Oscillation hot-pressing integrated forming process for L-shaped groove insulation of generator rotor

Abstract

The invention relates to a generator rotor L-shaped groove insulation oscillation hot-pressing integrated forming process, which specifically comprises the following steps of S1, mold preparation and substrate layer laying, S2, primary oscillation hot-pressing forming, and S3, thickening layer laying and secondary oscillation curing, and specifically comprises the following steps of S1, mold preparation and substrate layer laying, S2, primary oscillation hot-pressing forming, and S3, thickening layer laying and secondary oscillation curing, the working face of the dynamic pressure applying device applies dynamic pressure to the materials in a mode of combining rolling compaction and wave-shaped scanning, and S4, post-treatment.The method has the following beneficial effects that by introducing a dynamic oscillation pressure field, the problems of interlayer fusion and internal stress in the two-time hot pressing process of different materials are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of advanced manufacturing technology of core components of new energy power generation equipment, and specifically relates to an oscillating hot pressing integrated molding process for L-shaped slot insulation of generator rotor, which is particularly suitable for the manufacturing of insulation structure of high power density generator rotor. Background Technology

[0002] Generator rotor slot insulation typically employs an L-shaped structure, with its long side attached to the slot wall and the short side (i.e., the spacer strip) bearing the main clamping force of the rotor windings. Therefore, the thickness of the short side is usually much greater than that of the long side. Traditional L-slot insulation manufacturing processes often involve separately molding the substrate and spacer strip, then bonding them together with adhesive. This method suffers from problems such as adhesive aging, uneven adhesive application leading to delamination or overflow, and interface thermal stress concentration, severely impacting the long-term reliability of the insulation system.

[0003] To overcome the shortcomings of adhesive bonding processes, existing technologies have proposed the idea of ​​integral hot pressing for L-shaped groove insulation. However, due to the significant difference in thickness between the long and short sides of the L-shaped structure, if a single hot pressing is performed using an L-shaped mold, the internal stress distribution will be extremely uneven due to the different curing shrinkage rates and heat transfer rates of the material in the thick and thin areas. The short side is particularly prone to severe warping deformation, resulting in a low product yield.

[0004] To address this, one proposed method involves first hot-pressing to form a U-shaped groove insulation, then cutting it to obtain two L-shaped groove insulations. While this method improves the warping problem of directly formed L-shaped parts to some extent, a new and more subtle technical defect is introduced when using a multi-stage hot-pressing process—that is, first hot-pressing to form a U-shaped substrate (composed of epoxy fiberglass prepreg and NOMEX paper), then laying a thickening layer (epoxy fiberglass prepreg) at the bottom for a second hot-pressing.

[0005] Risk of poor interlayer interface fusion: After the first hot pressing, the U-shaped substrate material is already in a partially cured or nearly fully cured state, and its surface chemical activity is significantly reduced. During the second hot pressing, it is difficult to achieve sufficient molecular-level diffusion and cross-linking between the newly laid thickened prepreg layer and the already formed U-shaped substrate interface. Even under vacuum and pressure, the two are prone to forming a distinct physical interface rather than a continuous chemically bonded whole. This weak interface is highly likely to become the origin of delamination under the thermal cycling and electromagnetic forces of the generator during operation.

[0006] Complex secondary thermal stress: After the first hot pressing, initial curing stress already exists inside the U-shaped substrate. The second hot pressing process is equivalent to localized secondary heating and curing of the bottom area of ​​the U-shaped substrate, which undergoes further thermal expansion and cooling contraction, while the sidewall areas are less affected by heat. This uneven thermal history leads to the formation of a complex and difficult-to-eliminate residual stress system inside the final product, which may not only cause microcracks but also reduce the dimensional stability and fatigue life of the product under long-term dynamic loads.

[0007] NOMEX paper performance may be compromised: As a high-performance insulating material, the excellent dielectric properties of NOMEX paper partly depend on its porous fiber structure. Under the high temperature and pressure of the second hot pressing, the NOMEX paper in the bottom region faces the risk of being over-compressed, causing a sharp drop in porosity. At the same time, it may be over-wetted by the secondary molten epoxy resin, resulting in damage to its inherent flexibility and dielectric strength. Summary of the Invention

[0008] The purpose of this invention is to overcome the above-mentioned shortcomings and provide an oscillating hot pressing integral molding process for L-shaped slot insulation of generator rotor. By introducing a dynamic oscillating pressure field, the problem of interlayer fusion and internal stress in the two hot pressing processes of different materials is effectively solved.

[0009] The objective of this invention is achieved through the following technical solution: an oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor, characterized by comprising the following steps:

[0010] S1. Mold Preparation and Base Layer Laying: Position a U-shaped hot pressing mold, which includes an oscillating hot pressing head assembly composed of multiple independent pressing head units arranged side by side along the axial direction, a fixed U-shaped mold core, and a vacuum sealing system; on the platform of the U-shaped mold core, stack 20-30 layers of epoxy glass fiber prepreg and 2-5 layers of NOMEX paper in sequence to form a composite base layer; S2. Initial Oscillating Hot Pressing: The oscillating hot pressing head assembly is pressed down to contact the composite base layer, and the pressure is continued to bend the composite base layer to the U-shape. Inside the mold core cavity, under a base pressure of 120-140℃ and 0.5-1.0MPa for 10-15 minutes, the axial oscillation program is started and continued for 10-30 minutes to ensure that the composite base layer is uniformly heated under dynamic pressure and initially shaped into a U-shaped preform; S3, Thickening layer laying and secondary oscillation curing: Keeping the U-shaped preform in the mold, 40-50 layers of epoxy glass fiber prepreg II are laid on its inner bottom to form a padding thickening layer; the mold is closed, the vacuum system is started, and the gradient pressure curing program is executed;

[0011] Among them, when the oscillating hot press head performs pressing, its working surface applies dynamic pressure to the material by combining rolling and wavy scanning; S4, post-processing: the U-shaped groove insulation is demolded, cut to a fixed length, and then cut along its longitudinal center line to obtain two L-shaped groove insulation finished products.

[0012] A further improvement of the present invention is that the gradient pressure curing process includes:

[0013] First stage: Maintain at 120-140℃ and 1.0-1.5MPa pressure for 1-2 hours, during which the axial oscillation program is executed simultaneously;

[0014] Second stage: Heat to 140-160℃, increase pressure to 2.0-3.0MPa, maintain for 4-6 hours, stop oscillation, and perform static pressure holding and curing;

[0015] The third stage: cool down to below 60℃ at a controllable rate of 1-2℃ / min and then depressurize.

[0016] A further improvement of the present invention is that the axial oscillation program is as follows: the control system controls the multiple independent pressure head units to perform alternating, wave-like additional pressing and micro-lifting actions along the workpiece axis while maintaining the basic pressure, according to a preset sequence and frequency, so as to form a dynamic pressure wave that propagates along the axis.

[0017] A further improvement of the present invention is that the resin content of epoxy glass fiber prepreg one and epoxy glass fiber prepreg two is 35%-45%, and they are made by a process including the following steps:

[0018] After impregnating the fiberglass cloth with epoxy resin, it is extruded through a pre-forming mold, and then successively passed through a preheating zone of 120-140℃, a gelation zone of 140-160℃, and a constant temperature zone of 160-180℃ to complete the curing process. Finally, it is drawn and cut into shape.

[0019] A further improvement of the present invention is that: the U-shaped hot pressing mold includes a mold frame, a fixed U-shaped mold core placed on the mold frame, and an oscillating hot pressing head assembly placed directly above the U-shaped mold core, wherein the oscillating hot pressing head assembly includes:

[0020] The main pressure head base is connected to the mold frame through a main pressure cylinder, and is driven by the main pressure cylinder to lift and lower as a whole.

[0021] Multiple independent pressure head units are mounted side by side on the main pressure head base along the axial direction of the U-shaped mold core. Each independent pressure head unit is independently controlled by a micro servo drive cylinder to press down. A row of rotating pressure rollers is installed on the bottom working surface of each independent pressure head unit. The row of pressure rollers is driven by a motor to achieve synchronous rotation. The axial direction of the pressure rollers is consistent with the radial direction of the U-shaped mold core.

[0022] The heating element, integrated inside the independent pressure head unit, is used to heat the material;

[0023] The vacuum system, connected to the cavity of the U-shaped mold core, is used to draw a vacuum during the pressing process;

[0024] The cooling system includes a coolant supply unit and piping, the piping being connected to the cooling pipes inside the U-shaped mold core;

[0025] The integrated control system is connected to the main pressure cylinder, each of the aforementioned micro servo drive cylinders, heating elements, and vacuum system. The integrated control system controls the main pressure cylinder to drive the entire hot press head assembly to press down to provide basic pressure, while simultaneously driving each pressure roller to actively rotate to achieve rolling and compaction. It also coordinates and controls each of the aforementioned micro servo drive cylinders to generate an axially propagating wave-shaped pressure distribution in their driven independent press head units, achieving wave-shaped scanning. Furthermore, it controls the cooling system to operate in the third stage of the curing process to achieve controllable cooling.

[0026] A further improvement of the present invention is that the integrated control system includes an oscillation waveform control module, which has multiple oscillation waveform modes pre-stored for sending commands to each of the micro servo drive cylinders.

[0027] The oscillation waveform mode includes at least one unidirectional traveling wave mode. In this mode, the control system controls each independent pressure head unit to perform additional pressing and resetting sequentially from one end of the workpiece to the other, forming a continuously traveling pressure wave.

[0028] A further improvement of the present invention is that the integrated control system further includes:

[0029] The resin flow optimization logic dynamically adjusts the frequency and amplitude of the wavy pressure distribution based on real-time temperature monitoring values.

[0030] The contact pressure adaptive logic adjusts the output pressure of the corresponding independent pressure head unit in real time by monitoring the current feedback of each of the micro servo drive cylinders.

[0031] A further improvement of the present invention is that the surface of the pressure roller is coated with a high-temperature resistant and non-stick coating.

[0032] A further improvement of the present invention is that the integrated control system is also configured to independently control the rotational speed of the drive motor in each of the pressure roller drive mechanisms, so that the average rotational speed of the pressure roller at the bottom of each independent pressure head unit changes according to a preset waveform and sequence. Specifically, the rotational speed of the pressure rollers of the multiple independent pressure head units is controlled to undergo a cycle of "acceleration-peak-deceleration" along the axial direction in sequence, thereby forming a rolling speed wave that propagates along the axial direction.

[0033] A further improvement of the present invention is that the bonding strength between the U-shaped preform and the thickened layer of the pad strip is not less than 15 MPa.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. This invention fundamentally solves the problem of interlayer fusion in the multi-stage hot pressing of heterogeneous materials. Traditional static secondary hot pressing will form a significant weak interface between the pre-cured substrate and the newly added thick layer. However, this invention uses dynamic pressure waves generated by axial oscillation program to continuously knead and shear the bonding interface. This mechanical action can effectively break the low-activity layer on the substrate surface, greatly promote the mutual diffusion and cross-linking reaction of epoxy resin molecules, and enable the two-layered materials to form a strong and continuous chemical bonded whole at the interface, thereby increasing the interlayer bonding strength to more than 15MPa and significantly improving the anti-delamination ability of the insulation structure under long-term thermal cycling and mechanical vibration.

[0036] 2. Due to the inherent thickness variations in the L-shaped structure, traditional processes easily lead to uneven cooling and shrinkage, causing warping. However, the oscillating pressure field of this invention subjects the material to dynamic, alternating stress during curing, rather than static directional stress. This promotes molecular chain relaxation and stress redistribution. Combined with program-controlled gradient cooling, it effectively releases and counteracts the internal stresses caused by differences in the thermal expansion coefficients of different materials and curing shrinkage, significantly reducing the warping of the final L-shaped groove insulation and fundamentally improving geometric accuracy and long-term dimensional stability.

[0037] 3. The dynamic oscillation pressure of this invention has an adaptive compensation effect on local non-uniformity of materials (such as slight layup deviations), reducing its sensitivity to process parameters. By precisely controlling the frequency and amplitude of oscillation, it is possible to ensure sufficient interlayer fusion while avoiding the application of continuous excessive compressive force to the NOMEX paper, which serves as a key insulating barrier. This prevents the porous structure from being excessively crushed or the resin from being over-wetted, thus better preserving the inherent high dielectric strength and toughness of the NOMEX paper. As a result, the product achieves excellent mechanical properties while simultaneously ensuring insulation reliability. Attached Figure Description

[0038] Figure 1 This is a flowchart of the oscillating hot pressing integral molding process for the L-shaped slot insulation of the generator rotor of the present invention.

[0039] Figure 2 This is a schematic diagram of the integral hot-press molding process for the L-shaped slot insulation of the generator rotor of the present invention.

[0040] Figure 3 This is a schematic diagram of the structure of the U-shaped hot pressing mold of the present invention.

[0041] Figure 4for Figure 3 Side view.

[0042] Figure 5 This is a comparison diagram of the interlayer interface structure of the molded part of the present invention and the prior art oscillating secondary hot pressing molded part.

[0043] Figure 6 This is a comparison diagram of the internal stress distribution and warping of the molded part of the present invention and the existing molded part.

[0044] Numbering on the map:

[0045] 1-Oscillating hot press head assembly, 2-U-shaped mold core, 3-Epoxy glass fiber prepreg one, 4-NOMEX paper, 5-Base layer, 6-Padded strip thickening layer, 7-U-shaped preform, 8-L-shaped groove insulation, 9-Epoxy glass fiber prepreg two, 10-U-shaped groove insulation, 11-Mold frame, 12-Main press head base, 13-Active cylinder, 14-Independent press head unit, 15-Miniature servo drive cylinder, 16-Pressure roller. Detailed Implementation

[0046] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0047] In the description of this invention, it should be understood that the terms indicating orientation or positional relationship, such as those based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the structure or unit referred to must have a specific orientation, and therefore should not be construed as a limitation of this invention.

[0048] In this invention, unless otherwise explicitly specified and limited, terms such as “connection,” “provided with,” and “have” should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can be described as a mechanical connection, a direct connection, or a connection through an intermediate medium. Those skilled in the art can understand the basic meaning of the above terms in this invention according to the specific circumstances.

[0049] A process for integral hot pressing of L-slot insulation for generator rotors, referring to... Figure 1 , Figure 2 A process for integral hot pressing of L-shaped slot insulation for generator rotors, characterized by the following steps:

[0050] S1. Mold Preparation and Base Layer Laying: Position a U-shaped hot pressing mold, which includes an oscillating hot pressing head assembly 1 composed of multiple independent pressing head units 13 arranged in parallel along the axial direction, a fixed U-shaped mold core 2, and a vacuum sealing system; on the platform of the U-shaped mold core 2, stack 20-30 layers of epoxy glass fiber prepreg 3 and 2-5 layers of NOMEX paper 4 in sequence to form a composite base layer 5; S2. Initial Oscillating Hot Pressing: The oscillating hot pressing head assembly 1 is pressed down to contact the composite base layer 5, and the pressure is continued to bend the composite base layer 5. Inside the cavity of the U-shaped mold core 2, under a base pressure of 120-140℃ and 0.5-1.0MPa for 10-15 minutes, the axial oscillation program is started and continued for 10-30 minutes, so that the composite base layer 5 is uniformly heated under dynamic pressure and initially shaped into a U-shaped preform 7; S3, thickening layer laying and secondary oscillation curing: Keep the U-shaped preform 7 in the mold, and lay 40-50 layers of epoxy glass fiber prepreg 9 on its inner bottom to form a padding thickening layer 6; close the mold, start the vacuum system, and execute the gradient pressure curing program;

[0051] Among them, when the oscillating hot press head performs pressing, its working surface applies dynamic pressure to the material by combining rolling and wavy scanning; S4, post-processing: the U-shaped groove insulation 10 is demolded, cut to a fixed length, and then cut along its longitudinal center line to obtain two L-shaped groove insulation 8 finished products.

[0052] This invention fundamentally solves the problem of interlayer fusion in the multi-stage hot pressing of heterogeneous materials. Traditional static secondary hot pressing will form a significant weak interface between the pre-cured substrate and the newly added thick layer. However, this invention uses dynamic pressure waves generated by axial oscillation program to continuously knead and shear the bonding interface. This mechanical action can effectively break the low-activity layer on the substrate surface, greatly promote the mutual diffusion and cross-linking reaction of epoxy resin molecules, and enable the two-layered materials to form a strong, continuous chemical bond at the interface, thereby increasing the interlayer bonding strength to over 15 MPa and significantly improving the anti-delamination ability of the insulation structure under long-term thermal cycling and mechanical vibration.

[0053] Due to the inherent thickness variations in the L-shaped structure, traditional processes often lead to uneven cooling and shrinkage, causing warping. However, the oscillating pressure field of this invention subjects the material to dynamic, alternating stress during curing, rather than static directional stress. This promotes molecular chain relaxation and stress redistribution. Combined with program-controlled gradient cooling, it effectively releases and counteracts the internal stresses caused by differences in the thermal expansion coefficients of different materials and curing shrinkage. This significantly reduces the warping of the final L-shaped groove insulation, fundamentally improving geometric accuracy and long-term dimensional stability.

[0054] The dynamic oscillation pressure of this invention has an adaptive compensation effect on local non-uniformity of materials (such as slight layup deviations), reducing its sensitivity to process parameters. By precisely controlling the frequency and amplitude of oscillation, it is possible to ensure sufficient interlayer fusion while avoiding the application of continuous excessive compressive force to the NOMEX paper, which serves as a critical insulating barrier. This prevents the porous structure from being excessively crushed or the resin from being over-wetted, thus better preserving the inherent high dielectric strength and toughness of the NOMEX paper. As a result, the product achieves excellent mechanical properties while simultaneously ensuring insulation reliability.

[0055] The gradient pressure curing process includes:

[0056] First stage: Maintain at 120-140℃ and 1.0-1.5MPa pressure for 1-2 hours, during which the axial oscillation program is executed simultaneously;

[0057] Second stage: Heat to 140-160℃, increase pressure to 2.0-3.0MPa, maintain for 4-6 hours, stop oscillation, and perform static pressure holding and curing;

[0058] The third stage: cool down to below 60℃ at a controllable rate of 1-2℃ / min and then depressurize.

[0059] The design of this gradient pressure curing process is key to achieving high-quality interlayer bonding and optimizing the internal structure. Its specific functions are as follows: In the first stage, medium temperature and pressure with synchronous axial oscillation are used. The main purpose is to promote sufficient resin flow, wetting, and interfacial diffusion between layers under suitable epoxy resin viscosity conditions, while effectively eliminating air bubbles, laying the foundation for a dense and uniform interfacial transition layer. In the second stage, the temperature and pressure are increased to higher levels and static pressure is maintained. The purpose is to allow the resin system to complete a full cross-linking and curing reaction, constructing a high-strength three-dimensional network structure, ensuring the final mechanical properties and thermal stability of the product. In the third stage, the programmed controlled cooling function aims to achieve slow, uniform cooling, causing the material to shrink synergistically, maximizing the release and homogenization of internal stress generated during curing, thereby effectively suppressing product warpage and ensuring dimensional accuracy and long-term dimensional stability.

[0060] The axial oscillation program is as follows: the control system controls multiple independent pressure head units to perform alternating, wave-like additional pressing and micro-lifting actions along the workpiece axis while maintaining the basic pressure, according to a preset sequence and frequency, forming a dynamic pressure wave that propagates along the axis.

[0061] Among them, epoxy glass fiber prepreg 13 and epoxy glass fiber prepreg 29 have a resin content of 35%-45%, and are made by a process including the following steps:

[0062] After impregnating the fiberglass cloth with epoxy resin, it is extruded through a pre-forming mold, and then successively passed through a preheating zone of 120-140℃, a gelation zone of 140-160℃, and a constant temperature zone of 160-180℃ to complete the curing process. Finally, it is drawn and cut into shape.

[0063] Preferred, refer to Figure 3 , Figure 4 The U-shaped hot pressing mold includes a mold frame 11, a fixed U-shaped mold core 2 placed on the mold frame 11, and an oscillating hot pressing head assembly 1 placed directly above the U-shaped mold core 2. The oscillating hot pressing head assembly 1 includes:

[0064] The main pressure head base 12 is connected to the mold frame 11 through the main pressure cylinder 13, and is driven by the main pressure cylinder 13 to lift and lower as a whole.

[0065] Multiple independent pressure head units 14 are mounted side by side on the main pressure head base 12 along the axial direction of the U-shaped mold core 2. Each independent pressure head unit 14 is independently controlled by a micro servo drive cylinder 15 to press down. A row of rotating pressure rollers 16 is installed on the bottom working surface of each independent pressure head unit 14. The row of pressure rollers 16 is driven by a drive motor to achieve synchronous rotation. The axial direction of the pressure rollers 16 is consistent with the radial direction of the U-shaped mold core 2.

[0066] The heating element, integrated inside the independent pressure head unit 14, is used to heat the material;

[0067] A vacuum system, connected to the cavity of the U-shaped mold core 2, is used to draw a vacuum during the pressing process;

[0068] The cooling system includes a coolant supply unit and piping, which are connected to the cooling pipes inside the U-shaped mold core 2.

[0069] The integrated control system is connected to the main pressure cylinder 13, each micro servo drive cylinder 15, heating element and vacuum system. The integrated control system controls the main pressure cylinder to drive the entire hot press head assembly to press down to provide basic pressure, while driving each pressure roller to rotate actively to achieve rolling and crushing, and coordinates the control of each micro servo drive cylinder to make the independent press head unit 14 driven by it generate a wave-shaped pressure distribution that propagates along the axial direction to achieve wave-shaped scanning; and controls the operation of the cooling system in the third stage of the curing process to achieve controllable cooling.

[0070] It is important to note that in order to ensure that the working surface of the pressure roller directly contacts the pre-pressed workpiece, the drive motor adopts a compact, embedded design. It can be installed horizontally inside the independent pressure head unit, rather than directly below or to the side. The power is transmitted through the built-in gear set. The drive motor and other components will not interfere with the pressing of multiple pressure rollers, which can ensure that the pressure is applied to the workpiece effectively and evenly.

[0071] Preferably, the integrated control system includes an oscillation waveform control module, which has multiple oscillation waveform modes pre-stored for sending commands to each micro servo drive cylinder 15;

[0072] The oscillation waveform mode includes at least one unidirectional traveling wave mode. In this mode, the control system controls each independent pressure head unit to perform additional pressing and resetting sequentially from one end of the workpiece to the other, forming a continuously traveling pressure wave.

[0073] Preferably, the integrated control system also includes:

[0074] The resin flow optimization logic dynamically adjusts the frequency and amplitude of the wavy pressure distribution based on real-time temperature monitoring values.

[0075] The contact pressure adaptive logic adjusts the output pressure of the corresponding independent pressure head unit in real time by monitoring the current feedback of each of the micro servo drive cylinders.

[0076] Preferably, the surface of the pressure roller is coated with a high-temperature resistant, non-stick coating.

[0077] Preferably, the integrated control system is further configured to: independently control the rotational speed of the drive motor in each pressure roller drive mechanism, so that the average rotational speed of the pressure roller at the bottom of each independent pressure head unit changes according to a preset waveform and sequence, specifically: controlling the rotational speed of the pressure rollers of multiple independent pressure head units to sequentially undergo a cycle of "acceleration-peak-deceleration" along the axial direction, thereby forming a rolling speed wave that propagates along the axial direction.

[0078] This application differs fundamentally from traditional pressing methods. Traditional hot pressing of glass fiber prepreg and NOMEX paper uses a single, flat pressing plate, which only achieves static, uniform pressure, offering limited effectiveness in addressing interlayer fusion and stress distribution issues. This application, however, employs an array of spaced pressure rollers instead of a single pressing plate, which is key to achieving "oscillating hot pressing." Specifically: 1. Each pressure roller actively rotates under drive, continuously and linearly compacting the material along its rolling trajectory; 2. Multiple pressure roller units are coordinated by a control system to generate a wave-like pressure distribution (wave scanning) propagating along the workpiece's axial direction. This means that any point on the workpiece surface is sequentially subjected to the rolling and pressure waves of different rollers, achieving a dynamic and comprehensive pressing effect. This design is not only feasible but also actively generates beneficial kneading and shearing effects on the interlayer interface, effectively expelling air bubbles and promoting resin flow and molecular diffusion—something static flat pressing cannot achieve. This effectively solves the problems of interlayer fusion and stress distribution in the hot pressing process of heterogeneous materials in this application.

[0079] Figure 5The diagram shows a comparison of the interlayer interface structure of the molded part of this invention and the existing oscillating secondary hot pressing molded part. The structural features clearly demonstrate that the oscillating hot pressing integral molding process of this invention is significantly superior to the traditional static secondary hot pressing method in terms of interlayer bonding quality. Traditional static secondary hot pressing results in poor bonding at the shear interface, leading to easy delamination or shear failure between layers. In contrast, this invention, through oscillating hot pressing, promotes resin flow and recombination under the action of high-frequency micro-vibration and thermo-mechanical coupling, forming a strong interpenetrating structure. This effectively enhances the interlayer bonding strength and interfacial toughness, thereby improving the overall mechanical properties and insulation reliability of the generator rotor L-slot insulation component. The bonding strength between the U-shaped preform 7 and the padding thickening layer 6 in this invention is not less than 15 MPa.

[0080] Figure 6 This diagram compares the internal stress distribution and warpage of the molded part of this invention with that of existing molded parts. The stress distribution and structural deformation results clearly demonstrate that the oscillating hot-pressing integrated molding process of this invention is significantly superior to the traditional static hot-pressing method in suppressing residual stress and structural deformation. Existing static hot-pressing technology suffers from uneven thermo-mechanical fields and inconsistent resin curing shrinkage, leading to concentrated internal residual stress and significant warpage deformation of the L-shaped slot insulation. In contrast, this invention, through high-frequency micro-oscillation and gradient pressure control, promotes uniform resin flow and stress release, achieving uniform internal stress distribution. The final molded part exhibits no visible warpage deformation, significantly improving dimensional stability and meeting the requirements of high-precision assembly and long-term reliability for generator rotor slot insulation.

[0081] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A vibration hot pressing integral molding process for L-shaped slot insulation of a generator rotor, characterized in that, Specifically, the following steps are included: S1. Mold preparation and base layer laying: Position a U-shaped hot pressing mold, which includes an oscillating hot pressing head assembly composed of multiple independent pressing head units arranged in parallel along the axial direction, a fixed U-shaped mold core, and a vacuum sealing system; on the platform of the U-shaped mold core, 20-30 layers of epoxy glass fiber prepreg and 2-5 layers of NOMEX paper are stacked in sequence to form a composite base layer; S2. Initial oscillating hot pressing: The oscillating hot pressing head assembly is pressed down to contact the composite substrate layer and continuously pressed down to bend the composite substrate layer into the cavity of the U-shaped mold core. Under the basic pressure of 120-140℃ and 0.5-1.0MPa, the axial oscillation program is started for 10-30 minutes to make the composite substrate layer uniformly heated under dynamic pressure and initially shaped into a U-shaped preform. S3. Thickening layer laying and secondary vibration curing: Keep the U-shaped preform in the mold, lay 40-50 layers of epoxy glass fiber prepreg II on its inner bottom to form a padding thickening layer; close the mold, start the vacuum system, and execute the gradient pressure curing procedure; When the oscillating hot press head performs pressing, its working surface applies dynamic pressure to the material by combining rolling and wave scanning. S4. Post-processing: Demold the U-shaped groove insulation, cut it to a fixed length, and then cut it along its longitudinal center line to obtain two L-shaped groove insulation finished products.

2. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 1, characterized in that, The gradient pressure curing process includes: First stage: Maintain at 120-140℃ and 1.0-1.5MPa pressure for 1-2 hours, during which the axial oscillation program is executed simultaneously; Second stage: Heat to 140-160℃, increase pressure to 2.0-3.0MPa, maintain for 4-6 hours, stop oscillation, and perform static pressure holding and curing; The third stage: cool down to below 60℃ at a controllable rate of 1-2℃ / min and then depressurize.

3. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 2, characterized in that, The axial oscillation program is as follows: the control system controls the multiple independent pressure head units to perform alternating, wave-like additional pressing and micro-lifting actions along the workpiece axis while maintaining the basic pressure, according to a preset sequence and frequency, so as to form a dynamic pressure wave that propagates along the axis.

4. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 3, characterized in that, The epoxy glass fiber prepreg one and epoxy glass fiber prepreg two have a resin content of 35%-45%, and are manufactured by a process including the following steps: After impregnating the fiberglass cloth with epoxy resin, it is extruded through a pre-forming mold, and then successively passed through a preheating zone of 120-140℃, a gelation zone of 140-160℃, and a constant temperature zone of 160-180℃ to complete the curing process. Finally, it is drawn and cut into shape.

5. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 4, characterized in that, The U-shaped hot pressing mold includes a mold frame, a fixed U-shaped mold core placed on the mold frame, and an oscillating hot pressing head assembly placed directly above the U-shaped mold core. The oscillating hot pressing head assembly includes: The main pressure head base is connected to the mold frame through a main pressure cylinder, and is driven by the main pressure cylinder to lift and lower as a whole. Multiple independent pressure head units are mounted side by side on the main pressure head base along the axial direction of the U-shaped mold core. Each independent pressure head unit is independently controlled by a micro servo drive cylinder to press down. A row of rotating pressure rollers is installed on the bottom working surface of each independent pressure head unit. The row of pressure rollers rotates synchronously through a drive motor. The axial direction of the pressure rollers is consistent with the radial direction of the U-shaped mold core. The heating element, integrated inside the independent pressure head unit, is used to heat the material; A vacuum system, connected to the cavity of the U-shaped mold core, is used to draw a vacuum during the pressing process; The cooling system includes a coolant supply unit and piping, the piping being connected to a cooling pipe inside the U-shaped mold core; The integrated control system is signal-connected to the main pressure cylinder, each of the micro servo drive cylinders, the heating element, and the vacuum system. The integrated control system controls the main pressure cylinder to drive the entire hot press head assembly to press down to provide basic pressure, while driving each pressure roller to actively rotate to achieve rolling and crushing, and coordinates the control of each of the micro servo drive cylinders to generate wavy pressure distribution along the axial direction of the driven independent press head unit to achieve wavy scanning; and controls the operation of the cooling system in the third stage of the curing process to achieve controllable cooling.

6. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 5, characterized in that, The integrated control system includes an oscillation waveform control module, which has multiple oscillation waveform modes pre-stored and is used to send commands to each of the micro servo drive cylinders. The oscillation waveform mode includes at least one unidirectional traveling wave mode. In this mode, the control system controls each independent pressure head unit to perform additional pressing and resetting sequentially from one end of the workpiece to the other, forming a continuously traveling pressure wave.

7. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 6, characterized in that, The integrated control system also includes: The resin flow optimization logic dynamically adjusts the frequency and amplitude of the wavy pressure distribution based on real-time temperature monitoring values. The contact pressure adaptive logic adjusts the output pressure of the corresponding independent pressure head unit in real time by monitoring the current feedback of each of the micro servo drive cylinders.

8. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 7, characterized in that, The surface of the pressure roller is coated with a high-temperature resistant, non-stick coating.

9. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 8, characterized in that, The integrated control system is also configured to: independently control the rotational speed of the drive motor in each of the pressure roller drive mechanisms, so that the average rotational speed of the pressure roller at the bottom of each independent pressure head unit changes according to a preset waveform and sequence. Specifically, the rotational speed of the pressure rollers of the multiple independent pressure head units is controlled to undergo a cycle of "acceleration-peak-deceleration" along the axial direction in sequence, thereby forming a rolling speed wave that propagates along the axial direction.

10. The oscillating hot pressing integral molding process for L-shaped slot insulation of a generator rotor according to claim 9, characterized in that, The bonding strength between the U-shaped preform and the thickened layer of the pad strip is not less than 15 MPa.

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