Preparation method for controlling magnet performance through forming process

Abstract

The invention discloses a preparation method for controlling magnet performance through a forming process, and belongs to the technical field of sintered neodymium-iron-boron permanent magnet materials. The method comprises the steps that S1, an upper pressing head assembly moves upwards to a preset powder adding position on a mold, and then sintered neodymium-iron-boron powder is quantitatively added into the mold; s2, the upper pressure head assembly moves downwards to a preset micro-descending position on the mold; s3, the lower pressing head assembly moves downwards and moves to a preset pre-pressing position on the grinding tool, and the sintered neodymium iron boron powder in the mold is pre-pressed; s4, after pre-pressing of the sintered neodymium iron boron powder is completed, magnetizing orientation operation is conducted on the sintered neodymium iron boron powder in the mold; s5, after the magnetizing orientation operation is completed, the upper pressing head assembly and the lower pressing head assembly synchronously move towards the middle of the mold, and the sintered neodymium-iron-boron powder is subjected to bidirectional opposite pressing; and S6, after the sintered neodymium-iron-boron powder is pressed, demagnetization operation is carried out. The technical scheme is used for solving the problem that powder distribution in a die cavity is not uniform when neodymium iron boron powder is pressed and sintered.

Description

Technical Field

[0001] The invention belongs to the technical field of sintered NdFeB permanent magnet materials, and in particular relates to a preparation method for controlling magnet performance through a molding process. Background Art

[0002] Sintered NdFeB permanent magnet materials are widely used in electronics, electromechanics, communications, instrumentation, medical and military fields due to their excellent comprehensive magnetic properties. However, the traditional preparation methods often have problems such as poor magnet consistency and unstable performance during the molding process, which affects product quality and performance. The process of controlling the performance of sintered NdFeB through the molding process is a key link in the preparation process of sintered NdFeB. The molding process determines the geometric shape, size and orientation of the magnet, and these factors directly affect the final performance of the magnet.

[0003] At present, the manufacturing process of sintered NdFeB materials mainly includes the steps of permanent magnet powder preparation, pressing and sintering. The pressing step is mainly as follows: add the sintered NdFeB powder into the mold cavity, apply the orientation current after scraping, and use the upper and lower mold rods to press the powder in the orientation magnetic field to prepare rare earth permanent magnet materials. However, due to the magnetic field, the magnetic field at the two poles in the mold cavity is higher than the central magnetic field, which will result in more powder and less powder in the center, resulting in the problem that the final performance fails to reach the optimal level. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a preparation method for controlling the performance of magnets through a molding process, so as to solve the problem in the prior art that when pressing and sintering NdFeB powder, there is more powder at the two poles and less powder at the center in the mold cavity, resulting in poor performance after pressing and molding.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method for controlling the performance of a magnet through a molding process, wherein a pre-pressing position, a powder adding position and a micro-reduction position are sequentially arranged from the upper surface to the lower surface of the mold, and a lower pressing head assembly is arranged above the upper surface of the mold, and an upper pressing head assembly is arranged below the lower surface of the mold;

[0007] The preparation method comprises the following steps:

[0008] S1. The upper pressure head assembly moves upward to the preset powder adding position on the mold, and then quantitatively adds sintered NdFeB powder to the mold;

[0009] S2. After the sintered NdFeB powder is added, the upper pressure head assembly moves downward to the preset micro-drop position on the mold;

[0010] S3, the lower pressure head assembly moves downward to the preset pre-pressing position on the mold to pre-press the sintered NdFeB powder in the mold;

[0011] S4. After the pre-pressing of the sintered NdFeB powder is completed, the sintered NdFeB powder in the mold is magnetized and oriented;

[0012] S5. After the magnetization and orientation operation is completed, the upper and lower pressure head assemblies move synchronously toward the middle of the mold to perform bidirectional pressure on the sintered NdFeB powder;

[0013] S6. After the sintered NdFeB powder is pressed, demagnetization operation is performed;

[0014] S7. After demagnetization is completed, the upper and lower pressure head assemblies move upward synchronously to push the sintered NdFeB powder out of the mold after pressing.

[0015] Furthermore, the pre-compression density of the sintered NdFeB powder is between 2.5 and 2.8, and the compression density of the sintered NdFeB powder is between 3.9 and 4.1.

[0016] Furthermore, in step S1, after the sintered NdFeB powder is added, a triangular fork is used to evenly insert it into the mold cavity four times.

[0017] Furthermore, the upper pressure head assembly includes a lifting hydraulic rod and an upper pressure plate, and the lower pressure head assembly includes a telescopic hydraulic rod and a lower pressure plate. In step S2, when the upper pressure head assembly moves down to a slightly lowered position, a hammer assembly is provided on the upper pressure head assembly to tap and compact the sintered NdFeB powder in the mold.

[0018] Furthermore, four groups of hammer assemblies are evenly distributed on the outer circumference of the mold, and the hammer assembly includes a symmetrically arranged light rod, one end of the light rod is provided with an end plate, the other end of the light rod is provided with a retaining ring, and the retaining ring is arranged close to the jacking hydraulic rod, the light rod is provided with a slider, a first spring is provided between the slider and the baffle arranged on the outside, the first spring is sleeved on the light rod, the slider is provided with a vertical plate, one end of the vertical plate is fixed on the slider, the other end of the vertical plate is located on the outer side of the middle and lower part of the mold, and a knocking block is provided on the other end of the vertical plate, and the knocking block is connected to the other end of the vertical plate, and at least one wedge block is provided on the part of the vertical plate located at the lower end of the mold, a mounting block is provided on the output rod of the jacking hydraulic rod, the middle part of the mounting block is threadedly connected to the output rod of the jacking hydraulic rod, and baffles are provided on the sides of the mounting block facing the wedge block, one end of the baffle is connected to the mounting block, and the other end of the baffle is arranged toward the wedge block, and the projections of the baffle and the wedge block in the vertical direction partially overlap.

[0019] Furthermore, a groove is provided on the side of the mounting block on which the baffle is set, a gap is provided between the end of the groove and the upper surface of the mounting block, a rotating shaft is provided in one end of the groove facing the upper surface of the mounting block, and one end of the baffle is rotatably connected to the rotating shaft.

[0020] Furthermore, a fixing plate is provided on the upper surface of the mounting block, one end of the fixing plate is fixedly connected to the mounting block, and a second spring is provided on the other end of the fixing plate, and both ends of the second spring are respectively fixed to the fixing plate and the baffle.

[0021] Furthermore, the knocking block is detachably connected to the end of the vertical plate.

[0022] Furthermore, the knocking block is made of rubber.

[0023] Furthermore, the wedge blocks in the four groups of hammer assemblies are arranged at different heights.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention optimizes the molding process to standardize and quantify the molding process, thereby achieving stable performance. At the same time, the coercive force can be increased by process control or the remanence can be slightly reduced to increase the coercive force. The operation method is simple, low-cost, and easy to promote and apply.

[0026] (2) The technical solution improves the density of the powder through the pre-pressing process, that is, the powders at the center are in a tightly squeezed state, which effectively suppresses the problem of the center powder moving to the two poles due to the fact that the magnetic field at the two poles in the mold is higher than the central magnetic field strength under the subsequent magnetic field. Therefore, it effectively avoids the phenomenon of less powder in the center and more powder at the two poles during the final pressing, and effectively improves the unevenness of the powder density distribution. At the same time, the pre-pressing method can also increase the coercive force without affecting the residual magnetism, and at the same time reduce deformation and improve dimensional consistency.

[0027] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0029] Figure 1 It is a schematic diagram of setting a pre-pressing position, a powder adding position and a slight lowering position on the mold in the present invention;

[0030] Figure 2It is a three-dimensional schematic diagram of a hammer assembly arranged on the outer side of the mold in the present invention;

[0031] Figure 3 It is a schematic cross-sectional view of a hammer assembly arranged on the outer side of the mold in the present invention;

[0032] Figure 4 It is a schematic diagram of the glass body of the hammer assembly in the present invention;

[0033] Figure 5 For the present invention Figure 4 A local enlarged schematic diagram of point A in the middle.

[0034] The following are marked in the accompanying drawings:

[0035] a. Upper surface of mold; b. Pre-pressing position; c. Powder adding position; d. Slightly lowering position; 1. Telescopic hydraulic rod; 2. Lower pressure plate; 3. Lifting hydraulic rod; 4. Upper pressure plate; 5. Mold; 6. Mounting plate; 7. End plate; 8. Polish rod; 9. Slider; 10. Retaining ring; 11. Vertical plate; 12. Wedge block; 13. Knocking block; 14. Mounting block; 15. Groove; 16. Baffle; 17. Rotating shaft; 18. Fixed plate; 19. Second spring; 20. First spring. DETAILED DESCRIPTION

[0036] like Figure 1 to Figure 5 As shown, the present invention is a preparation method for controlling the performance of a magnet by a molding process, wherein a pre-pressing position b, a powder adding position c and a micro-reduction position d are sequentially arranged from the upper surface a to the lower surface of the mold, and a lower pressing head assembly is arranged above the upper surface a of the mold, and an upper pressing head assembly is arranged below the lower surface of the mold 5;

[0037] The preparation method comprises the following steps:

[0038] S1, the upper pressure head assembly moves upward to the preset powder adding position c on the mold 5, and then quantitatively adds sintered NdFeB powder to the mold 5;

[0039] S2. After the sintered NdFeB powder is added, the upper pressure head assembly moves downward to the preset micro-drop position d on the mold 5;

[0040] The advantages of setting the micro-drop position d are: (1) Dropping to the micro-drop position d is conducive to placing the mold 5 in the middle during orientation, controlling the molding position, and increasing the service life of the mold 5. That is, when molding at the same location, if the mold 5 is damaged, the molding position can be changed by changing the micro-drop position d, thereby avoiding the damaged part and increasing the service life; (2) Dropping to the micro-drop position d is conducive to the self-flow of the powder. Following the micro-drop process, the powder distribution will be more uniform.

[0041] It should be noted that in this solution, a is the upper surface of the mold, and the pre-pressing position b is calculated by the set pre-pressing density. According to the powder weight, cavity size and pre-pressing density, the distance between the upper and lower cylinders during pre-pressing can be calculated to set the pre-pressing position b. c is adjusted by the actual powder addition, and is determined according to the actual powder addition. d is set according to the mold situation by changing the molding position. The distance from the pre-pressing position b to the micro-drop position d, the cavity size and powder weight are used to calculate the density, which is the pre-pressing density. The powder adding height c is adjusted according to the actual situation. The abcd of different molds are adjusted according to the pre-pressing density and the actual situation of the mold.

[0042] S3, the lower pressure head assembly moves downward to the preset pre-pressing position b on the mold to pre-press the sintered NdFeB powder in the mold 5; it should be noted that when the lower pressure head assembly moves to the pre-pressing position b, the pre-pressing step has been completed.

[0043] S4. After the pre-pressing of the sintered NdFeB powder is completed, the sintered NdFeB powder in the mold 5 is subjected to magnetization and orientation operation. The magnetization and orientation operation is a prior art and will not be described in detail in this technical solution.

[0044] S5. After the magnetization and orientation operation is completed, the upper and lower pressure head assemblies move synchronously toward the middle of the mold 5 to perform bidirectional pressure on the sintered NdFeB powder; the upper and lower pressure head assemblies move at the same speed to extrude the sintered NdFeB powder, that is, the density of the sintered NdFeB powder after extrusion will be relatively uniform, and the pressing effect will be better.

[0045] Specifically, the magnetic field strength is 1.5-2T, the applied pressure is 10-15MPa, the pressing movement speed is 20-25mm / s, and the density after pressing is 3.9-4.1g / cm3.

[0046] S6. After the sintered NdFeB powder is pressed, demagnetization operation is performed;

[0047] S7, after demagnetization is completed, the upper pressing head assembly and the lower pressing head assembly move upward synchronously to push the sintered NdFeB powder after pressing out of the mold 5.

[0048] In an practicable manner, the pre-compression density of the sintered NdFeB powder is between 2.5 and 2.8, and the compression density of the sintered NdFeB powder is between 3.9 and 4.1.

[0049] In one practicable manner, in step S1, after the sintered NdFeB powder is added, a triangular fork is evenly inserted into the mold cavity four times to preliminarily eliminate defects such as powder bridging and improve the subsequent pressing effect.

[0050] In order to further illustrate the influence of controlling the pre-pressing density on the Br and Hcj of the magnet, N52 and N38MT are selected for specific implementation. During the manufacturing process, the smelting, hydrogen crushing and airflow grinding processes are the same as normal, and only the molding process is changed. Through the new molding process, the normal molding process generally corresponds to a pre-pressing density of 2.2. The test is carried out with the same powder and the pre-pressing density of 2.5, 2.6, 2.7, and 2.8 at the same time sequence. After molding, it is subjected to 200MPA isostatic pressing and sintered in the same environment to ensure consistency except for the pre-pressing density. The experimental results are as follows:

[0051]

[0052]

[0053] It can be seen from the above test results that in the magnet with brand N52, the values ​​of Br and Hcj are within the pre-compression density range, and increase with the increase of pre-compression density; but in N38MT, at pre-compression densities of 2.5 and 2.8, the values ​​of Br and Hcj of the magnet increase more, and at pre-compression densities of 2.6 and 2.7, the values ​​of Br and Hcj of the magnet increase significantly, and it can be seen from Examples 5 and 6 that when the pre-compression density is too large (exceeding the range in the present technical solution), the values ​​of Br and Hcj will decrease instead.

[0054] In summary, in the preparation method provided by the present invention, by increasing the pre-pressing density, the coercive force can be increased by 0.5 without substantially reducing the remanence, and at the same time, the coercive force can be increased more while slightly reducing the remanence, that is, the technical solution can fine-tune the performance of the blank according to the pre-pressing density. Specifically, the fine-tuning object can be to only increase the coercive force or slightly reduce the remanence to increase the coercive force.

[0055] In an practicable manner, the upper ram assembly includes a lifting hydraulic rod 3 and an upper pressing plate 4, and the lower ram assembly includes a telescopic hydraulic rod 1 and a lower pressing plate 2. In step S2, when the upper ram assembly moves down to the slightly lowered position d, a hammer assembly is provided on the upper ram assembly to tap and compact the sintered NdFeB powder in the mold 5. After the sintered NdFeB powder is added to the mold 5, pores or insufficient density may appear inside the mold, which will subsequently affect the performance of the pressed blank.

[0056] In an operative manner, four groups of hammer assemblies are evenly distributed on the outer circumference of the mold 5, and the hammer assemblies include symmetrically arranged light rods 8, one end of which is provided with an end plate 7, which is fixed to the edge of the mounting plate 6, and the other end of which is provided with a retaining ring 10, which is arranged close to the lifting hydraulic rod 3, and a slider 9 is provided on the light rod 8, and a first spring 20 is provided between the slider 9 and the retaining plate 16 arranged on the outer side, and the first spring 20 is sleeved on the light rod 8, and a vertical plate 11 is provided on the slider 9, and one end of the vertical plate 11 is fixed to the slider 9, and the other end of the vertical plate 11 is located on the outer side of the middle and lower part of the mold 5, and A knocking block 13 is provided on the other end of the vertical plate 11, and the knocking block 13 is connected to the other end of the vertical plate 11 and arranged toward the mold 5. At least one wedge block 12 is provided on the portion of the vertical plate 11 located at the lower end of the mold 5. A mounting block 14 is provided on the output rod of the jacking hydraulic rod 3. The middle part of the mounting block 14 is threadedly connected to the output rod of the jacking hydraulic rod 3, and a baffle 16 is provided on the side of the mounting block 14 facing the wedge block 12. One end of the baffle 16 is connected to the mounting block 14, and the other end of the baffle 16 is arranged toward the wedge block 12. The projections of the baffle 16 and the wedge block 12 in the vertical direction partially overlap.

[0057] It is not difficult to understand that the length of the baffle 16 is preferably able to enter the interior of the mold 5, which is convenient for the subsequent pushing operation; of course, if the length of the baffle 16 is long, then the length of the output end of the lifting hydraulic rod 3 can be increased. The working principle of the above technical solution is: when the lifting hydraulic rod 3 moves downward, the baffle 16 contacts the inclined surface of the wedge block 12, thereby pushing the wedge block 12 to move outward, thereby compressing the first spring 20. When the baffle 16 and the wedge block 12 are disengaged, under the action of the first spring 20, the sliding block will be quickly pushed back, thereby driving the knocking block 13 at the upper end of the vertical plate 11 to knock on the outer surface of the mold 5, thereby causing the mold 5 to vibrate, and then can drive the sintered NdFeB powder therein to vibrate, thereby achieving the purpose of vibration compaction. At the same time, the vibration of the mold 5 can also cause the residual sintered NdFeB powder on the inner side of the mold 5 to fall off, and then merge with the sintered NdFeB powder at the bottom, further improving the subsequent pressing effect.

[0058] Of course, in this technical solution, when the jacking hydraulic rod 3 moves upward, it is necessary to rotate the mounting block 14 so that the baffle 16 avoids the wedge block 12 to avoid movement interference, that is, through the threaded connection, it is also possible to choose whether the hammer assembly is required.

[0059] In one practicable manner, a groove 15 is provided on the side of the mounting block 14 on which the baffle 16 is set, and a gap is provided between the end of the groove 15 and the upper surface of the mounting block 14, that is, the groove 15 is not connected to the upper surface of the mounting block 14, but is connected to the small surface of the mounting block 14, and a rotating shaft 17 is provided in one end of the groove 15 facing the upper surface of the mounting block 14, and one end of the baffle 16 is rotatably connected to the rotating shaft 17. It is not difficult to understand that there should be no contact between the upper surface of the baffle 16 and the end of the groove 15 to avoid interference between the end of the baffle 16 and the end face of the groove 15 when the baffle 16 rotates downward.

[0060] That is, the baffle 16 can rotate downward, but due to the obstruction of the inner wall of the upper end of the groove 15, the upward rotation angle is small. Therefore, with this arrangement, the baffle 16 can squeeze the wedge block 12 to move, and during the upward movement, after the two are separated, the baffle 16 automatically rotates upward, thereby avoiding movement interference during the upward movement.

[0061] In one feasible manner, a fixing plate 18 is provided on the upper surface of the mounting block 14, one end of the fixing plate 18 is fixedly connected to the mounting block 14, and a second spring 19 is provided on the other end of the fixing plate 18, and the two ends of the second spring 19 are respectively fixed to the fixing plate 18 and the baffle 16. The advantage of the arrangement of the second spring 19 is that the baffle 16 is always in a parallel state, that is, when the baffle 16 moves upward, it contacts the wedge block 12, overcomes the resistance of the spring and rotates, and then moves to the top of the wedge block 12. After moving upward, the second spring 19 resets, driving the baffle 16 to reset, and then when moving downward, it can act on the wedge block 12. That is, this arrangement can automatically avoid motion interference and push the wedge block 12 without human intervention.

[0062] In one practicable manner, the knocking block 13 is detachably connected to the end of the vertical plate 11 , and different heights can be set as needed to knock on different heights of the side of the mold 5 .

[0063] In one practicable manner, the knocking block 13 is made of rubber to avoid the noise generated by metal collision and protect the mold 5 at the same time.

[0064] In one feasible manner, the wedge blocks 12 in the four groups of hammer assemblies are arranged at different heights. The advantage of different heights is that the hammering timings of the four hammer assemblies are staggered, that is, the four hammer assemblies contact the mold 5 at different times, so that the mold 5 can generate multiple vibrations, thereby improving the compaction effect of the stripping box. At the same time, it can also avoid the problem of multiple hammer assemblies working simultaneously from different directions, resulting in the vibration being offset.

[0065] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A preparation method for controlling magnet properties through a molding process, characterized in that: A pre-pressing position (b), a powder adding position (c) and a slight lowering position (d) are sequentially arranged from the upper surface (a) to the lower surface of the mold, and a lower pressing head assembly is arranged above the upper surface (a) of the mold, and an upper pressing head assembly is arranged below the lower surface of the mold (5); The preparation method comprises the following steps: S1, the upper pressure head assembly moves upward to a preset powder adding position (c) on the mold (5), and then quantitatively adds sintered NdFeB powder to the mold (5); S2. After the sintered NdFeB powder is added, the upper pressure head assembly moves downward to a preset micro-drop position (d) on the mold (5); S3, the lower pressure head assembly moves downward to a preset pre-pressing position (b) on the mold to pre-press the sintered NdFeB powder in the mold (5); S4, after the pre-pressing of the sintered NdFeB powder is completed, the sintered NdFeB powder in the mold (5) is subjected to magnetization and orientation operation; S5, after the magnetization and orientation operation is completed, the upper pressure head assembly and the lower pressure head assembly move synchronously toward the middle of the mold (5) to perform bidirectional pressure on the sintered NdFeB powder; S6. After the sintered NdFeB powder is pressed, demagnetization operation is performed; S7. After demagnetization is completed, the upper pressing head assembly and the lower pressing head assembly move upward synchronously to push the sintered NdFeB powder after pressing out of the mold (5).

2. The method for preparing a magnet by controlling its performance through a molding process according to claim 1, characterized in that: The pre-compression density of the sintered NdFeB powder is between 2.5 and 2.8, and the counter-compression density of the sintered NdFeB powder is between 3.9 and 4.

1.

3. The method for preparing a magnet by controlling its performance through a molding process according to claim 1, characterized in that: In the step S1, after the sintered NdFeB powder is added, a triangular fork is used to evenly insert it into the mold cavity four times.

4. The method for preparing a magnet by controlling its performance through a molding process according to claim 1, characterized in that: The upper pressure head assembly includes a lifting hydraulic rod (3) and an upper pressure plate (4), and the lower pressure head assembly includes a telescopic hydraulic rod (1) and a lower pressure plate (2). In step S2, when the upper pressure head assembly moves down to the slightly lowered position (d), a hammer assembly is provided on the upper pressure head assembly to tap and compact the sintered NdFeB powder in the mold (5).

5. The method for preparing a magnet by controlling its performance through a molding process according to claim 4, characterized in that: Four groups of hammer assemblies are evenly distributed on the outer circumference of the mold (5), and the hammer assemblies include symmetrically arranged light rods (8), one end of the light rod (8) is provided with an end plate (7), the other end of the light rod (8) is provided with a retaining ring (10), and the retaining ring (10) is arranged close to the jacking hydraulic rod (3), a slider (9) is provided on the light rod (8), a first spring (20) is provided between the slider (9) and the retaining plate (16) arranged on the outside, and the first spring (20) is sleeved on the light rod (8), a vertical plate (11) is provided on the slider (9), one end of the vertical plate (11) is fixed on the slider (9), and the other end of the vertical plate (11) is located on the outside of the middle and lower part of the mold (5), and the vertical plate (11) is provided on the slider (9). 1) is provided with a knocking block (13), the knocking block (13) is connected to the other end of the vertical plate (11), the vertical plate (11) is provided with at least one wedge block (12) at the lower end of the mold (5), the output rod of the jacking hydraulic rod (3) is provided with a mounting block (14), the middle part of the mounting block (14) is threadedly connected to the output rod of the jacking hydraulic rod (3), and the side of the mounting block (14) facing the wedge block (12) is provided with a baffle (16), one end of the baffle (16) is connected to the mounting block (14), the other end of the baffle (16) is arranged toward the wedge block (12), and the projections of the baffle (16) and the wedge block (12) in the vertical direction partially overlap.

6. The method for preparing a magnet by controlling its performance through a molding process according to claim 5, characterized in that: A groove (15) is provided on the side of the mounting block (14) on which the baffle (16) is arranged, a spacing is provided between the end of the groove (15) and the upper surface of the mounting block (14), a rotating shaft (17) is provided in one end of the groove (15) facing the upper surface of the mounting block (14), and one end of the baffle (16) is rotatably connected to the rotating shaft (17).

7. The method for preparing a magnet by controlling its performance through a molding process according to claim 6, characterized in that: A fixing plate (18) is provided on the upper surface of the mounting block (14), one end of the fixing plate (18) is fixedly connected to the mounting block (14), and a second spring (19) is provided on the other end of the fixing plate (18), and two ends of the second spring (19) are respectively fixed to the fixing plate (18) and the baffle (16).

8. The method for preparing a magnet by controlling its performance through a molding process according to claim 5, characterized in that: The knocking block (13) is detachably connected to the end of the vertical plate (11).

9. The method for preparing a magnet by controlling its performance through a molding process according to claim 5, characterized in that: The knocking block (13) is made of rubber.

10. The method for preparing a magnet by controlling its performance through a molding process according to claim 5, characterized in that: The wedge blocks (12) in the four groups of hammer assemblies are arranged at different heights.

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