Mim-based metal powder forming injection molding equipment and injection molding process

Abstract

The application relates to the technical field of metal powder injection molding, and discloses a metal powder forming injection molding equipment and an injection molding process based on MIM, wherein the metal powder forming injection molding equipment based on MIM comprises an injection unit, the injection unit comprises an injection cylinder, one end of the injection cylinder is provided with an injection nozzle, an injection cavity one, a centrifugal cavity and an injection cavity two are sequentially arranged in the injection cylinder, a rotating injection rod is arranged in the injection cavity two, the injection rod extends into the injection cavity one, a spiral conveying piece is arranged on the rod wall of the injection rod, a pair of annular rings are arranged on the outer wall of the injection rod, the positions of the pair of annular rings correspond to the two side walls of the centrifugal cavity respectively, the outer diameter of the annular ring is the same as the diameter of the injection cavity one, an annular centrifugal shell is rotationally arranged in the centrifugal cavity, and an annular vacuum cavity is arranged on the outside of the centrifugal cavity. The device forms centrifugal acceleration in the centrifugal cavity, so that the gas bubbles in the melt gather to the top wall of the centrifugal shell; the gas bubbles are extracted through the top wall micropores and the outside vacuum cavity, and the gas hole defects are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal powder injection molding, and in particular to a metal powder forming injection molding equipment based on MIM and an injection molding process. BACKGROUND

[0002] The metal powder forming injection molding equipment is a special machine for metal injection molding (MIM), which combines powder metallurgy and plastic injection molding technology and can efficiently produce complex-shaped and high-precision metal parts. The core process includes mixing micron-sized metal powder and organic binder into uniform feedstock, injecting into a precision mold through a high-temperature and high-pressure injection molding machine, then removing the binder through a debinding furnace, and densifying the metal particles in a high-temperature sintering furnace to finally form a metal product close to full density.

[0003] In the patent with the patent number CN109693350A, a screw assembly, a barrel and an injection molding machine for metal powder melt injection are disclosed. The screw assembly includes a screw and a flow dividing component. The flow dividing component is detachably arranged at the end of the screw. The flow dividing component includes a flow dividing main body, main flow dividing wings and auxiliary flow dividing wings. The main flow dividing wings are distributed on the flow dividing main body along the axial circumference of the flow dividing main body. The auxiliary flow dividing wings are arranged on the flow dividing main body corresponding to the main flow dividing wings and located on the side of the main flow dividing wings close to the screw.

[0004] The existing technology has the following defects:

[0005] Firstly, due to the large difference in melting temperature of different metal powders, the traditional feeding screw adopts a fixed temperature gradient heating mode, which is difficult to achieve precise gradient temperature control, resulting in premature melting of low melting point metals and high melting point metals still in solid state, and significant asynchronous melting process. This non-uniform melting state is easy to form air gaps in the material liquid, and a large number of small bubbles are generated in the mixture under the shearing and extruding action of the screw. Secondly, the conventional screw structure lacks a dynamic degassing mechanism. Under the centrifugal effect of high-speed rotation, the low-density bubbles are forced to migrate to the outer diameter area of the screw and continuously accumulate, forming a stable bubble retention layer. With the continuous operation of the equipment, these bubbles are merged to form macroscopic pores due to flow channel pressure fluctuations, and directly injected into the mold cavity along with the melt, resulting in internal defects such as porosity and holes in the molded parts. In addition, the existing equipment relies on offline sampling for quality control, which cannot intervene in the real-time generated bubbles during injection, resulting in small defects in the products. SUMMARY

[0006] In view of the above problems existing in the prior art, a metal powder forming injection molding equipment based on MIM and an injection molding process are proposed.

[0007] The application provides a metal powder forming injection molding equipment based on MIM, which aims to reduce the bubble content before metal powder injection and improve product quality.

[0008] The technical scheme of the application is as follows: a metal powder forming injection molding equipment based on MIM, comprising a base and further comprising:

[0009] A hydraulic unit is arranged on the base.

[0010] A mold is connected with the hydraulic unit and the mold is controlled to open and close through the hydraulic unit.

[0011] An injection unit is slidably arranged on the base and used for injecting metal powder slurry into the mold.

[0012] The injection unit comprises an injection cylinder, one end of the injection cylinder is provided with an injection nozzle, and the injection cylinder is sequentially provided with an injection cavity one, a centrifugal cavity and an injection cavity two; a rotating injection rod is arranged in the injection cavity two and extends into the injection cavity one; a helical conveying piece is arranged on the rod wall of the injection rod; a pair of annular rings are arranged on the outer wall of the injection rod, and the positions of the annular rings correspond to the two side walls of the centrifugal cavity respectively; the outer diameter of the annular ring is the same as the diameter of the injection cavity one; an annular centrifugal shell is rotatably arranged in the centrifugal cavity; meshing teeth one are arranged on the two side walls of the centrifugal shell; meshing teeth two are arranged on the outer edges of the pair of annular rings; the meshing teeth one and the meshing teeth two are meshed; a plurality of micropores are arranged on the top wall of the centrifugal shell; and a plurality of material holes are arranged on each annular ring.

[0013] Further, the injection unit further comprises a slide arranged on the base and a rack arranged on the slide; the injection cylinder is connected with the rack; a pushing module is arranged on the rack and connected with the injection rod; a feeding hole is arranged at the right end of the injection cylinder; a feeding pipe is arranged at the feeding hole; and a cartridge is connected with the upper opening of the feeding pipe.

[0014] Further, a rotating spoiler rod is arranged in the injection rod, the rotating direction of the spoiler rod is opposite to that of the injection rod, and the part of the spoiler rod located in the centrifugal cavity is provided with an annular spoiler block; a plurality of helical grooves are annularly arranged on the surface of the spoiler block; a plurality of helical openings are annularly arranged on the part of the injection rod corresponding to the spoiler block, and the helical openings are connected with the helical grooves.

[0015] Further, the diameter of the injection rod gradually increases in the direction of the injection nozzle, and the pitch of the helical conveying piece gradually decreases in the direction of the injection nozzle.

[0016] Further, a heating device is arranged on the outer wall of the injection cylinder.

[0017] Further, an injection head is arranged at the left end of the injection rod, and the shape of the injection head is matched with the inner cavity of the injection nozzle.

[0018] Further, the outer wall of the injection cylinder is provided with a vacuum pipe, the vacuum pipe is communicated with the vacuum cavity, and the vacuum pipe is connected with a vacuum pump.

[0019] Further, the material passing holes are arranged in a spiral shape, and the spiral directions of the material passing holes on the pair of annular rings are opposite.

[0020] Further, the application also provides a metal powder forming injection molding process based on MIM, comprising the following steps:

[0021] Step one: selecting metal powder with small particle size (5-20 mu m), high sphericity and good fluidity, then preparing a thermoplastic binder, and preliminarily mixing the metal powder and the binder at a volume ratio of 50-65%;

[0022] Step two: heating the metal powder and the binder to 150-200 DEG C in a banbury mixer to realize sufficient mixing through mechanical shearing force, forming a homogeneous feedstock, after mixing, the feedstock is cooled, crushed into granules, and then injected into a barrel;

[0023] Step three: designing a mold according to the shape of the part and preheating to 100-150 DEG C, controlling the pressure (50-200 MPa), temperature (150-200 DEG C) and pressure maintaining time during injection molding, injecting the feedstock particles into the mold to form a "green body", and reserving 15-25% of the sintering shrinkage of the mold to compensate for the subsequent deformation;

[0024] Step four: removing the organic matter in the green body by solvent degreasing or thermal degreasing, and strictly controlling the degreasing rate;

[0025] Step five: in a vacuum or protective atmosphere, the part after degreasing is heated to near the melting point of the metal, and the powder particles are diffused and combined after being heated for 1-4 hours to realize densification, and then the furnace is cooled to reduce residual stress.

[0026] The beneficial effects of the application are:

[0027] 1. By setting the injection unit, the structure design realizes multiple advantages through coaxial transmission centrifugal degassing and vacuum cooperative degassing: when the injection rod rotates, the meshing teeth two of the outer wall annular ring and the meshing teeth one of the centrifugal shell sidewall dynamically mesh, so that the centrifugal shell synchronously rotates at high speed, forming centrifugal acceleration in the centrifugal cavity, forcing the gas bubbles with lower density in the melt to gather to the top wall of the centrifugal shell; the top wall micropore is communicated with the outside vacuum cavity, and the gas bubbles are efficiently extracted from the system to avoid forming pores in the injection mold. At the same time, the material passing holes on the annular ring ensure the continuous conveying of the melt from the injection cavity one to the centrifugal cavity, and the compression effect of the spiral conveying piece maintains the density of the melt, combined with the coaxial design of the centrifugal shell self-rotation power, which not only simplifies the transmission structure, but also improves the degassing efficiency, and is suitable for defect-free batch production of high-precision complex parts.

[0028] 2. The core advantage of the structure design is that the melt is super-efficiently degassed by setting the spoiler rod, reversing the shear flow field and guiding the composite flow channel: when the spoiler rod rotates counterclockwise, the surface spiral groove and the injection rod spiral port form an interpenetrating dynamic flow channel, which generates high-strength reverse vortex in the melt, and directly peels off the bubbles attached to the injection rod wall surface; at the same time, the spiral groove converts the tangential kinetic energy of the melt into radial momentum, and the centrifugal acceleration pushes the bubbles to the top wall of the centrifugal shell. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a perspective view of the MIM-based metal powder forming injection molding equipment of the application;

[0030] Figure 2 It is a perspective view of the injection unit in the MIM-based metal powder forming injection molding equipment of the application;

[0031] Figure 3 It is a perspective view of the injection cylinder in the MIM-based metal powder forming injection molding equipment of the application;

[0032] Figure 4 It is a left view of the injection cylinder in the MIM-based metal powder forming injection molding equipment of the application;

[0033] Figure 5 It is a perspective view of the Figure 4 A-A section view of the application;

[0034] Figure 6 It is a perspective view of the internal structure of the injection cylinder in the MIM-based metal powder forming injection molding equipment of the application;

[0035] Figure 7 It is a half-section perspective view of the injection cylinder in the MIM-based metal powder forming injection molding equipment of the application;

[0036] Figure 8 It is a left view of the Figure 6 of the application;

[0037] Figure 9 It is a perspective view of the Figure 6 hidden centrifugal shell of the application;

[0038] Figure 10 It is a perspective view of the spoiler block in the MIM-based metal powder forming injection molding equipment of the application.

[0039] In the figure:

[0040] 1, base; 2, hydraulic unit; 3, mold; 4, injection unit; 5, injection cylinder; 6, injection nozzle; 7, injection cavity one; 8, centrifugal cavity; 9, injection cavity two; 10, injection rod; 11, spiral conveying piece; 12, circular ring; 13, centrifugal shell; 14, meshing tooth one; 15, meshing tooth two; 16, vacuum cavity; 17, material hole; 18, slide; 19, rack; 20, push module; 21, feed hole; 22, feed pipe; 23, barrel; 24, spoiler rod; 25, spoiler block; 26, spiral groove; 27, spiral port; 28, heating device; 29, injection head; 30, vacuum pipe. DETAILED DESCRIPTION

[0041] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0042] Example 1, reference Figures 1-10 For the first embodiment of the present application, a metal powder forming injection molding equipment based on MIM is provided, including a base 1, further comprising: a hydraulic unit 2 arranged on the base 1; a mold 3 connected with the hydraulic unit 2, the mold 3 is controlled to open and close by the hydraulic unit 2; an injection unit 4 is slidingly arranged on the base 1, used for injecting metal powder melt into the mold 3; the injection unit 4 includes an injection cylinder 5, one end of the injection cylinder 5 is provided with an injection nozzle 6, the injection cylinder 5 is sequentially provided with an injection cavity one 7, a centrifugal cavity 8 and an injection cavity two 9, a rotating injection rod 10 is arranged in the injection cavity two 9, the injection rod 10 extends into the injection cavity one 7, a spiral conveying piece 11 is arranged on the rod wall of the injection rod 10, a pair of circular rings 12 are arranged on the outer wall of the injection rod 10, the positions of the pair of circular rings 12 correspond to the two side walls of the centrifugal cavity 8 respectively, the outer diameter of the circular ring 12 is the same as the diameter of the injection cavity one 7, an annular centrifugal shell 13 is rotatably arranged in the centrifugal cavity 8, meshing tooth one 14 is arranged on the two side walls of the centrifugal shell 13, meshing tooth two 15 is arranged on the outer edge of the pair of circular rings 12, the meshing tooth one 14 is engaged with the meshing tooth two 15, a plurality of micropores are arranged on the top wall of the centrifugal shell 13, an annular vacuum cavity 16 is arranged outside the centrifugal cavity 8, a plurality of material holes 17 are arranged on each circular ring 12.

[0043] In the embodiment, the cavity formed by the centrifugal shell 13 and the pair of annular rings 12 is used to generate centrifugal force when the injection rod 10 rotates, so that the bubbles are moved to the micropores on the top wall of the centrifugal shell 13 under the action of the centrifugal force, and finally are sucked out by the negative pressure in the vacuum cavity 16. Meanwhile, the centrifugal shell 13 and the pair of annular rings 12 are connected by the engagement tooth one 14 and the engagement tooth two 15. When the injection rod 10 moves horizontally for injection, the pair of annular rings 12 is separated from the centrifugal shell 13. After the injection rod 10 is reset, the centrifugal shell 13 and the pair of annular rings 12 are re-engaged. The engagement tooth one 14 and the engagement tooth two 15 are smoothly processed on both sides, so that the engagement tooth one 14 and the engagement tooth two 15 can be aligned during the re-engagement process. The inner wall of the micropore is coated with a liquid-repellent coating (such as polytetrafluoroethylene) to prevent the pores from being blocked by residual melt.

[0044] It is worth noting that in the dynamic centrifugal-vacuum collaborative degassing system of metal powder injection molding, the bubbles will move to the outer periphery of the screw (i.e. the outer wall of the centrifugal cavity 8) under the action of centrifugal force. The following is a detailed explanation: when the screw rotates at high speed, the centrifugal force direction is radially outward (away from the rotation axis). The density of the metal melt is much higher than that of the bubble, which causes the melt to be thrown to the outer periphery under the action of centrifugal force, while the bubble receives less centrifugal force due to its low density. The melt forms a strong outflow (radially outward) under the push of the screw conveying piece 11, and the bubble is carried to the outer periphery area by the high-speed flowing melt. Although the bubble itself has a tendency to move towards the axis due to its low density, the outflow speed of the melt is much faster than the reverse movement of the bubble, and finally the bubble is "wrapped" near the outer wall of the centrifugal cavity 8.

[0045] Referring to Figures 1-2 The injection unit 4 further comprises a slide 18 arranged on the base 1, a rack 19 arranged on the slide 18, the injection cylinder 5 being connected with the rack 19, and a pushing module 20 arranged on the rack 19 and connected with the injection rod 10. The right end of the injection cylinder 5 is provided with a feeding hole 21, and a feeding pipe 22 is arranged at the feeding hole 21. The feeding pipe 22 is connected with a cartridge 23 at the upper opening.

[0046] In the embodiment, a driving motor is arranged in the rack 19, which is used to drive the rotation of the injection rod 10 to convey the melt metal powder. The pushing module 20 is an electric push rod, which is connected with the injection rod 10 and used to control the horizontal movement of the injection rod 10 to achieve the injection effect. The cartridge 23 is used to carry the mixture of metal powder and adhesive. The slide 18 is used to translate the entire injection unit 4.

[0047] Referring to Figures 5-10, the injection rod 10 is provided with a rotating spoiler rod 24, the rotating direction of the spoiler rod 24 is opposite to the injection rod 10, the spoiler rod 24 is located in the part of the centrifugal cavity 8 and is provided with an annular spoiler block 25, the surface of the spoiler block 25 is annularly arranged with a plurality of spiral grooves 26, and the part of the injection rod 10 corresponding to the spoiler block 25 is annularly arranged with a plurality of spiral openings 27, and the spiral openings 27 are communicated with the spiral grooves 26.

[0048] In the embodiment, the spoiler rod 24 is coaxially nested in the inside of the injection rod 10, the axis of the spoiler rod 24 is coincident with the injection rod 10, and the annular spoiler block 25 extends out in the section of the centrifugal cavity 8. The surface of the spoiler block 25 is annularly arranged with six groups of spiral grooves 26 at an equal angle of 60°, and six groups of spiral openings 27 (oblique angle through the wall) are formed in the corresponding positions of the injection rod 10. When the injection rod 10 rotates clockwise, the spoiler rod 24 nested in the injection rod 10 rotates counterclockwise through the gear set, and the two form a bidirectional reverse shear flow field. The specific action mechanism includes:

[0049] Laminar flow breaking and bubble peeling, when the spoiler block 25 rotates at high speed in the reverse direction, the edge of the spiral groove 26 generates a reverse shear force on the melt, directly destroys the laminar boundary layer formed by the spiral conveying piece 11 of the injection rod 10, and makes the bubbles attached to the inner wall of the injection rod 10 be forced to peel off; the flow guiding effect of the spiral groove 26 converts the tangential flow of the melt into radial motion, cooperates with the centrifugal acceleration generated by the rotation of the centrifugal cavity 8, and pushes the bubbles to the top wall of the centrifugal shell 13. The bubbles enriched on the top wall are continuously subjected to the negative pressure of the vacuum cavity 16 and are extracted at high speed through the micropores.

[0050] With reference to Figure 5 The diameter of the injection rod 10 gradually increases towards the injection nozzle 6, and the pitch of the spiral conveying piece 11 gradually decreases towards the injection nozzle 6.

[0051] With reference to Figure 3 The outer wall of the injection cylinder 5 is provided with a heating device 28.

[0052] In the embodiment, the variable-diameter injection rod 10 cooperates with the variable-pitch conveying piece to realize a multi-stage gradient melting screw design,

[0053] The injection cylinder 5 is divided into a preheating section, a gradient melting section, a homogenization section and a dynamic exhaust section, each section is independently temperature-controlled, and electromagnetic induction heating is adopted, so that different metal powders are sequentially melted according to the melting point, and bubble generation caused by local overheating or unmelted particles is avoided.

[0054] Preheating section: low-temperature zone (slightly lower than the melting temperature of the low-melting-point metal), pre-compaction and uniform preheating of the mixed powder.

[0055] Gradient melting section: setting a stepped temperature rising zone, sequentially matching the melting points of different metal powders, so that high and low melting point powders are melted in stages.

[0056] Homogenization section: a constant temperature and high pressure zone, where the molten liquid is forcibly mixed by high-shear spiral blades to eliminate component segregation.

[0057] The pitch and depth of the spiral conveyor 11 gradually decrease from the feed end to the extrusion end, which is achieved by changing the compression ratio:

[0058] Wide front groove: Reduces feed flow resistance and prevents unmelted powder from accumulating and creating air gaps.

[0059] Narrow groove at the rear end: enhances shear force and breaks up bubbles generated during the melting process.

[0060] Reference Figure 5 The left end of the injection rod 10 is provided with an injection head 29, the shape of which fits the inner cavity of the injection nozzle 6.

[0061] In this embodiment, the inner cavity of the injection head 29 and the injection nozzle 6 are used to extrude the molten metal powder into the injection cylinder 5 and inject it into the mold 3 to form a blank.

[0062] Reference Figure 5 The outer wall of the syringe 5 is provided with a vacuum tube 30, which is connected to the vacuum chamber 16 and a vacuum pump.

[0063] In this embodiment, a vacuum pump is used for vacuum suction and exhaust: the vacuum negative pressure at the micropores on the outer wall draws away the gas bubbles, and the clean melt is extruded from the end of the cavity into the mold 3.

[0064] The vacuum pump is used for self-cleaning circulation: when the machine stops, the vacuum pump switches to pulse backflushing mode, and high-pressure gas backflushes the micropores to prevent residual blockage.

[0065] Reference Figure 9 The feed hole 17 is set in a spiral shape, and the spiral directions of the feed holes 17 located on a pair of rings 12 are opposite.

[0066] In this embodiment, the spiral direction of the feed hole 17 on the right side is the same as that of the spiral conveyor plate 11, while the spiral direction of the feed hole 17 on the left side is opposite to that of the spiral conveyor plate 11, so that...

[0067] The working principle of this embodiment:

[0068] When the metal powder slurry is pushed into injection chamber 7 by the spiral conveyor 11, the melt continues to flow forward under the rotational drive of injection rod 10, and then enters the annular centrifugal shell 13 through the inlet of centrifugal chamber 8. At this time, a pair of rings 12 on injection rod 10 dynamically engage with meshing teeth 14 on the side wall of centrifugal shell 13 through meshing teeth 15, synchronously transmitting the rotational power of injection rod 10 to centrifugal shell 13, driving it to rotate at high speed at the same speed. Under the action of strong centrifugal force, low-density bubbles are thrown towards the top wall area of ​​centrifugal shell 13, while clean melt flows along the inner wall of centrifugal shell 13 into injection chamber 9. At the same time, the micropores on the top wall of centrifugal shell 13 are connected to the outer vacuum chamber 16, and the vacuum pump maintains the negative pressure in vacuum chamber 16, continuously extracting the bubbles accumulated on the top wall of centrifugal shell 13 from the system.

[0069] Simultaneously, the counter-rotating baffle rod 24 and injection rod 10 form a dynamic shear coupling effect: when the melt flows through the centrifugal cavity 8, the array of spiral grooves 26 on the surface of the annular baffle block 25 of the baffle rod 24 generates a high-intensity reverse vortex as it rotates in the opposite direction, directly impacting the laminar boundary layer formed by the spiral conveyor plate 11 of the injection rod 10, forcibly peeling off the bubbles attached to the outer wall of the injection rod 10; at the same time, the annular spiral opening 27 opened at the corresponding position of the injection rod 10 and the spiral grooves 26 of the baffle block 25 are interconnected, so that the melt is driven by centrifugal force and Bernoulli effect when passing through the spiral opening 27, forming a radial-tangential composite turbulence, which continuously guides the dispersed bubbles to the top wall area of ​​the centrifugal shell 13. The degassed melt enters the injection cavity 9 from the bottom of the centrifugal shell 13, and is finally extruded into the mold cavity 3 under high pressure through the injection nozzle 6.

[0070] Example 2, refer to Figures 1-10 The second embodiment of the present invention provides: a metal powder molding injection molding process based on MIM, employing a metal powder molding injection molding equipment based on MIM, including the following steps:

[0071] Step 1: Select metal powder with fine particle size (20μm), high sphericity and good flowability, and then prepare a thermoplastic binder (paraffin). Mix the metal powder and binder together at a volume ratio of 65%.

[0072] Step 2: Heat the metal powder and binder to 150°C in an internal mixer and mix them thoroughly by mechanical shearing force to form a homogeneous feed. After mixing, the feed is cooled, crushed and processed into granules, and then injected into the feed cylinder 23.

[0073] Step 3: Design mold 3 according to the shape of the part and preheat it to 100°C. Control the pressure (200MPa), temperature (200°C) and holding time during injection molding. Inject the feed particles into mold 3 to form a "green blank". Mold 3 needs to reserve 15% sintering shrinkage to compensate for subsequent deformation.

[0074] Step 4: Remove organic matter from the green body by solvent degreasing or thermal degreasing, strictly controlling the degreasing rate;

[0075] Step 5: In a vacuum atmosphere, heat the degreased parts to near the metal melting point and hold for 3 hours to allow the powder particles to diffuse and bond, achieving densification. Then, cool with the furnace to reduce residual stress.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A metal powder molding injection equipment based on MIM, comprising a base (1), characterized in that, Also includes: The hydraulic unit (2) is mounted on the base (1); The mold (3) is connected to the hydraulic unit (2), and the opening and closing of the mold (3) is controlled by the hydraulic unit (2); The injection unit (4) is slidably mounted on the base (1) and is used to inject metal powder slurry into the mold (3); The injection unit (4) includes an injection cylinder (5), with an injection nozzle (6) at one end. The injection cylinder (5) contains an injection chamber one (7), a centrifuge chamber (8), and an injection chamber two (9) arranged sequentially. A rotating injection rod (10) is located within the injection chamber two (9), extending into the injection chamber one (7). A spiral conveying plate (11) is provided on the rod wall of the injection rod (10), and a pair of rings (12) are provided on the outer wall of the injection rod (10). The positions of the pair of rings (12) correspond to the two points of the centrifuge chamber (8). The outer diameter of the ring (12) on the side wall is the same as the diameter of the injection chamber (7). A ring-shaped centrifugal shell (13) is rotatably arranged inside the centrifugal chamber (8). There are meshing teeth (14) on both side walls of the centrifugal shell (13). There are meshing teeth (25) on the outer edge of a pair of rings (12). The meshing teeth (14) mesh with the meshing teeth (25). There are micropores on the top wall of the centrifugal shell (13). There is a ring-shaped vacuum chamber (16) on the outside of the centrifugal chamber (8). There are multiple material passage holes (17) on each ring (12). The injection unit (4) also includes a slide (18) on the base (1) and a frame (19) on the slide (18). The injection cylinder (5) is connected to the frame (19). A push module (20) is provided on the frame (19). The push module (20) is connected to the injection rod (10). A feed hole (21) is provided at the right end of the injection cylinder (5). A feed pipe (22) is provided at the feed hole (21). A material cylinder (23) is connected to the upper end of the feed pipe (22). The injection rod (10) is provided with a rotating baffle rod (24). The rotation direction of the baffle rod (24) is opposite to that of the injection rod (10). The part of the baffle rod (24) located in the centrifuge chamber (8) is provided with an annular baffle block (25). The surface of the baffle block (25) has a ring array of multiple spiral grooves (26). The part of the injection rod (10) corresponding to the baffle block (25) has a ring array of multiple spiral openings (27). The spiral openings (27) are connected to the spiral grooves (26).

2. The metal powder molding and injection molding equipment based on MIM according to claim 1, characterized in that: The diameter of the injection rod (10) gradually increases towards the injection nozzle (6), and the pitch of the spiral conveyor plate (11) gradually decreases towards the injection nozzle (6).

3. The metal powder molding and injection molding equipment based on MIM according to claim 1, characterized in that: A heating device (28) is provided on the outer wall of the injection cylinder (5).

4. The MIM-based metal powder molding injection equipment according to claim 1, characterized in that: The left end of the injection rod (10) is provided with an injection head (29), the shape of which fits the inner cavity of the injection nozzle (6).

5. The MIM-based metal powder molding injection equipment according to claim 1, characterized in that: The outer wall of the injection cylinder (5) is provided with a vacuum tube (30), which is connected to the vacuum chamber (16) and a vacuum pump.

6. The MIM-based metal powder molding injection equipment according to claim 1, characterized in that: The feed hole (17) is set in a spiral shape, and the feed holes (17) located on a pair of rings (12) have opposite spiral directions.

7. A metal powder molding injection process based on MIM, employing the metal powder molding injection equipment based on MIM as described in claim 1, characterized in that, Includes the following steps: Step 1: Select metal powder with a particle size of 5-20μm, high sphericity and good flowability, and then prepare a thermoplastic binder. Mix the metal powder and binder in a preliminary manner at a volume ratio of 50-65%. Step 2: Heat the metal powder and binder to 150-200℃ in a mixer and mix them thoroughly by mechanical shearing to form a homogeneous feed. After mixing, the feed is cooled, crushed and processed into granules, and then injected into the feed cylinder (23). Step 3: Design mold (3) according to the shape of the part and preheat it to 100-150℃. Control the pressure of 50-200 MPa, temperature of 150-200℃ and holding time during injection molding. Inject the feed particles into mold (3) to form a "green blank". Mold (3) reserves 15-25% sintering shrinkage to compensate for subsequent deformation. Step 4: Remove organic matter from the green body by solvent degreasing or thermal degreasing, strictly controlling the degreasing rate; Step 5: In a vacuum or protective atmosphere, heat the degreased parts to near the metal melting point and hold for 1-4 hours to allow the powder particles to diffuse and bond, achieving densification. Then, cool with the furnace to reduce residual stress.

Images