Bionic flexible electrode based on coral appearance and self-compensation electrochemical polishing method thereof

Abstract

The invention provides a bionic flexible electrode based on a coral appearance and an electrochemical polishing method for an inner channel of the bionic flexible electrode, and belongs to the field of non-traditional machining of a mechanical manufacturing technology. The electrode is characterized in that the whole electrode adopts a hollow structure, and insulating parts and non-insulating parts of the electrode are alternately arranged. The conductive metal wires are arranged in a circumferential array and serve as an electrode main body, an electrolyte flow field is uniform in the machining process due to the good internal and external through characteristic, and discharge of electrolytic reaction products is accelerated; the bionic insulation parts with the circumferential array micropore structures are distributed at equal intervals along the axis of the electrode, so that short-circuit burn caused by contact between the conductive metal wires and the surface of the inner channel in the machining process is avoided. During machining, the electrode is subjected to self-adaptive bending in the inner channel or is combined with clamp control for self-compensation, and inner channel polishing is completed under the electrochemical action. By means of the method, finishing machining of the workpiece with the inner channel can be achieved, and the machining precision and the inner surface quality are improved.

Description

Technical Field

[0001] The invention relates to a bionic flexible electrode based on the shape of coral polyps and a self-compensating electrochemical polishing method thereof, belonging to the technical field of electrolytic machining. Background Art

[0002] Additive manufacturing technology has important applications in industries such as aerospace due to its advantages of flexibility, high efficiency, and light weight. Aiming at the urgent need for surface finishing of metal parts with inner channels in additive manufacturing, the present invention proposes a flexible electrode electrolytic polishing method, conducts research on modes such as tool cathode reciprocating motion, tool cathode rotational motion, and internal and external flushing, breaks through the flexible electrode structure design and optimization technology, conducts electrolytic polishing process tests on the surface of inner flow channels in additive manufacturing, masters the core technology, realizes surface finishing of parts containing inner channels under additive manufacturing technology, improves surface quality, and thus increases the service life of parts. This technology has a very broad application prospect and is of great significance to the development of related fields.

[0003] The surface roughness of laser additively manufactured metal parts is usually between 10-50μm, while the surface roughness of traditional machined parts is generally around 2.5μm. Rough surfaces can easily cause stress concentration and may lead to the generation of microcracks, which in turn affect the fatigue performance of parts. This is unacceptable for aerospace technology that requires high stability in harsh environments. At present, most parts directly formed by laser additive manufacturing are difficult to meet the quality inspection requirements of related application fields. There are a large number of raised structures on the surface of laser additively manufactured parts, resulting in severe surface undulations, which can be attributed to spheroidization effect, ripple effect, step effect and powder adhesion.

[0004] For complex internal channels, the visibility of the internal channels is poor, and it is difficult or impossible for the tool to reach the area to be processed, making it difficult to finish. Internal finishing of workpieces with complex internal channels is a difficult problem in current manufacturing. The current mainstream finishing technologies for additive manufacturing parts at home and abroad mainly include mechanical finishing, laser finishing, abrasive flow finishing, and electrochemical finishing. Compared with the first three finishing technologies, electrochemical finishing shows certain advantages. Mechanical polishing is the current mainstream technology, which has great advantages in cost control and processing effect. However, mechanical polishing has many processing steps, poor tool durability, and cannot process irregular internal surfaces. Abrasive flow finishing causes uneven surface material removal due to the mapping and diffusion of uncontrollable abrasive flow during the finishing process, and abrasive particles may remain on the surface after finishing. Laser finishing technology is greatly affected by laser accuracy and intensity. At the same time, local heating of additive parts in a short period of time during laser finishing may cause deformation or cracks of the workpiece, affecting its performance. Electrochemical finishing is a non-contact processing. There is no direct contact between the tool and the workpiece, no tool loss, no residual stress and work hardening layer will be generated after the workpiece is processed, and the surface of the processed parts is smooth. As an important branch of electrochemical subtractive processing, electrochemical polishing technology is widely used in the surface treatment of key parts such as aerospace structural parts, guns, etc., such as removing burrs on the surface of parts after mechanical processing.

[0005] From the above, it can be seen that the electrochemical polishing method can uniformly process the surface at the microscopic level, remove the surface roughness, oxide layer, impurities, etc., so as to obtain a smooth, uniform and clean surface; in the control of the parameters in the polishing process, such as voltage, current density, electrolyte flow rate, temperature, etc., the polishing effect can be precisely controlled; whether it is a small-sized internal channel part or a complex internal channel structure, relying on the spontaneous or external driving force of chemical reagents to cause high-degree-of-freedom flow, spread and diffusion, chemical reactions can occur at all positions of the additive manufacturing parts to dissolve the material. Therefore, it is very suitable for the internal channel polishing of metal parts. However, the internal channel of the workpiece has a small diameter and a large aspect ratio. In the actual processing process, there will be problems such as the inability to process the over-bending part, the inability to discharge the product in time, and short-circuit burns. Therefore, it is a key issue at present to design a tool cathode with good flexibility and effective electrochemical polishing of complex internal channels while avoiding short-circuit burns. Summary of the invention

[0006] Purpose of the Invention

[0007] In nature, coral tentacles and their mouthparts have the characteristics of high flexibility and adaptability. This biological characteristic provides new inspiration for the design of electrochemical machining electrodes. Coral polyps have many branches and their tentacles have a large surface area. The bionic designed electrodes also have a similar fractal structure to increase the surface area, so that the current distribution is more uniform and the efficiency is higher during processing; the adaptability enables the electrode to adapt to the shape changes of the workpiece during processing, reducing the need for clamping and adjustment, and is suitable for processing special-shaped curved surfaces or thin-walled parts; in addition, the flexible structure of coral polyps can promote and optimize the flow of electrolyte, reduce the accumulation of bubbles and processing products, and avoid short circuits or uneven corrosion during processing, which is helpful for processing accuracy and surface quality; the microscopic branch structure similar to coral polyps can also evenly disperse the current density, reduce edge effects, avoid local over-corrosion or insufficient processing, and is especially suitable for the processing of high-precision complex surfaces (such as turbine blades and microchannels) to improve processing efficiency.

[0008] Technical Solution

[0009] A bionic flexible electrode based on the shape of coral polyps, characterized by:

[0010] The bionic flexible electrode 1 is composed of a bionic insulating ring 3 with a coral polyp shape and a flexible metal wire 2 arranged at intervals, and the flexible metal wire 2 is inserted in the bionic insulating ring 3. The bionic flexible electrode 1 is a circular array structure as a whole, and the electrode body is composed of a conductive metal wire with a large aspect ratio and a certain flexibility, so that the electrode can be flexibly deformed;

[0011] The cross section of the flexible metal wire 2 is circular, the cross section of the bionic insulating ring 3 is perpendicular to the flexible metal wire 2, and the outer diameter of the insulating ring 3 is larger than the outer diameter of the circumferential array of the flexible metal wire 2, which can effectively avoid short circuit burns caused by direct contact between the metal wire and the hole wall;

[0012] For workpieces to be processed with different cross-sections, bionic flexible electrodes 1 with different cross-sections can be selected to match the channel shapes in the workpiece 4 to be processed, which can be circular, elliptical or square. The bionic flexible electrode according to claim 1 is characterized in that:

[0013] According to different inner channel structures, the present invention proposes two types of bionic flexible electrodes with different structures: Type I bionic flexible electrode 1-1, whose flexible metal wire 2 forms a small interference fit with the bionic insulating ring 3, and a small amount of deformation margin can be left when the electrode is bent, and one end thereof is a cylinder as a whole, which can be directly clamped on the machine tool fixture 9-1, and is mainly suitable for polishing long straight holes;

[0014] If the curvature of the inner channel of the workpiece to be processed is large, a Class II bionic flexible electrode 1-2 can be used for self-compensation processing. The flexible metal wire 2 and the bionic insulating ring 3 form a cross-distribution of small interference fit and clearance fit. One end of the metal wire 2 that is clearance-fitted with the bionic insulating ring 3 is clamped with a self-compensating micro-clamp 9-2, which is convenient for z-axis self-compensation control of a single metal wire 2. By controlling the z-axis displacement of the single metal wire 2, the bionic flexible electrode 1 is bent to different degrees in the curved inner channel to better fit the inner channel structure and achieve a better polishing effect.

[0015] The method for self-compensating electrochemical polishing of a bionic flexible electrode based on the shape of a coral polyp as claimed in claim 1 is characterized by comprising the following processing steps:

[0016] Step 1: Fix the workpiece 4 to be processed on the machine tool fixture, one end of the channel in the workpiece is connected to the liquid supply chamber 6, and the other end is connected to the liquid collection chamber 7;

[0017] Step 2: Place the bionic flexible electrode 1 along the inner channel in the workpiece 4 to be processed, connect one side of the electrode with a self-made fixture 9, and adjust the machine tool spindle to a suitable initial processing position;

[0018] Step 3: Connect the bionic flexible electrode 1 to the negative pole of the power source 8, and connect the workpiece 4 to be processed to the positive pole of the power source 8;

[0019] Step 4: Turn on the liquid supply system to allow the electrolyte to fill the inner channel along the liquid supply cavity and be recovered along the liquid collection cavity; the outer diameter of the bionic insulating ring 3 is larger than the flexible metal wire 2, which can effectively prevent the flexible metal wire 2 from contacting the inner wall 5 of the workpiece to be processed to cause short circuit burns;

[0020] Step 5: After the electrolyte fills the inner channel, the power supply 8 is turned on, and the type I bionic flexible electrode 1-1 is controlled by the self-made clamp 9-1 to perform reciprocating motion along the axial direction and rotational motion around the axis, or the type II bionic flexible electrode 1-2 is clamped by the micro clamp 9-2 to perform self-compensation movement of the flexible metal wire 2, the inner clamp of the axis compensates along the positive direction of the z-axis, and the outer clamp of the axis compensates along the negative direction of the z-axis;

[0021] Step 6: Through the synergistic effect of electrochemical dissolution and the mechanical movement of the bionic flexible electrode 1, the inner wall 5 of the anode workpiece to be processed is promoted to undergo an electrochemical dissolution reaction. In this process, the dual effects of electrolyte flushing and the movement of the bionic flexible electrode 1 can effectively remove electrochemical reaction byproducts and bubbles, and finally achieve electrolytic polishing treatment on the surface of the inner channel of the workpiece;

[0022] Step 7: When the roughness of the inner wall 5 of the workpiece to be processed reaches the processing requirement, the processing is stopped. The beneficial effects of the present invention are:

[0023] 1) An innovative flexible electrode structure is proposed. The cathode of this patent adopts a bionic coral tentacles structure, which is characterized by a hollow thin-walled cylinder, which is composed of a bionic insulating ring and a metal conductor wire with a small interference fit and arranged at intervals. Its structure is flexible and can be bent to any degree in the inner channel for finishing processing.

[0024] 2) A new internal channel polishing process is proposed. The electrode reciprocating motion and the electrode rotation are combined in the finishing process, making the finishing process more uniform and improving the processing efficiency; at the same time, the internal and external through-structure allows for better product discharge.

[0025] 3) It has a wide range of applications. The polishing process of this electrode is suitable for the internal channel processing of various metal materials and alloy materials, such as aerospace, medical equipment and other fields, and has a wide application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an overall schematic diagram of a flexible electrode that mimics the shape of coral polyps;

[0027] Figure 2 Schematic diagram of the flexible electrode imitating the shape of coral polyps clamped on the machine tool for electrochemical polishing of complex internal channels;

[0028] Figure 3 It is a structural schematic diagram of the bionic insulating ring;

[0029] Figure 4 Schematic diagram of the structure of type I bionic electrode and type II bionic electrode;

[0030] Figure 5 It is a schematic diagram of the cross-sectional structure of a bionic electrode used for processing a circular-like inner hole;

[0031] The numbers in the figure are as follows: 1. Bionic flexible electrode; 2. Flexible metal wire; 3. Bionic insulating ring; 4. Workpiece to be processed; 5. Inner wall of workpiece to be processed; 6. Liquid supply chamber; 7. Liquid collecting chamber; 8. Power supply; 9. Self-made fixture. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings.

[0033] like Figure 1As shown, this patent proposes a bionic flexible electrode based on the shape of coral polyps and a self-compensating electrochemical polishing method thereof. The bionic flexible electrode 1 is formed by the flexible metal wire 2 and the bionic insulating ring 3 being interlaced and arranged in an array. The electrode body is composed of a conductive metal wire with a large aspect ratio and a certain flexibility, so that the electrode can produce flexible deformation in places with large curvature in a complex inner channel to improve the force distribution during bending; the cross-section of the above-mentioned bionic flexible electrode 1 can be circular or elliptical, and the electrode as a whole is arranged in a circular array by conductive metal wires, and the bionic insulating part with circular array small holes is equidistantly distributed along the electrode axis, which can avoid short-circuit burns caused by contact between the conductive metal wire and the surface of the inner channel; for small holes in the inner channel with different cross-sections, the present invention also proposes different flexible electrodes, and the cross-sectional shape after bending corresponds to the shape of the inner channel of the workpiece 4 to be processed, and different types of parts can be processed.

[0034] like Figure 1 , 2 As shown, the flexible braided electrode electrochemical polishing complex inner channel method proposed by the present invention includes the following process:

[0035] 1) Fix the workpiece 4 to be processed on the workbench of the machine tool, and connect one end of the inner channel to the liquid collecting chamber 7;

[0036] 2) Place the flexible electrode 1 along the inner channel in the workpiece 4 to be processed, connect it with a special clamping device, and let the other end hang freely in the air, and adjust the machine tool spindle to a suitable initial processing position;

[0037] 3) Connect the flexible electrode 1 to the negative pole of the power source 8, and connect the workpiece 4 to be processed to the positive pole of the power source 8;

[0038] 4) Turn on the liquid supply system, and a portion of the electrolyte flows into the inner hole of the liquid supply cavity 6 through the liquid supply end coaxial with the machine tool spindle, and is injected into the inner channel through the gap between the bionic insulating ring 3 and the flexible metal wire 2; the diameter of the flexible electrode bionic insulating ring 3 is larger than the outer diameter of the flexible metal wire 2 array, so as to avoid short circuit burns caused by the contact between the flexible metal wire 2 and the inner channel surface 5 of the part during the processing;

[0039] 5) After the electrolyte has fully filled the inner channel, start the power supply 8, control the machine tool spindle to perform axial reciprocating motion and rotation, and drive the flexible electrode 1 to synchronously produce a compound motion. Through the synergistic effect of electrochemical dissolution and the mechanical movement of the flexible electrode 1, the directional dissolution of the inner channel surface 5 of the anode workpiece is completed. Among them, the raised part of the surface 5 is closer to the flexible electrode 1, and its accelerated dissolution characteristics can achieve surface morphology leveling. At the same time, the dual force formed by the flow of the electrolyte and the movement of the electrode can promptly remove the reaction by-products and bubbles, and finally achieve efficient electrolytic polishing of the inner channel surface;

[0040] 6) After a period of time, when the roughness of the channel surface 5 inside the part reaches the processing requirements, stop processing.

[0041] like Figure 3 As shown, the bionic insulating ring 3 proposed by the present invention is shaped like the tentacles of coral polyps and has a similar fractal structure to increase the surface area, making the current distribution more uniform and more efficient during processing. At the same time, the diameter of the bionic insulating ring 3 is larger than the array diameter of the flexible metal wire 2, which can effectively isolate the workpiece and the tool to prevent short circuit burns in the circuit.

[0042] like Figure 4 As shown, Class I and Class II bionic flexible electrodes are designed for workpieces with different degrees of inner channel curvature. The Class I bionic flexible electrode 1-1 is integrally clamped by a self-made fixture 9-1, and is adaptively flexibly bent by the reaction force of the inner wall in the inner channel to process the inner surface. For the inner channel with a larger curvature, a Class II flexible bionic electrode 1-2 is used. The z-axis displacement of a single flexible metal wire 2 is controlled by the micro fixture 9-2 to achieve a self-compensation control function, thereby making the electrode as a whole produce flexible bending to process the inner surface.

[0043] As shown in Figures 5 and 6, the shape of the flexible metal wire 2 array of the bionic flexible electrode 1 proposed in the present invention can be adjusted according to the cross-sectional shape of the inner channel to be processed, and the shape of the bionic insulating ring 3 can be changed accordingly to meet the processing requirements of inner channels of different shapes, such as circular, elliptical, etc.

Claims

1. A bionic flexible electrode based on the shape of coral polyps, characterized by: The bionic flexible electrode (1) is formed by a bionic insulating ring (3) with a coral polyp-shaped structure and a flexible metal wire (2) arranged at intervals, and the overall structure is a circular array structure. The electrode body is composed of a conductive metal wire with a large aspect ratio and a certain flexibility. The flexible metal wire (2) is inserted into the bionic insulating ring (3), so that the electrode can be flexibly deformed and bent. The cross section of the flexible metal wire (2) is circular, and the flexible metal wire (2) is perpendicular to the plane of the bionic insulating ring (3); the outer diameter of the insulating ring (3) is larger than the outer diameter of the circumferential array of the flexible metal wire (2), which can effectively prevent the metal wire from directly contacting the hole wall and causing short circuit burns; For workpieces to be processed with different cross sections, bionic flexible electrodes (1) with different cross sections can be selected to match the shapes of the channels in the workpieces to be processed (4), which can be circular, elliptical or square.

2. The bionic flexible electrode according to claim 1, characterized in that: According to different inner channel structures, the present invention proposes two types of bionic flexible electrodes with different structures: A Class I bionic flexible electrode (1-1), wherein the flexible metal wire (2) forms a small interference fit with the bionic insulating ring (3), and a small amount of deformation margin can be left when the electrode is bent. One end of the electrode is a cylindrical body and can be directly clamped on a machine tool fixture (9-1), and is mainly suitable for polishing long straight holes. If the curvature of the inner channel of the workpiece to be processed is relatively large, a type II bionic flexible electrode (1-2) can be used for self-compensation processing, wherein the flexible metal wire (2) and the bionic insulating ring (3) form a small interference fit and a clearance fit that are cross-distributed, and one end of the metal wire (2) that is clearance-fitted with the bionic insulating ring (3) is clamped with a self-compensating micro-clamp (9-2), which facilitates the z-axis self-compensation control of a single metal wire (2). By controlling the z-axis displacement of the single metal wire (2), the bionic flexible electrode (1) is bent to different degrees in the curved inner channel to better fit the inner channel structure and achieve a better polishing effect.

3. A method for self-compensating electrochemical polishing using a bionic flexible electrode based on the shape of coral polyps as claimed in claim 1, characterized in that The processing includes the following: Step 1: Fix the workpiece (4) to be processed on the machine tool fixture, one end of the channel in the workpiece is connected to the liquid supply chamber (6), and the other end is connected to the liquid collection chamber (7); Step 2: placing the bionic flexible electrode (1) along the inner channel in the workpiece to be processed (4), connecting one side of the electrode with a self-made fixture (9), and adjusting the machine tool spindle to a suitable initial processing position; Step 3: connecting the bionic flexible electrode (1) to the negative electrode of the power source (8), and connecting the workpiece to be processed (4) to the positive electrode of the power source (8); Step 4: Turn on the liquid supply system, so that the electrolyte fills the inner channel along the liquid supply cavity and is recovered along the liquid collection cavity; the outer diameter of the bionic insulating ring (3) is larger than the flexible metal wire (2), which can effectively prevent the flexible metal wire (2) from contacting the inner wall (5) of the workpiece to be processed to cause short circuit burns; Step 5: After the electrolyte fills the inner channel, the power supply (8) is turned on, and the type I bionic flexible electrode (1-1) is controlled by the self-made clamp (9-1) to perform reciprocating motion along the axis and rotational motion around the axis, or the type II bionic flexible electrode (1-2) is clamped by the micro clamp (9-2) to perform self-compensation movement of the flexible metal wire (2), the inner clamp of the axis compensates along the positive direction of the z-axis, and the outer clamp of the axis compensates along the negative direction of the z-axis; Step 6: Through the synergistic effect of electrochemical dissolution and the mechanical movement of the bionic flexible electrode (1), the inner wall (5) of the anode workpiece to be processed is promoted to undergo an electrochemical dissolution reaction. In this process, the dual effects of electrolyte flushing and the movement of the bionic flexible electrode (1) can effectively remove electrochemical reaction byproducts and bubbles, and finally achieve electrolytic polishing treatment of the inner channel surface of the workpiece; Step 7: When the roughness of the inner wall (5) of the workpiece to be processed reaches the processing requirement, the processing is stopped.

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