Process method for electrolytic milling with an extremely small machining gap achieved by a counter-electrode

Abstract

The present invention relates to a process method for realizing electrolytic milling with an extremely small machining gap by means of a reverse-copy electrode, belonging to the field of electrolytic machining. The present invention proposes to trim the sharp right angle at the bottom of a rectangular electrode into a smooth rounded corner through reverse-polarity reverse-copy machining to eliminate the region where the current density distribution is concentrated. The trimmed structure also reduces the hydrodynamic loss caused by the sudden change in the flow velocity and direction of the electrolyte at the liquid outlet hole, significantly improving the flow velocity of the electrolyte in the machining gap and the ability to efficiently discharge the products, and simply and efficiently realizing electrolytic milling with an extremely small machining gap. The extremely small machining gap greatly reduces the inter-electrode resistance, and also helps to locate the machining current and evenly increase the overall current density, promoting the improvement of the electrolytic milling processing efficiency, the machining surface quality and the machining accuracy.

Description

Technical Field

[0001] The present invention relates to a process method for realizing electrolytic milling with an extremely small machining gap by using a counter-copy electrode, and belongs to the field of electrolytic machining. Background Technique

[0002] Electrolytic milling is a special machining technology that uses a simple rectangular cathode to electrolytically machine the surface of a workpiece in a machining manner similar to numerical control milling. The tool cathode scans and moves on the surface of the workpiece according to a specified numerical control program, and the electrolyte mostly flows rapidly into the machining gap in the form of internal spraying, forming a conductive circuit between the tool cathode and the workpiece, and the surface material of the workpiece undergoes an electrochemical reaction and is dissolved and removed. Macroscopic electrolytic milling can achieve directional machining and material removal of a specified small area on the surface of the workpiece, with good machining flexibility, wide adaptability, low tool cost, and short design and manufacturing cycle. Therefore, the macroscopic electrolytic milling technology has attracted the widespread attention of scholars at home and abroad, and research has been carried out one after another.

[0003] The machining gap is the most important factor directly determining the machining accuracy and efficiency of macroscopic electrolytic milling. The resistance in the machining gap decreases linearly with its distance. A small machining gap can significantly reduce the resistance. During machining, only less electric energy is required to overcome the resistance, greatly reducing the power consumption. Moreover, a small machining gap helps to position the machining current and increase the overall current density, which can improve the machining accuracy and surface quality and reduce stray corrosion to protect the non-machined area. This is different from applying a high voltage to obtain a high current density. During the process of simply applying a high voltage, the machining gap is relatively large, inevitably resulting in a large resistance and wasting electric energy; and due to the edge effect, the low current density area outside the machining gap will also expand, making the stray corrosion more serious. Therefore, the effect of a small machining gap is unique, and creating an extremely small machining gap is very attractive for realizing precise and efficient electrolytic milling.

[0004] Under the existing macroscopic electrolytic milling machining conditions, the machining gap is usually greater than 0.2 mm. Further reducing the machining gap is a huge challenge. Usually, discharges and sparks will occur to disorderly damage the cathode and anode, forcing the machining to stop. The too-high current density and too-concentrated distribution in the tip region of the tool cathode are the primary factors directly increasing the risk of sparks and discharges. According to the electric field characteristics, the current density concentrated in the sharp right-angle region is usually several times that of other regions. When the machining gap is further reduced, the current density in these sharp right-angle regions will surge rapidly and quickly reach the critical point of discharge and spark, thus causing uncontrollable damage to the cathode and anode.

[0005] In addition, reducing the machining gap conflicts with the requirement of efficient product transportation and discharge during the machining process. Because it increases the hydrodynamic losses and significantly reduces the flow velocity of the electrolyte within the machining gap. As a result, a large amount of electrolytic products generated by the high machining current cannot be discharged in time and accumulate continuously in the machining gap, further promoting the generation of sparks and discharges, causing uncontrollable damage to the cathode and anode. Moreover, most of the electrolytic products that cannot be discharged can only remain on the machining surface, seriously affecting the machining accuracy and damaging the machining surface quality. Increasing the electrolyte injection pressure is the simplest and most common method to increase the flow velocity and product discharge capacity in electrolytic milling. However, high injection pressure will also cause continuous cavitation at the sharp edges of the tool cathode, greatly reducing the machining efficiency and affecting the machining performance. Therefore, to achieve an extremely small machining gap during machining, it is necessary to overcome the problems of excessively high and concentrated local current density and difficult discharge of accumulated machining products. Summary of the Invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention designs a process method for electrolytic milling with an extremely small machining gap by using a reverse-copy electrode. By reversing the polarity and reverse-copying to trim the tool electrode, the concentrated area of current density distribution is eliminated. At the same time, the shape of the liquid outlet holes of the tool electrode is improved to accelerate the flow velocity within the machining gap and enhance the product transportation and discharge capacity, ultimately achieving electrolytic milling with an extremely small machining gap.

[0007] A process method for electrolytic milling with an extremely small machining gap by using a reverse-copy electrode, characterized by including the following processes:

[0008] Step 1. Reverse-copy preparation: The rectangular electrode vertically clamped on the machine tool spindle is connected to the positive pole of the DC power supply, and the horizontally placed workpiece is connected to the negative pole of the DC power supply. The machining gap between the bottom surface of the rectangular electrode and the workpiece surface is controlled to be H by the spindle. The electrolyte flows into the rectangular electrode from the liquid inlet hole at the top of the rectangular electrode through the spindle, then flows out from the liquid outlet hole at the bottom of the rectangular electrode to the workpiece surface, and finally discharges outward through the machining gap between the bottom surface of the rectangular electrode and the workpiece surface;

[0009] Step 2. Reverse-copy machining of the rectangular electrode: The DC power supply maintains a constant current, the rectangular electrode and the workpiece are energized, and the material at the bottom of the rectangular electrode undergoes electrochemical anodic dissolution. Since the current density is the highest and the distribution is the most concentrated, the outermost pair of symmetric outer right angles at the bottom of the rectangular electrode and the pair of symmetric inner right angles on both sides of the liquid outlet holes at the bottom of the rectangular electrode are the main dissolution areas of the electrode material, and are respectively dissolved into a pair of outer rounded corners and a pair of inner rounded corners until the width of the bottom surface of the rectangular electrode between the outer rounded corners and the inner rounded corners is reduced to 50% - 75% of the original, the current density distribution becomes dispersed and the concentrated area is completely eliminated, and the DC power supply is powered off;

[0010] Step 3. Process condition adjustment: The trimmed rectangular electrode is controlled by the main shaft to move downward, and the machining gap between the electrode and the workpiece surface is reduced to a minimum machining gap h. The trimmed rectangular electrode is connected to the negative pole of the DC power supply, while the workpiece is connected to the positive pole of the DC power supply, and the electrolyte is continuously supplied and flowing.

[0011] Step 4. Electrochemical milling with minimum machining gap: The trimmed rectangular electrode and the workpiece are energized, and the main shaft controls the rectangular electrode to feed along a preset trajectory. The workpiece material then undergoes electrochemical anodic dissolution. The flow rate of the electrolyte within the minimum machining gap below the trimmed rectangular electrode remains very high, sufficient to quickly carry away the electrolytic products and bubbles generated by the electrochemical reaction. At the same time, the concentrated area of the current density distribution within the machining gap is eliminated, thus avoiding damage to the electrochemical milling process such as sparks and short circuits, and realizing electrochemical milling with a minimum machining gap.

[0012] In step 2 of the present invention, the bottom of the rectangular electrode that undergoes electrochemical anodic dissolution can be divided into a pair of outermost symmetric outer right angles, a pair of symmetric inner right angles on both sides of the liquid outlet holes, and a pair of flat bottoms between the inner and outer right angles. According to the electric field tip effect, the electric field in the inner right angle and outer right angle regions is the strongest, the current density is the highest and the distribution is the most concentrated, the electrolytic reaction is the most intense, and the most electrode material is dissolved. Keeping the DC power supply at a constant current all the time is to ensure precise positioning and preferential dissolution of the regions with concentrated current density near the inner and outer right angles, relatively reducing the dissolution of the material near the flat bottom, quickly and efficiently trimming the original sharp inner and outer right angles into smoothly transitioning inner and outer rounded corners, and rapidly dispersing the current density distribution to eliminate the high current density values. This process method is convenient and efficient, precisely locates the high current density region using the electric field properties, dissolves as needed, has no unnecessary electrode loss, and is applicable to electrodes made of any acid and alkali resistant conductive material. Moreover, when the sharp inner right angle is trimmed into a smoothly transitioning inner rounded corner, the liquid outlet hole of the rectangular electrode becomes a gradually changing flared opening, significantly reducing the hydrodynamic loss caused by the sudden change in the flow rate and direction of the electrolyte at the original inner right angle, and greatly increasing the flow rate of the electrolyte within the machining gap. Thus, during the electrochemical milling with a minimum machining gap in step 4, the flow rate within the gap is still sufficient to quickly carry away the electrolytic products and bubbles generated by the electrochemical reaction. In this way, the trimmed rectangular electrode simultaneously overcomes the problems of excessive local current density, too concentrated distribution, and difficulty in discharging the product accumulation in the minimum machining gap. The method is ingenious and the effect is remarkable.

[0013] The process method for the reverse copy electrode to achieve electrochemical milling with a minimum machining gap is characterized in that: the rectangular electrode material is an acid and alkali resistant conductive body; the electrolyte is a salt solution of water-based and organic solvents with a concentration of 1% - 50%, and the amount of electricity provided by the DC power supply for reverse copy trimming of the rectangular electrode in the above step 2 is about 10 - 5000 C.

[0014] The present invention has a wide range of applications and is applicable to salt solutions of water-based and organic solvents with different concentrations, different compositions, and different conductivities. The concentration range of single or mixed solutions composed of commonly used sodium fluoride, sodium nitrate, sodium chloride, sodium chlorate, etc. is 1% - 50%. Even if the solution has a low concentration and low conductivity, as long as the DC power supply provides sufficient electric quantity, reverse copying and trimming can be completed. The electric quantity range matching the concentration range is 10 - 5000 C.

[0015] The process method for electrolytic milling with an extremely small machining gap realized by the above-mentioned reverse copying electrode is characterized in that: the outer fillet of the rectangular electrode after trimming in the above step two has a larger curvature than the inner fillet.

[0016] Because at the bottom of the rectangular electrode, the inner right angle is located on both sides of the liquid outlet hole, and the flowing electrolyte is clean and sufficient; the outer right angle is located at the outermost side of the machining gap, and the flowing electrolyte is relatively less and carries products. Therefore, the electrolytic reaction rate near the inner right angle is relatively fast, more material is dissolved, and the curvature after trimming for the same time is larger.

[0017] The process method for electrolytic milling with an extremely small machining gap realized by the above-mentioned reverse copying electrode is characterized in that: the machining gap H for the above general electrolytic milling is 0.2 - 0.5 mm; the extremely small machining gap h is 0.05 - 0.1 mm.

[0018] When the machining gap H for general electrolytic milling is less than 0.2 mm, arcing will occur between the anode and the cathode, damaging the machining process. When it exceeds 0.5 mm, the positioning of the machining current is too poor, resulting in poor machining accuracy and surface quality. An extremely small machining gap h less than 0.1 mm is difficult to achieve by general electrolytic milling. Among them, the 0.05 mm extremely small machining gap realized by the present invention is the smallest in the known macroscopic electrolytic milling research. The 0.05 mm extremely small machining gap significantly reduces the interelectrode resistance. During machining, only less electrical energy is required to overcome the resistance, greatly reducing the electrical energy loss, improving the electrical energy utilization efficiency, obtaining a material removal rate nearly twice as high, and saving about 30% of the power cost. The significant reduction of the interelectrode resistance also evenly increases the overall current density in the extremely small machining gap. Cooperating with the efficient transportation and discharge of products, it significantly reduces the surface roughness value after machining and improves the machining surface quality. In addition, the extremely small machining gap helps to position the machining current, greatly reducing the peripheral low current density area caused by the edge effect, reducing stray corrosion and secondary corrosion of the machined surface, and improving the machining accuracy and machining localization.

[0019] The present invention has the following advantages:

[0020] 1. The operation of the present invention is simple and fast. Only by reversing the polarity and reverse copying the trimming tool electrode structure can the problems of too high local current density, too concentrated distribution, and difficult discharge of accumulated products in the extremely small machining gap be overcome simultaneously, and electrolytic milling with an extremely small machining gap can be efficiently realized.

[0021] 2 The process method of the present invention utilizes the properties of the electric field to accurately locate the high current density area, dissolve as required, with high accuracy and efficiency, and has a wide range of applications.

[0022] 3 The extremely small machining gap achieved by the present invention significantly reduces the inter-electrode resistance, greatly reduces the power loss, and improves the power utilization efficiency and material removal rate. The significant reduction of the inter-electrode resistance also evenly increases the overall current density within the extremely small machining gap. Coupled with the efficient transportation and discharge of the products, it significantly improves the surface quality of electrolytic milling. In addition, the extremely small machining gap helps to locate the machining current, reduces stray corrosion and secondary corrosion, and improves the machining accuracy and machining localization of electrolytic milling. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a three-dimensional schematic diagram of rectangular electrode electrolytic milling;

[0024] Figure 2 is a process flow diagram of using a reverse-copy electrode to achieve electrolytic milling with an extremely small machining gap;

[0025] Figure 3 is a comparison diagram between electrolytic milling with an extremely small machining gap and general electrolytic milling;

[0026] Among them, the reference numerals and names are: 1. rectangular electrode; 2. workpiece; 3. electrolyte; 4. electric field lines; 5. products; 6. bubbles; 7. sparks; 8. inner right angle; 9. outer right angle; 10. inner fillet; 11. outer fillet. EMBODIMENTS

[0027] The present invention will be further described in detail below with reference to the accompanying drawings:

[0028] The three-dimensional schematic diagram of general electrolytic milling is as shown in Figure 1 The rectangular electrode 1 is vertically placed, and the workpiece 2 is horizontally placed, with the two maintaining a mutually perpendicular layout. The electrolyte 3 flows in through the liquid inlet hole at the top of the rectangular electrode 1 via the main shaft, then flows out from the liquid outlet hole at the bottom of the rectangular electrode 1 to the surface of the workpiece 2, and finally discharges outward through the machining gap between the bottom surface of the rectangular electrode 1 and the surface of the workpiece 2. Figure 1 The shaded surface in Figure 2 and Figure 3 is perpendicular to both the surface of the workpiece 2 and the large-area wall surface of the rectangular electrode 1, and will be used as the

[0029] Figure 2 observation surface. Figure 2As shown in (a). The rectangular electrode 1 clamped on the machine tool spindle is connected to the positive pole of the DC power supply, and the workpiece 2 is connected to the negative pole of the DC power supply. The machining gap between the bottom surface of the rectangular electrode 1 and the surface of the workpiece 2 is generally 0.2 mm. Contrary to the polarity in general electrochemical milling, the rectangular electrode 1 becomes the anode in the electrolysis process, and the workpiece 2 becomes the cathode in the electrolysis process. The rectangular electrode 1 is machined by the workpiece 2. According to the tip effect of the electric field, the electric field is the strongest and the current density is the most concentrated in the area of a pair of outer right angles 9 on the outermost side of the bottom of the rectangular electrode 1 and a pair of inner right angles 8 on both sides of the liquid outlet hole. Figure 2 In (a), the electric field lines 4 are the densest; while for a pair of flat bottoms between the inner right angle 8 and the outer right angle 9, the electric field is weaker and the current density distribution is more dispersed. Figure 2 In (a), the electric field lines 4 are sparser. Step two is as Figure 2 As shown in (b), the DC power supply maintains a constant current. The rectangular electrode 1 and the workpiece 2 are energized, and the material at the bottom of the rectangular electrode 1 undergoes electrochemical anodic dissolution, and the electrolysis products 5 are continuously discharged. The electrolysis reaction is the most intense in the areas of the outer right angle 9 and the inner right angle 8 where the electric field is the strongest and the current density distribution is the most concentrated, and the most electrode material is dissolved. Keeping the DC power supply at a constant current all the time is to ensure precise positioning and preferential dissolution of the areas with concentrated current density near the inner right angle 8 and the outer right angle 9, relatively reducing the dissolution of the material near the flat bottom, and quickly and efficiently trimming the original sharp inner right angle 8 and outer right angle 9 into smoothly transitioning inner fillets 10 and outer fillets 11, rapidly dispersing the current density distribution and eliminating the high current density values. Therefore, for the rectangular electrode 1 with an outer dimension of 32 mm × 3 mm, a bottom liquid outlet hole size of 30 mm × 1 mm, and a material of 316L stainless steel, only 100 C of electric charge provided by the DC power supply is required in a 25% NaCl solution to eliminate the area with concentrated current density distribution, as Figure 2 As shown in (c), which is convenient and efficient. The electric field lines 4 in the areas near the smoothly transitioning inner fillets 10 and outer fillets 11 are dispersed, and the sparsity degree of the electric field lines 4 in the entire machining gap is similar. Comparing Figure 2 The inner fillet 10 in (c), it can be clearly found that the curvature of the inner fillet 10 is large. Because the inner right angle 8 is located on both sides of the liquid outlet hole, the flowing electrolyte 3 is clean and sufficient; the outer right angle 9 is located on the outermost side of the machining gap, and the flowing electrolyte 3 is relatively less and carries the products 5. The electrolysis reaction speed is relatively fast during the process of trimming the inner right angle 8 into the inner fillet 10, and more material is dissolved. After such trimming, the liquid outlet hole of the rectangular electrode 1 becomes a gradually changing flared opening, significantly reducing the hydrodynamic loss caused by the sudden change in the flow rate and direction of the electrolyte 3 at the original inner right angle 8, and greatly increasing the flow rate of the electrolyte 3 in the machining gap and the ability to carry and discharge the products 5. In view of the above method of reversing the polarity to reverse copy and trim the electrode, electrodes of different sizes and different conductive materials can change the power supply of the DC power supply to simultaneously eliminate the area with concentrated current density distribution and enhance the ability to efficiently discharge the products 5.

[0030] Step three is as follows Figure 2 as shown in (d). The trimmed rectangular electrode 1 is controlled by the main shaft to move downward, and the machining gap between it and the surface of the workpiece 2 is reduced to an extremely small machining gap of 0.05 mm, which is the smallest machining gap in the currently known research. The trimmed rectangular electrode 1 is connected to the negative pole of the DC power supply while the workpiece 2 is connected to the positive pole of the DC power supply. The workpiece 2 becomes the anode during the electrolysis process, and the rectangular electrode 1 becomes the cathode during the electrolysis process. The workpiece 2 is machined by the rectangular electrode 1. Step four starts the electrolytic milling with an extremely small machining gap, as shown in Figure 2 (e). The trimmed rectangular electrode 1 and the workpiece 2 are energized, and the main shaft controls the rectangular electrode 1 to feed along the preset trajectory at a speed of v . The material of the workpiece 2 undergoes electrochemical anodic dissolution accordingly. The flow rate of the electrolyte 3 within the extremely small machining gap below the trimmed rectangular electrode 1 is still very fast, which is sufficient to quickly discharge the electrolytic products 5 and bubbles 6 generated by the electrochemical reaction. At the same time, the concentrated area of the current density distribution within the machining gap is eliminated, avoiding damage to the electrolytic milling process such as sparks 7 and short circuits, and realizing the electrolytic milling with an extremely small machining gap.

[0031] Figure 3 The machining situations of the general rectangular electrode 1 and the trimmed rectangular electrode 1 during general electrolytic milling and electrolytic milling with an extremely small machining gap are compared. Figure 3 (a) shows the machining situation of the general rectangular electrode 1 during general electrolytic milling; Figure 3 (b) shows the machining situation of the general rectangular electrode 1 during electrolytic milling with an extremely small machining gap; Figure 3 (c) shows the machining situation of the trimmed rectangular electrode 1 during general electrolytic milling; Figure 3 (d) shows the machining situation of the trimmed rectangular electrode 1 during electrolytic milling with an extremely small machining gap. Comparing Figure 3 (a) and Figure 3 (c), it can be found that under the condition of unchanged other conditions during general electrolytic milling, the trimmed rectangular electrode 1 can obtain a faster flow rate of the electrolyte 3 within the machining gap. Figure 3 In (a), the inner right angle 8 of the general rectangular electrode 1 will cause the vertically downward flowing electrolyte 3 to suddenly change to a horizontal flow direction and then enter the machining gap. The flow channel also changes from an outlet hole with a width of more than 1 mm to a machining gap with a width of 0.2 mm. The electrolyte 3 is instantly compressed, the flow rate drops steeply, and the hydrodynamic loss is serious. When changing to Figure 3 the inner fillet 10 of the trimmed rectangular electrode 1 in (c), the vertically downward flowing electrolyte 3 can first flow obliquely and then gradually change to a horizontal flow direction, and the flow channel also gradually decreases, significantly reducing the hydrodynamic loss and increasing the flow rate of the electrolyte 3 within the machining gap. In this way, more electrolytic products 5 can be carried out of the machining gap, Figure 3(c) There are significantly fewer particles of product 5 in the middle gap. In addition, reduction reaction occurs on the bottom surface of the rectangular electrode 1 acting as the cathode to generate bubbles 6. Since the sudden change in the velocity and direction of the electrolyte 3 at the inner right angle 8 of the general rectangular electrode 1 leads to an extremely low flow rate near the bottom surface of the rectangular electrode 1, the bubbles 6 generated at the inner right angle 8 are difficult to be quickly transported to the outer right angle 9 and discharged, and will accumulate to form a bubble 6 layer, as Figure 3 shown in (a), weakening the current density and increasing the power loss. However, the flow rate near the bottom surface of the trimmed rectangular electrode 1 is still very high. Coupled with the upward arc of the electrode bottom surface formed by the outer fillet 11, which conforms to the escape direction of the bubbles 6, the bubbles 6 can be quickly discharged.

[0032] When the machining gap is reduced to the minimum value, the flow rate of the electrolyte 3 in the machining gap under the general rectangular electrode 1 is even lower, and more product 5 particles and bubbles 6 cannot be discharged, as Figure 3 shown in (b), which greatly reduces the conductivity of the electrolyte 3 in the machining gap and increases the risk of sparks 7 and discharges. Coupled with the uneven distribution of the current density under the general rectangular electrode 1, the current density at the inner right angle 8 and the outer right angle 9 is the largest and the most concentrated, and it is very easy to cause intense sparks 7, as Figure 3 shown in (b), uncontrollably causing disordered damage to the cathode and anode. This is also the reason why it has been impossible to achieve electrolytic milling with an extremely small machining gap. However, the trimmed rectangular electrode 1 can eliminate the region with concentrated current density distribution; and as Figure 3 shown in (d), the flow rate of the electrolyte 3 in the extremely small machining gap under it is still very fast, which is sufficient to carry the electrolytic products 5 and bubbles 6 generated by the electrochemical reaction and discharge them quickly, completely avoiding the risk of sparks 7.

[0033] When the trimmed rectangular electrode 1 is used for electrolytic milling with an extremely small machining gap, the interelectrode resistance is significantly reduced. During machining, only less electrical energy is required to overcome the resistance, greatly reducing the power loss, improving the power utilization efficiency, obtaining a material removal rate nearly twice as high, and saving about 30% of the power cost. The significant reduction in the interelectrode resistance also evenly increases the overall current density in the extremely small machining gap. Combined with the efficient transportation and discharge of the product 5, it significantly reduces the surface roughness value after machining and improves the machining surface quality. In addition, the extremely small machining gap helps to position the machining current, greatly reducing the peripheral low current density area caused by the edge effect, reducing the stray corrosion and the secondary corrosion of the machined surface, and improving the machining accuracy and machining localization.

[0034] The present invention can eliminate the concentrated area of current density distribution and enhance the ability of efficient discharge of the product 5 by reverse-copying and trimming the rectangular electrode 1, simply and efficiently realizing electrolytic milling with an extremely small machining gap, improving the machining efficiency, machining surface quality and machining accuracy of electrolytic milling. However, the above description should not be construed as a limitation on the patent of the present invention. It should be noted that several improvements can be made without departing from the concept of the present invention, and all of these should fall within the protection scope of the patent of the present invention.

Claims

1. A process method for electrolytic milling with an extremely small machining gap by using a reverse-copy electrode, characterized in that It includes the following processes: Step 1, anti-copy preparation: The rectangular electrode (1) vertically clamped on the machine tool spindle is connected to the positive pole of the DC power supply, and the horizontally placed workpiece (2) is connected to the negative pole of the DC power supply. The machining gap between the bottom surface of the rectangular electrode (1) and the surface of the workpiece (2) is controlled by the spindle to be H. The electrolyte (3) flows into the rectangular electrode (1) from the liquid inlet hole at the top of the rectangular electrode (1) through the spindle, then flows out from the liquid outlet hole at the bottom of the rectangular electrode (1) to the surface of the workpiece (2), and finally discharges outwards through the machining gap between the bottom surface of the rectangular electrode (1) and the surface of the workpiece (2); Step 2, anti-copy machining of the rectangular electrode (1): The DC power supply maintains a constant current. The rectangular electrode (1) and the workpiece (2) are energized. The material at the bottom of the rectangular electrode (1) undergoes electrochemical anodic dissolution. Since the current density is the highest and the distribution is the most concentrated, the pair of symmetric outer right angles (9) on the outermost side at the bottom of the rectangular electrode (1), and the pair of symmetric inner right angles (8) on both sides of the liquid outlet hole at the bottom of the rectangular electrode (1) are the main dissolution areas of the electrode material, and are respectively dissolved into a pair of outer rounded corners (11) and a pair of inner rounded corners (10) until the width of the bottom surface of the rectangular electrode (1) between the outer rounded corners (11) and the inner rounded corners (10) is reduced to 50% - 75% of the original, the current density distribution becomes dispersed and the concentrated area is completely eliminated, and the DC power supply is powered off; Step 3, process condition adjustment: The spindle is used to control the trimmed rectangular electrode (1) to move downward, and the machining gap between the trimmed rectangular electrode (1) and the surface of the workpiece (2) is reduced to a very small machining gap h. The trimmed rectangular electrode (1) is connected to the negative pole of the DC power supply while the workpiece (2) is connected to the positive pole of the DC power supply, and the electrolyte (3) keeps flowing; Step 4, electrolytic milling with a very small machining gap: The trimmed rectangular electrode (1) and the workpiece (2) are energized. The spindle controls the rectangular electrode (1) to feed according to a preset trajectory, and the material of the workpiece (2) undergoes electrochemical anodic dissolution accordingly. The flow rate of the electrolyte (3) in the very small machining gap below the trimmed rectangular electrode (1) is still very fast, which is sufficient to quickly discharge the electrolytic products (5) and bubbles (6) generated by the electrochemical reaction. At the same time, the concentrated area of the current density distribution in the machining gap is eliminated, thus avoiding the damage to the electrolytic milling process such as sparks (7) and short circuits, and realizing the electrolytic milling with a very small machining gap.

2. The process method for electrolytic milling with an extremely small machining gap by using a reverse-copy electrode according to claim 1, characterized in that: The material of the above-mentioned rectangular electrode (1) is an acid and alkali corrosion-resistant conductor; the electrolyte (3) is a salt solution of water-based and organic solvents with a concentration of 1% - 50%. The electric quantity provided by the DC power supply for trimming the rectangular electrode (1) in the above-mentioned step 2 is 10 - 5000 C.

3. The process method for electrolytic milling with an extremely small machining gap by using a reverse-copy electrode according to claim 1, characterized in that: The curvature of the outer rounded corner (11) of the trimmed rectangular electrode (1) in the above-mentioned step 2 is larger than that of the inner rounded corner (10).

4. The process method for electrolytic milling with an extremely small machining gap by using a reverse-copy electrode according to claim 1, characterized in that: The above-mentioned machining gap H is 0.2 - 0.5 mm.

5. The process method for electrolytic milling with an extremely small machining gap by using a reverse-copy electrode according to claim 1, characterized in that: The above-mentioned very small machining gap h is 0.05 - 0.1 mm.

Images