Production method of coaxial unit high-speed parallel transmission symmetric cable

Abstract

The invention relates to the technical field of cable production, in particular to a production method of a coaxial unit high-speed parallel transmission symmetrical cable, which comprises the following steps: S1, polishing a conductor; s2, insulation pushing or wrapping forming, wherein a PTFE pushing cable insulation process or a PTFE microporous belt wrapping cable insulation forming process is adopted; s3, shielding and wrapping, wherein an electronic-grade high-frequency ultra-low profile copper foil (HVLP) is adopted for wrapping; s4, shielding and shaping; s5, wrapping an inner buffer layer; s6, filling and cabling, wherein a 100% back-twist cage stranding machine is adopted for cabling; s7, outer buffer layer wrapping: wrapping is performed in the same manner as the inner buffer layer, and filling and cabling processes are completed synchronously; s8, weaving is conducted; s9, forming the sheath; according to the whole method, the damage of the coaxial subunits in the cabling process can be reduced, the positions of the coaxial subunits are relatively fixed, and the delay difference between the coaxial subunits is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cable production, and particularly relates to a production method for a coaxial unit high-speed parallel transmission symmetrical cable. Background Art

[0002] The basic transmission unit structure of a high-speed parallel transmission symmetrical cable can be referred to Figure 1 . From its cross-section, it includes a metal conductor 1, an insulating layer 2, and a metal shielding layer 3. The structure is characterized by two insulated single wires arranged in parallel, with a metal shielding layer wrapped outside, which conforms to the definition of parallel wire pairs in high-speed parallel cables for digital communication in relevant standards. In the current market, for a high-speed cable with the above structure and a length of 5 meters, the highest mature data transmission bandwidth per unit can reach 112 Gbps; when the length is shorter, 2 meters or 1 meter, the highest mature data transmission bandwidth per unit can reach 224 Gbps.

[0003] However, for the requirements of the next-generation higher transmission bandwidth, such as a transmission bandwidth of up to 336 Gbps or 448 Gbps per unit, this structure can no longer meet the requirements. The reason is that the two insulators are in the same shielding layer, and in addition, the external shielding uses a "wrapping" process method, tightly wrapping the two insulators together, resulting in the deformation of the cross-sectional shape of the insulation, changing from an ideal circular shape to an elliptical shape, and finally leading to uneven electromagnetic field distribution between the two conductors, a decline in the quality of the transmitted signal, and an inability to increase the transmission bandwidth. In addition, since the two conductors of the parallel wire pair share a shielding layer as the conductor for the return body current, in the case of high frequencies, due to the skin effect principle, as Figure 2 shown, the effective current-carrying area 4 (the area covered by the lines) of the internal conductor shrinks sharply, shrinking to within 75% of the circumferential area of the outer surface of the inner conductor, and the entire circumferential area of the outer surface of the inner conductor cannot be used, resulting in the effective cross-sectional area of the inner conductor of the parallel pair structure not reaching 100%, and further causing a relatively large signal loss attenuation and relatively serious signal quality deterioration of this structure, making it difficult to increase the transmission bandwidth.

[0004] In view of the above problems, the invention patent with the authorization announcement number CN221861297U discloses a high-speed Ethernet automotive high-speed data transmission cable, which includes two parallel signal conductors. Each signal conductor is successively provided with an insulating material, a shielding layer, and a buffer layer on the outside. The two signal conductors are no longer in the same shielding layer, reducing signal attenuation and improving signal quality and transmission bandwidth. However, there are still certain problems in the production of this coaxial unit parallel transmission symmetrical cable: 1) The two transmission sub-units are of coaxial structure, and the coaxial sub-units are prone to axial torque during the cabling process, resulting in damage; 2) There are gaps between the coaxial sub-units, which are prone to relative displacement and cause frictional collision damage, resulting in an uneven outer peripheral circular contour after cabling; 3) The physical lengths of the coaxial sub-units are not easy to maintain consistent, so there is a time delay difference between the coaxial sub-units, affecting the transmission bandwidth of the cable. Summary of the Invention

[0005] The present invention provides a production method for a coaxial unit high-speed parallel transmission symmetrical cable, which can reduce the damage generated by the coaxial sub-units during the cabling process, realize the relative fixation of the positions between the coaxial sub-units, and reduce the time delay difference between the coaxial sub-units.

[0006] To solve the above problems, the production method for the coaxial unit high-speed parallel transmission symmetrical cable provided by the present invention adopts the following technical solutions: A production method for a coaxial unit high-speed parallel transmission symmetrical cable includes the following steps: S1: Conductor polishing, polishing the surface of the silver-plated copper wire with a diamond wire drawing die; S2: Insulation extrusion or winding forming, adopting a PTFE cable insulation extrusion process or a PTFE microporous tape cable insulation winding forming process; S3: Shielding winding, winding with an electronic-grade high-frequency ultra-low-profile copper foil (HVLP), and using a concentric active tape feeding constant tension winding machine for winding. During the winding process, the insulated wire core does not rotate, and the copper foil tape actively rotates and wraps around the surface of the insulated wire core; S4: Shielding shaping, with the restraint of a round hole die, reducing the outer diameter of the copper foil shielding semi-finished product after winding by 0.03 mm to 0.06 mm, so that the copper foils in the winding are in closer contact, the shape is more round, and the outer diameter size fluctuation is smaller; S5: Inner buffer layer winding, using a concentric active tape feeding constant tension winding machine for winding. During the winding process, the insulated wire core does not rotate, and the buffer tape actively rotates and wraps around the surface of the shielded wire core. The tension during the tape wrapping process is set according to 30% to 70% of the average breaking force of the buffer tape, so that the buffer tape can be tightly wrapped around the shield to form good buffer protection; S6: Filling and cabling. A 100% untwisting stranding machine is used for cabling. Meanwhile, an appropriate amount of dry cotton yarn is added to the gaps between the coaxial lines of each sub-unit to relatively fix the positions between the coaxial sub-units. During the cabling process, the pay-off tensions of each coaxial sub-unit are consistent, and an active pay-off process is adopted to reduce the damage caused to the coaxial sub-units due to pulling; S7: Wrapping of the outer buffer layer. It is wrapped in the same way as the inner buffer layer and is completed synchronously with the filling and cabling processes; S8: Braiding. Tinned or tinned copper-clad aluminum magnesium alloy wires are evenly braided and sleeved outside the semi-finished product after cabling; S9: Sheath forming. Polyvinyl chloride, low-smoke halogen-free polyolefin or cross-linked polyolefin is used to form a sheath through a tubular extrusion process.

[0007] The beneficial effects of the above solution are as follows: Using refined mirror silver-plated copper as the inner conductor can ensure that in the case of high frequencies, when the current flows on the silver layer on the surface of the silver-plated copper due to the skin effect, because the resistivity of silver is the lowest and the surface roughness is low, the effective resistance is relatively low, and the signal loss is small, so as to achieve a higher finished product transmission bandwidth; Using low-density microporous PTFE as the insulating dielectric material can ensure that the dielectric loss is the lowest among existing materials, so as to achieve a higher finished product transmission bandwidth; Using pure copper foil with extremely low surface roughness as the shielding outer conductor can ensure that in the case of high frequencies, when the current only flows on the surface of the copper foil due to the skin effect, the surface effective resistance of the copper foil is relatively low, and the signal loss is small; Using the mature concentric wrapping method can batch achieve an insulation concentricity of more than 96%; By combining multiple measures, a higher finished product transmission bandwidth can be achieved; A 100% untwisting stranding machine is used for cabling. Meanwhile, an appropriate amount of dry cotton yarn is added to the gaps between the coaxial lines of each sub-unit, so that the coaxial sub-units will not be damaged due to passive axial torsion during the cabling process. The appropriate amount of dry cotton yarn can relatively fix the positions between the coaxial sub-units, so that the coaxial sub-units will not easily displace and cause frictional collision damage, and the outer peripheral contour after cabling will be more round; During the cabling process, the pay-off tensions of each coaxial sub-unit are consistent, and an active pay-off process is adopted, which can minimize the damage caused to the coaxial sub-units due to pulling, maximize the physical length consistency between each coaxial sub-unit, and then reduce the delay difference between each coaxial sub-unit, so as to improve the transmission bandwidth of the cable.

[0008] Further, in step S1, the polished silver-copper surface meets the mirror standard, which means that under a 200-fold microscope, there are no protrusions, indentations, impurities, the silver layer is continuous without pinholes or copper leakage, the surface roughness is not greater than 0.2 um, the silver layer thickness is not less than 1 um, and conductors of different specifications use different sizes of conductors, and the fluctuation of the outer diameter of the conductor should be controlled within ±0.001 mm.

[0009] Further, in step S2, the outer diameter of the formed product is 0.03 mm to 0.06 mm larger than the preset outer diameter to leave a margin for subsequent processing, and the fluctuation of the outer diameter of the insulation molding is controlled within ±0.02 mm.

[0010] Further, in step S3, the tension during the taping process is set according to 50% to 70% of the average breaking force of the copper foil tape, so that the copper foil tape can be tightly wrapped on the insulation surface to form a well-contact and continuous shielded outer conductor.

[0011] Further, the overlapping coverage rate of the copper foils is not less than 40% and not greater than 49%. The principle is to make the surface flat and reduce the gap after wrapping. At the same time, the fluctuation of the outer diameter of the semi-finished product after wrapping the copper foil tape is controlled within ±0.04 mm.

[0012] Further, in step S4, while the round hole die compresses and reduces the diameter of the copper foil shield semi-finished product, the heating temperature of the semi-finished product is gradually increased until the die should be heated to 350 °C to 390 °C. The high-temperature die is used to shape the size and shape of the semi-finished product. After shaping, the semi-finished product is quickly cooled to ensure that the shape is cooled and solidified. During the heating process, nitrogen or other protective gases are used to protect the semi-finished product to prevent the copper foil from oxidizing.

[0013] The beneficial effects of the above solution are as follows: The function of heat setting is as follows: a. The temperature of 350 °C to 390 °C is higher than the annealing temperature of copper by about 270 °C, which completes the annealing of the copper foil, reduces the resistivity of the copper foil of the shielded outer conductor, and thus reduces the loss of the shielded outer conductor.

[0014] b. Under the action of high temperature and diameter reduction extrusion, the contact surfaces of the wound and overlapped copper foils produce a welding effect, further reducing the formation of the wound and overlapped copper foil shielded outer conductor into a whole, reducing the resistance, and thus reducing the loss of the shielded outer conductor.

[0015] c. The temperature of 350 °C to 390 °C can make the PTFE surface closely attached inside the copper foil of the shielded outer conductor melt and bond with the copper foil to form a stable overall structure.

[0016] d. After cooling, under the extrusion of the reduced outer diameter of the core, the density of the molten PTFE on the surface increases due to extrusion and reaches a solid state level of approximately 2.05 g / cm³, increasing the surface hardness and strength of the insulated core, improving the anti-extrusion deformation ability of the insulated core, making the insulated core not easily deformed or damaged during subsequent process operations, and ensuring the processability of the insulation.

[0017] Further, in step S5, when the inner buffer layer is wound, the shielding rate of the buffer tape on the surface of the shielded wire is not less than 90% and not more than 100%. Based on the principle of a flat surface and reduced gaps after winding, the outer diameter fluctuation of the semi-finished product after winding the buffer tape meets ±0.06 mm.

[0018] Further, during filling and cabling, when the number of transmission channels is less than 8, one cabling operation is performed; when the number of transmission channels is greater than or equal to 8, the cables of the transmission channels are cabled in two steps. In the first cabling process, the middle 2 pairs of 4 cores and the inner buffer layer are wound; in the second cabling, the semi-finished product of 2 pairs of 4 cores and the inner buffer layer completed in the first cabling is used as the central unit, and together with the remaining 6 pairs of 12-core coaxial sub-units and the filling cotton thread, a 100% untwisted cage cabling is performed, and at the same time, the outer buffer layer is wound.

[0019] Further, in step S8, the braiding density is not less than 80%. During braiding, the tension of the pay-off and take-up and the tension of the braiding wire are controlled to reduce the physical damage to the transmission unit, thereby improving the transmission bandwidth of the cable.

[0020] Further, before braiding, a layer of aluminum foil is wrapped around the cabled semi-finished product to further compensate for the shielding density of the braiding. The aluminum side of the aluminum foil faces outward, and a conductor is added between the aluminum foil and the braiding mesh as a ground wire for the later connection operation of the cable and the connector. Description of the Drawings

[0021] By referring to the accompanying drawings and reading the following detailed description, the above and other objects, features, and advantages of the exemplary embodiments of the present invention will become readily understood. In the drawings, several embodiments of the present invention are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, where: Figure 1 is a schematic structural diagram of a symmetric cable in the prior art; Figure 2 is a schematic diagram of the effective current-carrying area in a symmetric cable in the prior art; Figure 3 is a schematic structural diagram of a symmetric cable in the present invention; Figure 4 is a schematic diagram of the effective current-carrying area in a symmetric cable in the present invention; Figure 5Schematic diagram of a symmetrical cable with 8 pairs of transmission channels in the present invention; Figure 6 Flow chart of the production method of the coaxial unit high-speed parallel transmission symmetrical cable provided by the present invention; Explanation of reference numerals: 1. Metal conductor; 2. Insulating layer; 3. Metal shielding layer; 4. Effective current-carrying area; 5. Inner buffer layer; 6. Outer buffer layer; 7. Braid wire; 8. Sheath; 9. Filling cotton thread. Detailed implementation manners

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Those skilled in the art should know that the embodiments described below are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0023] Embodiment of the production method of the coaxial unit high-speed parallel transmission symmetrical cable provided by the present invention: As Figure 3 and Figure 4 shown, compared with the prior art, for the symmetrical cable produced by the production method of the coaxial unit high-speed parallel transmission symmetrical cable provided by the present invention, each cable includes a metal conductor 1, an insulating layer 2, a metal shielding layer 3 and an inner buffer layer 5, and the effective high-frequency current-carrying area 4 generated has small signal loss attenuation and can effectively improve the transmission bandwidth.

[0024] As Figure 6 shown, the production method of the coaxial unit high-speed parallel transmission symmetrical cable includes the following steps: S1: Conductor polishing, polishing the surface of the silver-plated copper wire with a diamond wire drawing die; S2: Insulation extrusion or winding forming, adopting the PTFE extrusion cable insulation process or the PTFE microporous tape winding cable insulation forming process; S3: Shielding winding, winding with an electronic-grade high-frequency ultra-low profile copper foil (HVLP), and using a concentric active tape feeding constant tension winding machine for winding. During the winding process, the insulated wire core does not rotate, and the copper foil tape actively rotates and wraps around the surface of the insulated wire core; S4: Shielding shaping, with the restraint of a round hole die, reducing the outer diameter of the copper foil shield semi-finished product after winding by 0.03 mm to 0.06 mm, so that the copper foils in the winding are in closer contact, the shape is more round, and the outer diameter size fluctuation is smaller; S5: Wrapping of the inner buffer layer, which is wrapped by a concentric active tape - feeding constant - tension wrapping machine. During the wrapping process, the insulated wire core does not rotate, and the buffer tape rotates actively to cover the surface of the shielded wire core. The tension during the tape - wrapping process is set at 30% to 70% of the average breaking force of the buffer tape, so that the buffer tape can be tightly wrapped on the shield surface to form good buffer protection. S6: Filling and cabling, which is carried out by a 100% untwisting stranding machine. At the same time, an appropriate amount of dry cotton yarn is added to the gaps between the coaxial lines of each sub - unit to keep the relative positions of the coaxial sub - units fixed. During the cabling process, the pay - off tensions of each coaxial sub - unit are the same, and an active pay - off process is adopted to reduce the damage caused by pulling on the coaxial sub - units. S7: Wrapping of the outer buffer layer, which is wrapped in the same way as the inner buffer layer and is completed synchronously with the filling and cabling process. S8: Braiding, where tinned or tinned copper - clad aluminum - magnesium alloy wires are evenly braided around the completed semi - finished product after cabling. S9: Sheath forming, using polyvinyl chloride or low - smoke halogen - free polyolefin or cross - linked polyolefin to form a sheath through a tubular extrusion process.

[0025] Specifically, in step S1, after polishing, the silver - copper surface meets the mirror standard, which means that under a 200 - fold microscope, there are no protrusions, indentations, impurities, the silver layer is continuous without pinholes or copper leakage, the surface roughness is not greater than 0.2 um, the silver layer thickness is not less than 1 um, and different - sized conductors are selected for different specifications. The fluctuation of the conductor outer diameter should be controlled within ±0.001 mm.

[0026] Using refined mirror - plated silver - copper as the inner conductor can ensure that in the case of high frequencies, when the current flows on the silver layer of the silver - copper surface due to the skin effect, because the resistivity of silver is the lowest and the surface roughness is low, the effective resistance is low, and the signal loss is small, so as to achieve a higher finished - product transmission bandwidth.

[0027] In step S2, the outer diameter of the formed product is 0.03 mm to 0.06 mm larger than the preset outer diameter to leave a margin for subsequent processing. The fluctuation of the insulated forming outer diameter is controlled within ±0.02 mm.

[0028] In step S3, the tension during the tape - wrapping process is set at 50% to 70% of the average breaking force of the copper - foil tape, so that the copper - foil tape can be tightly wrapped on the insulation surface to form a well - contacted and continuous shielded outer conductor.

[0029] At the same time, the overlapping coverage rate of the copper foils is not less than 40% and not more than 49%. Based on the principle of a flat surface and reduced gaps after wrapping, at the same time, the fluctuation of the outer diameter of the semi - finished product after wrapping the copper - foil tape is controlled within ±0.04 mm.

[0030] In step S4, while the round hole die compresses and reduces the diameter of the copper foil shield semi-finished product, the heating temperature of the semi-finished product is gradually increased until the die should be heated to 350°C to 390°C. The high-temperature die is used to shape the size and shape of the semi-finished product. After shaping, the semi-finished product is quickly cooled to ensure that the shape is cooled and solidified. During the heating process, nitrogen or other protective gases are used to protect the semi-finished product to prevent the copper foil from oxidizing.

[0031] The beneficial effects of the above solution are as follows: The function of heating and shaping is as follows: a. The temperature of 350°C to 390°C is about 270°C higher than the annealing temperature of copper, completing the annealing of the copper foil, reducing the resistivity of the shield outer conductor copper foil, and thus reducing the loss of the shield outer conductor.

[0032] b. Under the action of high temperature and diameter reduction extrusion, the contact surfaces of the overlapped copper foils generate a welding effect, further reducing the formation of the shield outer conductor of the overlapped copper foils into a whole, reducing the resistance, and thus reducing the loss of the shield outer conductor.

[0033] c. The temperature of 350°C to 390°C can make the surface of the PTFE closely attached inside the shield outer conductor copper foil melt and bond with the copper foil to form a stable overall structure.

[0034] d. After cooling, under the extrusion of the reduced outer diameter of the wire core, the density of the surface-melted PTFE increases due to extrusion, reaching a solid state level of about 2.05 g / cm³, increasing the surface hardness and strength of the insulated wire core, improving the anti-extrusion deformation ability of the insulated wire core, making the insulated wire core not easily deformed and damaged during subsequent process operations, and ensuring the processability of the insulation.

[0035] In step S5, when the inner buffer layer is wrapped, the shielding rate of the buffer tape on the surface of the shielded wire is not less than 90% and not more than 100%. Based on the principle of a flat surface and reduced gaps after wrapping, the outer diameter fluctuation of the semi-finished product after wrapping the buffer tape meets ±0.06 mm.

[0036] During filling and cabling, when the number of transmission channels is less than 8, a single cabling operation is performed; When the number of transmission channels is greater than or equal to 8, as Figure 5 shown, the symmetrical cable includes a metal conductor 1, an insulating layer 2, a metal shielding layer 3, an inner buffer layer 5, filling cotton threads 9, an outer buffer layer 6, braided wires 7, and a sheath 8; for the cable with transmission channels, cabling is performed in two steps. In the first cabling process, the middle 2 pairs of 4 cores and the inner buffer layer are wrapped; during the second cabling, the semi-finished product of the 2 pairs of 4 cores and the inner buffer layer completed in the first cabling is used as the central unit, and together with the remaining 6 pairs of 12-core coaxial sub-units and filling cotton threads, a 100% untwisted cage cabling is performed, and at the same time, the outer buffer layer is wrapped.

[0037] In order to compensate for the physical lengths of the 2 pairs of 4-core coaxial sub-units in the central unit and the 6 pairs of 12-core coaxial sub-units around it to be as consistent as possible after the second cabling, it is necessary to appropriately reduce the cabling pitch during the first cabling and appropriately increase the cabling pitch during the second cabling, so as to make the physical lengths of all coaxial sub-units as consistent as possible, thereby reducing the delay difference between coaxial sub-units and improving the transmission bandwidth of the cable.

[0038] In step S8, the braiding density is not less than 80%. During braiding, control the tension of the pay-off and take-up and the tension of the braiding wire to reduce physical damage to the transmission unit, thereby improving the transmission bandwidth of the cable.

[0039] Before braiding, a layer of aluminum foil is wrapped around the semi-finished cable to further compensate for the shielding density of the braiding. The aluminum side of the aluminum foil faces outward, and a conductor is added between the aluminum foil and the braiding mesh as a ground wire to facilitate the connection operation between the cable and the connector in the later stage.

[0040] Based on the above description of this specification, those skilled in the art can also understand the following terms used, such as terms indicating orientation or positional relationship like "upper", "lower", "front", "rear", "left", "right", "width", "horizontal", "top", "bottom", "inner", "outer", etc. These terms are based on the orientation or positional relationship shown in the drawings of this specification. They are only for the purpose of facilitating the description of the solution of the present invention and simplifying the description, rather than explicitly or implicitly indicating that the devices or elements involved must have the specific orientation, be constructed and operated in the specific orientation. Therefore, the above terms of orientation or positional relationship cannot be understood or interpreted as a limitation to the solution of the present invention.

[0041] In addition, in the description of this specification, the meaning of "a plurality" is at least two, such as two, three or more, etc., unless otherwise specifically and clearly defined.

Claims

1. A production method of a coaxial unit high-speed parallel transmission symmetrical cable, characterized in that It includes the following steps: S1: Conductor polishing; S2: Insulation extrusion or wrapping forming; S3: Shield wrapping, using an electronic-grade high-frequency ultra-low-profile copper foil (HVLP) for wrapping, and using a concentric active tape-releasing constant-tension wrapping machine for wrapping. During the wrapping process, the insulated core does not rotate, and the copper foil tape actively rotates to wrap around the surface of the insulated core; S4: Shield shaping. With the restraint of a round-hole die, the outer diameter of the semi-finished copper foil shield after wrapping is extruded and reduced by 0.03 mm to 0.06 mm, so that the copper foils in the wrapping are in closer contact, the shape is more round, and the outer diameter size fluctuation is smaller; S5: Inner buffer layer wrapping, using a concentric active tape-releasing constant-tension wrapping machine for wrapping. During the wrapping process, the insulated core does not rotate, and the buffer tape actively rotates to wrap around the surface of the shielded core. The tension during the tape wrapping process is set at 30% to 70% of the average breaking force of the buffer tape, so that the buffer tape can be tightly wrapped on the shield surface to form good buffer protection; S6: Filling and cabling, using a 100% untwisting stranding machine for cabling. At the same time, an appropriate amount of dry cotton yarn is added to the gaps between the coaxial lines of each sub-unit to keep the positions of the coaxial sub-units relatively fixed. During the cabling process, the pay-off tensions of each coaxial sub-unit are consistent, and an active pay-off process is adopted to reduce the damage caused to the coaxial sub-units by pulling; S7: Outer buffer layer wrapping; S8: Braiding; S9: Sheath forming.

2. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to claim 1, characterized in that In step S1, after polishing, the silver-copper surface reaches the mirror standard, that is, there are no protrusions and depressions, no impurities, and the silver layer is continuous without pinholes and copper leakage when observed under a 200-fold microscope. The surface roughness is not greater than 0.2 um, the silver layer thickness is not less than 1 um, and different sizes of conductors are selected for different specifications. The fluctuation of the conductor outer diameter should be controlled within ±0.001 mm.

3. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to claim 2, characterized in that, In step S2, the outer diameter of the formed product is 0.03 mm to 0.06 mm larger than the preset outer diameter to leave a margin for subsequent processing. The fluctuation of the insulation forming outer diameter is controlled within ±0.02 mm.

4. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to any one of claims 1 to 3, characterized in that, In step S3, the tension during the tape wrapping process is set at 50% to 70% of the average breaking force of the copper foil tape, so that the copper foil tape can be tightly wrapped on the insulation surface to form a well-contact and continuous shielded outer conductor.

5. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to claim 4, characterized in that, The mutual overlapping coverage rate of the copper foils is not less than 40% and not greater than 49%. Based on the principle of a flat surface and reduced gaps after wrapping, at the same time, the outer diameter fluctuation of the semi-finished product after wrapping the copper foil tape is controlled within ±0.04 mm.

6. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to any one of claims 1 to 3, characterized in that In step S4, while the round-hole die compresses and reduces the diameter of the copper foil shield semi-finished product, the heating temperature of the semi-finished product is gradually increased until the die should be heated to 350 °C to 390 °C. The high-temperature die is used to shape the size and shape of the semi-finished product. After shaping, the semi-finished product is quickly cooled to ensure that the shape is cooled and solidified. During the heating process, nitrogen or other protective gases are used to protect the semi-finished product to prevent copper foil oxidation.

7. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to any one of claims 1 to 3, characterized in that, In step S5, when the inner buffer layer is wrapped, the shielding rate of the buffer tape on the surface of the shielded wire is not less than 90% and not more than 100%. Based on the principle of a flat surface and reduced gaps after wrapping, the outer diameter fluctuation of the semi-finished product after wrapping the buffer tape meets ±0.06 mm.

8. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to any one of claims 1 to 3, characterized in that, During filling and cabling, when the number of transmission channels is less than 8, one cabling operation is performed. When the number of transmission channels is greater than or equal to 8, the cables of the transmission channels are cabled in two steps. In the first cabling process, the middle 2 pairs of 4 cores and the inner buffer layer are wrapped. In the second cabling, the semi-finished product of the 2 pairs of 4 cores and the inner buffer layer completed in the first cabling is used as the central unit, and together with the remaining 6 pairs of 12-core coaxial sub-units and filling cotton threads, a 100% untwisted cage cabling is performed, and at the same time, the outer buffer layer is wrapped.

9. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to any one of claims 1 to 3, characterized in that, In step S8, the braiding density is not less than 80%. During braiding, the tension of the pay-off and take-up and the tension of the braiding wires are controlled to reduce physical damage to the transmission unit, thereby improving the transmission bandwidth of the cable.

10. The production method of the coaxial unit high-speed parallel transmission symmetrical cable according to claim 9, characterized in that, Before braiding, the semi-finished cabling product is coated with a layer of aluminum foil to further compensate for the shielding density of the braiding. The aluminum side of the aluminum foil faces outward, and a conductor is added between the aluminum foil and the braiding mesh as a ground wire for later connection operations between the cable and the connector.

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