Coaxial coating preparation system and process for continuous fiber and aramid fiber reinforced 3D printing composite consumables

Abstract

The invention discloses a coaxial coating preparation system and process for continuous fiber and aramid fiber reinforced 3D printing composite consumables. Comprising a continuous fiber and aramid fiber unwinding unit, a constant tension control unit, a fiber depth pretreatment unit, a continuous fiber and aramid fiber composite pre-twisting unit, a melt extrusion unit, a coaxial dual-channel coating extrusion die head, a graded cooling and shaping unit, an online diameter measurement closed-loop control unit and a constant tension winding unit which are linked in sequence. The continuous fiber and aramid fiber unwinding unit, the constant tension control unit, the fiber depth pretreatment unit and other functional units are reasonably arranged, and the central control unit is used for achieving electric connection and overall regulation and control of all the units, so that a whole-process closed-loop system from raw material treatment to composite forming, cooling shaping, quality detection and winding storage in sequence is formed; and a parameter database and a linkage regulation and control module integrated by the central control unit can realize accurate coordination of the whole process of feeding, temperature control, forming and detection.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, specifically to a coaxial coating preparation system and process for continuous fiber and aramid-reinforced 3D printing composite consumables. Background Technology

[0002] FDM (Fused Deposition Modeling) 3D printing technology is increasingly widely used in industrial manufacturing, aerospace, and medical fields due to its advantages such as ease of operation and controllable cost. The performance of its core consumables directly determines the structural strength and functional stability of the printed parts. Current FDM 3D printing consumables mainly use single thermoplastic plastics such as PLA, ABS, PETG, TPU, and PA as raw materials. Meanwhile, the industry also explores improved solutions such as chopped fiber-filled materials, in-line or post-impregnation continuous fiber reinforcement materials, and core-sheathed composite filaments to attempt to enhance the mechanical properties and functional adaptability of the consumables.

[0003] However, existing technologies still have many insurmountable shortcomings: single thermoplastic consumables generally suffer from low tensile strength, insufficient rigidity, and poor creep resistance, failing to meet the application requirements of structural load-bearing components and functional components; chopped fiber-filled materials typically have fiber lengths less than 0.3 mm, which are further sheared during melt plasticization and extrusion, making it difficult to form an effective continuous load-bearing path and easily leading to nozzle wear, clogging, and decreased interlayer bonding performance; online lay-up or post-impregnation processes involve complex equipment structures, high motion control coupling, and high costs, making it difficult to achieve large-scale industrial applications; core-sheathed composite filaments suffer from problems such as the outer resin failing to wet between the fiber monofilaments, core fiber eccentricity, fiber exposure and delamination during printing, and poor interfacial bonding performance between aramid fibers and thermoplastics. Furthermore, existing related extrusion devices generally suffer from low coaxiality control accuracy, easy mixing of core material and coating layer, insufficient temperature control system adaptability, poor process coordination, and lack of online detection and feedback mechanisms, resulting in low yield rates and failing to guarantee stable production and application quality of composite consumables.

[0004] Therefore, there is an urgent need for a coaxial coating preparation system and process for continuous fiber and aramid reinforced 3D printing composite consumables with high integration, precise coaxiality control, good isolation between core material and coating layer, wide temperature control adaptability, strong process synergy, and real-time quality detection function, in order to solve the problems of insufficient material performance, poor production stability, and low product quality controllability in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a coaxial coating preparation system and process for continuous fiber and aramid-reinforced 3D printing composite consumables, so as to solve the problems existing in the prior art mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a coaxial coating preparation system and process for continuous fiber and aramid reinforced 3D printing composite consumables, comprising a continuous fiber and aramid unwinding unit, a constant tension control unit, a fiber depth pretreatment unit, a continuous fiber and aramid composite pretwisting unit, a melt extrusion unit, a coaxial dual-channel coating extrusion die, a graded cooling and shaping unit, an online diameter measurement closed-loop control unit, and a constant tension winding unit, all linked in sequence; and a central control unit that coordinates and regulates the continuous fiber and aramid unwinding unit, the constant tension control unit, the fiber depth pretreatment unit, the continuous fiber and aramid composite pretwisting unit, the melt extrusion unit, the coaxial dual-channel coating extrusion die, the graded cooling and shaping unit, the online diameter measurement closed-loop control unit, and the constant tension winding unit.

[0007] The continuous fiber and aramid unwinding unit, constant tension control unit, fiber depth pretreatment unit, continuous fiber and aramid composite pretwisting unit, melt extrusion unit, coaxial dual-channel coating extrusion die, graded cooling and shaping unit, online diameter measurement closed-loop control unit, and constant tension winding unit are sequentially connected via pipelines or circuits. The central control unit is electrically connected to the continuous fiber and aramid unwinding unit, constant tension control unit, fiber depth pretreatment unit, continuous fiber and aramid composite pretwisting unit, melt extrusion unit, coaxial dual-channel coating extrusion die, graded cooling and shaping unit, online diameter measurement closed-loop control unit, and constant tension winding unit, respectively. The central control unit integrates a parameter database and a linkage control module to regulate the entire process of material feeding, temperature control, molding, and testing.

[0008] Preferably, the fiber deep pretreatment unit includes a drying module, a surface activation module, and a fiber spreading module, wherein:

[0009] The drying module provides a processing environment with a temperature of 80-140 degrees Celsius and a humidity of <5%RH, and the fiber is processed in this environment for 30-120 seconds.

[0010] The surface activation module is activated by any of the following methods: plasma treatment, flame treatment, or silane coupling agent dipping.

[0011] The fiber spreading module increases the width of the fiber bundle by 2-5 times, and the single filament separation degree is ≥80%.

[0012] Preferably, the melt extrusion unit uses a single-screw or twin-screw extruder with a screw length-to-diameter ratio of 24-40, a compression ratio of 2.5-3.5, and a shear rate controlled at <500s⁻¹.

[0013] The coaxial dual-channel coating extrusion die includes a central fiber channel, a self-centering guide cone, an annular main flow channel, at least four equal-length symmetrical flow channels, a high-pressure impregnation chamber, and a precision sizing outlet die. The melt pressure in the high-pressure impregnation chamber reaches 5-15 MPa, and the diameter of the central fiber channel is 1.3-1.6 times the diameter of the composite core wire.

[0014] Specifically, when the zoned temperature control of the melt extrusion unit is adapted to TPU, the corresponding temperature control range is 170-210 degrees Celsius; when it is adapted to PA, the corresponding temperature control range is 210-260 degrees Celsius; and when it is adapted to PEEK, the corresponding temperature control range is 340-390 degrees Celsius.

[0015] Preferably, the staged cooling shaping unit includes a primary air-cooling component and a secondary water-cooling component;

[0016] The primary air-cooling system uses a ring-shaped air duct with an air velocity of 1-5 meters per second and a temperature of 20-30 degrees Celsius.

[0017] The length of the secondary water-cooling tank is 1-3 meters, and the water temperature is 15-35 degrees Celsius.

[0018] Preferably, the online diameter measurement closed-loop control unit includes a laser diameter gauge with an accuracy of ±1μm, an industrial computer, and a PID control algorithm. The online diameter measurement closed-loop control unit controls the wire diameter stability within the range of ≤±0.02 mm by adjusting the extruder speed and traction speed in real time.

[0019] A coaxial coating process for preparing a continuous fiber and aramid-reinforced 3D printing composite consumable, using the preparation system described in any one of the claims, comprises the following steps in sequence:

[0020] S1) Fiber pretreatment

[0021] Continuous fibers and aramid fibers are selected, and after drying, dehumidification, surface activation and fiber spreading treatment, they are pre-twisted at a mass ratio of 10:1-1:1 to form composite core yarns. The tension during the pre-twisting process is controlled at 5-50 cN.

[0022] S2) Raw material preparation

[0023] The outer layer is made of thermoplastic polymer material and dried, and the core material is the composite core wire prepared in step S1;

[0024] S3) Parameter Adjustment

[0025] The temperature control, feeding, traction and positioning parameters can be called by the central control unit or manually set, and the coaxiality deviation between the core material channel and the forming die is ≤0.005 mm.

[0026] S4) Coaxial overmolding

[0027] The composite core wire is conveyed under constant tension to the central channel of the coaxial dual-channel extrusion die. The outer layer of thermoplastic polymer is melted and plasticized by the melt extrusion unit and then impregnated with the composite core wire under high pressure through the annular flow channel and formed.

[0028] S5) Staged cooling and shaping

[0029] The consumables are cured by a first-stage air cooling and a second-stage water cooling process, with a wire diameter fluctuation of ≤±0.02 mm.

[0030] S6) Online detection and winding

[0031] The online diameter measurement closed-loop control unit monitors and adjusts the data in real time, and the finished products are cut to specifications and stored in a moisture-proof environment.

[0032] Preferably, the plasma treatment parameters for surface activation in step S1 are:

[0033] Power 100-500 W, processing time 0.5-3 s;

[0034] The pre-twist pitch is 10-80 mm, and the twist direction can be switched between S and Z directions.

[0035] Preferably, the temperature control parameters in step S3 are:

[0036] The temperature of the feed section of the melt extrusion unit is 100-150 ℃, the temperature of the compression section is 150-200 ℃, and the temperature of the melting section is 200-260 ℃;

[0037] The temperature of the coaxial dual-channel encapsulation extrusion die is 180-260 ℃, and the temperature difference between the die and the molten section is ≤5 ℃.

[0038] Preferably, the melt pressure in the high-pressure impregnation chamber in step S4 is 5-15 MPa, and the molten resin penetrates into the gap between the composite core wire monofilaments to form a micro-mechanical interlocking structure.

[0039] The coaxiality deviation of the core material of the prepared composite consumable is ≤0.01 mm, and the uniformity error of the coating thickness is ≤5%.

[0040] Preferably, in step S6, the finished product is cut to an accuracy of ±10 mm and is packaged in a nitrogen-filled sealed bag for moisture protection.

[0041] PLA and ASA consumables should be stored at room temperature (20-25℃) and humidity (≤60%).

[0042] TPU consumables should be stored at a temperature ≤30℃ and should be protected from heavy pressure.

[0043] Thermosensitive core material composite consumables should be stored refrigerated at 2-8 ℃.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1) This application rationally arranges functional units such as continuous fiber and aramid unwinding unit, constant tension control unit, and fiber depth pretreatment unit, and uses central control unit to realize electrical connection and overall control of each unit, forming a closed-loop system for the entire process from raw material processing to composite molding, cooling and shaping, quality inspection, winding and storage. The parameter database and linkage control module integrated in the central control unit can realize precise coordination of the entire process of material supply, temperature control, molding and inspection, avoid production failures caused by parameter disconnection in each link, and significantly improve the automation level and operational stability of the system.

[0046] 2) The fiber depth pretreatment unit of this application lays the foundation for the full impregnation of the molten resin through drying, surface activation and fiber spreading triple treatment. The self-centering guide cone and high-pressure impregnation chamber design of the coaxial dual-channel coating extrusion die, combined with the precise positioning mechanism, ensure that the coaxiality deviation of the core material is ≤0.01 mm. The molten resin can fully penetrate into the gap between the composite core filaments to form a micro-mechanical locking structure. The online diameter measurement closed-loop control unit adjusts the extruder speed and traction speed in real time through a laser diameter measuring instrument and PID control algorithm, strictly controlling the wire diameter stability within the range of ≤±0.02 mm. At the same time, the coating layer thickness uniformity error is ≤5%, which effectively solves the problems of core layer eccentricity, insufficient impregnation and large dimensional fluctuation in the prior art, and ensures the structural consistency and mechanical property stability of the printed parts.

[0047] 3) The melt extrusion unit of this application adopts a single-screw or twin-screw extruder. With a screw length-to-diameter ratio of 24-40, a compression ratio of 2.5-3.5, and precise control of shear rate <500s⁻¹, it can be adapted to various thermoplastic polymer materials such as TPU, PA, and PEEK. It also has dedicated temperature control ranges of 170-210 degrees Celsius, 210-260 degrees Celsius, and 340-390 degrees Celsius for different materials. The fiber depth pretreatment unit supports various surface activation methods such as plasma treatment, flame treatment, and silane coupling agent impregnation, which effectively improves the problem of strong chemical inertness of aramid fiber surface and enhances its interfacial bonding strength with thermoplastic polymer materials. The system can flexibly combine different types of continuous fibers, aramid fibers, and outer polymers to meet various functional requirements such as conductivity, high toughness, and flexibility. It is suitable for the production of conventional specifications of composite consumables such as 1.75 mm and 2.85 mm.

[0048] 4) This application establishes a standardized production process through standardized fiber pretreatment, parameter debugging, coaxial wrapping molding, and graded cooling and shaping. The parameter database built into the central control unit supports one-click access to parameters of consumables of different materials and specifications. Material changeover takes only 10-15 minutes, significantly shortening production preparation time. The graded cooling and shaping unit adopts a combination of primary air cooling and secondary water cooling to quickly solidify consumables and reduce internal stress. Combined with the PID closed-loop regulation of the constant tension control unit, it effectively avoids stretching deformation or breakage of consumables. The production speed can reach 0.5-5 meters per minute, which is more than 30% higher than traditional equipment. The yield rate is ≥98%, meeting the needs of large-scale industrial production.

[0049] 5) The online diameter measurement closed-loop control unit of this application integrates a laser diameter gauge with an accuracy of ±1 micrometer, a thickness sensor, and a surface defect detector to monitor wire diameter, coating thickness, and surface finish in real time. The detection data is fed back to the central control unit in real time. When parameter deviation occurs, it can be automatically adjusted to avoid the generation of batches of unqualified products. The central control unit can completely record the production process data of each batch of consumables, which facilitates quality traceability and problem investigation, reduces production risks, and provides reliable assurance for product quality control. Attached Figure Description

[0050] Figure 1 This is a schematic cross-sectional view of the coaxial co-extrusion die head of this application;

[0051] Figure 2 This is a process flow diagram for this application. Detailed Implementation

[0052] 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 embodiments of the present invention, and 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.

[0053] In the description of the invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0054] In the description of the invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0055] In the description of the invention, it should be noted that the execution order of the steps is not limited by the sequence number. The possible changes in the order of some steps, the synchronous execution of steps, and the split execution of steps are all within the scope of protection of this application.

[0056] Please see Figure 1-2 This invention provides a technical solution: a coaxial coating preparation system and process for continuous fiber and aramid reinforced 3D printing composite consumables, comprising a continuous fiber and aramid unwinding unit, a constant tension control unit, a fiber depth pretreatment unit, a continuous fiber and aramid composite pretwisting unit, a melt extrusion unit, a coaxial dual-channel coating extrusion die, a graded cooling and shaping unit, an online diameter measurement closed-loop control unit, and a constant tension winding unit, all linked in sequence; and a central control unit that coordinates and controls the continuous fiber and aramid unwinding unit, the constant tension control unit, the fiber depth pretreatment unit, the continuous fiber and aramid composite pretwisting unit, the melt extrusion unit, the coaxial dual-channel coating extrusion die, the graded cooling and shaping unit, the online diameter measurement closed-loop control unit, and the constant tension winding unit.

[0057] The continuous fiber and aramid unwinding unit, constant tension control unit, fiber depth pretreatment unit, continuous fiber and aramid composite pretwisting unit, melt extrusion unit, coaxial dual-channel coating extrusion die, graded cooling and shaping unit, online diameter measurement closed-loop control unit, and constant tension winding unit are sequentially connected via pipelines or circuits. The central control unit is electrically connected to the continuous fiber and aramid unwinding unit, constant tension control unit, fiber depth pretreatment unit, continuous fiber and aramid composite pretwisting unit, melt extrusion unit, coaxial dual-channel coating extrusion die, graded cooling and shaping unit, online diameter measurement closed-loop control unit, and constant tension winding unit, respectively. The central control unit integrates a parameter database and linkage control module to regulate the entire process of material feeding, temperature control, molding, and testing.

[0058] Specifically, the preparation system of this application fundamentally solves the problems of dispersed structure, high coupling degree of motion control of various components, and poor coordination in the existing composite consumable production equipment by means of sequential linkage of various functional units, pipeline or circuit connection methods, and overall control design of the central control unit over all functional units. Each functional unit forms a complete continuous production chain from raw material processing to composite molding, cooling and shaping, quality inspection, and winding and storage, avoiding production interruptions or quality fluctuations caused by the disconnection of various links in traditional equipment. The separate electrical connection design between the central control unit and each functional unit, combined with the integrated parameter database and linkage control module, achieves precise and coordinated control of the entire process of material supply, temperature control, molding, and inspection, breaking the limitations of independent parameter setting and lack of linkage in the existing technology, and significantly improving the automation level and operational stability of the system. At the same time, this integrated design simplifies the equipment structure, reduces the cost and maintenance difficulty of traditional complex equipment, provides reliable system support for the large-scale industrial production of composite consumables, and effectively solves the shortcomings of existing continuous fiber reinforcement schemes that are difficult to apply on a large scale.

[0059] Specifically, the central control unit uses a PLC controller with an integrated touchscreen display and a built-in parameter database for different materials and specifications. It supports the storage of more than 1,000 sets of production parameters and features parameter setting, status monitoring, and fault alarm functions. The constant tension control unit uses a PID closed-loop control algorithm with a response time of less than 20 milliseconds, an overshoot of less than 5%, a tension control range of 5-50 cN, and a control accuracy better than ±1%. The parameter database built into the central control unit not only contains temperature control curves for different materials (such as TPU, PA, and PEEK), but also stores process parameters such as pre-twisting tension, twist pitch, and traction speed for corresponding fiber combinations. It supports one-click recall and custom saving of more than 1,000 sets of production parameters. When switching to produce consumables of different specifications or materials, simply selecting the corresponding parameter set on the touchscreen display completes the automatic adaptation of equipment parameters, reducing material changeover time to 10-15 minutes and significantly improving production efficiency and equipment flexibility.

[0060] The fiber deep pretreatment unit includes a drying module, a surface activation module, and a fiber spreading module, wherein:

[0061] The drying module provides a processing environment with a temperature of 80-140 degrees Celsius and a humidity of <5%RH, and the fiber is processed in this environment for 30-120 seconds.

[0062] The surface activation module employs any of the following methods: plasma treatment, flame treatment, or silane coupling agent impregnation coating;

[0063] The fiber spreading module increases the width of the fiber bundle by 2-5 times, and the single filament separation degree is ≥80%.

[0064] Specifically, the drying module provides a precise temperature and humidity environment that thoroughly removes moisture adsorbed on the fiber surface, preventing air bubbles from forming due to moisture evaporation during subsequent extrusion and ensuring the density of the composite consumable's internal structure. The surface activation module offers multiple treatment methods that can flexibly adapt to different fiber characteristics, effectively introducing polar functional groups onto the aramid fiber surface, overcoming its strong surface chemical inertness, and significantly improving the interfacial bonding strength between the fiber and the outer thermoplastic polymer material, reducing the risk of delamination and fiber exposure during printing. The fiber spreading module expands the fiber bundle width by 2-5 times and ensures a single filament separation rate of no less than 80%, transforming the fiber bundle from an aggregated state to a dispersed single filament state. This creates sufficient contact area for the subsequent high-pressure impregnation of the molten resin, ensuring that the resin can penetrate into the gaps between each single filament, forming a stable load-bearing structure, and laying a key foundation for improving the mechanical properties of the composite consumable.

[0065] Specifically, the constant tension control unit adopts a PID closed-loop control algorithm with a response time of <20ms and an overshoot of <5%. It can maintain a stable tension of 5-50cN throughout the entire process of fiber unwinding, pre-twisting, and coating, avoiding fiber stretching deformation or relaxation due to tension fluctuations. This ensures the orientation consistency and structural stability of the composite core yarn, providing a high-quality core material foundation for subsequent coating molding.

[0066] The melt extrusion unit uses a single-screw or twin-screw extruder with a screw length-to-diameter ratio of 24-40, a compression ratio of 2.5-3.5, and a shear rate controlled at <500s⁻¹.

[0067] The coaxial dual-channel coating extrusion die includes a central fiber channel, a self-centering guide cone, an annular main flow channel, at least four equal-length symmetrical flow channels, a high-pressure impregnation chamber, and a precision sizing outlet die. The melt pressure in the high-pressure impregnation chamber reaches 5-15 MPa, and the diameter of the central fiber channel is 1.3-1.6 times the diameter of the composite core wire.

[0068] Specifically, when the zoned temperature control of the melt extrusion unit is adapted to TPU, the corresponding temperature control range is 170-210 degrees Celsius; when the zoned temperature control is adapted to PA, the corresponding temperature control range is 210-260 degrees Celsius; and when the zoned temperature control is adapted to PEEK, the corresponding temperature control range is 340-390 degrees Celsius.

[0069] Specifically, the melt extrusion unit features a screw length-to-diameter ratio of 24-40 and a compression ratio of 2.5-3.5, coupled with a shear rate control of less than 500s⁻¹. This ensures the full melting and plasticization of thermoplastic polymer materials while preventing resin degradation caused by excessive shearing, thus guaranteeing the stability of the outer layer material's performance. The coaxial dual-channel encapsulated extrusion die's central fiber channel, self-centering guide cone, and high-pressure impregnation chamber work synergistically to achieve precise positioning of the composite core filament, significantly reducing the coaxiality deviation of the core material. Simultaneously, the 5-15 MPa high-pressure impregnation chamber pressure forces the molten resin to fully penetrate the gaps between the composite core filaments, forming a micro-mechanical locking structure. This completely solves the problem of traditional "skin-wrapped core" wires only covering the surface and lacking sufficient impregnation. The dedicated zoned temperature control ranges designed for different materials such as TPU, PA, and PEEK allow the system to accurately match the melting characteristics of various materials, breaking the limitations of the existing equipment's single temperature control mode and expanding the material combination space of composite consumables to meet the production of products with different functional requirements.

[0070] Specifically, the coaxial dual-channel encapsulation extrusion die head features a flow channel isolation structure with a width of 0.2-0.5mm, filled with a sealing material with a temperature resistance of ≥300℃. This effectively isolates the core material channel from the outer melt flow channel, preventing core layer contamination caused by premature mixing of the core material and molten polymer. The precision sizing outlet die head has a detachable design, supporting quick replacement of dies with different inner diameters such as 1.75mm and 2.85mm, adapting to the production needs of various consumable specifications. Furthermore, the inner wall roughness of the die is Ra≤0.8μm, ensuring the surface smoothness of the consumables.

[0071] Reference manual attached Figure 1 The continuous fiber core material is conveyed into the guide tip under constant tension. The self-centering structure of the guide tip ensures that the core material is always on the central axis of the die head, controlling the coaxiality deviation between the core material channel and the forming die within ≤0.005mm, thus solving the problem of core layer eccentricity in traditional coating processes. The outer layer of molten polymer enters the die body through the molten polymer inlet. The annular main distribution cavity and symmetrical distribution channels inside the die body evenly distribute the melt. Then, the melt is forced to penetrate into the gaps between the single filaments of the composite core filament through the high-pressure wetting chamber (5-15MPa pressure), forming a micro-mechanical locking structure, completely solving the defect of insufficient wetting in existing technologies. The composite consumables that have completed high-pressure wetting and coating are finally precision sized and formed through the coated consumables outlet. Combined with subsequent graded cooling and online detection, the wire diameter stability is ensured to be ≤±0.02mm and the coating layer thickness uniformity error is ≤5%, providing key structural support for the stable production of high-performance composite consumables.

[0072] The staged cooling unit includes a primary air-cooled component and a secondary water-cooled component;

[0073] The primary air-cooling system uses a ring-shaped air duct with an air velocity of 1-5 meters per second and a temperature of 20-30 degrees Celsius.

[0074] The length of the secondary water-cooling tank is 1-3 meters, and the water temperature is 15-35 degrees Celsius.

[0075] Specifically, the primary air cooling system employs a ring-shaped air duct with a wind speed of 1-5 meters per second and a temperature design of 20-30 degrees Celsius. This allows for the rapid formation of a pre-cured shell on the surface of the consumable, preventing wrinkles or deformation during subsequent water cooling and simultaneously fixing the shape of the consumable. The secondary water cooling tank, with a length of 1-3 meters and a water temperature setting of 15-35 degrees Celsius, ensures complete curing of the consumable from the surface to the core, thoroughly releasing the internal stress generated during production and preventing deformation or cracking caused by stress release during subsequent storage or printing. This staged combination of air and water cooling balances cooling efficiency and quality, enabling the consumable to maintain dimensional stability while rapidly shaping, effectively controlling wire diameter fluctuations. This provides a solid foundation for subsequent online inspection and winding processes, ensuring the shape accuracy and structural integrity of the composite consumable.

[0076] The online diameter measurement closed-loop control unit includes a laser diameter gauge with an accuracy of ±1μm, an industrial computer, and a PID control algorithm. This control unit maintains wire diameter stability within ≤±0.02 mm by real-time adjustment of the extruder speed and traction speed. Specifically, the ±1μm laser diameter gauge accurately captures wire diameter data in real time. Combined with the industrial computer and PID control algorithm, this forms a complete closed-loop control system, overcoming the limitations of traditional equipment where detection and production are disconnected. By adjusting the extruder speed and traction speed in real time, the unit strictly controls wire diameter stability within ≤±0.02 mm, effectively avoiding issues of excessively thick or thin wires caused by mismatches in feeding and extrusion speeds. This real-time monitoring and immediate adjustment design can promptly detect and correct wire diameter deviations during production, eliminating the need for post-production quality inspection. This significantly reduces the probability of batch defects, substantially improves the yield rate, and ensures the consistency of wire diameter in each batch, providing crucial assurance for the stability of the 3D printing process and the quality of printed parts.

[0077] Specifically, in addition to wire diameter monitoring and PID control functions, the online diameter measurement closed-loop control unit also integrates a surface defect detector, which can identify defects such as scratches, bubbles, and pits on the surface of consumables in real time. It can also trigger alarms or automatically adjust process parameters through the central control unit to further reduce the defect rate. At the same time, the detection data and production parameters are stored synchronously, which can realize the quality traceability of each meter of consumables and provide data support for subsequent process optimization.

[0078] According to another aspect of this application, a coaxial coating preparation process for a continuous fiber and aramid-reinforced 3D printing composite consumable is also provided, comprising the following steps in sequence:

[0079] S1) Fiber pretreatment

[0080] Continuous fibers and aramid fibers are selected, and after drying, dehumidification, surface activation and fiber spreading treatment, they are pre-twisted at a mass ratio of 10:1-1:1 to form composite core yarns. The tension during the pre-twisting process is controlled at 5-50 cN.

[0081] S2) Raw material preparation

[0082] The outer layer is made of thermoplastic polymer material and dried, and the core material is the composite core wire prepared in step S1;

[0083] S3) Parameter Adjustment

[0084] The temperature control, feeding, traction and positioning parameters can be called by the central control unit or manually set, and the coaxiality deviation between the core material channel and the forming die is ≤0.005 mm.

[0085] S4) Coaxial overmolding

[0086] The composite core wire is conveyed under constant tension to the central channel of the coaxial dual-channel extrusion die. The outer layer of thermoplastic polymer is melted and plasticized by the melt extrusion unit and then impregnated with the composite core wire under high pressure through the annular flow channel and formed.

[0087] S5) Staged cooling and shaping

[0088] The consumables are cured by a first-stage air cooling and a second-stage water cooling process, with a wire diameter fluctuation of ≤±0.02 mm.

[0089] S6) Online detection and winding

[0090] The online diameter measurement closed-loop control unit monitors and adjusts the data in real time, and the finished products are cut to specifications and stored in a moisture-proof environment.

[0091] Specifically, the fiber pretreatment step forms a composite core filament through pre-twisting and controls tension to ensure a stable core filament structure and consistent orientation, providing a high-quality core material for subsequent overcoating. The raw material preparation step dries the inner and outer layer raw materials, avoiding the impact of moisture on molding quality. The parameter adjustment step, using preset parameters from the central control unit or manual settings, quickly adapts to different materials and specifications, shortening production preparation time. The coaxial overcoating step achieves precise bonding between the core filament and the outer melt, forming a rational structure of "core functional material and outer polymer." The staged cooling and shaping step ensures the curing quality and dimensional stability of the consumables. The online detection and winding step ensures controllable finished product quality through real-time feedback adjustments. The entire process is logically coherent and tightly integrated, with standardized parameters and operations in each step, improving production efficiency, ensuring consistent product quality, and supporting rapid switching between different specifications and functions of consumables to meet the needs of large-scale production and diversified demands.

[0092] The plasma treatment parameters for surface activation in step S1 are as follows:

[0093] Power 100-500 W, processing time 0.5-3 s;

[0094] The pre-twist pitch is 10-80 mm, and the twist direction can be switched between S and Z directions.

[0095] Specifically, this application addresses the problems of unstable surface activation, loose pre-twisted structure, and insufficient core filament toughness in existing technologies. The plasma power of 100-500 watts and processing time of 0.5-3 seconds allow for precise control of the activation level based on fiber characteristics, ensuring sufficient polar functional groups are introduced onto the aramid fiber surface while avoiding over-treatment that could damage the fiber itself, thus ensuring the stability of the interfacial bonding strength. The pre-twisting pitch of 10-80 mm and switchable S- and Z-directions allow for flexible adaptation to different fiber combinations and subsequent printing requirements, enabling continuous fibers to tightly bond with aramid fibers to form a structurally stable composite core filament, preventing core filament loosening or breakage during production or printing. Tension control of 5-50 centinewtons during pre-twisting ensures the fiber remains axially straight, improving the core filament's orientation and load-bearing capacity, providing crucial support for enhancing the overall mechanical properties of the composite consumable. Simultaneously, the stable core filament structure reduces the risk of core layer eccentricity during subsequent coating processes.

[0096] The temperature control parameters in step S3 are:

[0097] The temperature of the feed section of the melt extrusion unit is 100-150 ℃, the temperature of the compression section is 150-200 ℃, and the temperature of the melting section is 200-260 ℃;

[0098] The coaxial dual-channel coating extrusion die has a flow channel temperature of 180-260 ℃, with a temperature difference of ≤5 ℃ between the flow channel and the melting section.

[0099] Specifically, this application solves the problems of single temperature control mode, large temperature fluctuation, uneven resin melting, and easy deformation of core material in the prior art. The three-stage temperature control design of the melt extrusion unit—100-150 degrees Celsius in the feeding section, 150-200 degrees Celsius in the compression section, and 200-260 degrees Celsius in the melting section—conforms to the gradual transition of thermoplastic polymers from solid to molten state, ensuring gradual melting and uniform plasticization of the material and avoiding resin degradation caused by local overheating or molding defects caused by local unmelted areas. The coaxial dual-channel encapsulation extrusion die has a flow channel temperature of 180-260 degrees Celsius, with a temperature difference of no more than 5 degrees Celsius from the melting section. This design prevents the molten resin from solidifying due to a sudden drop in temperature within the flow channel, ensuring the fluidity of the melt and the continuity of the encapsulation. The precise temperature control range set for different material properties not only adapts to the melting requirements of the outer polymer layer but also avoids the deformation of the heat-sensitive core material due to high temperatures through reasonable temperature control. This balances the molding quality of the outer layer with the functional stability of the core material, solving the shortcomings of traditional single temperature control modes that cannot accommodate different material properties.

[0100] In step S4, the melt pressure in the high-pressure impregnation chamber is 5-15 MPa, and the molten resin penetrates into the gap between the single filaments of the composite core wire to form a micro-mechanical interlocking structure.

[0101] The coaxiality deviation of the core material of the prepared composite consumable is ≤0.01 mm, and the uniformity error of the coating thickness is ≤5%.

[0102] Specifically, a melt pressure of 5-15 MPa forces the molten resin to penetrate into the gaps between the single filaments of the composite core filament, completely changing the limitation of traditional coating which only stays on the surface of the fiber bundle. This forms a micro-mechanical interlocking structure, significantly improving the interfacial bonding strength between the core material and the coating layer, and avoiding delamination and fiber exposure during the printing process. The coaxiality deviation of the core material of the prepared composite consumable does not exceed 0.01 mm, and the thickness uniformity error of the coating layer does not exceed 5%, ensuring the symmetry and consistency of the cross-sectional structure of the consumable. This makes the filament feeding resistance of the consumable uniform during 3D printing, and the mechanical properties of the printed parts are evenly distributed. This solves the problem of insufficient local strength of the printed parts caused by uneven structure, and significantly improves the performance and reliability of the composite consumable.

[0103] In step S6, the finished product is cut to an accuracy of ±10 mm and is packaged in a nitrogen-filled sealed bag for moisture protection.

[0104] PLA and ASA consumables should be stored at room temperature (20-25℃) and humidity (≤60%).

[0105] TPU consumables should be stored at a temperature ≤30℃ and should be protected from heavy pressure.

[0106] Thermosensitive core material composite consumables should be stored refrigerated at 2-8 ℃.

[0107] Specifically, the ±10 mm cutting precision ensures the consistency of length for each roll of consumables, facilitating user operation and storage management. The nitrogen-filled sealed bag moisture-proof packaging design effectively isolates moisture in the air, preventing issues such as printhead clogging and air bubbles that may occur when PLA, ASA, TPU, and other materials absorb moisture. Dedicated storage conditions are designed for different types of consumables: a room temperature of 20-25 degrees Celsius and humidity not exceeding 60% is suitable for PLA and ASA consumables; a temperature not exceeding 30 degrees Celsius and avoiding heavy pressure is suitable for TPU consumables; and a refrigerated environment of 2-8 degrees Celsius is suitable for heat-sensitive core material composite consumables. This maximizes the protection of the physical properties and chemical stability of the consumables, extends their shelf life, and prevents material degradation and mechanical property decline caused by improper storage, ensuring that the consumables maintain good molding effects and functional stability during user operation.

[0108] Specifically, color masterbatch additives can be added during the production process as needed. After being mixed with the outer thermoplastic polymer material, the mixture is melted and plasticized to achieve customized color for the composite consumables. The color masterbatch dispersion uniformity is ≥95%, with no obvious color blocks or stripes. After the finished consumables are packaged in nitrogen-filled sealed bags, under suitable storage conditions, the shelf life of PLA and ASA consumables can reach 12 months, TPU consumables can reach 9 months, and thermosensitive core composite consumables can reach 6 months, effectively ensuring the long-term performance stability of the consumables.

[0109] Example 1: Preparation of 3D printing consumables made of aramid and continuous PA fiber reinforced nylon composite

[0110] This embodiment uses the coaxial coating preparation system for continuous fiber and aramid-reinforced 3D printing composite consumables of this application, and is produced according to the preparation process of this application, as follows:

[0111] 1. Raw material selection

[0112] Core layer material: 1000D aramid fiber and continuous PA filament are selected and compounded at a mass ratio of 5:1;

[0113] Outer layer material: PA12 thermoplastic polymer material is selected, with an appropriate amount of color masterbatch additives.

[0114] 2. Process parameter settings

[0115] S1) Fiber pretreatment

[0116] Aramid fibers and continuous PA filaments are fed into a fiber deep pretreatment unit. The drying module provides a treatment environment of 120 degrees Celsius and humidity <5%RH, in which the fibers are treated for 60 seconds. Surface activation is performed by plasma treatment, with the plasma power set at 300W and the treatment time at 1.5s. After treatment by the fiber spreading module, the fiber bundle width is increased by 3 times, and the single filament separation degree is ≥85%. Subsequently, a composite core yarn is formed by pre-twisting the continuous fiber and aramid composite pre-twisting unit. The pre-twisting tension is controlled at 25cN, the twist pitch is set at 40mm, and the twist direction is S-direction.

[0117] S2) Raw material preparation

[0118] The outer PA12 material and color masterbatch additives are mixed and fed into the hopper of the melt extrusion unit. The hopper has a built-in drying device that dries the material at 60 degrees Celsius to ensure that the dew point is ≤-40℃. The core material is a composite core wire prepared by S1.

[0119] S3) Parameter Adjustment

[0120] The central control unit calls the preset parameters corresponding to PA12 to set the temperature of the melt extrusion unit's feeding section to 130 degrees Celsius, the compression section to 180 degrees Celsius, and the melting section to 240 degrees Celsius; the temperature of the coaxial dual-channel encapsulation extrusion die head flow channel is 235 degrees Celsius, with a temperature difference of ≤5 degrees Celsius from the melting section; the core material positioning structure is adjusted to ensure that the coaxiality deviation between the core material channel and the forming die is ≤0.005 mm; and the traction speed is set to 2 m / min.

[0121] S4) Coaxial overmolding

[0122] The composite core filament is conveyed to the central channel of the coaxial dual-channel coating extrusion die via a constant tension control unit. The diameter of the central fiber channel is 1.4 times the diameter of the composite core filament. The outer PA12 material is melted and plasticized by the melt extrusion unit. The screw length-to-diameter ratio is set to 30, the compression ratio is 3.0, and the shear rate is controlled at 400s⁻¹. The molten PA12 enters the high-pressure impregnation chamber through the annular flow channel. The melt pressure in the chamber is stabilized at 12 MPa, forcibly penetrating into the gap between the composite core filaments and completing the coating molding. The forming die is a detachable structure with an inner diameter of 1.85mm.

[0123] S5) Staged cooling and shaping

[0124] After being coated and molded, the composite consumable is first treated by a primary air-cooling component, with the wind speed in the annular air duct set at 3 m / s and the temperature at 25 degrees Celsius, to form a preliminary surface curing shell; then it enters a secondary water-cooling tank, which is 2 m long and has a water temperature of 20 degrees Celsius, to achieve complete curing.

[0125] S6) Online detection and winding

[0126] The online diameter measurement closed-loop control unit monitors the wire diameter in real time using a laser diameter gauge with an accuracy of ±1μm. Combined with a PID control algorithm, it adjusts the extruder speed and traction speed to keep the wire diameter stable within the range of ≤±0.02 mm. The finished product is cut in 500m / roll with a cutting accuracy of ±10mm. It is packaged in a nitrogen-filled sealed bag for moisture protection and stored in an environment with a temperature of 20-25 degrees Celsius and a humidity of ≤60%.

[0127] 3. Finished Product Performance

[0128] The prepared composite consumable has a wire diameter of 1.75±0.02mm, a core material coaxiality deviation of ≤0.01mm, and a coating layer thickness uniformity error of ≤4%. According to the test, its tensile strength is 6.5 times higher than that of single PA12 consumable, and the core material and coating layer interface are tightly bonded without delamination.

[0129] Example 2: Preparation of Continuous Fiber Reinforced TPU Flexible Composite 3D Printing Consumables

[0130] This embodiment uses the coaxial coating preparation system for continuous fiber and aramid-reinforced 3D printing composite consumables of this application, and is produced according to the preparation process of this application, as follows:

[0131] 1. Raw material selection

[0132] Core layer material: Continuous PA filaments are selected as the core layer reinforcement material;

[0133] Outer layer material: TPU85A flexible thermoplastic polymer material is selected.

[0134] 2. Process parameter settings

[0135] S1) Fiber pretreatment

[0136] The continuous PA filament is fed into the fiber deep pretreatment unit. The drying module provides a treatment environment of 100 degrees Celsius and humidity <5%RH for 45 seconds. Surface activation is carried out by silane coupling agent impregnation. After treatment by the fiber spreading module, the fiber bundle width is increased by 2.5 times and the single filament separation degree is ≥82%. No additional pre-twisting is required (single continuous fiber core material), and the tension is controlled at 15cN.

[0137] S2) Raw material preparation

[0138] The outer TPU85A material is fed into the hopper of the melt extrusion unit and dried at 40 degrees Celsius, with a dew point ≤ -40℃; the core material is continuous PA filament treated with S1.

[0139] S3) Parameter Adjustment

[0140] The parameters for adapting to TPU are manually set through the central control unit: the temperature of the feed section of the melt extrusion unit is 120 degrees Celsius, the temperature of the compression section is 160 degrees Celsius, and the temperature of the melting section is 190 degrees Celsius; the temperature of the coaxial dual-channel encapsulation extrusion die is 185 degrees Celsius, with a temperature difference of ≤5 degrees Celsius from the melting section; the coaxiality deviation between the core material channel and the forming die is ≤0.005 mm; and the traction speed is set to 1.5 m / min.

[0141] S4) Coaxial overmolding

[0142] Continuous PA filaments are conveyed under constant tension to the central channel of the coaxial dual-channel coating extrusion die. The diameter of the central fiber channel is 1.3 times the diameter of the core filament. The outer TPU85A is melted and plasticized in the melt extrusion unit. The screw has a length-to-diameter ratio of 28, a compression ratio of 2.8, and a shear rate controlled at 350s⁻¹. The molten TPU enters the high-pressure impregnation chamber, where the melt pressure is stabilized at 8 MPa. After fully impregnating the core filament, the coating is completed. The inner diameter of the forming die is adapted to a 1.75mm specification.

[0143] S5) Staged cooling and shaping

[0144] The primary air-cooled component has a wind speed of 2m / s and a temperature of 22 degrees Celsius; the secondary water-cooled tank is 1.5m long and has a water temperature of 18 degrees Celsius, achieving gradient cooling and curing of consumables.

[0145] S6) Online detection and winding

[0146] The online diameter measurement closed-loop control unit monitors and provides feedback adjustments in real time to ensure that the wire diameter fluctuation is ≤ ±0.02 mm; the finished product is cut into 300m / rolls, packaged in nitrogen-filled sealed bags for moisture protection, and stored at a temperature ≤ 30 degrees Celsius while avoiding heavy pressure.

[0147] 3. Finished Product Performance

[0148] The prepared TPU flexible composite material has a bending radius of <5mm, and after 500 repeated bends, there is no delamination or cracking; the core material coaxiality deviation is ≤0.008mm, and the coating layer thickness uniformity error is ≤3%. It has both flexibility and high strength characteristics, and is suitable for the 3D printing needs of flexible structural parts.

[0149] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coaxial covering system for continuous fiber and aramid reinforced 3D printing composite consumables, characterized in that, The continuous fiber and aramid unwinding unit, the constant tension control unit, the fiber deep pretreatment unit, the continuous fiber and aramid composite pre-twist unit, the melt extrusion unit, the coaxial double-channel covering extrusion die, the staged cooling and shaping unit, the online diameter measurement closed-loop control unit and the constant tension winding unit are sequentially linked through pipelines or circuits, and the central control unit is electrically connected with the continuous fiber and aramid unwinding unit, the constant tension control unit, the fiber deep pretreatment unit, the continuous fiber and aramid composite pre-twist unit, the melt extrusion unit, the coaxial double-channel covering extrusion die, the staged cooling and shaping unit, the online diameter measurement closed-loop control unit and the constant tension winding unit, and the central control unit integrates a parameter database and a linkage control module to control the whole process of feeding, temperature control, molding and detection. The fiber deep pretreatment unit comprises a drying module, a surface activation module and a fiber spreading module.

2. The continuous fiber and aramid reinforced 3D printing composite co-axial covering preparation system according to claim 1, wherein, The drying module provides a treatment environment with a temperature of 80-140 DEG C and a humidity of < 5% RH, and the fiber is treated in the environment for 30-120 seconds. The surface activation module adopts any one of plasma treatment, flame treatment or silane coupling agent immersion coating. The fiber spreading module expands the width of the fiber bundle by 2-5 times, and the single filament separation degree is ≥ 80%. The melt extrusion unit adopts a single screw or a double screw extruder, the screw length-diameter ratio is 24-40, the compression ratio is 2.5-3.5, and the shear rate is controlled to be < 500 s-1.

3. The continuous fiber and aramid reinforced 3D printing composite co-axial covering preparation system according to claim 1, wherein, The coaxial double-channel covering extrusion die comprises a central fiber channel, a self-centering guide cone, an annular main shunt cavity, at least 4 equal-length symmetric shunt flow channels, a high-pressure infiltration cavity and a precision diameter setting outlet die hole, the melt pressure of the high-pressure infiltration cavity reaches 5-15 MPa, and the diameter of the central fiber channel is 1.3-1.6 times the diameter of the composite core wire. The partition temperature control of the melt extrusion unit is adapted to TPU, and the corresponding temperature control range is 170-210 DEG C; the partition temperature control is adapted to PA, and the corresponding temperature control range is 210-260 DEG C; and the partition temperature control is adapted to PEEK, and the corresponding temperature control range is 340-390 DEG C. The staged cooling and shaping unit comprises a primary air cooling assembly and a secondary water cooling assembly.

4. The continuous fiber and aramid reinforced 3D printing composite co-axial covering preparation system according to claim 1, wherein, The primary air cooling adopts an annular air duct, the air speed is 1-5 m / s, and the temperature is 20-30 DEG C. The secondary water cooling tank has a length of 1-3 m, and the water temperature is 15-35 DEG C. ​ 5. The continuous fiber and aramid reinforced 3D printing composite co-axial covering preparation system according to claim 1, wherein, The online diameter measurement closed-loop control unit comprises a laser diameter gauge with a precision of ±1 μm, an industrial computer and a PID control algorithm, and controls the diameter stability within a range of ≤±0.02 mm by adjusting the rotating speed of the extruder and the traction speed in real time.

6. A coaxial covering preparation process of continuous fiber and aramid reinforced 3D printing composite consumables, characterized in that, The preparation system according to any one of claims 1 to 5 comprises the following steps in sequence: S1) fiber pretreatment Continuous fibers and aramid fibers are selected, dried and dehumidified, surface activated and spread, and then pre-twisted to form a composite core yarn at a mass ratio of 10:1-1:1, with the tension control during the pre-twisting process being 5-50 cN; S2) raw material preparation The outer layer is made of thermoplastic polymer material after drying treatment, and the core material is the composite core yarn prepared in step S1; S3) parameter adjustment The temperature control, feeding, traction and positioning parameters are set by the central control unit or manually, and the coaxiality deviation between the core material channel and the forming die is ≤0.005 mm; S4) coaxial covering forming The composite core yarn is transported to the center channel of the coaxial double-channel covering extrusion die under constant tension, and the outer layer of thermoplastic polymer is melted and plasticized by the melt extrusion unit, then it is immersed and covered by the composite core yarn through the annular flow channel under high pressure; S5) staged cooling and shaping The material is solidified by first air cooling and then water cooling, and the diameter fluctuation is ≤±0.02 mm; S6) online detection and winding The finished product is cut according to the specification and stored in a moisture-proof manner after real-time monitoring and feedback adjustment by the online diameter measurement closed-loop control unit.

7. The process of claim 6, wherein the process further comprises the step of: The plasma treatment parameters for surface activation in step S1 are: ​ Power: 100-500 W, treatment time: 0.5-3 s; The twist pitch of pre-twisting is 10-80 mm, and the twist direction can be switched between S and Z directions.

8. The coaxial coating preparation process of the continuous fiber and aramid-reinforced 3D printing composite consumable according to claim 6, characterized in that, The temperature control parameters in step S3 are: The temperature of the melt extrusion unit is 100-150 ℃ at the feeding section, 150-200 ℃ at the compression section, and 200-260 ℃ at the melting section; The temperature of the coaxial double-channel covering extrusion die is 180-260 ℃, and the temperature difference with the melting section is ≤5 ℃.

9. The process of claim 6, wherein the process is characterized by, The melt pressure of the high-pressure immersion cavity in step S4 is 5-15 MPa, and the molten resin penetrates into the gap between the composite core yarn filaments to form a micro mechanical locking structure; The coaxiality deviation of the prepared composite consumable core material is ≤0.01 mm, and the uniformity error of the coating layer thickness is ≤5%.

10. The process of claim 6, wherein the process is characterized by, In step S6, the cutting accuracy of the finished product is ±10 mm, and the product is packaged in a nitrogen-filled sealed bag to prevent moisture; PLA and ASA consumables are stored at room temperature 20-25 ℃ and humidity ≤60%, TPU consumables are stored at a temperature ≤30 ℃ and avoid heavy pressure, Thermosensitive core material composite consumables are stored in a refrigerator at 2-8 ℃.

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