Multi-field linkage injection molding method of magnet

Abstract

The invention discloses a multi-field linkage injection molding method of a magnet, and relates to the technical field of injection molding, the injection molding method of the magnet is applied to a mold with an adjustable magnetic field, and the injection molding method of the magnet comprises the following steps: S1, injecting a magnetic powder material into a mold cavity to form a molded blank; wherein the injection pressure ranges from 50 MPa to 100 MPa, the temperature in the mold cavity ranges from 95 DEG C to 140 DEG C, meanwhile, a magnetic field is applied to the interior of the mold cavity, and the magnetic field intensity is controlled to be gradually increased to the target intensity from the initial set intensity; s2, the formed blank body is subjected to cooling treatment; and S3, the cooled formed blank is subjected to degreasing treatment and sintering treatment in sequence, and the magnet is prepared. According to the injection molding method provided by the invention, the magnet with high magnetic performance, excellent mechanical strength and high dimensional stability can be prepared, so that the qualified rate of the molded magnet is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of injection molding, in particular to a multi-field linkage injection molding method of a magnet. BACKGROUND

[0002] In the magnet injection molding process adopted in the related art, the problem of coordinated control of multiple physical fields has not been effectively solved. Specifically, the magnet injection molding process is essentially a complex multiphase flow and solidification process of a magnet powder-binder melt under the action of a magnetic field, involving strong coupling of temperature field, flow field (injection force field) and magnetic field. However, the prior art often lacks systematic coordinated control of the above multiple physical fields: on the one hand, mismatched process parameters will interfere with the preset orientation magnetic field, destroying the ordered arrangement of the magnetic powder; on the other hand, a static or single magnetic field cannot adapt to the dynamic flow of the material in the complex cavity during the injection process, resulting in significant differences in the orientation effect of the magnetic powder in different regions. The direct consequence of this lack of multiple physical field coordination is that the magnet is not uniformly filled and the orientation degree is not uniform, which causes the green body to be prone to poor magnetic performance consistency, dimensional deformation and other problems during subsequent forming and sintering, resulting in a low product qualification rate. SUMMARY

[0003] The main purpose of the present application is to provide a multi-field linkage injection molding method of a magnet, aiming to improve the qualification rate of the magnet after molding through the coordinated control between the temperature field, the injection force field and the magnetic field.

[0004] To achieve the above-mentioned purpose, the present application provides a multi-field linkage injection molding method of a magnet, applied to a mold with an adjustable magnetic field, the injection molding method of the magnet comprising: Step S1: injecting a magnetic powder material into a mold cavity to form a molded embryo; wherein the injection pressure is between 50 MPa and 100 MPa, the temperature in the mold cavity is between 95℃ and 140℃, a magnetic field is applied to the mold cavity at the same time, and the magnetic field strength is gradually increased from an initial set strength to a target strength; Step S2: cooling the molded embryo; Step S3: sequentially performing a debinding treatment and a sintering treatment on the cooled molded embryo to obtain a magnet.

[0005] In an embodiment, before the step S1, the method further comprises: Step S0: maintaining the magnetic field strength in the mold cavity at an initial set strength for a first set period of time, the initial set strength being 55% to 75% of the target strength.

[0006] In an embodiment, the step S1 comprises a first sub-step of injecting the magnetic powder material into the mold cavity for a second set period of time until filling to 30% of the volume of the mold cavity; In the first sub-step, the magnetic powder material is injected into the mold cavity at a speed of 6 mm / s to 9 mm / s, and the magnetic field strength is gradually increased from the initial set strength to 75% to 82% of the target strength at a first rate.

[0007] In an embodiment, in the first sub-step, the first rate is set to be between 0.015 T / s to 0.035 T / s.

[0008] In an embodiment, the step S1 further comprises a second sub-step of continuing to inject the magnetic powder material into the mold cavity for a third set period of time until filling to 70% of the volume of the mold cavity; In the second sub-step, the magnetic powder material is injected into the mold cavity at a speed of 9 mm / s to 12 mm / s, and the magnetic field strength is gradually increased from 75% to 82% of the target strength to the target strength at a second rate, which is smaller than the first rate.

[0009] In an embodiment, in the second sub-step, the second rate is set to be between 0.012 T / s to 0.025 T / s.

[0010] In an embodiment, the step S1 further comprises a third sub-step of continuing to inject the magnetic powder material into the mold cavity for a fourth preset period of time until the mold cavity is completely filled; In the third sub-step, the magnetic powder material is injected into the mold cavity at a speed of 6 mm / s to 9 mm / s, and the magnetic field strength is maintained at the target strength.

[0011] In an embodiment, the step S1 further comprises a pressure maintaining step: In a fifth preset period of time, the magnetic field strength is maintained at the target strength, and the mold cavity filled with the magnetic powder material is subjected to pressure maintaining.

[0012] In an embodiment, the step S2 comprises: In the process of reducing the temperature of the shaped body from the first temperature value to the second temperature value, the magnetic field strength is gradually reduced from the target strength to the first set strength at a third rate; In the process of reducing the temperature of the shaped body from the second temperature value to the third temperature value, the magnetic field strength is gradually reduced from the first set strength to the second set strength at a fourth rate; wherein the fourth rate is smaller than the third rate.

[0013] In an embodiment, the mold cavity has a plurality of independently temperature-controllable regions, the plurality of regions including a first region, a second region, a third region, and a fourth region, the first region corresponding to a main body portion of the shaped embryo, the second region corresponding to a thin-walled portion of the shaped embryo, the third region corresponding to a thin-rib portion of the shaped embryo, and the fourth region corresponding to a gate of the mold cavity. In step S1, the temperature of the first region is controlled to be maintained at 95-105°C, the temperature of the second region is controlled to be maintained at 115-135°C, the temperature of the third region is controlled to be maintained at 125-140°C, and the temperature of the fourth region is controlled to be maintained at 105-120°C.

[0014] In the technical solution of the present application, the embryo is formed by synergistically regulating the injection force field, the temperature field, and the magnetic field under specific parameters. Specifically, the magnetic powder material is injected into the mold cavity at 95-140°C under an injection pressure of 50-100 MPa to form a shaped embryo, and a magnetic field with an initial strength gradually increasing to a target strength is synchronously applied to ensure the consistency of the orientation of the magnetic powder. Then, the shape and size precision of the embryo are fixed through a cooling process. Finally, the binder in the magnetic powder material is completely removed and the magnetic powder is densified through a debinding and sintering process, and a magnet with high magnetic performance, excellent mechanical strength, and high dimensional stability is finally successfully prepared, thereby improving the qualified rate of the magnet after shaping. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0016] Figure 1 Structure schematic diagram of an embodiment of the mold provided by the present application; Figure 2 Structure schematic diagram of a Halbach array assembled in the mold provided by the present application; Figure 1 Structure schematic diagram of a cross-sectional structure of an embodiment of the Halbach array in the mold; Figure 3 Structure schematic diagram of a cross-sectional structure of the Halbach array; Figure 2 Structure schematic diagram of a cross-sectional structure of the Halbach array; Figure 4 Structure schematic diagram of another embodiment of the mold provided by the present application; Figure 5 Structure schematic diagram of another embodiment of the mold provided by the present application; Figure 2A table of magnetic induction strength of a Halbach array; Figure 6 A flow chart of an embodiment of the injection molding method provided by the present application.

[0017] Brief Description of the Drawings 100, mold; 1, fixed mold; 2, movable mold; 3, coil; 200, Halbach array.

[0018] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0020] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0021] In addition, if the embodiments of the present application involve descriptions of “first”, “second”, etc., the descriptions of “first”, “second”, etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by “first”, “second” can explicitly or implicitly include at least one of the features. In addition, “and / or” or “and / or” appearing throughout the text means that the three parallel solutions are included, for example, “A and / or B” includes A solution, or B solution, or A and B solutions are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of those of ordinary skill in the art, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor is it within the protection scope of the present application.

[0022] In the magnet injection molding process adopted in the related art, the problem of coordinated control of multiple physical fields has not been effectively solved. Specifically, the magnet injection molding process is essentially a complex multiphase flow and solidification process of a magnetic powder-binder melt under the action of a magnetic field, involving strong coupling of temperature field, flow field (injection force field) and magnetic field. However, the existing technology often lacks systematic coordination of the above multiple physical fields: on the one hand, mismatched process parameters will interfere with the preset orientation magnetic field, destroying the ordered arrangement of the magnetic powder; on the other hand, a static or single magnetic field cannot adapt to the dynamic flow of the material in the complex cavity during the injection process, resulting in significant differences in the orientation effect of the magnetic powder in different regions. The direct consequence of this lack of multiple physical field coordination is uneven filling and different orientation degrees in the magnet, which makes the green body prone to poor magnetic performance consistency, dimensional deformation and other problems during subsequent forming and sintering, resulting in a low product qualification rate.

[0023] First, the injection molding device applied by the injection molding method of the magnet proposed in the embodiments of the present application is described.

[0024] In some embodiments of the present application, the injection molding device includes a rack, an injection system, a mold system, a multi-field regulation system, a monitoring system, a control system, and an automated auxiliary system, which cooperate with each other to realize precise forming of complex structure magnets.

[0025] In some embodiments of the present application, the rack adopts a high-strength steel structure, including a base, a column, a beam, and a workbench, for supporting various functional modules in the injection molding device. The base is internally provided with a damping device to reduce the influence of vibration on the forming precision of the magnet during injection; the workbench can be driven by a servo motor to move in three degrees of freedom, such as X-axis, Y-axis, and Z-axis, to facilitate the installation and positioning of the mold 100.

[0026] In some embodiments of the present application, the injection system includes a barrel, a screw, a driving device, and a feeding device, which is used to heat and plasticize the mixture of rare earth iron-based alloy magnetic powder and binder and then inject it into the mold cavity.

[0027] In some embodiments of the present application, the barrel adopts a bimetallic bushing structure, with a wear-resistant alloy in the inner layer and a partition heating device in the outer layer, which can realize gradient temperature control in the axial direction of the barrel. The inner wall of the barrel is provided with special spiral grooves to enhance the mixing and plasticizing effect of the mixture.

[0028] Specifically, the temperature control range of the partition heating device is between 60° and 300°, and the temperature fluctuation is stably controlled within ±1°C.

[0029] In some embodiments of the present application, the screw is a barrier screw with a length-diameter ratio of 18:1 to 25:1 and a compression ratio of 2.5:1 to 4:1, which can effectively realize uniform plasticization and stable conveying of the mixture. The screw is driven by a servo motor through a reduction box, and the rotation speed can be adjusted within a range of 0 to 300 r / min, with a control accuracy of ±1 r / min.

[0030] In some embodiments of the present application, the driving device adopts an electro-hydraulic servo driving mode, and the injection pressure can be adjusted within a range of 0 to 150 MPa, the injection speed can be adjusted within a range of 0.1 mm / s to 50 mm / s, and the holding pressure can be adjusted within a range of 0 to 120 MPa, which can ensure stable feeding of the mold cavity.

[0031] In some embodiments of the present application, the feeding device is a loss-in-weight feeder, which can accurately control the feeding amount, and the control accuracy of the feeding device is controlled within ±0.2%.

[0032] In some embodiments of the present application, the mold system includes a mold 100, a guide mechanism, an ejection mechanism, and a cooling system. The mold 100 includes a fixed mold 1 and a movable mold 2, and a molding cavity with a complex structure can be formed between the fixed mold 1 and the movable mold 2.

[0033] Please refer to Figure 1 In some embodiments of the present application, the mold 100 includes the fixed mold 1 and the movable mold 2, which are made of P20 mold steel. The fixed mold 1 and the movable mold 2 are combined to form a mold cavity, and the surface of the mold cavity is subjected to nitriding treatment to improve hardness, wear resistance, and service life. According to the processing requirements of the complex structure magnet product, the mold cavity can be designed as a multi-cavity, a special-shaped structure, and provided with an optimized runner and gate system to reduce the feeding flow resistance.

[0034] In some embodiments of the present application, the guide mechanism adopts a guide pillar and guide sleeve structure with a cooperation accuracy of H7 / g6 to ensure accurate clamping of the fixed mold 1 and the movable mold 2.

[0035] In some embodiments of the present application, the ejection mechanism adopts a hydraulic ejection mode, and the ejection speed can be adjusted within a range of 0.5 mm / s to 20 mm / s, and the ejection stroke can be adjusted to ensure stable removal of the molded embryo.

[0036] In some embodiments of the present application, the cooling system is integrated inside the mold 100 and adopts a spiral cooling water channel design. The cooling system adjusts the cooling water in a closed loop through a temperature control unit, and the water temperature is adjusted within a range of 5°C to 50°C, so as to realize accurate control of the temperature of the mold 100, and the control accuracy can reach ±1°C.

[0037] In some embodiments of this application, the multi-field control system includes a magnetic field generating system, a gradient temperature control system, and a precise force field control system to achieve coordinated control of the magnetic field, temperature field, and force field during the injection molding process of the magnet.

[0038] In some embodiments of this application, the magnetic field generating system has two configuration methods.

[0039] In one embodiment, the magnetic field generating system includes a Hellbeck array 200 assembled with the mold 100, through which the magnetic field strength within the mold cavity is adjusted.

[0040] In another embodiment, the magnetic field generating system includes a coil 3 disposed within the mold 100, which is used to adjust the magnetic field strength within the mold cavity.

[0041] Among them, such as Figures 2-3 The image shows a Hellbeck array 200, which includes magnets and iron components. The magnets provide the original magnetic field, while the iron components guide, concentrate, and redistribute the magnetic flux, thereby enhancing the magnetic field on the target side.

[0042] like Figure 4 The diagram shows a coil 3 installed inside the mold 100, and the magnetic induction intensity of the coil 3 can change.

[0043] In some embodiments of this application, the gradient temperature control system includes a mold zone heating device, a barrel zone heating device, and a temperature monitoring unit.

[0044] Among them, the mold zone heating device adopts an embedded heating tube, which divides the mold cavity into multiple independent temperature control zones, and realizes precise temperature control of each zone within the range of 60℃ to 160℃, with an accuracy of ±1℃.

[0045] The barrel zone heating device uses a cast aluminum heater and is divided into three zones: feeding section, compression section, and metering section, to achieve gradient temperature control.

[0046] The feeding section refers to the initial area of ​​the feed cylinder, which is mainly responsible for receiving and conveying materials.

[0047] The compression section refers to the middle area of ​​the barrel, which is mainly responsible for compacting, melting and compressing the material to realize the transformation of the material from solid to liquid phase.

[0048] The metering section refers to the last section in the barrel before the material leaves the barrel. It is mainly responsible for homogenization, pressurization, and quantitative delivery of the material to the mold 100, while ensuring the accuracy of the injection volume.

[0049] The temperature monitoring unit uses a thermocouple sensor with an accuracy of ±0.5℃ to collect temperature data of the mold 100 and the barrel in real time and feed it back to the control system.

[0050] In some embodiments of the present application, the precise force field control system is linked with the driving device of the injection system, integrating three control modules of injection pressure control module, holding pressure control module and clamping force control module. Among them, the injection pressure control module realizes continuous and precise adjustment of pressure through an electro-hydraulic proportional valve; the holding pressure control module adopts a segmented strategy that can be adjusted in real time to adapt to the filling process; the clamping force control module relies on a servo motor driven elbow mechanism to ensure stable clamping and prevent material overflow.

[0051] In some embodiments of the present application, the monitoring system includes a process parameter monitoring module and a product quality online monitoring module for real-time acquisition of key parameters and product quality information during the forming process.

[0052] The process parameter monitoring module includes pressure sensors, temperature sensors, displacement sensors, magnetic field sensors, etc., which can real-time collect process parameters such as injection pressure, barrel temperature, mold temperature, screw displacement, magnetic field strength, etc., with a sampling frequency greater than or equal to 1000 Hz.

[0053] Specifically, the measurement range of the pressure sensor is between 0 and 200 MPa, with an accuracy of ±0.5% FS.

[0054] The temperature sensor includes a thermocouple, an infrared temperature measuring instrument, etc., with a measurement accuracy of ±0.5°C.

[0055] The displacement sensor includes a grating ruler, with a measurement accuracy of ±0.001 mm.

[0056] The magnetic field sensor includes a Hall sensor, with a measurement accuracy of ±0.005 T.

[0057] The product quality detection module integrates an industrial camera and an image recognition system to perform online detection of the appearance size and surface quality of the formed blank, with a detection accuracy of ±0.01 mm, and can identify common defects such as material shortage, flash, and cracks. At the same time, the product quality detection module also includes an online magnetic property detector to quickly detect the preliminary magnetic properties of the blank, with a detection time of less than or equal to 10 s / piece.

[0058] In some embodiments of the present application, the automated auxiliary system includes an automatic picking device, an automatic detection and sorting device, and a waste recycling device.

[0059] The automatic picking device uses a multi-axis robot equipped with a visual positioning system, which can accurately identify the position of the formed blank, realize automatic picking and placing of the formed blank, and has a picking efficiency of greater than or equal to 10 pieces / min.

[0060] The automatic detection and sorting device cooperates with the product quality online monitoring module to automatically sort and stack the qualified molded blanks and mark and isolate the unqualified products.

[0061] The waste recycling device automatically collects, crushes and recycles the sprue and runner waste generated during the injection process. The incorporation ratio of the recycled material can be set through the control system to realize the recycling of resources.

[0062] Based on the above injection molding device, the application also proposes a multi-field linkage injection molding method for a magnet. The adjustable magnetic field mold 100 is as described above and will not be repeated here.

[0063] Please refer to Figure 6 In some embodiments of the present application, the injection molding method comprises: Step S1: injecting a magnetic powder material into a mold cavity to form a molded embryo; wherein the injection pressure is between 50MPa and 100MPa, the temperature in the mold cavity is between 95℃ and 140℃, a magnetic field is applied to the mold cavity at the same time, and the magnetic field strength is gradually increased from the initial set strength to the target strength.

[0064] In step S1, the molded embryo is formed by injecting the magnetic powder material into the mold cavity at a temperature of 95℃ to 140℃ with an injection pressure of 50MPa to 100MPa, and a magnetic field with an initial strength gradually increasing to a target strength is applied at the same time. This can realize the coordinated control of the injection force field, temperature field and magnetic field, effectively balance the magnetic powder orientation effect and the stability of the melt flow, avoid the disturbance of the melt flow front by the high-speed magnetic field change, and prevent the generation of eddy current to destroy the magnetic powder arrangement, thereby ensuring the ordered arrangement of the magnetic powder along the easy axis direction of the product and reducing the orientation deviation of the magnetic powder.

[0065] In some embodiments of the present application, the injection molding method further comprises: Step S2: cooling treatment of the molded embryo.

[0066] In step S2, the molded embryo after injection molding is subjected to cooling treatment, which can fix the shape of the magnet, prevent defects and ensure dimensional accuracy.

[0067] During injection molding, the magnet and the magnetic powder material of the plastic are in a molten state. If they are allowed to cool naturally, warping, deformation or internal shrinkage may occur due to uneven shrinkage of each part, which not only affects the appearance and assembly accuracy, but also leads to uneven distribution of magnetic properties. By controlling the cooling process, the molded embryo can be uniformly solidified, and its final shape and internal structure can be locked, so that the mold cavity filling rate is higher.

[0068] Meanwhile, the cooling treatment can also enable the secondary magnetization of the magnet to achieve a higher magnetic effect.

[0069] It should be noted that the secondary magnetization step is arranged after the sintering process step.

[0070] In some embodiments of the present application, the injection molding method further comprises: Step S3: sequentially performing debinding treatment and sintering treatment on the cooled molding blank to obtain the magnet.

[0071] In step S3, the debinding and sintering treatment on the cooled molding blank can convert the mixed blank of plastic and metal powder into a dense and solid pure metal magnet. The debinding is to remove the plastic binder added during molding by heating or the like, so as to clear the space for the subsequent step; and then the sintering is performed in a protective atmosphere much higher than the melting point of the metal, so that the loose metal powder particles atomically diffuse and fuse at high temperature, shrink and densify, thereby eliminating internal pores and forming a high-density microstructure to ensure the excellent magnetic performance and mechanical strength of the magnet.

[0072] In summary, in the technical solution of the present application, the injection force field, temperature field and magnetic field are synergistically controlled to form a blank under specific parameters. Specifically, the magnetic powder material is injected into a mold cavity at a temperature of 95-140°C under an injection pressure of 50-100 MPa, and a magnetic field with an initial strength gradually increasing to a target strength is applied synchronously to ensure the consistency of the orientation of the magnetic powder; then the shape and size accuracy of the blank are fixed through a cooling process; finally, the binder in the magnetic powder material is completely removed and the magnetic powder is densified through debinding and sintering processes, and a magnet with high magnetic performance, excellent mechanical strength and high dimensional stability is successfully prepared to improve the qualified rate of the magnet after molding.

[0073] In some embodiments of the present application, the value of the target strength is not greater than 1.6T.

[0074] Please refer to Figure 5 As Figure 5 The magnetic induction strength table of the Halbach array 200 is shown, and the curve can represent the surface magnetic induction strength distribution of the permanent magnet. The magnetic induction strength represented by the Y-axis can be 1.6T as the target strength in the present application.

[0075] In some embodiments of the present application, the method further comprises, before step S1: Step S0: maintaining the magnetic field strength in the mold cavity at an initial set strength for a first set period of time, the initial set strength being 55-75% of the target strength.

[0076] In step S0, a stable magnetic field environment can be established in the mold cavity in advance before the magnetic powder is injected, so as to uniformly form a preliminary magnetic field atmosphere inside the mold cavity, reduce the hysteresis of the magnetic powder in response to the magnetic field in the subsequent injection filling process, and especially for the areas such as fine ribs of the product after molding which are prone to insufficient orientation, the orientation willingness of the magnetic powder can be activated in advance to avoid the orientation disorder of the magnetic powder due to the untimely response during filling.

[0077] The initial setting strength is 55% to 75% of the target strength of the adjustable magnetic field, that is, the initial setting strength can be 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, or 75% of the target strength of the adjustable magnetic field. The value of the initial setting strength is not limited to the listed proportion values, and other unlisted proportion values in this range are also applicable.

[0078] Specifically, taking 1.5T as the target strength of the adjustable magnetic field as an example, the initial setting strength is controlled to be 65% of the target strength, and the initial setting strength is 0.975T. In the first preset time period, the strength of the adjustable magnetic field is kept stable at 0.975T, and no magnetic field strength adjustment is performed, so as to stabilize the magnetic field environment inside the mold cavity and uniformly form a preliminary magnetic field atmosphere inside the mold cavity, reduce the hysteresis of the magnetic powder in response to the magnetic field in the subsequent injection filling process, and especially for the areas such as fine ribs of the product after molding which are prone to insufficient orientation, the orientation willingness of the magnetic powder can be activated in advance to avoid the orientation disorder of the magnetic powder due to the untimely response during filling.

[0079] In some embodiments of the present application, the first preset time period is between 5S and 10S, so that a stable magnetic field environment is formed inside the mold cavity to provide a uniform magnetic field basis for subsequent material filling.

[0080] The value of the first preset time period can be 5S, 5.5S, 6S, 6.5S, 7S, 7.5S, 8S, 8.5S, 9S, 9.5S, or 10S. The value of the first preset time period is not limited to the listed proportion values, and other unlisted proportion values in this range are also applicable.

[0081] Specifically, the first preset time period is 8S.

[0082] In some embodiments of the present application, step S1 includes a first sub-step: In the second setting time period, the magnetic powder material is injected into the mold cavity until it is filled to 30% of the volume of the mold cavity; In the first sub-step, the speed of injecting the magnetic powder material into the mold cavity is 6mm / s to 9mm / s, and the magnetic field strength is gradually increased from the initial setting strength to 75% to 82% of the target strength of the adjustable magnetic field at a first rate.

[0083] In the first sub-step, since the magnetic field strength is gradually increased from the initial setting strength to 75% to 82% of the target strength of the adjustable magnetic field, the change of the magnetic field strength is relatively slow, and since the injection speed is maintained at 6mm / s to 9mm / s, the speed of the magnetic powder material injected into the mold cavity is also relatively slow; wherein the slow rate of change of the magnetic field strength is suitable for the low-speed flow of the magnetic powder material solution, guiding the smooth flow of the magnetic powder along with the front of the magnetic powder material solution, avoiding the agglomeration of the magnetic powder due to the sudden increase of the magnetic field strength, and at the same time, the gradual increase of the magnetic field strength at this rate can ensure the preliminary ordered arrangement of the magnetic powder in the inlet and flow channel area of the cavity, laying a good foundation for the orientation of the magnetic powder in the subsequent filling stage. In the gradual increase of the initial setting strength to 75% to 82% of the target strength of the adjustable magnetic field at a first rate, the initial setting strength can be increased to 75%, 76%, 77%, 78%, 79%, 80%, 81%, or 82% of the target strength. Other unlisted proportion values in this range are also applicable.

[0084] It should be noted that the above injection speed is the speed of the screw of the injection system advancing in the barrel, which is positively correlated with the filling speed of the magnetic powder material into the mold cavity.

[0085] In some embodiments of the present application, the first rate is set to be between 0.015T / s and 0.035T / s; in this way, a slow change in the strength of the magnetic field is provided, avoiding the agglomeration of the magnetic powder due to the sudden increase of the magnetic field strength, and at the same time, the gradual increase of the magnetic field strength at this rate can ensure the preliminary ordered arrangement of the magnetic powder in the inlet and flow channel area of the mold cavity, laying a good foundation for the orientation of the magnetic powder in the subsequent filling stage. If the first rate is less than 0.015T / s, the change of the magnetic field strength is too slow, and the magnetic powder does not have enough time to arrange along the magnetic field arrangement direction in the first sub-step, the magnetic field orientation efficiency is low, and the magnetic performance of the final obtained magnet product cannot meet the standard requirements.

[0086] If the first rate is greater than 0.035T / s, the change of the magnetic field strength is too fast, and the sudden change of the magnetic field will make the magnetic powder agglomerate, destroy the flowability of the material, cause the mold cavity to be not fully filled, and the orientation of the magnetic powder is chaotic, resulting in poor consistency of the magnetic performance of the final obtained magnet product.

[0087] The first rate can be 0.015T / s, 0.016T / s, 0.017T / s, 0.018T / s, 0.019T / s, 0.020T / s, 0.021T / s, 0.022T / s, 0.023T / s, 0.024T / s, 0.025T / s, 0.026T / s, 0.027T / s, 0.028T / s, 0.029T / s, 0.030T / s, 0.031T / s, 0.032T / s, 0.033T / s, 0.034T / s, 0.035T / s. The first rate is not limited to the listed values, and other values in the range are also applicable.

[0088] The length of the second set time period is flexibly adjusted according to the volume of the mold cavity and the injection speed, so as to ensure that the magnetic powder material flows at a low speed in the mold cavity.

[0089] Specifically, the length of the second set time period is 10s, the injection system advances the magnetic powder material solution to fill the mold cavity at a speed of 6mm / s to 9mm / s, and the magnetic field strength gradually increases from 0.975T to 81% to 82% of the target strength, that is, the magnetic field strength increases to 1.225T after the second set time period, and the adjustment rate is controlled at 0.025T / s. The magnetic field strength change rate is matched with the low-speed flowing magnetic powder material solution, which guides the magnetic powder to flow smoothly and synchronously with the front edge of the magnetic powder material solution, avoids the agglomeration of the magnetic powder due to the sudden increase of the magnetic field strength, and at the same time, the gradual increase of the magnetic field strength at this rate can ensure the preliminary ordered arrangement of the magnetic powder at the inlet and flow channel area of the mold cavity, and lay a good foundation for the subsequent orientation of the magnetic powder in the filling stage.

[0090] It should be noted that the front edge of the magnetic powder material solution refers to the boundary of the most forward end when the solution advances in the mold cavity.

[0091] In some embodiments of the present application, step S1 further comprises a second sub-step: In the third set time period, the magnetic powder material is continuously injected into the mold cavity until it is filled to 70% of the volume of the mold cavity. In the second sub-step, the speed of injecting the magnetic powder material into the mold cavity is 9mm / s to 12mm / s, and the magnetic field strength gradually increases from 75% to 82% of the target strength to the target strength at a second rate, which is less than the first rate.

[0092] In the second sub-step, the adjustment rate of the magnetic field needs to be reduced, that is, the magnetic field strength change rate is adjusted from the first rate to a second rate in this stage to balance the magnetic powder orientation effect and the melt flow stability of the magnetic powder material, avoid the high-speed magnetic field change interfering with the melt flow front of the magnetic powder material, and prevent the vortex phenomenon from destroying the magnetic powder arrangement. At this rate, the magnetic field strength can be continuously increased to strengthen the magnetic powder orientation, and the melt with a medium-speed flow can be adapted to ensure that the magnetic powder in the key areas such as complex cavities and thin walls fully responds to the magnetic field, is orderly arranged along the easy axis direction of the product, and the orientation deviation is reduced.

[0093] The length of the third set time period is flexibly adjusted according to the volume size of the mold cavity and the injection speed, so as to ensure that the magnetic powder material flows at a medium speed in the mold cavity.

[0094] Specifically, the length of the third set time period is between 11S and 12S, the injection system advances the magnetic powder material solution to fill the mold cavity at a speed of 9mm / s to 12mm / s, the magnetic field strength continues to increase from 1.225T to the target strength 1.5T, and the second rate is 0.023T / s. In this way, the magnetic powder orientation effect and the melt flow stability of the magnetic powder material are balanced, the high-speed magnetic field change is avoided to interfere with the melt flow front of the magnetic powder material, and the vortex phenomenon is prevented from destroying the magnetic powder arrangement. At this rate, the magnetic field strength can be continuously increased to strengthen the magnetic powder orientation, and the melt with a medium-speed flow can be adapted to ensure that the magnetic powder in the key areas such as complex cavities and thin walls fully responds to the magnetic field, is orderly arranged along the easy axis direction of the product, and the orientation deviation is reduced.

[0095] In some embodiments of the present application, the second rate is set to be between 0.012T / s and 0.025T / s, so as to continuously strengthen the magnetic powder orientation without interfering with the flow front of the solution due to the too fast change of the magnetic field.

[0096] If the second rate is lower than 0.012T / s, the magnetic field strength is increased too slowly, so that the magnetic powder orientation driving force is insufficient, the magnetic powder cannot be fully arranged along the easy axis in the complex areas of the mold cavity, the pre-magnetization effect is poor, and the secondary magnetization and product magnetic performance are affected.

[0097] If the second rate is higher than 0.025T / s, the magnetic field will change suddenly, which easily interferes with the melt flow front, causes the magnetic powder to agglomerate, and the filling is not full, and finally the magnetic performance consistency is poor.

[0098] The second rate can be 0.012T / s, 0.013T / s, 0.014T / s, 0.015T / s, 0.016T / s, 0.017T / s, 0.018T / s, 0.019T / s, 0.020T / s, 0.021T / s, 0.022T / s, 0.023T / s, 0.024T / s, 0.025T / s. The value of the second rate is not limited to the listed ratio values, and other unlisted ratio values in the range are also applicable.

[0099] In some embodiments of the present application, step S1 further comprises a third sub-step: In the fourth preset time period, the injection of the magnetic powder material into the mold cavity continues until the mold cavity is completely filled; In the third sub-step, the speed of injecting the magnetic powder material into the mold cavity is 6mm / s to 9mm / s, and the magnetic field strength is maintained at the target strength.

[0100] In the third sub-step, by reducing the flow speed of the magnetic powder stream melt, the impact caused by the too fast speed when the magnetic powder stream melt fills the end of the cavity is avoided. The constant strong magnetic field can keep the magnetic powder in the filled area in a stable orientation state, and at the same time ensure that the magnetic powder in the last filled area is fully oriented, avoiding the inconsistency of the magnetic powder orientation in different areas caused by the fluctuation of the magnetic field strength, and ensuring the uniformity of the magnetic properties of the entire product.

[0101] Specifically, the magnetic field strength is maintained at 1.5T.

[0102] It should be noted that the speed of injecting the magnetic powder material in the above is positively correlated with the injection pressure, so the control of the injection speed can realize the regulation and control of the injection pressure.

[0103] In some embodiments of the present application, step S1 further comprises a pressure maintaining step: In the fifth preset time period, the magnetic field strength is maintained at the target strength, and the mold cavity filled with the magnetic powder material is pressure maintained.

[0104] In the pressure maintaining step, shrinkage and porosity defects of the blank can be prevented by feeding, and at the same time the magnetic powder orientation effect is maintained. The magnetic field strength is maintained at the target strength, which is constant and does not need to be adjusted. The constant strong magnetic field can ensure that the magnetic powder does not deviate from the optimal orientation direction due to the change of the melt pressure during the pressure maintaining process, and the orientation results of the early stage are stable, which lays a foundation for the orientation of the magnetic powder in the subsequent cooling and setting stage, avoids the rebound of the magnetic powder orientation due to the decrease of the magnetic field strength, and affects the magnetic properties of the product. In some embodiments of the present application, the fifth preset time period is between 5S and 12S.

[0105] If the length of the fifth preset time period is less than 5S, the risk of shrinkage and porosity of the shaped blank body increases, the magnetic field pressure maintaining time is short, the orientation effect of the magnetic powder is insufficient, and the product magnetic performance compliance rate decreases.

[0106] If the length of the fifth preset time period is greater than 12S, the time consumption of the whole process increases, the production efficiency decreases, the internal stress of the shaped blank body concentrates, the deformation rate after cooling increases, and the size precision and magnetic performance consistency of the complex structure magnet are poor.

[0107] The value of the fifth preset time period can be 5S, 5.5S, 6S, 6.5S, 7S, 7.5S, 8S, 8.5S, 9S, 9.5S, 10S, 10.5S, 11S, 11.5S, or 12S. The value of the fifth preset time period is not limited to the listed ratio values, and other unlisted ratio values in this range are also applicable.

[0108] In some embodiments of the present application, step S2 comprises: during the process of reducing the temperature of the shaped blank body from the first temperature value to the second temperature value, gradually reducing the magnetic field strength from the target strength to a first set strength at a third rate; during the process of reducing the temperature of the shaped blank body from the second temperature value to a third temperature value, gradually reducing the magnetic field strength from the first set strength to a second set strength at a fourth rate; wherein the fourth rate is less than the third rate.

[0109] In step S2, the magnetic field strength is gradually reduced to avoid the magnetic stress caused by the sudden change of the magnetic field from causing the shaped blank body to deform, especially for complex and special-shaped structures. Slow and segmented change of the magnetic field can keep the structure of the shaped blank body stable during the cooling and shrinkage process, and the low-intensity magnetic field residue can prevent the orientation disorder of the magnetic powder caused by thermal motion during the cooling process, ensuring the stability of the magnetic performance of the final product.

[0110] In some embodiments of the present application, the second set strength is 10% of the target strength.

[0111] Specifically, step S2 starts after the pressure maintaining ends, and is specifically divided into a temperature reduction initial stage and a temperature reduction middle and later stage.

[0112] In some embodiments of the present application, the first temperature value is between 130° and 140°.

[0113] In some embodiments of the present application, the third temperature value is between 50°C and 80°C.

[0114] The following is an example.

[0115] In the initial stage of the temperature reduction, the temperature of the shaped body is reduced from the first temperature value 130°C to the second temperature value 90°C, and the magnetic field strength is reduced from the target strength 1.5T to the first set strength 0.6T at the third rate 0.078T / s.

[0116] In the middle and later stage of the temperature reduction, the temperature of the shaped body is reduced from the second temperature value 90°C to the third temperature value 60°C, and the magnetic field strength is reduced from the first set strength 0.6T to the second set strength 0.15T at the fourth rate 0.072T / s.

[0117] In some embodiments of the present application, the step of gradually reducing the magnetic field strength from the target strength to the first set strength at the third rate in the process of reducing the temperature of the shaped body from the first temperature value to the second temperature value further comprises: In the sixth preset time period, the magnetic field strength is maintained at the target strength.

[0118] In this way, the orientation structure of the magnetic powder can be further consolidated after the pressure maintaining step is completely finished.

[0119] Specifically, the value of the sixth preset time period can be between 3S and 5S.

[0120] In some embodiments of the present application, the step of gradually reducing the magnetic field strength from the target strength to the first set strength at the third rate in the process of reducing the temperature of the shaped body from the first temperature value to the second temperature value, and gradually reducing the magnetic field strength from the first set strength to the second set strength at the fourth rate in the process of reducing the temperature of the shaped body from the second temperature value to the third temperature value, the process time is between 10S and 15S, and the third rate and the fourth rate are both 0.07T / s to 0.08T / s. This is because the presence of the magnetic field will produce a "magnetic viscosity" effect on the oriented magnetic powder, hindering its relaxation due to cooling shrinkage. By gradually reducing the magnetic field strength and the increasing rigidity of the material, the magnetic stress can be gradually released, avoiding the rebound or deformation of the magnetic powder arrangement caused by the sudden disappearance of the external field, while continuing to guide the magnetic powder to complete the final orientation when there is still fine adjustment ability.

[0121] In some embodiments of the present application, the step of gradually reducing the magnetic field strength from the first set strength to the second set strength at the fourth rate in the process of reducing the temperature of the shaped body from the second temperature value to the third temperature value further comprises: In the seventh preset time period, the magnetic field strength is gradually attenuated to zero.

[0122] The seventh preset time period is between 5S and 10S, and the speed of magnetic field decay is between 0.02T / s and 0.04T / s, so as to eliminate any residual magnetization force, ensure that the blank completes the final cooling in a state of complete absence of external field interference, and prevent the generation of tiny anisotropic stress.

[0123] In some embodiments of the present application, the mold cavity has a plurality of regions capable of independent temperature control, including a first region, a second region, a third region, and a fourth region. The first region corresponds to the main body portion of the molded embryo, the second region corresponds to the thin-walled portion of the molded embryo, the third region corresponds to the thin rib portion of the molded embryo, and the fourth region corresponds to the gate of the mold cavity.

[0124] The main body portion refers to a structural portion with a thickness of not less than 3mm and a total volume of more than 50% of the volume of the mold cavity; The thin-walled portion refers to a structural portion with a thickness of not more than 2mm and a total volume of not more than 20% of the volume of the mold cavity; The thin rib refers to a structure with a thickness of not more than 1.5mm and a height-to-width ratio (i.e., the ratio of height to width) of more than 3, and a total volume of not more than 25% of the volume of the mold cavity.

[0125] In some embodiments of the present application, in step S1, the temperature of the first region is controlled to be between 95℃ and 105℃, the temperature of the second region is controlled to be between 115℃ and 135℃, the temperature of the third region is controlled to be between 125℃ and 140℃, and the temperature of the fourth region is controlled to be between 105℃ and 120℃.

[0126] In this way, the temperature in the complex regions of the mold cavity is appropriately increased to reduce the viscosity of the melt, and the injection force field control and magnetic field control ensure that the melt is filled sufficiently everywhere in the mold cavity.

[0127] If the thin-walled portion, thin rib, and high-depth-ratio region structure of the product are complex, the melt is not easy to flow in these places, so the temperature of these parts is increased, i.e., the temperature of the second region and the third region is greater than that of the first region, so that the viscosity of the melt corresponding to the second region and the third region is reduced to ensure that the melt is filled sufficiently in the second region and the third region.

[0128] In addition, by controlling the temperature of the fourth region to be between 105℃ and 120℃, the melt in the regions of the mold cavity is prevented from cooling too early and causing the gate to be blocked.

[0129] The temperature value of the first region can be 95℃, 96℃, 97℃, 98℃, 99℃, 100℃, 101℃, 102℃, 103℃, 104℃, 105℃. The temperature value of the first region is not limited to the listed proportion values, and other unlisted proportion values in the range are also applicable.

[0130] The temperature value of the second region can be 115℃, 116℃, 117℃, 118℃, 119℃, 120℃, 121℃, 122℃, 123℃, 124℃, 125℃, 126℃, 127℃, 128℃, 129℃, 130℃, 131℃, 132℃, 133℃, 134℃, 135℃. The temperature value of the second region is not limited to the listed proportion values, and other unlisted proportion values in the range are also applicable.

[0131] The temperature value of the third region can be 125℃, 126℃, 127℃, 128℃, 129℃, 130℃, 131℃, 132℃, 133℃, 134℃, 135℃, 136℃, 137℃, 138℃, 139℃, 140℃. The temperature value of the third region is not limited to the listed proportion values, and other unlisted proportion values in the range are also applicable.

[0132] The temperature value of the fourth region can be 105℃, 106℃, 107℃, 108℃, 109℃, 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃, 120℃. The temperature value of the fourth region is not limited to the listed proportion values, and other unlisted proportion values in the range are also applicable.

[0133] In some embodiments of the present application, step S3 comprises the following steps: Blank taking out: starting the movable mold moving mechanism, opening the mold 100, taking out the formed blank from the mold cavity by the automatic taking device and placing it on the conveying belt.

[0134] Debinding treatment: placing the formed blank in a debinding furnace, using a multi-effect composite debinding process, first performing catalytic debinding to remove part of the binder; then performing thermal debinding under heating in the sintering furnace stage to remove the remaining binder and greatly improve the product performance; finally performing catalytic debinding at 300℃-400℃ to reduce the residual harmful elements.

[0135] Among them, the heating rate of the thermal debinding stage is controlled at 10℃ / min-15℃ / min, and the holding time is 2h-3h, so as to adapt to the heating rhythm of the sintering furnace, quickly remove the remaining binder, and at the same time improve the product density and magnetic performance through high temperature.

[0136] The catalytic debinding stage controls the temperature rising rate to be 3℃ / min-8℃ / min, and the holding time is 0.5h-1h; wherein, the low-temperature slow rising can accurately remove harmful element residues.

[0137] In combination with the above steps, the carbon content of the debound blank body can be guaranteed to be ≤500ppm.

[0138] Sintering treatment: the debound blank body is placed in a vacuum sintering furnace, sintered at 1050℃-1150℃ for 2h-4h, and the vacuum degree is ≤1×10 -3 Pa. During the sintering process, a segmented heating strategy is adopted, and the heating rate is 5-10℃ / min. The holding time is 1h-2h at 600-800℃ to eliminate internal stress. After sintering, the furnace is cooled to room temperature, and a sintered rare earth iron-based alloy blank body with a complex structure is obtained.

[0139] Subsequent processing and detection: according to product requirements, a small amount of machining (machining weight reduction ratio ≤10%) is performed on the sintered blank body to correct the size accuracy. Subsequently, the magnetic properties (remanence, coercive force, etc.), size accuracy, and surface quality of the product are comprehensively detected, and qualified products are put into storage for use.

[0140] In some embodiments of the present application, the injection molding of the magnet further includes a preparation step of the magnetic powder material, which includes three steps of magnetic powder pretreatment, adhesive preparation, and feed mixing.

[0141] Magnetic powder pretreatment: Nd-Fe-B rare earth iron-based alloy magnetic powder is selected, and the powder with a particle size D50<5μm is prepared by airflow milling process. The magnetic powder is placed in a vacuum drying box and dried at 80-120℃ for 4h-6h to remove the surface adsorbed moisture. Subsequently, a metal modification layer (such as Zn, Al, etc.) is coated on the surface of the magnetic powder by rotary diffusion method, with a coating thickness of 0.1-0.5μm, to improve the oxidation resistance and flowability of the magnetic powder.

[0142] Adhesive preparation: a paraffin-polyethylene-polypropylene composite adhesive system is used, wherein the proportion of paraffin is 50%-60%, the proportion of polyethylene is 20%-30%, and the proportion of polypropylene is 10%-20%. After mixing the components in proportion, heating and melting at 150-180℃, and stirring uniformly, the adhesive is prepared.

[0143] Feed mixing: the pretreated rare earth iron-based alloy magnetic powder is mixed with the adhesive, and then extruded and granulated by a double-screw extruder to prepare feed particles with a diameter of 3mm-5mm, which are placed in a sealed bag for use.

[0144] The injection molding method of the application is applied to the preparation of a 12-pole radially oriented magnetic ring blank with an outer diameter of 25 mm, a height of 6.5 mm, and a thinnest wall thickness of only 0.8 mm. The temperature of the mold 100 corresponding to the thin wall and thin rib part is set to 130°C, and the temperature of the main body part is set between 95°C and 105°C; at the same time, the dynamic magnetic field generating system generates and maintains a tangential magnetic field of 1.2T at the cavity. Compared with the conventional constant temperature mold 100 and static magnetic field process, the filling rate of this complex blank is increased from 85% to more than 99.9%, the magnetic powder orientation degree is increased by 35%, the blank deformation after sintering is less than 0.05 mm, and the good product rate is increased from less than 50% to more than 90%, fully proving the effectiveness and advancement of the application.

[0145] The above only describes exemplary embodiments of the application, and does not limit the patent scope of the application, and any equivalent structural transformation made under the technical concept of the application, or direct / indirect application in other related technical fields, is included in the patent protection scope of the application.

Claims

1. A multi-field linkage injection molding method for a magnet, applied to a mold with an adjustable magnetic field, characterized in that, include: Step S1: Inject magnetic powder material into the mold cavity to form a molded preform; wherein, the injection pressure is between 50MPa and 100MPa, the temperature inside the mold cavity is between 95℃ and 140℃, and at the same time, a magnetic field is applied to the mold cavity, and the magnetic field strength is controlled to gradually increase from the initial set strength to the target strength. Step S2: Cool the molded preform. Step S3: The cooled molded blank is subjected to degreasing and sintering treatment in sequence to obtain a magnet.

2. The injection molding method as described in claim 1, characterized in that, Before step S1, the procedure also includes: Step S0: During a first set time period, the magnetic field strength inside the mold cavity is maintained at an initial set strength, which is 55% to 75% of the target strength.

3. The injection molding method as described in claim 2, characterized in that, Step S1 includes a first sub-step: during a second set time period, injecting the magnetic powder material into the mold cavity until it fills 30% of the volume of the mold cavity; In the first sub-step, the magnetic powder material is injected into the mold cavity at a rate of 6 mm / s to 9 mm / s, and the magnetic field strength is gradually increased from the initial set strength to 75% to 82% of the target strength at a first rate.

4. The injection molding method as described in claim 3, characterized in that, In the first sub-step, the first rate is set between 0.015T / s and 0.035T / s.

5. The injection molding method as described in claim 3, characterized in that, Step S1 further includes a second sub-step: during a third set time period, continuing to inject the magnetic powder material into the mold cavity until it fills 70% of the volume of the mold cavity; In the second sub-step, the magnetic powder material is injected into the mold cavity at a rate of 9 mm / s to 12 mm / s, and the magnetic field strength is gradually increased from 75% to 82% of the target strength to the target strength at a second rate, wherein the second rate is less than the first rate.

6. The injection molding method as described in claim 5, characterized in that, In the second sub-step, the second rate is set between 0.012T / s and 0.025T / s.

7. The injection molding method as described in claim 5, characterized in that, Step S1 further includes a third sub-step: during a fourth preset time period, continue to inject the magnetic powder material into the mold cavity until the mold cavity is completely filled; In the third sub-step, the magnetic powder material is injected into the mold cavity at a rate of 6 mm / s to 9 mm / s, and the magnetic field strength is maintained at the target strength.

8. The injection molding method as described in claim 7, characterized in that, Step S1 further includes a pressure holding step: During the fifth preset time period, the magnetic field strength is maintained at the target strength, and the mold cavity filled with the magnetic powder material is pressurized.

9. The injection molding method as described in claim 1, characterized in that, Step S2 includes: During the process of reducing the temperature of the molded preform from a first temperature value to a second temperature value, the magnetic field strength is gradually reduced from the target strength to a first set strength at a third rate. During the process of reducing the temperature of the molded preform from the second temperature value to the third temperature value, the magnetic field strength is gradually reduced from the first set strength to the second set strength at a fourth rate. The fourth rate is less than the third rate.

10. The injection molding method as described in claim 1, characterized in that, The mold cavity has multiple independently temperature-controlled areas, including a first area, a second area, a third area, and a fourth area. The first area corresponds to the main body of the molded blank, the second area corresponds to the thin-walled part of the molded blank, the third area corresponds to the fine rib part of the molded blank, and the fourth area corresponds to the gate of the mold cavity. In step S1, the temperature of the first region is controlled to be maintained between 95°C and 105°C, the temperature of the second region is controlled to be maintained between 115°C and 135°C, the temperature of the third region is controlled to be maintained between 125°C and 140°C, and the temperature of the fourth region is controlled to be maintained between 105°C and 120°C.

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