A 3D printing head structure that can be used to prepare variable-component composite materials

Abstract

A 3D printing head structure that can be used to prepare variable-component composite materials includes: a single-screw extrusion structure with an extrusion screw and an extrusion barrel, at least two material storage barrels with adjustable material delivery information, a nozzle located below the extruder barrel, and a cooling device and a heating device spaced apart on the periphery of the extruder barrel. The extrusion screw is divided from top to bottom into a solid mixing section, a feeding section, a compression section, and a metering section; a tapered screw flight, a first blade, and a second blade are spaced apart on the periphery of the main body of the solid mixing section; the radial dimension of the tapered screw flight gradually decreases along the axial transmission direction; the blade rotation diameter of the first blade is greater than the maximum radial dimension of the tapered screw flight; the blade rotation diameter of the second blade is less than the minimum radial dimension of the tapered screw flight; and the cooling device is located above the heating device. This structure is used in 3D printing to deposit material components of different proportions online, enabling continuous printing of variable-component composite materials and ensuring that different locations on the same part have the desired performance.

Description

Technical Field

[0001] The present disclosure relates to the field of 3D printing technology, and in particular to a 3D printing head structure that can be used to prepare composite materials with variable components. Background Art

[0002] As product functionality and performance requirements continue to increase, a single homogeneous material can no longer meet application needs. Sometimes, different locations within the same component even need different functions or performance. To meet this demand, heterogeneous materials have emerged. This means that the same component is composed of different materials, and the performance requirements are met by regulating the distribution of these different materials.

[0003] 3D printing technology digitally deposits materials point by point and layer by layer. Theoretically, it can easily produce heterogeneous materials by controlling the ratios of different components in the raw materials, and has therefore attracted widespread attention. However, the most widely used 3D printing technology currently is fused filament printing (FFF), which uses polymer-based composite materials as raw materials. This method requires the polymer composites to be pre-prepared as filaments. This method cannot deposit specific materials in specific areas, and it suffers from long cycles, high costs, and difficulty in combining and regulating different material components within a specific area.

[0004] In recent years, screw extrusion 3D printers have emerged, which integrate screw extrusion heads into 3D printers. However, the performance of current screw extrusion 3D printers in printing multi-component variable material mixtures still needs to be improved. For example, when using a single-screw extrusion 3D printer to print a variety of materials in powder form, the multi-component material mixing effect is poor, and it is difficult to control the material components online in real time. As a result, the performance qualification rate of the printed products is low. Summary of the Invention

[0005] In order to improve the online printing effect of multi-component materials, some embodiments of the present disclosure provide a 3D printing head structure that can be used for preparing variable-component composite materials.

[0006] Some embodiments of the present disclosure provide a 3D printing head structure that can be used to prepare a variable-component composite material, the 3D printing head structure comprising: a single-screw extrusion structure, at least two material storage barrels with adjustable material delivery information, a nozzle, a cooling device, and a heating device;

[0007] The single-screw extrusion structure comprises: an extrusion screw and an extrusion barrel, wherein the extrusion barrel is located on the periphery of the extrusion screw and has an accommodating space between the extrusion screw and the extrusion screw; the extrusion screw is divided from top to bottom into a solid mixing section, a feeding section, a compression section, and a metering section; the main body of the solid mixing section is provided with: a conical screw flight, a first blade, and a second blade; the radial dimension of the conical screw flight gradually decreases along the axial transmission direction; the blade rotation diameter of the first blade is greater than the maximum radial dimension of the conical screw flight; and the blade rotation diameter of the second blade is less than the minimum radial dimension of the conical screw flight;

[0008] The storage barrel is distributed on the top of the extruder barrel, and the material output port of the storage barrel is used to output the material in the form of powder or granules to the accommodating space;

[0009] The nozzle is arranged at the bottom of the extruder barrel;

[0010] The cooling device and the heating device are arranged at intervals on the periphery of the extruder barrel, and the cooling device is located above the heating device.

[0011] In some embodiments, the radial dimension of the conical screw ridge can vary within 10 mm to 100 mm; the number of the first blades is multiple, and the multiple first blades are distributed from top to bottom along the axial direction, and the blade rotation diameters of the multiple first blades gradually decrease along the axial direction; the number of the second blades is multiple, and the multiple second blades are arranged from top to bottom along the axial direction and distributed in the gaps of the conical screw ridge.

[0012] In some embodiments, the blade rotation diameter of the first blade is 20 mm to 40 mm; the blade rotation diameter of the second blade is 6 mm to 18 mm; and the radial dimension of the conical screw fin is 10 mm to 30 mm.

[0013] In some embodiments, pins for homogenizing melt mixing are distributed around the periphery of the main body of the metering section, and the height of the pins does not exceed the screw groove depth or screw thread height of the metering section;

[0014] The cross-sectional shape of the pin includes one or more of the following combinations: oval, circular, semicircular, sawtooth, and polygonal including triangle.

[0015] In some embodiments, the cross-sectional diameter or cross-sectional side length of the pin is 0.3 mm to 1 mm;

[0016] The spacing between the pins is 3mm to 10mm;

[0017] The height of the pin is 1mm to 2mm;

[0018] The number of the pins distributed along the circumference of the extrusion screw is 6 to 20.

[0019] In some embodiments, the length ratios of the solid mixing section, the feeding section, the compression section, and the metering section are 4:4:3:3.

[0020] In some embodiments, the screw groove depth of the feeding section is 2 mm to 4 mm, and the screw groove depth of the metering section is 1 mm to 2 mm.

[0021] In some embodiments, the diameter of the extrusion screw is 8 mm to 20 mm, the aspect ratio (the ratio of the length of the working part of the screw (the length of the threaded part) to the screw diameter is called the aspect ratio) is 8:1 to 10:1, and the compression ratio is 2 to 4;

[0022] The portion of the extruder barrel that matches the solid mixing section is funnel-shaped, and the portion of the extruder barrel that matches the feeding section, the compression section, and the metering section is straight-cylinder-shaped;

[0023] The inner diameter of the straight cylindrical portion of the extruder barrel is 8.2 mm to 20.2 mm, and the outer diameter is 15 mm to 30 mm.

[0024] In some embodiments, the extrusion screw and the extruder barrel are both prepared by 3D printing process;

[0025] The extrusion screw and the extruder barrel are made of stainless steel or die steel.

[0026] In some embodiments, the extrusion screw is used to rotate under the driving action of a driving member; the cooling device is a power-adjustable air-cooling device or a water-cooling device, and the air-cooling device or the water-cooling device is used to determine the target heat dissipation rate according to the temperature of the heating device, and the target heat dissipation rate is used to prevent the solid material in the solid mixing section and the feeding section from agglomerating due to heating by the heating device below, and to protect the driving member from damage by high temperature.

[0027] Compared with the related art, the technical solution provided by the embodiments of the present disclosure has at least the following technical effects:

[0028] By arranging conical screw fins, first blades and second blades at intervals on the periphery of the main body of the extrusion screw in the solid mixing section, the radial size of the conical screw fins gradually decreases along the axial transmission direction, the blade rotation diameter of the first blade is greater than the maximum radial size of the conical screw fins, and the blade rotation diameter of the second blade is less than the minimum radial size of the conical screw fins. The arrangement of the first blade is conducive to the full stirring and mixing of the object material, and the arrangement of the conical screw fins is conducive to the full stirring and mixing and axial transportation of the solid material. The cooperation of the first blade and the conical screw fins can form a gradient cutting force surface and mixing space during the material transmission process, thereby improving the adequacy of stirring and the mixing uniformity between at least two materials; the arrangement of the second blade can prevent part of the material from accumulating and remaining at the root of the screw during the mixing process, thereby improving the adequacy of the material mixing and ensuring the accuracy of the physical component distribution ratio transmitted to the feeding zone;

[0029] By arranging a cooling device and a heating device on the periphery of the extruder barrel, the heating device can change the melting characteristics of the material therein by heating, thereby achieving melt mixing or phase transition of the composite material, etc. The cooling device can prevent the solid material in the solid mixing section and the feeding section from agglomeration caused by the heating of the lower heating device, and can also protect the drive components used to drive the extrusion screw from damage by high temperature.

[0030] On this basis, the powder or granular materials in at least two storage barrels can be solid-state mixed, melted and homogenized through a single-screw extrusion structure, and multi-component materials with adjustable ratios can be printed through a nozzle. When applied to 3D printing, different ratios of material components can be deposited on demand through a single nozzle to achieve continuous printing of variable-component composite materials, so that different positions of the same part have different performance to meet special performance or functional requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0032] Figure 1 A schematic diagram of a 3D printing head structure provided in some embodiments of the present disclosure;

[0033] Figure 2 A schematic diagram of the structure of an extrusion screw provided in some embodiments of the present disclosure;

[0034] Figure 3 A partial enlarged view of the solid mixing section of an extrusion screw provided in some embodiments of the present disclosure;

[0035] Figure 4 A partial enlarged view of the metering section of an extrusion screw provided for some embodiments of the present disclosure; and

[0036] Figure 5 A flowchart of a method for parameter setting and optimization in a 3D printing head structure provided in some embodiments of the present disclosure. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the present disclosure more clear, the present disclosure will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present disclosure, rather than all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present disclosure without creative effort are intended to fall within the scope of protection of the present disclosure.

[0038] The terms used in the embodiments of the present disclosure are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. The singular forms "a," "an," "the," and "the" used in the embodiments of the present disclosure and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0039] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0040] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprising a" does not exclude the presence of other identical elements in the product or device comprising the element.

[0041] Some embodiments of the present disclosure provide a 3D printing head structure that can be used for the preparation of variable-component composite materials, the 3D printing head structure comprising: a single-screw extrusion structure, at least two storage barrels with adjustable material conveying information, a nozzle, a cooling device, and a heating device. The single-screw extrusion structure comprises an extrusion screw for extruding materials and an extruder barrel matched therewith, a plurality of storage barrels capable of quantitatively conveying materials are provided above the extruder barrel, a cooling device and a heating device are provided on the outer surface of the extruder barrel, and a nozzle is installed below the extruder barrel. The extrusion screw comprises a solid mixing section, a feeding section, a compression section, and a metering section; the solid mixing section is provided with a conical screw ridge, a first blade, and a second blade, the radial dimension of the conical screw ridge gradually decreases along the axial transmission direction; the blade rotation diameter of the first blade is greater than the maximum radial dimension of the conical screw ridge; the blade rotation diameter of the second blade is less than the minimum radial dimension of the conical screw ridge.

[0042] The term "variable component" herein may include the following: the composition type of the composite material components can be adjusted, or the ratio of the composite material components can be adjusted, or the composition type and ratio of the composite material components can be adjusted simultaneously. It should be understood that the axial transmission direction refers to the direction of material transport along the axial direction; for example, when the axis of the extrusion screw in the 3D print head structure is arranged in a vertical direction, the radial dimension of the tapered screw flight gradually decreases along the axial transmission direction, which means that the radial dimension of the tapered screw flight gradually decreases from top to bottom along the axial direction; if the placement and orientation of the 3D print head structure changes, the orientation corresponding to the axial transmission direction will also be adjusted accordingly.

[0043] The provision of the first blade facilitates the thorough mixing of physical materials, while the provision of the tapered screw fin facilitates the thorough mixing and axial transport of solid materials. The combination of the first blade and the tapered screw fin can form a gradient-type cutting force surface and mixing space during material transport, thereby improving the thoroughness of mixing and the uniformity of mixing between at least two materials. The provision of the second blade can prevent some materials from accumulating and remaining at the root of the screw during the mixing process, thereby improving the thoroughness of material mixing and ensuring the accuracy of the physical component ratio transmitted to the feeding zone. By providing a cooling device and a heating device on the periphery of the extruder barrel, the heating device can change the melting characteristics of the materials therein by heating, thereby achieving melt mixing of the composite material. The cooling device can prevent the solid materials in the solid mixing section and the feeding section from agglomeration caused by heating by the lower heating device, and can also simultaneously protect the drive components used to drive the extrusion screw from damage by high temperature. On this basis, the powder or granular materials in at least two storage barrels can be solid-state mixed, melted and homogenized through a single-screw extrusion structure, and multi-component composite materials with adjustable ratios can be printed through a nozzle. When applied to 3D printing, different ratios of material components can be deposited on demand through a single nozzle to achieve continuous printing of variable-component composite materials, so that different positions of the same part have different performances to meet special performance or functional requirements.

[0044] Optional embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0045] Figure 1 A schematic diagram of a 3D printing head structure provided in some embodiments of the present disclosure. Figure 2 A schematic diagram of the structure of an extrusion screw provided in some embodiments of the present disclosure.

[0046] Reference Figure 1 As shown, the 3D printhead structure provided by the embodiment of the present disclosure for preparing a composite material with variable composition includes: a single-screw extrusion structure 10, at least two material storage barrels 20 with adjustable material delivery information, a nozzle 50, a cooling device 30, and a heating device 40. The single-screw extrusion structure 10 includes: an extrusion screw 11 and an extruder barrel 12. This 3D printhead structure can be used to prepare composite materials with online adjustment of multiple components, achieving online and efficient composite extrusion of multiple powder or granular materials (as the components of the composite material).

[0047] Composite materials are new materials composed of two or more material components (referred to as components) with different chemical and physical properties in a designed form, proportion and distribution.

[0048] Combine Figure 1 and Figure 2As shown, the extruder barrel 12 is located outside the extrusion screw 11 and has an accommodating space 100 between it and the extrusion screw 11; the extrusion screw 11 is divided from top to bottom into a solid mixing section L0, a feeding section L1, a compression section L2 and a metering section L3. Figure 2 Schematically shows the main body 110 of the extrusion screw, and the outer periphery of the main body of the solid mixing section L0 is spaced apart with: conical screw fins 112, first blades 111 and second blades 113.

[0049] The storage barrel 20 is distributed on the top of the extruder barrel 12, and the material output port of the storage barrel 12 is used to output the material in powder or granular form to the accommodating space 100. For example, in some embodiments, the storage barrel 20 can be detachably mounted on the top of the extruder barrel 12.

[0050] The nozzle 50 is disposed at the bottom of the extruder barrel 12 .

[0051] The cooling device 30 and the heating device 40 are arranged at intervals on the periphery of the extruder barrel 12 , and the cooling device 30 is located above the heating device 40 .

[0052] Figure 3 A partially enlarged view of the solid mixing section of an extrusion screw provided in some embodiments of the present disclosure.

[0053] For example, refer to Figure 2 and Figure 3 As shown in the partially enlarged area C of the solid mixing section of the extrusion screw, the radial dimension of the conical screw flight 112 is along the axial transmission direction (eg Figure 3 The blade rotation diameter of the first blade 111 is larger than the maximum radial dimension of the conical spiral fin 112; the blade rotation diameter of the second blade 113 is smaller than the minimum radial dimension of the conical spiral fin 112.

[0054] The radial dimension of the conical screw fin is the radial dimension from the axis of the extrusion screw (e.g. Figure 3 The size of the screw edge (along the left and right directions of the paper) to the edge of the tapered screw ridge.

[0055] The blade rotation diameter of the first blade 111 or the second blade 112 refers to the size from the axis of the extrusion screw to the edge of the first blade or the second blade along the radial direction.

[0056] By arranging conical spiral ridges, first blades and second blades at intervals on the periphery of the main body of the solid mixing section, the radial dimension of the conical spiral ridges gradually decreases along the axial transmission direction, the blade rotation diameter of the first blade is greater than the maximum radial dimension of the conical spiral ridges, and the blade rotation diameter of the second blade is less than the minimum radial dimension of the conical spiral ridges. The setting of the first blade is conducive to the full stirring and mixing of object materials, and the setting of the conical spiral ridges is conducive to the full stirring and mixing and axial transportation of solid materials. The cooperation of the first blade and the conical spiral ridge can form a gradient cutting force surface and mixing space during the material transmission process, thereby improving the adequacy of stirring and the mixing uniformity between at least two materials; the setting of the second blade can prevent part of the material from accumulating and remaining at the root of the screw during the mixing process, thereby improving the mixing adequacy of the material and ensuring the accuracy of the physical component ratio transmitted to the feeding area (the area between the feeding section of the extrusion screw and the extruder barrel).

[0057] In some embodiments, the radial dimension of the tapered screw flight may vary within a range of 10 mm to 100 mm.

[0058] There are multiple first blades, which are distributed from top to bottom along the axial direction, and the blade rotation diameters of the multiple first blades gradually decrease along the axial direction; there are multiple second blades, which are arranged from top to bottom along the axial direction and distributed in the gaps of the conical spiral blades.

[0059] For example, Figure 3 The figure shows that on the periphery of the main body of the extrusion screw in the solid mixing section L0, there are three groups of first blades 111a, 111b and 111c distributed from top to bottom along the axial direction, and each group of first blades has three blades (a group of first blades contains at least two blades, and the angle, distribution position, distribution uniformity or unevenness between multiple blades can be adjusted. For example, three blades can be distributed at intervals of 120°). They are at different circumferential positions at the same axial position and are staggered with the conical spiral fins 112. The blade rotation diameter of each group of first blades decreases successively along the axial direction. For example, the relationship between the blade rotation diameters of each group of first blades is: the blade rotation diameter of the first group of first blades 111a> the blade rotation diameter of the second group of first blades 111b> the blade rotation diameter of the third group of first blades 111c.

[0060] In some embodiments, combined Figure 1 and Figure 2As shown, the portion of the extruder barrel 12 that mates with the solid mixing section L0 is funnel-shaped. This funnel-shaped portion 121 and the extrusion screw of the solid mixing section form a first accommodating space for accommodating materials output from the material output ports of at least two storage barrels 20. As the extrusion screw 11 rotates under the driving member, the first blade 111, the second blade 113, and the tapered screw flight 112 all rotate within this first accommodating space, stirring the various materials therein.

[0061] Combine Figure 1 and Figure 2 As shown, the portion of the extruder barrel 12 that matches the feeding section L1 , the compression section L2 and the metering section L3 is in a straight cylindrical shape, referred to as a straight cylindrical portion 122 .

[0062] The cooling device 30 is arranged between the extruder barrel corresponding to the solid mixing section and the heating device 40. For example, in some embodiments, the cooling device 30 can be arranged on the periphery of the extruder barrel corresponding to the feeding section; multiple heating devices 40 are distributed on the periphery of the extruder barrel corresponding to the compression section and the metering section.

[0063] In some embodiments, the extrusion screw is used to rotate under the driving action of a driving member; the cooling device 30 is a power-adjustable air-cooling device or a water-cooling device, and the air-cooling device or the water-cooling device is used to determine the target heat dissipation rate according to the temperature of the heating device, and the target heat dissipation rate is used to prevent the solid material in the solid mixing section and the feeding section from agglomerating due to heating by the heating device below, and to protect the driving member from damage by high temperature.

[0064] Heating device 40 is used to heat the mixed materials. For example, if at least two materials include component A and component B, 3D printing requires heating components A and B to produce a composite material. The specific temperature setting depends on the melting points and phase transition temperatures of components A and B, respectively. The heating temperature range of the heating device can be adjusted according to the specific composite material requirements. For example, heating device 40 can be copper, ceramic, or spring heating rings, with a number of 2 to 5. The printing temperature can be dynamically adjusted to maintain a stable extrusion flow rate based on the different composite material printing requirements.

[0065] When the heating device 40 heats the materials in the accommodating space of the placed area, the heat will be conducted upwards. In order to avoid the heat corresponding to the high temperature being conducted to the solid mixing section L0 and the feeding section L1, causing the various materials therein to agglomerate under high temperature conditions, thereby affecting the printing efficiency; at the same time, it can also protect the driving component used to drive the extrusion screw from being damaged by high temperature.

[0066] By arranging a cooling device and a heating device on the periphery of the extruder barrel, the heating device can change the melting characteristics of the material therein by heating, realize the melt mixing or phase transition of the composite material, etc. The cooling device can prevent the solid material in the solid mixing section and the feeding section from agglomerating due to the heating of the heating device below, and can also protect the driving parts used to drive the extrusion screw from high temperature damage.

[0067] In some embodiments, the aforementioned 3D printhead structure supports a compact and lightweight design due to its efficient mixing and excellent mixing uniformity. For example, in some embodiments, the extrusion screw has a diameter of 8 mm to 20 mm, an aspect ratio of 8:1 to 10:1, and a compression ratio of 2 to 4. This sizing facilitates rapid conversion of different material components during printing and reduces printhead inertia, thereby ensuring the machining accuracy of the 3D printhead structure.

[0068] The aspect ratio here refers to the ratio between the length of the working part of the extrusion screw (the length of the threaded part, which corresponds to the axial length of the tapered screw fins of the solid mixing section, the threads of the feeding section, the threads of the compression section and the threads of the metering section) and the diameter of the extrusion screw.

[0069] The compression ratio is the ratio of the volume of the first screw groove (corresponding to the tapered flight) to the volume of the last screw groove (corresponding to the metering section). The compression ratio significantly affects the density of the product and the ability to remove air from the material. It also affects the extruder's output and the mechanical strength of the screw.

[0070] This embodiment can obtain a lightweight print head by reducing the size of the extrusion screw and the extruder barrel. While ensuring printing accuracy, it can also achieve rapid switching between different material components. For example, it can achieve printing switching of different component ratios of the same material components (for example, both components A and B) (for example, the ratio of components A and B is 1:5, or 2:4, etc.), and can obtain material components with different ratios by adjusting the material conveying speed of different storage barrels; or it can also achieve printing switching of composite materials corresponding to different material components (for example, one composite material is component A and component B; another composite material is component A and component C; and another composite material is component A, component B and component C). The switching and increase and decrease of material component types can be achieved by replacing the material in the storage barrel or adjusting the number of storage barrels to place new components; In addition, the material components of the composite material and the ratio of each component can also be controlled at the same time.

[0071] In some embodiments, the extrusion screw and the extrusion barrel are both prepared by 3D printing process;

[0072] The extrusion screw and the extruder barrel are made of stainless steel or die steel, such as but not limited to 316L, 304L, Cr12MoV, 38CrMoAlA, MS1, SKD61, DC53 and the like, which can achieve good thermal conductivity while ensuring long-term durability.

[0073] Figure 4 A partially enlarged view of the metering section of an extrusion screw provided for some embodiments of the present disclosure.

[0074] In some embodiments, reference Figure 4 As shown in the partially enlarged area D of the metering section of the extrusion screw, the periphery of the main body of the metering section L3 is distributed with pins 114 for melt mixing homogenization, and the height of the pins 114 does not exceed (≤) the screw groove depth or thread height of the metering section.

[0075] The cross-sectional shape of the pin includes but is not limited to a combination of one or more of the following shapes: oval, circular, semicircular, sawtooth, and polygonal including triangle.

[0076] By setting the pin, the flow direction of the melt (molten material) transmitted through the compression section can be forced to change, thereby achieving a better mixing effect. By setting the height of the pin lower than the depth of the screw groove of the metering section, interference with other positions of the extrusion screw can be avoided and the mixing effect can be ensured at the same time.

[0077] In some embodiments, the length ratio of the solid mixing section, the feeding section, the compression section, and the metering section is 4:4:3:3, that is, the lengths of the solid mixing section and the feeding section are equal.

[0078] In some embodiments, the blade rotation diameter of the first blade is 20 mm to 40 mm; the blade rotation diameter of the second blade is 6 mm to 18 mm; and the radial dimension of the conical screw fin is 10 mm to 30 mm.

[0079] In some embodiments, the cross-sectional diameter or side length of the pin is 0.3 mm to 1 mm; if the diameter or side length of the pin is too large, it will increase the resistance and be unfavorable for the transportation of the material; if the diameter or side length is too small, it will affect the mixing effect; by setting the cross-sectional diameter or side length of the pin within the range of this embodiment, the material transportation resistance and mixing effect can be taken into account and balanced during the material mixing process in the metering section.

[0080] In some embodiments, the spacing between the pins is 3 mm to 10 mm; too large a spacing affects the mixing effect, and too small a spacing affects the material conveying efficiency; by setting the pin spacing within the scope of this embodiment, it is possible to achieve a balance between material conveying efficiency and mixing effect during material mixing in the metering section.

[0081] In some embodiments, the height of the pin is 1 mm to 2 mm; if the pin height is too low, the material will be retained near the wall of the extruder barrel, affecting the mixing effect; if the pin height is too high, the material conveying resistance will increase; by setting the pin height within the range of this embodiment, the material conveying resistance and the mixing effect can be taken into account and balanced during the material mixing process in the metering section.

[0082] In some embodiments, the number of the pins distributed along the circumference of the extrusion screw is 6 to 20; the more the number of pins distributed in the circumferential direction, the better the mixing effect, but the corresponding material conveying efficiency is reduced; by setting the number of pins along the circumference within the scope of this embodiment, it is possible to achieve a balance between material conveying efficiency and mixing effect during material mixing in the metering section.

[0083] The above parameters of the pin can be determined by establishing a melt flow channel model and performing multiphase flow analysis using STAR-CCM+ (a simulation software based on continuum mechanics numerical technology) or Fluent-EDEM (a simulation software that can be used for particle flow simulation and calculation) coupling or Comsol (a general simulation software). The mixing effect of the material can be evaluated based on the distribution state of multiple components at the outlet cross section of the extruder barrel, and the parameters of the pin can be optimized and adjusted based on the mixing effect.

[0084] The portion of the extruder barrel that matches the solid mixing section is funnel-shaped, and the portions of the extruder barrel that match the feeding section, the compression section, and the metering section are straight-cylinder-shaped. In some embodiments, the inner diameter of the straight-cylinder portion of the extruder barrel is 8.2 mm to 20.2 mm, and the outer diameter is 15 mm to 30 mm.

[0085] The following describes the setting and optimization methods of various parameters of the 3D printing head structure.

[0086] Figure 5 A flowchart of a method for parameter setting and optimization in a 3D printing head structure provided in some embodiments of the present disclosure.

[0087] Reference Figure 5 As shown, the parameter setting and optimization method of the 3D printing head structure provided in this embodiment includes the following steps: S1, S2, S3, S4, S5, S6 and S7.

[0088] In step S1, the basic parameters of the extrusion screw are determined: based on the extrusion output and material conversion requirements, the diameter of the extrusion screw is preliminarily determined, for example, 10 mm to 20 mm, and then the length of each segment is determined (for example, the overall length is determined based on the aspect ratio of 8 / 1 or 9 / 1, and the length of each segment is determined based on the ratio of each segment) and the compression ratio and other parameters. Among them, the parameters of the extrusion screw include but are not limited to: the diameter of the extrusion screw, the aspect ratio, the length ratio of each segment, the screw groove depth, the pitch, the thread width (referring to the thread width corresponding to the feeding section, the compression section and the metering section, which can also be consistent with the description of the solid mixing section and called the screw flight width), etc.

[0089] In some embodiments, the extrusion screw diameter is 8 mm to 20 mm, which is beneficial for keeping the 3D printing head lightweight, improving molding accuracy and accelerating material conversion.

[0090] In some embodiments, the length L0 of the solid mixing section of the extrusion screw is the same as the length L1 of the feeding section, and the length ratio of the feeding section, compression section and metering section is 4:3:3, which is conducive to the transportation and melting of the material.

[0091] In some embodiments, the groove depth of the feeding section of the extrusion screw is 2 mm to 4 mm, which is beneficial to improving material conveying efficiency, and the groove depth of the metering section is 1 mm to 2 mm, which is beneficial to melting and mixing of materials.

[0092] In some embodiments, the inner diameter of the extruder barrel is 8.2 mm to 20.2 mm, and the outer diameter is 15 mm to 30 mm, so that the barrel is as light as possible to ensure forming accuracy.

[0093] In step S2, the parameters of the solid mixing section are determined: the sizes of the first blade and the second blade are preliminarily determined according to the size of the extrusion screw, and the screw fins of the solid mixing section are tapered.

[0094] For example, in some embodiments, the blade rotation diameter of the first blade decreases along the axial direction of the extrusion screw, preferably 20 mm to 40 mm, the blade rotation diameter of the second blade remains unchanged, preferably 6 mm to 18 mm, and the radial dimension of the conical screw fin is preferably 10 mm to 30 mm, thereby achieving online mixing of solid materials while ensuring the material conveying efficiency.

[0095] In step S3, analysis of the mixing effect of the solid mixing section: assemble the designed solid mixing section model and the extruder barrel model (wherein the parameters of the extruder barrel can be set according to the basic parameters of the extrusion screw and the space required by the material), and then import them into discrete element software such as EDEM for calculation, analyze the material distribution state at the outlet cross section of the solid mixing section, and evaluate the mixing effect of the solid mixing section.

[0096] In step S4, the mixing pin parameters are determined: the mixing pin size is determined according to the screw groove depth and pitch size of the metering section of the extrusion screw.

[0097] In some embodiments, the diameter d or side length of the mixing pin is 0.3 mm to 1 mm.

[0098] In some embodiments, the spacing between the mixing pins is 3 mm to 10 mm.

[0099] In some embodiments, the height of the mixing pins is 1 mm to 2 mm.

[0100] In some embodiments, the number of mixing pins distributed along the radial direction of the extrusion screw is 6 to 20.

[0101] S5. Melt mixing effect analysis: Establish a melt flow channel model, use STAR-CCM+ or Fluent-EDEM coupling or Comsol software to perform multiphase flow analysis, analyze the distribution state of multiple components at the exit section of the extruder barrel, and evaluate the mixing effect of the materials.

[0102] S6. Optimization of mixing structure parameters: According to the mixing effect of the solid material and the melt in S3 and S5, the parameters of the first blade, the second blade and the size parameters of the pin are adjusted respectively, and steps S2 and S4 are repeated respectively to obtain a structure with the best mixing effect, which is conducive to ensuring the mixing effect of multiple components and accelerating the material transformation response.

[0103] S7. Output the optimized barrel and screw model and prepare it.

[0104] After the parameter optimization of the above process, the 3D print head structure and the corresponding preferred parameters corresponding to the previous embodiment are obtained. After the 3D print head structure is made, the 3D print head structure can be used to efficiently mix, melt and extrude a variety of material components to achieve the preparation of heterogeneous parts corresponding to the composite material. For example, according to the actual product requirements, the ratio requirements between the matrix material and at least one reinforcing material can be determined, the conveying speed of each material in at least two storage barrels can be determined, and the materials corresponding to the matrix material and at least one reinforcing material can be conveyed to the accommodating space according to a predetermined ratio. Then, under the solid mixing and stirring (for example, in the solid mixing section and the feeding section) and melt mixing (for example, in the compression section and the metering section) extrusion action of the extrusion screw, efficient mixing between different material components can be achieved, and finally, heterogeneous parts with gradually varying performance can be prepared, and the optimal configuration of material-structure-performance can be achieved, thereby meeting specific material performance requirements.

[0105] In summary, the embodiments of the present disclosure provide a 3D printhead structure that can be used to prepare variable-component composite materials. This effectively addresses the problems of poor forming and mixing effects and slow switching between multiple material components in single-screw extrusion 3D printing, enabling rapid online adjustment of the ratio of multiple components and / or adjustment of the different components of the composite material. Furthermore, key parameters of the 3D printhead structure can be optimized based on simulated mixing effects, making it suitable for real-time online mixing of multiple material components. This 3D printhead structure can be used to 3D print heterogeneous parts with various desired properties.

[0106] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems or devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and relevant parts can be referred to the method description. The values ​​of the parameter ranges provided in the embodiments of this disclosure can all be taken to the endpoint values.

[0107] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present disclosure.

Claims

1. A 3D printing head structure that can be used to prepare a variable component composite material, characterized in that: include: A single-screw extrusion structure comprises an extrusion screw and an extrusion barrel, wherein the extrusion barrel is located outside the extrusion screw and has an accommodating space between the extrusion screw and the extrusion barrel; The extrusion screw is divided from top to bottom into a solid mixing section, a feeding section, a compression section, and a metering section; the outer periphery of the main body of the solid mixing section is spaced apart by: a tapered screw flight, a first blade, and a second blade; the radial dimension of the tapered screw flight gradually decreases along the axial transmission direction; the blade rotation diameter of the first blade is greater than the maximum radial dimension of the tapered screw flight; the blade rotation diameter of the second blade is less than the minimum radial dimension of the tapered screw flight; At least two material storage barrels with adjustable material delivery information are distributed on the top of the extruder barrel, and the material output ports of the storage barrels are used to output the material in powder or granular form to the accommodating space; A nozzle is arranged at the bottom of the extruder barrel; The cooling device and the heating device are arranged at intervals on the periphery of the extruder barrel, and the cooling device is located above the heating device.

2. The 3D printing head structure according to claim 1, characterized in that: The radial dimension of the conical screw fin can vary within a range of 10 mm to 100 mm; There are multiple first blades, the multiple first blades are distributed from top to bottom along the axial direction, and the blade rotation diameters of the multiple first blades gradually decrease along the axial direction; There are multiple second blades, which are arranged from top to bottom along the axial direction and distributed in the gaps of the conical screw fins.

3. The 3D printing head structure according to claim 1, characterized in that: The blade rotation diameter of the first blade is 20 mm to 40 mm; The blade rotation diameter of the second blade is 6 mm to 18 mm; The radial dimension of the conical screw fin is 10 mm to 30 mm.

4. The 3D printing head structure according to claim 1, characterized in that: Pins for homogenizing melt mixing are distributed on the periphery of the main body of the metering section, and the height of the pins does not exceed the screw groove depth or screw thread height of the metering section; The cross-sectional shape of the pin includes one or more of the following combinations: oval, circular, semicircular, sawtooth, and polygonal including triangle.

5. The 3D printing head structure according to claim 4, characterized in that: The cross-sectional diameter or cross-sectional side length of the pin is 0.3 mm to 1 mm; The spacing between the pins is 3mm to 10mm; The height of the pin is 1mm to 2mm; The number of the pins distributed along the circumference of the extrusion screw is 6 to 20.

6. The 3D printing head structure according to claim 1, characterized in that: The length ratio of the solid mixing section, the feeding section, the compression section and the metering section is 4:4:3:

3.

7. The 3D printing head structure according to claim 1, characterized in that: The screw groove depth of the feeding section is 2 mm to 4 mm, and the screw groove depth of the metering section is 1 mm to 2 mm.

8. The 3D printing head structure according to any one of claims 1 to 7, characterized in that: The diameter of the extrusion screw is 8 mm to 20 mm, the aspect ratio is 8:1 to 10:1, and the compression ratio is 2 to 4; The portion of the extruder barrel that matches the solid mixing section is funnel-shaped, and the portion of the extruder barrel that matches the feeding section, the compression section, and the metering section is straight-cylinder-shaped; The inner diameter of the straight cylindrical portion of the extruder barrel is 8.2 mm to 20.2 mm, and the outer diameter is 15 mm to 30 mm.

9. The 3D printing head structure according to claim 1, characterized in that: The extrusion screw and the extrusion barrel are both prepared by 3D printing technology; The extrusion screw and the extruder barrel are made of stainless steel or die steel.

10. The 3D printing head structure according to claim 1, characterized in that: The extrusion screw is used to rotate under the driving action of the driving member; The cooling device is a power-adjustable air-cooling device or a water-cooling device, and the air-cooling device or the water-cooling device is used to determine a target heat dissipation rate according to the temperature of the heating device. The target heat dissipation rate is used to prevent agglomeration of solid materials in the solid mixing section and the feeding section due to heating by the lower heating device and to protect the driving component from damage by high temperature.

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