A communicating extrusion screw and an extruder

Abstract

The embodiment of the application provides a communicating extrusion screw and an extruder, the screw rod comprises a rod body, screw ridges and a fractal communicating structure, the fractal communicating structure penetrates between the screw ridges; the fractal communicating structure is formed into a hollow rod shape by an external fractal wall and an internal communicating channel; the fractal communicating structure is a structure formed according to the self-similarity principle and the iteration generation principle of fractal theory and recursion by using the principle of Koch curve, strong shear strengthening melting and dispersion processes are provided through the fractal communicating structure, and precise distribution of the same screw groove, front and rear screw grooves and interphase screw grooves can be realized, so that the distribution and mixing capacity of the material is improved; the problem of unmelted material aggregation and easy dispersion phase agglomeration caused by the lack of mutual intersection of materials between interphase screw grooves due to the fact that the traditional screw rod can only make the mutual intersection of materials in adjacent screw grooves through the slotting form of the screw ridge is avoided.

Description

Technical Field

[0001] This application relates to a connected extrusion screw and an extruder. Background Technology

[0002] Extrusion molding equipment is used to mix two or more phases uniformly. The screw is a key component in extrusion molding equipment, affecting the performance of the extruded product. Traditional extrusion equipment typically includes single-screw, twin-screw, and multi-screw extruders. Twin-screw and multi-screw extruders are further divided into fully meshing, partially meshing, and non-meshing types. Among them, single-screw, partially meshing, and non-meshing twin-screw and multi-screw extruders mainly rely on friction conveying. Traditional single-screw extruders have a simple structure, low processing cost, and high production efficiency, but their mixing capacity is relatively weak. To enhance their mixing performance, methods such as adding pin structures, adding secondary screw ribs, and slotting screw ribs are usually used to break up the solid bed in the screw channel, allowing the unmelted glassy state to fully contact the melt, increasing melting efficiency; changing the material flow path, thereby promoting the distribution and mixing capacity; however, the friction conveying of the screw makes the materials in the front and rear screw channels relatively independent, which cannot fundamentally solve the problem of dispersed phase agglomeration and makes it difficult to improve the material distribution and mixing capacity. Summary of the Invention

[0003] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0004] The purpose of this application is to at least partially solve one of the technical problems existing in the related art. The embodiments of this application provide a connected extrusion screw and extruder, which provides a strong shear-enhanced melting and dispersion process through a fractal connected structure.

[0005] An embodiment of the first aspect of this application provides a connected extrusion screw, comprising: a rod body, helical ridges, and a fractal connecting structure. The helical ridges are arranged around the rod body and form a spiral shape, and the fractal connecting structure extends through the helical ridges. The fractal connecting structure is formed into a hollow rod shape by an outer fractal wall and an inner connecting channel. The outer edge of the transverse cross section of the fractal wall and the outer edge of the transverse cross section of the connecting channel are as follows: composed of a first line segment, multiple second line segments, and multiple third line segments. The multiple second line segments and multiple third line segments form a Koch curve. The first line segment is connected to the Koch curve. The multiple second line segments form multiple outwardly protruding regular polygons. The multiple third line segments form an inwardly concave shape. Four adjacent second line segments form a shape where the first and last second line segments are on the same straight line and the middle second line segment forms an inwardly equilateral triangle. Four adjacent third line segments form a shape where the first and last third line segments are on the same straight line and the middle third line segment forms an inwardly equilateral triangle.

[0006] According to certain embodiments of the first aspect of this application, when The fractal connection structure is connected in the front and rear screw grooves or in alternating screw grooves; when The fractal connection structure is connected in two screw grooves that are n screw grooves apart or in two screw grooves that are n+1 screw grooves apart; where L is the length of the fractal connection structure, s is the pitch between adjacent screw edges, and e is the width of the screw edge.

[0007] According to certain embodiments of the first aspect of this application, the ratio of the area enclosed by the outer edge of the transverse section of the fractal wall to the area enclosed by the outer edge of the transverse section of the connecting channel ranges from 1:0.5 to 1:0.8.

[0008] According to certain embodiments of the first aspect of this application, the connection portion between the fractal connecting structure and the helical ridge is cylindrical.

[0009] According to certain embodiments of the first aspect of this application, the maximum width of the fractal wall is less than or equal to the maximum width of the fractal connected structure.

[0010] According to certain embodiments of the first aspect of this application, when the fractal connection structure is installed on a single screw or a non-meshing twin screw, the distance between the center of the fractal connection structure and the center of the screw satisfies the following relationship: The included angle between the centers of adjacent fractal connected structures satisfies the following relationship: ;in, ; This represents the maximum dimension of the connecting channel in the width direction. The number of layers of the fractal connected structure on the spiral edge. The distance between the center of the fractal connected structure and the center of the screw. denoted as the included angle between the centers of adjacent fractal connected structures, d is the inner diameter of the screw, D is the outer diameter of the screw, and h is the screw groove depth.

[0011] According to certain embodiments of the first aspect of this application, the through holes on the helical ridge and the plurality of fractal interconnected structures form a disturbance structure group, wherein the plurality of fractal interconnected structures in the disturbance structure group are staggered.

[0012] According to certain embodiments of the first aspect of this application, adjacent groups of disturbance structures are circumferentially distributed around the axis of the rod.

[0013] According to certain embodiments of the first aspect of this application, when the fractal connection structure is installed on a partially meshing twin screw, the distance between the center of the fractal connection structure and the center of the screw satisfies the following relationship: The included angle between the centers of adjacent fractal connected structures satisfies the following relationship: ;in, , ; This represents the maximum dimension of the connecting channel in the width direction. The number of layers of the fractal connected structure on the spiral edge. The distance between the center of the fractal connected structure and the center of the screw. denoted as the included angle between the centers of adjacent fractal connected structures, d is the inner diameter of the screw, D is the outer diameter of the screw, and C is the center distance of the partially meshing twin screw.

[0014] According to a second aspect of this application, an extruder includes a barrel and a communicating extrusion screw as described above, the communicating extrusion screw being disposed within the barrel; the extruder includes a conveying section, a melting section, and a homogenizing section, with a fractal communicating structure located at the ends of the melting section and the homogenizing section of the communicating extrusion screw.

[0015] The above-mentioned solution has at least the following beneficial effects: it provides strong shear enhancement for melting and dispersion processes through fractal interconnection structure, and enables precise flow separation between the same screw channel, front and rear screw channels, and alternating screw channels, thereby improving the material distribution and mixing capacity; it avoids the problem of unmelted material agglomeration and easy dispersion phase aggregation caused by the lack of material interaction between alternating screw channels due to the fact that traditional single screw, partially meshing and non-meshing twin screws can only achieve mutual interaction of materials in adjacent screw channels through screw ridge slotting. Attached Figure Description

[0016] The accompanying drawings are used to provide a further understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0017] Figure 1 This is a structural diagram of the extruder provided in an embodiment of this application;

[0018] Figure 2 This is a structural diagram of the interconnected extrusion screw provided in an embodiment of this application;

[0019] Figure 3 This is a structural diagram of a fractal connected structure;

[0020] Figure 4 This is a partial structural diagram of a fractal connected structure;

[0021] Figure 5 This is a cross-sectional view of a fractal connected structure;

[0022] Figure 6 This is a structural diagram of a single screw with a fractal interconnect structure installed.

[0023] Figure 7 This is a structural diagram of a single screw with a fractal interconnect structure installed in another direction;

[0024] Figure 8 This is a schematic diagram of the material flow direction of a single screw with a fractal interconnection structure installed.

[0025] Figure 9 This is a top view of a partially meshing twin-screw screw with a fractal interconnect structure installed.

[0026] Figure 10 It is a side view of a partially meshing twin screw with a fractal interconnect structure installed;

[0027] Figure 11 It is a three-dimensional view of a partially meshing twin-screw screw with a fractal interconnect structure installed;

[0028] Figure 12 This is a schematic diagram of the material flow direction of a partially meshing twin-screw extruder with a fractal interconnection structure. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, or the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0031] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0032] An embodiment of this application provides an extruder.

[0033] Reference Figure 1 An extruder includes a barrel and a connected extrusion screw, with the connected extrusion screw housed within the barrel. The barrel has a feed inlet 1. The extruder includes a conveying section, a melting section, and a homogenizing section. A fractal connecting structure is located at the end of the melting section and the homogenizing section of the connected extrusion screw. The fractal connecting structure is perpendicular to the screw ridge 2 or forms a certain angle with the screw ridge 2.

[0034] During polymer processing, the glassy material enters the screw channel 5 from the feed inlet 1. Under the action of heating in the barrel and heat dissipation due to viscosity, it becomes a highly elastic state and then transforms into a viscous flow state.

[0035] Reference Figure 2For a connected extrusion screw, the screw includes: a rod body, a screw ridge 2, and a fractal connecting structure. The screw ridge 2 is arranged around the rod body and forms a spiral shape, and the fractal connecting structure runs through the screw ridge 2. The fractal connecting structure is formed into a hollow rod shape by an outer fractal wall 3 and an inner connecting channel 4.

[0036] Reference Figure 4 and Figure 5 Based on the self-similarity principle and iterative generation principle of fractal theory, and using the Koch curve principle of typical theory for recursion, the shapes of the outer edges of the transverse cross section of fractal wall 3 and the outer edges of the transverse cross section of connecting channel 4 can be obtained.

[0037] The outer edges of the transverse cross-section of the fractal wall 3 and the transverse cross-section of the connecting channel 4 are as follows: They consist of a first line segment, multiple second line segments, and multiple third line segments. The multiple second and third line segments form a Koch curve. The first line segment connects to the Koch curve. The multiple second line segments form multiple outwardly protruding regular polygons. The multiple third line segments form an inwardly concave shape. Four adjacent second line segments form a shape where the first and last second line segments are on the same straight line, and the middle second line segment forms an inwardly equilateral triangle. Similarly, four adjacent third line segments form a shape where the first and last third line segments are on the same straight line, and the middle third line segment forms an inwardly equilateral triangle. The length of the first line segment is L0, the length of the second line segment is L1, and the length of the third line segment is L2.

[0038] Given a basic geometric line segment, taking a straight line as an example, the segments at one-third and two-thirds of their length are used as base points to fold outwards, merging to form a small equilateral triangle. The length of the folded side is one-third of the original side. By continuing this method indefinitely, the Koch curve is formed. Similarly, the sides of a regular polygon are folded in the same way. The difference is that in this embodiment, the one-third point of each side is not simply folded, but the one-third and two-thirds points are used as the two base points of the new regular polygon, folding outwards to form a small regular polygon. After two recursive folding cycles, and by reasonably arranging and discarding some line segments, the shape of the outer edge of the transverse section of the fractal wall 3 and the outer edge of the transverse section of the connecting channel 4 can be obtained.

[0039] In this embodiment, a fractal interconnected structure provides strong shear enhancement for melting and dispersion processes, and enables precise flow separation between the same screw channel, front and rear screw channels, and alternating screw channels, thereby improving the material distribution and mixing capabilities. This avoids the problem of unmelted material agglomeration and dispersion phase aggregation caused by the lack of material exchange between alternating screw channels in traditional single-screw, partially meshing, and non-meshing twin-screw extruders, which can only achieve material exchange between adjacent screw channels through screw ridge slotting.

[0040] The ratio of the area enclosed by the outer edge of the transverse section of the fractal wall 3 to the area enclosed by the outer edge of the transverse section of the connecting channel 4 is in the range of 1:0.5 to 1:0.8.

[0041] Channel 4 runs through the entire fractal connected structure, and the length of channel 4 is the same as the length of the fractal connected structure.

[0042] Reference Figure 3 The connection between the fractal connected structure and the spiral edge 2 is a cylindrical shape with a diameter of B; the part of the fractal connected structure between the spiral edges 2 adopts a fractal wall structure. Therefore, the diameters of the fractal wall 3 and the cylindrical part of the fractal connected structure are different. Furthermore, the maximum width B2 of the fractal wall 3 is less than or equal to the maximum width B1 of the fractal connected structure.

[0043] The length of the fractal connection structure is L, the pitch between adjacent screw ridges 2 is s, and the width of screw ridge 2 is e. When L=0, that is, no fractal connection structure is set, and a circular hole is directly opened on the screw ridge 2, the material flows through the circular hole and is subjected to the pressure in the extrusion direction, flowing through the circular hole to the next screw groove 5, realizing the convergence of materials in the front and rear screw grooves 5. When the length of the fractal connection structure satisfies When material flows through the fractal interconnected structure, because the fractal interconnected structure is perpendicular to the flow direction or forms a certain angle, it changes the flow direction of the material, increasing the disturbance of the flow path. Simultaneously, under the pressure of the extrusion direction, it also achieves the connection between the two front and rear screw channels 5 or the alternating screw channels 5. Furthermore, the material is subjected to strong shearing under the influence of the fractal structure, which is beneficial for improving dispersion and mixing capabilities. When the length of the fractal interconnected structure meets the requirements... The fractal connection structure connects two screw grooves 5 that are n screw grooves apart or two screw grooves 5 that are n+1 screw grooves apart, so as to realize the connection of materials in two screw grooves 5 that are n screw grooves apart or two screw grooves 5 that are n+1 screw grooves apart.

[0044] Reference Figure 6 , Figure 7 and Figure 8 When a fractal connection structure is installed on a single screw or a non-meshing twin screw, the fractal connection structure has the following characteristics, and the distance between the center of the fractal connection structure and the center of the screw satisfies the following relationship: The included angle between the centers of adjacent fractal connected structures satisfies the following relationship: ;in, ; This represents the maximum dimension of the connecting channel in the width direction. The number of layers of the fractal connected structure on the spiral edge 2. The distance between the center of the fractal connected structure and the center of the screw. denoted as the included angle between the centers of adjacent fractal connected structures, d is the inner diameter of the screw, D is the outer diameter of the screw, and h is the screw groove depth.

[0045] In the screw channel of a single screw or a non-meshing twin screw, material conveying is achieved through friction conveying. When material flows through the screw channel 5, fractal walls 311, 312, 314, 315, and 316 are perpendicular to or at an angle to the direction of material movement. Under the action of fractal wall 311, the material is divided into two parts, flowing through the next part of fractal walls 312 and 314, where the two parts partially converge. The material fluid is then divided into three parts and flows through the gaps between fractal walls 315 and 316. After undergoing multiple fractal structures, the material fluid continuously separates and converges, eventually mixing evenly. The unmelted glassy material, under the disturbance of fractal wall 3, increases the contact area and frequency with the externally heated inner wall of the barrel and the molten pool, thereby improving the melting efficiency of the material. The strong shearing action of fractal wall 3 further enhances the dispersion and mixing efficiency. The fractal wall 3 has irregular gaps and boundaries, which can provide more shear surfaces and flow dividers, interfere with and prevent the single flow of some incompletely fused and homogeneous materials, promote the further fusion of incompletely fused materials, increase the randomness of the material flow in the screw channel 5, and its disturbance effect improves the mixing ability of the material, so that the degree of mixing of the material is further improved. At the same time, it disperses and promotes the continuous transfer of the material on the path, so that the material continuously rubs against the various surfaces of the fractal structure, causing the pulling and aggregation between the materials and the frictional heat generated between the material and the contact surface of the fractal wall 3, further improving the melting rate. Meanwhile, part of the material in the screw groove 511 flows through connecting channels 411, 413, and 415 and is transported to the alternating screw grooves 513; part flows through the through holes between the screw ribs 2 and moves to the adjacent screw groove 512; and part flows through connecting channels 412 and 414 and moves to the separated screw grooves 514. This realizes the flow of fluid material in screw grooves 511, 512, 513, and 514. Furthermore, the material flows from the center of one screw groove to another screw groove, close to the inner wall of the barrel or the screw wall, thus realizing the tumbling of the material in the screw groove 5 and achieving the uniform distribution of the processing fluid.

[0046] Fractal interconnected structures and through holes form a disturbance structure group. Multiple fractal interconnected structures within the disturbance structure group are circumferentially staggered to facilitate the dispersion and mixing of materials between the screw channels. The position of the through holes is not specifically required. Adjacent disturbance structure groups are circumferentially distributed around the screw axis. To allow material flow between different screw channels, adjacent disturbance structure groups are circumferentially distributed around the screw axis at 90-degree angles, meaning four groups of fractal interconnected disturbance structure groups are arranged within a 360-degree circumferential range of each screw channel. There should be approximately twenty fractal interconnected structures within the same screw channel. To ensure the fractal structures effectively disturb the flowing material within the screw channels, the arrangement of the structures should not be too few or too loose; the specific number and distribution of the fractal interconnected structures can be adjusted according to actual conditions.

[0047] Reference Figure 9 , Figure 10 , Figure 11 and Figure 12 When a fractal connection structure is installed on a partially meshing twin-screw, the fractal connection structure has the following characteristics, and the distance between the center of the fractal connection structure and the center of the screw satisfies the following relationship: The included angle between the centers of adjacent fractal connected structures satisfies the following relationship: ;in, , ; This represents the maximum dimension of the connecting channel in the width direction. The number of layers of the fractal connected structure on the spiral edge 2. The distance between the center of the fractal connected structure and the center of the screw. θ is the included angle between the centers of adjacent fractal connected structures, d is the inner diameter of the screw, D is the outer diameter of the screw, and C is the center distance of the partially meshing twin screw.

[0048] In the screw channels of a partially meshing twin-screw extruder, material conveying is achieved through friction conveying. For example, the first screw 611 and the second screw 612 form a partially meshing twin-screw extruder structure with co-directional meshing. During the rotation cycle of the first screw 611 and the second screw 612, the material flows through the high-shear gap zone of the partially meshing twin-screw extruder multiple times, improving dispersion and mixing performance. Both the first screw 611 and the second screw 612 are equipped with fractal walls 3 and connecting channels 4. The material flows in the same direction in both the first screw 611 and the second screw 612. The fractal walls 3 are perpendicular to the direction of material movement or form a certain angle with the direction of movement. As the material flows through the screw groove 5, it is diverted by the fractal wall 3111. Part of the material flows to the lower fractal walls 3121 and 3141, while another part flows away from the screw groove. The material flowing towards the fractal walls 3121 and 3141 is further divided into three parts and flows into the gap between the fractal walls 3151 and 3161, where it is further diverted. Part of the material flows to the lower fractal wall 3, and another part flows away from the screw groove. As the partially meshing twin screws rotate, the material on the first screw 611 and the second screw 612 intersects, and after passing through the fractal walls 3 multiple times, the fluid continuously separates and intersects, eventually mixing evenly. Meanwhile, part of the material in the screw groove 5111 flows through the connecting channels 4111, 4131, and 4151 and is transported to the alternating screw grooves 5131; part flows through the through holes between the screw ribs 2 and moves to the adjacent screw groove 5121; and part flows through the connecting channels 4121 and 4141 and moves to the screw grooves 5141 spaced apart. This achieves the flow of fluid in the screw grooves 5111, 5121, 5131, and 5141. Furthermore, the material flows from the center of one screw groove to another screw groove near the inner wall of the barrel or the screw wall, achieving the tumbling of the material in the screw groove and thus achieving the uniform distribution of the processing fluid.

[0049] It is understandable that for partially meshing twin-screw screws, the first screw 611 and the second screw 612 are partially meshed, but not completely meshed.

[0050] In summary, by setting fractal walls 3 perpendicular to or at a certain angle to the friction conveying direction between the screw channels 5, the material is subjected to strong shearing when it flows through the fractal walls 3, which helps to disperse and mix the material in the screw channels 5. When the material flows through the gaps in the fractal walls 3, it enables the material to split into two, four, and two and then merge during the conveying process. The fluid's distribution and mixing capacity is improved during the continuous separation and merging process. The fractal connecting structure with a connecting function is set in the screw channels 5, which causes the incompletely melted material to be constantly disturbed, thereby increasing the heat conduction area with the outer wall of the barrel and promoting the melting of the material. By setting the connecting channel 4, the material in the center of the screw channel in the original laminar flow process is directed to the inner wall of the barrel between the screw channels 5 or adjacent screw channels 5, realizing the precise flow and merging of the material at any position of adjacent screws 5 or between screw channels 5, breaking the mixing dead zone in traditional laminar flow mixing and increasing the distribution and mixing capacity.

[0051] The above is a detailed description of the preferred embodiments of this application, but this application is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A continuous extrusion screw, characterized in that, include: A rod body, helical ridges, and a fractal connecting structure, wherein the helical ridges are arranged around the rod body and form a spiral shape, and the fractal connecting structure passes through the helical ridges; The fractal interconnected structure is formed by an outer fractal wall and an inner connecting channel, creating a hollow rod shape. The outer edges of the transverse cross-section of the fractal wall and the transverse cross-section of the connecting channel are as follows: composed of a first line segment, multiple second line segments, and multiple third line segments. The multiple second line segments and multiple third line segments form a Koch curve. The first line segment is connected to the Koch curve. The multiple second line segments form multiple outwardly protruding regular polygons. The multiple third line segments form an inwardly concave shape. Four adjacent second line segments form a shape where the first and last second line segments are on the same straight line and the middle second line segment forms an inwardly equilateral triangle. Four adjacent third line segments form a shape where the first and last third line segments are on the same straight line and the middle third line segment forms an inwardly equilateral triangle. The ratio of the area enclosed by the outer edge of the transverse section of the fractal wall to the area enclosed by the outer edge of the transverse section of the connecting channel is in the range of 1:0.5 to 1:0.

8. The through holes on the spiral ridge and the multiple fractal interconnected structures form a disturbance structure group, in which the multiple fractal interconnected structures are staggered.

2. The interconnected extrusion screw according to claim 1, characterized in that, when The fractal connection structure is connected in the front and rear screw grooves or in alternating screw grooves; when The fractal connection structure is connected in two screw grooves that are n screw grooves apart or in two screw grooves that are n+1 screw grooves apart; where L is the length of the fractal connection structure, s is the pitch between adjacent screw edges, and e is the width of the screw edge.

3. The interconnected extrusion screw according to claim 1, characterized in that, The connection between the fractal connecting structure and the spiral edge is cylindrical.

4. The interconnected extrusion screw according to claim 1, characterized in that, The maximum width of the fractal wall is less than or equal to the maximum width of the fractal connected structure.

5. A connected extrusion screw according to claim 1, characterized in that, When the fractal connection structure is installed on a single screw or a non-meshing twin screw, the distance between the center of the fractal connection structure and the center of the screw satisfies the following relationship: The included angle between the centers of adjacent fractal connected structures satisfies the following relationship: ;in, ; This represents the maximum dimension of the connecting channel in the width direction. The number of layers of the fractal connected structure on the spiral edge. The distance between the center of the fractal connected structure and the center of the screw. denoted as the included angle between the centers of adjacent fractal connected structures, d is the inner diameter of the screw, D is the outer diameter of the screw, and h is the screw groove depth.

6. A connected extrusion screw according to claim 1, characterized in that, Adjacent disturbance structure groups are circumferentially distributed around the axis of the rod.

7. A connected extrusion screw according to claim 1, characterized in that, When the fractal connection structure is installed on a partially meshing twin screw, the distance between the center of the fractal connection structure and the center of the screw satisfies the following relationship: The included angle between the centers of adjacent fractal connected structures satisfies the following relationship: ;in, , ; This represents the maximum dimension of the connecting channel in the width direction. The number of layers of the fractal connected structure on the spiral edge. The distance between the center of the fractal connected structure and the center of the screw. denoted as the included angle between the centers of adjacent fractal connected structures, d is the inner diameter of the screw, D is the outer diameter of the screw, and C is the center distance of the partially meshing twin screw.

8. An extruder, characterized in that, The extruder includes a barrel and a connected extrusion screw as described in any one of claims 1 to 7, wherein the connected extrusion screw is disposed within the barrel; the extruder includes a conveying section, a melting section, and a homogenizing section, and the fractal connecting structure is located at the end of the melting section and the homogenizing section of the connected extrusion screw.

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