Manufacturing process of light-weight wind power variable pitch bearing plastic retainer
By using high-quality POM materials, drying treatment, pressure holding treatment and vibration technology, the problem of pores in plastic materials during injection molding is solved, and the material strength and service life of wind power pitch bearings are significantly improved.
Patent Information
- Application Number
- CN202510187748.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-05-13
AI Technical Summary
During injection molding, plastic materials are prone to pore problems, resulting in a decrease in material strength and toughness, increasing the risk of lubricant leakage and pollutant penetration, and thus shortening the service life of wind power pitch bearings.
High-quality POM materials with uniform particles and consistent color are used to reduce the moisture content of the material through drying treatment, set appropriate pressure and time to ensure that the material fully fills the mold cavity, and use impact parts to vibrate during the injection molding process to improve the material flowability.
It significantly reduces the porosity in the plastic cage, improves the strength and toughness of the material, extends the service life of wind power pitch bearings, and reduces operation and maintenance costs.
Smart Images
Figure CN119974364A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the field of wind turbine pitch bearings, and in particular, relates to a manufacturing process for a lightweight wind turbine pitch bearing plastic cage. Background Art
[0002] With the improvement of wind energy conversion capacity and the consideration of operation and maintenance costs, the variable pitch bearing, as the core rotating component between the blade and the hub, faces complex and changeable external load challenges, and needs to have both excellent dynamic response and long service life. With the evolution of mechanical transmission systems towards high speed, low friction and lightweight, coupled with the rapid development of high-performance engineering plastics, the material selection of bearing cages is no longer limited to traditional metals. Nowadays, high-performance engineering plastics are the new favorite of cages. Injection molded plastic cages have achieved a good balance between strength and elasticity, and have many advantages due to their unique materials. For example, the low density of plastics significantly reduces the inertial force of the cage, giving it excellent dynamic response capabilities. More importantly, under poor lubrication conditions, plastic cages can still maintain normal operation for a period of time, avoiding bearing jamming and possible secondary damage. It has been widely used at home and abroad and has shown unique advantages.
[0003] However, the porosity problem that plastic materials are prone to during the injection molding process is a key factor that restricts their mechanical properties and service life. The formation of pores inside plastic cages is mainly attributed to the physical phenomenon of material cooling and shrinkage during the molding stage. Since cages need to meet specific load and functional requirements, their pocket window beams are usually designed with thicker walls. During the cooling and solidification process, the thinner wall areas will be cooled and crystallized first, while the thicker wall areas will lack sufficient flow material to fill the space formed by cooling and shrinkage during subsequent crystallization, which ultimately leads to the formation of pores.
[0004] These pores not only weaken the overall strength and toughness of the material, but also may become potential channels for lubricant leakage and contaminant penetration. The presence of pores not only reduces the mechanical properties of the material, but may also accelerate the wear process of the bearing and shorten its service life, because the pores provide a path for lubricant loss and contaminants to enter the interior of the bearing, thereby exacerbating friction and corrosion between bearing components. Therefore, controlling the cooling shrinkage during the injection molding process to reduce the formation of pores is crucial to improving the performance of plastic cages. It can be seen that the existing technology needs to be further improved and enhanced. Summary of the invention
[0005] The present invention provides a manufacturing process for a lightweight wind turbine pitch bearing plastic retainer, so as to at least solve or alleviate one or more technical problems in the prior art, or at least provide a beneficial option.
[0006] To achieve the above object, the present invention provides the following technical solutions:
[0007] A lightweight wind turbine pitch bearing plastic cage manufacturing process, comprising the following steps:
[0008] Step 1: Select high-quality POM material with uniform particles and consistent color as the injection molding raw material;
[0009] Step 2: The drying machine dries the POM material to reduce the moisture content of the POM material to 0.2% or less;
[0010] Step 3: Add the pretreated POM material to the injection molding machine feeding system, set the holding pressure and holding time, determine the theoretical injection amount according to the mold cavity volume and material density parameters, and set the actual injection amount to be 3g-5g higher than the theoretical injection amount;
[0011] Step 4: Set the temperature of the mold between 50℃-80℃;
[0012] Step 5: The temperature of the injection nozzle is set to 210°C, and the POM material is injected into the mold cavity through the glue port;
[0013] Step 6: After the injection molding is completed, wait for the injection molding cage to be fully cooled and then remove the injection molding cage from the mold.
[0014] The above structure uses high-quality POM (polyoxymethylene) material with uniform particles and consistent color as the injection molding raw material, which can ensure the quality and consistency of the material itself and reduce the porosity caused by material problems. Using a drying machine to dry the POM material to reduce the moisture content to 0.2% or below helps to reduce the moisture in the material and avoid porosity caused by water evaporation during the injection molding process. By accurately setting the holding pressure, holding time, and the actual injection amount being 3g-5g higher than the theoretical injection amount, it can ensure that the material is fully filled in the mold cavity and reduce porosity caused by insufficient injection or uneven pressure.
[0015] In a preferred implementation, the glue port in step 5 is located at a thick wall position of the retaining frame.
[0016] Ensure that the plastic melt fills these critical areas first during the injection molding process. Since thick-walled areas usually require more material to fill, setting the gate here can ensure that these areas are adequately supplied with material, thereby reducing porosity caused by insufficient filling.
[0017] In a preferred implementation, the holding pressure p of step 3 satisfies 115 MPa≤p≤150 MPa, and the holding time t satisfies 18 s≤t≤28 s.
[0018] In a preferred implementation, the mold in step 4 is provided with a sealing cavity at the position of the retaining frame pocket, and the side of the sealing cavity is a molding space corresponding to the thick-walled window beam. An impact piece is introduced into the sealing cavity to impact the cavity wall to vibrate the injection molding material, improve the fluidity of the injection molding material, and make the injection molding material evenly distributed.
[0019] When the POM material is injected into the mold cavity, the impact piece hits the inner wall of the sealed cavity driven by air pressure, and the generated vibration wave can be transmitted to the injection molding material, effectively improving its fluidity. The improvement of fluidity helps the injection molding material to fill every corner of the mold cavity more easily, especially the complex structure and thick wall parts, thereby reducing the porosity caused by poor flow. The vibration action can break the agglomeration structure inside the injection molding material and make it more evenly distributed in the mold cavity. The uniform distribution helps to reduce the porosity and defects caused by material accumulation or sparseness, and improve the overall quality and performance of the cage.
[0020] In a preferred implementation, the impact piece is spherical and a plurality of impact pieces are provided in the sealing cavity, and impact the inner wall of the sealing cavity under the driving of air pressure.
[0021] In a preferred implementation, the temperature of the gas injected into the sealed cavity is regulated to achieve local temperature control of the mold.
[0022] In a preferred implementation, the baking temperature in step 2 is 75±5 degrees.
[0023] In a preferred implementation, the retaining frame formed in step 6 is a segmented window-type isolation block structure, each segment of the isolation block is configured with three pockets to accommodate rolling elements, and the intervals between the pockets are window beams.
[0024] In a preferred implementation, the inner wall of the retainer pocket has an arc surface and an inclined surface structure to facilitate the operation of the rolling body, and an oil storage groove is provided in the window beam section. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present application and do not constitute an improper limitation of the present invention. In the drawings:
[0026] Figure 1 The production process flow chart of the lightweight wind turbine pitch bearing plastic cage of the present application is depicted;
[0027] Figure 2 A three-dimensional schematic diagram of the injection molding of a lightweight wind turbine pitch bearing plastic cage of the present application is depicted;
[0028] Figure 3 A schematic diagram of the internal structure of a mold for producing a lightweight wind turbine pitch bearing plastic cage of the present application is depicted;
[0029] Figure 4 A schematic diagram of the plastic retainer of the present application is depicted;
[0030] Figure 5 A schematic diagram of a large gap scanning diagram of the product before the improvement of this application is depicted;
[0031] Figure 6 A schematic diagram of a large gap scanning diagram of the product of Test 2 of this application is depicted;
[0032] Description of labels:
[0033] 1. mold; 10. mold cavity; 11. sealing cavity; 110. impact member; 2. retaining frame; 20. pocket hole; 21. window beam; 210. oil storage tank. DETAILED DESCRIPTION
[0034] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.
[0035] First, the technical concept of the technical solution disclosed in the present invention is explained.
[0036] In view of the above problems existing in the prior art, the present invention provides a kind of invention.
[0037] The specific plans adopted are:
[0038] like Figure 1-4 As shown, the present invention provides a lightweight wind turbine pitch bearing plastic cage manufacturing process, comprising the following steps:
[0039] Step 1: Select high-quality POM material with uniform particles and consistent color as the injection molding raw material;
[0040] Step 2: The drying machine dries the POM material to reduce the moisture content of the POM material to 0.2% or less;
[0041] Step 3: Add the pretreated POM material to the injection molding machine feeding system, set the holding pressure and holding time, determine the theoretical injection amount according to the mold cavity volume and material density parameters, and set the actual injection amount to be 3g-5g higher than the theoretical injection amount;
[0042] Step 4: Set the temperature of mold 1 between 50°C and 80°C;
[0043] Step 5: The temperature of the injection nozzle is set to 210° C., and the POM material is injected into the mold cavity 10 through the glue port;
[0044] Step 6: After the injection molding is completed, wait for the injection molding cage to be fully cooled and then remove the injection molding cage from the mold.
[0045] The above scheme uses high-quality POM (polyoxymethylene) materials with uniform particles and consistent color as injection molding raw materials, which can ensure the quality and consistency of the material itself and reduce porosity caused by material problems. Using a drying machine to dry the POM material to reduce the moisture content to 0.2% or below helps to reduce the moisture in the material and avoid porosity caused by water evaporation during the injection molding process. By accurately setting the holding pressure, holding time, and the actual injection amount to be 3g-5g higher than the theoretical injection amount, it can ensure that the material is fully filled in the mold cavity and reduce porosity caused by insufficient injection or uneven pressure. Set the mold temperature between 50℃-80℃ and the injection nozzle temperature to 210℃. The setting of these two temperature ranges helps the melting and flow of the POM material, while avoiding material degradation caused by excessively high temperature or insufficient filling caused by too low temperature, thereby reducing porosity.
[0046] Reducing the porosity can significantly improve the strength and toughness of the cage, improve its mechanical properties, and thus increase the reliability and service life of the entire variable pitch bearing. The POM material itself has low density characteristics, and with the optimized injection molding process, it can further achieve lightweight cages, helping to reduce the weight and operation and maintenance costs of the entire wind turbine.
[0047] The experiment designs different combinations of holding pressure, holding time and mold temperature, manufactures multiple injection molding samples with different holding pressure, holding time and mold temperature, and establishes the mapping relationship between the injection amount and the holding pressure, holding time and mold temperature through weight testing. The main parameters are shown in Table 1.
[0048]
[0049] Table 1 Test parameters
[0050] The weight test results of the samples obtained through the test were analyzed. It can be seen from Table 2 that the glue feeding amount of Test 2, 787g, is the maximum value, which is 5g higher than the 782g before improvement. Next, CT scans are performed on the samples before improvement and the samples in Test 2.
[0051]
[0052] Table 2 Glue feeding amount measurement data (weight method)
[0053] The CT scan results show that:
[0054] See also Figure 5, before improvement, the defect volume of the first cavity was 47.77, the defect volume ratio was 0.018%, and there were two large pores. The defect volume of the second cavity before improvement was 44.84, the defect volume ratio was 0.017%, and there were two large pores.
[0055] See also Figure 6 The defect volume of the first cavity in test 2 is 33.62, the defect volume ratio is 0.012%, and there is a large pore. The defect volume of the second cavity in test 2 is 15.75, the defect volume ratio is 0.006%, and there is no large pore.
[0056] According to the data comparison before and after process optimization:
[0057] The defect volume of Test 2 was significantly optimized, with the defect volume of the second cavity reduced by 64.84% year-on-year. The results are shown in Table 3.
[0058]
[0059] Table 3 Data comparison before and after process optimization
[0060] The large voids in Test 2 were significantly optimized. The four pores before the improvement were only one in Test 2. Figure 6 As shown, the optimization effect is improved by 75%.
[0061] The appropriate amount of injection can ensure that the injection material fully fills the mold cavity, avoiding problems such as short shots and lack of material. At the same time, too high an amount of injection may lead to problems such as overfilling, increased internal stress, and extended cooling time. Through the above POM material test, it is known that under the conditions of holding pressure of 150Mpa, holding time of 18S, and mold temperature of 55℃, the injection amount is set to 787g, and the pores of the cage can be optimized, and the optimization effect is improved by 75%. The increase in the amount of injection can make the thinner wall of the cage complete the cooling and crystallization process first during the cooling stage, while the thicker area continues to crystallize, and there is subsequent material to fill the vacancies caused by cooling shrinkage, thereby reducing the formation of pores.
[0062] As a preferred embodiment of the present application, the glue port in step 5 is located at a thick wall position of the retaining frame.
[0063] Placing the nozzle at the thick wall ensures that the plastic melt fills these critical areas first during the injection molding process. Since thick wall areas usually require more material to fill, placing the nozzle here ensures that these areas are fully supplied with material, thereby reducing porosity caused by insufficient filling. During the injection molding holding pressure stage, the flowing plastic can be fully held in the thick wall area. This helps to eliminate voids caused by material shrinkage and further reduce the formation of porosity. The holding pressure process ensures that the material is evenly distributed and tightly compacted in the mold cavity, thereby improving the density and strength of the cage.
[0064] As a preferred embodiment of the present application, the holding pressure p of step 3 satisfies, 115Mpa≤p≤150Mpa, and the holding time t satisfies, 18s≤t≤28s.
[0065] The holding pressure is between 115MPa and 150MPa, which can ensure that the plastic melt is fully filled in the mold cavity, especially in thick-walled and complex structural parts. Sufficient pressure helps the plastic melt flow and fill every corner of the mold, reducing the formation of pores and defects. Appropriate holding pressure can improve the density of the cage and reduce internal pores, thereby enhancing the strength and toughness of the cage. This is crucial for wind turbine pitch bearings that withstand complex and variable external loads. The holding time is between 18s and 28s, allowing the plastic melt to have enough time to solidify and cool in the mold cavity. This helps to reduce deformation and shrinkage problems caused by insufficient solidification. Appropriate holding time can ensure that the cage maintains a stable shape and size during the cooling process, reducing dimensional deviation and shape distortion caused by uneven cooling.
[0066] If the holding pressure is lower than 115MPa, the plastic melt will not be filled sufficiently, resulting in pores and defects. In addition, too low a pressure may also lead to uneven material distribution and reduce the strength and toughness of the cage. If the holding pressure exceeds 150MPa, it will cause excessive wear of the mold and increase production costs. At the same time, too high a pressure may also cause excessive internal stress in the plastic melt, causing cracks or deformation of the cage during subsequent use. If the holding time is less than 18s, the plastic melt will not solidify sufficiently, causing the cage to deform or shrink during the cooling process. In addition, too short a holding time may also affect the distribution and density of the material. If the holding time exceeds 28s, although it can ensure that the plastic melt is fully solidified and cooled, it will increase production costs and cycles.
[0067] As a preferred embodiment of the present application, the mold in step 4 is provided with a sealing cavity corresponding to the retaining frame pocket position, the side of the sealing cavity is a molding space corresponding to the thick-walled window beam, and an impact piece is introduced into the sealing cavity to impact the cavity wall to vibrate the injection molding material, improve the fluidity of the injection molding material, and make the injection molding material evenly distributed. For details, see Figure 3 The impact piece is spherical and multiple impact pieces are arranged in the sealing cavity, and impact the inner wall of the sealing cavity under the driving of air pressure.
[0068] When the POM material is injected into the mold cavity, the impact piece 110 impacts the inner wall of the sealing cavity 11 driven by air pressure, and the generated vibration wave can be transmitted to the injection molding material, effectively improving its fluidity. The improvement in fluidity helps the injection molding material to fill every corner of the mold cavity more easily, especially the complex structure and thick-walled parts, thereby reducing the porosity caused by poor flow. The vibration effect can break the agglomeration structure inside the injection molding material and make it more evenly distributed in the mold cavity. The uniform distribution helps to reduce the porosity and defects caused by material accumulation or sparseness, and improve the overall quality and performance of the cage. By improving fluidity and promoting uniform distribution, this solution can significantly reduce the porosity in the injection molded cage.
[0069] And because the vibration effect can improve the filling effect of the injection material, reduce the scrap rate caused by insufficient filling, thereby improving production efficiency. At the same time, the uniform distribution of injection material also helps to shorten the injection cycle and further reduce production costs.
[0070] In order to maintain the air pressure in the sealed cavity and drive the impact piece to impact, the sealed cavity must be designed with reasonable air inlets and outlets.
[0071] Furthermore, the temperature of the gas injected into the sealed cavity is regulated to achieve local temperature control of the mold.
[0072] During the injection molding process, the difference in cooling speed between thin-walled and thick-walled areas can lead to porosity. Thin-walled areas cool faster and tend to form a hard shell, while the interior may not be fully solidified, resulting in increased internal stress and even shrinkage. Thick-walled areas cool more slowly, which may cause the material to shrink more during the solidification process and may also form porosity. Therefore, local temperature control can be designed to balance this difference and regulate the temperature of the gas entering the sealed cavity.
[0073] For example, for thick-walled areas, a slightly lower temperature gas can be introduced and the gas direction can be controlled so that it blows toward the thick wall to speed up its cooling rate and coordinate it with the cooling rate of the thin-walled area. Or because the thin-walled area cools faster, the temperature around it can be kept relatively stable, or it can be prevented from cooling quickly by slight heating.
[0074] As a preferred embodiment of the present application, the baking temperature in step 2 is 75±5 degrees.
[0075] Moisture and volatiles can be effectively removed within this temperature range while avoiding overheating and decomposition of the material.
[0076] As a preferred embodiment of the present application, the retaining frame 2 formed in step 6 is a segmented window-type isolation block structure, each isolation block is equipped with three pockets 20 to accommodate rolling bodies, and the intervals between the pockets are window beams 21. The inner walls of the retaining frame pockets have arc and inclined structures to facilitate the operation of the rolling bodies, and an oil storage tank 210 is provided in the window beam section.
[0077] Anything not described in the present invention can be achieved by adopting or drawing on existing technologies.
[0078] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of various changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.
Claims
1. A lightweight wind turbine pitch bearing plastic cage manufacturing process, comprising the following steps: Step 1: Select high-quality POM material with uniform particles and consistent color as the injection molding raw material; Step 2: The drying machine dries the POM material to reduce the moisture content of the POM material to 0.2% or less; Step 3: Add the pretreated POM material to the injection molding machine feeding system, set the holding pressure and holding time, determine the theoretical injection amount according to the mold cavity volume and material density parameters, and set the actual injection amount to be 3g-5g higher than the theoretical injection amount; Step 4: Set the temperature of the mold between 50℃-80℃; Step 5: The temperature of the injection nozzle is set to 210°C, and the POM material is injected into the mold cavity through the glue port; Step 6: After the injection molding is completed, wait for the injection molding cage to be fully cooled and then remove the injection molding cage from the mold.
2. The lightweight wind turbine pitch bearing plastic cage manufacturing process according to claim 1 is characterized in that: The glue opening in step 5 is located at the thick wall position of the retainer.
3. The lightweight wind turbine pitch bearing plastic cage manufacturing process according to claim 1 is characterized in that: The holding pressure p of step 3 satisfies 115Mpa≤p≤150Mpa, and the holding time t satisfies 18s≤t≤28s.
4. The lightweight wind turbine pitch bearing plastic cage manufacturing process according to claim 1 is characterized in that: The mold in step 4 is provided with a sealing cavity at the position of the retaining frame pocket corresponding to the mold, and the side of the sealing cavity is a molding space corresponding to the thick-walled window beam. An impact piece is introduced into the sealing cavity to impact the cavity wall to vibrate the injection molding material, improve the fluidity of the injection molding material, and make the injection molding material evenly distributed.
5. The lightweight wind turbine pitch bearing plastic cage manufacturing process according to claim 4 is characterized in that: The impact piece is spherical and a plurality of impact pieces are arranged in the sealing cavity, and impact the inner wall of the sealing cavity under the driving of air pressure.
6. The lightweight wind turbine pitch bearing plastic cage manufacturing process according to claim 4 is characterized in that: The temperature of the gas injected into the sealed cavity is regulated to achieve local temperature control of the mold.
7. The lightweight wind turbine pitch bearing plastic cage manufacturing process according to claim 1 is characterized in that: The baking temperature in step 2 is 75±5 degrees.
8. The lightweight wind turbine pitch bearing plastic cage manufacturing process according to claim 1 is characterized in that: The retainer formed in step 6 is a segmented window-type isolation block structure, each segment of the isolation block is equipped with three pockets to accommodate rolling elements, and the intervals between the pockets are window beams.
9. The lightweight wind turbine pitch bearing plastic cage manufacturing process according to claim 8 is characterized in that: The inner wall of the cage pocket has an arc surface and an inclined surface structure, which is convenient for the operation of the rolling body, and an oil storage groove is arranged on the window beam section.