Molten metal membrane electrode electric spark machining system and method

Abstract

The invention discloses a molten metal membrane electrode electric spark machining system and method.The system comprises a pulse power source, a molten metal membrane electrode, a liquid supply system and a liquid membrane control system, the molten metal membrane electrode comprises a carrier, and the surface of the carrier is covered with a molten metal membrane layer to serve as a liquid membrane electrode for discharging; the liquid film control system is used for controlling the liquid supply system to supply liquid to the carrier so as to control the shape of the metal liquid film layer; during working, one pole of the pulse power supply is electrically connected with the metal liquid film layer, and the other pole of the pulse power supply is electrically connected with a workpiece to be machined. Compared with the prior art, frequent electrode replacement or off-line compensation in the electric spark machining process can be avoided, and then the machining efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of electrospark machining, and in particular to an electrospark machining system and method for a metal liquid film electrode. Background Art

[0002] Electrospark machining is a kind of special machining. It is a non-contact machining method that mainly uses the etching effect of the high temperature generated by the instantaneous discharge of electric sparks for machining. It does not require a tool with a complex structure, and has the advantage of small macroscopic machining force. It has great advantages in machining parts with special materials, small size, and precise structure, and has been widely used in industrial production. Traditional electrospark machining mostly uses materials such as graphite and copper as tool electrodes, but in the process of heat removal of the workpiece material, the surface of the tool electrode will also be etched by the electric spark, resulting in electrode loss, affecting the efficiency and quality of machining. In terms of electrode loss, the early method was to gain experience through a large number of process practices, on the one hand, to explore machining conditions with low electrode loss, and on the other hand, to immediately replace a new tool electrode after each stage of machining is completed. These methods can only reduce the roughness of the machined workpiece to a certain extent, and the impact on fine parts is still very large, and frequent startup and shutdown also greatly reduces the machining efficiency.

[0003] In order to solve the defects of EDM in this aspect, domestic and foreign scholars have done a lot of research and attempts. Zhou Tianfeng et al. proposed an automated electrode wear evaluation method (IS-3DR) integrating image segmentation and three-dimensional registration, which accurately evaluates electrode wear through image recognition and three-dimensional point cloud registration, and improves the accuracy of electrode compensation. In order to reduce the electrode loss in the process of fine spark machining, Gou Junfeng et al. adopted spiral motion of electrode, increased the side clearance and introduced fixed reference axial compensation (FRAC), so as to monitor the electrode wear in real time and perform axial compensation. Bai Jicheng, Zheng Chunhua et al. of Harbin Institute of Technology proposed a method of using radial basis function (RBF) network to construct a mathematical model of electrode loss to predict the amount of electrode loss for compensation. Although EDM improves the machining efficiency when machining special-shaped cavities, it will produce a large residual material column at the bottom of the workpiece, affecting the machining quality; the previous methods include electrode lifting motion, rotation motion, flushing application, etc., but these methods are not effective in non-rotating electrode forming processing. Gao Minghao and others designed a slot electrode with internal flushing, which integrates the advantages of internal flushing EDM and slot electrode EDM. By optimizing parameters such as pulse width, pulse interval and flushing pressure, the processing efficiency was improved and the electrode loss was reduced. Later, an adaptive flushing technology based on gap discharge state detection was proposed, which achieved the dual goals of high processing efficiency and low electrode wear. Some scholars have also tried to study solid electrodes with low electrode loss. Wu Bo and others designed a copper-brass-tin laminated electrode and tested it. The experimental results showed that the copper foil had a significant protective effect on brass and reduced the loss of brass.

[0004] These methods cannot fundamentally solve the problem, whether they are for accurate detection and compensation of electrode loss or for reducing electrode loss. Until a new method of processing using liquid metal electrodes was proposed, the siphon effect was used to adaptively compensate for the tool electrode loss during the discharge process. It does not require the establishment of a complex wear model, nor does it require equipment to detect electrode loss. It is more convenient and has considerable advantages over traditional methods. Zhu Erlei studied the analysis of the influence of electric field force and surface tension on the shape of the end of liquid metal as an electrode in a capillary, and conducted experiments to find factors that affect the processing accuracy of liquid metal electrodes. It was found that reducing voltage, reducing capacitance, and increasing resistance within a certain range can improve the processing accuracy of liquid metal electrodes. Huang Ruining and others from the Shenzhen Graduate School of Harbin Institute of Technology proposed an electric field-controlled liquid metal electrode electrospark processing method, such as Figure 1 However, the electrode size of this method is limited by the capillary, and the electrode morphology control is complex, which is not convenient for engineering applications. Summary of the invention

[0005] The main purpose of the present invention is to provide a metal liquid film electrode electrospark machining system and method, aiming to avoid frequent electrode replacement or off-line compensation during electrospark machining and improve machining efficiency.

[0006] To achieve the above-mentioned object, the present invention provides a metal liquid film electrode electrospark machining system, comprising: a pulse power supply, a metal liquid film electrode, a liquid supply system and a liquid film control system, wherein the metal liquid film electrode comprises a carrier, the surface of the carrier is covered with a metal liquid film layer as a liquid film electrode for discharge, and the liquid film control system is used to control the liquid supply system to supply liquid to the carrier to control the shape of the metal liquid film layer;

[0007] During operation, one pole of the pulse power supply is electrically connected to the metal liquid film layer, and the other pole is electrically connected to the workpiece to be processed.

[0008] A further technical solution of the present invention is that a layer of gallium, indium or tin metal is plated on the surface of the carrier, and the metal liquid film layer covers the gallium, indium or tin metal.

[0009] A further technical solution of the present invention is that it further comprises a discharge medium and a container for containing the discharge medium. During operation, the workpiece and the carrier are relatively immersed in the discharge medium.

[0010] A further technical solution of the present invention is that the discharge medium is spark machine oil.

[0011] A further technical solution of the present invention is that it also includes a flushing system for flushing metal chips on the workpiece.

[0012] A further technical solution of the present invention is that the carrier is a porous carrier, and a plurality of through holes are arranged on the surface of the carrier. After the liquid metal is injected into the porous carrier, it seeps out through the plurality of through holes to form the metal liquid film layer.

[0013] A further technical solution of the present invention is that the carrier is fixed on a fixing device, and the fixing device is provided with a plurality of edge pores, and the liquid metal flows from the plurality of edge pores along the outer wall of the carrier to the bottom to form the metal liquid film layer.

[0014] A further technical solution of the present invention is that it also includes a numerically controlled motion platform, wherein a clamp for clamping the carrier is arranged on the top of the numerically controlled motion platform, and a workbench is arranged on the bottom.

[0015] A further technical solution of the present invention is that the pulse power supply is a transistor controllable pulse power supply or a resistor-capacitor pulse power supply.

[0016] To achieve the above object, the present invention further provides a method for electrospark machining of a metal liquid film electrode, the method comprising the following steps:

[0017] Step S10, constructing an experimental platform, wherein the experimental platform includes the metal liquid film electrode electrospark machining system as described above.

[0018] Step S20, starting the pulse power supply, and performing discharge machining when the pulse power supply reaches a high level and the discharge conditions are met between the electrodes. During the machining process, the carrier is supplied with liquid through a liquid supply system to control the shape of the metal liquid film layer.

[0019] The beneficial effects of the metal liquid film electrode electrospark machining system and method of the present invention are:

[0020] The metal liquid film electrode is composed of a carrier and a metal liquid film layer. Usually, the carrier itself is insulated and does not participate in the discharge. Therefore, as long as the metal liquid film layer can be continuously formed, the shape of the metal liquid film electrode will not change, which can effectively solve the problem of solid electrode loss affecting processing accuracy and processing efficiency. Under the action of the liquid supply system and the liquid film control system, the compensation problem of liquid metal can also be well solved. In this way, there is no need to frequently replace electrodes or compensate offline during the processing process, nor is there any need to monitor the processing process online and compensate in real time. Compared with capillary liquid phase electrodes, metal liquid film electrodes can be used in processing applications that require high efficiency, and liquid film electrodes of different shapes can be produced by changing the specifications and shapes of porous carriers to serve different processing needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of a liquid metal electrode processing method in the prior art;

[0023] Figure 2 It is a structural block diagram of the metal liquid film electrode electrospark machining system of the present invention;

[0024] Figure 3 It is a schematic diagram of the metal liquid film electrode processing method;

[0025] Figure 4 It is a schematic diagram of the metal liquid film electrode processing process;

[0026] Figure 5 This is a schematic diagram of the first formation scheme of the metal liquid film electrode;

[0027] Figure 6 This is a schematic diagram of the second formation scheme of the metal liquid film electrode;

[0028] Figure 7 It is a top view of the second formation scheme of the metal liquid film electrode;

[0029] Figure 8 This is a schematic diagram of the third formation scheme of the metal liquid film electrode;

[0030] Fig. 9 It is a flow chart of a preferred embodiment of the metal liquid film electrode electrospark machining method of the present invention.

[0031] Description of Figure Numbers:

[0032] Pulse power supply 1; metal liquid film electrode 2; liquid supply system 3; liquid film control system 4; carrier 5; metal liquid film layer 6; spark oil 7; flushing system 8; CNC motion platform 9; clamp 10; workbench 11; liquid metal 12; fixture 13; edge pore 14; workpiece 15.

[0033] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The present invention provides a metal liquid film electrode 2 electrospark machining system, such as Figures 2 to 8 As shown, a preferred embodiment of the electrospark machining system of the metal liquid film electrode 2 of the present invention includes: a pulse power supply 1, a metal liquid film electrode 2, a liquid supply system 3 and a liquid film control system 4.

[0036] The metal liquid film electrode 2 includes a carrier 5 , the surface of which is covered with a metal liquid film layer 6 of a certain thickness as a discharge liquid film electrode. The liquid film control system 4 is used to control the liquid supply system 3 to supply liquid to the carrier 5 to control the shape of the metal liquid film layer 6 .

[0037] During operation, one electrode of the pulse power supply 1 is electrically connected to the metal liquid film layer 6 , and the other electrode is electrically connected to the workpiece 15 to be processed.

[0038] In this embodiment, the pulse power supply 1 can be a transistor-controlled pulse power supply 1 or a resistor-capacitor (RC) pulse power supply 1. When the pulse power supply 1 reaches a high level and the discharge conditions are met between the electrodes, discharge machining is performed. During the machining process, part of the workpiece 15 material will be eroded, and at the same time, the metal liquid film layer 6 will also have some loss, and the liquid film will be deformed. During the machining process, the metal liquid film layer 6 will mainly be subjected to the impact force of the spark discharge and the impact force of the flushing liquid. During this period, the thickness and shape of the metal liquid film layer 6 are maintained or compensated by the liquid film control system 4.

[0039] Furthermore, in this embodiment, a layer of gallium, indium or tin metal is plated on the surface of the carrier 5 , and the metal liquid film layer 6 covers the gallium, indium or tin metal.

[0040] In this embodiment, the metal liquid film layer 6 may be made of a conductive gallium-based alloy that is liquid at room temperature, such as a gallium-indium-tin alloy.

[0041] Since the surface tension of the liquid metal 12 is large and its wettability on the surface of most materials is poor, it is necessary to treat the surface of the carrier 5 to improve its wettability so as to form the metal liquid film layer 6. For example, the carrier 5 is immersed in the liquid metal 12 or a layer of gallium, indium or tin metal is plated on the carrier 5 before processing.

[0042] Furthermore, in this embodiment, the metal liquid film electrode 2 EDM system further includes a discharge medium and a container for containing the discharge medium. During operation, the workpiece 15 and the carrier 5 are relatively immersed in the discharge medium.

[0043] Furthermore, in this embodiment, the discharge medium is spark oil 7.

[0044] It is worth mentioning that, as an implementation scheme, air can also be used as a discharge medium, but when air is used as the discharge medium, the distance between the carrier 5 and the workpiece 15 needs to be close to perform EDM on the workpiece 15, and the adjustment accuracy is high when adjusting the distance between the carrier 5 and the workpiece 15. However, this embodiment uses spark machine oil 7 as the discharge medium, and the distance requirement for the carrier 5 and the workpiece 15 is relatively low, and they can be farther apart. Under this condition, the adjustment accuracy of the distance between the carrier 5 and the workpiece 15 is relatively low, which is more convenient for EDM.

[0045] Furthermore, in this embodiment, the metal liquid film electrode 2 electrospark machining system also includes a flushing system 8 for flushing metal chips on the workpiece 15 .

[0046] During the EDM process, the material of the workpiece 15 is removed by discharge to form a groove. The flushing system 8 is used to remove the waste material and the consumed liquid metal 12 remaining in the groove through flushing liquid so as to proceed to the next step of discharge.

[0047] In this embodiment, the liquid metal may be a conductive gallium-based alloy that is liquid at room temperature, such as a gallium-indium-tin alloy. The metal liquid film electrode 2 may be formed by the following methods:

[0048] 1. If Figure 5 As shown, the carrier 5 is a porous carrier 5. As an embodiment, the porous carrier 5 can be set as a hollow structure, and a plurality of through holes are set on the surface of the carrier 5. After the liquid metal 12 is injected into the porous carrier 5, it seeps out through the plurality of through holes to form a metal liquid film layer 6 on the bottom and side surfaces. In other embodiments, the interior of the porous carrier 5 can also be set as other structures, such as a honeycomb structure, to ensure that it can accommodate the liquid metal. Figure 3 As shown, in the electrospark machining system of the metal liquid film electrode 2 based on the porous carrier 5, the metal liquid film electrode 2 is compensated by automatically controlling the pressure pump, and the formation of the metal liquid film can also be controlled by an external electromagnetic field. The liquid metal is stored in the liquid storage tank. The liquid supply system 3 uses a precision pressure device to drive the supply of liquid metal 12.

[0049] 2. If Figure 6 and Figure 7 As shown, the carrier 5 is fixed on the fixing device 13, the fixing device 13 and the carrier 5 are in a T shape, the fixing device 13 is distributed with a plurality of edge pores 14, and the liquid metal 12 flows from the plurality of edge pores 14 along the outer wall of the carrier 5 to the bottom to form a metal liquid film layer 6. As an embodiment, the cross section of the fixing device 13 and the carrier 5 can be set to a T-shaped structure.

[0050] 3. If Figure 8 As shown, the bottom of the carrier 5 is extended into the liquid metal 12, and a layer of metal liquid film 6 is formed on the bottom when the carrier 5 is lifted.

[0051] Furthermore, in this embodiment, the electrospark machining system for the metal liquid film electrode 2 further includes a numerical control motion platform 9 , a clamp 10 for clamping the carrier 5 is disposed on the top of the numerical control motion platform 9 , and a workbench 11 is disposed on the bottom.

[0052] The working process of the metal liquid film electrode 2 EDM system of the present invention is as follows:

[0053] 1. Experimental platform construction: Based on the high-precision CNC motion platform 9, build Figure 3 The metal liquid film electrode 2 electrospark machining system shown;

[0054] 2. EDM process: When the pulse power supply 1 reaches a high level and the discharge conditions are met between the electrodes, discharge machining is performed. At this stage, part of the workpiece 15 material will be eroded, and the liquid metal 12 will also be partially lost, and the metal liquid film layer 6 will be deformed. During the machining process, the metal liquid film layer 6 will mainly be subjected to the impact force of the spark discharge and the impact force of the flushing liquid. During this period, a controllable pressure pump or a controllable external electromagnetic field is required to maintain the shape. The waste material and the lost liquid metal 12 remaining in the groove of the workpiece 15 will be taken away by the flushing liquid for the next discharge. At the same time, the liquid supply system 3 accurately replenishes the liquid metal 12 in the cavity of the porous carrier 5. This process is repeated to form continuous discharge machining.

[0055] The beneficial effects of the metal liquid film electrode electrospark machining system of the present invention are:

[0056] The metal liquid film electrode is composed of a carrier and a metal liquid film layer. Usually, the carrier itself is insulated and does not participate in the discharge. Therefore, as long as the metal liquid film layer can be continuously formed, the shape of the metal liquid film electrode will not change, which can effectively solve the problem of solid electrode loss affecting processing accuracy and processing efficiency. Under the action of the liquid supply system and the liquid film control system, the compensation problem of liquid metal can also be well solved. In this way, there is no need to frequently replace electrodes or compensate offline during the processing process, nor is there any need to monitor the processing process online and compensate in real time. Compared with capillary liquid phase electrodes, metal liquid film electrodes can be used in processing applications that require high efficiency, and liquid film electrodes of different shapes can be produced by changing the specifications and shapes of porous carriers to serve different processing needs.

[0057] To achieve the above object, the present invention also provides a method for electrospark machining of a metal liquid film electrode, such as Fig. 9 As shown, the method comprises the following steps:

[0058] Step S10, constructing an experimental platform, which includes the metal liquid film electrode electrospark machining system as described above.

[0059] In step S10, a metal liquid film electrode EDM system is constructed based on a high-precision CNC motion platform.

[0060] Step S20, starting the pulse power supply, when the pulse power supply reaches a high level and the discharge conditions are met between the electrodes, discharge machining is performed. During the machining process, the liquid supply system supplies liquid to the carrier to control the shape of the metal liquid film layer.

[0061] Step S20 involves the EDM process: when the pulse power supply reaches a high level and the discharge conditions are met between the electrodes, EDM is performed. At this stage, part of the workpiece material will be eroded, and the liquid metal will also be partially lost, and the metal liquid film layer will be deformed. During the machining process, the metal liquid film layer will mainly be subjected to the impact force of the spark discharge and the impact force of the flushing liquid. During this period, a controllable pressure pump or a controllable external electromagnetic field is required to maintain the shape. The waste material and the lost liquid metal remaining in the groove of the workpiece will be taken away by the flushing liquid for the next discharge. At the same time, the liquid supply system accurately replenishes the liquid metal in the porous carrier cavity. This process is repeated to form continuous EDM.

[0062] The beneficial effects of the metal liquid film electrode electrospark machining method of the present invention are:

[0063] The metal liquid film electrode is composed of a carrier and a metal liquid film layer. Usually, the carrier itself is insulated and does not participate in the discharge. Therefore, as long as the metal liquid film layer can be continuously formed, the shape of the metal liquid film electrode will not change, which can effectively solve the problem of solid electrode loss affecting processing accuracy and processing efficiency. Under the action of the liquid supply system and the liquid film control system, the compensation problem of liquid metal can also be well solved. In this way, there is no need to frequently replace electrodes or compensate offline during the processing process, nor is there any need to monitor the processing process online and compensate in real time. Compared with capillary liquid phase electrodes, metal liquid film electrodes can be used in processing applications that require high efficiency, and liquid film electrodes of different shapes can be produced by changing the specifications and shapes of porous carriers to serve different processing needs.

[0064] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A metal liquid film electrode electrospark machining system, characterized in that: include: A pulse power supply, a metal liquid film electrode, a liquid supply system and a liquid film control system, wherein the metal liquid film electrode comprises a carrier, the surface of the carrier is covered with a metal liquid film layer as a discharge liquid film electrode, and the liquid film control system is used to control the liquid supply system to supply liquid to the carrier to control the shape of the metal liquid film layer; During operation, one pole of the pulse power supply is electrically connected to the metal liquid film layer, and the other pole is electrically connected to the workpiece to be processed.

2. The metal liquid film electrode electrospark machining system according to claim 1, characterized in that: A layer of gallium, indium or tin metal is plated on the surface of the carrier, and the metal liquid film layer covers the gallium, indium or tin metal.

3. The metal liquid film electrode EDM system according to claim 1, characterized in that: It also includes a discharge medium and a container for containing the discharge medium. During operation, the workpiece and the carrier are relatively immersed in the discharge medium.

4. The metal liquid film electrode EDM system according to claim 3, characterized in that: The discharge medium is spark oil.

5. The metal liquid film electrode EDM system according to claim 3, characterized in that: Also included is a flushing system for flushing metal chips from the workpiece.

6. The metal liquid film electrode EDM system according to claim 1, characterized in that: The carrier is a porous carrier, and a plurality of through holes are arranged on the surface of the carrier. After the liquid metal is injected into the porous carrier, it seeps out through the plurality of through holes to form the metal liquid film layer.

7. The liquid film electrode EDM system according to claim 1, characterized in that: The carrier is fixed on a fixing device, and the fixing device is distributed with a plurality of edge holes. Liquid metal flows from the plurality of edge holes along the outer wall of the carrier to the bottom to form the metal liquid film layer.

8. The metal liquid film electrode electrospark machining system according to any one of claims 1 to 7, characterized in that: It also includes a numerical control motion platform, the top of which is provided with a clamp for clamping the carrier, and the bottom of which is provided with a workbench.

9. The metal liquid film electrode electrospark machining system according to any one of claims 1 to 7, characterized in that: The pulse power supply is a transistor controllable pulse power supply or a resistor-capacitor pulse power supply.

10. A method for electrospark machining of metal liquid film electrodes, characterized in that: The method comprises the following steps: Step S10, building an experimental platform, wherein the experimental platform includes the metal liquid film electrode electrospark machining system according to any one of claims 1 to 9. Step S20, starting the pulse power supply, and performing discharge machining when the pulse power supply reaches a high level and the discharge conditions are met between the electrodes. During the machining process, the carrier is supplied with liquid through a liquid supply system to control the shape of the metal liquid film layer.

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