Manufacturing method of aluminum alloy hub coated with carbon fibers

Abstract

The invention provides a manufacturing method of a carbon fiber coated aluminum alloy hub, which comprises the following steps of: paving a layer of raw silica gel at a position, corresponding to a hub to be paved, in a mold, and vacuumizing after closing the mold; putting the mold into an autoclave, and heating and curing to form a silicon rubber case mold; coating a bonding layer at the position, needing to be paved, of the hub; carbon fiber materials are laid on the corresponding positions of the hub; sleeving the hub paved with the carbon fibers with the obtained silica gel sleeve mold, then putting the hub into a vacuum bag, vacuumizing, and putting the hub into an autoclave for curing and forming a coating piece; and the wrapping part is taken out of the autoclave, the vacuum bag is removed, then the silicon rubber sleeve mold is taken down, and the hub wrapped with the carbon fibers is obtained. According to the manufacturing method of the aluminum alloy hub coated with the carbon fibers, the corresponding silicon rubber sleeve mold is manufactured through the mold, the hub paved with the carbon fibers is sleeved with the silicon rubber sleeve mold, then curing forming is conducted, the aluminum alloy hub coated with the carbon fibers can be obtained after mold opening, the manufacturing process is simple, the cost is low, and the product yield is high.

Description

Technical Field

[0001] The present application belongs to the technical field of composite wheel hub manufacturing, and more specifically, relates to a method for manufacturing a carbon fiber-coated aluminum alloy wheel hub. Background Art

[0002] The wheel hub is an important component of the wheel. Most existing wheel hubs are made of steel or aluminum alloy. Some wheel hubs are made of composite materials, such as carbon fiber composite materials. Carbon fiber material is coated on the surface of the aluminum alloy wheel hub. The combination of the two can improve performance and enhance the beauty of the product.

[0003] As the application of carbon fiber composite materials in the automotive industry gradually increases, the application of carbon fiber composite car wheels is also gradually increasing. Carbon fiber composite wheels are gradually extended from racing to passenger cars. The molding technology of carbon fiber composite products plays a key role in determining cost and quality. The existing carbon fiber composite wheel manufacturing process is relatively complicated, and the yield rate of the product after molding is not high. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a method for manufacturing a carbon fiber-coated aluminum alloy wheel hub with simple process and good molding quality.

[0005] To achieve the above objectives, the technical solution adopted in this application is to provide a method for manufacturing a carbon fiber-coated aluminum alloy wheel hub, comprising:

[0006] The following steps are involved:

[0007] Step S20, laying a layer of raw silicone rubber at the position where the wheel hub needs to be laid in the mold, and then closing the mold and vacuuming it;

[0008] Step S30, placing the mold into an autoclave, heating and curing it to form a silicone sleeve mold, and then taking out the silicone sleeve mold;

[0009] Step S40, applying an adhesive layer to the location on the wheel hub where the cloth needs to be laid, and leaving it for a predetermined time;

[0010] Step S50, laying the carbon fiber material on the corresponding position of the wheel hub;

[0011] Step S60, the obtained silicone sleeve mold is put on the wheel hub covered with carbon fiber, and then placed in a vacuum bag, evacuated, and placed in an autoclave for curing to form a covering part;

[0012] Step S70: Take out the covering part from the autoclave, remove the vacuum bag, and then remove the silicone sleeve mold to obtain a wheel hub covered with carbon fiber.

[0013] In one embodiment, before step S40, the method further includes:

[0014] Step S31: performing a roughening process on the position of the aluminum alloy wheel hub corresponding to the position where the carbon fiber coating is required;

[0015] Step S32: Clean the aluminum alloy wheel hub after the roughening treatment, put it into the oven and bake it dry at a temperature of 54-80 degrees and a baking time of 6-20 minutes.

[0016] In one embodiment, step S80 is further included after step S70: removing burrs and trimming the obtained wheel hub coated with carbon fiber, covering the portion not coated with carbon fiber with protective paper or protective tooling after trimming, and then performing a roughening treatment.

[0017] In one embodiment, step S91 is further included after step S80: first coat of paint treatment: after the roughening treatment is completed, the product is subjected to the first coarse grinding to remove white spots, the white spots on the product are ground off, the uneven positions are smoothed, and the positions with large unevenness are patched; after the patching is completed, it is cleaned and then sprayed with oil, and then left to stand for 1-3 hours, and then baked, the baking temperature is 65-95 degrees, and the baking time is 1-3 hours.

[0018] In one embodiment, step S92 is further included after step S91: second coat of paint treatment: the product is subjected to a second coat of sanding and spot repair, and then the product is cleaned and dried, and then sprayed with oil. After spraying, the product is left to stand for 1-3 hours and then baked. The baking temperature is 65-95 degrees and the baking time is 1-3 hours.

[0019] In one embodiment, after step S92, the method further includes:

[0020] Step S93: Third coat of paint: After drying, fill and polish any concave areas on the product surface, then clean and dry the product; apply topcoat, let it sit for 1-3 hours, and then bake at a temperature of 65-95 degrees for 1-3 hours;

[0021] Step S94: performing surface polishing on the product after the third coat of paint treatment to obtain a finished wheel hub.

[0022] In one embodiment, before step S20, the method further includes step S10: cleaning the surface of the aluminum alloy wheel hub, and then placing it in an oven to dry it, with a baking temperature of 80-120° C. and a baking time of 8-12 minutes.

[0023] In one embodiment, step S30 specifically includes: after the hub is baked, wait until the rim cools down to room temperature, lay a layer of raw silicone on the hub material laying position, then vacuumize, and place the mold in an autoclave for curing and molding; wherein the curing and molding conditions are a temperature of 120-150 degrees, a pressure of 0.65-0.95 MPa, and a time of 300-400 minutes.

[0024] In one embodiment, in step S60, the curing process is divided into two stages:

[0025] The first stage is heated from room temperature to a first temperature at a first heating rate under a first pressure, and when the temperature reaches the first temperature, the temperature and pressure are maintained for a first time;

[0026] The second stage is heated from the first temperature to the second temperature at a second heating rate under a second pressure, and when the temperature reaches the second temperature, the temperature is kept at the second temperature and pressure for a second time;

[0027] Among them, the first pressure is 0.16-0.3MPa, the second pressure is 0.5-0.8MPa, the first heating rate is 2.6℃ / min to 3.6℃ / min, the second heating rate is 2℃ / min to 3℃ / min, the first time is 8-15min, the second time is 180-210min, the first temperature is 75-95 degrees, and the second temperature is 120-150 degrees.

[0028] In one embodiment, in step S50, when laying the carbon fiber material at the corresponding position of the wheel hub, the butt joint line of each circle of material is at the position of the valve hole of the wheel hub, and the butt joint line is a straight line.

[0029] The beneficial effect of the method for manufacturing a carbon fiber coated aluminum alloy wheel hub provided by the present application is that: compared with the existing technology, the method for manufacturing a carbon fiber coated aluminum alloy wheel hub provided by the present application first makes a corresponding silicone sleeve mold through a mold, applies an adhesive layer at the position where the wheel hub needs to be paved, lays the carbon fiber at the corresponding position of the wheel hub, puts the silicone sleeve mold on the wheel hub paved with carbon fiber, and then solidifies and forms it. After opening the mold, the carbon fiber coated aluminum alloy wheel hub can be obtained. The manufacturing process is simple, the cost is low, and the product yield is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] Figure 1 It is a three-dimensional picture of the aluminum alloy wheel;

[0032] Figure 2 This is a cross-sectional view of a carbon fiber-covered wheel hub covered with a silicone mold;

[0033] Figure 3 for Figure 2 A magnified schematic diagram of point A in the middle;

[0034] Figure 4 for Figure 2 Exploded view of a carbon fiber-covered wheel hub covered with a silicone sleeve;

[0035] Figure 5 The process of manufacturing the carbon fiber coated aluminum alloy wheel hub provided in the embodiment of the present application Figure 1 ;

[0036] Figure 6 The process of manufacturing the carbon fiber coated aluminum alloy wheel hub provided in the embodiment of the present application Figure 2 ;

[0037] Figure 7 The process of manufacturing the carbon fiber coated aluminum alloy wheel hub provided in the embodiment of the present application Figure 3 .

[0038] Among them, the reference numerals in the figures are:

[0039] 10-aluminum alloy wheel hub; 20-carbon fiber layer; 30-silicone sleeve mold. DETAILED DESCRIPTION

[0040] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is 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 this application and are not intended to limit this application.

[0041] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0042] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0043] 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0044] See also Figure 1 The aluminum alloy wheel hub 10 includes a rim and a spoke. The spoke has a plurality of spokes. A mounting seat with axial openings at both ends is provided in the middle of the spoke for mounting an axle.

[0045] The method for manufacturing a carbon fiber coated aluminum alloy wheel hub provided in the embodiment of the present application is now described. Figures 1 to 7 The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub comprises the following steps:

[0046] In step S20, a layer of raw silicone is applied to the mold at the location where the wheel hub needs to be paved, and the mold is closed and vacuumed. Prior to step S20, step S10 is also included: cleaning the surface of the aluminum alloy wheel hub and then placing it in an oven to dry out any water stains. The baking temperature is 80-120°C and the baking time is 8-12 minutes. The wheel hub is hung during baking. The baking time can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, etc., and the baking time can be 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, etc.

[0047] In step S30, the mold is placed in an autoclave, heated and cured to form a silicone sleeve mold. The silicone sleeve mold is then removed. The silicone sleeve mold must be completely removed without any missing or cracked parts. Specifically, step S30 includes: after the wheel hub is baked and the rim cools to room temperature, a layer of raw silicone is applied to the wheel hub paving area. Vacuuming is then performed, and the mold is placed in an autoclave for curing. Curing conditions are a temperature of 120-150°C, a pressure of 0.65-0.95 MPa, and a time of 300-400 minutes. The curing temperature can be specifically 120 degrees, 125 degrees, 130 degrees, 135 degrees, 140 degrees, 145 degrees, 150 degrees, etc., the pressure can be specifically 0.65 MPa, 0.7 MPa, 0.75 MPa, 0.8 MPa, 0.85 MPa, 0.9 MPa, 0.95 MPa, etc., and the time can be specifically 300 min, 320 min, 340 min, 360 min, 380 min, 400 min, etc.

[0048] After step 30, the following steps are also included:

[0049] Step S31: roughening the positions of the aluminum alloy wheel hub that need to be covered with carbon fiber, and protecting the positions that do not need to be covered with carbon fiber, by using protective paper or protective tooling.

[0050] Step S32: Clean the roughened aluminum alloy wheel hub and place it in an oven to dry. The hub hub must be hung during baking; do not place it directly in the oven. The baking temperature is 54-80°C for 6-20 minutes. Specific baking temperatures include 54°C, 58°C, 60°C, 64°C, 68°C, 70°C, 72°C, 76°C, 78°C, and 80°C.

[0051] Step S40: Apply an adhesive layer to the area on the wheel hub where the fabric is to be laid, and let it sit for a predetermined time. The adhesive layer can be made of epoxy glue, and the predetermined time can be 8-13 minutes. Specifically, the time can be 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, etc.

[0052] Step S50: Spread the carbon fiber material on the corresponding position of the wheel hub. When spreading the carbon fiber material on the corresponding position of the wheel hub, the butt joint line of each circle of material must be at the position of the valve hole of the wheel hub, and the butt joint line is a straight line.

[0053] In step S60, the obtained silicone sleeve mold is placed on the carbon fiber-lined wheel hub, which is then placed in a vacuum bag, evacuated, and placed in an autoclave to form a covered part. In other words, the aluminum alloy wheel hub is covered with carbon fiber material, the outer periphery of which is covered with the silicone sleeve mold. The entire assembly is placed in a vacuum bag, evacuated, and then placed in an autoclave for hot pressing.

[0054] Specifically, in step S60, curing is divided into two stages: the first stage involves heating from room temperature to a first temperature at a first heating rate under a first pressure, and then maintaining the temperature and pressure for a first time at the first temperature; the second stage involves heating from the first temperature to a second temperature at a second heating rate under a second pressure, and then maintaining the temperature and pressure for a second time at the second temperature. The first pressure is lower than the second pressure, the first heating rate is higher than the second heating rate, and the second time is longer than the first time. The first pressure is 0.16-0.3 MPa, and the second pressure is 0.5-0.8 MPa; the first heating rate is 2.6°C / min to 3.6°C / min, and the second heating rate is 2°C / min to 3°C / min. The first time is 8-15 minutes, and the second time is 180-210 minutes. The first temperature is 75-95 degrees Celsius, and the second temperature is 120-150 degrees Celsius. The first pressure can be specifically 0.16MPa, 0.18MPa, 0.2MPa, 0.22MPa, 0.25MPa, 0.28MPa, 0.3MPa, etc., the second pressure can be specifically 0.5MPa, 0.55MPa, 0.58MPa, 0.6MPa, 0.62MPa, 0.65MPa, 0.7MPa, 0.75MPa, 0.8MPa, etc., the first heating rate can be specifically 2.6℃ / min, 2.7℃ / min, 2.8℃ / min, 2.9℃ / min, 3℃ / min, 3.1℃ / min, 3.2℃ / min, 3.3℃ / min, 3.4℃ / min, 3.5℃ / min, 3.6℃ / min, the second heating rate can be specifically 2℃ / min, 2.1℃ / min , 2.2℃ / min, 2.3℃ / min, 2.4℃ / min, 2.5℃ / min, 2.6℃ / min, 2.7℃ / min, 2.8℃ / min, 3℃ / min, etc., the first time can be 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, the second time can be 180min, 185min, 190min, 195min, 200min, 205min, 210min, etc., the first temperature can be 75 degrees, 78 degrees, 80 degrees, 82 degrees, 85 degrees, 88 degrees, 90 degrees, 92 degrees, 95 degrees, etc., the second temperature can be 120 degrees, 125 degrees, 130 degrees, 135 degrees, 140 degrees, 145 degrees, 150 degrees, etc.

[0055] Step S70: Take out the coating from the autoclave, remove the vacuum bag, and then remove the silicone mold to obtain a wheel hub coated with carbon fiber. Figures 2 to 4The silicone sleeve mold 30 is divided into two parts, the upper and lower parts, and the carbon fiber layer 20 outside the wheel hub is also divided into two parts. After the silicone sleeve mold is removed, the upper carbon fiber layer covers the upper surface and side surfaces of the spokes of the aluminum alloy wheel hub, and the lower surface of the spokes is not covered. The lower carbon fiber layer covers the inner peripheral wall of the rim of the aluminum alloy wheel hub, and only a small part extends to cover the outer peripheral wall of the rim. Most of the outer peripheral wall of the rim is not covered. The areas of the spokes and rim that are not carbon-coated can be covered with protective paper or protective tooling during roughening treatment, so that the positions that do not need carbon coating will not be sprayed with sand during sandblasting.

[0056] The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub provided in the present application is, compared with the prior art, first making a corresponding silicone sleeve mold through a mold, applying an adhesive layer at the position of the wheel hub where the cloth needs to be laid, laying the carbon fiber at the corresponding position of the wheel hub, and putting the silicone sleeve mold on the wheel hub covered with carbon fiber, and then curing and forming it. After opening the mold, the carbon fiber-coated aluminum alloy wheel hub can be obtained. The manufacturing process is simple, the cost is low, and the product yield is high.

[0057] After step S80, the method further includes step S91:

[0058] First coat of paint: After the roughening treatment is complete, the product undergoes a first coat of rough grinding to remove any white spots and smooth any uneven areas. Spot-finish any areas with large differences, especially those with particularly large differences, requires spot-finishing. After spot-finishing, the product is cleaned and sprayed with oil. After the spraying is completed, it is left to stand for a period of time before being baked. The standing time can be 1-3 hours, and the baking temperature can be between 65-95 degrees Celsius. Specific standing times can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. Specific baking temperatures can be 65, 68, 70, 72, 75, 78, 80, 82, 85, 88, 90, 92, or 95 degrees Celsius. Specific baking times can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0059] After step S91, the method further includes step S92:

[0060] Second coat of paint: Perform a second coat of sanding and spot repair on the product, then clean and dry it, then spray it with oil. After spraying, let it stand for a period of time and then bake it. The standing time can be 1-3 hours, the baking temperature can be 65-95 degrees, and the baking time can be 1-3 hours. The standing time can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc. The baking temperature can be 65 degrees, 68 degrees, 70 degrees, 72 degrees, 75 degrees, 78 degrees, 80 degrees, 82 degrees, 85 degrees, 88 degrees, 90 degrees, 92 degrees, 95 degrees, etc. The baking time can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.

[0061] After step S92, the following steps are also included:

[0062] Step S93: Third coat of paint: After drying, fill and polish any concave areas on the product surface, then clean and dry the product; apply topcoat, then let it rest for 1-3 hours and bake at a temperature of 65-95 degrees Celsius for 1-3 hours. The resting time can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, etc. The baking temperature can be 65 degrees, 68 degrees, 70 degrees, 72 degrees, 75 degrees, 78 degrees, 80 degrees, 82 degrees, 85 degrees, 88 degrees, 90 degrees, 92 degrees, or 95 degrees Celsius, etc. The baking time can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, etc.

[0063] Step S94: The surface of the product after the third coat of paint is polished to obtain the finished wheel hub. After the surface polishing is completed, the polished product can be sent for finished product inspection. After the product inspection is confirmed to be ok, it can be packaged and stored.

[0064] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for manufacturing a carbon fiber-coated aluminum alloy wheel hub, characterized by: The following steps are involved: Step S20, laying a layer of raw silicone rubber at the position where the wheel hub needs to be laid in the mold, and then closing the mold and vacuuming it; Step S30, placing the mold into an autoclave, heating and curing it to form a silicone sleeve mold, and then taking out the silicone sleeve mold; Step S40, applying an adhesive layer to the location on the wheel hub where the cloth needs to be laid, and leaving it for a predetermined time; Step S50, laying the carbon fiber material on the corresponding position of the wheel hub; Step S60, the obtained silicone sleeve mold is put on the wheel hub covered with carbon fiber, and then placed in a vacuum bag, evacuated, and placed in an autoclave for curing to form a covering part; Step S70: Take out the covering part from the autoclave, remove the vacuum bag, and then remove the silicone sleeve mold to obtain a wheel hub covered with carbon fiber.

2. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to claim 1, wherein: Before step S40, the method further includes: Step S31: performing a roughening process on the position of the aluminum alloy wheel hub corresponding to the position where the carbon fiber coating is required; Step S32: Clean the aluminum alloy wheel hub after the roughening treatment, put it into the oven and bake it dry at a temperature of 54-80 degrees and a baking time of 6-20 minutes.

3. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to claim 1, wherein: After step S70, the method further includes step S80: removing burrs and trimming the obtained wheel hub coated with carbon fiber, covering the portion not coated with carbon fiber with protective paper or protective tooling after trimming, and then performing a roughening treatment.

4. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to claim 3, characterized in that: After step S80, the process also includes step S91: first coat of paint treatment: after the roughening treatment is completed, the product is subjected to the first coarse grinding to remove the white spots on the product, smooth the uneven parts, and fill the uneven parts with large differences; After the repair is completed, clean it, spray it with oil, let it stand for 1-3 hours, and then bake it. The baking temperature is 65-95 degrees and the baking time is 1-3 hours.

5. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to claim 4, characterized in that: After step S91, step S92 is also included: second coat of paint treatment: the product is polished and patched for the second time, and then the product is cleaned and dried, and then sprayed with oil. After spraying, it is left to stand for 1-3 hours and then baked. The baking temperature is 65-95 degrees and the baking time is 1-3 hours.

6. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to claim 5, characterized in that: After step S92, the method further includes: Step S93: Third coat of paint: After drying, fill and polish any concave areas on the product surface, then clean and dry the product; apply topcoat, let it sit for 1-3 hours, and then bake at a temperature of 65-95 degrees for 1-3 hours; Step S94: performing surface polishing on the product after the third coat of paint treatment to obtain a finished wheel hub.

7. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to any one of claims 1 to 6, characterized in that: Before step S20, the method further includes step S10: cleaning the surface of the aluminum alloy wheel hub, and then placing the wheel hub in an oven for drying at a temperature of 80-120° C. for 8-12 minutes.

8. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to any one of claims 1 to 6, characterized in that: Step S30 specifically includes: after the hub is baked, wait for the rim to cool to room temperature, lay a layer of raw silicone on the hub material laying position, then vacuumize, and put the mold into the autoclave for curing and molding; wherein, the curing and molding conditions are temperature 120-150 degrees, pressure 0.65-0.95MPa, and time 300-400min.

9. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to any one of claims 1 to 6, characterized in that: In step S60, the curing process is divided into two stages: The first stage is heated from room temperature to a first temperature at a first heating rate under a first pressure, and when the temperature reaches the first temperature, the temperature and pressure are maintained for a first time; The second stage is heated from the first temperature to the second temperature at a second heating rate under a second pressure, and when the temperature reaches the second temperature, the temperature is kept at the second temperature and pressure for a second time; Among them, the first pressure is 0.16-0.3MPa, the second pressure is 0.5-0.8MPa, the first heating rate is 2.6℃ / min to 3.6℃ / min, the second heating rate is 2℃ / min to 3℃ / min, the first time is 8-15min, the second time is 180-210min, the first temperature is 75-95 degrees, and the second temperature is 120-150 degrees.

10. The method for manufacturing a carbon fiber-coated aluminum alloy wheel hub according to any one of claims 1 to 6, characterized in that: In step S50, when laying the carbon fiber material at the corresponding position of the wheel hub, the butt joint line of each circle of material is at the position of the valve hole of the wheel hub, and the butt joint line is a straight line.

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