Gas-assisted micro injection molding method

Abstract

The invention relates to the field of high polymer material forming and processing technologies, in particular to a gas-assisted micro injection molding device and method.The gas-assisted micro injection molding device comprises a base, and a mold assembly is arranged at the top of the base; the melt glue injection assembly is arranged at the top of the base; the mold assembly is communicated with the melt glue injection assembly through the runner; and the gas injection assembly for injecting gas into the runner to push the melt is arranged at the position, close to the runner, of the top of the base. The gas which does not react with the melt is introduced into the runner of the micro injection molding equipment, the gas can continuously provide stable pressure to push the melt to fill the cavity, the phenomenon of insufficient filling of the melt is improved, meanwhile, the gas pushes the melt in the runner into the cavity, the runner is hollow, materials are saved, and pressure and material loss are effectively reduced.

Description

Technical Field

[0001] This invention patent relates to the field of polymer material forming and processing technology, and particularly to a gas-assisted micro-injection molding device and method. Background Art

[0002] Micro-injection molding is a rapidly developing emerging technology in recent years. It is a manufacturing technology that can perform repeated batch production of complex and precise micro-structured plastic parts. Micro-injection molding can produce products with extremely small sizes, meeting the market's demand for miniaturized and precision products.

[0003] However, the current micro-injection molding technology still has the following problems: 1. Compared with traditional injection molding, the flow behavior of the melt during micro-injection molding is more complex. The melt viscosity near the mold wall is 50% - 80% higher than that of the material body, and the sharp increase in viscosity easily leads to insufficient filling of the mold cavity.

[0004] 2. During micro-injection molding, the product volume is small. When injecting through the runner, the proportion of the raw material in the runner in the total injection weight is relatively large, up to 90% at most. And the raw material in the runner is generally not recyclable, resulting in a large amount of material waste. However, in order to save materials and reduce the size of the runner, it is easy to cause local overheating of the melt in the main runner due to viscous dissipation, ultimately leading to short-shot and material degradation phenomena.

[0005] Therefore, in order to solve the above technical problems, this application proposes a gas-assisted micro-injection molding method. Summary of the Invention

[0006] In order to overcome the disadvantages that the flow behavior of the melt during the existing micro-injection molding process is complex and prone to filling imbalance, and the runner volume of micro-injection molding is large, and the raw material in the runner is generally not recyclable, resulting in a large amount of material waste, the present invention provides a gas-assisted micro-injection molding device.

[0007] The technical solution of the present invention is: A gas-assisted micro-injection molding device, comprising: a base and a mold assembly. The mold assembly is provided on the top of the base. A melt injection assembly is provided on the top of the base. The mold assembly is communicated with the melt injection assembly through a hollow runner; an air injection assembly, the air injection assembly is provided on the top of the base; a guiding assembly, a guiding assembly is provided at one end of the runner close to the melt injection assembly.

[0008] The gas injection assembly includes: a fixed shell, a fixed shell is provided on the top of the base through a bracket, two air chambers are provided on the top of the fixed shell, and an injection pipe is provided on the top of the air chamber; a gas needle, a gas needle is connected to the side wall of the flow channel, and the gas needle is connected to the end of the injection pipe with a short distance; an electric control rotating column, an electric control rotating column with a plurality of air holes opened at the top is rotatably provided inside the fixed shell, and pistons are slidably provided in the air holes; a limiting inclined plate, a limiting inclined plate is provided in the middle of the bracket, and the bottom of the piston is connected to the limiting inclined plate in a limiting manner.

[0009] Furthermore, the orientation assembly includes: a fixed frame, a plurality of fixed frames are provided inside the flow channel near the position of the melt injection assembly; a blocking frame, a blocking frame is provided between the fixed frames, and the legs of the blocking frame slide inside the fixed frames; a first elastic member, a first elastic member is provided between the blocking frame and the fixed frames; a wedge-shaped block, a chute is opened at a position on the inner side wall of the flow channel near the port of the fixed frame, a wedge-shaped block is slidably provided in the chute, and an inclined groove is provided on one side of the leg of the blocking frame in contact with the inner wall of the flow channel, and the inclined groove is in contact and cooperation with the wedge-shaped block; a second elastic member, a second elastic member is used between the wedge-shaped block and the chute.

[0010] Furthermore, it further includes: an exhaust pipe, an exhaust pipe is connected to the injection pipe connected to the gas needle at one end near the gas needle; a connecting pipe, a connecting pipe is provided on the exhaust pipe, and the connecting pipe is connected to an external waste gas recovery device; a fixed seat, a fixed seat is provided on the top of the fixed shell; an electric push rod, an electric push rod is provided on the upper part of the fixed seat; a blocking pipe, a blocking pipe is slidably provided inside the injection pipe; a connecting frame, a connecting frame is connected to one end of the blocking pipe near the electric push rod, and the connecting frame slidably penetrates the side wall of the injection pipe and is connected to the telescopic rod of the electric push rod.

[0011] Furthermore, the gas needle is arranged on the flow channel in an inclined direction towards the mold.

[0012] Furthermore, the total length of the injection pipe is between 8 cm and 12 cm.

[0013] Furthermore, a gas-assisted micro-injection molding method includes the following steps: S1. Preheat the mold, close the mold, and inject the melt. S2. When the melt injection volume is sufficient to fill the cavity of the mold assembly, stop injecting the melt; open the gas injection assembly on the flow channel and inject gas through the gas injection assembly. S3. Control the gas to drive the melt in the flow channel into the cavity of the mold assembly to complete filling and pressure holding. S4. After continuously holding the pressure for a period of time, discharge the gas to relieve the pressure, and open the mold to take out the part.

[0014] The present invention has the following advantages: In the present invention, after injecting a certain amount of melt into the runner, a gas that does not react with the melt is injected into the middle and rear ends of the runner, and the gas is used to push the melt into the mold. In this way, even when using a large-volume runner, a large amount of melt can be avoided from remaining in the runner during injection molding. Moreover, the gas is injected into the runner by the rapid rotation of the electric rotating column, and the air pressure in the runner is increased to exert a squeezing and pushing effect on the melt, so that under normal injection pressure, a high-pressure pushing effect on the melt is generated by the air pressure. The gas can continuously provide a stable pressure to push the melt to fill the cavity, improving the phenomenon of insufficient filling due to the large viscosity of the melt. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a three-dimensional structural schematic diagram of the present invention.

[0016] Figure 2 is a partial three-dimensional structural schematic diagram of the present invention.

[0017] Figure 3 is a three-dimensional structural schematic diagram of the gas injection assembly of the present invention.

[0018] Figure 4 is a partial three-dimensional structural sectional view schematic diagram of the gas injection assembly of the present invention.

[0019] Figure 5 is a partial three-dimensional structural exploded view of the gas injection assembly of the present invention.

[0020] Figure 6 is a partial three-dimensional structural sectional view schematic diagram of the present invention.

[0021] Figure 7 is a three-dimensional structural exploded view of the fixing frame, the blocking frame and the wedge block of the present invention.

[0022] Figure 8 is a three-dimensional structural schematic diagram of the gas injection pipe, the exhaust pipe and the connecting pipe of the present invention.

[0023] Figure 9 is a partial three-dimensional structural schematic diagram of the gas injection pipe, the connecting pipe and the connecting frame of the present invention.

[0024] Figure 10 is a process flow chart of the present invention.

[0025] In the attached drawing reference numerals: 1 - base, 2 - mold assembly, 3 - melt injection assembly, 4 - runner, 5 - gas injection assembly, 501 - bracket, 502 - fixed housing, 503 - gas chamber, 504 - gas injection pipe, 505 - gas needle, 506 - rotating column, 507 - air hole, 508 - limiting inclined plate, 509 - piston, 61 - orientation assembly, 611 - fixed frame, 7 - plugging frame, 8 - first elastic member, 9 - chute, 10 - wedge-shaped block, 11 - second elastic member, 12 - inclined chute, 13 - exhaust pipe, 14 - connecting pipe, 15 - fixed seat, 16 - electric push rod, 17 - connecting frame, 18 - plugging pipe. Detailed implementation mode

[0026] The present invention will be specifically described below with reference to the attached drawings.

[0027] Embodiment 1 As Figures 1 to 7 shown, the present invention provides a gas-assisted micro-injection molding device. As Figures 1 - 9 shown, it includes a base 1, a mold assembly 2, a melt injection assembly 3, a runner 4 and a gas injection assembly 5; Among them, a mold assembly 2 is provided on the left side of the top of the base 1. The mold assembly 2 includes a front mold and a rear mold. An injection cavity is provided between the front mold and the rear mold. A melt injection assembly 3 is provided on the right side of the top of the base 1. A runner 4 is provided between the mold assembly 2 and the melt injection assembly 3. The runner 4 communicates the melt injection assembly 3 with the cavity of the mold assembly 2 to realize micro-injection molding; Among them, a gas injection assembly 5 for extruding and pushing the melt during injection molding is provided at a position on the top of the base 1 close to the runner 4.

[0028] Among them, an orientation assembly 6 is provided at one end of the runner 4 close to the melt injection assembly 3.

[0029] The gas injection assembly 5 includes a bracket 501, a fixed housing 502, a gas chamber 503, a gas injection pipe 504, a gas needle 505, an electric control rotating column 506, an air hole 507, a limiting inclined plate 508 and a piston 509; Among them, a bracket 501 is provided at a position on the top of the base 1 close to the runner 4. A fixed housing 502 is provided on the upper part of the bracket 501 for stably installing the gas injection assembly 5; Among them, two gas chambers 503 are symmetrically arranged about the center at the top of the fixed housing 502. A gas injection pipe 504 is provided at the top of the gas chamber 503. A gas needle 505 penetrating the side wall is provided on the side of the runner 4. The gas needle 505 is connected to the end of the gas injection pipe 504 on the gas chamber 503 close to the runner 4. The gas injection pipe 504 not connected to the gas needle is connected to an external gas storage device to realize the connected gas injection inside the runner; The total length of the gas injection pipe 504 is between 8 cm and 12 cm. The gas injection pipe 504 with a length between 8 cm and 12 cm can maintain a certain space for the melt to flow into the gas injection pipe during the injection molding of the melt injection assembly 3, preventing it from flowing into the gas injection assembly 5, and effectively preventing a large amount of the melt from solidifying and blocking the gas injection pipeline, thus affecting the subsequent gas injection effect. Among them, an electrically controlled rotating column 506 is horizontally rotatably arranged inside the fixed shell 502. A plurality of air holes 507 are evenly spaced downward at the top of the electrically controlled rotating column 506. A limiting inclined plate 508 is arranged in the middle of the bracket 501. Pistons 509 are arranged in the air holes 507 of the electrically controlled rotating column 506. The bottom of the piston 509 is limit-connected to the limiting inclined plate 508, which is used to control the stable and precise injection of gas into the runner, and prevent the gas from leaking back from the runner.

[0030] Working principle: Exemplarily, when injection molding is carried out, the raw materials are melted by the melt injection assembly and extruded into the mold assembly 2 that has been closed and sealed through the runner 4. After the melt partially fills the runner 4, the gas injection assembly 5 controls the gas to push the melt in the runner 4 for micro-injection molding. The orientation assembly 6 prevents the substances in the runner 4 from flowing back into the melt injection assembly 3, completing filling and pressure holding. During this process, the gas can continuously provide stable pressure to push the melt to fill the cavity, enabling the melt injected into the runner 4 to be extruded by the gas to fill the cavity of the mold, saving the loss of material leftovers, and at the same time ensuring the complete filling of the cavity by the melt using air pressure.

[0031] In this embodiment, the gas injection assembly 5 is composed of a bracket 501, a fixed housing 502, a gas chamber 503, an injection pipe 504, a gas needle 505, an electronically controlled rotating column 506, air holes 507, and a piston 509. When gas injection is required, the electronically controlled rotating column 506 is started, and the electronically controlled rotating column 506 rotates within the fixed housing 502. When the electronically controlled rotating column 506 rotates, it can drive the piston 509 to rotate around the limiting inclined plate 508. Under the limiting effect of the limiting inclined plate 508 on the piston 509, the piston 509 moves up and down within the air holes 507 while rotating around the limiting inclined plate 508. When the piston 509 passes through the gas chamber 503 that is not connected to the runner 4, the piston 509 moves downward, and the upper inner side of the air holes 507 is filled with gas. When the piston 509 passes through the bottom of the gas chamber 503 connected to the runner 4, the piston 509 moves upward, and the gas on the upper inner side of the air holes 507 is pushed into the injection pipe 504. When the electronically controlled rotating column 506 rotates continuously, gas is continuously replenished into the runner 4, thus achieving the purpose of rapid gas injection and accurately controlling the air pressure for extruding and pushing the melt within the runner 4. Moreover, the structure of rotating gas injection can, to the greatest extent, avoid gas backflow into the gas injection assembly 5 and leakage during the pressure holding process. At the same time, the gas needle 505 is generally made of metal, with certain strength and corrosion resistance to withstand the high temperature and pressure during the injection molding process. The injection of gas can use the air pressure to better extrude and fill the melt into the mold cavity during the flow process, thereby making the surface of the workpiece smoother and improving the appearance quality. When exhausting the air within the runner 4, by controlling the reverse rotation of the electronically controlled rotating column 506, the effect of exhausting and reducing the pressure of the runner 4 can be achieved.

[0032] As described, the orientation assembly 6 includes a fixed frame 61, a blocking frame 7, a first elastic member 8, a wedge-shaped block 10, and a second elastic member 11. A plurality of fixed frames 61 are symmetrically arranged about the central axis of the runner 4 on the inner side of the runner 4 near the position of the melt injection assembly 3. A blocking frame 7 is provided between the fixed frames 61 inside the runner 4. The legs of the blocking frame 7 slide within the fixed frames 61. When the blocking frame 7 contacts the runner port, it completely blocks the runner port. A first elastic member 8 is provided between the blocking frame 7 and the fixed frame 61; a wedge-shaped block 10, a chute 9 is opened at a position on the inner side wall of the runner 4 near the port of the fixed frame 61. A wedge-shaped block 10 is slidably arranged within the chute 9. An inclined groove 12 is provided on one side of the leg of the blocking frame 7 in contact with the inner wall of the runner 4. The inclined groove 12 is in contact and cooperation with the wedge-shaped block 10. A second elastic member 11 is used between the wedge-shaped block 10 and the chute 9.

[0033] To prevent gas in the runner 4 from entering the barrel through the nozzle, a fixed frame 61, a plugging frame 7, a first elastic member 8, a wedge block 10, and a second elastic member 11 are installed in the runner 4. When the melt injection assembly 3 injects melt into the runner 4, the melt is pushed to squeeze the plugging frame 7. The plugging frame 7 is pushed to move closer to the fixed frame 61, the first elastic member 8 is compressed, and the plugging frame 7 is disengaged from the port of the runner 4. The plastic melt flows from the melt injection assembly 3 into the interior of the runner 4. During the above process, the wedge block 10 is engaged in the inclined slot 12 of the plugging frame 7 under the action of the second elastic member 11. When initially pushing the plugging frame 7, the inclined slot 12 of the plugging frame 7 pushes the wedge block 10 to compress the second elastic member 11 and move into the interior of the sliding slot 9. This structural effect makes it necessary to apply a greater extrusion thrust when disengaging the plugging frame 7 from the port of the runner 4. Moreover, when the injection volume is sufficient and the melt injection assembly 3 stops injecting melt, the plugging frame 7 moves towards the port of the runner 4 under the action of the first elastic member 8. When the inclined slot 12 of the plugging frame 7 approaches the wedge block 10, the wedge block 10 extends out of the sliding slot 9 under the action of the second elastic member 11, further pushing the plugging frame 7 towards the port of the runner 4 to ensure complete contact between the plugging frame 7 and the port of the runner 4, avoiding the situation where the plugging frame 7 cannot completely block the port of the runner 4 due to excessive melt sealing, resulting in gas leakage into the melt injection assembly 3 during gas injection, thus achieving the effect of preventing gas backflow.

[0034] Embodiment 2 As Figure 8 and Figure 9 shown, on the basis of Embodiment 1, it further includes an exhaust pipe 13, a connecting pipe 14, a fixed seat 15, an electric push rod 16, a connecting frame 17, and a plugging pipe 18. The injection gas pipe 504 connected to the gas needle 505 is connected to an exhaust pipe 13 at one end close to the gas needle 505. A connecting pipe 14 is provided on the exhaust pipe 13, and the connecting pipe 14 is connected to the waste gas recovery device. A fixed seat 15 is provided on the top of the fixed shell 502, and an electric push rod 16 is provided on the upper part of the fixed seat 15. A plugging pipe 18 is slidably arranged inside the injection gas pipe 504, and the plugging pipe 18 can move to block the exhaust pipe 13. One end of the plugging pipe 18 close to the electric push rod 16 is connected to a connecting frame 17. The connecting frame 17 slidably penetrates the side wall of the injection gas pipe 504, and the connecting frame 17 is connected to the telescopic rod of the electric push rod 16.

[0035] For convenient exhaust, an exhaust pipe 13 is connected to the injection pipe 504. During injection, first control the electric push rod 16 to drive the plugging pipe 18 to move towards the end close to the air needle 505. Finally, isolate the inside of the injection pipe 504 from the exhaust pipe 13, and the gas is normally injected into the runner 4. When exhaust is required, control the electric push rod 16 to drive the plugging pipe 18 to move towards the end close to the injection assembly 5 through the connecting frame 17. The inside of the injection pipe 504 is reconnected to the exhaust pipe 13, and the gas in the runner 4 is discharged into the external waste gas collection equipment through the exhaust pipe 13 and the connecting pipe 14 under the action of air pressure. In this way, it is convenient to operate injection and exhaust, and it can also prevent melt debris from entering the injection assembly 5 during exhaust, which affects injection.

[0036] As Figure 3 shown, the air needle 505 is arranged on the runner 4 in an inclined direction towards the mold; The air needle 505 is arranged on the runner 4 in a state of inclining towards the mold, which can better blow air into the mold during injection, and prevent the melt in the runner 4 from being blown towards the end of the runner 4 close to the plugging frame 7.

[0037] Embodiment 3 As Figure 10 shown, a gas-assisted micro-injection molding method of the present invention specifically includes the following steps: S1. Preheat the mold assembly 2 to a predetermined temperature, close the mold and fix it, and then slowly inject the melt into the runner 4; S2. When the injection amount of the melt in the runner 4 between the injection assembly 5 and the mold assembly 2 is greater than the demand for filling the cavity of the mold assembly 2, stop injecting the melt into the runner 4, then open the injection assembly 5 on the runner 4 system, and uniformly and stably inject gas into the runner 4 through the injection assembly 5; S3. Control the gas to drive the melt in the runner 4 into the cavity to ensure complete filling, and then maintain the pressure in the mold assembly 2 for a period of time.

[0038] S4. After maintaining the pressure for a period of time, stop injecting gas from the injection assembly 5 and control the plugging pipe 18 to no longer isolate the exhaust pipe 13. Discharge the gas through the exhaust pipe 13 and the connecting pipe 14 to exhaust and relieve the pressure in the mold. When the air pressure in the mold returns to the atmospheric pressure level, open the mold to take out the part.

[0039] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A gas-assisted micro-injection molding device, comprising: A base (1) and a mold assembly (2), wherein the mold assembly (2) is provided on the top of the base (1), and a melt injection assembly (3) is provided on the top of the base (1), and the mold assembly (2) and the melt injection assembly (3) are connected through a hollow flow channel (4); characterized in that it also includes: A gas injection component (5), wherein a gas injection component (5) is provided on the top of the base (1); An orientation component (6), wherein an orientation component (6) is provided inside the flow channel (4); The gas injection assembly (5) comprises: A fixed shell (502), wherein the top of the base (1) is provided with the fixed shell (502) via a bracket (501), the top of the fixed shell (502) is provided with two air chambers (503), and the top of the air chamber (503) is provided with an air injection pipe (504); An air needle (505), the flow channel (4) is connected to the air needle (505), and the air needle (505) is connected to the end of the air injection pipe (504); An electrically controlled rotating column (506), wherein the fixed shell (502) is internally provided with an electrically controlled rotating column (506) having a plurality of air holes (507) on the top, and pistons (509) are slidably provided in the air holes (507); A limiting inclined plate (508), wherein the middle portion of the bracket (501) is provided with a limiting inclined plate (508), and the bottom of the piston (509) is connected to the limiting inclined plate (508) in a limiting manner.

2. A gas-assisted micro-injection molding device according to claim 1, characterized in that: The orientation component (6) comprises: A fixing frame (61), wherein a plurality of fixing frames (61) are provided on the inner side of the flow channel (4) near the melt injection assembly (3); A blocking frame (7) is provided between the blocking frame (7) and the fixing frame (61), and a support leg of the blocking frame (7) slides inside the fixing frame (61); A first elastic member (8), wherein the first elastic member (8) is provided between the blocking frame (7) and the fixing frame (61); A wedge block (10) is provided with a slide groove (9) on the inner wall of the flow channel (4) near the port of the fixed frame (61), the wedge block (10) is slidably arranged in the slide groove (9), and an inclined groove (12) is provided on the side where the support leg of the blocking frame (7) contacts the inner wall of the flow channel (4), and the inclined groove (12) contacts and cooperates with the wedge block (10); A second elastic member (11) is used between the wedge block (10) and the slide groove (9).

3. A gas-assisted micro-injection molding device according to claim 2, characterized in that: Also includes: An exhaust pipe (13), wherein the gas injection pipe (504) connected to the gas needle (505) is connected to the exhaust pipe (13) at one end close to the gas needle (505); A connecting pipe (14), wherein the exhaust pipe (13) is provided with a connecting pipe (14), and the connecting pipe (14) is connected to an external exhaust gas recovery device; A fixing seat (15), wherein the fixing shell (502) is provided with a fixing seat (15) on the top thereof; An electric push rod (16), the upper part of the fixed seat (15) is provided with an electric push rod (16); A plugging tube (18), wherein a plugging tube (18) is slidably provided inside the gas injection tube (504); A connecting frame (17) is connected to one end of the sealing tube (18) close to the electric push rod (16). The connecting frame (17) slides through the side wall of the gas injection tube (504) and is connected to the telescopic rod of the electric push rod (16).

4. A gas-assisted micro-injection molding device according to claim 1, characterized in that: The air needle (505) is arranged on the flow channel 4 in a direction inclined toward the mold.

5. The gas-assisted micro-injection molding device according to claim 1, characterized in that: The total length of the gas injection pipe (504) is between 8CM and 12CM.

6. A gas-assisted micro-injection molding method, characterized in that The gas-assisted micro-injection molding device according to any one of claims 1 to 4 is used for injection molding, and the specific molding process is divided into the following steps: S1, preheat the mold, close the mold, and inject the melt; S2. When the amount of melt injected is sufficient to fill the cavity of the mold component (2), the melt injection stops; the gas injection component (4) on the flow channel is opened, and gas is injected through the gas injection component (4); S3, controlling the gas to drive the melt in the flow channel (1) into the cavity of the mold component (2) to complete filling and pressure holding; S4. After maintaining the pressure for a period of time, the gas is exhausted and the pressure is released, and the mold is opened to take out the parts.

7. A gas-assisted micro-injection molding method according to claim 5, characterized in that: The gas injected by the gas injection component (4) uses nitrogen as the extrusion gas.

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