17 pulley, 13 upper guide part, 14,51 lower guide part, 15 upper nozzle, 16 lower nozzle, 18 power supply, 19 processing tank, 20 control device, 21 processing power supply, 22 gas Supply device, 23, 65, 66, 67, 68 Open/close valve, 24, 60, 70, 71, 72, 73 Pipe, 25 Workpiece, 26 Processing groove, 27 Nozzle, 31 Processing control section, 32 Gas supply control section , 33 wire supply speed control section, 52 end section, 53 ventilation path, 54 ventilation port, 55 traveling path, 61 first tank, 62 second tank, 63, 64, 81 pump, 80 tank, 82 cooling device, 100, 101, 102 EDM equipment.

Claims (9)

An electric discharge machining apparatus for machining a workpiece by applying a voltage between a wire electrode and the workpiece to generate an electric discharge in a gap between the wire electrode and the workpiece in a machining liquid. There
With a first processing for cutting out a target shape from the workpiece with a first dimensional accuracy, and with a second dimensional accuracy higher than the first dimensional accuracy for the workpiece subjected to the first processing. A machining control unit that controls the second machining for cutting out the target shape;
An oxygen amount adjusting unit that adjusts the amount of oxygen contained in the working liquid to be larger in the first processing than in the second processing;
An electric discharge machine comprising: The electric discharge machining apparatus according to claim 1, wherein the oxygen amount adjustment unit performs the adjustment by supplying a gas containing oxygen to the gap. A guide part for guiding the traveling of the wire electrode,
The oxygen amount adjusting unit performs the adjustment by supplying a gas containing oxygen to the guide unit in the first processing and stopping the supply of a gas containing oxygen in the second processing. The electric discharge machine according to claim 1 or 2. The guide portion is provided with a ventilation path through which air for conveying the wire electrode passes,
The electric discharge machining apparatus according to claim 3, wherein the oxygen amount adjusting unit supplies the gas containing oxygen to the ventilation path. A first tank and a second tank for storing the working fluid;
The amount of oxygen contained in the first working liquid, which is the working liquid stored in the first tank, is larger than that in the second working liquid, which is the working liquid stored in the second tank. ,
The oxygen amount adjusting unit supplies the first working liquid to the gap in the first processing, and supplies the second working liquid to the gap in the second processing, whereby the adjustment is performed. The electric discharge machining apparatus according to claim 1, wherein The electric discharge machining apparatus according to claim 1, wherein the oxygen amount adjusting unit performs the adjustment by lowering the temperature of the working liquid in the first machining rather than in the second machining. In an electric discharge machining method for machining a workpiece by applying a voltage between a wire electrode and the workpiece to generate an electric discharge in a gap between the wire electrode and the workpiece in a machining liquid. ,
A step of increasing the amount of oxygen contained in the machining liquid in the gap to perform a first machining to cut out a target shape from the workpiece with a first dimensional accuracy;
The amount of oxygen contained in the machining liquid in the gap is reduced as compared with that in the first machining so that the second dimension higher than the first dimensional accuracy is obtained from the workpiece subjected to the first machining. A step of performing a second process of cutting out a target shape with dimensional accuracy of
An electric discharge machining method comprising: The electrical discharge machining method according to claim 7, wherein the workpiece is a cemented carbide. The electric discharge machining method according to claim 7, wherein the machining liquid is water.

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