A twin-screw assembly for powder injection molding

Abstract

This invention relates to the field of syringe technology, specifically to a twin-screw assembly for powder injection molding, characterized by: a housing; a mixing chamber extending along its length within the housing; a first screw and a second screw rotatably disposed within the mixing chamber; the first screw and the second screw arranged side-by-side; both the first screw and the second screw extending along their length; a first sealing chamber and a second sealing chamber within the housing; and an extrusion port at one end of the housing. This invention, through the counter-clockwise alternating motion of the first and second pistons, combined with the alternating operation of the first and second sealing chambers to form a pressurizing unit, creates a continuous and uninterrupted secondary pressurization and conveying structure for the material. This ensures that the pressure at the extrusion port is consistently maintained within the high-pressure range required for the powder injection molding process, avoiding sudden pressure rises and falls and effectively reducing pressure fluctuations.

Description

Technical Field

[0001] This invention relates to the field of syringe technology, and more specifically to a twin-screw assembly for powder injection molding. Background Technology

[0002] Powder injection molding, a precision molding technology combining powder metallurgy and plastic injection molding, is widely used in machinery manufacturing, electronics and communications, automotive, aerospace and other fields due to its advantages such as near-net-shape forming, high molding precision, and ability to produce complex structural parts. As industries increasingly demand higher performance from molded parts, high-solids powder injection molding systems have become the mainstream, requiring a higher proportion of powder raw materials in the molding compound, resulting in molded materials exhibiting high viscosity characteristics.

[0003] In existing technologies, material conveying and mixing in powder injection molding often employs interlocking twin-screw assemblies. These assemblies require necessary assembly clearances between the screws and between the screws and the barrel shell to meet the screw's rotational movement requirements. However, in high-solids, high-viscosity material systems, these assembly clearances easily form axial leakage channels, causing material backflow or bypass flow in the metering and conveying section. This severely weakens the twin-screw's ability to build pressure axially, making it impossible to form a stable high-pressure zone at the discharge end.

[0004] Pressure fluctuations at the discharge end not only significantly reduce material conveying efficiency but also directly affect the stability of subsequent injection molding processes, leading to problems such as uneven density, dimensional accuracy deviations, internal porosity, and surface defects in the molded preform, thus reducing the yield of finished products. At the same time, in order to compensate for insufficient pressure build-up capacity, existing processes often need to reduce material viscosity by adjusting the raw material ratio and increasing the binder content. This not only increases the material cost of raw material preparation but also increases the difficulty of subsequent debinding and sintering processes, further affecting the final performance of the parts.

[0005] In summary, existing interlocking twin-screw assemblies are no longer suitable for the process requirements of high-solids powder injection molding. There is an urgent need for a twin-screw assembly structure that can effectively improve the pressure build-up capacity at the discharge end, reduce pressure fluctuations, and ensure stable material delivery. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned shortcomings in the prior art by providing a twin-screw assembly for powder injection molding.

[0007] The objective of this invention is achieved through the following technical solution: a twin-screw assembly for powder injection molding, comprising a housing; a mixing chamber extending along the length direction within the housing; a first screw and a second screw rotatably disposed within the mixing chamber; the first screw and the second screw arranged side by side; both the first screw and the second screw extending along the length direction; a first sealing cavity and a second sealing cavity within the housing; and an extrusion port at one end of the housing. One end of the first sealing cavity is provided with a first discharge check valve; one end of the first sealing cavity is connected to the extrusion port through the first discharge check valve; the first discharge check valve opens in the direction of the extrusion port; a first piston is provided in the first sealing cavity for sealing and sliding; the first piston is provided with a first feed check valve; the other end of the first sealing cavity is connected to one end of the mixing cavity through the first feed check valve; the first feed check valve opens in the direction of the first sealing cavity; One end of the second sealing cavity is provided with a second discharge check valve; one end of the second sealing cavity is connected to the extrusion port through the second discharge check valve; the second discharge check valve opens in the direction of the extrusion port; a second piston is provided in the second sealing cavity for sealing and sliding; the second piston is provided with a second feed check valve; the other end of the second sealing cavity is connected to one end of the mixing cavity through the second feed check valve; the second feed check valve opens in the direction of the second sealing cavity.

[0008] The present invention is further configured such that the direction of movement of the first piston is opposite to the direction of movement of the second piston.

[0009] The present invention is further configured such that a first rod is provided at the end of the first piston away from the extrusion port; the first rod extends along the length direction; a first driving cavity is provided at one end of the first screw extending along the length direction; and the first rod is movably disposed in the first driving cavity.

[0010] The present invention is further configured such that the outer wall of the first rod is provided with a first reciprocating spiral groove; the inner wall of the first driving cavity is rotatably provided with a first key; and the first key is movably disposed in the first reciprocating spiral groove.

[0011] The present invention is further configured such that a second rod is provided at the end of the second piston away from the extrusion port; the second rod extends along the length direction; a second driving cavity is provided at one end of the second screw, extending along the length direction; and the second rod is movably disposed in the second driving cavity.

[0012] The present invention is further configured such that the outer wall of the second rod is provided with a second reciprocating spiral groove; the inner wall of the second driving cavity is rotatably provided with a second key; the second key is movably disposed in the second reciprocating spiral groove.

[0013] The present invention is further configured such that the housing is provided with a first feed port and a second feed port communicating with the mixing chamber.

[0014] The present invention is further configured such that the extrusion port has a trumpet-shaped structure.

[0015] The present invention is further configured such that the other end of the housing is provided with an end cap; the end cap is rotatably provided with a first gear and a second gear; the other end of the first screw protrudes out of the housing opening and is connected to the first gear; the other end of the second screw protrudes out of the housing opening and is connected to the second gear.

[0016] The present invention is further configured such that the end cover is provided with a motor; the output end of the motor is provided with a transmission gear; the first gear and the second gear respectively mesh with the two sides of the transmission gear.

[0017] The beneficial effects of the present invention are as follows: The present invention forms a continuous and uninterrupted secondary pressurization and conveying structure for materials by using the counter-clockwise alternating motion of the first piston and the second piston, in conjunction with the alternating working pressurization unit formed by the first sealing cavity and the second sealing cavity. This ensures that the pressure at the extrusion port is always kept stable within the high pressure range required by the powder injection molding process, avoiding the problem of sudden pressure rises and falls, and effectively reducing the pressure fluctuation range. Attached Figure Description

[0018] The invention will be further illustrated with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the invention. For those skilled in the art, other drawings can be obtained based on the following drawings without any creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a cross-sectional view of the present invention; Figure 3 yes Figure 2 A magnified view of part A in the middle; Figure 4 yes Figure 2 A magnified view of part B in the middle; The components are as follows: 1. Shell; 11. Mixing chamber; 12. Extrusion port; 13. First feed port; 14. Second feed port; 2. First screw; 21. First drive chamber; 22. First key; 3. Second screw; 31. Second drive chamber; 32. Second key; 4. First sealing chamber; 41. First discharge check valve; 42. First feed check valve; 5. First piston; 51. First rod; 52. First reciprocating spiral groove; 6. Second sealing chamber; 61. Second discharge check valve; 62. Second feed check valve; 7. Second piston; 71. Second rod; 72. Second reciprocating spiral groove; 8. End cap; 81. Motor; 82. Transmission gear; 83. First gear; 84. Second gear. Detailed Implementation

[0020] The present invention will be further described in conjunction with the following embodiments.

[0021] Depend on Figures 1 to 4 As can be seen, the twin-screw assembly for powder injection molding described in this embodiment includes a housing 1; a mixing chamber 11 extending along the length direction is provided inside the housing 1; a first screw 2 and a second screw 3 are rotatably arranged inside the mixing chamber 11; the first screw 2 and the second screw 3 are arranged side by side; both the first screw 2 and the second screw 3 extend along the length direction; a first sealing chamber 4 and a second sealing chamber 6 are provided inside the housing 1; and an extrusion port 12 is provided at one end of the housing 1. One end of the first sealing cavity 4 is provided with a first discharge check valve 41; one end of the first sealing cavity 4 is connected to the extrusion port 12 through the first discharge check valve 41; the first discharge check valve 41 opens toward the extrusion port 12; a first piston 5 is provided in the first sealing cavity 4 for sealing and sliding; the first piston 5 is provided with a first feed check valve 42; the other end of the first sealing cavity 4 is connected to one end of the mixing cavity 11 through the first feed check valve 42; the first feed check valve 42 opens toward the first sealing cavity 4. One end of the second sealing cavity 6 is provided with a second discharge check valve 61; one end of the second sealing cavity 6 is connected to the extrusion port 12 through the second discharge check valve 61; the second discharge check valve 61 opens toward the extrusion port 12; a second piston 7 is provided in the second sealing cavity 6 for sealing and sliding; the second piston 7 is provided with a second feed check valve 62; the other end of the second sealing cavity 6 is connected to one end of the mixing cavity 11 through the second feed check valve 62; the second feed check valve 62 opens toward the second sealing cavity 6.

[0022] Specifically, in the twin-screw assembly for powder injection molding described in this embodiment, during use, the material is first placed into the mixing chamber 11. As the first screw 2 and the second screw 3 rotate, the material is pushed towards the extrusion port 12. When the first piston 5 moves towards the mixing chamber 11, the volume of the first sealing chamber 4 gradually increases, and the pressure in the first sealing chamber 4 decreases, allowing the material to enter the first sealing chamber 4 from the mixing chamber 11 through the first feed check valve 42. When the first piston 5 moves towards the extrusion port 12, the volume of the first sealing chamber 4 gradually decreases, and the pressure in the first sealing chamber 4 increases. This allows the material to enter the extrusion port 12 from the first sealed chamber 4 through the first discharge check valve 41 for discharge. Similarly, when the second piston 7 moves toward the mixing chamber 11, the volume of the second sealed chamber 6 gradually increases and the pressure of the second sealed chamber 6 decreases, allowing the material to enter the second sealed chamber 6 from the mixing chamber 11 through the second feed check valve 62. When the second piston 7 moves toward the extrusion port 12, the volume of the second sealed chamber 6 gradually decreases and the pressure of the second sealed chamber 6 increases, allowing the material to enter the extrusion port 12 from the second sealed chamber 6 through the second discharge check valve 61 for discharge.

[0023] In this embodiment, the rotation of the first screw 2 and the second screw 3 in the mixing chamber 11 achieves preliminary mixing and axial conveying of the material, supplying it for the subsequent pressurization process. The first sealing chamber 4 and the second sealing chamber 6 are respectively equipped with a suitable first piston 5 and a second piston 7. The first sealing chamber 4 is correspondingly equipped with a first feed check valve 42 and a first discharge check valve 41, and the second sealing chamber 6 is correspondingly equipped with a second feed check valve 62 and a second discharge check valve 61. The directional conduction characteristic of the check valves ensures that the material flows only in one direction along the mixing chamber 11-first sealing chamber 4-extrusion port 12 and the mixing chamber 11-second sealing chamber 6-extrusion port 12, preventing material backflow. At the same time, the first piston 5 and the second piston 7 slide in the sealing chamber 4 and the second sealing chamber 6 respectively. The secondary compression and pressurization of the material can be achieved through the volume change of the first sealing chamber 4 and the second sealing chamber 6, which makes up for the insufficient pressure build-up caused by gap leakage in traditional twin screws and meets the process requirements of high-solids powder injection molding for high-pressure conveying.

[0024] This embodiment describes a twin-screw assembly for powder injection molding, in which the movement direction of the first piston 5 is opposite to that of the second piston 7. The first piston 5 and the second piston 7 maintain opposite axial reciprocating motions, creating an alternating working process between the first sealing cavity 4 and the second sealing cavity 6. That is, when the first piston 5 retracts to fill the first sealing cavity 4 with material, the second piston 7 advances to complete the material pressurization and conveying in the second sealing cavity 6, and vice versa. This achieves uninterrupted secondary pressurization and conveying of the material, ensuring that the pressure at the extrusion port 12 remains within the required process range, significantly reducing pressure fluctuations, avoiding uneven discharge and material interruption, and improving the stability of high-solids-content powder material conveying.

[0025] This embodiment describes a twin-screw assembly for powder injection molding. The first piston 5 has a first rod 51 at its end furthest from the extrusion port 12. The first rod 51 extends along its length. One end of the first screw 2 has a first driving cavity 21 extending along its length. The first rod 51 is movably disposed within the first driving cavity 21. This embodiment integrates the first piston 5 and the first rod 51, with the first rod 51 movably fitted within the first driving cavity 21 of the first screw 2. The rotational motion of the first screw 2 provides the power for the reciprocating motion of the first piston 5 driven by the first rod 51. This eliminates the need for additional hydraulic or pneumatic drive components for the first piston 5, simplifying the overall equipment structure, reducing potential failure points, and ensuring that the movement of the first piston 5 is synchronized with the feeding action of the first screw 2, guaranteeing coordination and synchronization of the processes.

[0026] This embodiment describes a twin-screw assembly for powder injection molding. The outer wall of the first screw body 51 is provided with a first reciprocating helical groove 52; the inner wall of the first drive cavity 21 is rotatably provided with a first key 22; the first key 22 is movably disposed within the first reciprocating helical groove 52. Specifically, when the first screw 2 rotates, the first key 22 on the inner wall of the first drive cavity 21 and the first reciprocating helical groove 52 on the outer wall of the first screw body 51 form a guiding engagement, precisely converting the rotational motion of the first screw 2 into the axial reciprocating linear motion of the first screw body 51, thereby driving the first piston 5 to perform periodic filling and pressing actions within the first sealed cavity 4. This mechanical transmission method has high transmission efficiency and precise stroke control, ensuring consistent stroke of the first piston 5 in each reciprocating motion, and ensuring stable pressurization effect in the first sealed cavity 4.

[0027] This embodiment describes a twin-screw assembly for powder injection molding. The second piston 7 has a second rod 71 at its end furthest from the extrusion port 12. The second rod 71 extends along its length. One end of the second screw 3 has a second drive chamber 31 extending along its length. The second rod 71 is movably disposed within the second drive chamber 31. This embodiment integrates the second piston 7 and the second rod 71, with the second rod 71 movably fitted within the second drive chamber 31 of the second screw 3. The rotational motion of the second screw 3 provides the power for the reciprocating motion of the second piston 7 driven by the second rod 71. This eliminates the need for separate hydraulic or pneumatic drive components for the second piston 7, simplifying the overall equipment structure, reducing potential failure points, and ensuring that the movement of the second piston 7 is synchronized with the feeding action of the second screw 3, guaranteeing coordination and synchronization of the processes.

[0028] This embodiment describes a twin-screw assembly for powder injection molding. The outer wall of the second rod 71 is provided with a second reciprocating spiral groove 72; the inner wall of the second drive cavity 31 is rotatably provided with a second key 32; the second key 32 is movably disposed within the second reciprocating spiral groove 72. Specifically, when the second screw 3 rotates, the second key 32 on the inner wall of the second drive cavity 31 and the second reciprocating spiral groove 72 on the outer wall of the second rod 71 form a guiding engagement, precisely converting the rotational motion of the second screw 3 into the axial reciprocating linear motion of the second rod 71, thereby driving the second piston 7 to perform periodic filling and pressing actions within the second sealing cavity 6. This mechanical transmission method has high transmission efficiency and precise stroke control, ensuring consistent stroke of the second piston 7 in each reciprocation, and ensuring stable pressurization effect in the second sealing cavity 6.

[0029] This embodiment describes a twin-screw assembly for powder injection molding. The housing 1 is provided with a first feed port 13 and a second feed port 14 communicating with a mixing chamber 11. Both the first feed port 13 and the second feed port 14 on the housing 1 are connected to the mixing chamber 11, enabling multi-point synchronous feeding of materials into the mixing chamber 11. This effectively increases the material feed throughput and meets the large-volume conveying requirements of high-solids-content powder materials. Simultaneously, multi-point feeding allows for more uniform material distribution within the mixing chamber 11. Combined with the mixing and conveying actions of the first screw 2 and the second screw 3, this avoids localized material accumulation and clumping within the mixing chamber 11, ensuring uniform material mixing and reducing subsequent pressurization and conveying failures caused by uneven material mixing.

[0030] This embodiment describes a twin-screw assembly for powder injection molding, wherein the extrusion port 12 has a trumpet-shaped structure. The trumpet-shaped extrusion port 12 has one end with a larger radius connected to the discharge side of the first sealing cavity 4 and the second sealing cavity 6, and the other end with a smaller radius is the discharge end. This structure can effectively buffer the high-pressure material discharged through the first discharge check valve 41 and the second discharge check valve 61, significantly reducing the flow resistance and pressure loss of high-viscosity, high-solids-content powder materials at the discharge end, and preventing material from stagnating and clogging at the extrusion port 12.

[0031] This embodiment describes a twin-screw assembly for powder injection molding. The housing 1 has an end cap 8 at one end. The end cap 8 is rotatably equipped with a first gear 83 and a second gear 84. The other end of the first screw 2 protrudes from the opening of the housing 1 and connects to the first gear 83. The other end of the second screw 3 protrudes from the opening of the housing 1 and connects to the second gear 84. The end cap 8 provides stable rotational support for the first gear 83 and the second gear 84. The first screw 2 is fixedly connected to the first gear 83, and the second screw 3 is fixedly connected to the second gear 84, thereby enabling the first gear 83 and the second gear 84 to drive the first screw 2 and the second screw 3 to rotate, respectively.

[0032] This embodiment describes a twin-screw assembly for powder injection molding. The end cap 8 is equipped with a motor 81; the output end of the motor 81 is equipped with a transmission gear 82; the first gear 83 and the second gear 84 mesh with the two sides of the transmission gear 82, respectively. The motor 81 provides a unified and stable power source for the first screw 2 and the second screw 3. The transmission gear 82 at the output end of the motor 81 meshes with the first gear 83 and the second gear 84, respectively, achieving synchronous rotation of the twin screws driven by a single power source. This effectively simplifies the power drive system of the equipment and reduces the use of power components. Simultaneously, the single power source ensures that the rotation speeds of the first gear 83 and the second gear 84 are completely consistent, further improving the synchronicity of the rotation of the first screw 2 and the second screw 3. This ensures that the first piston 5 and the second piston 7 achieve precise counter-rotating movements, making the entire pressurized conveying system more stable and reliable in operation.

[0033] Finally, 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 the scope of protection of the present invention. 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 essence and scope of the technical solutions of the present invention.

Claims

1. A twin-screw assembly for powder injection molding, characterized in that: The device includes a housing (1); the housing (1) has a mixing chamber (11) extending along its length; a first screw (2) and a second screw (3) are rotatably arranged in the mixing chamber (11); the first screw (2) and the second screw (3) are arranged side by side; both the first screw (2) and the second screw (3) extend along their length; the housing (1) has a first sealing chamber (4) and a second sealing chamber (6); one end of the housing (1) has an extrusion port (12); One end of the first sealing cavity (4) is provided with a first discharge check valve (41); one end of the first sealing cavity (4) is connected to the extrusion port (12) through the first discharge check valve (41); the first discharge check valve (41) opens in the direction of the extrusion port (12); a first piston (5) is provided in the first sealing cavity (4) for sealing and sliding; the first piston (5) is provided with a first feed check valve (42); the other end of the first sealing cavity (4) is connected to one end of the mixing cavity (11) through the first feed check valve (42); the first feed check valve (42) opens in the direction of the first sealing cavity (4); A second discharge check valve (61) is provided at one end of the second sealing cavity (6); one end of the second sealing cavity (6) is connected to the extrusion port (12) through the second discharge check valve (61); the second discharge check valve (61) opens towards the extrusion port (12); a second piston (7) is provided in the second sealing cavity (6) for sealing and sliding; the second piston (7) is provided with a second feed check valve (62); the other end of the second sealing cavity (6) is connected to one end of the mixing cavity (11) through the second feed check valve (62); the second feed check valve (62) opens towards the second sealing cavity (6); The direction of movement of the first piston (5) is opposite to the direction of movement of the second piston (7); The first piston (5) has a first rod (51) at one end away from the extrusion port (12); the first rod (51) extends along the length direction; the first screw (2) has a first drive cavity (21) at one end extending along the length direction; the first rod (51) is movably disposed in the first drive cavity (21); The outer wall of the first rod (51) is provided with a first reciprocating spiral groove (52); the inner wall of the first drive cavity (21) is rotatably provided with a first key (22); the first key (22) is movably disposed in the first reciprocating spiral groove (52); The second piston (7) has a second rod (71) at one end away from the extrusion port (12); the second rod (71) extends along the length direction; the second screw (3) has a second drive cavity (31) at one end extending along the length direction; the second rod (71) is movably disposed in the second drive cavity (31); The outer wall of the second rod (71) is provided with a second reciprocating spiral groove (72); the inner wall of the second drive cavity (31) is provided with a second key (32); the second key (32) is movably disposed in the second reciprocating spiral groove (72).

2. The twin-screw assembly for powder injection molding according to claim 1, characterized in that: The housing (1) is provided with a first feed port (13) and a second feed port (14) that are connected to the mixing chamber (11).

3. A twin-screw assembly for powder injection molding according to claim 1, characterized in that: The extrusion port (12) has a trumpet-shaped structure.

4. A twin-screw assembly for powder injection molding according to claim 1, characterized in that: The other end of the housing (1) is provided with an end cap (8); the end cap (8) is rotatably provided with a first gear (83) and a second gear (84); the other end of the first screw (2) protrudes out of the opening of the housing (1) and is connected to the first gear (83); the other end of the second screw (3) protrudes out of the opening of the housing (1) and is connected to the second gear (84).

5. A twin-screw assembly for powder injection molding according to claim 4, characterized in that: The end cap (8) is equipped with a motor (81); the output end of the motor (81) is equipped with a transmission gear (82); the first gear (83) and the second gear (84) respectively mesh with the two sides of the transmission gear (82).

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