Tool cathode and method for improving flatness of fly-by electrochemical milling surface machining

Abstract

The present invention relates to a tool cathode and method for improving the flatness of fly-by electrolytic milling surface processing, and belongs to the field of electrolytic processing. In the present invention, the cathode has a cylindrical structure, a pair of water outlet holes with contours defined by parametric equations are provided at the end, and a pair of normal positioning plates are provided on the outer circular wall. The cathode has six steps for plane processing, which mainly relies on two cycles of adjacent groove processing and adjacent groove joint mark processing. The cathode end face uses the shape of the water outlet to adjust the distribution of the metal conductive area, so that the power supply received in the vertical direction of the processed groove is consistent during rotational feeding, which greatly improves the flatness of the bottom surface after groove processing. When the cathode is not rotating, the concentrated power supply between the two water outlet holes at the cathode end can be used to remove the joint marks at the junction of adjacent grooves. One cathode solves two major problems, and improves the flatness of fly-by electrolytic milling surface processing simply and efficiently.

Description

Technical Field

[0001] The invention relates to a tool cathode and a method for improving the flatness of a fly-by electrolytic milling plane, belonging to the field of electrolytic machining. Background Art

[0002] Fly-through electrochemical milling (ECM) is a specialized machining technique that uses a simple rod-shaped cathode to electrochemically machine the workpiece surface in a manner similar to CNC milling. The tool cathode scans and moves across the workpiece surface according to a specified CNC program. The electrolyte, often in the form of an internal spray, rapidly flows into the machining gap, forming a conductive circuit between the tool cathode and the workpiece. The workpiece surface material undergoes an electrochemical reaction and is dissolved and removed. Fly-through electrochemical milling enables directional machining and material removal of designated areas on the workpiece surface. The machining process involves no cutting forces, and does not generate residual stress, recast layers, or microcracks. Furthermore, the tool cathode used is lossless and low-cost. Consequently, ECM technology has attracted widespread attention from scholars both domestically and internationally, leading to numerous research efforts.

[0003] The use of a rotating cathode is currently a popular choice for fly-by-fly electrochemical milling (ECM). This is because the rotating cathode's simultaneous feed mode promotes rapid electrolyte renewal, maintaining high electrolyte conductivity. This not only improves machining efficiency but also eliminates the hazards of short circuits and sparks. Furthermore, the rotating cathode optimizes the flow distribution within the machining gap, reducing stagnation time in turbulent fluids and significantly improving machining accuracy. Most notably, the use of a rotating cathode is key to integrating ECM with other machining processes, such as electrochemical spark discharge machining (EDM), aligning with the broader trend of developing hybrid machining technologies. However, the major drawback of using a rotating cathode for fly-by-fly electrochemical milling is that the machined surface typically has a curved arc profile, resulting in poor surface flatness. Because the electric field distribution on the rotating cathode's circular base is uneven, the amount of electricity per unit area perpendicular to the feed direction decreases from the center toward the edges. Consequently, the amount of material dissolved by the electrochemical anode is greater in the center and less at the edges. Consequently, the machining depth is naturally deeper in the center and shallower at the edges, resulting in an arc-shaped profile. Moreover, the larger the size of the rotating cathode, the greater the difference in the power supply distribution, and the worse the surface smoothness after processing. Poor surface smoothness will not only greatly reduce processing efficiency, but also easily cause overcutting and damage the surface quality of the processed surface.

[0004] Furthermore, the current approach to surface machining with electrochemical fly milling (ECM) generally involves combining and expanding multiple parallel grooves into a flat surface. This involves secondary machining of adjacent groove sidewalls to offset the removal of a portion, while preserving the bottom surface of each groove. In principle, regardless of the electrode used, the groove sidewalls after electrochemical machining are inherently inclined and curved, making it impossible to achieve a profile perpendicular to the bottom surface as achieved with traditional machining. This means that even after secondary machining of adjacent groove sidewalls, a portion of the grooves will remain, representing a joint mark. Current research on joint marks is limited to adjusting the amount of secondary machining to minimize them, with no definitive solution. Furthermore, the poor surface flatness of individual grooves means that very little of the bottom surface needs to be retained, leaving the majority of the groove profile as sidewalls for secondary machining. This results in more material remaining after secondary machining, leading to larger joint marks. These are the two major challenges that currently undermine flatness in ECM: poor individual track flatness and the difficulty in removing joint marks across multiple tracks.

[0005] Many scholars have conducted research on the flatness problem of electrolytic machining. The patent "Combined electrolytic machining tool cathode and method for improving the flatness of the bottom surface of the machining" (authorization announcement number: CN112091338B, inventors: Ma Xin; Li Hansong; Qu Ningsong; Yue Xiaokang) proposes a combined electrode to improve the flatness of the bottom surface of electrolytic machining. However, this combined electrode is a translational electrode, not a rotating electrode, and it is not suitable for many application scenarios of rotating cathodes. The patent "Tool cathode and method for improving the flatness of the bottom surface of electrolytic milling" (authorization announcement number: CN108080755B, inventors: Niu Ni; Qu Ningsong; Yue Xiaokang; Li Hansong) is used for electrolytic milling with a large cutting depth, that is, the bottom surface of the tool cathode is located below the surface of the anode workpiece being machined, and the outer circle and bottom surface of the tool cathode need to be processed at the same time. Therefore, the machining gap of electrolytic milling is divided into two parts, one part is between the outer circle of the tool cathode and the semicircular side wall of the workpiece to be machined, and the other part is between the bottom surface of the tool cathode and the bottom surface of the workpiece to be machined. In this way, the flow field is naturally divided into two parts. In electrolytic milling, the semicircular side wall of the workpiece to be machined will simultaneously limit the flow field of the two parts of the machining gap, converge the electrolyte at the bottom of the tool cathode, and destroy the machining flatness. Patent CN108080755B suppresses the convergent flow of the electrolyte and diffuses the flow field distribution by designing the tool cathode structure, thereby improving the flatness of the bottom surface of electrolytic milling. However, the machining states and conditions of fly-by electrolytic milling and electrolytic milling are so different that they cannot be compared. The bottom surface of the tool cathode in fly-by electrolytic milling moves above the surface of the anode workpiece, and the outer circle of the tool cathode does not participate in the machining, so the flow field is only distributed in the machining gap between the bottom surface of the tool cathode and the machined surface of the workpiece. In addition, the depth of fly-by electrolytic milling is relatively small, which allows the electrolyte in the machining gap to freely overflow and diffuse in all directions, without any constraints or convergence effect. Therefore, the solution proposed by this patent is not applicable to fly-by rotary cathode electrolytic milling. The key to improving the flatness of its single groove machining is still to start from the fundamental distribution of the electric field (power supply). As for the problem of joint marks at the junction of adjacent grooves, most of the current research adjusts the amount of secondary processing to minimize the joint marks, and then uses other process methods to remove the minimized joint marks. The actual operation is very complicated, and the machining accuracy and quality are difficult to guarantee. It has always been the ideal pursuit of scholars at home and abroad to use electrolytic milling to remove joint marks without the help of other processes. Summary of the Invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention designs a tool cathode and method for improving the flatness of fly-by electrolytic milling plane processing, and uses the shape design of the water outlet on the cathode end face to adjust the distribution of the metal conductive area, so that the power supply received from the cathode end face in the vertical direction of the processing groove tends to be consistent when the cathode rotates and feeds, thereby greatly improving the flatness of the bottom surface after single groove processing; and when the cathode is not rotating, the concentrated power supply between the two water outlet holes at the cathode end can be used to complete the electrochemical dissolution and removal of the tool marks at the junction of adjacent grooves, killing two birds with one stone.

[0007] A tool cathode for improving flatness in fly-by electrolytic milling, characterized in that: the tool cathode has a cylindrical structure, an outer radius of R, an inner radius of r, a height of H, and an end thickness of h1; a rectangular coordinate system is established with the end face center as the origin, the cathode axis as the Z axis, the direction from the uncovered end of the cathode to the end face as the positive direction of the Z axis, and two perpendicular diameter lines on the end face as the X and Y axes;

[0008] A pair of normal square spacers are provided on the outer circular wall of the tool cathode near the end. The two spacers are mirror-symmetrical about the YZ plane, and each spacer itself is mirror-symmetrical about the XZ plane. The thickness of the spacer along the Y axis is h2; the length of the spacer along the Z axis is E; and the width of the spacer along the X axis is F.

[0009] The cathode end of the tool has a pair of water outlet holes, the hole walls of which are always perpendicular to the end face. The two water outlet holes are mirror-symmetrical about the XZ plane, and each water outlet hole itself is mirror-symmetrical about the YZ plane; the contour of the water outlet hole in the first quadrant of the XY plane satisfies the parametric equation

[0010] The known number a in the parametric equation satisfied by the above-mentioned water outlet contour in the first quadrant determines the smaller value of the ordinate of the intersection of the water outlet contour and the y-axis, and the value range of a is [R / 90, R / 18]. The known number b determines the curvature of the contour of the water outlet in the first quadrant, and the value range of b is [0.5R, 0.8R]. k is an independent variable.

[0011] A pair of normal positioning plates are provided on the outer circular wall of the tool cathode of the present invention, and the two positioning plates are mirror-symmetrical about the YZ plane, which is convenient for design and manufacture. Each normal positioning plate itself is mirror-symmetrical about the XZ plane, and the thickness of the positioning plate along the Y-axis direction is very thin, so the entire tool cathode can be considered to be mirror-symmetrical about the positioning plate. The two water outlets can also be considered to be mirror-symmetrical about the positioning plates, so when the end face of the tool cathode is very close to the processed surface of the workpiece during processing so that it cannot be observed, the state of the entire tool cathode can be understood by observing the position angle of the positioning plates. In addition, each water outlet itself is mirror-symmetrical about the YZ plane, so the outline of the water outlet in the second quadrant is symmetrical with the outline in the first quadrant, and the outline of the other water outlet in the third and fourth quadrants is symmetrical with the second and first quadrants respectively. In this way, the entire outline of the two water outlets can be determined by only determining the outline in the first quadrant through a parametric equation. This parametric equation adjusts the conductive area distribution of the metal end face by designing the outlet shape. This ensures that the power supplied to the cathode end face in the vertical direction of the machined groove is uniform during the cathode's rotational feed, resulting in a smooth machined groove bottom. The entire tool cathode is designed as a cylindrical structure with a thickness of only h1 at the end, rather than a cylindrical structure. This is also to avoid the difficulty of improving the power supply distribution in the parametric equation due to the excessively long wall of the outlet hole at the end.

[0012] It's clear that the water outlets in the first and second quadrants intersect the positive y-axis at two points. The ordinate of the intersection point near the cathode axis is determined by a, which determines the conductive metal area at the center of the cathode end face. To reduce the amount of power supplied to the central region of the machined groove and ensure the parametric equation improves the uniformity of power distribution, a cannot exceed R / 18. To avoid the tip effect and maintain the structural strength of the cathode end face, a cannot be less than R / 90. The larger the number b, the smaller the curvature of the water outlet profile. The value range of b is [0.5R, 0.8R]. If it is too small, the conductive metal area at the cathode end face will be insufficient, significantly reducing the material removal rate and machining efficiency. If it is too large, the parametric equation cannot guarantee the uniformity of power distribution, nor can it improve the machined surface smoothness. Therefore, this value range represents a balance between surface smoothness and machining efficiency.

[0013] The above-mentioned method for machining a tool cathode for improving the flatness of a surface processed by fly-by electrochemical milling is characterized by comprising the following steps:

[0014] Single groove machining process: The tool cathode is mounted on the machine tool spindle and connected to the negative pole of the power supply. The workpiece is mounted on the machine tool table and connected to the positive pole of the power supply. The end face of the tool cathode is always higher than the upper surface of the workpiece. The electrolyte is injected into the tool cathode from top to bottom through the spindle, then sprayed onto the workpiece surface through the water outlet and overflowed and diffused in all directions, filling the machining gap between the tool cathode and the workpiece to form a conductive circuit. The spindle drives the tool cathode to rotate and feed forward, electrochemically dissolving the workpiece surface. The shape of the water outlet is designed to adjust the distribution of the metal conductive area on the end face of the tool cathode, so that the power supply received from the cathode end face in the vertical direction of the machined groove is consistent, so the bottom surface flatness of the groove after machining is greatly improved.

[0015] Specific processing steps:

[0016] Step 1, first groove processing: the tool cathode keeps rotating and feeds from the starting point of the first groove to the end point of the first groove, and the first groove is processed according to the single groove processing process;

[0017] Step 2: Processing the second groove:

[0018] 2-1. The tool cathode keeps rotating and feeds a distance d along the normal direction of the first groove processing direction, that is, processing from the end point of the first groove to the starting point of the adjacent second groove;

[0019] 2-2. According to the single groove processing process, the tool cathode keeps rotating and processes from the starting point of the second groove to the end point of the second groove in the opposite direction of the processing direction of the first groove;

[0020] 2-3. The tool cathode keeps rotating and feeds back from the end point of the second groove to the starting point of the first groove along the normal direction of the second groove processing direction, completing the processing of the second groove;

[0021] Step 3: Processing the cutting marks of the first and second grooves:

[0022] 3-1. Tool setting at the cutting mark: When the power is turned off, the spindle drives the tool cathode from the starting point of the first groove to the midpoint between the starting point of the first groove and the end point of the second groove. After the positioning piece of the tool cathode moves to a position parallel to the cutting mark, the spindle stops rotating.

[0023] 3-2. Removing the cutting mark: After reducing the power output and turning on the power, the spindle stops rotating to ensure that the tool cathode positioning piece is aligned parallel to the cutting mark, and feeds along the cutting mark. The concentrated power supply between the two water outlets of the tool cathode completes the electrochemical dissolution removal of the cutting mark, significantly improving the flatness of the bottom surface of the two adjacent grooves.

[0024] 3-3. After the cutting marks are removed, the power is turned off and the spindle drives the tool cathode to move back to the starting point of the second groove;

[0025] Step 4: Processing of other adjacent grooves:

[0026] 4-1. The groove that has just been machined is called the Nth groove, where N ≥ 2. After the power supply is restored, the tool cathode is powered on, and it keeps rotating and feeds a distance d in the normal direction of the machining direction of the Nth groove, that is, it machines from the starting point of the Nth groove to the starting point of the adjacent N+1th groove.

[0027] 4-2. According to the single groove processing process, the tool cathode keeps rotating and processes from the starting point of the N+1 groove to the end point of the N+1 groove in the same direction as the processing direction of the Nth groove;

[0028] 4-3. The tool cathode keeps rotating and feeds back from the end point of the N+1th groove to the end point of the Nth groove along the normal direction of the machining direction of the N+1th groove, completing the machining of the N+1th groove;

[0029] Step 5: Processing of cutting marks of other adjacent grooves:

[0030] 5-1. Tool setting at the cutting mark: When the power is turned off, the spindle drives the tool cathode from the end point of the Nth groove to the midpoint between the end points of the Nth groove and the N+1th groove. After the positioning piece of the tool cathode moves to a position parallel to the cutting mark, the spindle stops rotating.

[0031] 5-2. Removal of the cutting mark: After reducing the power output and turning on the power, the spindle stops rotating to ensure that the tool cathode positioning piece is aligned parallel to the cutting mark, and feeds along the cutting mark. The concentrated power supply between the two water outlets of the tool cathode is used to complete the electrochemical dissolution removal of the cutting mark, which significantly improves the flatness of the bottom surface of the adjacent grooves.

[0032] 5-3. After the cutting marks are removed, the power is turned off and the spindle drives the tool cathode to move back to the starting point of the N+1 groove;

[0033] Step 6. Repeat steps 4 and 5 to process the plane: After restoring the power output, turn on the power and repeat the above steps 4 and 5. In this way, the electrolytic milling plane is processed by combining adjacent grooves and removing the cutting marks at their junctions.

[0034] The present invention is aimed at fly-by electrolytic milling. During the groove processing, the power supply received by the processing groove in the vertical direction from the circular bottom surface of the traditional cathode must be the largest in the center and decreases towards the two edges, resulting in the largest amount of material removal in the center of the processing groove and decreasing towards the two edges. In this way, the processing groove presents an arc-shaped contour that is deep in the middle and shallow on both sides in the vertical direction. In addition, the cathode bottom surface of the fly-by electrolytic milling processing is higher than the upper surface of the anode workpiece, which causes the electrolyte to overflow and disperse, making it difficult to restrain. Therefore, to improve the surface flatness, it is necessary to start from the fundamental point of the electric field (power supply) distribution. Using the parametric equations obtained by rigorous derivation, the cathode end face of the tool determines the shape contour of the water outlet and also determines the distribution of the remaining metal conductive area. During single-groove machining in steps 1, 2, and 4, it was found that the metal conductive area decreases closer to the center of the cathode end face, significantly reducing the power supply to the corresponding area in the center of the machined groove during the cathode's rotational feed. However, the metal conductive area increases closer to the edge of the cathode end face, ensuring sufficient power supply to the corresponding areas at the edge of the machined groove during the cathode's rotational feed. This reverses the traditional power distribution pattern of the rotating cathode, which decreases from the center to the edges. The power supply from the cathode end face, perpendicular to the machined groove, becomes more uniform from the center to the edges, resulting in a more uniform material removal rate, significantly improving flatness. This single-groove machining process solves the first problem that can hinder flatness in fly-by electrochemical milling: poor flatness of individual tracks. In step 2, by machining adjacent grooves, the single groove is transformed into a small plane composed of two grooves. This is the basic principle of fly-by electrochemical milling for surface machining. The same principle applies to step 4. Although the bottom surfaces of the two adjacent grooves are flattened, the side walls of the grooves are still tilted and curved, which cannot be avoided based on the principle of electrolytic machining. Therefore, when processing adjacent grooves in steps 2-2 and 4-2, the adjacent side walls of the previous groove will still leave cutting marks after secondary processing, which directly destroys the flatness.

[0035] The cross section of the joint mark is very similar to a triangle, except that the two sides are arcs instead of straight lines; and the joint mark is straight as a whole and parallel to the direction of the groove. In order to remove the joint mark, the present invention clearly defines the distribution of the metal conductive area with a diameter of the end face (i.e., the X-axis) as the axis when designing the cathode end face of the tool, so the two water outlets are mirror-symmetrical about the XZ plane, and the entire tool cathode is mirror-symmetrical about the XZ plane. The remaining conductive metal between the two water outlets on the cathode end face surrounds the X-axis to form a conductive metal strip. Its shape is narrow in the middle and wide on both sides, which improves the power supply distribution during the rotational feed process, and can concentrate the electric field distribution below the X-axis when it is not rotating, which is very suitable for processing straight joint marks. Therefore, the position of the joint mark is determined by steps 3-1 and 5-1. The power is turned off to stop the power supply during the tool setting process to avoid damaging the processed surface. When the positioning plate is aligned parallel to the cutter mark, the conductive metal strip left between the two water outlets on the cathode end face is positioned directly above the cutter mark. This concentrates the majority of the power supply on the cutter mark, allowing for electrochemical anodic dissolution. Because the cutter mark is lower than the unmachined workpiece surface, meaning that relatively little material needs to be removed, the high power output required for single-groove machining is not required. Therefore, the power output should be reduced in steps 3-2 and 5-2. When the cutter mark is removed in step 3-3, the tool cathode has moved to the midpoint between the end point of the first groove and the starting point of the second groove. To prepare for machining the third groove, the tool cathode must be moved to the starting point of the second groove. This process must avoid damaging the machined surface, so power must be turned off again, similar to step 5-3. This resolves the second challenge that can disrupt flatness in fly-by electrochemical milling: the difficulty of removing cutter marks from multiple tracks. For larger planes, a third groove, a fourth groove, and so on, are needed. Repeat steps 4 and 5. Each additional groove requires one more removal of the joint mark.

[0036] The present invention has the following advantages:

[0037] The present invention is simple, efficient and low-cost. It solves the two major problems that damage the flatness of fly-type electrolytic milling plane processing - poor flatness of a single track and difficulty in removing tool marks between multiple tracks - by simply using a tool cathode whose water outlet profile is determined by a parametric equation. It does not require combined electrodes, auxiliary processes or complex control programs, has a short preparation cycle, high utilization rate and wide applicability.

[0038] Based on the parallel plate electric field distribution theory, the tool cathode of this invention utilizes the shape of the end-face water outlet to adjust the distribution of the metal's conductive area. As the cathode rotates and feeds, the amount of power received from the cathode end face in the vertical direction of the machined groove becomes uniform, significantly improving the flatness of the bottom surface after single-groove machining. Furthermore, when the cathode is stationary, the concentrated power supply between the two water outlets at the cathode end can be used to electrochemically dissolve and remove tool marks at the junction of adjacent grooves, achieving two goals at once. The proposed planar machining method is fast and efficient, with on-demand dissolution, precise positioning, and high machining accuracy.

[0039] The present invention significantly improves the flatness of surfaces produced by fly-by electrochemical milling, making it widely applicable to various difficult-to-cut materials in aerospace, defense, and military applications. Compared to traditional machining, it significantly improves processing efficiency and precision. This significantly promotes the advancement of fly-by electrochemical milling technology and the development of fly-by rotary cathode electrochemical milling applications.

[0040] The above-mentioned tool cathode for improving the flatness of fly-by electrolytic milling plane processing is characterized in that: the outer circle radius R of the above-mentioned tool cathode satisfies R≥3mm, the height H satisfies H≥30mm, the end thickness h1 satisfies R / 18≤h1≤2R / 9, and the inner circle radius r is equal to the larger value of the vertical coordinate of the intersection of the contour of the water outlet in the first quadrant and the y-axis.

[0041] The fly-by electrolytic milling process used in the present invention is generally macro-processing, and for the meso- and micro-scales, surface flatness is not so important, so the cathode radius is not less than 3 mm. The structure of the tool cathode is cylindrical, and its strength is not as good as that of a column. In order to ensure the clamping strength during use, the cathode height H is at least 30 mm. In order to avoid the electric field interference caused by the excessive length of the hole wall of the end water outlet, which increases the difficulty of improving the power supply distribution, the end thickness h1 does not exceed 2R / 9; in order to maintain the structural strength of the cathode end, the end thickness h1 is not less than R / 18. In order to facilitate the manufacture of the tool cathode, the inner circle radius r is equal to the larger value of the vertical coordinate of the intersection of the outline of the water outlet in the first quadrant and the y-axis.

[0042] The above-mentioned tool cathode for improving the flatness of fly-by electrolytic milling plane processing is characterized in that: the thickness of the above-mentioned positioning plate is h2≤3mm, the length E satisfies E≥6mm, and the width F satisfies F≥3mm; the minimum distance between the above-mentioned positioning plate and the end surface of the tool cathode is not less than 6mm.

[0043] Because the positioning piece serves as a visual guide for positioning, it must be sufficiently visible. However, structural rigidity requirements are minimal, so a length E ≥ 6mm and a width F ≥ 3mm are sufficient. However, excessive thickness of the positioning piece will increase positioning errors, so the thickness h2 should be ≤ 3mm. The positioning piece also conducts electricity. To prevent electrolytic reactions from interfering with machining due to proximity to the anode workpiece surface, the minimum distance between the positioning piece and the cathode end of the tool must be at least 6mm.

[0044] The above-mentioned tool cathode for improving the flatness of plane machining by fly-by electrolytic milling is characterized in that the tool cathode material is an acid- and alkali-resistant conductor.

[0045] Because the electrolyte used in electrolytic milling is often corrosive, the tool cathode material should be an acid and alkali corrosion-resistant conductor to increase its service life.

[0046] The above-mentioned method for improving the flatness of a plane processed by fly-by electrolytic milling is characterized in that the feed distance d in the above-mentioned steps 2-1 and 4-1 satisfies 1.7R≤d≤1.9R.

[0047] The single groove processing technology of the present invention has solved the problem of poor flatness of a single track. The proportion of the flat bottom surface of the processed groove to the groove width is significantly improved, the uneven curved side walls are greatly narrowed, and the overlapping area required for secondary processing of these adjacent curved side walls when processing adjacent grooves is also greatly narrowed. Therefore, the offset feed distance (i.e., the span) when processing adjacent grooves in steps 2-1 and 4-1 is significantly increased. By meeting [1.7R, 1.9R], smaller tool marks can be obtained, and the processing efficiency is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 CAD diagram of the tool cathode for improving flatness in fly-by electrochemical milling; (a) is a bottom view, (b) is a half-section front view, (c) is a top view, and (d) is an axonometric view.

[0049] Figure 2 Schematic top view of fly-by electrolytic milling using a rotating cathode; (a) shows the general case of a conventional cathode, and (b) shows the cathode processing of the present invention;

[0050] Figure 3 Schematic diagram of a three-dimensional process for improving the flatness of a surface processed by fly-by electrochemical milling; (a) corresponds to step 1, (b) corresponds to step 2, (c) corresponds to step 3-1, (d) corresponds to step 3-2, (e) corresponds to step 4, (f) corresponds to step 5-1, and (g) corresponds to step 5-2;

[0051] Figure 4Schematic top view of a process for improving the flatness of a surface processed by fly-by electrolytic milling; wherein (a) corresponds to step 1, (b) corresponds to step 2, (c) corresponds to step 3-1, (d) corresponds to step 3-2, (e) corresponds to step 4, (f) corresponds to step 5-1, and (g) corresponds to step 5-2;

[0052] Figure 5 This is the contour diagram after processing using a conventional cathode corresponding to Example 1;

[0053] Figure 6 The contour diagrams of Example 2 after using a cathode to improve the flatness of a fly-by electrochemical milling plane are shown; (a) is a single groove machining case, (b) is a plane machining case, and (c) is a case of removing tool marks;

[0054] Figure 7 The contour diagrams of Example 3 after cathode processing using another method for improving the flatness of fly-by electrochemical milling plane processing are shown; (a) is the case of single groove processing, (b) is the case of plane processing, and (c) is the case of tool mark removal;

[0055] The label names are: 1. workpiece; 2. tool cathode; 3. electrolyte; 4. water outlet; 5. positioning piece; 6. cutting mark; 7. groove. DETAILED DESCRIPTION

[0056] The present invention will be described in further detail below with reference to the accompanying drawings:

[0057] Figure 1 CAD drawing of tool cathode 2 for improving flatness in fly-by electrochemical milling. Figure 1 (a) is a bottom view, Figure 1 (b) is the half-section main view, Figure 1 (c) is a top view, Figure 1 (d) is an axonometric drawing. It can be seen that the tool cathode 2 has a cylindrical structure, with an outer radius of R, an inner radius of r, a height of H, and an end thickness of h1. A rectangular coordinate system is established with the center of the end face as the origin, the axis of the tool cathode 2 as the Z axis, the direction of the uncovered end of the tool cathode 2 pointing to the end face as the positive direction of the Z axis, and the straight lines of the two diameters perpendicular to each other on the end face as the X and Y axes. A pair of normal square positioning pieces 5 are set on the outer circular wall of the tool cathode 2 near the end. The positioning pieces 5 have a thickness of h2, a length of E, and a width of F. The two positioning pieces 5 are mirror-symmetrical about the YZ plane, and each positioning piece 5 itself is mirror-symmetrical about the XZ plane, as shown in FIG. Figure 1Furthermore, the positioning piece 5 is also made of conductive material. To avoid electrolytic reaction from interfering with machining due to being too close to the surface of the anode workpiece 1, the minimum distance between the positioning piece 5 and the end face of the tool cathode 2 should be no less than 6 mm.

[0058] like Figure 1 As shown in (c), the two water outlets 4 are mirror-symmetrical about the XZ plane, and the water outlet 4 itself is mirror-symmetrical about the YZ plane. The outline of the water outlet 4 in the first quadrant is determined by the parametric equation. The outline of the water outlet 4 in the second quadrant is symmetrical with the outline in the first quadrant. The outline of the other water outlet 4 in the third and fourth quadrants is symmetrical with the second and first quadrants respectively. In this way, the entire outline of the two water outlets 4 can be determined by only determining the outline in the first quadrant through the parametric equation. Obviously, there are two intersection points between the water outlet 4 in the first and second quadrants and the positive half axis of the y-axis, and the vertical coordinate of the intersection point close to the axis center of the tool cathode 2 is determined by a, as shown in the figure. Figure 1 (a) To reduce the amount of power supplied to the center of the machined groove and ensure the parametric equation's effectiveness in improving power distribution uniformity, a cannot exceed R / 18. To avoid the tip effect and maintain the structural strength of the tool cathode 2 end face, a cannot be less than R / 90. The ordinate of the other intersection with the positive y-axis, the larger ordinate, is equal to the inner circle radius r. This facilitates manufacturing of the tool cathode 2 and reduces process steps.

[0059] A top view of electrochemical milling using a rotating cathode Figure 2 On the surface of the machined groove, a dotted line is drawn perpendicular to the feed direction to represent the cross section of the machined groove. When the rotating cathode represented by the shadow flies from the right side of the dotted line to the left side of the dotted line, the machining of the cross section is completed. Figure 2 (a) represents the general case. The time for processing point O at the center of the machining groove on the dotted line is equal to the length of the line segment O1O2 divided by the feed speed v jj The time for processing point P on the dotted line at the edge of the processing groove is equal to the length of the line segment P1P2 divided by the feed speed v jj At the same feed rate, line segment O1O2 is longer than line segment P1P2, so point O is machined for a longer period of time. This means that the center area of ​​the rotating cathode supplies more power to the corresponding middle area of ​​the machined groove. Consequently, more material is removed from the middle area of ​​the machined groove by the electrochemical anode, resulting in a deeper machining depth. As a result, the machining depth of the machined groove gradually decreases from the center to the sides, forming an arc-shaped profile. This explains the poor flatness of individual tracks after using a rotating cathode for fly-by electrochemical milling.

[0060] To address the issue of poor single-track flatness, the following calculations are performed. First, the bottom surface of the rotating cathode is simplified to a circle, temporarily ignoring edge effects. Next, the feed rate is assumed to be so high that the material removal depth at the anode is negligible. This simplifies the electric field between the cathode and cathode to a parallel plate field, and the resistance in the machining gap is uniform everywhere. Since machining time cannot be changed, the key to improving single-track flatness lies in improving the distribution of power supplied per unit time to the bottom surface of the tool cathode 2. This fundamentally changes the conventional thinking that the projected area of ​​the anode surface directly facing the cathode bottom receives an equal amount of power. As long as the circular bottom surface of the tool cathode 2 has a water outlet 4, it will inevitably reduce the conductive metal area, which means that the current density on the anode surface facing it will inevitably be zero. Therefore, for a rotating cathode, this zero-current-density area must reduce the sum of the current densities of the entire circle of the same radius on the anode surface. When the rotation speed of the tool cathode 2 is fast enough, the circular projection of the circular bottom surface of the tool cathode 2 on the anode surface also rotates at a high speed. It can be understood that the circular projection is still complete, and the current density on the entire circle of the same radius on the anode surface is still equal, but it is smaller than the current density of other projection areas on the anode surface without water outlets. In this way, it can be assumed that the anode current density i in the circular projection area is differentiated by radius, that is, the current density on a circle of any radius is equal everywhere, and the current density on concentric circles of different radii may be different, and the n radii are subdivided into R1, R2, R3,..., R n The concentric circles correspond to current densities i1, i2, i3, ······, i n The line segment P1P2 of the processing process of a certain point P on the dot-dash line is the section of countless concentric circles of different radii, which has experienced the corresponding anode current density. Let the distance between a certain point P on the dot-dash line and the axis of the processing groove be k (i.e. Figure 2 The distance between the center of the shaded circle in a and the line segment P1P2 is k). The amount of electricity received by this point during the entire machining process is Q(k) = ∫i(k)dt, which is the integral of the product of the anode current density value of each concentric circle intercepted by the line segment P1P2 and its corresponding action time. Because the feed speed v is the same everywhere, and the time so L is the length of each anode current density, that is, the length of the overlap between the circle corresponding to each anode current density and the line segment P1P2. According to Faraday's law, the anode material at the groove position of point P is corroded. μ is the mass electrochemical equivalent, η is the current efficiency. Combined with the circle section calculation formula, it can be expanded Because Δi is very small, in order to improve the flatness and obtain a balanced relationship between corrosion quality and groove position, the anode current density i should be The function based on w1 and w2 are known parameters. Also, because it was previously assumed that the anode current density i in the circular projection area is differentiated according to the radius, but in reality, the anode current density in the projection area opposite the complete circular bottom plane of the tool cathode 2 is uniform and consistent, and it is impossible to really change according to the radius. To achieve this, we can only change the shape of the bottom plane of the tool cathode 2 and the distribution of the metal material, that is, by arranging the water outlet 4 to change the arc length of the metal material of different radii of the tool cathode. In this way, after the tool cathode 2 rotates, due to the different arc lengths, the current density of the concentric circles of each radius in the projection area opposite the anode surface is different. When the rotation speed is fast enough, the projection area of ​​the anode surface also rotates at high speed. It can be understood that the current density at various points on the entire circle of the same radius is still equal but has decreased. In this way, the change of current density with radius is converted into the change of arc length of the remaining metal material on the bottom surface of the tool cathode 2 with radius, and Convert to arc length Then perform polar coordinate transformation to obtain the remaining metal material profile parameter equation In order to control the low power supply at the center of the bottom surface of the tool cathode 2, the relationship between w1 and w2 is obtained from the simulation: w1 / R-w2=a, and w2=b, so the parametric equation becomes The value range of the known number a is [R / 90, R / 18], and the value range of the known number b is [0.5R, 0.8R].

[0061] Figure 2 (b) is a top view of the tool cathode 2 during machining using a fly-by electrochemical milling method to improve flatness. Using rigorously derived parametric equations, the end face of the tool cathode 2 determines the shape and contour of the water outlet holes 4 and the distribution of the remaining conductive metal area. Therefore, as the tool cathode 2 rotates and flies over the dotted line, once the relative projections of the two water outlet holes 4 overlap point O, no power is supplied, pausing electrochemical dissolution. The closer to the center of the tool cathode 2 end face, the less conductive metal area there is. Consequently, the power supply to the center of the machined groove (represented by point O) is significantly reduced during the rotational feed of the tool cathode 2. The closer to the edge of the tool cathode 2 end face, the more conductive metal area there is, ensuring sufficient power supply to the edges of the machined groove during the rotational feed of the tool cathode 2. Therefore, the power supply distribution of the traditional rotating cathode, which generally decreases from the center to the sides, is reversed. The power supply received by the tool cathode 2 end face in the vertical direction of the machined groove becomes more uniform, resulting in a more consistent material removal from the center to the sides of the machined groove, significantly improving flatness.

[0062] Figure 3 A three-dimensional schematic diagram of the process method for improving the flatness of a surface by electrochemical fly-milling. Figure 4A schematic diagram of a top view of a process for improving the flatness of a surface by electrochemical milling. Step 1 (first groove machining) Figure 3 As shown in (a) and 4(a), the moment when the first groove is processed is selected. According to the single groove processing process, the tool cathode 2 is connected to the negative pole of the power supply, and the workpiece 1 is connected to the positive pole of the power supply. The end face of the tool cathode 2 is always higher than the upper surface of the workpiece 1. The electrolyte 3 is injected into the tool cathode 2 from top to bottom through the spindle, and then sprayed onto the surface of the workpiece 1 through the water outlet 4 and overflowed and diffused in all directions, filling the processing gap between the tool cathode 2 and the workpiece 1, forming a conductive circuit. The spindle drives the tool cathode 2 while v xz The speed of rotation is v jj The tool is fed forward at a speed of 1 / 4, electrochemically dissolving the surface of the workpiece 1 from the starting point to the end point of the first groove. The shape of the water outlet 4 on the end face of the tool cathode 2 adjusts the distribution of the metal's conductive area, ensuring a uniform power supply from the end face of the tool cathode 2 in the vertical direction of the machined groove. This results in a uniform amount of material removal from the center to both sides of the machined groove, resulting in a smooth bottom surface after machining.

[0063] Step 2 (second groove processing) Figure 3 As shown in (b) and 4(b), the figure selects the moment when the adjacent groove processing is completed and the process returns to the starting point of the first groove. After the first groove processing is completed, the spindle drives the tool cathode 2 to keep rotating and feed a distance d along the normal direction of the first groove processing direction, processing from the end point of the first groove to the starting point of the adjacent second groove. Then the second groove is continuously fed in the opposite direction of the first groove processing direction to reach the end point of the second groove. Then it is fed back to the starting point of the first groove along the normal direction of the second groove processing direction to complete the processing of the adjacent second groove. The single groove processing technology has solved the problem of poor flatness of a single track. The width of the flat bottom surface of a single groove in the vertical feed direction becomes wider, while the width of the inclined and curved part decreases, that is, the part of a single groove that can be retained without secondary processing becomes wider, and the part that requires secondary processing is reduced. Therefore, when machining adjacent grooves in step 2, the normal feed distance d (i.e., the span) along the machining direction of the first groove is significantly increased to meet the requirements of [1.7R, 1.9R], significantly improving machining efficiency. However, after secondary machining of the adjacent inclined and curved sidewalls of the grooves, some sidewall material will still remain at the junction of the two grooves, which is the raised cutting mark 6.

[0064] The cross section of the joint mark 6 is very similar to a triangle, except that the two sides are arcs instead of straight lines; and the joint mark 6 is straight as a whole and parallel to the direction of the groove. In order to remove the joint mark 6, the present invention clearly defines the distribution of the metal conductive area with a diameter of the end face (i.e., the X-axis) as the axis when designing the end face of the tool cathode 2, so the two water outlets 4 are mirror-symmetrical about the XZ plane, and the entire tool cathode 2 is mirror-symmetrical about the XZ plane. The remaining conductive metal in the middle of the two water outlets 4 on the end face of the tool cathode 2 surrounds the X-axis to form a conductive metal strip. Its shape is narrow in the middle and wide on both sides, which improves the power supply distribution during the rotational feeding process, and can concentrate the electric field distribution below the X-axis when it is not rotating, which is very suitable for processing straight joint marks 6. Therefore, the first thing is to position the conductive metal strip vertically above the joint mark 6 so that most of the power supply can be concentrated on the joint mark 6, as shown in step 3-1 (joint mark 6 tool alignment). Figure 3 (c) and 4(c). The power supply is turned off to avoid re-processing during the positioning process. The spindle drives the tool cathode 2 to move to the midpoint between the starting point of the first groove and the end point of the second groove. After the positioning piece 5 of the tool cathode 2 is turned to a position parallel to the cutting mark 6, the spindle stops rotating and the positioning is completed. Figure 3 The moments selected in (c) and 4(c) are the moments when the positioning is completed and the rotation stops.

[0065] Step 3-2 (removing the knife mark 6) Figure 3 (d) and 4(d). Because the height of the butt mark 6 is lower than the unprocessed surface of the workpiece 1, that is, the material to be removed at the butt mark 6 is relatively small, the power output is reduced before power is turned on. The spindle no longer rotates to ensure that the positioning piece 5 of the tool cathode 2 is aligned parallel to the butt mark 6 and feeds along the butt mark 6. The concentrated power supply between the two water outlets 4 of the tool cathode 2 is used to complete the electrochemical dissolution removal of the butt mark 6, significantly improving the flatness of the bottom surfaces of the two adjacent grooves. Figure 3 The moments selected in (d) and 4(d) are just after the removal of the cutting mark 6. After the cutting mark 6 is removed, the power is turned off and the spindle drives the tool cathode 2 back to the starting point of the second groove to prepare for subsequent processing.

[0066] Step 4 (Other adjacent groove processing) Figure 3(e) and 4(e). After the power output is restored, the power is turned on, and the spindle drives the tool cathode 2 to keep rotating and feed a distance d along the normal direction of the second (N=2) groove processing direction, that is, from the starting point of the second (N=2) groove to the starting point of the adjacent third (N+1=3) groove. Then, along the same direction of the second (N=2) groove processing direction, process from the starting point of the third (N+1=3) groove to the end point of the third (N+1=3) groove. Then, feed from the end point of the third (N+1=3) groove back to the end point of the second (N=2) groove along the normal direction of the third (N+1=3) groove processing direction, completing the processing of the third (N+1=3) groove. The moment selected in the figure is just when the third groove processing is completed and returned to the end point of the second groove. Step 5-1 (tool alignment after connecting tool mark 6) as shown Figure 3 (f) and 4(f). The power supply is turned off to avoid re-processing during the positioning process. The spindle drives the tool cathode 2 to move to the midpoint between the end point of the second (N=2) groove and the end point of the third (N+1=3) groove. After the positioning piece 5 of the tool cathode 2 is turned to a position parallel to the cutting mark 6, the spindle stops rotating and the positioning is completed. Figure 3 The moment selected in (f) and 4(f) is the moment when the positioning stops. Figure 3 (g) and 4(g) show the moment when the joint mark 6 has just been removed. The process is identical to step 3-2. After the joint mark 6 is removed, the power is turned off, and the spindle drives the tool cathode 2 back to the starting point of the third (N+1=3) groove, preparing for subsequent machining. Steps 4 and 5 are then repeated, performing fly-by electrochemical milling by combining adjacent grooves and removing the joint mark 6 at their intersections.

[0067] The following is a comparison of the embodiments. The three types of rotating cathodes selected in the embodiment of the present invention have an outer radius R of 9 mm and a height H of 60 mm. Figure 5 、 Figure 6 (a) Figure 7 (a) The left side is shown in the actual picture. Example 1 is a conventional cathode, such as Figure 5 As shown on the left, the radius of its seven water holes is 1mm. In the past, fly-by electrolytic milling processing used this kind of conventional cathode with small and dispersed opening area. The small opening area has almost no effect on the metal conductive area and electric field distribution on the bottom surface of the conventional cathode, and the power supply distribution is also consistent. Figure 2 (a) is the same. Example 2 is a tool cathode 2 for improving the flatness of a fly-by electrolytic milling surface. Figure 6 (a) As shown on the left, the end thickness h1 = 2R / 9 = 2mm, the known number a = R / 18 = 0.5, the known number b = 0.8R = 7.2, the contour of the water outlet 4 in the first quadrant satisfies the parametric equation The positioning piece 5 has a thickness of h2 = 0.5 mm, a length of E = 6 mm, and a width of F = 5 mm. Figure 7 (a) As shown on the left, the end thickness h1 = R / 18 = 0.5 mm, the known number a = R / 90 = 0.1, the known number b = 0.5R = 4.5, the contour of the water outlet 4 in the first quadrant satisfies the parametric equation The positioning piece 5 has a thickness of h2 = 0.5 mm, a length of E = 6 mm, and a width of F = 5 mm. Three different tool cathodes 2 were tested to clearly compare the actual surface flatness achieved. The test parameters were as follows: electrolyte 3 was a 20% NaCl solution, temperature was 30°C, and electrolyte pressure was 0.2 MPa. Tool cathode 2 was made of 304 stainless steel, and anode workpiece 1 was made of 7075 aluminum alloy. Tool cathode 2 rotation speed was 500 rpm, feed rate was 60 mm / min, machining gap was 0.2 mm, and machining voltage was 30 V.

[0068] Example 1:

[0069] This embodiment uses a conventional cathode. Because the area of ​​the seven water outlet holes is small, the electric field distribution on the bottom surface of the conventional cathode is still uneven. The power supply per unit area perpendicular to the feed direction decreases from the middle to the sides. Correspondingly, the amount of material dissolved by the electrochemical anode is more in the middle and less on the sides. Naturally, the processing depth is deep in the middle and shallow on the sides, presenting an arc-shaped profile. Figure 5 As shown in the cross-sectional profile on the right, the machined surface flatness is very poor, with a bottom height difference of 0.18mm.

[0070] Example 2:

[0071] This embodiment uses a tool cathode 2 that improves the flatness of a fly-by electrolytic milling surface. The bottom surface of the groove it finally processes is relatively flat, very close to the surface profile of a mechanical milling process, such as Figure 6 (a) The cross-sectional profile on the right shows that the bottom height difference is only 0.027mm, which is only about 1 / 6 of that of a conventional cathode. The cross-sectional profile after processing three adjacent grooves with a normal feed (span) of d = 16.5mm is shown in the figure below. Figure 6 As shown in (b), the bottom height difference is 0.071mm, which is exactly the height of the cutting mark 6. At this time, the cutting mark 6 becomes the main factor that destroys the flatness. The cross-sectional profile after the cutting mark 6 is removed according to the process method of this patent is as follows Figure 6 As shown in (c), the bottom surface height difference is reduced to 0.033 mm, which is close to the bottom surface height difference of a single groove, indicating that the effect of removing the cutting mark 6 is very obvious.

[0072] Example 3:

[0073] This embodiment uses another tool cathode 2 to improve the flatness of the fly-through electrochemical milling plane. The bottom surface of the groove it finally processes is also relatively flat, such as Figure 7 (a) The cross-sectional profile on the right shows that the bottom height difference is only 0.021mm, which is only about 1 / 9 of that of a conventional cathode. The cross-sectional profile after processing three adjacent grooves with a normal feed (span) of d = 16.5mm is shown in the figure below. Figure 7 As shown in (b), the bottom height difference is 0.049mm, which is exactly the height of the cutting mark 6. At this time, the cutting mark 6 becomes the main factor that destroys the flatness. The cross-sectional profile after the cutting mark 6 is removed according to the process method of this patent is as follows Figure 7 As shown in (c), the bottom surface height difference is reduced to 0.026mm, which is close to the height difference of a single groove bottom surface, demonstrating that the present invention is very effective in removing the joint mark 6. In summary, the present invention effectively and quickly solves the two major problems that undermine the flatness of fly-by electrochemical milling surfaces—the poor flatness of individual tracks and the difficulty in removing the joint marks 6 of multiple tracks—significantly improving the flatness of fly-by electrochemical milling surfaces.

[0074] The present invention proposes a tool cathode 2 and method for improving the flatness of fly-by electrolytic milling plane processing, and uses the shape design of the water outlet 4 on the end face of the tool cathode 2 to adjust the distribution of the metal conductive area. When the tool cathode 2 is rotated and fed, the power supply received from the end face of the tool cathode 2 in the vertical direction of the processing groove tends to be consistent, which greatly improves the flatness of the bottom surface after single groove processing; and when the tool cathode 2 is not rotating, the concentrated power supply between the two water outlets 4 on the end of the tool cathode 2 can be used to complete the electrochemical dissolution and removal of the tool mark 6 at the junction of adjacent grooves, killing two birds with one stone. However, the above description cannot be understood as a limitation of the patent of the present invention. It should be noted that, without departing from the concept of the present invention, several improvements can be made, and these should all fall under the protection of the patent of the present invention.

Claims

1. A tool cathode for improving the flatness of a surface during fly-by electrochemical milling, characterized in that: The tool cathode (2) has a cylindrical structure, with an outer radius of R, an inner radius of r, a height of H, and an end thickness of h1; a rectangular coordinate system is established with the center of the end face as the origin, the axis of the tool cathode (2) as the Z axis, the direction of the end face of the tool cathode (2) without a cover as the positive direction of the Z axis, and the straight lines of two mutually perpendicular diameters on the end face as the X and Y axes; A pair of normal square positioning pieces (5) are provided on the outer circular wall of the tool cathode (2) near the end, the two positioning pieces (5) are mirror-symmetrical about the YZ plane, and each positioning piece (5) itself is mirror-symmetrical about the XZ plane; the thickness of the positioning piece (5) along the Y axis is h2; the length of the positioning piece (5) along the Z axis is E; the width of the positioning piece (5) along the X axis is F; The cathode (2) of the tool is provided with a pair of water outlet holes (4), the wall of the water outlet hole (4) is always perpendicular to the end face, the two water outlet holes (4) are mirror-symmetrical about the XZ plane, and each water outlet hole (4) itself is mirror-symmetrical about the YZ plane; the contour of the water outlet hole (4) in the first quadrant of the XY plane satisfies the parametric equation The known number a in the parametric equation satisfied by the outline of the water outlet (4) in the first quadrant determines the smaller value of the ordinate of the intersection of the outline of the water outlet (4) and the y-axis, and the value range of a is [R / 90, R / 18]; and the known number b determines the curvature of the outline of the water outlet (4) in the first quadrant, and the value range of b is [0.5R, 0.8R]; k is an independent variable.

2. The tool cathode for improving the flatness of a surface during fly-by electrochemical milling according to claim 1, characterized in that: The outer radius R of the tool cathode (2) satisfies R≥3mm, the height H satisfies H≥30mm, the end thickness h1 satisfies R / 18≤h1≤2R / 9, and the inner radius r is equal to the larger value of the ordinate of the intersection of the contour of the water outlet (4) in the first quadrant and the y-axis.

3. The tool cathode for improving the flatness of a surface during fly-by electrochemical milling according to claim 1, characterized in that: The thickness of the positioning piece (5) is h2≤3mm, the length E satisfies E≥6mm, and the width F satisfies F≥3mm; the minimum distance between the positioning piece (5) and the end face of the tool cathode (2) is not less than 6mm.

4. The tool cathode for improving flatness in fly-by electrochemical milling according to claim 1, characterized in that: The tool cathode (2) is made of a material that is an acid and alkali corrosion-resistant conductor.

5. A method for machining a tool cathode for improving the flatness of a fly-by electrolytic milling surface according to claim 1, characterized in that The following processes are included: Single groove processing technology: the tool cathode (2) is installed on the main spindle of the machine tool and connected to the negative pole of the power supply; the workpiece (1) is installed in the worktable of the machine tool and connected to the positive pole of the power supply; the end face of the tool cathode (2) is always higher than the upper surface of the workpiece (1); the electrolyte (3) is injected into the tool cathode (2) from top to bottom through the main spindle, and then sprayed onto the surface of the workpiece (1) through the water outlet (4) and overflowed and diffused in all directions, filling the processing gap between the tool cathode (2) and the workpiece (1) to form a conductive circuit; the main spindle drives the tool cathode (2) to rotate and feed forward at the same time, and electrochemically dissolves the surface of the workpiece (1); the end face of the tool cathode (2) uses the shape design of the water outlet (4) to adjust the distribution of the metal conductive area, so that the power supply received from the end face of the tool cathode (2) in the vertical direction of the processing groove tends to be consistent, so the flatness of the bottom surface of the groove after processing is greatly improved; Specific processing steps: Step 1, first groove processing: the tool cathode (2) keeps rotating and feeds from the starting point of the first groove to the end point of the first groove, and processes the first groove according to the single groove processing process; Step 2: Processing the second groove: 2-1, the tool cathode (2) keeps rotating and feeds a distance d along the normal direction of the first groove processing direction, that is, processing from the end point of the first groove to the starting point of the adjacent second groove; 2-2. According to the single groove processing process, the tool cathode (2) keeps rotating and processes the second groove from the starting point to the end point of the second groove in the opposite direction of the processing direction of the first groove; 2-3. The tool cathode (2) keeps rotating and feeds back from the end point of the second groove to the starting point of the first groove along the normal direction of the second groove processing direction, thereby completing the processing of the second groove; Step 3: Processing the cutting marks of the first and second grooves: 3-1. Tool setting at the tool mark (6): The power is turned off, and the spindle drives the tool cathode (2) to move from the starting point of the first groove to the midpoint between the starting point of the first groove and the end point of the second groove. After the positioning piece (5) of the tool cathode (2) moves to a position parallel to the tool mark (6), the spindle stops rotating; 3-2. Removal of the butt joint mark (6): After reducing the power output and then turning on the power, the spindle no longer rotates to ensure that the positioning piece (5) of the tool cathode (2) is aligned parallel to the butt joint mark (6), and feeds along the butt joint mark (6). The concentrated power supply between the two water outlets (4) of the tool cathode (2) is used to complete the electrochemical dissolution removal of the butt joint mark (6), which significantly improves the flatness of the bottom surfaces of the two adjacent grooves; 3-3. After the cutting mark (6) is removed, the power supply is turned off, and the spindle drives the tool cathode (2) to move back to the starting point of the second groove; Step 4: Processing of other adjacent grooves: 4-1. The groove that has just been processed is called the Nth groove, where N≥2; after the power output is restored, the power is turned on, and the tool cathode (2) keeps rotating and feeds a distance d along the normal direction of the processing direction of the Nth groove, that is, processing from the starting point of the Nth groove to the starting point of the adjacent N+1th groove; 4-2. According to the single groove processing process, the tool cathode (2) keeps rotating and processes from the starting point of the N+1 groove to the end point of the N+1 groove in the same direction as the processing direction of the Nth groove; 4-3. The tool cathode (2) keeps rotating and feeds back from the end point of the N+1th groove to the end point of the Nth groove along the normal direction of the machining direction of the N+1th groove, thereby completing the machining of the N+1th groove; Step 5: Processing of cutting marks of other adjacent grooves: 5-1. Tool alignment at the tool mark (6): The power is turned off, and the spindle drives the tool cathode (2) to move from the end point of the Nth groove to the midpoint between the end points of the Nth groove and the N+1th groove. After the positioning piece (5) of the tool cathode (2) moves to a position parallel to the tool mark (6), the spindle stops rotating. 5-2. Removal of the butt joint mark (6): After reducing the power output and then turning on the power, the spindle no longer rotates to ensure that the positioning piece (5) of the tool cathode (2) is aligned parallel to the butt joint mark (6), and feeds along the butt joint mark (6). The concentrated power supply between the two water outlets (4) of the tool cathode (2) is used to complete the electrochemical dissolution removal of the butt joint mark (6), which significantly improves the flatness of the bottom surface of the adjacent grooves; 5-3. After the cutting mark (6) is removed, the power supply is turned off, and the spindle drives the tool cathode (2) to move back to the starting point of the N+1 groove; Step 6, repeat steps 4 and 5 to process the plane: after the power output is restored, power on and repeat the above steps 4 and 5, so as to perform fly-by electrolytic milling plane processing by combining adjacent grooves and removing the cutting marks (6) at their junctions.

6. The method for improving the flatness of a surface processed by fly-by electrochemical milling according to claim 5, characterized in that: The feeding distance d in the above steps 2-1 and 4-1 satisfies 1.7R≤d≤1.9R.

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