Manufacturing method of enameled wire for painting stranded bare metal conductor

Abstract

The invention relates to the technical field of enameled wires, and provides a manufacturing method of an enameled wire for painting after stranding of bare metal conductors in order to solve the technical problems that paint is difficult to fill uniformly and the surface performance is unstable due to the fact that lines and gaps exist on the surface of a stranded conductor. Comprising the following steps: S1, carrying out annealing softening treatment on a single-core metal conductor; s2, twisting the plurality of annealed conductors; s3, annealing the stranded conductor again; s4, the stranded conductor sequentially passes through a front furnace and a rear furnace to be painted, low-viscosity insulating paint is used in the front furnace, a felt method is used for coating, gaps are filled through pressurization, a furnace body is prolonged, and repeated coating and baking are carried out in a circulating mode; a rear furnace is coated with a high-viscosity insulating paint eye mold, the roundness is adjusted through a slightly large eye mold in the first four times, coating and baking are conducted multiple times through a conventional eye mold in the subsequent process, and a rear furnace body is shorter than the front furnace to prevent over-baking; s5, coating lubricating oil or wax; and S6, rolling a finished product. The stranded enameled wire is compact in structure, smooth in surface and excellent in flexibility and bending resistance.

Description

Technical Field

[0001] The invention relates to the technical field of enameled wires, and in particular to a method for manufacturing enameled wires which are coated with paint after twisting bare metal conductors. Background Art

[0002] Enameled wire is an insulated conductor commonly used in electromagnetic coils, motors, transformers, and other fields. Conventional enameled wire generally uses a single-core metal conductor, with multiple layers of insulating varnish evenly coated on the surface and cured at high temperature. It has good insulation properties and mechanical strength. However, in some application scenarios, such as electronic products used for repeated bending, moving parts, or flexible connections, higher requirements are placed on the flexibility and bending resistance of the enameled wire. At the same time, there are strict control standards for its electrical properties, especially its resistance value. Existing conventional single-core enameled wire with pure copper or alloy conductors is difficult to meet the reliability requirements of such products in dynamic applications due to its strong rigidity and limited fatigue resistance.

[0003] To improve flexibility, one approach is to twist multiple thin-diameter bare metal wires together and then insulate and coat the entire conductor. This twisted structure significantly improves the bending flexibility of the wire. However, if ordinary single-core enameled wire is used first and then twisted, the insulating varnish layer on the surface of each core wire isolates each other, leading to electrical isolation within the conductor. This can cause problems such as high overall resistance and unstable conductivity. Furthermore, if insulation defects exist in the individual wires before twisting, the risk of electrical performance fluctuations can be further exacerbated.

[0004] Another solution is to twist bare metal conductors and then directly extrude and coat them with multiple insulation layers to form a composite structure, such as three-layer insulated wire. However, the insulation thickness of this type of wire is relatively large, usually needing to be increased by about 0.150mm or more. Taking the 0.18mm specification as an example, the outer diameter of the finished product is 0.33-0.38mm, resulting in a significant increase in the overall wire diameter, which is not conducive to small-size winding design. At the same time, its surface roughness is high and the smoothness is poor, which also limits the direct solderability and winding performance during processing.

[0005] Therefore, stranding bare metal conductors before applying the traditional enameled wire coating and curing process offers an ideal balance of flexibility, flex resistance, and electrical performance. For example, a single-core copper enameled wire with a diameter of 0.18mm has a resistance of approximately 0.672Ω / m. A conductor made by twisting seven bare copper wires with a diameter of 0.068mm has a resistance comparable to that of a single-core copper wire with a diameter of only approximately 0.027mm. If a standard thickness of insulating enameled wire is successfully applied, the finished wire diameter approaches that of the original single-core enameled wire, effectively improving performance while avoiding an excessively large outer diameter.

[0006] However, traditional enameled wire production requires extremely high surface smoothness. Spiral lines and gaps are common on the stranded conductor surface. After applying liquid lacquer and then undergoing high-temperature curing, defects such as paint particles, paint bumps, uneven filling, and pinholes are prone to appearing. This lack of smoothness affects the product's appearance and withstand voltage performance. Furthermore, achieving uniform lacquer filling in these gaps and forming a dense, smooth, and even insulation layer around the conductor remains a major technical challenge.

[0007] Therefore, there is an urgent need for a manufacturing process for stranded conductor enameled wire that can take into account insulation effect, finished product smoothness and electrical performance consistency to meet the urgent demand for high-flexibility and high-reliability enameled wire in special applications. Summary of the Invention

[0008] In order to solve the technical problem that the presence of lines and gaps on the surface of twisted conductors makes it difficult to evenly fill the paint and the surface performance is unstable, the present invention provides a method for manufacturing enameled wires that are painted after twisting bare metal conductors.

[0009] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0010] The present invention provides a method for manufacturing an enameled wire for twisting bare metal conductors and then coating them with paint, comprising the following steps:

[0011] S1. performing annealing and softening treatment on the single-core metal conductor;

[0012] S2, twisting the plurality of annealed and softened single-core metal conductors;

[0013] S3, annealing the twisted conductor again;

[0014] S4. The stranded conductors are sequentially passed through the front furnace and the back furnace for enameling treatment, wherein:

[0015] a) The forehearth uses insulating varnish with low viscosity and high fluidity after dilution, and is applied using the felt method. A pressure block is added to the felt to increase the pressure, so that a small amount of low-viscosity varnish fills the conductor twist gaps, and there is almost no adhesion on the outer periphery;

[0016] b) The length of the forehearth is extended to meet the baking time required for the curing of low-viscosity paint, and multiple rounds of paint baking treatment are carried out;

[0017] c) The back furnace uses high-concentration and high-viscosity insulating varnish of the same type to coat the eye mold. When the back furnace is coating for the first four times, the inner diameter of the eye mold used is 1.04 to 1.06 times the outer diameter of the stranded conductor, which is used to fill the gap and round the outer diameter of the stranded conductor to make the conductor round.

[0018] d) Starting from the fifth coating, the inner diameter of the coating eye mold shall be 1.09 times or more of the outer diameter of the stranded conductor for further rounding and thickening;

[0019] e) The length of the rear furnace body is smaller than that of the front furnace to prevent the insulation layer from being damaged by excessive baking;

[0020] S5. Apply lubricating oil or wax to the surface of the enameled wire coming out of the back furnace;

[0021] S6. Rewind the finished product line.

[0022] The single-core metal conductors are first annealed before twisting, and then annealed again to stabilize the twisted structure, ensuring the softness and consistency of the conductors. The front furnace uses low-viscosity, highly fluid insulating varnish combined with felt pressure coating to effectively penetrate the twisted gaps, leaving no excess adhesion on the outer periphery. The furnace body is extended and multiple rounds of coating and baking are used to fill the gaps and initially smooth the surface. The rear furnace uses high-viscosity varnish and eye mold coating. The front section rounds the conductor shape and the rear section constructs a uniform and dense insulation layer. The furnace length is shortened to avoid over-baking of the insulation. Finally, the lubricity of the finished product is improved by applying wax or lubricating oil. The overall process can achieve high-performance twisted enameled wire with a dense structure, smooth surface, stable resistance, excellent flexibility and bending resistance. It is particularly suitable for applications with high requirements for insulation quality, electrical consistency and mechanical properties.

[0023] Furthermore, the inner diameters of the paint molds used in the first four coats are, respectively, 1.04, 1.04, 1.05, and 1.06 times the outer diameter of the stranded conductor. Starting with the fifth coat, the inner diameter of the paint mold is set starting at 1.09 times the outer diameter of the stranded conductor and increasing in an arithmetically spaced manner. Using a paint mold with a smaller multiple difference from the outer diameter of the stranded conductor in the first four coats helps gradually shape and round the conductor profile during the initial coating phase, making the conductor's shape more consistent and providing a stable benchmark for subsequent coats. Starting with the fifth coat, using an inner diameter setting starting at 1.09 times the outer diameter and increasing in an arithmetically spaced manner allows for uniform layer-by-layer thickening of the insulation coating, effectively controlling the morphology and thickness distribution of the paint layer. This prevents surface defects caused by excessive coating buildup, improves the insulation density and smoothness of the final product, and ensures the mechanical flexibility, electrical stability, and surface quality of the enameled wire.

[0024] Furthermore, the solvent ratio of the low-viscosity insulating varnish used in the forehearth is significantly lower than that used in conventional enameling processes, resulting in a significantly lower solids content. Specifically, the low-viscosity, low-solids insulating varnish used in the forehearth has a solids content of less than 5%, compared to more than 15% for conventional varnish. This significantly improves the varnish's fluidity and permeability, allowing it to more easily fill tiny gaps on the surface of the stranded conductor, effectively preventing bubbles, voids, or insulation defects caused by insufficient filling, thereby improving the integrity and density of the insulation layer. Furthermore, since the low-solids varnish has virtually no excess adhesion to the surface of the gaps, unnecessary coating accumulation is avoided, helping to achieve a preliminary smoothing of the stranded conductor surface.

[0025] Furthermore, the felt coating method employs a felt press block to ensure closer contact between the conductor and the felt as it passes through, enhancing the paint's permeability. Applying the press block to the felt increases the contact pressure between the conductor and the felt, allowing the low-viscosity paint to more fully penetrate the gaps between the stranded conductors. This improves paint adhesion and filling, reduces voids, and enhances the mechanical reliability and electrical insulation performance of the finished product.

[0026] Furthermore, the front furnace is painted 8 to 10 times, while the rear furnace is painted 5 times, preferably 4 to 6 times. Multiple cycles of coating and baking build a dense and uniform insulation layer by layer. The front furnace achieves gap filling and preliminary shaping, while the rear furnace forms a surface coating and improves smoothness and insulation strength, giving the enameled wire both good mechanical flexibility and stable insulation performance.

[0027] Furthermore, the high-viscosity and high-solid content insulating varnish used in the rear furnace has a solid content of more than 38%; the low-viscosity and low-solid content insulating varnish used in the front furnace has a solid content of less than 5%.

[0028] By using low-viscosity insulating varnish with a solid content of less than 5% in the front furnace, it can fully penetrate and fill the tiny gaps on the surface of the twisted conductor, achieving uniform coverage of the insulation layer inside the gaps. By using high-viscosity insulating varnish with a solid content of more than 38% in the rear furnace, an outer insulating layer with uniform thickness, dense structure and strong adhesion can be quickly formed on the conductor surface. The combination of the two not only takes into account the permeability of the internal filling and the integrity of the outer coating, but also effectively controls the total thickness and flatness of the insulating layer, thereby significantly improving the electrical consistency, surface finish and mechanical strength of the enameled wire, and meeting the strict requirements of high-performance flexible applications for insulation reliability and finished product consistency.

[0029] Furthermore, the line speed in the front and rear furnaces is the same, and the baking temperature range is 370°C to 390°C, preferably 390°C. Maintaining consistent line speeds in the front and rear furnaces ensures a continuous and stable enameling process, preventing wire deformation or insulation damage caused by abnormal tension. The temperature control range helps the same varnish achieve optimal curing effects at different stages, improving process stability and finished product consistency.

[0030] The beneficial effects brought about by implementing the present invention are as follows:

[0031] The method for manufacturing enameled wire for painting bare metal conductors after twisting, provided by the present invention, can effectively solve technical problems such as difficulty in uniformly filling the paint, unstable surface properties, and poor consistency of the finished product caused by spiral lines and gaps on the surface of the twisted conductor. The conductor flexibility and structural stability are improved by annealing the conductors before and after twisting. An insulating varnish with extremely low viscosity and a high solvent ratio is used in combination with a felt pressing block for the front coating, so that the paint can smoothly penetrate and fill the gaps without forming accumulation on the outer surface. The extended furnace body and multiple cycles of coating and baking are combined to achieve full curing and a smooth transition. Subsequently, the conductor is coated layer by layer with an insulating varnish with a higher viscosity using an eye mold to round the conductor. The slightly larger eye mold in the front section can make the wire more round, and the conventional eye mold in the back section further improves the surface smoothness and insulation strength. The overall process not only ensures structural density and gap filling integrity, but also achieves a finished product with a rounded appearance, stable insulation, and good lubricity. It is particularly suitable for important fields requiring high flexibility, high bending resistance, resistance consistency, and insulation reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a front view structural diagram of the enameled wire painting equipment of the present invention;

[0033] Figure 2 It is a schematic diagram of the three-dimensional structure of the enameled wire painting equipment of the present invention;

[0034] Figure 3 This is a schematic diagram of the assembly of the base, the pay-off mechanism, the guide wheel 1 and the annealing furnace in the present invention;

[0035] Figure 4 This is a schematic diagram of the assembly of the base, lubricating oil mechanism and winding mechanism in the present invention;

[0036] Figure 5 This is a schematic diagram of the assembly of the base, felt mechanism and forehearth in the present invention;

[0037] Figure 6 This is a flow chart of the enameled wire manufacturing method of the present invention.

[0038] In the figure: 1. Base; 2. Pay-off mechanism; 21. Mounting block 1; 22. Concave block 1; 23. Threaded rod 1; 24. Moving block 1; 25. Mounting plate 1; 26. Sleeve 1; 27. Pay-off wheel; 3. Guide wheel 1; 4. Annealing furnace; 5. Guide wheel 2; 6. First guide wheel; 7. Felt mechanism; 71. Insulating paint box; 72. Fixed plate 1; 73. Paint felt; 74. Material pump; 75. Discharge pipe; 8. Front furnace; 9. Eye mold; 10. Rear furnace; 11. Second guide wheel; 12. Lubricating oil mechanism; 121. Lubricating oil tank; 122. Water pump; 123. Fixed plate 2; 124. Pulley; 125. Oil spray pipe; 13. Winding mechanism; 131. Concave block 2; 132. Threaded rod 2; 133. Moving block 2; 134. Mounting plate 2; 135. Sleeve 2; 136. Winding wheel. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] See Figure 1 and Figure 2 The present invention provides an enameled wire coating device for bare metal conductors after stranding, which is provided with a wire-releasing mechanism 2, a guide wheel 1 3, an annealing furnace 4, a guide wheel 2 5, a first guide wheel 6, a felt mechanism 7, a front furnace 8, an eye mold 9, a rear furnace 10, a second guide wheel 11, a lubricating oil mechanism 12 and a winding mechanism 13 in sequence from one side to the other.

[0041] The pay-off mechanism 2 is wound with a stranded wire made of annealed and softened bare metal wire.

[0042] See Figure 2 The pay-off mechanism 2 includes a mounting block 21, a concave block 22, a threaded rod 23, two moving blocks 24, two mounting plates 25, two sleeves 26 and a pay-off wheel 27. The mounting block 21 is mounted on the top of the base 1, the concave block 22 is mounted on the mounting block 21, the threaded rod 23 is rotatably mounted in the concave block 22, and the two moving blocks 24 are symmetrically slidably mounted in the concave block 22. The two moving blocks 24 are both threadedly connected to the threaded rod 23.

[0043] The two mounting plates 25 are respectively mounted on the two moving blocks 24 , and the two sleeves 26 are respectively rotatably mounted on the outer walls of the two mounting plates 25 close to each other. The unwinding wheel 27 is arranged between the two sleeves 26 , and the two sleeves 26 are respectively adapted to the two ends of the unwinding wheel 27 .

[0044] One end of the threaded rod 1 23 extends to the outside of one side of the concave block 1 22 and is installed with a turntable 1. The guide wheel 1 3, the annealing furnace 4 and the guide wheel 2 5 are all installed on the top of the base 1.

[0045] The forehearth 8 is installed on the top of the base 1 , the two first guide wheels 6 are symmetrically installed on the forehearth 8 , and the felt mechanism 7 is arranged on the forehearth 8 , and the felt mechanism 7 is located between the corresponding first guide wheel 6 and the forehearth 8 .

[0046] See Figure 5 The felt mechanism 7 includes an insulating paint box 71, a fixed plate 72, two paint felts 73, a material pump 74 and two discharge pipes 75. The insulating paint box 71 and the fixed plate 72 are both installed on the front furnace 8. The fixed plate 72 is located in front of the insulating paint box 71. The two paint felts 73 are installed on the fixed plate 72 in an up-and-down symmetrical manner. A vertical pipe is installed on the rear outer wall of the fixed plate 72. The material pump 74 is installed on the insulating paint box 71. The extraction pipe on the material pump 74 extends into the insulating paint box 71. The injection pipe on the material pump 74 is connected to the vertical pipe. The two discharge pipes 75 are installed on the fixed plate 72 in an up-and-down symmetrical manner. One end of the two discharge pipes 75 is aligned with the two paint felts 73 respectively, and the other end of the two discharge pipes 75 is connected to the vertical pipe.

[0047] The back furnace 10 is installed on the base 1 , two second guide wheels 11 are symmetrically installed on the back furnace 10 , the eye mold mold 9 is installed on the back furnace 10 , and the eye mold mold 9 is located between the corresponding second guide wheel 11 and the back furnace 10 .

[0048] See Figure 4 The lubricating oil mechanism 12 is arranged on the base 1. The lubricating oil mechanism 12 includes a lubricating oil tank 121, a water pump 122, a second fixed plate 123, a pulley 124 and an oil spray pipe 125. The lubricating oil tank 121 is installed on the base 1, the water pump 122 is installed on the top of the lubricating oil tank 121, the second fixed plate 123 is installed on the front outer wall of the lubricating oil tank 121, and the two pulleys 124 are symmetrically installed on the second fixed plate 123 in an upper and lower manner. The oil suction pipe on the water pump 122 extends into the lubricating oil tank 121, and the oil discharge pipe of the water pump 122 extends to the outside of one side of the second fixed plate 123 and is located above the pulley 124.

[0049] The winding mechanism 13 is arranged on the base 1. The winding mechanism 13 includes a mounting block 2, a concave block 2 131, a threaded rod 2 132, two moving blocks 2 133, two mounting plates 2 134, two sleeves 2 135, and a winding wheel 136. The mounting block 2 is mounted on the top of the base 1, the concave block 2 131 is mounted on the mounting block 2, the threaded rod 2 132 is rotatably mounted on the concave block 2 131, and the two moving blocks 2 133 are symmetrically slidably mounted on the concave block 2 131. The two moving blocks 2 133 are both threaded with the threaded rod 2 132. The two mounting plates 134 are respectively mounted on the two moving blocks 133, and the two sleeves 135 are respectively rotatably mounted on the outer walls of the two mounting plates 134 on one side close to each other. The winding wheel 136 is arranged between the two sleeves 135, and the two ends of the winding wheel 136 are respectively adapted to the two sleeves 135. A motor is installed on the corresponding mounting plate 134, and the output shaft of the motor is fixedly connected to one end of the corresponding sleeve 135. One end of the threaded rod 132 extends to the outside of one side of the concave block 131 and is installed with a turntable 2.

[0050] See Figure 6 Based on the above-mentioned equipment, the present invention provides a method for manufacturing enameled wire for painting after twisting bare metal conductors, which is suitable for improving the flexibility, surface quality and insulation performance of the enameled wire, and especially proposes an improved process for the problem of difficulty in filling gaps with paint in the twisted structure of multiple metal conductors.

[0051] First, several single-core metal conductor wires are annealed to improve their ductility and strand consistency. The annealed single-core metal wires are then twisted together under controlled tension and pitch to form a tightly structured stranded conductor. This stranded conductor is then annealed again to eliminate stresses induced during the twisting process and ensure structural stability during subsequent processing.

[0052] Next, the stranded conductors enter the enameling process in two stages, the front furnace 8 and the back furnace 10. The front furnace 8 section is painted using the felt method. The insulating varnish used is a highly diluted varnish of the same type. Its viscosity and concentration are far lower than those required for conventional coating. It has excellent fluidity and can penetrate and fill the tiny gaps between the conductors in small amounts under the pressure of the felt. To improve the paint penetration effect, a pressure block is added to the felt to ensure that the felt is fully fitted to the conductor surface, ensuring that the low-viscosity paint effectively enters the spiral groove gaps between each conductor. This step adopts a repeated coating and baking method. Usually after 8 to 10 treatments, the gaps in the conductors are gradually filled, the surface tends to be smooth, and the waste caused by uneven peripheral coating is effectively avoided.

[0053] Because the low-viscosity, high-solvent insulating varnish used in forehearth 8 is difficult to completely dry and cure at standard process temperatures (around 380°C), the present invention significantly extends the length of the forehearth 8 to prolong the heating time and improve curing efficiency. Considering that low-viscosity varnish has difficulty forming a good coating on the conductor surface, and further increasing the number of forehearth 8 cycles no longer significantly improves performance, the conductor enters the backhearth 10 stage.

[0054] In the rear furnace section 10, the same high-viscosity, high-concentration insulating varnish as in the front furnace section 8 is used undiluted, and an eye-molding coating process is employed. The eye-molding process is initially configured with four dies slightly larger than the outer diameter of the stranded conductor and of uniform size. The inner diameters of the eye-molding dies used in the first four coats are, respectively, 1.04, 1.04, 1.05, and 1.06 times the outer diameter of the stranded conductor. This process gradually rounds the conductor with only a slight increase in outer diameter and film thickness. After the fourth coat, subsequent eye-molding dimensions are configured according to conventional enameled wire process requirements. Approximately five more coats and bakes are performed to achieve the target thickness and uniformity of the enameled layer. Starting with the fifth coat, the inner diameter of the eye-molding dies is set at 1.09 times the outer diameter of the stranded conductor and increases in an arithmetic progression, starting at 1.12 times the outer diameter of the stranded conductor for the sixth and seventh coats, respectively, and continuing in a similar fashion.

[0055] Because the rear furnace 10 uses a high-viscosity varnish that cures quickly, its length can be significantly shorter than the front furnace 8, thus preventing thermal degradation or cracking of the insulating varnish due to overheating. The conductor's operating speed remains consistent between the front and rear furnaces 10 throughout the coating process, aligning with the curing temperature range of the same type of varnish, ensuring product consistency and process controllability.

[0056] After coating, the conductor surface is further treated with lubricant or wax to improve its sliding properties and processing compatibility, and to prevent wear or scratches on the paint film during subsequent winding and use. Finally, the finished enameled wire is wound and packaged by a winding device.

[0057] The twisted conductor enameled wire produced by the above manufacturing method has the characteristics of small outer diameter, good softness, high bending resistance and smooth surface; especially when the conductor is made of a highly flexible material such as copper alloy or aluminum alloy, this method can further improve its comprehensive mechanical properties on the basis of its inherent toughness, and is particularly suitable for application scenarios such as high-frequency winding coils, flexible wires, and micro motor coils that have high requirements on dimensional accuracy and winding ability.

[0058] The beneficial effects of implementing the method for manufacturing an enameled wire for twisting bare metal conductors and then painting them provided by the present invention are as follows:

[0059] This method achieves full filling of the gaps in the twisted conductors and uniform coating of the outer circumference by coating the twisted conductors with low-viscosity and high-viscosity insulating varnishes in stages in sequence, and combines the process of the front furnace felt method with the rear furnace eye mold method. This method not only effectively solves the problems of difficult gap filling and uneven outer layer in multi-strand conductor structures, but also improves the roundness and insulation performance of the enameled wire. The front furnace extends the furnace body and uses diluted varnish in combination with multiple rounds of curing to gradually fill the gaps with low-viscosity varnish, while the rear furnace forms a dense outer coating with high-viscosity varnish, effectively controlling the coating thickness and quality. The resulting enameled wire has the advantages of small outer diameter, good softness, high bending resistance, and smooth surface. It is particularly suitable for occasions with high requirements on wire formability and winding performance. The paint film has good density and adhesion, which is beneficial to improving the long-term electrical stability and mechanical reliability of the product.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing an enameled wire for twisting bare metal conductors and then coating them with paint, characterized in that: The steps include: S1. performing annealing and softening treatment on the single-core metal conductor; S2, twisting the plurality of annealed and softened single-core metal conductors; S3, annealing the twisted conductor again; S4. The stranded conductors are sequentially passed through the front furnace and the back furnace for enameling treatment, wherein: a) The forehearth is coated with insulating varnish of the first concentration and viscosity by a felt method, and a pressure block is added to the felt to increase the pressure; b) Extend the length of the forehearth to meet the baking time required for the curing of low-viscosity paints and perform multiple paint baking treatments; c) the back furnace uses the same type of insulating varnish with a second concentration value and a second viscosity value to coat the eye mold, wherein the second concentration value is greater than the first concentration value, and the second viscosity value is greater than the first viscosity value. When the back furnace performs the first four coatings, the inner diameter of the painted eye mold used is 1.04 to 1.06 times the outer diameter of the stranded conductor; d) Starting from the fifth coating, the inner diameter of the coating eye mold shall be 1.09 times or more of the outer diameter of the stranded conductor; e) The length of the rear furnace is smaller than that of the front furnace; S5. Apply lubricating oil or wax to the surface of the enameled wire coming out of the back furnace; S6. Rewind the finished product line.

2. The method for manufacturing an enameled wire for twisting bare metal conductors and then painting them according to claim 1, characterized in that: The inner diameters of the painted eye molds used in the first four times are 1.04 times, 1.04 times, 1.05 times, and 1.06 times the outer diameter of the stranded conductor, respectively; starting from the fifth painting, the inner diameter of the painted eye mold starts at 1.09 times the outer diameter of the stranded conductor and is set in an arithmetically increasing manner.

3. The method for manufacturing an enameled wire for twisting bare metal conductors and then painting them according to claim 1, characterized in that: The low-viscosity and low-solid-content insulating varnish used in the forehearth has a solid content of less than 5%.

4. The method for manufacturing an enameled wire for twisting bare metal conductors and then painting them according to claim 1, characterized in that: The front furnace is painted 8 to 10 times, and the rear furnace is painted 7 to 9 times.

5. The method for manufacturing an enameled wire for twisting bare metal conductors and then painting them according to claim 1, characterized in that: The high-viscosity and high-solid content insulating varnish used in the rear furnace has a solid content of more than 38%; the low-viscosity and low-solid content insulating varnish used in the front furnace has a solid content of less than 5%.

6. The method for manufacturing an enameled wire for twisting bare metal conductors and then painting them according to claim 1, characterized in that: The line speed in the front furnace and the rear furnace is the same, and the baking temperature range is 370℃~390℃.

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