3D printing composite consumable for enhancing Z-axis strength through magnetic field assisted orientation and preparation and printing method

Abstract

The invention discloses a 3D printing composite consumable capable of enhancing Z-axis strength through magnetic field assisted orientation and a preparation and printing method, and belongs to the technical field of additive manufacturing, and the composite consumable comprises, by mass, 70-95 parts of a thermoplastic resin matrix; 5-30 parts of a magnetic response enhancing filler; 0.5 to 2.0 parts of a dispersant; 0.1 to 0.5 part of an antioxidant; the magnetic response reinforcing filler is a fiber core material of which the surface is coated with a magnetic nanoparticle layer; in a molten state, the internal magnetic response enhancing filler can directionally deflect under the action of an external magnetic field. When magnetic field assisted 3D printing is carried out, an external magnetic field in a specific direction is applied to a fused deposition modeling spray head; when the consumable material is melted and extruded, the magnetic response reinforcing filler overcomes melt shear resistance under the action of magnetic field torque, generates directional deflection and is changed from the extrusion direction to the arrangement in the interlayer stacking direction or at a preset angle, and an interlayer reinforcing structure is formed. The problem that the Z-axis mechanical property of a traditional fiber-reinforced 3D printing consumable is weak due to fiber down-flow orientation is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, specifically relating to a 3D printing composite consumable for enhancing Z-axis strength with magnetic field-assisted orientation, and its preparation and printing methods. Background Technology

[0002] Fused deposition modeling (FDM) technology, with its advantages of low equipment cost, simple operation, and high degree of molding freedom, has become one of the most widely used technologies in the additive manufacturing field, especially showing great potential in the field of composite material molding. Fiber-reinforced composite materials, due to their combination of lightweight and high strength, are widely in demand in high-end equipment fields such as aerospace and automotive manufacturing. Combining them with FDM technology can achieve low-cost and rapid fabrication of complex structural parts. However, FDM printing of fiber-reinforced composite materials faces an inherent physical contradiction: shear-induced orientation. When the melt containing fibers flows through the tiny printing nozzle, it is subjected to strong shear forces, which force the fibers to be highly oriented along the extrusion direction (horizontal X / Y axis). Although this orientation characteristic significantly improves the horizontal tensile strength of the printed part, it does not effectively contribute to the interlaminar bonding force in the vertical direction (Z-axis). Furthermore, fiber enrichment on the interlaminar surface hinders the interlaminar diffusion of polymer chains, leading to a significant decrease in Z-axis strength and making it prone to interlaminar cracking, which severely limits its application in load-bearing structural parts.

[0003] To address the interlaminar strength defects in FDM-printed fiber-reinforced composites, researchers have conducted related improvement studies. The core approach focuses on mitigating the negative impact of shear-induced orientation by optimizing the printing process or adjusting the equipment structure. The most widely applied methods include modifying the nozzle geometry, increasing the cross-sectional area of ​​the internal flow channel, designing streamlined nozzle chambers, and adopting variable-diameter nozzle outlets. Optimizing the nozzle structure can reduce the shear rate of the melt flowing through the nozzle to some extent, decreasing the degree of forced horizontal fiber orientation, and promoting uniform fiber dispersion in the melt, thereby improving the interlaminar bonding state of the printed part and enhancing the mechanical properties in the Z-axis direction. In addition, some researchers have attempted to improve interlaminar fusion by adjusting process parameters such as printing temperature, interlaminar gap, and extrusion speed; however, these process adjustments have limited effect on improving fiber orientation and are mostly used as auxiliary means for nozzle structure improvement.

[0004] While existing techniques for modifying nozzle geometry can alleviate shear-induced orientation problems to some extent, they still suffer from numerous insurmountable drawbacks, limiting the effectiveness of improvements and hindering practicality. There is an inherent contradiction between optimizing nozzle geometry and printing accuracy. Enlarging the flow channel or using variable diameter structures to reduce shear force leads to decreased molding accuracy after melt extrusion, increased surface roughness, and larger dimensional errors in the printed parts, failing to meet the requirements for high-precision structural component fabrication. The improvement in fiber orientation is limited; existing nozzle structures can only moderately reduce shear strength and cannot fundamentally solve the problem of shear-induced fiber horizontal orientation. The increase in Z-axis strength of the printed parts is small and still insufficient to meet the mechanical requirements of stressed structural components. Improved nozzles lack versatility; specialized nozzle structures need to be designed for composite materials with different fiber types, diameters, and contents, increasing equipment costs and application difficulty, hindering large-scale deployment. Therefore, existing methods cannot simultaneously achieve printing accuracy and interlayer mechanical properties, making it difficult to effectively solve the interlayer cracking problem in FDM-printed fiber-reinforced composite materials. There is an urgent need to develop a new magnetic field-assisted orientation enhancement method for 3D printing composite materials with improved Z-axis strength. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength, as well as a preparation and printing method, so as to solve the technical problem of poor Z-axis mechanical properties caused by the co-current orientation of fibers in traditional fiber-reinforced 3D printing consumables.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength, comprising, by weight: 70-95 parts thermoplastic resin matrix; 5-30 parts magnetic response enhancing filler; 0.5-2.0 parts dispersant; and 0.1-0.5 parts antioxidant. The magnetic response-enhancing filler is a fiber core material with a magnetic nanoparticle layer on its surface; the magnetic response-enhancing filler inside the 3D printing composite consumable with magnetic field-assisted orientation enhancement can be oriented and deflected under the action of an external magnetic field in the molten state.

[0007] Preferably, the fiber core material is a fibrous or whisker-like material; the aspect ratio of the fibrous or whisker-like material is greater than 10.

[0008] Preferably, the thermoplastic resin matrix is ​​selected from one or more of polylactic acid, polycaprolactone, thermoplastic polyurethane, polyetheretherketone, and polycarbonate; the dispersant is selected from one or more of zinc stearate, ethylene bis-stearamide, polyethylene glycol, and titanate coupling agent; and the antioxidant is selected from one or more of hindered phenolic antioxidant 1010, phosphite antioxidant 168, antioxidant 1076, and antioxidant 264.

[0009] Preferably, the magnetic nanoparticle layer is composed of iron oxide nanoparticles, nickel nanoparticles, or cobalt nanoparticles.

[0010] Preferably, the fiber core material is carbon fiber, glass fiber, potassium titanate whiskers, or carbon nanotubes; the coating method includes chemical coprecipitation, sol-gel method, or electrostatic adsorption method; the thickness of the magnetic nanoparticle layer is 50-200 nm.

[0011] The preparation method of the above-mentioned magnetic field-assisted orientation-enhanced Z-axis strength 3D printing composite consumable disclosed in this invention includes: pretreating the fiber core material, dispersing it in a magnetic nanoparticle solution, and obtaining a magnetic response-enhancing filler after a chemical co-precipitation reaction; mixing the thermoplastic resin matrix, the magnetic response-enhancing filler, the dispersant and the antioxidant evenly, and extruding the filament at 180-200℃ to obtain the magnetic field-assisted orientation-enhanced Z-axis strength 3D printing composite consumable.

[0012] The method for magnetic field-assisted 3D printing of the above-mentioned magnetic field-assisted orientation-enhanced Z-axis strength 3D printing composite consumable disclosed in this invention includes: A 3D printing composite filament with magnetic field-assisted orientation to enhance Z-axis strength is fed into the heated nozzle of a 3D printer for melting. A magnetic field is applied to the area where the melt leaves the nozzle but has not yet completely cooled and solidified. The magnetic response-enhancing filler in the melt rotates under the action of the magnetic field torque, aligns along the direction of the magnetic field lines, and cools and solidifies with the resin in this orientation state, forming an enhanced structure that spans the interface of the deposition layer.

[0013] Preferably, the melting temperature is 20-40°C above the melting point of the matrix resin; the applied magnetic field is a constant magnetic field or an alternating magnetic field.

[0014] Preferably, the strength of the magnetic field is 0.1-0.8T, and the direction of the magnetic field lines is perpendicular to the plane of the printing platform or forms an angle of 45°-90° with the printing path.

[0015] Preferably, the magnetic field is generated by a ring-shaped permanent magnet or an electromagnetic coil installed at the end of the 3D printer nozzle, and the magnetic field generating device moves synchronously with the printing nozzle; the magnetic field strength is controlled by adjusting the current of the electromagnetic coil, thereby regulating the deflection angle of the magnetic response enhancement filler in the matrix, and realizing the gradient distribution of anisotropic mechanical properties inside the printed part.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a 3D printing composite filament with magnetic field-assisted orientation enhancement for Z-axis strength. It introduces a fiber core material with a surface coated with magnetic nanoparticles as a magnetically responsive reinforcing filler, utilizing its ability to undergo directional deflection under an applied magnetic field in the molten state, effectively overcoming the limitations of shear-induced orientation in traditional FDM technology. By applying a vertical magnetic field during printing, glass fibers that might otherwise be arranged horizontally are actively induced to align vertically, forming a reinforcing structure across the interlayer interface. This achieves active control over the orientation of the reinforcing filler. This active control significantly improves the Z-axis mechanical properties of the printed part, effectively solving the problem of weak Z-axis mechanical properties caused by the co-current orientation of fibers in traditional fiber-reinforced 3D printing filaments.

[0017] Furthermore, the core material of the magnetically responsive reinforced filler is a fibrous or whisker-like material with an aspect ratio greater than 10, optimizing the performance of the 3D printing composite filament for magnetically assisted orientation enhancement of Z-axis strength. When the composite filament is heated to a molten state during 3D printing, the internal magnetically responsive reinforced filler, i.e., the fibrous or whisker-like core material with a magnetic nanoparticle layer on its surface, experiences a magnetic torque under the influence of an external magnetic field. Due to the significantly elongated shape and aspect ratio greater than 10 of these fibrous or whisker-like core materials, their response to magnetic torque is more sensitive and efficient. The high aspect ratio results in relatively low fluid resistance when the filler rotates in the melt, making it easier to overcome the viscous resistance of the matrix resin. This allows for faster and more precise directional deflection along the magnetic field lines, enabling more reinforcing filler to cross adjacent printing layer interfaces, forming a continuous, Z-axis-oriented reinforcing structure. Compared to fillers with a small aspect ratio or non-fibrous fillers, fibrous or whisker fillers with a high aspect ratio can provide a longer effective load transfer path and a stronger mechanical interlocking effect after orientation, thereby significantly improving the tensile strength, flexural strength and interlayer bonding strength of the printed parts in the Z-axis direction.

[0018] Furthermore, the thermoplastic resin matrix is ​​one or more of polylactic acid, polycaprolactone, thermoplastic polyurethane, polyetheretherketone, and polycarbonate, allowing for precise control of the physicochemical properties of the composite consumables according to different application requirements. When biocompatibility or biodegradability is required, polylactic acid or polycaprolactone can be selected as the matrix to ensure the consumables' application potential in the biomedical field; when high strength, high heat resistance, or chemical corrosion resistance is required, polyetheretherketone or polycarbonate can be selected to meet stringent engineering application requirements; while thermoplastic polyurethane can impart excellent flexibility and abrasion resistance to the consumables. The excellent composite of these specific resin matrices with magnetically responsive fillers ensures that, in the molten state, the magnetically responsive fillers can be effectively oriented under the action of an external magnetic field and form a stable reinforced structure after cooling and solidification. The optimized matrix selection enables the composite consumables not only to possess the ability of magnetic field-assisted orientation but also to provide customized mechanical, thermal, or biological properties according to the specific functional requirements of the final printed parts, thereby significantly improving the performance diversity and application breadth of the composite consumables.

[0019] Furthermore, the magnetic nanoparticle layer, composed of iron oxide nanoparticles, nickel nanoparticles, or cobalt nanoparticles, ensures that the magnetically responsive filler, in its molten state, can generate a sufficiently strong magnetic torque under the influence of an external magnetic field, thereby achieving efficient directional deflection. These magnetic nanoparticles all possess significant magnetic properties, enabling them to be effectively magnetized under an external magnetic field and generate a magnetic torque aligned with the direction of the magnetic field. When these nanoparticles are uniformly coated on the surface of the fiber core material, the entire fiber core material acquires reliable magnetic responsiveness. During the 3D printing process, when the composite material is in a molten state, the viscosity of the matrix resin decreases, allowing the fiber core material coated with these specific magnetic nanoparticles to rotate relatively freely within the melt. At this point, when an external magnetic field is applied, these strongly magnetically responsive fiber core materials will rapidly align along the magnetic field lines. The magnetic nanoparticles ensure that the magnetically responsive filler has sufficient magnetization intensity and response speed in the molten state, thereby overcoming the resistance caused by melt viscosity, achieving effective orientation, and ultimately forming the desired structure with enhanced Z-axis strength after cooling and solidification.

[0020] Furthermore, the fiber core material is made of carbon fiber, glass fiber, potassium titanate whiskers, or carbon nanotubes. These high-performance fiber materials, acting as a reinforcing skeleton, achieve directional alignment under the influence of a magnetic field, effectively forming a continuous reinforcing structure across the deposition layer interface. This overcomes the problems of weak interlayer bonding and insufficient Z-axis strength in traditional 3D printing technology. By selecting specific fiber core materials with high strength and high modulus, excellent reinforcement effects are ensured even with low filler content. This allows the printed parts to maintain good formability while significantly improving their overall strength, stiffness, and toughness, especially the mechanical properties in the Z-axis direction, thereby broadening the application scope of 3D printing technology in the manufacturing of high-performance structural components.

[0021] Furthermore, coating methods such as chemical co-precipitation, sol-gel, or electrostatic adsorption are employed to ensure that the magnetic nanoparticles adhere firmly and uniformly to the surface of the fiber core material, forming a magnetically responsive enhanced filler with stable magnetic response capabilities. Simultaneously, by precisely controlling the thickness of the magnetic nanoparticle layer within the range of 50-200 nm, each magnetically responsive enhanced filler ensures sufficient magnetic torque response capability while avoiding problems such as excessive filler weight, poor dispersibility, or decreased mechanical properties caused by excessively thick coating layers. When the composite filament is in a molten state during 3D printing, the internal magnetically responsive enhanced filler, under the influence of an external magnetic field, can efficiently and stably undergo directional deflection thanks to the magnetic nanoparticle layer. This allows the magnetically responsive enhanced filler to overcome melt viscosity resistance and achieve effective magnetic field-assisted orientation, thereby forming the desired reinforcing structure in the printed part and significantly improving the Z-axis mechanical properties of the printed part.

[0022] This invention discloses a method for magnetic field-assisted 3D printing using the aforementioned magnetic field-assisted orientation-enhanced Z-axis strength 3D printing composite filament. The initial step of the 3D printing process is to melt the magnetic field-assisted orientation-enhanced Z-axis strength 3D printing composite filament into the heated nozzle of a 3D printer. This aims to heat the solid composite filament above its melting temperature, transforming it into a fluid melt. Applying a magnetic field to the region where the melt leaves the nozzle but has not yet completely cooled and solidified is crucial for achieving magnetic field-assisted orientation. This region is a transitional area where the melt still maintains a certain degree of fluidity but is about to solidify. Precisely applying a magnetic field to this region ensures that the magnetic torque effectively acts on the magnetically responsive enhanced filler in the melt, allowing it to rotate freely and align along the magnetic field lines. This avoids premature solidification of the melt, which would prevent the filler from aligning, or applying the magnetic field too late, which would result in poor orientation. The rotation of the magnetically responsive enhanced filler in the melt under the action of the magnetic torque, aligning it along the magnetic field lines, is the core mechanism of this method. Because the surface of the magnetically responsive reinforced filler is coated with a layer of magnetic nanoparticles, when placed in an external magnetic field, it experiences a magnetic torque, causing its own magnetic moment direction to align with the direction of the external magnetic field. This leads to the filler rotating within the melt until its long axis is parallel to the magnetic field lines, reaching an energy-stable state. Finally, in this oriented state, it solidifies as the resin cools, forming a reinforcing structure that spans the deposition layer interface. When the magnetically responsive reinforced filler achieves precise orientation under the influence of a magnetic field, the surrounding resin matrix rapidly cools and solidifies, locking the filler in its oriented state. This solidification process allows the filler to effectively cross the layer interfaces formed by layer-by-layer deposition during 3D printing, forming a continuous and oriented reinforcing structure, thus significantly improving the mechanical properties of the printed part in the Z-axis direction. This effectively solves the problem of having only magnetically responsive composite consumables but being unable to achieve precise filler orientation during 3D printing. By actively orienting the magnetically responsive reinforced filler in the molten state and fixing it in an oriented state, a continuous reinforcing structure spanning the deposition layer interface is formed inside the printed part. It significantly improves the mechanical properties of 3D printed parts in the Z-axis direction, overcomes the inherent defect of low interlayer bonding strength in traditional FDM printed parts, and makes the overall performance of printed parts more balanced and reliable, thus broadening its application potential in structural and functional parts.

[0023] Furthermore, when the melting temperature is 20-40°C above the melting point of the matrix resin, the thermoplastic resin matrix can achieve suitable viscosity and flowability. The resin will not become too viscous due to excessively low temperatures, hindering the rotation of the magnetically responsive reinforced filler, nor will it become excessively diluted due to excessively high temperatures, leading to filler sedimentation or thermal degradation. This suitable melting state provides favorable conditions for the free rotation of the magnetically responsive reinforced filler within the melt. When a magnetic field is applied to the area of ​​the melt leaving the nozzle but not yet fully cooled and solidified, both constant and alternating magnetic fields can apply a magnetic torque to the magnetically responsive reinforced filler in its suitable flow state. A constant magnetic field provides a continuous directional force, allowing the filler to align stably along the magnetic field lines, suitable for scenarios requiring stable, unidirectional orientation. An alternating magnetic field, through its periodic changes, can more effectively overcome the viscous resistance within the melt, promoting filler rotation and potentially achieving faster or more uniform orientation in certain situations, especially when the initial filler distribution is uneven or the melt viscosity is relatively high. The combination of a suitable melting temperature and a specific type of magnetic field ensures that the magnetically responsive filler can be oriented efficiently and precisely in the melt along a preset direction and maintain this orientation during the subsequent cooling and shaping process, thereby forming the desired reinforcing structure inside the printed part and significantly improving the mechanical properties in the Z-axis direction.

[0024] Furthermore, in the magnetic field-assisted 3D printing method, after the magnetically assisted orientation-enhanced Z-axis strength 3D printing composite filament is fed into the heated nozzle of the 3D printer for melting, a magnetic field strength of 0.1-0.8T is applied to the area where the melt leaves the nozzle but has not yet fully cooled and solidified. This ensures that the magnetically responsive reinforcing filler can obtain sufficient magnetic torque in the melt to overcome the viscous resistance of the melt and achieve effective rotation. When the magnetic field lines are perpendicular to the printing platform plane, the magnetically responsive reinforcing filler is guided to align along the Z-axis, thereby forming a continuous reinforcing structure between the layers of the printed part, effectively compensating for the deficiency of interlayer bonding in traditional 3D printing technology. When the magnetic field lines form an angle of 45°-90° with the printing path, the filler can be oriented at a specific angle according to specific needs, thereby achieving anisotropic control of the internal mechanical properties of the printed part. This allows the magnetically responsive filler to be oriented in a desired and efficient manner and locked in this orientation state during the subsequent cooling and shaping process, ultimately forming a 3D printed part with excellent Z-axis strength or specific anisotropic mechanical properties. This solves the problem of poor filler orientation and unsatisfactory mechanical properties caused by insufficient control of magnetic field parameters.

[0025] Furthermore, by integrating the magnetic field generator into the end of the 3D printer's nozzle and making it move synchronously with the nozzle, the magnetic field can be precisely and in real-time applied to the depositing molten composite material. When an electromagnetic coil is used as the magnetic field generator, its core working principle is to apply a magnetic torque to the magnetically responsive filler in the melt using a magnetic field generated by an electric current, causing the filler to deflect along the direction of the magnetic field lines. By precisely adjusting the current in the electromagnetic coil, the strength of the magnetic field can be directly controlled. Changes in the magnetic field strength affect the magnitude of the magnetic torque, which in turn determines the deflection angle of the magnetically responsive filler in the molten matrix. In areas requiring higher strength or stiffness, the current can be increased to enhance the magnetic field, causing the filler to align more tightly along a specific direction; while in areas requiring more flexibility or isotropic properties, the current can be decreased to reduce the magnetic field strength, allowing for a larger deflection angle or a more random distribution of the filler. This dynamic, localized magnetic field strength control capability enables the magnetically responsive filler inside the printed part to achieve a fine, spatially variable orientation distribution. Ultimately, this controllable filler orientation gradient is directly converted into the gradient distribution of anisotropic mechanical properties inside the printed part, thereby enabling complex functional structures and performance optimizations to be achieved in a single printed part according to specific application requirements, significantly improving the design freedom and functional diversity of 3D printing materials. Attached Figure Description

[0026] Figure 1 This is a flowchart of the method for magnetic field-assisted 3D printing using a 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength, as disclosed in this invention. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0029] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0030] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0031] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0032] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0033] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0034] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0035] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0036] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0037] This invention discloses a 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength, comprising the following raw materials in parts by weight: thermoplastic resin matrix: 70-95 parts; magnetic response-enhancing filler: 5-30 parts; dispersant: 0.5-2.0 parts; antioxidant: 0.1-0.5 parts; The magnetically responsive filler is a fibrous or whisker-like material with an aspect ratio greater than 10, and its surface is coated with a layer of magnetic nanoparticles. When the consumable is in the molten state, the magnetically responsive filler inside can undergo directional deflection under the influence of an external magnetic field. The thickness of the magnetic nanoparticle layer is 50-200 nm, preferably 80-150 nm. Too thin a layer (<50 nm) will result in insufficient magnetic response torque, making it difficult to overcome melt shear forces; too thick a layer (>200 nm) will easily lead to coating peeling, affecting interfacial bonding.

[0038] The thermoplastic resin matrix is ​​selected from one or more of polylactic acid (PLA), polycaprolactone (PCL), thermoplastic polyurethane (TPU), polyetheretherketone (PEEK), or polycarbonate (PC). The dispersant is selected from one or more of zinc stearate, ethylene bis-stearamide (EBS), polyethylene glycol (PEG), and titanate coupling agents. The antioxidant is selected from one or more of hindered phenolic antioxidant 1010, phosphite antioxidant 168, antioxidant 1076, and antioxidant 264.

[0039] The preparation method of magnetic response enhancement filler is as follows: carbon fiber, glass fiber, potassium titanate whiskers or carbon nanotubes are used as core materials, and iron(III) oxide (Fe3O4), nickel (Ni) or cobalt (Co) nanoparticles are coated on the surface of the core material by chemical coprecipitation, sol-gel method or electrostatic adsorption method; the thickness of the coating layer is 50-200 nm.

[0040] This invention discloses a magnetic field-assisted 3D printing method for 3D printing composite consumables that enhance Z-axis strength using magnetic field-assisted orientation, comprising the following steps: S1. Feed the composite material into the heating nozzle of the 3D printer for melting, and set the melting temperature to 20-40℃ above the melting point of the matrix resin; S2. Apply a constant magnetic field or alternating magnetic field with an intensity of 0.1T-0.8T to the area where the melt leaves the nozzle but has not yet completely cooled and solidified; S3. The direction of the magnetic field lines is set to be perpendicular to the printing platform plane (i.e., the Z-axis direction) or at an angle of 45°-90° with the printing path; S4. The magnetic response-enhancing filler in the melt rotates under the action of magnetic field torque, aligns along the direction of magnetic field lines, and cools and solidifies with the resin in this orientation state, forming an enhanced structure that crosses the interface of the deposition layer.

[0041] The magnetic field is generated by a ring-shaped permanent magnet or electromagnetic coil installed at the end of the print head, and the magnetic field generating device moves synchronously with the print head.

[0042] By adjusting the current in the electromagnetic coil to control the magnetic field strength, the deflection angle of the magnetic response-enhancing filler in the matrix can be controlled, thereby achieving a gradient distribution of anisotropic mechanical properties inside the printed part.

[0043] This invention provides a composite consumable and its application method that breaks through the traditional flow field orientation limitation by using external field assistance to achieve Z-axis directional arrangement of packing to enhance interlayer bonding.

[0044] The present invention aims to provide a 3D printing consumable and method capable of actively controlling fiber orientation.

[0045] The technical principle of this invention is: 1. Magnetic functionalization: endowing traditional reinforcing fibers (such as chopped carbon fiber) with magnetic responsive properties. By coating the fiber surface with nano-magnetic particles, it becomes a miniature "magnetic needle".

[0046] 2. The interplay between flow field and magnetic field: During the printing process, the fiber is subjected to two forces: one is the fluid shear force (which causes it to lie horizontally), and the other is the torque of the external magnetic field (which causes it to stand upright along the magnetic field lines).

[0047] 3. In-situ Implantation: This invention applies a sufficiently strong vertical magnetic field at the nozzle exit, causing the semi-molten magnetic fibers to be forced upright the instant the melt leaves the nozzle. These fibers then penetrate the surface of the cooled material above or bridge the next layer. After cooling and solidification, these upright fibers act like countless tiny "steel nails" or "piles," firmly anchoring the layers together, thus completely solving the problem of weak Z-axis strength.

[0048] This invention overcomes the limitations of traditional magnetic field-assisted 3D printing in terms of mechanical property control. By integrating the magnetic field generator with the printing nozzle and moving them synchronously, and utilizing the current adjustment capability of the electromagnetic coil, precise and dynamic control of the magnetic field strength and the deflection angle of the magnetically responsive filler is achieved. This allows for local optimization of the microstructure within the printed part according to design requirements, thereby achieving a gradient distribution of anisotropic mechanical properties within a single printed part. Different stiffness, strength, or toughness can be imparted to different regions of the printed part to meet performance requirements under complex working conditions, greatly enhancing the functionality and application range of 3D printing materials and providing a new approach for manufacturing high-performance, multifunctional composite materials.

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0050] Example 1 General-purpose PLA-based magnetic carbon fiber consumables Material system: Polylactic acid (PLA) + magnetic chopped carbon fiber (MCF) Preparation process: 1) Magnetic Modification: Short-cut carbon fibers with an average length of 100 μm were acidified with concentrated nitric acid to remove surface colloids. These fibers were then dispersed in a mixed solution of FeCl3 and FeCl2 (molar ratio 2:1), and the pH was adjusted to 10 by adding ammonia dropwise at 80 °C to induce a chemical co-precipitation reaction. After the reaction, the carbon fiber surface was uniformly coated with a layer of Fe3O4 nanoparticles. After washing, drying, and grinding, MCF was obtained.

[0051] 2) Blending and granulation: Mix 85 parts PLA granules, 15 parts MCF, and 0.5 parts silane coupling agent (KH550) evenly and add the mixture to a twin-screw extruder. Set the extrusion temperature to 190℃. Because MCF is magnetic, reduce the number of kneading blocks in the screw assembly to avoid excessive shearing that could cause the magnetic layer to peel off.

[0052] 3) Wire extrusion: 1.75mm wire is extruded through a single screw wire drawing machine.

[0053] Printing process: A high-temperature resistant neodymium iron boron (NdFeB) ring-shaped permanent magnet is fitted around the brass nozzle of the FDM printer. The central magnetic field strength at the nozzle exit is approximately 0.4T, with the magnetic field lines pointing vertically downwards. The printing temperature is 210℃, and the layer height is 0.2mm.

[0054] Expected results: After melt extrusion, the carbon fibers rapidly flip under the influence of a magnetic field. The microstructure shows that about 70% of the fibers are at an 85° angle to the printed layer plane, effectively penetrating the interlayer interface.

[0055] Example 2 Engineering-grade PEEK-based magnetic whisker consumables Material system: Polyetheretherketone (PEEK) + magnetic potassium titanate whiskers Preparation process: 1) Magnetic modification: Electroless nickel plating is used. Potassium titanate whiskers are sensitized and activated, and then placed in a plating solution containing nickel sulfate and sodium hypophosphite. A layer of metallic nickel is deposited on the surface of the whiskers, giving them excellent ferromagnetism.

[0056] 2) Melt blending: 90 parts of PEEK powder and 10 parts of nickel-plated whiskers were mixed at 360°C using a twin-screw extruder. The high viscosity of PEEK requires the whiskers to have higher magnetic responsiveness, and the nickel plating layer provides a stronger magnetic moment than Fe3O4.

[0057] 3) Forming: Prepared into 1.75mm wire.

[0058] Printing process: Because PEEK printing temperatures can reach as high as 400℃, permanent magnets are prone to demagnetization. In this embodiment, a water-cooled electromagnetic coil surrounds the nozzle, and a DC current is applied to generate an adjustable magnetic field of 0.6T.

[0059] Expected results: The whiskers form a dense, brush-like, vertically arranged structure between the layers, which not only significantly improves the interlayer shear strength but also endows PEEK components with a certain electromagnetic shielding effectiveness.

[0060] Example 3 Flexible TPU-based anisotropic conductive consumables Material system: Thermoplastic polyurethane (TPU) + magnetic nickel-plated graphene Preparation process: 1) Magnetic modification: Nickel nanoparticles are grown in situ on graphene oxide (GO) sheets using a solvothermal method, followed by thermal reduction to obtain magnetic graphene.

[0061] 2) Composite: 92 parts TPU and 8 parts magnetic graphene are mixed in a mixer, then crushed, granulated and extruded into wire.

[0062] Printing process: Apply a vertical magnetic field during printing.

[0063] Expected results: Graphene sheets are vertically arranged along the Z-axis in a TPU matrix, overlapping to form vertical conductive pathways. The fabricated flexible sensor exhibits high conductivity (resistivity <10Ω·cm) in the Z-axis direction, while being insulated in the X / Y-axis directions, achieving anisotropic conductivity without the need for complex circuit design.

[0064] Example 4 Printing method for gradient structure functional consumables Material system: The same PLA / MCF consumables as in Example 1.

[0065] Technological Innovation: This embodiment focuses on achieving the gradient structure by controlling the electromagnet current.

[0066] Printing process: When printing the outer shell of the model (which requires a high surface finish), turn off the electromagnet current. At this point, the fibers are mainly distributed horizontally, resulting in a smooth surface.

[0067] When infilling the interior of the printed model or at stress-bearing joints, apply the maximum current (0.5T). At this point, the fibers are vertically aligned, providing support strength similar to that of a "column".

[0068] Expected results: The final product combines excellent appearance quality (no burrs on the outer shell) with superior internal structural strength, achieving digital programming of the material's microstructure.

[0069] Example 5 Low-cost magnetic glass fiber reinforced consumables Material system: polyethylene terephthalate-1,4-cyclohexanediethanol ester (PETG) + magnetic glass fiber.

[0070] Preparation process: Magnetic modification: An electrostatic self-assembly method was used. Negatively charged glass fibers were immersed in positively charged Fe3O4 nanofluid, forming a dense monolayer coating through electrostatic adsorption. Subsequently, the coating was shaped and hydrophobically treated using a silane coupling agent, KH560.

[0071] Blending: 80 parts PETG and 20 parts magnetic glass fiber are blended and extruded.

[0072] Printing process: A standard FDM printer was modified by adding a simple ring magnet.

[0073] Expected results: This is a low-cost solution. Fiberglass is inexpensive and white with a semi-transparent coating. After coating, it appears black. After magnetic field-induced orientation, the interlayer bonding strength is increased by more than 40%, and the anisotropy of the material's thermal shrinkage is reduced, making it less prone to edge warping in large-size printing.

[0074] Example 6 Polycaprolactone (PCL) matrix and carbon nanotube filler were used. Raw material composition (parts by weight): thermoplastic resin matrix (PCL): 94.4 parts; magnetic response enhancing filler (magnetic carbon nanotubes, coated with Fe3O4, layer thickness 50nm): 5.0 parts; dispersant (PEG): 0.5 parts; antioxidant 1010: 0.1 parts.

[0075] Preparation process: PCL has a low melting point, and the extrusion temperature is set to 100℃.

[0076] Printing process: Apply a weak magnetic field of 0.1T (because the viscosity of PCL melt is extremely low, a small magnetic field is sufficient to drive it), and the magnetic field lines are perpendicular.

[0077] Example 7 Using a PEEK matrix and potassium titanate whiskers.

[0078] Raw material composition (parts by weight): thermoplastic resin matrix (PEEK): 68.5 parts; magnetic response enhancing filler (magnetic potassium titanate whiskers, coated with nickel, 200nm thick): 30.0 parts; dispersant (titanium ester coupling agent): 1.0 part; antioxidant (168): 0.5 parts.

[0079] Preparation process: Extrusion temperature 370℃.

[0080] Printing process: Apply a strong magnetic field of 0.8T (due to high filler content and high viscosity), with the magnetic field lines perpendicular.

[0081] Example 8 Raw material composition: Same as in Example 1.

[0082] Printing process: Adjust the direction of the electromagnetic coil current so that the magnetic field lines form a 45° angle with the printing path. This angle is intended to balance the Z-axis strength with the X / Y-axis strength within the layer.

[0083] Example 9 Material system (parts by weight): Polycarbonate (PC): 95 parts; Magnetic response enhancing filler (cobalt nanoparticles coated with carbon fiber): 4.2 parts; Dispersant (zinc stearate): 0.5 parts; Antioxidant 1076: 0.3 parts.

[0084] Preparation process: 1) Magnetic modification: The carbon fiber is dispersed in cobalt salt sol using the sol-gel method. After hydrolysis and condensation reaction, a Co nanoparticle coating layer with a thickness of 125 nm is formed on the fiber surface. 2) Blending extrusion: PC, magnetic carbon fiber, zinc stearate and antioxidant 1076 are mixed evenly, granulated at 200℃ through a twin-screw extruder, and extruded into 1.75mm wire by a single-screw wire drawing machine; Printing process: An alternating magnetic field with a strength of 0.4T is generated using an electromagnetic coil, and the magnetic field lines are perpendicular to the printing platform; the melting point of PC is approximately 220℃, and the printing temperature is 240℃ (the melting point of the substrate +20℃). Example 10 Material system (parts by weight): PLA: 80 parts; magnetic response enhancement filler (glass fiber coated Fe3O4): 19.2 parts; dispersant (ethylene bis-stearamide): 0.5 parts; antioxidant 264: 0.3 parts.

[0085] Preparation process: 1) Magnetic modification: Fe3O4 nanoparticles with a thickness of 125nm were coated on the surface of glass fiber using electrostatic adsorption. 2) Blending extrusion: Mix all components evenly, extrude and granulate at 180°C, and draw into 1.75mm wire.

[0086] Printing process: The ring-shaped permanent magnet generates a constant magnetic field with an intensity of 0.4T, and the printing temperature is 190℃ (PLA melting point +20℃).

[0087] Example 11 Material system (parts by weight): PCL / TPU blend matrix (mass ratio 1:1): 70 parts; magnetic response enhancement filler (carbon nanotube coated Ni): 27.5 parts; dispersant (titanium ester coupling agent): 2.0 parts; antioxidant 1010: 0.5 parts.

[0088] Preparation process: 1) Magnetic modification: Ni nanoparticles were coated on the surface of carbon nanotubes by chemical coprecipitation, with a thickness of 125 nm; 2) Blending extrusion: Mix the components in an internal mixer at 100℃, extrude and granulate, and draw into 1.75mm wire.

[0089] Printing process: The electromagnetic coil generates a constant magnetic field with a strength of 0.3T, and the printing temperature is 80℃ (the melting point of PCL / TPU blend +20℃).

[0090] Comparative Example Magnetic field-free printing Raw material composition: Same as in Example 1.

[0091] Printing process: Use a standard FDM printer without applying any external magnetic field.

[0092] Figure 1 This is a flowchart of the method for magnetic field-assisted 3D printing using a 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength, as disclosed in this invention. The flowchart shows the complete process flow from raw material preparation to the final product. Step S1 (Filler Magnetization Treatment): It is clarified that coating the fiber / whisker surface with magnetic nanoparticles is a prerequisite for achieving magnetic response. Step S2 (Composite Consumable Extrusion): The matrix and modified filler are blended and extruded into filaments. Step S3 (FDM Heating and Melting): The consumable enters the nozzle and melts; at this point, the fiber is mainly in a horizontal state due to shear force. Step S4 (In-situ Magnetic Field Control): This is the core of this invention. A vertical magnetic field is applied at the nozzle exit; the magnetic torque overcomes fluid resistance, forcing the fiber to "stand upright." Step S5 (Cooling and Shaping): The fiber is frozen in a vertical state, spanning the interlayer interface, ultimately forming a high-strength and tough Z-axis printed part.

[0093] Table 1. Test data on interlayer bonding performance of 3D printed parts made from magnetic field-assisted orientation-enhanced Z-axis strength composite materials prepared in each embodiment.

[0094] Table 1 shows the interlayer bonding performance test data of 3D printed parts with enhanced Z-axis strength using magnetic field-assisted orientation of 3D printed composite materials prepared in each embodiment. The Z-axis strength improvement rate is calculated based on the comparative example (without magnetic field). As can be seen from Table 1, compared with the comparative example, the Z-axis tensile strength of Examples 1-7, with the application of a vertical magnetic field, is significantly improved (40%~86%). This proves that the magnetic field successfully induced the vertical orientation of the fibers, forming an effective "interlayer micro-rivet" structure, overcoming the anisotropy defects of traditional FDM processes. In Example 7, due to the high filler content of 30% and the high viscosity of the PEEK matrix, a strong magnetic field of 0.8T was used, achieving the highest absolute strength and improvement rate, indicating that a strong magnetic field is crucial for orientation control in high-viscosity / high-filler systems. Example 8 used a 45° magnetic field angle, and its Z-axis strength improvement (38.1%) was lower than that of Example 1 with a vertical magnetic field (65.5%), but its strength in the X / Y axes was better preserved. This demonstrates that by changing the angle of the magnetic field, it is possible to achieve precise control over the anisotropy of the mechanical properties of materials.

[0095] In summary, this invention discloses a magnetically assisted orientation-enhanced Z-axis strength 3D printing composite consumable and its preparation and printing method. The composite consumable consists of a thermoplastic resin matrix and a magnetically responsive reinforcing filler, wherein the magnetically responsive reinforcing filler is a fibrous or whisker-like material with ferromagnetic nanoparticles coated on its surface. The accompanying printing method disclosed in this invention includes: applying an external magnetic field in a specific direction at the nozzle of a fused deposition modeling (FDM) machine; when the consumable is molten and extruded, the magnetically responsive reinforcing filler overcomes the melt shear resistance under the action of the magnetic field torque, undergoing directional deflection, changing from being aligned along the extrusion direction (X / Y axis) to being aligned along the interlayer stacking direction (Z axis) or at a preset angle, forming an interlayer reinforcement structure similar to "micro-steel nails." This effectively solves the problem of weak Z-axis mechanical properties in traditional fiber-reinforced 3D printing consumables due to the fiber's flow-oriented orientation. In traditional fused deposition modeling (FDM) technology, when a composite consumable containing reinforcing fibers is extruded through a printing nozzle, the strong shear force on the melt forces the fibers to be highly oriented along the extrusion direction (i.e., the horizontal X / Y axis direction). This inherent "shear-induced orientation" results in good mechanical properties in the horizontal direction of the printed part, but the interlayer bonding force perpendicular to the printing layer direction (Z-axis) is very weak, making it prone to interlayer cracking and limiting its application in load-bearing structures. This invention introduces a fiber core material with a surface coated with magnetic nanoparticles as a magnetically responsive reinforcing filler, and utilizes its ability to undergo directional deflection under an applied magnetic field in the molten state, effectively overcoming the limitations of shear-induced orientation in traditional FDM technology. By applying a vertical magnetic field during the printing process, glass fibers that might otherwise be arranged horizontally are actively induced to align vertically, thus forming a reinforcing structure across the interlayer interface. Unlike existing technologies where fibers passively align along the flow field direction, this invention achieves active control over the orientation of the reinforcing filler, significantly improving the Z-axis mechanical properties of the printed part and effectively solving the problem of weak Z-axis mechanical properties caused by the downstream orientation of fibers in traditional fiber-reinforced 3D printing consumables. In this way, the composite consumable of this invention can be used to manufacture 3D printed parts with higher structural integrity and reliability, broadening the scope of 3D printing technology in engineering applications.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A 3D printing composite consumable for enhancing Z-axis strength with magnetic field-assisted orientation, characterized in that, By weight, it includes: 70-95 parts thermoplastic resin matrix; 5-30 parts magnetically responsive reinforcing filler; 0.5-2.0 parts dispersant; 0.1-0.5 parts antioxidant; The magnetic response-enhancing filler is a fiber core material with a magnetic nanoparticle layer on its surface; the magnetic response-enhancing filler inside the 3D printing composite consumable with magnetic field-assisted orientation enhancement Z-axis strength can be oriented and deflected under the action of an external magnetic field in the molten state.

2. The 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength according to claim 1, characterized in that, The fiber core material is a fibrous or whisker-like material; the aspect ratio of the fibrous or whisker-like material is greater than 10.

3. The 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength according to claim 1, characterized in that, The thermoplastic resin matrix is ​​selected from one or more of polylactic acid, polycaprolactone, thermoplastic polyurethane, polyetheretherketone, and polycarbonate; the dispersant is selected from one or more of zinc stearate, ethylene bis-stearamide, polyethylene glycol, and titanate coupling agent; the antioxidant is selected from one or more of hindered phenolic antioxidant 1010, phosphite antioxidant 168, antioxidant 1076, and antioxidant 264.

4. The 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength according to claim 1, characterized in that, The magnetic nanoparticle layer is composed of iron oxide nanoparticles, nickel nanoparticles, or cobalt nanoparticles.

5. The 3D printing composite consumable with magnetic field-assisted orientation to enhance Z-axis strength according to claim 1, characterized in that, The fiber core material is: carbon fiber, glass fiber, potassium titanate whiskers or carbon nanotubes; the coating method includes: chemical coprecipitation, sol-gel method or electrostatic adsorption method; the thickness of the magnetic nanoparticle layer is 50-200 nm.

6. A method for preparing the 3D printing composite consumable with magnetic field-assisted orientation enhancement for Z-axis strength as described in any one of claims 1-5, characterized in that, include: After pretreatment of the fiber core material, it is dispersed in a magnetic nanoparticle solution and subjected to a chemical co-precipitation reaction to obtain a magnetic response-enhancing filler. The thermoplastic resin matrix, magnetic response-enhancing filler, dispersant and antioxidant are mixed evenly and extruded at 180-200℃ to obtain a 3D printing composite consumable with magnetic field-assisted orientation-enhanced Z-axis strength.

7. A method for magnetic field-assisted 3D printing using the magnetic field-assisted orientation-enhanced Z-axis strength 3D printing composite consumable as described in any one of claims 1-5, characterized in that, include: The 3D printing composite material with magnetic field-assisted orientation to enhance Z-axis strength is fed into the heated nozzle of the 3D printer for melting. A magnetic field is applied to the region where the melt leaves the nozzle but has not yet fully cooled and solidified; the magnetic response-enhancing filler in the melt rotates under the action of the magnetic field torque, aligns along the direction of the magnetic field lines, and cools and solidifies with the resin in this orientation state, forming an enhanced structure that spans the interface of the deposited layer.

8. The method for magnetic field-assisted 3D printing according to claim 7, characterized in that, The melting temperature is 20-40°C above the melting point of the matrix resin; the applied magnetic field is a constant magnetic field or an alternating magnetic field.

9. The method for magnetic field-assisted 3D printing according to claim 7, characterized in that, The magnetic field strength is 0.1-0.8T, and the magnetic field lines are perpendicular to the printing platform plane or at an angle of 45°-90° with the printing path.

10. The method for magnetic field-assisted 3D printing according to claim 7, characterized in that, The magnetic field is generated by a ring-shaped permanent magnet or an electromagnetic coil installed at the end of the 3D printer nozzle. The magnetic field generating device moves synchronously with the printing nozzle. The magnetic field strength is controlled by adjusting the current of the electromagnetic coil, thereby regulating the deflection angle of the magnetic response enhancement filler in the matrix and realizing the gradient distribution of anisotropic mechanical properties inside the printed part.

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