A preparation process and preparation system based on silicon nitride ceramic bearing balls

Abstract

The invention discloses a kind of preparation technology and preparation system based on silicon nitride ceramic bearing ball, relate to silicon nitride ceramic bearing ball technical field, comprise the following steps: S1, raw material mixing: adopt wet ball milling to mix high-purity silicon nitride powder, sintering aid and toughening agent to obtain compound A;S2, dry pressing molding: compound A is extruded, so that compound A forms a blank;S3, gas pressure sintering: under nitrogen atmosphere, blank is rapidly heated to 1800 DEG C, heat preservation 15 35min, then heat preservation more than 8 hours after being cooled to 1600 DEG C, to suppress grain growth, obtain fine grain structure. The present invention can effectively improve the density distribution inside silicon nitride ceramic bearing ball, by density uniform so that silicon nitride ceramic bearing ball is more stable when rotating at high speed, reduces imbalance phenomenon, greatly improves the stability of bearing when rotating at high speed.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon nitride ceramic bearing balls, and in particular to a preparation process and a preparation system based on silicon nitride ceramic bearing balls. Background Art

[0002] Silicon nitride ceramic bearing balls are high-performance bearing components made of silicon nitride. They have the characteristics of high hardness, high wear resistance, high temperature resistance, and corrosion resistance. At present, during the preparation, high-purity, uniform-sized silicon nitride ceramic powder is used, and extrusion molding is performed using a forming mold to ensure the dimensional accuracy and uniformity of the product. High-temperature and high-pressure sintering technology is used to form high-density composite silicon nitride ball bearings.

[0003] The current silicon nitride ceramic bearing ball preparation process faces the following problems: due to the uneven particle size distribution of the raw materials, the gaps between small particles may not be effectively filled by large particles, and a large number of pores are likely to remain during the sintering process, resulting in insufficient density of the ceramic balls after sintering, which will seriously affect the mechanical properties of the silicon nitride ceramic bearing balls, resulting in a decrease in their hardness and wear resistance, and imbalance problems during high-speed rotation. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation process and preparation system based on silicon nitride ceramic bearing balls to solve the deficiencies in the above-mentioned prior art.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a preparation process based on silicon nitride ceramic bearing balls, comprising the following steps:

[0006] S1, raw material mixing: high-purity silicon nitride powder, sintering aid and toughening agent are mixed by wet ball milling to obtain mixture A;

[0007] S2, dry pressing: extruding the mixture A to form a green billet;

[0008] S3, gas pressure sintering: In a nitrogen atmosphere, the green billet is rapidly heated to 1800°C, kept at this temperature for 15-35 minutes, then cooled to 1600°C and kept at this temperature for more than 8 hours to inhibit grain growth and obtain a fine-grained structure;

[0009] S4, precision machining: use diamond grinding wheel for rough grinding, and then use chemical mechanical polishing or magnetorheological polishing for fine polishing to make the surface roughness Ra ≤ 0.01μm.

[0010] Preferably, the sintering aid adopts a Y2O3-MgO system, and its addition ratio is 5-10wt%.

[0011] Preferably, in S2, the required forming pressure of the green billet is 200-300 MPa.

[0012] Preferably, the toughening agent is silicon carbide whisker, and the addition ratio thereof is 2-5 wt.%.

[0013] A preparation system based on silicon nitride ceramic bearing balls, comprising:

[0014] Stand;

[0015] The mold assembly includes a material feeding frame, a chute, and a forming block. A plurality of the chute are respectively provided on the upper and lower bottom surfaces of the material feeding frame. The forming block is slidably connected to the chute. A forming cavity is provided on the forming block. A pair of the forming cavities are spliced ​​to form a first semicircular cavity. The mold assembly has a first position and a second position.

[0016] A sliding block is slidably connected to the vertical frame, and the material placement frame is rotatably connected to the sliding block;

[0017] a first elastic member, wherein the first elastic member applies an upward thrust to the sliding block;

[0018] The pressure assembly includes a fixed plate and a punch, wherein the punch is fixedly mounted on the fixed plate, and a second semicircular cavity is formed at the lower portion of the punch. The first semicircular cavity and the second semicircular cavity can be combined to form a complete spherical cavity.

[0019] The power unit is used to drive the mold assembly to move from the first position to the second position. During this stroke, the pressure assembly moves downward under the drive of the power unit, the punch is inserted into the first semicircular cavity, and the mold assembly moves to the second position under the action of pressure. The mixture A in the cavity is squeezed by the punch to form a blank;

[0020] After the power unit moves upward, the unloading part, under the elastic force of the first elastic member, the mold assembly will reset from the second position to the first position. During this stroke, the unloading part passively drives the mold assembly to rotate so that the blank on the bottom surface of the material placement frame is separated.

[0021] Preferably, guide grooves are provided on both sides of the material placement frame, and guide pillars are rotatably connected to both sides of the forming block, and the guide pillars are rollingly connected in the guide grooves.

[0022] Preferably, a central shaft is provided on the material placing frame, and the central shaft is rotatably connected to the sliding block.

[0023] Preferably, the unloading part includes a flipping assembly and a trigger assembly, the flipping assembly includes a force arm and a rotating roller, the middle part of the force arm is fixedly installed on the end of the central axis, and a pair of rotating rollers are rotatably connected to the two ends of the force arm respectively, the trigger assembly includes a trigger block, a second elastic member, and an auxiliary plate, the trigger block is slidably connected to the auxiliary plate, and the second elastic member applies a thrust to the trigger block toward the direction of the flipping assembly.

[0024] Preferably, the trigger block is provided with an inclined surface at one end close to the flip assembly. When the mold assembly moves from the second position to the first position, the rotating roller abuts against the inclined surface, which hinders the upward movement of the force arm, so that the force arm drives the material loading frame to rotate.

[0025] Preferably, it includes a first positioning axis and a second positioning axis, the first positioning axis is installed at the lower part of the stand, the second positioning axis is installed at the upper part of the stand, and the sliding block and the center axis are both provided with through holes that are compatible with the first positioning axis and the second positioning axis.

[0026] In the above technical solution, the present invention provides a preparation process based on silicon nitride ceramic bearing balls, which can effectively improve the density distribution inside the silicon nitride ceramic bearing balls. The uniform density makes the silicon nitride ceramic bearing balls more stable during high-speed rotation, reduces the imbalance phenomenon, and greatly improves the stability of the bearings during high-speed rotation; and the silicon carbide whiskers play a connecting role inside the silicon nitride ceramic bearing balls, which can greatly increase the internal grain connection, further increase the stability of the silicon nitride ceramic bearing balls under high-speed conditions, and reduce the risk of breakage of the silicon nitride ceramic bearing balls. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0028] Figure 1 This is a schematic diagram of the overall structure of a preparation process and preparation system based on silicon nitride ceramic bearing balls according to the present invention;

[0029] Figure 2 This is a structural schematic diagram of a discharge portion of a mold assembly in a preparation process and system for silicon nitride ceramic bearing balls according to the present invention when the mold assembly is reset from the second position to the first position;

[0030] Figure 3 This is an appendix to the preparation process and preparation system based on silicon nitride ceramic bearing balls of the present invention. Figure 2 The schematic diagram of the structure after enlarging A in the middle;

[0031] Figure 4 This is a structural schematic diagram of a mold assembly in a first position of a preparation process and preparation system for silicon nitride ceramic bearing balls according to the present invention;

[0032] Figure 5 This is a structural schematic diagram of a mold assembly in a second position of a preparation process and preparation system for silicon nitride ceramic bearing balls according to the present invention;

[0033] Figure 6 This is an appendix to the preparation process and preparation system based on silicon nitride ceramic bearing balls of the present invention. Figure 5 The schematic diagram of the structure after enlarging point B in the middle;

[0034] Figure 7 A cross-sectional view of a mold assembly of a preparation process and preparation system for silicon nitride ceramic bearing balls according to the present invention;

[0035] Figure 8 A schematic cross-sectional view of a mold assembly of a preparation process and preparation system for silicon nitride ceramic bearing balls according to the present invention;

[0036] Figure 9 This is an appendix to the preparation process and preparation system based on silicon nitride ceramic bearing balls of the present invention. Figure 8 The schematic diagram of the structure after enlarging at C in the middle;

[0037] Figure 10 This is a schematic diagram of the material placement frame structure of a preparation process and preparation system based on silicon nitride ceramic bearing balls of the present invention;

[0038] Figure 11 This is an appendix to the preparation process and preparation system based on silicon nitride ceramic bearing balls of the present invention. Figure 10 Schematic diagram of the structure after enlarging point D in the middle.

[0039] Explanation of the accompanying drawings: 1. Material receiving part; 2. Stand; 3. Sliding block; 4. Mold assembly; 41. Material placing frame; 42. Slide groove; 421. Forming block; 422. Forming cavity; 43. Guide column; 44. Guide groove; 5. Center axis; 51. First positioning axis; 52. Second positioning axis; 6. Flipping assembly; 61. Force arm; 62. Rotating roller; 7. Trigger assembly; 71. Trigger block; 72. Second elastic member; 73. Auxiliary plate; 8. Pressure assembly; 82. Fixed disk; 83. Punch; 9. First elastic member; 10. Power unit. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] See also Figure 1-11The present invention provides a method for preparing silicon nitride ceramic bearing balls, comprising the following steps:

[0042] S1, raw material mixing: high-purity silicon nitride powder, sintering aid and toughening agent are mixed by wet ball milling to obtain mixture A;

[0043] S2, dry pressing: extruding the mixture A to form a green billet;

[0044] S3, gas pressure sintering: In a nitrogen atmosphere, the green billet is rapidly heated to 1800°C, kept at this temperature for 15-35 minutes, then cooled to 1600°C and kept at this temperature for more than 8 hours to inhibit grain growth and obtain a fine-grained structure;

[0045] S4, precision machining: use diamond grinding wheel for rough grinding, and then use chemical mechanical polishing or magnetorheological polishing for fine polishing to make the surface roughness Ra ≤ 0.01μm.

[0046] The sintering aid adopts Y2O3-MgO system, and its addition ratio is 5-10wt%.

[0047] In S2, the required forming pressure of the green billet is 200-300 MPa.

[0048] The toughening agent is silicon carbide whisker, and the addition ratio thereof is 2-5 wt.%.

[0049] In the present invention, the Y2O3-MgO system refers to a material containing yttrium oxide (Y2O3) and magnesium oxide (MgO) as additives or primary components. During the sintering process of silicon nitride ceramics, the Y2O3-MgO system forms a liquid phase at high temperatures. This liquid phase fills the gaps between silicon nitride particles, promoting particle rearrangement and diffusion, thereby lowering the sintering temperature and increasing the density of the sintered body. For example, when gas-pressure sintering silicon nitride ceramics, adding an appropriate amount of Y2O3 and MgO can reduce the sintering temperature from over 1900°C without additives to around 1700-1850°C. Yttrium oxide (Y2O3) and magnesium oxide (MgO) combined with silicon carbide whiskers can play a bridging and pull-out role in the silicon nitride ceramic matrix due to their unique microstructure. When the ceramic matrix is ​​subjected to external force and cracks are generated, the silicon carbide whiskers can span the two ends of the crack like a bridge to prevent further crack expansion. At the same time, during the crack propagation process, the whiskers will be pulled out of the silicon nitride particles. This process consumes a lot of energy, thereby effectively improving the toughness of the ceramic ball and reducing the risk of its rupture under high load.

[0050] The above process can effectively improve the density distribution inside the silicon nitride ceramic bearing ball. The uniform density makes the silicon nitride ceramic bearing ball more stable during high-speed rotation, reduces the imbalance phenomenon, and greatly improves the stability of the bearing during high-speed rotation. The silicon carbide whiskers act as a connection inside the silicon nitride ceramic bearing ball, which can greatly increase the internal grain connection, further increase the stability of the silicon nitride ceramic bearing ball at high speed, and reduce the risk of silicon nitride ceramic bearing ball breakage.

[0051] During the molding stage, mixed material A needs to be extruded to form a blank. After sintering, the blank becomes a silicon nitride ceramic bearing ball blank. During the blank molding process, the pressure is between 200 and 300 MPa. Although a release agent is applied to the cavity, the blank is still difficult to remove from the mold. Therefore, we propose a preparation system that can effectively reduce the blank removal time and improve production efficiency.

[0052] A preparation system based on silicon nitride ceramic bearing balls includes a forming device, wherein the forming device includes:

[0053] Stand 2;

[0054] The mold assembly 4 includes a material loading frame 41, a chute 42, and a forming block 421. A plurality of the chute 42 are respectively provided on the upper and lower bottom surfaces of the material loading frame 41. The forming block 421 is slidably connected to the chute 42. A forming cavity 422 is provided on the forming block 421. A pair of the forming cavities 422 are spliced ​​to form a first semicircular cavity. The mold assembly 4 has a first position and a second position.

[0055] Sliding block 3, the sliding block 3 is slidably connected to the stand 2, and the material loading frame 41 is rotatably connected to the sliding block 3;

[0056] a first elastic member 9 , which applies an upward thrust to the sliding block 3 ;

[0057] The pressure assembly 8 includes a fixed plate 82 and a punch 83. The punch 83 is fixedly mounted on the fixed plate 82. A second semicircular cavity is formed at the lower portion of the punch 83. The first semicircular cavity and the second semicircular cavity can be combined to form a complete spherical cavity.

[0058] The power unit 10 is used to drive the mold assembly 4 from the first position to the second position. During this stroke, the pressure assembly 8 moves downward under the drive of the power unit 10, and the punch 83 is inserted into the first semicircular cavity. The mold assembly 4 moves to the second position under the action of pressure, and the mixture A in the cavity is squeezed by the punch 83 to form a blank.

[0059] In the unloading part, after the power unit 10 moves upward, the mold assembly 4 will be reset from the second position to the first position under the elastic force of the first elastic member 9. During this stroke, the unloading part passively drives the mold assembly 4 to rotate so that the blank on the bottom surface of the loading frame 41 is separated.

[0060] In the embodiment of the present invention, after the mixed material A is added to the material frame 41, it is scraped by a scraper to evenly fill the first semicircular cavity formed by the molding cavity 422. After the power unit 10 is started, the pressure assembly 8 is driven downward, and the punch 83 corresponds to the first semicircular cavity. The punch 83 is inserted into the first semicircular cavity, and a second semicircular cavity is opened at the bottom of the punch 83. At this time, as shown in the attached Figure 9 As shown in , a complete spherical cavity is formed by splicing the first semicircular cavity and the second semicircular cavity together, so that the mixture A is formed into a sphere under the extrusion of the punch 83 and the forming block 421 to complete the forming of the green billet;

[0061] During the downward movement of the power unit 10, the sliding block 3 will overcome the elastic force of the first elastic member 9 and move downward synchronously. At this time, the first elastic member 9 is compressed until the mold assembly 4 moves to the second position. In the second position, the mold assembly 4 reaches the lowest point. At this time, the mixture A has formed a green billet under the action of pressure.

[0062] After the blank is formed, the power unit 10 retracts quickly and the punch 83 will also detach from the mold assembly 4. After losing the pressure of the power unit 10, the first elastic member 9 will drive the sliding block 3 to move upward, and when the sliding block 3 moves upward, it will simultaneously drive the mold assembly 4 to move upward, and the mold assembly 4 will be reset from the second position to the first position. During this process, the unloading part will passively drive the mold assembly 4 to rotate. After the mold assembly 4 is flipped 180 degrees, under the action of gravity, the forming block 421 will slide and unfold along the slide groove 42, so that the blank formed will detach from the mold assembly 4. The removal of the material is convenient and quick. When it is reset to the first position, the mixture A can be added immediately, the production continuity is good, and the production efficiency is significantly improved.

[0063] Furthermore, due to the large extrusion force of the blank, even after being flipped 180 degrees, a portion of the forming block 421 is difficult to unfold solely by relying on gravity. Therefore, in the present invention, the rebound of the first elastic member 9 will drive the sliding block 3 to collide with the upper part of the stand 2. The vibration generated during the collision can greatly promote the expansion of the forming block 421, greatly reducing the jamming of the blank. The vibration can also shake off the residual mixed material A on the surface of the forming block 421, so as to reduce the risk of the forming block 421 failing to close.

[0064] In the embodiments of the present invention, please refer to Figure 10-11Guide grooves 44 are provided on both sides of the material placement frame 41 , and guide pillars 43 are rotatably connected to both sides of the forming block 421 , and the guide pillars 43 are rollingly connected in the guide grooves 44 .

[0065] The guide post 43 is connected in a rolling manner in the guide groove 44, and the guide post 43 is connected in rotation to the forming block 421. Therefore, the forming block 421 will be restricted by the guide groove 44 during its displacement, and the slope of the guide groove 44 is consistent with the slope of the chute 42. In this way, under the restriction of the guide groove 44, the forming block 421 can only slide and unfold along the inclined surface of the chute 42. After unfolding, as shown in the attached Figure 9 As shown, the forming cavities 422 are separated from each other, thereby separating the green blank.

[0066] In the embodiment of the present invention, a central shaft 5 is provided on the material placement frame 41 , and the central shaft 5 is rotatably connected to the sliding block 3 .

[0067] The sliding block 3 can be displaced vertically along the stand 2. Therefore, when the sliding block 3 is displaced, the material loading frame 41 can be synchronously driven to move in the vertical direction. Moreover, since the central axis 5 is rotatably connected to the sliding block 3, the material loading frame 41 can also rotate synchronously to realize the flipping of the forming block 421 and complete the unloading of the blank.

[0068] In the embodiments of the present invention, please refer to Figure 2-3 The unloading part includes a flipping assembly 6 and a trigger assembly 7. The flipping assembly 6 includes a force arm 61 and a rotating roller 62. The middle part of the force arm 61 is fixedly installed at the end of the central axis 5. A pair of rotating rollers 62 are rotatably connected to the two ends of the force arm 61. The trigger assembly 7 includes a trigger block 71, a second elastic member 72, and an auxiliary plate 73. The trigger block 71 is slidably connected to the auxiliary plate 73. The second elastic member 72 applies a thrust to the trigger block 71 toward the direction of the flipping assembly 6.

[0069] After the extrusion of the blank is completed, the power unit 10 will move up quickly, thereby driving the punch 83 to quickly disengage from the forming block 421. Without the extrusion of the punch 83, the first elastic member 9 will rebound, and the first elastic member 9 will drive the sliding block 3 to move upward. The upward displacement of the sliding block 3 will drive the mold assembly 4 to move up synchronously, and the force arm 61 is installed on the central axis 5. During the upward movement of the mold assembly 4, the power arm 61 will inevitably move up synchronously. The force arm 61 remains in a horizontal state at this time. During the upward movement, the rotating roller 6 at the upper end of the force arm 61 2 will be blocked by the trigger block 71. Under the obstruction of the trigger block 71, the lever arm 61 will rotate clockwise. When the lever arm 61 rotates, it will synchronously drive the central shaft 5 to rotate. When the central shaft 5 rotates, it will synchronously drive the mold assembly 4 to rotate, thereby realizing the flipping of the mold assembly 4. Under the restriction of the trigger block 71, the rotation angle of the lever arm 61 is at least greater than 90 degrees. When the lever arm 61 is separated from the trigger block 71, it continues to rotate under the action of inertia. In this way, the mold assembly 4 is finally balanced by relying on its own gravity.

[0070] In an embodiment of the present invention, the trigger block 71 is provided with an inclined surface at one end close to the flip assembly 6. When the mold assembly 4 is reset from the second position to the first position, the rotating roller 62 abuts against the inclined surface, and the inclined surface hinders the upward movement of the lever arm 61, so that the lever arm 61 drives the material frame 41 to rotate.

[0071] The upper and lower surfaces of the trigger block 71 are both set as inclined surfaces, so that during the downward movement of the mold assembly 4, it is necessary to ensure that the mold assembly 4 does not rotate. Through the inclined surface setting of the trigger block 71, during the downward movement of the mold assembly 4, since the punch 83 is inserted into the forming block 421, and a protrusion is set at the lower part of the fixed plate 82, the protrusion contacts the surface of the forming block 421. Therefore, the mold assembly 4 cannot rotate during the downward movement. The force arm 61 will apply a greater pressure to the trigger block 71 during the downward movement, so that the trigger block 71 overcomes the elastic force of the second elastic member 72 and retracts, so that the trigger block 71 gives way to the force arm 61, so as to ensure that the mold assembly 4 moves downward smoothly.

[0072] Furthermore, in this process, a two-stage variable pressure is realized during the blank forming process. When moving from the first position to the trigger block 71, the mold assembly 4 needs to overcome the resistance brought by the trigger block 71 and the rebound force of the first elastic member 9 when moving downward. After passing the trigger block 71, the mold assembly 4 only needs to overcome the rebound force of the first elastic member 9. In this way, the pressure changes to gradually increase, then briefly decrease, and then gradually increase, realizing two-stage pressurization, thereby improving the blank forming quality.

[0073] In the embodiments of the present invention, please refer to Figure 5-6, including a first positioning shaft 51 and a second positioning shaft 52, the first positioning shaft 51 is installed at the lower part of the stand 2, and the second positioning shaft 52 is installed at the upper part of the stand 2, and the sliding block 3 and the center shaft 5 are both provided with through holes that are compatible with the first positioning shaft 51 and the second positioning shaft 52.

[0074] The center shaft 5 can be positioned by the first positioning shaft 51 and the second positioning shaft 52 to ensure that the material frame 41 is in a horizontal state when it is in the first position and the second position, thereby ensuring the stability of the blank during extrusion molding. A sufficient disconnection section is reserved between the first positioning shaft 51 and the second positioning shaft 52, and the disconnection section ensures that the center shaft 5 can rotate smoothly to ensure smooth unloading.

[0075] The receiving part 1 includes a material receiving part 1, which is used to receive the blanks. The receiving part 1 can be set as a mesh conveyor belt. The received blanks are directly transported to the next process flow, and the mixed material A can directly pass through the mesh conveyor belt into the receiving box below for centralized collection. Alternatively, the mesh conveyor belt can be not set up to directly collect the mixed material and the blanks, and then they can be sorted manually.

[0076] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A preparation system based on silicon nitride ceramic bearing balls, characterized in that: include: Stand (2); A mold assembly (4), the mold assembly (4) includes a material loading frame (41), a chute (42), and a forming block (421), wherein a plurality of the chute (42) are respectively provided at the upper and lower bottom surfaces of the material loading frame (41), the forming block (421) is slidably connected to the chute (42), a forming cavity (422) is provided on the forming block (421), a pair of the forming cavities (422) are spliced ​​together to form a first semicircular cavity, and the mold assembly (4) has a first position and a second position; A sliding block (3), the sliding block (3) is slidably connected to the stand (2), and the material placement frame (41) is rotatably connected to the sliding block (3); a first elastic member (9), wherein the first elastic member (9) applies an upward thrust to the sliding block (3); A pressure assembly (8) includes a fixed plate (82) and a punch (83), wherein the punch (83) is fixedly mounted on the fixed plate (82), and a second semicircular cavity is formed at the lower portion of the punch (83), wherein the first semicircular cavity and the second semicircular cavity can be combined to form a complete spherical cavity; A power unit (10) is used to drive the mold assembly (4) to move from a first position to a second position. During this stroke, the pressure assembly (8) moves downward under the drive of the power unit (10), the punch (83) is inserted into the first semicircular cavity, and the mold assembly (4) moves to the second position under the action of pressure, and the mixed material A in the cavity is squeezed by the punch (83) to form a blank; The unloading part, after the power unit (10) moves upward, under the elastic force of the first elastic member (9), the mold assembly (4) is reset from the second position to the first position. During this stroke, the unloading part passively drives the mold assembly (4) to rotate so that the blank on the bottom surface of the material placement frame (41) is separated; Guide grooves (44) are provided on both sides of the material placement frame (41), and guide pillars (43) are rotatably connected to both sides of the forming block (421), and the guide pillars (43) are rollingly connected in the guide grooves (44); The unloading portion includes a flip assembly (6) and a trigger assembly (7), the flip assembly (6) includes a force arm (61) and a rotating roller (62), the middle portion of the force arm (61) is fixedly mounted on the end of the central shaft (5), a pair of rotating rollers (62) are rotatably connected to the two ends of the force arm (61), and the trigger assembly (7) includes a trigger block (71), a second elastic member (72), and an auxiliary plate (73), the trigger block (71) is slidably connected to the auxiliary plate (73), and the second elastic member (72) applies a thrust to the trigger block (71) in the direction of the flip assembly (6); The trigger block (71) is provided with an inclined surface at one end close to the flip assembly (6). When the mold assembly (4) is reset from the second position to the first position, the rotating roller (62) contacts the inclined surface, and the inclined surface hinders the upward movement of the lever arm (61), so that the lever arm (61) drives the material frame (41) to rotate. A first positioning shaft (51) and a second positioning shaft (52), wherein the first positioning shaft (51) is mounted on the lower portion of the stand (2), and the second positioning shaft (52) is mounted on the upper portion of the stand (2), and the sliding block (3) and the central shaft (5) are both provided with through holes adapted to the first positioning shaft (51) and the second positioning shaft (52).

2. A preparation system based on silicon nitride ceramic bearing balls according to claim 1, characterized in that: The material placement frame (41) is provided with a central shaft (5), and the central shaft (5) is rotatably connected to the sliding block (3).

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