Flexible braided electrode and method for electrochemical polishing of complex inner channel

Abstract

The invention provides a flexible braided electrode and an electrochemical polishing method for a complex inner channel, and belongs to the technical field of electrochemical machining. The flexible braided electrode is formed by mutually braiding a plurality of flexible conductive wires and a plurality of flexible insulating wires according to a certain interval, the diameter of the insulating wires is larger than that of the conductive wires, and steps with a certain height are naturally formed between the insulating wires and the conductive wires, so that short-circuit burn caused by contact between the conductive metal wires and an inner channel can be avoided, mass transfer can be enhanced, and product discharge can be accelerated; the flexible woven electrode is of a hollow net-shaped cylindrical structure, internal and external compound flushing can be achieved, and the flushing effect is improved. During polishing, the flexible braided electrode can be bent and deformed in a bent inner channel in a self-adaptive manner, internal and external compound flushing is performed by utilizing the internal and external through characteristic, and electrochemical polishing of the complex inner channel is realized by combining rotation and reciprocating motion of the electrode. The invention provides the flexible braided electrode with ingenious conception, and the flexible braided electrode is supplemented with an innovative process method, so that high-efficiency and high-quality finishing of a complex inner channel can be realized.

Description

Technical Field

[0001] The invention relates to a flexible braided electrode and a method for electrochemical polishing a complex inner channel, belonging to the technical field of electrolytic processing. Background Art

[0002] Additive manufacturing technology is a technology that uses lasers and other methods to heat and melt materials based on models made with computer-aided design software, and then stacks them point by point, line by line, and layer by layer to form complete parts or components. This technology has a high degree of flexibility, a short manufacturing cycle, and greatly reduces material waste. Therefore, it is widely used in aerospace manufacturing, medical personalized human implants, chemical catalysis and other fields. At the same time, the flexibility and efficiency of additive manufacturing technology make it widely used in the production of workpieces with complex internal channel structures.

[0003] However, due to the problems of spheroidization effect, powder adhesion, step effect and so on in additive manufacturing technology, the surface of the machined parts is rough and has a large number of raised structures, which makes it difficult to meet the technical requirements of aerospace and other fields, and requires post-finishing processing. Especially for complex internal channels, the internal channel visibility is poor and the tool operation is inconvenient, making post-finishing processing difficult. How to perform finishing processing on workpieces with complex curved internal channels is a problem that currently plagues manufacturing.

[0004] At present, the common polishing processes for additively manufactured parts at home and abroad include mechanical polishing, laser polishing, abrasive flow polishing, and chemical polishing. Among these polishing technologies, mechanical polishing is the most widely used, and it has significant advantages in terms of material removal efficiency and surface quality after processing. However, mechanical polishing has many processing steps, poor tool accessibility, and cannot effectively finish the complex internal channels; during laser polishing, local heating of the workpiece in a short period of time may cause deformation or cracks of the workpiece, and the laser beam is difficult to cope with the complex internal channels; after abrasive flow polishing, abrasive particles may remain on the surface of the workpiece, and the abrasive particles in the internal channels are more difficult to discharge, making it difficult to accurately control the surface roughness of the workpiece.

[0005] As a non-contact processing method, the electrochemical polishing method is not limited by the mechanical properties of the material. It mainly relies on the dissolution of the anode during the electrochemical reaction to achieve the purpose of material removal. This method has the advantages of strong flexibility and good processing effect, and can better realize the finishing processing of complex internal channels.

[0006] In the patent "Flexible wire electrode assembly and method for composite polishing of the inner surface of a tiny metal flow channel" (application number 20020010932152.0 applicant Nanjing University of Aeronautics and Astronautics, inventors Zeng Yongbin, Li Yanliang, Yang Tao, Xu Zhengyang), a flexible electrode formed by spirally winding two flexible wires is proposed, and the diameter of the insulating flexible wire is larger than the conductive cathode wire, which can avoid the conductive cathode wire from contacting the inner wall and short-circuiting. In contrast, the flexible braided electrode used in the present invention has a hollow structure, which can be compositely flushed inside and outside, accelerate product discharge, improve polishing quality, and the cross-sectional shape of the flexible electrode can be adjusted to a certain extent according to the shape of the inner channel, so that it can complete the finishing of square, elliptical and other inner channels.

[0007] In the patent "Electrolytic mechanical finishing method of cathode and internal channel of traction-type flexible tool" (application number 2001810474066.2, applicant Nanjing University of Aeronautics and Astronautics, inventor Qu Ningsong, Yue Xiaokang, Fang Xiaolong, Li Hansong), a cathode tool including a cathode bolt and a flexible friction layer is proposed, which finishes the inner wall surface through the combined action of electrolysis and friction. In comparison, the flexible braided electrode structure used in the present invention is simple and light, with high polishing efficiency, and can also perform finishing processing on smaller internal channels.

[0008] In the patent "Flexible twisted cathode and its electrochemical polishing method for complex inner channels" (application number 2002210578163.2, applicant Nanjing University of Aeronautics and Astronautics, inventors Zhu Di'an, Lin Chao and Wang Dengyong), a flexible electrode twisted from two metal wires and multiple strands of non-conductive fine wires is proposed. The non-conductive fine wires evenly distributed along the circumferential direction can avoid direct contact between the tool cathode and the inner channel, preventing short circuits. In contrast, the flexible braided electrode used in the present invention has a mesh hollow structure, which can be flushed with liquid inside and outside, and the alternating braiding method naturally forms a height step between the insulating wire and the metal conductor wire, which prevents short circuits and ensures the finishing effect.

[0009] In the patent "Complex Internal Channel Reciprocating Electrolytic Grinding Composite Processing Method" (application number 20020011047082.7 applicant Nanjing University of Aeronautics and Astronautics, inventors Zhu Di, Wang Dengyong, An Linchao), a processing method for electrolytic grinding composite processing is proposed by pulling the tool assembly reciprocatingly through a hollow soft shaft, which is used for finishing the surface of a curved complex internal channel. In comparison, the flexible braided electrode used in the present invention has a simple structure, is easy to make, and can finish smaller internal channel parts.

[0010] In the patent "Flexible Electrode for Electrochemical Polishing and Electrochemical Polishing Method for Inner Cavity Structure" (application number 2002110339643.9, applicant China Academy of Engineering Physics, Mechanical Manufacturing Technology Research Institute, inventors Ye Zuoyan, Ye Minheng, Wang Lili, Pan Jinlong, Li Xiaoyuan, Wang Chao, Shen Xianfeng), a flexible electrode consisting of an insulating layer, an electrode layer and a support layer is proposed. After expansion, it can adaptively match the inner cavity structure morphology under the action of the inner wall of the workpiece for electrochemical polishing. In comparison, the present invention adopts a flow field mode of high-voltage and high-speed electrolyte flushing, and controls the cathode to perform reciprocating and rotating motions, which is more conducive to product discharge, enhances mass transfer, and ensures the finishing effect.

[0011] In the patent "Snake-shaped flexible cathode and inner channel electrochemical polishing method" (application number 202210578582.6 applicant Nanjing University of Aeronautics and Astronautics, inventors Zhu Di'an, Lin Chao and Wang Dengyong), a snake-shaped flexible cathode consisting of multiple cathode unit sections, ball joints, cathode end caps, cathode support rings and fastening bolts is proposed. In comparison, the flexible braided electrode used in the present invention is braided by multiple metal wires with smaller diameters and multiple non-metal wires with larger diameters arranged at a certain interval. It has a simple structure and is easy to make, and can be used for finishing of small-aperture inner channels.

[0012] In the patent "An Electrode Device for Electrolytic Cleaning of the Inner Flow Channel of Additively Manufactured Parts and Its Processing Method" (application number 2002310072363.5, applicant Shanghai Jiaotong University, inventor requests not to publish name), an electrode structure consisting of a front conductive electrode, a front insulating sleeve and a rear flexible electrode is provided, and the residue is removed by a rear brush. In comparison, the hollow structure of the flexible braided electrode used in the present invention can be used for internal and external composite flushing, enhance mass transfer, and improve the quality of electrolytic polishing.

[0013] In the patent "An electrolytic polishing device for the inner wall of a special-shaped microtube" (application number 2002310330372.X, applicant Taiyuan University of Technology, inventor Liang Guoxing, Bai Xuechen, Hao Xinhui, Liu Donggang, Yang Shiqing, Zhang Dongdong, and Lv Ming), a device for electrolytic polishing of the inner wall of a special-shaped microtube including an electrolyte tank, a waste liquid tank, and a reaction box is designed, and the electrolytic polishing treatment of the inner hole of the special-shaped microtube is achieved through the redirection fixed pulley and the driving device. In comparison, the flexible braided electrode used in the present invention has a simple structure, adopts an internal and external composite flushing mode and combines mechanical movement for finishing, the product can be quickly discharged with the electrolyte, and the finishing effect is good.

[0014] In the patent "Suction electrolytic machining device and method for finishing internal structures" (application number 202011451556.4 applicant Nanjing University of Aeronautics and Astronautics, inventors Tang Xiaochuan, Zhao Chenhao, Qu Ningsong), a suction electrolytic machining device with a tool cathode, an insulating layer, a clamping frame, a slider, a bolt, a sealing gasket, a liquid extraction tube, and a clamping screw is designed to achieve electrolytic finishing of the entire internal structure surface. In contrast, the flexible braided electrode used in the present invention can be curled into a circular, elliptical, or square shape according to the shape of the inner hole cross section, and can process complex inner channel surfaces with non-circular cross sections.

[0015] As can be seen from the above, the electrochemical polishing method mainly relies on the tool cathode to extend into the inner channel for electrochemical reaction. Due to the small diameter and large curvature of the inner channel, there are problems such as difficult processing of the curved part, inability to discharge the processed product in time, and short circuit between the tool cathode and the workpiece during the actual processing. Therefore, designing a flexible tool cathode with good flexibility and simple structure that can effectively realize electrochemical polishing of complex inner channels while avoiding short-circuit burns is a key issue that needs to be solved urgently. Summary of the invention

[0016] In response to the problems that the tool cathode cannot extend into the curved channel and the processed products cannot be discharged in time during electrochemical polishing of a workpiece with a complex internal channel, the present invention proposes a flexible braided electrode with good flexibility and simple structure, which can effectively realize electrochemical polishing of the complex internal channel and a method for electrochemical polishing of the complex internal channel.

[0017] A flexible braided electrode, characterized in that: a plurality of flexible insulating wires and a plurality of flexible conductive wires are alternately arranged and woven into a hollow mesh structure; wherein the diameter of the flexible insulating wires is larger than the diameter of the flexible conductive wires, and steps of a certain height are naturally formed between each other after the weaving is completed, which can not only avoid short-circuit burns caused by contact between the conductive wires and the inner channel, but also enhance mass transfer and accelerate product discharge.

[0018] The method for electrochemical polishing of complex internal channels using a flexible braided electrode is characterized in that it includes the following processes: Step 1: Fix the part to be processed on the workbench of a machine tool, and one end of the internal channel is connected to a liquid collecting chamber; Step 2: Place the flexible braided electrode along the internal channel in the part to be processed, and perform adaptive bending deformation according to the shape of the internal channel; One end of the flexible braided electrode is connected to the first spindle of the machine tool, and the other end is connected to the second spindle of the machine tool, and the spindle of the machine tool is adjusted to the initial processing position; Step 3: Connect the flexible braided electrode to the negative pole of the power supply, and the part to be processed to the positive pole of the power supply; Step 4: Turn on the liquid supply system, and a part of the electrolyte flows into the inner hole of the flexible braided electrode through the liquid supply end coaxial with the machine tool spindle, and flows into the processing gap between the flexible braided electrode and the surface of the inner channel of the part through the mesh gap formed between the flexible insulating wire and the flexible conductive wire; Another part of the electrolyte flows into the liquid collecting chamber and enters the processing gap along the outer wall of the flexible braided electrode , thereby forming an internal and external composite flushing liquid; the diameter of the insulating wire of the flexible braided electrode is larger than the diameter of the conductive wire, which avoids short-circuit burns caused by the contact between the conductive wire of the flexible braided electrode and the surface of the inner channel of the part during processing; Step 5: After the electrolyte fills the inner channel, turn on the power supply, control the machine tool spindle to perform reciprocating motion along the axial direction and rotational motion around the axis, drive the flexible braided electrode to perform reciprocating motion and rotational motion, and under the combined action of electrochemical dissolution and mechanical movement of the flexible electrode, the electrochemical dissolution of the inner channel surface of the anode workpiece to be processed is achieved, and the raised area on the surface of the inner channel is closer to the flexible braided electrode, so the electrochemical dissolution rate is higher, which has a leveling effect, and at the same time, the electrochemical reaction products and bubbles are quickly discharged under the combined action of electrolyte flushing and flexible braided electrode movement, so as to achieve electrolytic polishing of the inner channel surface of the part; Step 6: After a period of time, when the roughness of the inner channel surface of the part meets the processing requirements, stop processing.

[0019] The beneficial effects of the present invention are: 1) Provides an innovative tool electrode structure. The flexible braided electrode proposed by the present invention is a hollow mesh structure formed by alternating a number of flexible insulating wires and a number of flexible conductive wires; wherein the diameter of the flexible insulating wires is larger than the diameter of the flexible conductive wires, and after the weaving is completed, steps of a certain height are naturally formed between each other, which can not only avoid short-circuit burns caused by contact between the conductive wires and the inner channel, but also enhance mass transfer and accelerate product discharge.

[0020] 2) An innovative polishing process method is provided. When the flexible braided electrode is used for electrochemical polishing of the inner channel, the flexible braided electrode rotates around the axis and reciprocates, and at the same time, the flexible braided electrode mesh structure is used, and the internal and external composite flushing mode is adopted to enhance mass transfer, remove processing products, and improve polishing efficiency and polishing quality.

[0021] 3) It has a wide range of applications. The flexible braided electrode proposed by the present invention can change the braiding method and the degree of density, and curl along the axis into a circle, an ellipse, or a square to adapt to the polishing of complex internal channels with different cross-sectional shapes such as round holes, elliptical holes, and square holes, and has a wide range of applications.

[0022] The flexible braided electrode is characterized in that: the braiding method of the flexible braided electrode is a single-strand braided structure, that is, a single-strand flexible insulating wire and a single-strand flexible conductive wire are interlaced and woven together. The braiding method is simple and easy to manufacture.

[0023] The flexible braided electrode is characterized in that: the braiding method of the flexible braided electrode is a three-strand braided structure, that is, two flexible insulating wires and a single flexible conductive wire are braided side by side; each flexible conductive wire is adjacent to two flexible insulating wires on both sides. Each flexible conductive wire is adjacent to two insulating wires on both sides, which can better cope with the inner channel with a larger curvature and a more complex structure, avoid the point contact short circuit problem caused by the sudden change of the inner wall structure during the processing, and is conducive to ensuring the processing stability.

[0024] The flexible braided electrode is characterized in that the flexible braided electrode is a positive braided structure, that is, the braided wire direction is used as the curling axis. This structure is easy to manufacture electrodes with complex cross-sections and has low manufacturing difficulty.

[0025] The flexible braided electrode is characterized in that: the flexible braided electrode is a 45° slanted braided structure, that is, the direction of the 45° angle with the braided wire is used as the curling axis. This structure is evenly stressed when bent, has good material mechanical properties, and can cope with inner channel structures with greater bending degrees.

[0026] The flexible braided electrode is characterized in that the flexible insulating wires and the flexible conductive wires are arranged alternately in the warp direction and the weft direction. This method can ensure the rigidity of the flexible braided electrode and realize the deformation of the flexible braided electrode; in addition, this method can also prevent the conductive metal wire from contacting the inner wall of the workpiece, preventing short circuit burns.

[0027] The flexible braided electrode is characterized in that the cross-section of the flexible braided electrode is circular, elliptical, or square, which can be selected according to different processing objects, taking into account both rigidity and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The overall schematic diagram of the cathode of the flexible braided electrode; Figure 2 Schematic diagram of electrochemical polishing of complex internal channels of flexible braided electrodes; Figure 3 Flexible braided electrodes made of different braiding methods, including a single-strand positive braiding structure and a three-strand positive braiding structure; Figure 4 A schematic diagram of a positive braiding structure in which a flexible braided electrode is curled along the braiding wire direction as an axis; Figure 5 A schematic diagram of a 45° braided structure in which a flexible braided electrode is curled along a direction that is 45° from the braided wire as an axis; Figure 6 Flexible braided electrodes with different cross-sectional shapes, namely circular, elliptical, and square; The numbers in the figure are as follows: 1. Flexible braided electrode; 2. Flexible insulating wire; 3. Flexible conductive wire; 4. Parts to be processed; 5. The first spindle of the machine tool; 6. Liquid collecting chamber; 7. Surface of the channel inside the part; 8. Power supply; 9. The second spindle of the machine tool. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings.

[0030] like Figure 1~2 As shown, the flexible braided electrode electrochemical polishing complex inner channel method proposed by the present invention includes the following processes: Step 1: Fix the part 4 to be processed on the workbench of the machine tool, and connect one end of the inner channel to the liquid collecting chamber 6; Step 2: Place the flexible braided electrode 1 along the inner channel in the part to be processed 4, and perform adaptive bending deformation according to the shape of the inner channel; one end of the flexible braided electrode 1 is connected to the first spindle 5 of the machine tool, and the other end is connected to the second spindle 9 of the machine tool, and the spindle of the machine tool is adjusted to the initial processing position; Step 3: Connect the flexible braided electrode 1 to the negative pole of the power source 8, and connect the part to be processed 4 to the positive pole of the power source 8; Step 4: Turn on the liquid supply system, a part of the electrolyte flows into the inner hole of the flexible braided electrode 1 through the liquid supply end coaxial with the machine tool spindle 5, and flows into the processing gap between the flexible braided electrode 1 and the inner channel surface 7 of the part through the mesh gap formed between the flexible insulating wire 2 and the flexible conductive wire 3; another part of the electrolyte flows into the liquid collecting cavity 6, enters the processing gap along the outer wall of the flexible braided electrode 1, thereby forming an inner and outer composite flushing liquid; the diameter of the flexible braided electrode insulating wire 2 is larger than the diameter of the conductive wire 3, which avoids the contact between the flexible braided electrode conductive wire 3 and the inner channel surface 7 of the part during the processing to cause short circuit burns; Step 5: After the electrolyte fills the inner channel, the power supply 8 is turned on to control the machine tool spindle 5 to perform reciprocating motion along the axial direction and rotational motion around the axis, driving the flexible braided electrode 1 to perform reciprocating motion and rotational motion. Under the combined action of electrochemical dissolution and mechanical motion of the flexible electrode 1, the electrochemical dissolution of the inner channel surface 7 of the anode workpiece to be processed is achieved, and the raised area of ​​the inner channel surface 7 is closer to the flexible braided electrode 1, so the electrochemical dissolution rate is higher, which has a leveling effect. At the same time, the electrochemical reaction products and bubbles are quickly discharged under the combined action of electrolyte flushing and the movement of the flexible braided electrode 1, so as to achieve electrolytic polishing of the inner channel surface of the part; Step 6: After a period of time, when the roughness of the channel surface 7 inside the part reaches the processing requirement, stop processing.

[0031] like Figure 3 As shown, the flexible braided electrode proposed in the present invention can be made by interlacing a single insulating wire 2 and a single metal conductor wire 3; or it can be made by interlacing a double insulating wire 2 and a single metal conductor wire 3 side by side.

[0032] like Figure 4 , Figure 5 As shown, in terms of the curling method, the flexible braided electrode 1 of the present invention can be curled along the braiding wire direction as the axis, or along the direction with an angle of 45° to the braiding wire as the axis.

[0033] like Figure 6 As shown, the cross-sectional shape of the flexible braided electrode after curling proposed by the present invention can be determined according to the cross-sectional shape of the inner channel to be processed, so as to meet the processing requirements of inner channels of different shapes, such as round, oval, square, etc.

Claims

1. A flexible braided electrode, characterized in that: A plurality of flexible insulating wires (2) and a plurality of flexible conductive wires (3) are alternately arranged and woven into a hollow mesh structure; wherein the diameter of the flexible insulating wires (2) is greater than the diameter of the flexible conductive wires (3), and after the weaving is completed, steps of a certain height are naturally formed between them, which can not only prevent the conductive wires from contacting the inner channel and causing short circuit burns, but also enhance mass transfer and accelerate product discharge.

2. The flexible braided electrode according to claim 1, characterized in that: The flexible braided electrode (1) is braided in a single-strand braided structure, that is, a single-strand flexible insulating wire (2) and a single-strand flexible conductive wire (3) are braided in an alternating manner.

3. The flexible braided electrode according to claim 1, characterized in that: The flexible braided electrode (1) is braided in a three-strand braided structure, that is, two strands of flexible insulating wires (2) and a single strand of flexible conductive wire (3) are braided side by side and interlaced; each flexible conductive wire (3) is adjacent to two flexible insulating wires (2) on both sides.

4. The flexible braided electrode according to claim 1, characterized in that: The flexible braided electrode (1) is a positive braided structure, that is, the braiding wire direction is used as the curling axis.

5. The flexible braided electrode according to claim 1, characterized in that: The flexible braided electrode (1) is a 45° inclined braided structure, that is, the direction forming a 45° angle with the braided wire is used as the curling axis.

6. The flexible braided electrode according to claim 1, characterized in that: The flexible insulating threads (2) and the flexible conductive threads (3) are arranged alternately in both the warp direction and the weft direction.

7. The flexible braided electrode according to claim 1, characterized in that: The cross section of the flexible braided electrode (1) is circular, oval or square.

8. A method for electrochemical polishing of complex internal channels using the flexible braided electrode of claim 1, characterized in that The process includes: Step 1: fix the part to be processed (4) on the working table of the machine tool, and connect one end of the inner channel to the liquid collecting chamber (6); Step 2: placing the flexible braided electrode (1) along the inner channel in the part to be processed (4), and performing adaptive bending deformation according to the shape of the inner channel; One end of the flexible braided electrode (1) is connected to the first spindle (5) of the machine tool, and the other end is connected to the second spindle (9) of the machine tool, and the spindle of the machine tool is adjusted to the initial processing position; Step 3: Connect the flexible braided electrode (1) to the negative electrode of the power source (8), and connect the part to be processed (4) to the positive electrode of the power source (8); Step 4: Turn on the liquid supply system, a portion of the electrolyte flows into the inner hole of the flexible braided electrode (1) through the liquid supply end coaxial with the machine tool spindle (5), and flows into the processing gap between the flexible braided electrode (1) and the inner channel surface (7) of the part through the mesh gap formed between the flexible insulating wire (2) and the flexible conductive wire (3); another portion of the electrolyte flows into the liquid collecting cavity (6), enters the processing gap along the outer wall of the flexible braided electrode (1), and forms an inner and outer composite flushing liquid; the diameter of the flexible braided electrode insulating wire (2) is larger than the diameter of the conductive wire (3), so as to avoid short circuit burns caused by the contact between the flexible braided electrode conductive wire (3) and the inner channel surface (7) of the part during processing; Step 5: After the electrolyte fills the inner channel, the power supply (8) is turned on to control the machine tool spindle (5) to perform reciprocating motion along the axial direction and rotational motion around the axis, thereby driving the flexible braided electrode (1) to perform reciprocating motion and rotational motion. Under the combined action of electrochemical dissolution and mechanical motion of the flexible electrode (1), the inner channel surface (7) of the anode workpiece to be processed is electrochemically dissolved. The raised area of ​​the inner channel surface (7) is closer to the flexible braided electrode (1), so the electrochemical dissolution rate is higher, which has a leveling effect. At the same time, the electrochemical reaction products and bubbles are quickly discharged under the combined action of the electrolyte flushing and the motion of the flexible braided electrode (1), thereby achieving electrolytic polishing of the inner channel surface of the part. Step 6: After a period of time, when the roughness of the channel surface (7) inside the part reaches the processing requirement, stop processing.

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