A kind of serial extrusion equipment for photovoltaic cable production

Abstract

This invention provides a tandem extrusion device for photovoltaic cable production, including a tandem extrusion shell structure. The tandem extrusion shell structure has an internal tandem extrusion guide structure, and one side of the tandem extrusion shell structure is rotatably connected to an extrusion surface smoothing structure. This invention is rationally designed. By setting the extrusion surface smoothing structure at the discharge end of the tandem extrusion shell structure, during the critical stage when the inner insulation layer is in a molten or highly elastic state, a servo motor drives a drive gear, which, through meshing with an internal meshing gear ring, drives the mounting plate and rotating tube to rotate around the cable axis. This continuously rounds and smooths the outer surface of the insulation layer, effectively eliminating problems of uneven wall thickness and outer diameter fluctuations, improving insulation layer performance and cable operational reliability. Furthermore, it is fully compatible with continuous tandem extrusion production processes and does not affect existing production efficiency.

Description

Technical Field

[0001] This invention mainly relates to the field of photovoltaic cables, and specifically to a tandem extrusion equipment for the production of photovoltaic cables. Background Technology

[0002] With the rapid development of the global photovoltaic new energy industry, the installed capacity of photovoltaic power plants continues to expand. As a core supporting component for power transmission and safety protection in photovoltaic power generation systems, the quality and performance stability of photovoltaic cables directly determine the long-term operational reliability and service life of photovoltaic systems. The tandem extrusion process, also known as the dual-machine series continuous extrusion process, can achieve continuous extrusion molding of the inner insulation layer and the outer sheath layer of photovoltaic cables compared to the traditional step extrusion process. After the insulation layer is extruded by the first extruder, it does not need to be cooled and wound up. It directly enters the sheath extrusion die of the second extruder in a molten / semi-molten state to complete the sheath layer coating. This greatly shortens the production process, improves production efficiency, and reduces production turnover costs. Therefore, it has been widely used in the large-scale production of photovoltaic cables.

[0003] During the operation of specific embodiments, the inventors discovered the following defects: Due to the special nature of the tandem extrusion process, the inner insulating layer is not cooled and shaped after extrusion and remains in a deformable state of molten or highly elasticity. The roughness of its inner wall directly translates into uneven wall thickness and fluctuations in outer diameter of the insulating layer itself: at the convex positions of the inner wall, the effective wall thickness of the insulating layer is reduced, and the outer diameter of the insulating layer at the corresponding position is smaller; at the concave positions of the inner wall, the effective wall thickness of the insulating layer is increased, and the outer diameter of the insulating layer at the corresponding position is larger; and the irregular random defects of the inner wall will cause continuous and irregular dynamic fluctuations in the outer diameter of the insulating layer.

[0004] It should be noted that the above content falls within the scope of the inventor's technical knowledge. Due to the vast and complex nature of the technical content in this field, the above content of this application does not necessarily constitute prior art. Summary of the Invention

[0005] 1. The technical problem that the invention aims to solve: This invention provides a tandem extrusion device for photovoltaic cable production, which solves the technical problems existing in the background art.

[0006] 2. Technical Solution: To achieve the above objectives, the technical solution provided by the present invention is as follows: a series extrusion equipment for photovoltaic cable production, comprising a series extrusion shell structure, wherein a series extrusion wire passing structure is provided inside the series extrusion shell structure, and a smooth extrusion surface structure is rotatably connected to one side of the series extrusion shell structure. The extrusion surface smooth structure includes a rotating tube, a mounting plate, and an internal meshing toothed ring. The feed end of the rotating tube is rotatably engaged with the discharge end of the tandem extrusion shell structure. The mounting plate is coaxially fixed to the discharge end of the rotating tube, and the internal meshing toothed ring is coaxially fixed to the inner sidewall of the mounting plate. The extruded housing structure includes a housing body and a servo motor. The output end of the servo motor is coaxially provided with a drive gear, which meshes with the internal meshing gear ring to drive the rotating tube to rotate around its own axis.

[0007] Furthermore, the inlet and outlet ends of the housing body are both coaxially provided with connecting pipes, the top of the housing body is fixed with an installation pipe, the servo motor is fixed to the outer side wall of the installation pipe, and the drive gear is housed inside the installation pipe.

[0008] Furthermore, a tapered guide groove is provided on the inner wall of the feed end of the rotating tube. The inner diameter of the tapered guide groove gradually decreases from the cable feed direction to the discharge direction. A wire feeding groove is provided on the inner wall of the rotating tube, and the wire feeding groove extends along the axial direction of the rotating tube.

[0009] Furthermore, the tandem extrusion line structure includes a positioning housing, which is coaxially and detachably connected to the interior of the tandem extrusion housing structure. The interior of the positioning housing has a placement chamber, and both ends of the positioning housing have coaxially formed threading holes that communicate with the placement chamber. The threading holes are coaxially arranged with the rotating tube.

[0010] Furthermore, a sealing plate is slidably connected to the bottom opening of the positioning housing, and a fixing bolt is rotatably connected to the sealing plate. The fixing bolt is threadedly connected to the bottom of the tandem extrusion housing structure.

[0011] Furthermore, the bottom of the mounting tube is connected to the internal cavity of the housing body, and the bottom of the drive gear extends to the discharge end of the mounting tube, forming an internal meshing transmission engagement with the internal meshing gear ring.

[0012] Furthermore, the inner wall of the rotating tube is provided with a wear-resistant and smooth coating, and the wire feeding groove is a spiral groove that extends spirally along the axial direction of the rotating tube.

[0013] 3. Beneficial effects: Compared with the prior art, the technical solution provided by this invention has the following advantages: This invention, by setting a smooth extrusion surface structure at the discharge end of the tandem extrusion shell structure, allows for continuous circumferential smoothing and ironing of the outer surface of the insulation layer during the critical stage when the inner insulation layer is in a molten or highly elastic state. A servo motor drives the active gear, which, through meshing with the internal meshing gear ring, drives the mounting plate and rotating tube to rotate around the cable axis. This effectively eliminates problems such as uneven wall thickness and outer diameter fluctuations, improves the performance of the insulation layer and the reliability of cable operation, and is fully compatible with continuous tandem extrusion production processes without affecting the original production efficiency. The tandem extrusion housing structure adopts an integrated and highly adaptable design. It can be quickly connected to the front and rear extrusion equipment through the connecting pipes at both ends of the housing body, adapting to the transformation and upgrading of existing tandem extrusion production lines. The transformation cost is low and the adaptability is strong. The mounting pipe at the top of the housing body provides a sealed protective space for the servo motor and the drive gear, ensuring transmission stability and accuracy. At the same time, it realizes the integration of the drive structure and the extrusion cavity, greatly reducing the space occupied by the equipment. The structure is compact and the layout is reasonable. The tandem extrusion cable guide structure enables precise coaxial positioning and convenient operation and maintenance of cables. The tandem extrusion cable guide structure inside the housing can coaxially limit the cable through coaxial through-holes at both ends of the positioning housing, preventing cable sway from exacerbating uneven wall thickness. The placement chamber inside the positioning housing can accommodate different specifications of cable guide cores, offering strong versatility. Furthermore, the sealing plate and fixing bolts enable detachable locking, facilitating disassembly and maintenance, reducing operational difficulty, and improving production changeover efficiency. Attached Figure Description

[0014] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a three-dimensional cross-sectional structural diagram of the present invention; Figure 3 This is a three-dimensional structural diagram of the mounting plate of the present invention; Figure 4 This is a schematic diagram of the three-dimensional structure of the rotating ring of the present invention; Figure 5 This is a schematic diagram of the three-dimensional structure of the rotating ring of the present invention.

[0015] Figure label: 1. Serial extrusion shell structure; 101. Shell body; 102. Connecting pipe; 103. Mounting pipe; 104. Servo motor; 105. Drive gear; 2. Serial extrusion line passing structure; 201. Positioning shell; 202. Sealing plate; 203. Fixing bolt; 204. Placement chamber; 205. Wire hole; 3. Smooth extrusion surface structure; 301. Rotating tube; 302. Guide groove; 303. Wire feeding groove; 304. Mounting plate; 305. Internal meshing toothed ring. Detailed Implementation

[0016] To facilitate understanding of the present invention, a more complete description of the invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be more thorough and complete.

[0017] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "page," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0019] In this invention, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," "fixed," "provided with," and "located in" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Example

[0020] See attached document Figures 1-5 A tandem extrusion equipment for photovoltaic cable production includes a tandem extrusion housing structure 1, an extrusion wire passing structure 2 is provided inside the tandem extrusion housing structure 1, and an extrusion surface smoothing structure 3 is rotatably connected to one side of the tandem extrusion housing structure 1. The tandem extrusion shell structure 1 is the main load-bearing structure of this equipment, used to realize the docking and installation with the upstream and downstream tandem extrusion production lines, and at the same time to provide installation and protection space for the tandem extrusion line passing structure 2 and the extrusion surface smooth structure 3; The cascade extrusion guide structure 2 is used to coaxially guide and limit the conductor and molten insulation layer of the photovoltaic cable, ensuring that the cable travels stably along the axis of the equipment during the cascade extrusion process and avoiding swaying or deviation. The extrusion surface smoothing structure 3 is used to perform circumferential rounding and surface ironing treatment on the photovoltaic cable insulation layer that has just been extruded and is still in a molten or highly elastic state, to eliminate uneven insulation layer wall thickness, outer diameter fluctuation and surface defects, and improve the forming quality of photovoltaic cable. The extrusion surface smooth structure 3 includes a rotating tube 301, a mounting plate 304, and an internal meshing toothed ring 305. The feed end of the rotating tube 301 is rotatably engaged with the discharge end of the tandem extrusion shell structure 1. The mounting plate 304 is coaxially fixed to the discharge end of the rotating tube 301. The internal meshing toothed ring 305 is coaxially fixed to the inner sidewall of the mounting plate 304. A tapered guide groove 302 is provided on the inner wall of the feed end of the rotating tube 301. The inner diameter of the tapered guide groove 302 gradually decreases from the cable feed direction to the discharge direction. A wire feeding groove 303 is provided on the inner wall of the rotating tube 301. The wire feeding groove 303 extends along the axial direction of the rotating tube 301. The inner wall of the rotating tube 301 is provided with a wear-resistant smooth coating. The wire feeding groove 303 is a spiral groove that extends spirally along the axial direction of the rotating tube 301. The rotating tube 301 is a cylindrical tubular structure with both ends open. Its inner cavity is a circular channel for cable extrusion molding. The feed end of the rotating tube 301 and the discharge end of the cascade shell structure 1 are connected by bearings to form a rotational fit, so that the rotating tube 301 can rotate freely around its own axis relative to the cascade shell structure 1. The axis of the rotating tube 301 is coaxial with the feed and discharge center axes of the cascade shell structure 1, ensuring that the cable is always in a coaxial state during the cable travel and avoiding eccentric scraping.

[0021] The mounting plate 304 has an annular disc structure. The inner ring of the mounting plate 304 is coaxially fixedly connected to the outer wall of the discharge end of the rotating tube 301 by welding or interference fit, so that the mounting plate 304 can rotate synchronously with the rotating tube 301. The internal meshing gear ring 305 is a ring-shaped internal gear structure. The outer ring of the internal meshing gear ring 305 is coaxially fixed to the inner side wall of the mounting plate 304 by bolt locking or welding. The internal teeth of the internal meshing gear ring 305 mesh with the drive gear 105 of the extrusion housing structure 1. The power of the servo motor 104 is transmitted to the rotating tube 301 through gear transmission, driving the rotating tube 301 to rotate around its own axis.

[0022] A conical guide groove 302 is provided on the inner wall of the feed end of the rotary tube 301. The conical guide groove 302 is a frustum-shaped inner cavity structure. Its inner diameter gradually decreases from the cable feeding direction to the discharge direction. The maximum inner diameter of the conical guide groove 302 matches the inner diameter of the discharge port of the tandem extrusion shell structure 1, and the minimum inner diameter smoothly transitions with the inner diameter of the main body cavity of the rotary tube 301. The conical guide groove 302 is used to smoothly guide the molten cable that has just been extruded from the tandem extrusion shell structure 1, so that the cable smoothly enters the circular inner cavity of the rotary tube 301, avoiding rigid scraping and abrasion between the cable and the feed end port of the rotary tube 301 during feeding, which would cause surface damage and ensure the continuity and surface integrity of the cable extrusion. The inner wall of the rotating tube 301 is provided with a wear-resistant and smooth coating. The wear-resistant and smooth coating can be a polytetrafluoroethylene coating or a ceramic wear-resistant coating, and the coating thickness is 50-200μm. On the one hand, this coating can significantly reduce the coefficient of friction between the inner wall of the rotating tube 301 and the surface of the molten cable, reduce frictional damage to the cable surface, and improve the smoothing effect. On the other hand, it can enhance the wear resistance and corrosion resistance of the inner wall of the rotating tube 301, extend the service life of the rotating tube 301, and reduce the equipment replacement and maintenance costs.

[0023] The extrusion shell structure 1 includes a shell body 101 and a servo motor 104. The output end of the servo motor 104 is coaxially provided with a drive gear 105. The drive gear 105 meshes with the internal meshing gear ring 305 to drive the rotating tube 301 to rotate around its own axis. The feed end and the discharge end of the shell body 101 are both coaxially provided with connecting pipes 102. The top of the shell body 101 is fixed with an installation tube 103. The servo motor 104 is fixed to the outer side wall of the installation tube 103. The drive gear 105 is housed inside the installation tube 103. The bottom of the installation tube 103 is connected to the internal cavity of the shell body 101. The bottom of the drive gear 105 extends to the discharge end of the installation tube 103 and forms an internal meshing transmission cooperation with the internal meshing gear ring 305. The servo motor 104 is fixedly installed on the top outer wall of the housing body 101. The output end of the servo motor 104 is set towards the discharge end of the housing body 101. The output end of the servo motor 104 is coaxially fixedly connected to the drive gear 105 through a coupling. The drive gear 105 meshes with the internal meshing gear ring 305 to form an internal meshing gear transmission pair. The servo motor 104 is used to provide rotational drive power. Through the meshing transmission between the drive gear 105 and the internal meshing gear ring 305, it drives the rotating tube 301 to rotate around its own axis. The servo motor 104 can adjust the speed through frequency conversion control to adapt to the production needs of photovoltaic cables with different specifications and different extrusion speeds. It is flexible in adjustment and highly adaptable.

[0024] Both the inlet and outlet ends of the housing body 101 are coaxially fixed with connecting pipes 102. The connecting pipes 102 are tubular structures with both ends through, used to allow the material wrapped around the outer wall of the cable to enter the gap between the positioning housing 201 and the housing body 101.

[0025] An installation tube 103 is fixedly provided on the top outer wall of the housing body 101. The installation tube 103 is a tubular structure with an open bottom. The bottom opening of the installation tube 103 is connected to the internal cavity of the housing body 101. The internal cavity of the installation tube 103 corresponds to the discharge end position of the housing body 101. The servo motor 104 is fixed to the outer wall of the mounting tube 103 by bolts. The output end of the servo motor 104 extends into the inner cavity of the mounting tube 103. The drive gear 105 is housed in the top of the mounting tube 103. The drive structure and the extrusion cavity are integrated on the housing body 101, which greatly reduces the overall space occupied by the equipment, making the equipment structure more compact and the layout more reasonable, and adapting to the compact installation requirements of the production line.

[0026] Furthermore, the extrusion line structure 2 includes a positioning housing 201, which is coaxially and detachably connected to the interior of the extrusion housing structure 1. The positioning housing 201 has a placement chamber 204 inside. Both ends of the positioning housing 201 have coaxially opened wire-passing holes 205 that communicate with the placement chamber 204. The wire-passing holes 205 are coaxially arranged with the rotating tube 301. A sealing plate 202 is slidably connected to the bottom opening of the positioning housing 201. A fixing bolt 203 is rotatably connected to the sealing plate 202. The fixing bolt 203 is threadedly connected to the bottom of the extrusion housing structure 1. The positioning housing 201 has an internal placement chamber 204, which is a cylindrical inner cavity used to accommodate wire guide cores that are compatible with different wire diameter specifications. The wire guide cores with the corresponding inner diameter can be replaced according to the specifications and models of the photovoltaic cables to be produced, so as to meet the production needs of photovoltaic cables with different wire diameters and greatly improve the versatility of the equipment.

[0027] Both the inlet and outlet ends of the positioning housing 201 are coaxially provided with wire-passing holes 205 that communicate with the placement chamber 204. The inner diameter of the wire-passing hole 205 is adapted to the inner hole of the wire-passing mold core in the placement chamber 204. The wire-passing hole 205 is coaxially arranged with the inner cavity of the rotating tube 301. The conductor of the photovoltaic cable enters the positioning housing 201 through the wire-passing hole 205 at the feeding end. After being coaxially limited by the wire-passing die core in the placement chamber 204, it passes out through the wire-passing hole 205 at the discharge end and enters the subsequent extrusion molding stage. Through the cooperation of the wire-passing hole 205 and the wire-passing die core, the cable conductor and the inner insulation layer can be precisely coaxially limited during the tandem extrusion process. This ensures that the cable travels in a straight line along the axis of the equipment throughout the process, avoiding swaying or deviation of the cable during extrusion, which would aggravate the problem of uneven insulation layer wall thickness and improve the molding uniformity of the insulation layer from the source.

[0028] The bottom of the positioning housing 201 has a bottom opening that communicates with the placement chamber 204. A sealing plate 202 is slidably connected to the bottom opening. The outer dimensions of the sealing plate 202 are adapted to the dimensions of the bottom opening of the positioning housing 201, which can seal the bottom opening and prevent molten plastic from entering the placement chamber 204. A fixing bolt 203 is rotatably connected to the center of the sealing plate 202. The bottom of the housing body 101 has a threaded through hole adapted to the fixing bolt 203. The screw end of the fixing bolt 203 passes through the sealing plate 202 and is threadedly connected to the threaded through hole at the bottom of the housing body 101. When the fixing bolt 203 is tightened, the sealing plate 202 can be driven to push the positioning housing 201 upward, thereby locking the positioning housing 201 into the internal cavity of the housing body 101. When the fixing bolt 203 is loosened, the sealing plate 202 can slide downwards, releasing the locking limit on the positioning housing 201. The positioning housing 201 can then be removed from the housing body 101 to complete operations such as replacing the wire guide core and cleaning the placement chamber 204. The disassembly and maintenance are convenient, which can greatly reduce the difficulty of equipment operation and maintenance and improve the efficiency of model changeover during production.

[0029] According to the specifications and model of the photovoltaic cable to be produced, the corresponding wire guide die core is installed in the placement chamber 204 of the positioning housing 201, the positioning housing 201 is installed into the inner cavity of the housing body 101, and the fixing bolts 203 are tightened to complete the locking and fixing; through the connecting pipes 102 at both ends of the housing body 101, the equipment is connected to the photovoltaic cable tandem extrusion production line, so that the feeding end of the equipment is connected to the die head of the insulation extruder, and the discharging end is connected to the subsequent sheath extrusion equipment or cooling equipment.

[0030] During the production process, the photovoltaic cable conductor enters the interior of the positioning housing 201 and passes through the wire hole 205 into the interior of the rotating tube 301. At the same time, there is a gap between the rotating tube 301 and the positioning housing 201 to wrap the cable on the outer wall by the principle of melting. Then the cable enters the wire release groove 303 inside the rotating tube 301.

[0031] At this time, the servo motor 104 starts and drives the drive gear 105 to rotate. Through the internal meshing transmission between the drive gear 105 and the internal meshing gear ring 305, the mounting plate 304 and the rotating tube 301 rotate synchronously around the cable axis. The inner wall of the rotating tube 301 continuously performs circumferential rounding and ironing treatment on the outer surface of the molten insulation layer, eliminating the problems of uneven wall thickness and irregular fluctuation of outer diameter caused by defects in the inner wall of the insulation layer. At the same time, the cable discharge groove 303 collects a small amount of overflow material to avoid surface scratches. Finally, the processed cable is sent out from the discharge end of the rotating tube 301 and enters the subsequent production process.

[0032] The above-described embodiments are merely illustrative of certain implementations of the present invention, and are described in a relatively specific and detailed manner. However, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A cascade extrusion device for photovoltaic cable production, characterized in that: include The tandem extrusion shell structure (1) has a tandem extrusion line passing structure (2) inside, and a smooth extrusion surface structure (3) is rotatably connected to one side of the tandem extrusion shell structure (1). The extrusion surface smooth structure (3) includes a rotating tube (301), a mounting plate (304), and an internal meshing toothed ring (305). The feed end of the rotating tube (301) is rotatably engaged with the discharge end of the tandem extrusion shell structure (1). The mounting plate (304) is coaxially fixed to the discharge end of the rotating tube (301), and the internal meshing toothed ring (305) is coaxially fixed to the inner sidewall of the mounting plate (304). The extrusion shell structure (1) includes a shell body (101) and a servo motor (104). The output end of the servo motor (104) is coaxially provided with a drive gear (105). The drive gear (105) meshes with the internal meshing gear ring (305) to drive the rotating tube (301) to rotate around its own axis.

2. The cascade extrusion equipment for photovoltaic cable production according to claim 1, characterized in that: The infeed end and the discharge end of the housing body (101) are both coaxially provided with connecting pipes (102), the top of the housing body (101) is fixed with an installation pipe (103), the servo motor (104) is fixed to the outer side wall of the installation pipe (103), and the drive gear (105) is housed inside the installation pipe (103).

3. The cascade extrusion equipment for photovoltaic cable production according to claim 1, characterized in that: The inner wall of the feed end of the rotating tube (301) is provided with a conical guide groove (302). The inner diameter of the conical guide groove (302) gradually decreases from the cable feed direction to the discharge direction. The inner wall of the rotating tube (301) is provided with a wire feeding groove (303). The wire feeding groove (303) extends along the axial direction of the rotating tube (301).

4. The cascade extrusion equipment for photovoltaic cable production according to claim 1, characterized in that: The extrusion line structure (2) includes a positioning housing (201), which is coaxially and detachably connected to the interior of the extrusion housing structure (1). The positioning housing (201) has a placement chamber (204) inside. Both ends of the positioning housing (201) have wire holes (205) coaxially connected to the placement chamber (204). The wire holes (205) are coaxially arranged with the rotating tube (301).

5. The cascade extrusion equipment for photovoltaic cable production according to claim 4, characterized in that: A sealing plate (202) is slidably connected to the bottom opening of the positioning housing (201), and a fixing bolt (203) is rotatably connected to the sealing plate (202). The fixing bolt (203) is threadedly connected to the bottom of the tandem extrusion housing structure (1).

6. The cascade extrusion equipment for photovoltaic cable production according to claim 2, characterized in that: The bottom of the mounting tube (103) is connected to the internal cavity of the housing body (101), and the bottom of the drive gear (105) extends to the discharge end of the mounting tube (103) to form an internal meshing transmission engagement with the internal meshing gear ring (305).

7. The cascade extrusion equipment for photovoltaic cable production according to claim 1, characterized in that: The inner wall of the rotating tube (301) is provided with a wear-resistant and smooth coating, and the wire feeding groove (303) is a spiral groove that extends spirally along the axial direction of the rotating tube (301).

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