Electrochemical machining method for deep and long variable-cross-section shielded inner cavity

Abstract

The invention relates to the technical field of electrochemical machining, in particular to a deep and long variable cross-section shielding inner cavity electrochemical machining method which comprises the steps that a deep and long shielding reducing inner cavity single-blade electrode is designed according to the shape of a deep and long variable cross-section shielding inner cavity; the electrochemical machining process is divided into three stages according to the requirement for stable machining gap control under the condition of large-allowance removal deformation control of the deep and long variable-diameter shielding inner cavity and by combining the characteristic that machining gaps of all parts on the surface of the deep and long variable-cross-section shielding inner cavity are different through a single-blade electrode, and different machining modes are adopted in the different machining stages; wherein in the first stage, electrolytic machining reaches a dynamic equilibrium state, in the second stage, the problem of machining gap change caused by stress release deformation in a workpiece is solved through self-adaptive machining, stable electrolytic machining removal of a large number of materials is achieved, and in the third stage, double-Z-axis synchronous feeding of an electrode is driven by a motor, and long-stroke small-gap stable and accurate machining is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical machining, and particularly relates to a deep long variable cross-section shielded inner cavity electrochemical machining method. BACKGROUND

[0002] With the further improvement of the performance of modern helicopters, the key structural parts of the aircraft tend to be integral structures. In order to reduce the number of parts, reduce the take-off weight and improve the reliability, the hub arms in the helicopter rotor system are designed to be deep long variable diameter shielded inner cavities with small ends and large middle. The integral hub arm is a key force-bearing part of the helicopter during vertical take-off, flight and hovering, and simultaneously bears the centrifugal force, flapping bending moment and edgewise bending moment transmitted by the blades. At the same time, it also needs to withstand the atmospheric turbulence, vibration load of the engine and transmission system. At present, the deep long variable diameter shielded inner cavity is an integral closed structure with an inner cavity, and has the characteristics of insufficient openness, local area shielding, no projection surface, machining path interference, and the material is titanium alloy which is difficult to machine. This has become a bottleneck in the production and development process, and limits the use of integral components in the helicopter rotor system.

[0003] The machining of such components mainly adopts special horizontal boring machines. Due to the small opening, large hole diameter and long axial size, the boring process is limited, mainly manifested as the following problems: the machining of the workpiece at both ends is unavoidable, and there are tool marks at both ends; the elongated tool bar boring causes the tool head to vibrate and the cutting amount to decrease, and the efficiency is low. The hollow rod-shaped hub arm of the helicopter is an integral closed structure with a complex appearance structure, an internal shielded inner cavity, characteristics of small ends and large middle, long depth, and local area shielding, and the material is mostly titanium alloy which is difficult to machine. Due to poor machining accessibility and difficult-to-machine material, the conventional mechanical machining method is difficult or impossible to machine.

[0004] The conventional electrolytic machining also has the problems of the oversized forming cathode which cannot enter the shielded inner cavity, and the uneven electrolyte flow field in the small internal space. At the same time, by comparing and analyzing the deep long variable diameter shielded inner cavity before and after machining, it is found that the material removal reaches 50%, and the inner cavity removal process is also a process of continuous release of internal stress of the large forging. The inner cavity surface will be deformed due to stress release, resulting in a change in the gap between the electrode machining surface and the inner cavity surface, causing short circuit, burning of the electrode and the workpiece. The conventional electrolytic machining of the deep long variable diameter shielded inner cavity has the following problems: the oversized forming cathode cannot enter the shielded inner cavity; the cathode movement space is limited, and the electrolytic machining cannot be stably developed; the material removal of the deep long variable diameter shielded inner cavity is large, the internal stress of the forging is released, resulting in unstable electrolytic machining gap, and short circuit, burning of the electrode and the workpiece are prone to occur. SUMMARY

[0005] The present application provides a deep long variable cross-section shielded inner cavity electrochemical machining method to solve the problems in the background art.

[0006] The deep long variable cross-section shielding inner cavity electrochemical machining method comprises the following steps: According to the deep long variable cross-section shielding inner cavity shape, a deep long shielding variable diameter inner cavity single blade electrode is designed; According to the need for stable machining gap control under the condition of deep long variable diameter shielding inner cavity large residual removal deformation control, combining the characteristics of the machining gap of each part of the single blade electrode and the surface of the deep long variable cross-section shielding inner cavity, the electrolytic machining process is divided into three stages, and different machining modes are adopted in different machining stages; Among them, the first stage is that the electrolytic machining reaches a dynamic balance state, the second stage solves the problem of machining gap change caused by internal stress release deformation of the workpiece through self-adaptive machining, and a large amount of material is stably electrolytic machined and removed, and the third stage is that the electrode is synchronously fed in double Z axes under the driving of the motor, and long-stroke small-gap stable and accurate machining is realized. Further, the deep long shielding variable diameter inner cavity single blade electrode is designed according to the deep long variable cross-section shielding inner cavity shape, comprising the following steps: The cross section of the deep long variable cross-section shielding inner cavity axis and the generatrix is selected as the base surface to design the deep long shielding variable diameter inner cavity single blade electrode.

[0007] Further, the deep long shielding variable diameter inner cavity single blade electrode is designed according to the deep long variable cross-section shielding inner cavity shape, comprising the following steps: The deep long variable cross-section shielding inner cavity generatrix is divided into a straight segment, a converging segment of a rotating generatrix, and a right-angle segment of the rotating generatrix. Based on the normal angle θ of each segment of the generatrix, the shape of the electrode profile is designed and optimized according to the cosθ method and multi-physical field simulation.

[0008] Further, the normal angle θ of the straight segment is 0°, and the electrode profile in this segment is the same as the inner wall profile of the workpiece.

[0009] Further, the normal angle θ of the converging segment is less than 45°, and the electrode profile in this segment is calculated according to the normal angle.

[0010] Further, the normal angle θ of the right-angle segment is greater than 45°, and the electrode shape in this segment is corrected according to the results of multi-physical field simulation combined with actual test.

[0011] Further, the single blade electrode adopts a two-end support mode, and during electrolytic machining, the single blade electrode is vertically fed, the workpiece is rotated, and the final required structure is machined.

[0012] Further, the machining gap Δ0 between the electrode and the inner cavity surface in the first stage is greater than 1.5 mm; In this stage, the electrode moves towards the workpiece anode, and when the speed of electrode movement is equal to the dissolution speed of the workpiece anode, a dynamic balance is reached.

[0013] Further, the processing gap Δ0 between the second-stage electrode and the inner cavity surface is between 0.8 mm and 1.5 mm. At this stage, adaptive adjustment devices are arranged at both ends of the electrode, the adaptive adjustment devices adjust the distance between the electrode processing surface and the workpiece anode surface, and the automatic constant gap large excess material processing inner cavity material is avoided, and the gap changes after the stress is released.

[0014] Further, the processing gap Δ0 between the third-stage electrode and the inner cavity surface is between 0.3 mm and 0.8 mm. At this stage, the electrode full surface enters the processing area, the gap between the electrode and the workpiece is consistent in the whole processing area, the electrode is synchronously fed in the double-Z-axis under the driving of the motor, and the electrochemical machining is accurately performed in the small gap state.

[0015] The above technical solutions of the present application have the following advantages: The deep long variable cross-section shielding inner cavity electrochemical machining method provided by the present application is a stress-free machining method, can use an extremely long elongated rod, solves the machining problem of the deep long variable diameter shielding inner cavity axial long member, and does not affect the machining precision. The cross-section cathode shape used in the single-blade cross-section cathode surface-feeding electrochemical machining method is small, the structure is flexible, and combined with the optimized trajectory, the single-blade cross-section cathode surface-feeding electrochemical machining method can penetrate into the non-projection area, solves the problem of insufficient openness of the shielding structure. The present application divides the deep long variable diameter shielding inner cavity electrochemical machining process into three stages, and uses different machining modes in different machining stages, solves the problem that the machining process is uncontrollable due to the stress release and large deformation of the large excess material in the inner cavity, and balances the machining efficiency and machining precision. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor.

[0017] Figure 1 The deep long shielding inner cavity cross-section selection schematic diagram provided by the embodiment of the present application is shown in the figure. Figure 2 The single-blade electrode cathode profile design schematic diagram provided by the embodiment of the present application is shown in the figure. Figure 3 The deep long shielding variable diameter inner cavity single-blade electrode three-dimensional model diagram provided by the embodiment of the present application is shown in the figure. Figure 4 The deep long variable diameter shielding inner cavity electrochemical machining first-stage schematic diagram provided by the embodiment of the present application is shown in the figure. Figure 5A second stage diagram of the deep long variable-diameter shielding inner cavity electrolytic machining provided by the embodiment of the present application is shown in the figure; Figure 6 A third stage diagram of the deep long variable-diameter shielding inner cavity electrolytic machining provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0018] In the following description, for the purpose of explanation and not limitation, specific details are set forth, such as particular system configurations, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

[0019] It should be understood that the term "comprising" as used in the specification and in the claims indicates the presence of the recited features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0020] In addition, in the description of the specification and the appended claims, the terms "first", "second", "third", etc. are used only to distinguish descriptions, and cannot be understood as indicating or implying relative importance.

[0021] In the present specification, the reference "one embodiment" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearance of the phrases "in one embodiment", "in some embodiments", "in other embodiments", "in additional embodiments", etc. in various places throughout the specification is not necessarily all referring to the same embodiment, but means that "one or more but not all embodiments". The terms "comprise", "include", "have" and their conjugates mean "including but not limited to", unless otherwise specifically stated. "Multiple" means "two or more".

[0022] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0023] The embodiment of the application provides a deep long variable cross-section shielding inner cavity electrochemical machining method, which comprises the following steps: designing a deep long shielding variable-diameter inner cavity single-blade electrode according to the shape of the deep long variable cross-section shielding inner cavity; according to the need for stable machining gap control under the condition of deep long variable-diameter shielding inner cavity large-amount removal deformation control, combining the characteristics of the single-blade electrode and the machining gap of each part of the surface of the deep long variable cross-section shielding inner cavity, dividing the electrolytic machining process into three stages, and adopting different machining modes in different machining stages; wherein, the first stage is that the electrolytic machining reaches a dynamic balance state, the second stage solves the problem of machining gap change caused by workpiece internal stress release deformation through self-adaptive machining, and realizes stable electrolytic machining removal of a large amount of material, and the third stage realizes long-stroke small-gap stable and accurate machining through double-Z-axis synchronous feeding of the electrode under the driving of the motor. The embodiment of the application provides a single-blade cross-section cathode surface-feeding electrochemical machining method for machining of a deep long variable cross-section shielding inner cavity of a helicopter rotor system. The single-blade cross-section cathode surface-feeding electrochemical machining method is a stress-free machining method, can adopt an extremely long elongated rod, solves the machining problem of the deep long variable-diameter shielding inner cavity axial long component, and will not affect machining precision. The single-blade cross-section cathode surface-feeding electrochemical machining method adopts a small cross-section cathode shape, has flexible structure, can penetrate into a non-projective surface area in combination with an optimized track, and solves the problem of insufficient openness of the shielding structure. The embodiment of the application divides the deep long variable-diameter shielding inner cavity electrolytic machining process into three stages, adopts different machining modes in different machining stages, solves the problem of uncontrollable machining process caused by large-amount material stress release deformation of the inner cavity, and takes into account machining efficiency and machining precision.

[0024] In some embodiments, the deep long shielding variable-diameter inner cavity single-blade electrode is designed according to the shape of the deep long variable cross-section shielding inner cavity, and the method comprises the following steps: selecting a section of an axis and a generatrix of the deep long variable cross-section shielding inner cavity as a base surface to design the deep long shielding variable-diameter inner cavity single-blade electrode.

[0025] In some embodiments, the deep long shielding variable-diameter inner cavity single-blade electrode is designed according to the shape of the deep long variable cross-section shielding inner cavity, and the method comprises the following steps: dividing the generatrix of the deep long variable cross-section shielding inner cavity into a straight segment, a converging segment of a rotating generatrix and a right-angle segment of the rotating generatrix; based on normal line angles θ of the segments of the generatrix, the shape of an electrode profile is designed and optimized according to a cosθ method and multi-physical field simulation.

[0026] In some embodiments, the normal line angle θ of the straight segment is 0°, and the electrode profile in the segment is the same as the inner wall profile of the workpiece.

[0027] In some embodiments, the normal line angle θ of the converging segment is less than 45°, and the electrode profile in the segment is calculated according to the normal line angle.

[0028] In some embodiments, the normal angle θ of the right-angle section is greater than 45°, and the section is corrected according to the simulation results of multiple physical fields and actual tests.

[0029] In some embodiments, the single-blade electrode adopts a two-end support mode, and during the electrochemical machining, the single-blade electrode is vertically fed, and the workpiece is rotated to machine the final required structure.

[0030] In some embodiments, the machining gap Δ0 between the first-stage electrode and the inner cavity surface is greater than 1.5 mm; during this stage, the electrode moves towards the workpiece anode, and when the moving speed of the electrode is equal to the dissolution speed of the workpiece anode, a dynamic balance is reached.

[0031] In some embodiments, the machining gap Δ0 between the second-stage electrode and the inner cavity surface is between 0.8 mm and 1.5 mm; during this stage, an adaptive adjustment device is arranged at the two ends of the electrode, the distance between the electrode machining surface and the workpiece anode surface is adaptively adjusted, the automatic constant gap over-machining of the inner cavity material is avoided, and the gap change after stress release is avoided.

[0032] In some embodiments, the machining gap Δ0 between the third-stage electrode and the inner cavity surface is between 0.3 mm and 0.8 mm; during this stage, the electrode full surface enters the machining area, the gap between the electrode and the workpiece is consistent in the full machining area, and the electrode is synchronously fed in the double-Z-axis under the drive of the motor, so that the electrochemical machining is accurately performed in a small gap state.

[0033] The specific technical solutions of the embodiments of the present application are as follows: (1) Selection of deep and long shielding inner cavity section The deep and long shielding variable-diameter inner cavity is formed by rotating a smooth and excessively curved generatrix, the cathode section is selected to pass through the workpiece axis and the generatrix section, and a design electrode base surface is formed, as shown in Figure 1 .

[0034] (2) Design of deep and long variable-section rotary shielding inner hole cathode During the electrochemical machining, the cathode surface needs to be designed according to the final shape of the shielding inner cavity, and the simulation results and test results are combined for optimization. As shown in Figure 2 , the deep and long shielding variable-diameter inner cavity generatrix can be divided into three regions: ① straight section (region 1), the curve normal angle θ is 0°, cosθ is 1, the electrode surface is the same as the inner wall surface of the workpiece; ② converging section of the rotary generatrix (region 2), the curve normal angle θ is less than 45°, the cathode surface is calculated according to the normal angle of the anode curve; and ③ right-angle section of the rotary generatrix (region 3), the curve normal angle θ is greater than 45°, and the cosθ method is invalid, and the electrode shape needs to be corrected according to the simulation results of multiple physical fields and actual tests.

[0035] The three-dimensional model of the cathode surface obtained according to the cosθ method and simulation optimization is as shown in Figure 3As shown. In order to ensure coaxial, take two end support mode. Electrochemical machining, single blade electrode vertical face feed, specimen rotation, processing out the final required structure.

[0036] (3) Deep long diameter shielding internal cavity multi-mode processing Deep long diameter shielding internal cavity single edge material removal of more than 65 mm, the overall material removal rate of more than 50%, the specimen a large amount of material removal internal stress release deformation, resulting in electrode and specimen inner surface gap unstable, short circuit. Deep long diameter shielding internal cavity electrochemical machining is a dynamic balance process, in different stages, the state of electrochemical machining is not the same.

[0037] The embodiment of the application is divided into three stages according to the different gap between single blade electrode and internal cavity surface processing: The first stage: the distance between the electrode and the internal cavity surface of the specimen is large, the processing gap △0>1.5mm, the electrochemical machining enters the pre-stable state, the stray corrosion is serious, and the processing does not have locality, such as Figure 4 As shown. In this stage, the workpiece (anode) is dissolved by the negative ions in the electrolyte under the action of the electric field, and the gap between the electrode and the workpiece is increased. With the continuous electrolysis process, the anode is continuously dissolved, in order to maintain the constant gap of electrochemical machining, the tool cathode will move to the anode. When the moving speed of the tool cathode is equal to the dissolution speed of the anode, the balance is reached, and the electrochemical machining enters the stable state.

[0038] The second stage: the distance between the electrode and the internal cavity surface of the specimen is between 0.8mm-1.5mm, the constant gap processing, the high efficient removal of large amount of material, but the stray is serious, such as Figure 5 As shown. In this stage, the deep long diameter shielding internal cavity cannot be monitored and observed during processing due to its long axial and shielding at both ends. Once the processing is carried out, the intermediate process cannot be intervened and adjusted. The embodiment of the application proposes a cathode self-adaptive control feeding electrochemical machining method for shielding internal cavity of aircraft integral component in the second processing stage of shielding internal cavity. Single blade electrode can penetrate into the internal cavity of shielding internal cavity, the electrode self-adaptive feeding, self-adaptive adjusting the distance between the electrode processing surface and the anode surface of the workpiece, and automatically constant gap processing internal cavity material with large amount of material. The large amount of material removal releases the internal stress of the workpiece, and the workpiece deforms; but the self-adaptive constant gap processing ensures the stable and orderly electrochemical machining.

[0039] The third stage: the distance between the electrode and the inner cavity surface of the workpiece is small, and the machining gap Δ0 is between 0.3mm and 0.8mm. The electrode full surface enters the machining area, the gap between the electrode and the workpiece is consistent in the whole machining area, the electrode is synchronously fed in the double-Z axis under the driving of the motor, and the electrochemical machining is stably carried out in the small gap state. In this stage, the electrochemical machining process is stable, the electric field is uniformly distributed, the machining precision is high, the machining surface quality is good, the machining has locality, and the stray corrosion is inhibited, as shown in FIG. 8. Figure 6

[0040] The single-blade cross-section cathode surface-feeding electrochemical machining method has the advantages of high efficiency, no electrode loss, and low machining cost. The single-blade cross-section cathode surface-feeding electrochemical machining method is a stress-free machining method, can adopt an extremely long extension rod, solves the machining problem of the deep and long variable-diameter shielded inner cavity axial long component, and will not affect the machining precision. The single-blade cross-section cathode surface-feeding electrochemical machining method adopts a small cross-section cathode shape, has flexible structure, and can penetrate into the area without projection surface in combination with the optimized trajectory, solves the problem of insufficient openness of the shielding structure.

[0041] In view of the problems that the deep and long variable-diameter shielded inner cavity large-amount material removal (total weight 50%) is uncontrollable in the machining process due to the internal stress release deformation of the forging, and the efficiency and precision cannot be considered, the electrochemical machining process is innovatively divided into three stages, and different machining modes are adopted in different machining stages. In the first stage, the electrochemical machining reaches the balanced state. In the second stage, the self-adaptive machining is mainly proposed to control the internal stress release deformation, improve the machining efficiency, and remove the large amount of material. In the third stage, the electrode is synchronously fed in the double-Z axis under the driving of the motor, the small gap is stably machined, the electric field is uniformly distributed, the machining precision is high, the machining surface quality is good, the machining has locality, and the stray corrosion is inhibited.

[0042] It should be noted that each of the embodiments in the specification adopts a progressive manner for description, and the same or similar parts between each of the embodiments can be referred to each other. Each of the embodiments mainly describes the difference from other embodiments. The application is not limited to the specific structures described above and shown in the drawings. Moreover, for the sake of brevity, the detailed description of the known methods and techniques is omitted.

[0043] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.​

Claims

1. A method for electrochemical machining of deep, long, variable cross-section shielded internal cavities, characterized in that, include: Design a single-edge electrode for a deep, long, variable-section shielded cavity based on the shape of the shielded cavity. Based on the need for stable machining clearance control under the condition of large allowance removal deformation control in deep and long variable diameter shielded inner cavity, and combined with the different machining clearances of various components on the surface of the single-edged electrode and deep and long variable cross section shielded inner cavity, the electrolytic machining process is divided into three stages, and different machining modes are adopted in different machining stages. The process consists of three stages: the first stage is to achieve a dynamic equilibrium state through electrolytic machining; the second stage is to solve the problem of changes in machining gap caused by stress release and deformation inside the workpiece through adaptive machining, thereby achieving stable electrolytic machining removal of a large amount of material; and the third stage is to achieve stable and precise machining with long stroke and small gap by synchronous feeding of the electrodes on both Z axes under the drive of the motor.

2. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 1, characterized in that, The design of the deep-length shielded variable-diameter inner cavity single-edge electrode based on the shape of the deep-length variable cross-section shielded inner cavity includes: A deep, long, variable cross-section shielding the inner cavity axis and generatrix is ​​selected as the base plane to design a deep, long, shielding variable diameter single-edged electrode for the inner cavity.

3. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 2, characterized in that, The design of a deep, long, variable cross-section shielding inner cavity axis and generatrix single-edge electrode, using the cross-section as the base plane, includes: The deep, long, variable cross-section shielding inner cavity generatrix is ​​divided into a straight segment, a convergent segment of the rotating generatrix, and a right-angle segment of the rotating generatrix. Based on the normal angle θ of each busbar segment, the shape of the electrode surface is designed and optimized according to the cosθ method and multiphysics simulation.

4. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 3, characterized in that, The normal angle θ of the straight section is 0°, and the electrode profile in this section is the same as the inner wall profile of the specimen.

5. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 3, characterized in that, The normal angle θ of the convergence segment is less than 45°, and the electrode profile is calculated based on the normal angle in this segment.

6. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 3, characterized in that, The normal angle θ of the right-angle segment is greater than 45°. The electrode shape in this segment is modified based on the results of multiphysics simulation and actual experiments.

7. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 1, characterized in that, The single-edged electrode is supported at both ends. During electrolytic machining, the single-edged electrode is fed vertically while the workpiece rotates to produce the final desired structure.

8. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 1, characterized in that, In the first stage, the machining gap between the electrode and the inner cavity surface, Δ0, is greater than 1.5 mm. During this stage, the electrode moves toward the anode of the workpiece, and a dynamic equilibrium is reached when the speed at which the electrode moves is equal to the speed at which the anode of the workpiece dissolves.

9. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 1, characterized in that, In the second stage, the machining gap Δ0 between the electrode and the inner cavity surface is between 0.8mm and 1.5mm. At this stage, adaptive adjustment devices are set at both ends of the electrode to adaptively adjust the distance between the electrode machining surface and the workpiece anode surface, automatically and with a large allowance to process the inner cavity material with a constant gap, avoiding gap changes after surface stress is released.

10. The electrochemical machining method for deep, long, variable cross-section shielded internal cavities as described in claim 1, characterized in that, In the third stage, the machining gap Δ0 between the electrode and the inner cavity surface is between 0.3mm and 0.8mm. At this stage, the entire surface of the electrode enters the machining area, the gap between the electrode and the workpiece is consistent throughout the machining area, the electrode is synchronously fed by the dual Z-axis under the drive of the motor, and electrolytic machining is carried out precisely in a small gap state.

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