A method for manufacturing a power vane forming die and the forming die

Abstract

The application discloses a kind of power vane forming die preparation methods, preparation wooden die;Preparation carbon fiber composite material suction surface shell mold: epoxy resin mold gelcoat is sprayed on the surface of wooden die of suction surface shell;According to the layer design of suction surface shell mold meat, carbon fiber fabric layer is sequentially placed on the surface of gelcoat layer;Vacuum bag film encapsulation is used to detect air tightness;According to the weight fraction of carbon fiber fabric, epoxy resin glue solution is prepared, and is injected into mold meat forming cavity;Solidification, cooling then remove and clean the forming auxiliary material on the surface of mold meat;2-5 layers of carbon fiber fabric are laid on the surface of mold meat, and pre-prepared carbon fiber composite material framework is placed, and filler is used to fill and smooth the hollow part of the framework, then 2-5 layers of carbon fiber fabric are used to cover, vacuum bag film encapsulation is used to detect air tightness, and finally epoxy resin is injected, and co-curing is shaped.The application also discloses a kind of forming die prepared by the preparation method.

Description

Technical Field

[0001] This invention relates to the field of molding die technology, and in particular to a method for preparing a power blade molding die and the molding die itself. Background Technology

[0002] Traditional power blade molds are mostly made of common metal materials, such as steel or aluminum alloy. Metal molds are generally of a split structure, resulting in weak joints that affect the overall strength and stability of the mold. Although metal molds have strong load-bearing capacity, their large weight limits operational flexibility, increases equipment load, affects production efficiency, and also increases transportation costs. Metal molds are prone to shrinkage during curing, leading to poor surface quality and affecting the precision of the power blade products. Furthermore, the thermal expansion coefficient of the mold material does not match that of the blade products, making them susceptible to deformation or even damage due to thermal stress. The slow heating rate and cooling characteristics of the mold do not match the temperature control characteristics of the blade products, resulting in prolonged growth cycles and unstable product quality.

[0003] In addition, the blade products require secondary positioning and assembly after demolding, which increases the risk of errors. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a power blade forming mold that simplifies the manufacturing process, improves the overall strength and stability of the mold, and achieves lightweight and high strength of the mold.

[0005] The present invention further provides a power blade forming mold prepared by the above-described preparation method.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing a power blade forming mold includes the following steps: S1. Prepare wood substitute molds; S2. Prepare a carbon fiber composite material mold, the carbon fiber composite material mold including a suction surface shell mold and a pressure surface shell mold, the preparation of the suction surface shell mold includes the following steps: S2.1 Spray a 1-2 mm thick epoxy resin mold coat onto the surface of the wood-based mold of the suction surface shell; S2.2 After the gel coat layer is cured, carbon fiber fabric is laid on the surface of the gel coat layer in sequence according to the layup design of the suction surface shell mold body until the thickness of the mold body reaches 10-30mm. S2.3 After the mold body is laid up, it is sealed with a flexible vacuum bag film and the airtightness is tested; S2.4 After passing the airtightness test, prepare epoxy resin solution at 60-80% of the weight fraction of carbon fiber fabric and inject it into the mold body forming cavity. S2.5 After the epoxy resin is injected and cured, it is cooled and then the molding auxiliary materials on the surface of the mold body are removed and cleaned. S2.6. After cleaning the mold body surface, lay 2-3 layers of carbon fiber fabric to cover it, then place the prefabricated carbon fiber composite skeleton, fill the hollow parts of the skeleton with filler material to make it flat, and then cover it with 2-3 layers of carbon fiber fabric. Finally, inject epoxy resin to impregnate the carbon fiber fabric, skeleton and filler material, so that the carbon fiber fabric, skeleton, filler material and mold body form a whole, and then co-cur and shape it. After curing, remove and clean the molding auxiliary materials on the surface.

[0007] As a further improvement to the above technical solution: The preparation of the suction surface shell mold also includes the following steps: S2.7 Demolding and trimming, then check the surface accuracy of the suction surface shell mold. If the surface accuracy does not meet the requirements, trim it. After the surface accuracy meets the requirements, check the airtightness of the suction surface shell mold.

[0008] The specific process of curing and shaping in step S2.6 is as follows: First, heat the material to 70-80°C at a heating rate of 1-2°C / minute and hold it at that temperature for 2-3 hours, while setting the pressure inside the autoclave to 0.3-0.5 MPa. Then, continue heating to 120-130°C at a heating rate of 1-2°C / minute, and hold at that temperature for 2-3 hours. At this time, the pressure inside the autoclave is adjusted to 0.6-0.8MPa. Finally, the autoclave is gradually cooled to room temperature at a cooling rate of 1~2℃ / min. Throughout the cooling process, the pressure inside the autoclave remains constant at 0.3~0.6MPa.

[0009] In step S2.5, curing is carried out in a constant temperature environment of 80℃~120℃ for 3~8 hours.

[0010] The specific process for airtightness testing in step S2.3 is as follows: the mold body is sealed with a flexible vacuum bag film, then vacuumed to below -0.095MPa, held for 5 minutes, and the vacuum degree drops by less than 10%. The specific process of airtightness testing in step S2.7 is as follows: the suction surface shell mold is sealed with a flexible vacuum bag film, the vacuum is drawn to below -0.095MPa, the pressure is maintained for 30 minutes, and the vacuum degree drops by less than 5%.

[0011] In step S2.1, the epoxy resin mold gel coat is sprayed in multiple layers, with each layer having the same thickness. The next layer is sprayed only after the previous layer of adhesive has cured.

[0012] The specific process for preparing the wood substitute mold in step S1 is as follows: S1.1. Evenly pile the wood substitute mud onto the surface of the metal frame; S1.2 After the wood substitute has solidified and formed, it is processed into a mold blank to ensure that the geometric tolerance meets the design requirements. Then, the mold blank is chamfered, the surface is polished, and a release agent is evenly applied. S1.3 Check the airtightness of the wood substitute mold: Seal the wood substitute mold in a sealed bag, evacuate to below -0.095MPa, hold the pressure for 30 minutes, and if the vacuum degree drops by less than 5%, the airtightness is qualified.

[0013] In step S1.1, select an expansion coefficient not exceeding 10 × 10 -6 / ℃ wood substitute mud was used as the filler material.

[0014] The metal frame mentioned in step S1.1 is a steel frame that has been welded and annealed.

[0015] A forming mold prepared by the above-mentioned method for preparing a power blade forming mold includes a suction surface shell mold and a pressure surface shell mold. The suction surface shell mold has a first locking part on its side and the pressure surface shell mold has a second locking part on its side. The first locking part can cooperate with the second locking part to lock the suction surface shell mold and the pressure surface shell mold.

[0016] Compared with the prior art, the advantages of the present invention are as follows: The present invention discloses a method for preparing a forming mold for power blades and the forming mold prepared therefrom: By using carbon fiber fabric lay-up, the mold surface and the back frame can be integrally molded, which simplifies the manufacturing process, improves the overall strength and stability of the mold, and reduces the problem of weak joints. By designing a reasonable curing and shaping process, the shrinkage rate can be effectively controlled, ensuring high quality and flatness of the mold surface, and improving the precision of power blade products. The molding mold is made of carbon fiber material, which achieves the purpose of lightweight and high strength. While ensuring sufficient load-bearing capacity, the weight of the mold is significantly reduced, which helps to improve production efficiency, reduce transportation costs, and thus improve the overall efficiency of use. The mold made of carbon fiber has a thermal expansion coefficient that is basically the same as that of the blade product, effectively avoiding product deformation or damage caused by thermal stress. In addition, the mold made of carbon fiber has a faster heating rate and cooling characteristics that match the blade product, which helps to shorten the production cycle and keep the mold and blade product synchronized throughout the heating-cooling process, further ensuring product quality.

[0017] The first and second locking parts are integrated into the mold, enabling the mold to function as a bonding tool. Specifically, the locking structure can accurately fix the blade products, reducing the errors that may occur during secondary positioning and assembly after demolding, and improving assembly accuracy and work efficiency.

[0018] Through the above design, the mold not only exhibits excellent temperature control performance during the production process, but also demonstrates higher practicality and reliability in the assembly stage.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of the suction surface shell mold in this invention. Figure 2 This is a three-dimensional structural diagram of the pressure surface shell mold in this invention.

[0021] Figure 3 This is a three-dimensional structural schematic diagram of the suction surface main beam mold in this invention.

[0022] Figure 4 This is a three-dimensional structural schematic diagram of the pressure surface main beam mold in this invention.

[0023] Figure 5 This is a three-dimensional structural diagram of the rib plate mold in this invention.

[0024] Figure 6 It is a three-dimensional structural diagram of the shell layered state of suction surface and pressure surface.

[0025] Figure 7 It is a three-dimensional structural diagram of the main beam ply configuration with suction and pressure surfaces.

[0026] Figure 8 This is a three-dimensional structural diagram of the combined solidified state of the suction surface main beam and the suction surface shell.

[0027] Figure 9 This is a three-dimensional structural diagram of the combined solidified state of the pressure surface main beam and the pressure surface shell.

[0028] Figure 10This is a three-dimensional structural diagram of the ribbed layer in its cured state.

[0029] Figure 11 This is a three-dimensional structural diagram of the suction surface mold and product components bonded to the rear edge rib.

[0030] Figure 12 This is a three-dimensional structural diagram of the bonding state between the pressure surface mold and product components and the leading edge rib.

[0031] Figure 13 This is a three-dimensional structural diagram of the adhesive bonding state between the suction surface component and the pressure surface component.

[0032] The labels in the diagram represent: 11. First locking part; 12. Suction surface mold profile; 13. Mold assembly positioning structure; 14. Main beam mold positioning structure; 15. Lifting structure; 21. Second locking part; 22. Pressure surface mold profile; 31. Rear edge rib; 32. Front edge rib; Detailed Implementation In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", 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.

[0033] 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.

[0034] In this invention, unless otherwise explicitly specified and limited, the terms "assembly," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figures 1 to 5 This invention illustrates an embodiment of a power blade forming mold prepared by the method for preparing a power blade forming mold according to the present invention. The large power blade forming mold mainly comprises five parts: a suction surface shell mold, a pressure surface shell mold, a suction surface main beam mold, a pressure surface main beam mold, and a rib mold. The suction surface shell mold has a first locking part 11 on its side, and the pressure surface shell mold has a second locking part 21 on its side. The first locking part 11 can cooperate with the second locking part 21 to lock the suction surface shell mold and the pressure surface shell mold together. The first locking part 11 and the second locking part 21 can be various types of locking hooks, locking rings, bolts, nuts, etc.

[0037] Furthermore, the suction surface shell mold and the pressure surface shell mold are also provided with a mold assembly positioning structure 13 (such as positioning holes and positioning protrusions around the mold) to achieve accurate positioning of the suction surface shell mold and the pressure surface shell mold.

[0038] The suction surface shell mold and the pressure surface shell mold are also equipped with a main beam mold positioning structure 14 (e.g., positioning grooves at both ends of the mold, which can cooperate with the protruding structures at both ends of the suction surface main beam mold and the pressure surface main beam mold for positioning), to achieve accurate positioning between the suction surface shell mold and the suction surface main beam mold, and between the pressure surface shell mold and the pressure surface main beam mold. The suction surface shell mold and the pressure surface shell mold are also equipped with a lifting structure 15 (e.g., various hooks, lifting rings, etc.) to facilitate the lifting and transportation of the mold.

[0039] The specific process of the method for preparing the power blade forming mold of the present invention is as follows: Wood substitute mold preparation: The purpose of wood substitute mold is to make molds for carbon fiber composite materials, including suction surface shell mold, pressure surface shell mold, suction surface main beam mold, pressure surface main beam mold, etc.

[0040] First, select a material with a low coefficient of thermal expansion (preferably not exceeding 10 × 10). -6 A wood substitute with a coefficient of thermal expansion (°C) was used as filler material and evenly piled onto the surface of the welded and annealed steel frame. The wood substitute with a low coefficient of thermal expansion helps to reduce the impact of temperature changes on the structure, while the annealing process of the steel frame further improves the stability and reliability of the substrate.

[0041] Then, after the wood substitute material is cured and shaped, it is processed into a mold blank by a high-precision CNC machine tool to ensure that the geometric tolerance reaches ±0.1mm.

[0042] Finally, the mold blank is chamfered and polished to achieve a surface roughness Ra≤0.8μm, and a release agent is applied evenly. To check the airtightness of the wood substitute mold, it is sealed in a sealed bag, then the bag is evacuated to below -0.095MPa and held under pressure for 30 minutes. If the vacuum level drops by less than 5%, the airtightness meets the requirements.

[0043] Fabrication of carbon fiber composite molds: Carbon fiber composite molding molds, including suction surface shell molds, pressure surface shell molds, suction surface main beam molds, and pressure surface main beam molds, were fabricated on a wooden mold using a vacuum injection molding process. The fabrication process of the suction surface shell mold is illustrated using this example; the other molds are fabricated similarly and will not be described in detail here.

[0044] The preparation steps include: 1) Spray a 1-2mm thick epoxy resin mold gel coat onto the surface of the suction surface shell wood mold. Preferably, spray in 4 layers, each layer is 0.5mm thick. After the first layer of adhesive has cured, spray the second layer, and so on. This helps to ensure that the gel coat is sprayed evenly. 2) After the gel coat layer has cured, according to the layering design of the suction surface shell mold body, layers are laid on the gel coat surface in sequence, with a mold body thickness of 10~30 mm; 3) After the mold body is laid up, it is sealed with a flexible vacuum bag film and vacuumed. Check the air tightness. Vacuum to below -0.095MPa and hold for 5 minutes. If the vacuum degree drops by less than 10%, the air tightness meets the requirements. 4) After the airtightness is qualified, prepare epoxy resin solution according to 70% of the weight fraction of carbon fiber fabric, and inject it into the mold body forming cavity using vacuum negative pressure suction. This helps to ensure that the epoxy resin fully wets the carbon fiber reinforcement material in the mold body. 5) After the epoxy resin is injected, it is cured at a constant temperature of 80°C to 120°C. After curing, it is cooled, and the molding auxiliary materials such as release cloth, guide net, injection can, etc. are removed and cleaned from the surface of the mold body. 6) Lay 2-3 layers of carbon fiber fabric on the cleaned mold body surface, place the prefabricated carbon fiber composite skeleton on it, fill the hollow parts of the skeleton with foam (preferably polyurethane foam, which has the characteristics of being lightweight, having strong adhesion, being self-leveling, and meeting certain strength and high temperature resistance requirements) and smooth it out, then cover it with another 2-3 layers of carbon fiber fabric, and finally use vacuum negative pressure suction to inject epoxy resin to impregnate the carbon fiber fabric, skeleton, foam, etc., so that it forms an integral part with the mold body, cures and sets the shape, and removes the molding auxiliary materials, such as release cloth, guide net, injection can, etc. 7) Demolding and trimming, checking the surface accuracy of the suction surface shell mold. If the surface accuracy does not meet the requirements, it needs to be trimmed. After the trimming is qualified, check the airtightness of the suction surface shell mold. Use a flexible film bag to seal it, then evacuate to below -0.095MPa and hold the pressure for 30 minutes. If the vacuum degree drops by less than 5%, the airtightness meets the requirements. Finally, the suction surface shell mold is obtained.

[0045] The inventors of this application have discovered that by rationally designing and strictly controlling the curing and shaping process parameters (including temperature, pressure, and time), the shrinkage rate of the mold caused by material properties during processing can be significantly reduced, thereby improving the dimensional accuracy and surface quality of the molding mold. Therefore, the specific curing and shaping process flow in this embodiment is as follows: First, the temperature is raised to 80°C at a heating rate of 1°C / minute and held at this temperature for 2 hours, while the pressure inside the autoclave is set to 0.3 MPa. Then, the temperature is increased to 125°C at a rate of 1°C / minute, and held for 2 hours. At this time, the pressure inside the autoclave is adjusted to 0.6MPa. Finally, the material was gradually cooled to room temperature at a cooling rate of 1°C / min, with the pressure inside the autoclave maintained at a constant 0.6 MPa throughout the cooling process. Verification has shown that this optimized curing process ensures high precision and flatness of the mold surface.

[0046] The molding die in this embodiment innovatively uses high-strength carbon fiber composite material and, through an integrated structural design, significantly reduces the die's weight while ensuring sufficient load-bearing capacity, thereby improving overall efficiency. The carbon fiber die has a coefficient of thermal expansion that is essentially the same as that of the blade product. This design effectively avoids product deformation or damage caused by thermal stress. Furthermore, the carbon fiber die has a rapid heating rate and cooling characteristics that match the blade product. Specifically, the molding die heats up at a rate of 1°C / minute and cools down at a rate of 2°C / minute during the molding process of the power blade, matching the temperature control characteristics of the blade product. This design not only helps shorten the production cycle but also ensures that the molding die and the blade product remain synchronized throughout the heating-cooling process, further guaranteeing product quality.

[0047] Integrating the locking structure into the mold gives it the function of bonding tooling. Specifically, the locking structure can precisely fix the blade products, reducing potential errors during secondary positioning and assembly after demolding, and improving assembly accuracy and work efficiency. Through this design, the mold not only exhibits excellent temperature control performance during production, but also demonstrates greater practicality and reliability in the assembly stage.

[0048] Figures 6 to 13This invention illustrates an embodiment of preparing large power blades using the power blade forming mold of the present invention. The forming of large power blades using carbon fiber composite materials mainly involves the following stages: (1) Suction surface and pressure surface shell layup, wherein layup refers to laying carbon fiber fabric in a predetermined direction and number of layers on the mold surface to achieve integral molding, as shown in 6. (2) The main beam ply for suction and pressure surfaces is shown in Figure 7. (3) The suction surface main beam and the suction surface shell are combined and solidified, as shown in Figure 8; (4) The pressure surface main beam and the pressure surface shell are combined and cured, as shown in 9; (5) Rib layer curing, as shown in 10; (6) The suction surface mold and product components are bonded to the rear edge rib, as shown in 11; (7) The pressure surface mold and product components are bonded to the front edge rib, as detailed below. Figure 12 As shown; (8) The suction surface assembly and the pressure surface assembly are bonded together, as follows: Figure 13 As shown.

[0049] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for preparing a forming mold for power blades, characterized in that: Includes the following steps: S1. Prepare wood substitute molds; S2. Prepare a carbon fiber composite material mold, the carbon fiber composite material mold including a suction surface shell mold and a pressure surface shell mold, the preparation of the suction surface shell mold includes the following steps: S2.1 Spray a 1-2mm thick epoxy resin mold coat onto the surface of the wood-based mold of the suction surface shell; S2.2 After the gel coat layer is cured, carbon fiber fabric is laid on the surface of the gel coat layer in sequence according to the layup design of the suction surface shell mold body until the thickness of the mold body reaches 10~30mm. S2.3 After the mold body is laid up, it is sealed with a flexible vacuum bag film and the airtightness is tested; S2.4 After passing the airtightness test, prepare epoxy resin solution at 60-80% of the weight fraction of carbon fiber fabric and inject it into the mold body forming cavity. S2.5 After the epoxy resin is injected and cured, it is cooled and then the molding auxiliary materials on the surface of the mold body are removed and cleaned. S2.

6. After cleaning the mold body surface, lay 2-3 layers of carbon fiber fabric to cover it, then place the prefabricated carbon fiber composite skeleton, fill the hollow parts of the skeleton with filler material to make it flat, and then cover it with 2-3 layers of carbon fiber fabric. Finally, inject epoxy resin to impregnate the carbon fiber fabric, skeleton and filler material, so that the carbon fiber fabric, skeleton, filler material and mold body form a whole, and then co-cur and shape it. After curing, remove and clean the molding auxiliary materials on the surface.

2. The method for preparing a power blade forming mold according to claim 1, characterized in that: The preparation of the suction surface shell mold also includes the following steps: S2.7 Demolding and trimming, then check the surface accuracy of the suction surface shell mold. If the surface accuracy does not meet the requirements, trim it. After the surface accuracy meets the requirements, check the airtightness of the suction surface shell mold.

3. The method for preparing a power blade forming mold according to claim 1, characterized in that: The specific process of curing and shaping in step S2.6 is as follows: First, heat the material to 70-80°C at a heating rate of 1-2°C / minute and hold it at that temperature for 2-3 hours, while setting the pressure inside the autoclave to 0.3-0.5 MPa. Then, continue heating to 120-130°C at a heating rate of 1-2°C / minute, and hold at that temperature for 2-3 hours. At this time, the pressure inside the autoclave is adjusted to 0.6-0.8 MPa. Finally, the autoclave is gradually cooled to room temperature at a cooling rate of 1~2℃ / min. Throughout the cooling process, the pressure inside the autoclave remains constant at 0.3~0.6MPa.

4. The method for preparing a power blade forming mold according to claim 1, characterized in that: In step S2.5, curing is carried out in a constant temperature environment of 80℃~120℃ for 3~8 hours.

5. The method for preparing a power blade forming mold according to claim 2, characterized in that: The specific process for airtightness testing in step S2.3 is as follows: the mold body is sealed with a flexible vacuum bag film, then vacuumed to below -0.095MPa, and held at that pressure for 5 minutes. The vacuum level decreases by less than 10%. The specific process of airtightness testing in step S2.7 is as follows: the suction surface shell mold is sealed with a flexible vacuum bag film, the vacuum is drawn to below -0.095MPa, the pressure is maintained for 30 minutes, and the vacuum degree drops by less than 5%.

6. The method for preparing a power blade forming mold according to claim 1, characterized in that: In step S2.1, the epoxy resin mold gel coat is sprayed in multiple layers, with each layer having the same thickness. The next layer is sprayed only after the previous layer of adhesive has cured.

7. The method for preparing a power blade forming mold according to any one of claims 1 to 6, characterized in that: The specific process for preparing the wood substitute mold in step S1 is as follows: S1.

1. Evenly pile the wood substitute mud onto the surface of the metal frame; S1.2 After the wood substitute has solidified and formed, it is processed into a mold blank to ensure that the geometric tolerance meets the design requirements. Then, the mold blank is chamfered, the surface is polished, and a release agent is evenly applied. S1.3 Check the airtightness of the wood substitute mold: Seal the wood substitute mold in a sealed bag, evacuate to below -0.095MPa, hold the pressure for 30 minutes, and if the vacuum degree drops by less than 5%, the airtightness is qualified.

8. The method for preparing a power blade forming mold according to claim 7, characterized in that: In step S1.1, select an expansion coefficient not exceeding 10 × 10 -6 / ℃ wood substitute mud was used as the filler material.

9. The method for preparing a power blade forming mold according to claim 7, characterized in that: The metal frame mentioned in step S1.1 is a steel frame that has been welded and annealed.

10. A forming mold prepared by the method for preparing a power blade forming mold according to any one of claims 1 to 9, characterized in that: The molding die includes a suction surface shell die and a pressure surface shell die. The suction surface shell die has a first locking part (11) on its side and the pressure surface shell die has a second locking part (21) on its side. The first locking part (11) can cooperate with the second locking part (21) to lock the suction surface shell die and the pressure surface shell.

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