Active backpressure control structure and method based on electric pre-molding injection molding machine

Abstract

The invention relates to an active backpressure control structure and method based on an electric pre-molding injection molding machine, the active backpressure control structure comprises a screw rod used for extruding and shearing raw materials, the rear end of the screw rod is connected with a coupling, the other end of the coupling is connected with a pre-molding servo motor used for driving the screw rod to rotate, and the pre-molding servo motor is connected with an electric pre-molding injection molding machine. The pre-plasticizing servo motor is fixedly mounted on the pre-plasticizing seat, an injection piston rod is arranged on the pre-plasticizing seat, an injection piston is arranged at the front end of the injection piston rod and moves in an injection cavity, and an injection withdrawing cavity is formed in the front end of the injection piston; and the oil pressure of the injection cavity is controlled by an electromagnet. According to the novel back pressure control mode, the electromagnet is electrified during material storage, injection action is output, proper pressure flow is supplied to the injection cavity through the control valve, reverse thrust is actively generated to the screw rod, gas and the like in the molten raw material storage cavity are discharged out of the charging barrel through the screw edge of the screw rod, and the injection effect is achieved. Therefore, the higher consistency of the specific gravity of the molten raw materials is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of injection molding machine manufacturing, and in particular to a structure and method for active back pressure control based on an electric pre-molding injection molding machine. Background Art

[0002] The back pressure technology of the injection molding machine refers to a technology that applies pressure to the rear end of the screw during the injection process to prevent the molten plastic from flowing forward without restriction, so as to ensure uniform compaction of the molten material and improve product quality. Back pressure is also called plasticizing pressure, and its control is achieved by adjusting the return oil throttle valve of the injection cylinder. The back pressure valve is installed at the rear of the injection cylinder of the pre-plasticizing screw injection molding machine to adjust the speed of the injection cylinder's oil leakage when the screw rotates backward, so that the cylinder maintains a certain pressure.

[0003] The role and impact of back pressure:

[0004] Prevent the screw from retreating too quickly: During the melting and plasticizing process of plastic, the molten material continuously moves toward the front end of the barrel, gradually forming a pressure that pushes the screw backward. In order to prevent the screw from retreating too quickly and ensure that the molten material is evenly compacted, it is necessary to provide a reverse pressure to the screw. This reverse pressure that prevents the screw from retreating is called back pressure.

[0005] Improve product quality: Proper adjustment of back pressure can increase the density of the molten material in the barrel, improve the shot volume, product weight and size stability; squeeze out the air in the raw material to make the raw material denser; slow down the screw retreat speed to fully plasticize the molten material in the barrel, increase the mixing uniformity of color powder, masterbatch and molten material, and avoid color mixing in the product; improve the shrinkage of the product surface and the glue flow around the product; increase the temperature of the molten material, improve the fluidity of the molten material when filling the mold, and there will be no cold glue lines on the surface of the product.

[0006] Back pressure adjustment method: Back pressure adjustment is usually achieved by adjusting the return oil throttle valve of the injection cylinder. A back pressure valve is installed at the rear of the injection cylinder of the pre-plasticizing screw injection molding machine to adjust the speed of oil leakage from the injection cylinder when the screw rotates backward.

[0007] Too low back pressure will result in poor plasticizing quality, unstable injection volume, large changes in product weight and product size, shrinkage, gas flowers, cold material lines, uneven gloss and other undesirable phenomena on the product surface. Too high back pressure will reduce plasticizing efficiency, deteriorate product surface color / gloss, slow screw retreat, long pre-plastic return time, increase cycle time, and reduce production efficiency.

[0008] In the prior art, this back pressure regulation belongs to passive back pressure, which is generated by the continuous input of molten raw materials, the accumulation of raw materials extruding the screw, so that the injection piston retreats, and the oil in the extrusion injection chamber overflows back to the oil tank. Relatively speaking, the pressure establishment has a certain lag, which will cause a certain difference in density between the first small section of raw materials in the molten raw material storage area and the raw materials after the back pressure is fully established. When producing high-precision products, it is easy to produce deviations in gram weight and the surface or product strength of the product itself due to different raw material densities. Summary of the invention

[0009] The object of the present invention is to provide a structure and method for active back pressure control based on an electric pre-molding injection molding machine to solve the problems raised in the above background technology.

[0010] In order to solve the above technical problems, the present invention is achieved through the following technical measures: a structure based on active back pressure control of an electric pre-plasticizing injection molding machine, characterized in that: it includes a screw for extruding and shearing raw materials, a coupling is connected to the rear end of the screw, and the other end of the coupling is connected to a pre-plasticizing servo motor for driving the screw to rotate, the pre-plasticizing servo motor is fixedly installed on a pre-plasticizing seat, an injection piston rod is arranged on the pre-plasticizing seat, an injection piston is arranged at the front end of the injection piston rod, the injection piston moves in an injection chamber, and the front end of the injection piston is an ejection chamber; the oil pressure of the injection chamber is controlled by an electromagnet.

[0011] Compared with the prior art, the advantages of the present invention are: this new back pressure control method allows the electromagnet to be energized when storing materials, outputs the injection action, gives a suitable pressure flow to the injection chamber through the control valve, and actively generates a reverse thrust to the screw, so that the gas in the molten raw material storage chamber is discharged out of the barrel through the screw ribs, thereby ensuring a higher consistency in the specific gravity of the molten raw material.

[0012] As an improvement of the present invention, one end of the injection piston rod is connected to the pre-molding seat, and the other end of the injection piston rod is connected to the injection seat. The purpose of selecting this design is to enable the injection piston rod to move and provide reverse thrust to the screw through the pre-molding seat.

[0013] As an improvement of the present invention, the pre-plastic seat is arranged on a linear guide rail. The purpose of selecting this design is that the pre-plastic seat can move smoothly on the linear guide rail, and the linear guide rail is fixed on the machine base.

[0014] As an improvement of the present invention, the injection piston rod has two sets, which are symmetrically arranged on both sides of the screw. The purpose of selecting this design is that the structure arranged on both sides can evenly bear the force when pushing the screw.

[0015] The present invention also provides a method for controlling active back pressure of an electric pre-molding injection molding machine, comprising the structure for active back pressure control of an electric pre-molding injection molding machine as described in claims 1 to 4, characterized in that the control steps are as follows:

[0016] 1: When electromagnet YV1 is energized, the injection molding machine performs mold closing action. When electromagnets YV1 and YV2 are energized, the injection molding machine performs differential mold closing action and performs rapid mold closing;

[0017] 2: When the electromagnet YV1 is energized, the injection molding machine performs low-pressure mold protection. When the electromagnet YV1 is energized, the injection molding machine performs high-pressure mold clamping.

[0018] 3: When electromagnet YV7 is energized, the injection molding machine performs the seat forward action, and the entire injection component moves toward the mold clamping component until the nozzle fits the mold gate. When electromagnets YV4 and YV7 are energized, the injection molding machine performs the injection action;

[0019] 4: The pre-plastic servo motor starts according to the pressure flow command given by the system, and the injection molding machine performs the material storage action. The electromagnet YV4 is energized, outputs the injection action, and the injection cavity actively generates a reverse thrust to the screw;

[0020] 5: When the electromagnet YV5 is energized, the injection molding machine performs the anti-drooling action. When the electromagnet YV8 is energized, the injection molding machine performs the seat retreat action;

[0021] 6: When electromagnets YV3 and YV22 are energized, the injection molding machine performs the mold opening slow speed 1 action. When electromagnet YV3 is energized, the injection molding machine performs the mold opening fast action;

[0022] 7: Electromagnets YV3 and YV22 are energized, and the injection molding machine performs the mold opening slow speed 2 action. Electromagnet YV9 is energized, and the injection molding machine performs the ejection action, and the ejector rod ejects the product in the mold;

[0023] 8: Electromagnet YV10 is energized, and after the product is ejected, the injection molding machine performs the ejection action, and the ejector rod retracts;

[0024] 9: Select the advance and retreat of neutron A or B according to the needs of the mold. When installing the mold, choose the use of mold adjustment advance and retreat according to the thickness of the mold;

[0025] 10: Electromagnet YV1 is energized and the injection molding machine performs the mold closing action. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] In the attached picture:

[0028] Figure 1It is a half-section schematic diagram of the active back pressure module of the electric pre-plasticizing machine according to the present invention.

[0029] Figure 2 It is a three-dimensional diagram of the active back pressure module of the electric pre-plasticizing machine according to the present invention.

[0030] Figure 3 It is a half-section schematic diagram of the passive back pressure module of the existing pre-plasticizing machine according to the present invention.

[0031] Figure 4 It is a three-dimensional schematic diagram of the injection molding machine described in the present invention.

[0032] Figure 5 The hydraulic principle diagram of the electric pre-plasticizing machine of the present invention.

[0033] Figure 6 The present invention discloses an electromagnet action table for the electric pre-plasticizing servo machine.

[0034] Description of reference numerals: 1. hydraulic motor; 2. pre-plastic seat; 3. coupling; 4. injection piston rod; 5. injection chamber; 6. injection piston; 7. ejection chamber; 8. screw; 9. barrel; 10. molten raw material storage chamber; 11. injection seat; 12. linear guide rail; 13. hopper; 14. pre-plastic servo motor; 15. machine base; 16. injection unit; 17. screw unit; 18. die unit;

[0035] YV1: mold closing electromagnet; YV2: mold closing differential electromagnet; YV3: mold opening electromagnet; YV4: injection electromagnet; YV5: ejection electromagnet; YV7: seat table advance electromagnet; YV8: seat table retreat electromagnet; YV9: push-in electromagnet; YV10: push-out electromagnet; V12: control valve. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0037] Example 1

[0038] Please refer to Figure 1 -6.

[0039] The injection molding machine generally includes a machine base 15 , at the rear end of which is an injection unit 16 , at the front end of which is connected a screw unit 17 , at the front end of which is connected a die unit 18 , and above which is a hopper 13 .

[0040] The present embodiment provides a structure of active back pressure control based on an electric pre-molding injection molding machine, which includes a screw 8 for extruding and shearing raw materials, a coupling 3 is connected to the rear end of the screw 8, and the other end of the coupling 3 is connected to a pre-molding servo motor 14 for driving the screw 8 to rotate, and the pre-molding servo motor 14 is fixedly installed on a pre-molding seat 2, an injection piston rod 4 is provided on the pre-molding seat 2, and an injection piston 6 is provided at the front end of the injection piston rod 4. The injection piston 6 moves in an injection cavity 5, and the front end of the injection piston 6 is an ejection cavity 7; the oil pressure of the injection cavity 5 is controlled by an electromagnet.

[0041] In the embodiments of the present invention, please refer to Figure 1 (half-section diagram) Figure 2 One end of the injection piston rod 4 is connected to the pre-molding seat 2, and the other end of the injection piston rod 4 is connected to the injection seat 11. The injection piston rod 4 can move, and the pre-molding seat 2 provides a reverse thrust to the screw 8.

[0042] Furthermore, the pre-plasticizing seat 2 is arranged on a linear guide rail 12 . The pre-plasticizing seat 2 can move smoothly on the linear guide rail 12 , and the linear guide rail 12 is fixed on the machine base 15 .

[0043] Furthermore, the injection piston rod 4 has two sets, which are symmetrically arranged on both sides of the screw 8. The structure arranged on both sides can evenly bear the force when pushing the screw 8.

[0044] In the embodiments of the present invention, please refer to Figure 5 and Figure 6 The present invention also provides a method for controlling active back pressure of an electric pre-molding injection molding machine, comprising the structure for controlling active back pressure of an electric pre-molding injection molding machine as described in claim 1-4, characterized in that the control steps are as follows:

[0045] 1: The mold-closing electromagnet YV1 is energized, and the injection molding machine performs the mold-closing action. The mold-closing electromagnet YV1 and the mold-closing differential electromagnet YV2 are energized, and the injection molding machine performs the differential mold-closing action for rapid mold closing;

[0046] 2: When the mold clamping electromagnet YV1 is energized, the injection molding machine performs low-pressure mold protection. When the mold clamping electromagnet YV1 is energized, the injection molding machine performs high-pressure mold clamping.

[0047] 3: The base table feed electromagnet YV7 is energized, and the injection molding machine performs the base table feed action. The entire injection unit 16 parts move toward the mold clamping part until the nozzle fits the mold gate. The injection electromagnet YV4 and the base table feed electromagnet YV7 are energized, and the injection molding machine performs the injection action;

[0048] 4: The pre-plastic servo motor 14 starts to start according to the pressure flow command given by the system, and the injection molding machine performs the material storage action. The injection electromagnet YV4 is energized, outputs the injection action, and the injection cavity 5 actively generates a reverse thrust to the screw 8;

[0049] 5: When the ejection electromagnet YV5 is energized, the injection molding machine performs the anti-drooling action. When the seat table retraction electromagnet YV8 is energized, the injection molding machine performs the seat table retraction action;

[0050] 6: When the mold opening electromagnet YV3 and the mold opening slow electromagnet YV22 are energized, the injection molding machine performs the mold opening slow speed 1 action. When the mold opening electromagnet YV3 is energized, the injection molding machine performs the mold opening fast action;

[0051] 7: The mold opening electromagnet YV3 and the mold opening slow speed electromagnet YV22 are energized, and the injection molding machine performs the mold opening slow speed 2 action. The ejection electromagnet YV9 is energized, and the injection molding machine performs the ejection action, and the ejector rod ejects the product in the mold;

[0052] 8: The ejector electromagnet YV10 is energized, and after the product is ejected, the injection molding machine performs the ejector action, and the ejector rod retracts;

[0053] 9: Select the advance and retreat of neutron A or B according to the needs of the mold. When installing the mold, choose the use of mold adjustment advance and retreat according to the thickness of the mold;

[0054] 10: The mold closing electromagnet YV1 is energized and the injection molding machine performs the mold closing action.

[0055] In the embodiments of the present invention, please refer to Figure 3 During the pre-plasticizing action in the prior art, the system pressure oil is supplied to the hydraulic motor 1 through the valve, and the hydraulic motor 1 drives the screw 8 through the coupling 3. The raw material in the hopper 13 falls into the barrel 9, and is gradually transformed into a molten raw material through the heating of the barrel 9 and the extrusion and shearing of the screw 8, and is transported to the molten raw material storage chamber 10 by the screw 8; at the same time, the molten raw material in the closed molten raw material storage chamber 10 is continuously input, and the extrusion will give the screw 8 a backward thrust, and the screw 8 transmits the thrust to the pre-plasticizing seat 2 through the coupling 3. The pre-plasticizing seat 2 is connected to the injection piston 6 through the injection piston rod 4. The injection piston 6 will move backward to squeeze the oil in the injection chamber 5 back to the oil tank, and the ejection chamber 7 absorbs oil from the total return oil pipeline.

[0056] During the pre-molding process, the plastic raw material gradually changes from solid to liquid, which will produce gas and form bubbles that melt into the raw material, resulting in inconsistent specific gravity of the molten raw material, which can easily cause inconsistent product weight and other defects. Therefore, a pressure control loop will be added in the middle of the oil in the injection chamber 5 returning to the oil tank, so that this part of the return oil will return to the oil tank through a constant overflow pressure, and the resistance of the return oil will be reversely thrust to the screw 8 through the injection piston 6, so that the gas in the molten raw material storage chamber 10 is discharged from the barrel 9 through the screw ridges of the screw 8, thereby ensuring the consistency of the specific gravity of the molten raw material. This overflow pressure that controls the return oil is called passive back pressure because it has a certain hysteresis, which can easily cause inconsistent specific gravity of the molten raw material.

[0057] This application is to improve the original passive back pressure, which requires the oil in the injection chamber 5 to generate back pressure through the pressure control circuit. The original pressure control circuit is not needed, and the pre-plastic servo motor 14 is used to replace the hydraulic motor 1. Then the original power system of the machine does not need to work. We can give an instruction to the original power system, and the electromagnet YV4 is energized to output the injection action, giving the appropriate pressure flow through V12 to the injection chamber 5, actively generating a reverse thrust to the screw 8, so that the gas in the molten raw material storage chamber 10 is discharged from the barrel 9 through the screw ridges of the screw 8. This new control structure and method can immediately apply this back pressure at the beginning of material storage, which can ensure a higher consistency in the specific gravity of the molten raw material.

[0058] The beneficial effect of the present invention is that this new back pressure control method allows the electromagnet to be energized when storing materials, outputs the injection action, and gives a suitable pressure flow to the injection chamber 5 through the control valve V12, actively generating a reverse thrust to the screw 8, so that the gas in the molten raw material storage chamber 10 is discharged from the barrel 9 through the screw ridges of the screw 8, thereby ensuring a higher consistency in the specific gravity of the molten raw material.

[0059] In the description of the present invention, it should be noted that the terms "vertical", "up", "down", "horizontal", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0060] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, 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 structure for active back pressure control based on an electric pre-molding injection molding machine, characterized in that: The invention comprises a screw (8) for extruding and shearing raw materials, a coupling (3) being connected to the rear end of the screw (8), a pre-plasticizing servo motor (14) for driving the screw (8) to rotate being connected to the other end of the coupling (3), the pre-plasticizing servo motor (14) being fixedly mounted on a pre-plasticizing seat (2), an injection piston rod (4) being arranged on the pre-plasticizing seat (2), an injection piston (6) being arranged at the front end of the injection piston rod (4), the injection piston (6) moving in an injection cavity (5), the front end of the injection piston (6) being an ejection cavity (7); the oil pressure of the injection cavity (5) being controlled by an electromagnet.

2. The structure of active back pressure control based on electric pre-molding injection molding machine according to claim 1 is characterized in that: One end of the injection piston rod (4) is connected to the pre-molding seat (2), and the other end of the injection piston rod (4) is connected to the injection seat (11).

3. The structure of active back pressure control based on electric pre-molding injection molding machine according to claim 1 is characterized in that: The pre-molding seat (2) is arranged on a linear guide rail (12).

4. The structure of active back pressure control based on electric pre-molding injection molding machine according to claim 1 is characterized in that: The injection piston rod (4) has two sets, which are symmetrically arranged on both sides of the screw rod (8).

5. A method for controlling active back pressure of an electric pre-molding injection molding machine, comprising the structure for active back pressure control of an electric pre-molding injection molding machine as described in rights 1 to 4, characterized in that the control steps are as follows: 5.1: When electromagnet YV1 is energized, the injection molding machine performs mold closing action. When electromagnets YV1 and YV2 are energized, the injection molding machine performs differential mold closing action and performs rapid mold closing; 5.2: When the electromagnet YV1 is energized, the injection molding machine performs low-pressure mold protection. When the electromagnet YV1 is energized, the injection molding machine performs high-pressure mold clamping. 5.3: When the electromagnet YV7 is energized, the injection molding machine performs the seat forward action, and the entire injection part (16) moves toward the mold clamping part until the nozzle fits the mold gate. When the electromagnets YV4 and YV7 are energized, the injection molding machine performs the injection action; 5.4: The pre-plasticizing servo motor (14) starts to start according to the pressure flow command given by the system, and the injection molding machine performs the material storage action. The electromagnet YV4 is energized, outputs the injection action, and the injection chamber (5) actively generates a reverse thrust to the screw (8); 5.5: When the electromagnet YV5 is energized, the injection molding machine performs the anti-drooling action. When the electromagnet YV8 is energized, the injection molding machine performs the seat retracting action; 5.6: When electromagnets YV3 and YV22 are energized, the injection molding machine performs the mold opening slow speed 1 action. When electromagnet YV3 is energized, the injection molding machine performs the mold opening fast action; 5.7: Electromagnets YV3 and YV22 are energized, and the injection molding machine performs the mold opening slow speed 2 action. Electromagnet YV9 is energized, and the injection molding machine performs the ejection action, and the ejector rod ejects the product in the mold; 5.8: Electromagnet YV10 is energized, and after the product is ejected, the injection molding machine performs the ejection action, and the ejector rod retracts; 5.9: Select the advance and retreat of neutron A or B according to the needs of the mold. When installing the mold, choose the use of mold adjustment advance and retreat according to the thickness of the mold; 5.10: Electromagnet YV1 is energized and the injection molding machine performs the mold closing action.

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