Multi-layer co-extrusion machine head with self-adaptive pressure and using method of multi-layer co-extrusion machine head

Abstract

The invention discloses a pressure self-adaptive multi-layer co-extrusion machine head and a use method thereof. The multi-layer co-extrusion machine head comprises a machine head assembly, a mold core bracket, a core rod and a driving system; a rear cover plate is installed on the rear side face of the machine head assembly. One end of the mold core support is connected with the driving system, and the other end of the mold core support penetrates through the rear cover plate, extends forwards in the axial direction and is detachably connected with a core rod arranged at the axis of the machine head assembly; a mold core support threaded plate is fixedly arranged on the rear side face of the rear cover plate, and the mold core support threaded plate is arranged on the mold core support in a sleeving mode and connected with the mold core support in a matched mode. The machine head assembly comprises a machine head body, a multi-layer melt cavity channel, a core rod and a mouth mold; the driving system comprises a controller, a power output hollow shaft, a speed reducer and a driving motor, according to the pressure self-adaptive multi-layer co-extrusion machine head, the problems of pressure fluctuation and the like existing in existing multi-layer co-extrusion pipe preparation can be solved.

Description

Technical Field

[0001] The invention relates to a multi-layer co-extrusion die head, and in particular to a pressure-adaptive multi-layer co-extrusion die head and a use method thereof. Background Art

[0002] Multi-layer co-extrusion can achieve the goal of bonding materials with different characteristics tightly together during the extrusion process, so that the product has the special properties, appearance and mechanical properties of each layer of material, such as oxygen barrier, water barrier, heat preservation, coloring, stiffness, hardness, etc. However, the differences between the layers are often large, and the required processing temperatures are also quite different. For example, when nylon and polyethylene are co-extruded in multiple layers, the temperature difference is about 100°C, but in order to ensure that nylon can be effectively processed, the temperature of the die can only be raised to the processing temperature of nylon. In this case, the melt strength of the polyethylene layer becomes extremely low, which easily makes the die pressure unstable, further causing the appearance and performance of the product to be unstable.

[0003] The melt pressure in the die of the extruder generally comes from two sources. One is that the melt accumulates in the flow channel to build up the melt pressure after the material is discharged from the screw head by the screw conveyor. The other is that a melt pump is added to stabilize the melt pressure after the melt is discharged from the screw. These two sources are effective means for extruding a single material. When the melt pressure fluctuates at the die, it can no longer be adjusted by human intervention or automatic correction through equipment adjustment. At the confluence of each layer in the die of multi-layer co-extruded melt, due to different melt temperatures and material properties, the melt strength and viscosity are different, which makes the melt pressure after confluence produce a significant change, which can easily cause pressure instability.

[0004] In addition, during the extrusion process of fiber-reinforced materials, the melt pressure in the die head often fluctuates due to uneven fiber distribution, resulting in appearance defects of the extruded products. In more serious cases, the fibers will block the flow channel outlet. In this case, the existing practice is to disassemble the mold for cleaning.

[0005] Therefore, it is necessary to develop a pressure-adaptive multi-layer co-extrusion die to solve the problems of pressure fluctuation and the like in the prior art.

[0006] Patent CN204773458U proposes a sleeve-type multi-layer co-extrusion die head, which has only three layers. The precision of five layers will be significantly reduced. In addition, since the inner and outer flow channels are relatively long, when the melt flows to the vicinity of the die outlet, the melt strength of each layer is quite different, and the melt pressure is no longer easily affected by the pressure established by the screw. Therefore, the melt strength difference between layers is large, the melt pressure is unstable after the layers are merged, and inherent defects such as pressure fluctuations that are prone to occur when processing fiber-reinforced materials still exist.

[0007] Patent CN206983191U changes the discharge amount to adjust the melt pressure by changing the speed of the extrusion screw. However, it is generally believed in the industry that the fluctuation of the melt pressure during the extrusion process cannot be adjusted by the screw speed, because the screw speed changes too drastically, which can easily cause more drastic pressure instability; and after the screw speed is adjusted, it takes a long time to extrude defective products before it can stabilize; this solution has no practical application value. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a pressure-adaptive multi-layer co-extrusion die head and a method of using the same.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] The present invention firstly proposes a pressure-adaptive multi-layer co-extrusion die head, comprising a die head assembly, a mold core support, a core rod, and a driving system;

[0011] A rear cover plate is installed on the rear side of the head assembly; one end of the core bracket is connected to the drive system, and the other end passes through the rear cover plate and extends axially forward and is detachably connected to the core rod arranged at the axis of the head assembly; a core bracket threaded plate is fixedly arranged on the rear side of the rear cover plate, and the core bracket threaded plate is sleeved on the core bracket and connected with the core bracket;

[0012] The die assembly comprises a die body, a multi-layer melt cavity, a core rod and a die; the multi-layer melt cavity is coaxially arranged in the die body and sleeved on the core support and the core rod; a front cover plate is installed on the front side of the die body, and a die mounting part and a die are installed on the front side of the front cover plate; there is a co-extrusion cavity between the front cover plate and the core rod and the die, and the discharge ports of the multi-layer melt cavity are respectively connected to the co-extrusion cavity; a pressure sensor probe is arranged in the co-extrusion cavity, and is an integrated structure with the melt pressure sensor fixed on the front cover plate;

[0013] The driving system includes a controller and a power output hollow shaft, a reducer, and a driving motor which are sequentially installed on the tailstock; the tailstock is slidably connected to the guide rail; the power output hollow shaft is connected to the core support through a connecting half shaft; the core support can rotate and move forward and backward under the drive of the driving system, and at the same time the volume of the co-extrusion cavity changes to achieve pressure adaptation.

[0014] As some preferred examples of the multi-layer co-extrusion head in the present invention, the die mounting piece is provided with an adjustment screw cover plate, which is used to press the die mounting piece onto the front cover plate and adjust the eccentricity of the die through multiple adjustment screws distributed along the radial direction of the front cover plate.

[0015] As some preferred examples of the multi-layer co-extrusion die in the present invention, a thermocouple is provided on the die body.

[0016] As some preferred examples of the multi-layer co-extrusion die head in the present invention, the core support threaded plate and the rear cover plate are fixedly connected by fastening screws.

[0017] As some preferred examples of the multi-layer co-extrusion die head in the present invention, the core support and the core rod are detachably connected via threads.

[0018] As some preferred examples of the multi-layer co-extrusion die head in the present invention, the connection between the core support threaded plate and the core support is a threaded connection or a ball screw connection.

[0019] As some preferred examples of the multi-layer co-extrusion die head in the present invention, the connecting half shaft (6) and the core support are rigidly connected via a coupling.

[0020] As some preferred examples of the multi-layer co-extrusion die in the present invention, the guide rail is fixedly mounted on the mold body; the die assembly is mounted on the mold body via a support rod.

[0021] As some preferred examples of the multi-layer co-extrusion die head in the present invention, the controller is connected to the melt pressure sensor and the drive motor through electrical signals.

[0022] In the multi-layer co-extrusion die head provided by the present invention, the multi-layer melt cavity inside the multi-layer co-extrusion die head can be optionally 3 layers or 5 layers. When the extruded material includes fiber-reinforced material, if the multi-layer melt cavity is 3 layers, it is recommended that the fiber-reinforced material be in the 2nd layer, and if the multi-layer melt cavity is 5 layers, it is recommended that the fiber-reinforced material be in any one or more of the 2nd, 3rd, and 4th layers to avoid the appearance defects of the pipe such as floating fibers on the surface. At the same time, the innermost layer and the outermost layer are recommended to be protective layers or medium-resistant layers, which are more conducive to protecting the pipe. The fiber-reinforced material as an intermediate layer can improve the overall strength of the pipe.

[0023] Secondly, the present invention also provides a pressure adjustment method for a pressure-adaptive multi-layer co-extrusion die as described above, comprising the following steps:

[0024] S1. After the machine is initialized, input the melt pressure setting value according to the extrusion conditions;

[0025] S2. During the production process, the melt pressure sensor collects the melt pressure signal in the current co-extrusion cavity in real time and converts it into a voltage or current signal to be recognized by the controller;

[0026] S3, the controller compares the melt pressure acquisition value with the set value to obtain the difference, and converts the positive and negative values ​​of the difference into the forward and reverse control signals of the drive motor;

[0027] S4, after receiving the forward and reverse control signal, the driving motor generates a rotational motion, and drives the mold core bracket to rotate in the forward or reverse direction through the power output hollow shaft, thereby generating a forward or backward displacement, and realizing the self-adaptive adjustment of the melt pressure;

[0028] Preferably, when the melt pressure is too high, the above pressure regulation method controls the core support to move backward, so that the volume of the co-extrusion cavity increases and the melt pressure is released; when the melt pressure is too low, the above pressure regulation method controls the core support to move forward, so that the volume of the co-extrusion cavity decreases and the system pressure is maintained stable.

[0029] The present invention drives the core support and the core rod to move forward and backward through the driving system to adjust the melt pressure in the co-extrusion cavity, ensure the stability of the system pressure, realize the multi-layer co-extrusion head pressure self-adaptive adjustment process, solve the inherent defects of unstable material discharge between layers and pressure fluctuation, and is also particularly suitable for solving the pressure fluctuation defect caused by uneven fiber distribution during the extrusion of fiber-reinforced materials, which can ensure the stability of production and the uniformity of thickness of the pipe.

[0030] Instruction Manual

[0031] Figure 1 It is a schematic diagram of the overall structure of the multi-layer co-extrusion die head in the present invention.

[0032] Figure 2 It is an enlarged structural schematic diagram of the die head assembly with five layers of melt channels.

[0033] Figure 3 It is a schematic diagram of the enlarged structure of the die head assembly of the three-layer melt cavity.

[0034] Figure 4 This is a schematic diagram of the co-extrusion cavity state when the core support is adjusted to move backward when the melt pressure is too high.

[0035] Figure 5 Schematic diagram of the co-extrusion cavity state in which the core support is adjusted forward when the melt pressure is too low.

[0036] In the figure, 1. driving motor; 2. reducer; 3. power output hollow shaft; 4. guide rail; 5. tailstock; 6. connecting half shaft; 7. core bracket; 8. support rod; 9. mold body; 10. die; 11. die mounting; 12. adjustment screw cover plate; 13. adjustment screw; 14. front cover plate; 15. melt pressure sensor; 16. head body; 17. thermocouple; 18. multi-layer melt cavity; 19. rear cover plate; 20. core bracket threaded plate; 21. fastening screw; 22. core rod. DETAILED DESCRIPTION

[0037] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the related listed items. The top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structures shown in the drawings. They are relative concepts and may therefore change accordingly according to their different locations and different usage states.

[0039] In the description of the present invention, the terms "center", "front", "back", "left", "right", "vertical", "horizontal", "inside", "outside", etc. used to indicate the orientation or position relationship are based on the orientation or position relationship shown in the 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, structure and operation, and therefore cannot be understood as a limitation on the present invention.

[0040] In one embodiment of the present invention, a pressure-adaptive multi-layer co-extrusion die head, such as Figure 1 As shown, it includes a head assembly, a core support 7, a core rod 22, and a drive system;

[0041] A rear cover plate 19 is installed on the rear side of the head assembly; one end of the core bracket 7 is connected to the drive system, and the other end passes through the rear cover plate 19 and extends axially forward and is detachably connected to a core rod 22 arranged at the axis of the head assembly; a core bracket threaded plate 20 is fixedly arranged on the rear side of the rear cover plate 19, and the core bracket threaded plate 20 is sleeved on the core bracket 7 and matched with the core bracket 7;

[0042] The die assembly comprises a die body 16, a multi-layer melt cavity 18, a core rod 22 and a die 10; the multi-layer melt cavity is coaxially arranged in the die body 16 and sleeved on the core support 7 and the core rod 22; a front cover plate 14 is installed on the front side of the die body 16, and a die mounting part 11 and a die 10 are installed on the front side of the front cover plate 14; there is a co-extrusion cavity between the front cover plate 14 and the core rod 22 and the die 10, and the discharge ports of the multi-layer melt cavity are respectively connected to the co-extrusion cavity; a pressure sensor probe is arranged in the co-extrusion cavity, and is an integrated structure with the melt pressure sensor 15 fixed on the front cover plate 14;

[0043] The driving system includes a controller and a power output hollow shaft 3, a reducer 2, and a driving motor 1 which are sequentially installed on a tailstock 5; the tailstock 5 is slidably connected to a guide rail 4; the power output hollow shaft 3 is connected to a core support 7 via a connecting half shaft 6; the core support 7 can rotate and move forward and backward under the drive of the driving system, and at the same time, the volume of the co-extrusion cavity changes to achieve pressure adaptation.

[0044] The die mounting member 11 is sleeved with an adjustment screw cover plate 12 for pressing the die mounting member 11 onto the front cover plate 14 and adjusting the eccentricity of the die through a plurality of adjustment screws 13 distributed along the radial direction of the front cover plate.

[0045] The head body 16 is provided with a thermocouple 17 .

[0046] The core support threaded plate 20 and the rear cover plate 19 are fixedly connected by fastening screws 21 .

[0047] The core support 7 and the core rod 22 are detachably connected via threads.

[0048] The connection between the core support thread plate 20 and the core support 7 is threaded connection or ball screw connection.

[0049] The connecting half shaft 6 and the core support 7 are rigidly connected via a coupling.

[0050] The guide rail 4 is fixedly mounted on the mold body 9 ; the head assembly is mounted on the mold body 9 via a support rod 8 .

[0051] The controller is connected to the melt pressure sensor 15 and the drive motor through electrical signals.

[0052] In another specific embodiment of the present invention, a pressure regulating method for a pressure-adaptive multi-layer co-extrusion die head comprises the following steps:

[0053] S1. After the machine is initialized, input the melt pressure setting value according to the extrusion conditions;

[0054] S2. During the production process, the melt pressure sensor 15 collects the melt pressure signal in the current co-extrusion cavity in real time and converts it into a voltage or current signal to be recognized by the controller;

[0055] S3, the controller compares the melt pressure acquisition value with the set value to obtain the difference, and converts the positive and negative values ​​of the difference into the forward and reverse control signals of the drive motor 1;

[0056] S4, after the driving motor 1 receives the forward and reverse control signal, it generates a rotational motion, and drives the mold core support 7 to rotate in a positive or reverse direction through the power output hollow shaft 3, thereby generating a displacement of forward movement or backward movement, and realizing the self-adaptive adjustment of the melt pressure;

[0057] When the melt pressure is too high, the core support 7 is controlled by the above pressure regulation method to move backward, so that the volume of the co-extrusion cavity increases ( Figure 4 As shown), release the melt pressure; when the melt pressure is too small, the core support 7 is controlled by the above pressure adjustment method to move forward, so that the volume of the co-extrusion cavity is reduced ( Figure 5 to maintain the system pressure stable.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A pressure-adaptive multi-layer co-extrusion die head, characterized in that: It comprises a die head assembly, a mold core support (7), a core rod (22), and a driving system; A rear cover plate (19) is installed on the rear side of the head assembly; one end of the core support (7) is connected to the drive system, and the other end passes through the rear cover plate (19) and extends forward in the axial direction and is detachably connected to a core rod (22) arranged at the axis of the head assembly; a core support threaded plate (20) is fixedly arranged on the rear side of the rear cover plate (19), and the core support threaded plate (20) is sleeved on the core support (7) and is matched with the core support (7); The die assembly comprises a die body (16), a multi-layer melt channel (18), a core rod (22) and a die (10); the multi-layer melt channel is coaxially arranged in the die body (16) and sleeved on the core support (7) and the core rod (22); a front cover plate (14) is installed on the front side of the die body (16), and a die mounting part (11) and a die (10) are installed on the front side of the front cover plate (14); a co-extrusion cavity is provided between the front cover plate (14) and the core rod (22) and the die (10), and the discharge ports of the multi-layer melt channel are respectively connected to the co-extrusion cavity; a pressure sensor probe is provided in the co-extrusion cavity, and is an integrated structure with the melt pressure sensor (15) fixed on the front cover plate (14); The driving system comprises a controller and a power output hollow shaft (3), a reducer (2), and a driving motor (1) which are sequentially mounted on a tailstock (5); the tailstock (5) is slidably connected to a guide rail (4); the power output hollow shaft (3) is connected to a core support (7) via a connecting half shaft (6); the core support (7) can rotate and move forward and backward under the drive of the driving system, and at the same time, the volume of the co-extrusion cavity changes, thereby achieving pressure self-adaptation.

2. The pressure-adaptive multi-layer co-extrusion die head according to claim 1, characterized in that: The die mounting member (11) is sleeved with an adjustment screw cover plate (12) for pressing the die mounting member (11) onto the front cover plate (14) and adjusting the eccentricity of the die through a plurality of adjustment screws (13) distributed along the radial direction of the front cover plate.

3. The pressure-adaptive multi-layer co-extrusion die head according to claim 1 or 2, characterized in that: A thermocouple (17) is arranged on the machine head body (16).

4. The pressure-adaptive multi-layer co-extrusion die head according to any one of claims 1 to 3, characterized in that: The core support threaded plate (20) and the rear cover plate (19) are fixedly connected by fastening screws (21).

5. The pressure-adaptive multi-layer co-extrusion die head according to any one of claims 1 to 4, characterized in that: The core support (7) and the core rod (22) are detachably connected via threads.

6. The pressure-adaptive multi-layer co-extrusion die head according to any one of claims 1 to 5, characterized in that: The connection between the core support thread plate (20) and the core support (7) is threaded connection or ball screw connection.

7. The pressure-adaptive multi-layer co-extrusion die head according to any one of claims 1 to 6, characterized in that: The connecting half shaft (6) and the mold core bracket (7) are rigidly connected via a coupling.

8. The pressure-adaptive multi-layer co-extrusion die head according to any one of claims 1 to 7, characterized in that: The guide rail (4) is fixedly mounted on the mold body (9); and the head assembly is mounted on the mold body (9) via a support rod (8).

9. The pressure-adaptive multi-layer co-extrusion die head according to any one of claims 1 to 8, characterized in that: The controller is connected to the melt pressure sensor (15) and the drive motor via electrical signals.

10. A pressure regulating method for a pressure-adaptive multi-layer co-extrusion die head according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. After the machine is initialized, input the melt pressure setting value according to the extrusion conditions; S2. During the production process, the melt pressure sensor (15) collects the melt pressure signal in the current co-extrusion cavity in real time and converts it into a voltage or current signal to be recognized by the controller; S3, the controller compares the melt pressure collected value with the set value to obtain a difference, and converts the positive and negative values ​​of the difference into a forward and reverse control signal of the drive motor (1); S4, after receiving the forward and reverse control signal, the driving motor (1) generates a rotational motion, and drives the mold core support (7) to rotate in a forward or reverse direction through the power output hollow shaft (3), thereby generating a forward or backward displacement, and realizing the self-adaptive adjustment of the melt pressure; Preferably, when the melt pressure is too high, the above pressure regulating method controls the core support (7) to move backward, thereby increasing the volume of the co-extrusion cavity and releasing the melt pressure; when the melt pressure is too low, the above pressure regulating method controls the core support (7) to move forward, thereby reducing the volume of the co-extrusion cavity and maintaining the system pressure stable.

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