Electric discharge machining method and electric discharge machining device

Abstract

The invention provides an electric spark machining method and an electric spark machining device. The electric spark machining method comprises the following specific steps that a target workpiece is pretreated, and the target workpiece is placed on a heating platform; a tool electrode provided with a cooling component is installed on a machine tool clamp, and a gap between the tool electrode and the target workpiece is adjusted; preheating the target workpiece to a preheating temperature; releasing low-temperature compressed gas to the discharge end of the tool electrode as a cold dielectric medium; the target workpiece is connected with the positive electrode of a pulse power source, the tool electrode is connected with the negative electrode of the pulse power source, the pulse power source applies pulse voltage between the positive electrode and the negative electrode of the pulse power source, and the tool electrode acts in the preset direction; and the preheated target workpiece is subjected to electric spark machining under the action of the cooling component and the cold dielectric medium, so that inter-electrode heat dissipation can be promoted during electric spark machining, the arc discharge probability is reduced, the energy loss is reduced, and the corrosion removal efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of electric spark machining, and in particular to an electric spark machining method and an electric spark machining device. Background Art

[0002] Electrospark machining refers to the process of applying a pulse voltage when the gap between two electrodes reaches a certain distance in a certain medium, and using the pulsed electric spark between the two electrodes to generate transient high temperature and high pressure, so that the electrode material and the base material melt or even vaporize instantly, thereby achieving the purpose of machining the workpiece. Compared with traditional cutting machining, electrospark machining is a non-contact machining that does not generate macroscopic forces, so it is not restricted by the mechanical properties of the material itself, and can process various difficult-to-machine materials, complex-shaped parts, and parts with special requirements. After more than half a century of research and development, electrospark machining has been widely used in aerospace, automotive, biomedical, military, chemical, cutting tools, molds, precision machinery and other fields.

[0003] Traditional EDM is performed in liquid dielectric or gas dielectric, among which liquid dielectric is more widely used, mainly oil-based dielectric represented by kerosene. This type of dielectric has a low flash point and is prone to fire, increasing the risk of processing. In addition, the kerosene temperature rises and is prone to burns on the workpiece. Water-based dielectric represented by deionized water is prone to cause rust of materials, and is prone to boiling and vaporization, forming water vapor on the surface of the base material, which weakens the cooling effect. Gas dielectric has stable dielectric constant, extremely low dielectric loss, is non-flammable and non-explosive, and has good chemical stability. Its application in EDM also has the potential to improve workpiece processing quality and cutting speed.

[0004] In order to improve the stability and processing quality of EDM, many scholars at home and abroad have continuously carried out theoretical innovation and practical exploration in the field of EDM. Studies have shown that cold electrodes help limit the conduction of heat energy to the depth of the electrode, so that the channel heat energy acts on a very small range, thereby reducing electrode damage. Cold electrodes can also reduce the heat-affected zone of the workpiece being processed, avoid excessive heat treatment or deformation, and thus maintain the geometric accuracy and surface quality of the workpiece. Liquid nitrogen cooling of EDM tool electrodes has been studied, but the steps are cumbersome and difficult to implement.

[0005] Therefore, an EDM technical solution is needed, which can solve the technical problems existing in traditional EDM such as excessive temperature leading to large tool electrode loss, easy arc discharge, and low pulse discharge energy utilization. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides an electrospark machining method, comprising the following specific steps:

[0007] Pre-treating a target workpiece and placing the target workpiece on a heating platform;

[0008] Mounting a tool electrode provided with a cooling component on a machine tool fixture, and adjusting a gap between the tool electrode and the target workpiece;

[0009] preheating the target workpiece to a preheating temperature;

[0010] releasing low-temperature compressed gas as a cold dielectric to the discharge end of the tool electrode;

[0011] The target workpiece is connected to the positive electrode of a pulse power supply, and the tool electrode is connected to the negative electrode of the pulse power supply. The pulse power supply applies a pulse voltage between the positive and negative electrodes thereof. The tool electrode moves in a preset direction, and the preheated target workpiece is subjected to electrospark machining under the action of the cooling component and the cold dielectric.

[0012] In a possible implementation, the cooling component is covered on the surface of the tool electrode, and the distance between the cooling component and the discharge end of the tool electrode is 1-50 mm.

[0013] In a possible implementation, the preheating temperature ranges from 20°C to 500°C.

[0014] In a possible implementation, the preheating temperature is 350°C.

[0015] In a possible implementation, the temperature range of the cold dielectric is -20°C to 10°C.

[0016] In a possible implementation, the temperature of the cold dielectric is -15°C.

[0017] In a possible implementation, the cooling temperature of the discharge end of the tool electrode ranges from -100°C to 10°C.

[0018] In a possible implementation manner, the interior of the tool electrode is hollow, and the cold dielectric is released from the interior of the tool electrode to the discharge end of the tool electrode.

[0019] The present invention also provides an electrospark machining device for executing the electrospark machining method as described above, comprising:

[0020] A heating platform, used for carrying and preheating the target workpiece after pretreatment;

[0021] A heating device controller connected to the heating platform, used to control the heating platform;

[0022] Tool electrodes, used to achieve EDM;

[0023] A machine tool fixture, used for fixing the tool electrode;

[0024] A cooling component provided on the tool electrode, used for cooling the tool electrode;

[0025] An electrode cooling temperature control system connected to the cooling component, used to control the cooling component;

[0026] A patch temperature sensor connected to the electrode cooling temperature control system and disposed close to the discharge end of the tool electrode, for providing the temperature of the discharge end of the tool electrode to the electrode cooling temperature control system;

[0027] Compressed gas device, used to provide compressed gas.

[0028] In a possible implementation, in an electric spark machining device, the interior of the tool electrode is hollow, and the cold dielectric is released from the interior of the tool electrode to a discharge end of the tool electrode.

[0029] The technical solution provided by the present invention has at least the following beneficial effects:

[0030] By cooling the tool electrode during the EDM process through a cooling component covered on the surface of the tool electrode, the heat dissipation capacity of the tool electrode can be improved and the electrode loss can be reduced; by providing a cold dielectric that accelerates the solidification of the molten metal during discharge, the discharge gap can be reduced and the machining accuracy can be guaranteed; by preheating the target workpiece, the target workpiece can be prevented from being affected by the change in temperature due to the influence of the cold tool electrode and the cold dielectric, which can affect the surface machining quality, ensure that more discharge energy is used for melting and etching of excess material during pulse discharge, and improve the energy utilization rate of pulse discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A flow chart of an electrospark machining method provided by an embodiment of the present invention;

[0032] Figure 2 A schematic structural diagram of a first electrospark machining device provided by an embodiment of the present invention;

[0033] Figure 3 A cross-sectional view of a tool electrode with a hollow interior provided by an embodiment of the present invention when releasing a cold dielectric;

[0034] Figure 4 A cross-sectional view of a tool electrode with a hollow interior provided by an embodiment of the present invention when cold dielectric is not released;

[0035] Figure 5 A schematic structural diagram of a second electrospark machining device provided by an embodiment of the present invention;

[0036] In the accompanying drawings, 10, target workpiece; 11, heating platform; 12, cooling component; 13, tool electrode; 14, machine tool fixture; 15, cold dielectric; 16, pulse power supply; 17, heating device controller; 18, electrode cooling temperature control system; 19, chip temperature sensor; 20, compressed gas device; 21, retractable hose; 22, temperature sensor; 23, sealing device; 24, servo motor. DETAILED DESCRIPTION

[0037] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0038] Please refer to Figures 1 to 5 The present invention provides an electrospark machining method, comprising the following specific steps:

[0039] S100 : pre-treating a target workpiece 10 and placing the target workpiece 10 on a heating platform 11 .

[0040] In this embodiment, the target workpiece 10 is a conventional workpiece to be processed. Preprocessing the target workpiece 10 mainly includes preprocessing the surface of the workpiece, using conventional operations. The heating platform 11 can use a conventional device for preheating the workpiece. The heating platform 11 is connected to the heating device controller 17. The maximum temperature of the discharge end of the tool electrode 13 is preset in the electrode cooling temperature control system 18, for example, it can be set to -15°C.

[0041] S200 : Mounting the tool electrode 13 provided with the cooling component 12 on the machine tool fixture 14 , and adjusting the gap between the tool electrode 13 and the target workpiece 10 .

[0042] In this embodiment, the cooling component 12 cools the entire tool electrode 13 through the heat conduction effect, which can further reduce the loss of the tool electrode 13, especially the loss of the sharp electrode, which can ensure the stability of the EDM forming process, improve the process index, increase the service life of the electrode, and reduce the processing cost. The tool electrode 13 is equivalent to a cold electrode under the cooling effect of the cooling component 12. The cold electrode can reduce the discharge gap, improve the processing accuracy, and improve the surface processing quality of the workpiece. Figure 3 , the distance l between the cooling component 12 and the discharge end of the tool electrode 13 can be set to 25 mm, or other suitable distances.

[0043] In a possible implementation, the cooling component 12 is covered on the surface of the tool electrode 13, and the distance l between the cooling component 12 and the discharge end of the tool electrode 13 is 1-50 mm.

[0044] In this embodiment, by controlling the appropriate distance from the cooling component 12 to the discharge end of the tool electrode 13, the tool electrode 13 can be effectively and continuously cooled, which helps to dissipate heat between electrodes, ensures smooth transfer of the discharge point, and reduces the probability of arc discharge.

[0045] S300: preheating the target workpiece 10 to a preheating temperature.

[0046] In this embodiment, the target workpiece 10 is preheated by the heating device controller 17 and the heating platform 11, and the preheating temperature can be 350°C or other suitable temperatures. The energy released by the pulse power supply 16 on the target workpiece 10 through pulse discharge is mainly distributed in the two stages of heating and melting and etching. By preheating the target workpiece 10 through the heating device, more energy in the pulse discharge can be allocated to the melting and etching stage of the processed workpiece, reducing energy loss, accelerating the etching speed, and improving the etching rate. Preheating the target workpiece 10 can also better control the heat distribution and avoid electric sparks causing thermal stress microcracks or other unexpected thermal damage to the target workpiece 10.

[0047] In a possible implementation, the preheating temperature ranges from 20°C to 500°C.

[0048] In this embodiment, the preheating temperature can be determined according to actual implementation needs.

[0049] In a possible implementation, the preheating temperature is 350°C.

[0050] S400 : releasing low-temperature compressed gas as a cold dielectric 15 toward the discharge end of the tool electrode 13 .

[0051] In this embodiment, the compressed gas can be a mixed gas of one or more of air, nitrogen, oxygen, argon, and carbon dioxide, and its temperature range is -20°C to 10°C. Compressed gas is used as a cold discharge medium, namely, a cold dielectric 15, which can reduce the discharge gap and improve the processing accuracy. It is also beneficial to protect the processing surface, reduce damage, and improve the surface processing quality of the workpiece. The fluid dynamic characteristics of the cold dielectric 15 can effectively discharge molten metal particles from the processing area to keep the processing area clean. When releasing the cold dielectric 15, it is necessary to stabilize the output and control the temperature change in the processing area to avoid burning on the surface of the workpiece material and ensure the uniformity of the processing quality. The release amount of low-temperature compressed gas can be determined according to the temperature sensor 22 to ensure that the temperature of the cold dielectric 15 meets the requirements. In a specific embodiment, the temperature of the compressed gas is -15°C, and it is supplied to the hollow interior of the tool electrode 13 through the compressed gas device 20, and is released as the cold dielectric 15 (such as Figure 2In another specific embodiment, the temperature of the compressed gas is -15°C, and the compressed gas device 20 is directly released at the side of the processing gap as the cold dielectric 15 (such as Figure 5 ).

[0052] In a possible implementation, the temperature range of the cold dielectric 15 is -20°C to 10°C.

[0053] In a possible implementation, the temperature of the cold dielectric 15 is -15°C.

[0054] In a possible implementation, the cooling temperature of the discharge end of the tool electrode 13 ranges from -100°C to 10°C.

[0055] In one possible implementation, Figure 2 , 3 4. The interior of the tool electrode 13 is hollow, and the cold dielectric 15 is released from the interior of the tool electrode 13 to the discharge end of the tool electrode 13 .

[0056] In the present embodiment, the cold dielectric 15 is supplied from the hollow interior of the tool electrode 13 .

[0057] S500: The target workpiece 10 is connected to the positive electrode of the pulse power supply 16, and the tool electrode 13 is connected to the negative electrode of the pulse power supply 16. The pulse power supply 16 applies a pulse voltage between its positive and negative electrodes. The tool electrode 13 moves in a preset direction, and the preheated target workpiece 10 is subjected to electrospark machining under the action of the cooling component 12 and the cold dielectric 15.

[0058] In this embodiment, the pulse power supply 16 adopts conventional settings. In specific implementation, the material of the target workpiece 10 can be TC4 titanium alloy with a size of 30mm×20mm×10mm. The tool electrode 13 is cast from red copper. The pulse voltage of the pulse power supply 16 is 27V, the pulse width is 85μs, and the pulse interval is 75μs. In specific operation, the servo motor 24 drives the tool electrode 13 to feed at a stable speed through the machine tool fixture 14 until the workpiece is processed.

[0059] In a specific embodiment, the tool electrode 13 is hollow inside, has an outer diameter of 5 mm, an inner diameter of 1.5 mm, and a length of 100 mm. During specific operation, the tool electrode 13 moves horizontally at a certain speed to process the target workpiece 10. For example: Figure 2 The servo motor 24 drives the machine tool fixture 14, the sealing device 23, and the tool electrode 13 to move horizontally to the left as a whole.

[0060] In another specific embodiment, the tool electrode 13 is a conventional solid common tool electrode with a rotation speed of 125 r / min, a diameter of 5 mm, and a length of 100 mm. During specific operation, the tool electrode 13 rotates at a certain speed and moves horizontally to process the target workpiece 10. For example: Figure 5 The servo motor 24 drives the machine tool fixture 14, the sealing device 23, and the tool electrode 13 to rotate as a whole and move horizontally to the left.

[0061] like Figures 2 to 5 The present invention also provides an electrospark machining device for executing the electrospark machining method as described above, comprising:

[0062] A heating platform 11, used for carrying and preheating the pretreated target workpiece 10;

[0063] A heating device controller 17 connected to the heating platform 11, used to control the heating platform 11;

[0064] A tool electrode 13, used for performing electrical discharge machining;

[0065] A machine tool fixture 14, used for fixing the tool electrode 13;

[0066] A cooling component 12 disposed on the tool electrode 13, used for cooling the tool electrode 13;

[0067] An electrode cooling temperature control system 18 connected to the cooling component 12, used to control the cooling component 12;

[0068] A patch temperature sensor 19 connected to the electrode cooling temperature control system 18 and disposed close to the discharge end of the tool electrode 13, for providing the electrode cooling temperature control system 18 with the temperature of the discharge end of the tool electrode 13;

[0069] The compressed gas device 20 is used to provide compressed gas.

[0070] In this embodiment, the compressed gas device 20 can provide the cold dielectric 15 through the retractable hose 21, and the retractable hose 21 can be provided with a temperature sensor 22 for monitoring the temperature of the output compressed gas. A sealing device 23 can be provided at the connection between the tool electrode 13 and the machine tool fixture 14. The machine tool fixture 14 is connected to the servo motor 24.

[0071] In the specific implementation, a heating device (i.e., a heating platform 11 and a heating device controller 17) is used to preheat the target workpiece 10, so that the target workpiece 10 is kept at room temperature or a higher temperature, ensuring that more discharge energy is used for melting and etching of excess materials during pulse discharge. During the electrospark machining process, the temperature of the discharge end of the tool electrode 13 detected by the patch temperature sensor 19 is used as the basis, and the cooling component 12 covered on the surface of the tool electrode 13 is controlled by the electrode cooling temperature control system 18 to cool and control the temperature of the tool electrode 13 to achieve the expected temperature range that meets the machining requirements. If the patch temperature sensor 19 detects that the temperature of the discharge end of the tool electrode 13 exceeds the preset range, the machine tool stops machining until the temperature drops to the preset range. Compressed gas is introduced into the machining gap through the compressed gas device 20 as a cold discharge medium, i.e., a cold dielectric 15, which accelerates the solidification of the discharge molten metal, promotes inter-electrode heat dissipation, and smoothly transfers the discharge point, which can reduce the probability of arc discharge.

[0072] In a possible implementation, in an electric spark machining device, the interior of the tool electrode 13 is hollow, and the cold dielectric 15 is released from the interior of the tool electrode 13 to the discharge end of the tool electrode 13 .

[0073] The EDM device of the present invention is easy to build and implement. A cooling component 12, a compressed gas device 20 for outputting cold dielectric 15, a heating platform 11, etc. are added to the original EDM equipment, and corresponding detection devices are provided. After proper adjustment, it can be operated, and the economic benefits are good.

[0074] The application scope of the technical solution in the present invention includes but is not limited to electric spark milling and electric spark forming, with good processing stability, high processing efficiency, greatly reducing electrode loss, especially for sharp small electrodes, reducing the probability of workpiece burns to a certain extent, and improving economic benefits. Compared with traditional electric spark machining, the present invention can achieve a smaller discharge gap, improve the utilization rate of pulse discharge, help reduce electrode loss, improve machining accuracy, accelerate the erosion rate of workpieces, ensure machining stability, and guarantee the surface quality of workpieces after machining.

[0075] The above embodiments should not limit the present invention in any way, and any technical solutions obtained by equivalent replacement or equivalent conversion shall fall within the protection scope of the present invention.

Claims

1. An electrospark machining method, characterized in that: The specific steps include: Pre-treating a target workpiece and placing the target workpiece on a heating platform; Mounting a tool electrode provided with a cooling component on a machine tool fixture, and adjusting a gap between the tool electrode and the target workpiece; preheating the target workpiece to a preheating temperature; releasing low-temperature compressed gas as a cold dielectric to the discharge end of the tool electrode; The target workpiece is connected to the positive electrode of a pulse power supply, and the tool electrode is connected to the negative electrode of the pulse power supply. The pulse power supply applies a pulse voltage between the positive and negative electrodes thereof. The tool electrode moves in a preset direction, and the preheated target workpiece is subjected to electrospark machining under the action of the cooling component and the cold dielectric.

2. The electrospark machining method according to claim 1, characterized in that: The cooling component is covered on the surface of the tool electrode, and the distance between the cooling component and the discharge end of the tool electrode is 1-50 mm.

3. The electrospark machining method according to claim 1, characterized in that: The preheating temperature ranges from 20°C to 500°C.

4. The electrospark machining method according to claim 3, characterized in that: The preheating temperature is 350°C.

5. The electrospark machining method according to claim 1, characterized in that: The temperature range of the cold dielectric is -20°C to 10°C.

6. The electrospark machining method according to claim 5, characterized in that: The temperature of the cold dielectric is -15°C.

7. The electrospark machining method according to claim 1, characterized in that: The cooling temperature of the discharge end of the tool electrode ranges from -100°C to 10°C.

8. The electrospark machining method according to claim 1, characterized in that: The interior of the tool electrode is hollow, and the cold dielectric is discharged from the interior of the tool electrode to the discharge end of the tool electrode.

9. An electrospark machining device, characterized in that: A method for performing an electrospark machining method according to any one of claims 1 to 8, comprising: A heating platform, used for carrying and preheating the target workpiece after pretreatment; A heating device controller connected to the heating platform, used to control the heating platform; Tool electrodes, used to achieve EDM; A machine tool fixture, used for fixing the tool electrode; A cooling component provided on the tool electrode, used for cooling the tool electrode; An electrode cooling temperature control system connected to the cooling component, used to control the cooling component; A patch temperature sensor connected to the electrode cooling temperature control system and disposed close to the discharge end of the tool electrode, for providing the temperature of the discharge end of the tool electrode to the electrode cooling temperature control system; Compressed gas device, used to provide compressed gas.

10. The electric spark machining device according to claim 9, characterized in that: The interior of the tool electrode is hollow, and the cold dielectric is discharged from the interior of the tool electrode to the discharge end of the tool electrode.

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