Preparation method of 3D printing material for straw fiber stage treatment

Abstract

The invention relates to the technical field of straw fiber material preparation, in particular to a straw fiber grading treatment 3D printing material preparation method which comprises the following steps: S1, a straw fiber grading treatment stage; s2, a raw material pretreatment stage; s3, a mixing and modifying stage; s4, a granulation and 3D printing adaptation stage; s5, an inspection and packaging stage; the raw materials are prepared from 55 parts of PLA, 20 parts of straw coarse fibers, 15 parts of straw fine fibers, 4 parts of maleic anhydride grafted POE, 3 parts of glycerin, 2 parts of talcum powder and 1 part of antioxidant according to 100 parts of total materials. The invention aims to provide the preparation method of the 3D printing material for straw fiber grading treatment to solve the problems that straw fibers are not subjected to precise grading treatment in most existing straw fiber material preparation, only fibers with single particle size are adopted for processing, the structural compactness and the mechanical enhancement effect of the material are difficult to consider at the same time, and the processing cost is low. And gaps exist in a finished product, and the performance is unbalanced.

Description

Technical Field

[0001] This invention relates to the field of straw fiber material preparation technology, specifically a method for preparing 3D printing materials by graded processing of straw fibers. Background Technology

[0002] The preparation of straw fiber materials is a process that uses agricultural waste straw as the core raw material. Through a series of processes such as crushing, screening, pretreatment, and composite modification, straw fiber is fused with polymer matrix, auxiliary additives, etc., and transformed into a new material with specific performance characteristics. Its core goal is to realize the resource reuse of straw, while expanding the application scenarios of biomass materials in different fields, and combining environmental protection value and practical value. Most existing straw fiber material preparations do not involve precise grading of straw fibers, but only use fibers of a single particle size for processing. This makes it difficult to balance the material's structural density and mechanical reinforcement, and can easily lead to problems such as voids and uneven performance in the finished product. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing 3D printing materials by graded processing of straw fibers, in order to solve the problems in the above-mentioned background technology where most existing straw fiber material preparations do not perform precise grading of straw fibers, but only use single-size fibers for processing, which makes it difficult to take into account both the structural density and mechanical reinforcement effect of the material, and easily leads to problems such as voids and uneven performance in the finished product.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing 3D printing materials by graded processing of straw fibers, the preparation method comprising the following steps: S1. In the straw fiber grading stage, the corn straw is crushed and screened through a double-layer screen to obtain coarse and fine straw fibers of different particle sizes, and the dust and impurities under the screen are removed. S2. Raw material pretreatment stage: The straw fiber, PLA and other auxiliary raw materials are dried, and the straw fiber is subjected to plasma surface activation treatment. S3, Mixing and Modification Stage: All raw materials are dry-mixed evenly in proportion, and then melt-blended and extruded through a twin-screw extruder to form a uniform melt composite. S4. In the granulation and 3D printing adaptation stage, the extruded strip is cooled and then cut into pellets. The pellets are then ultra-finely pulverized and screened to obtain printing raw materials that meet the particle size requirements. S5. Inspection and Packaging Stage: Mechanical properties and melt flow rate of printing materials are tested. After passing the test, they are vacuum packaged and stored in the warehouse after sealing test. The raw materials are formulated in the following proportions for a total of 100 parts: PLA 55 parts, straw coarse fiber 20 parts, straw fine fiber 15 parts, maleic anhydride grafted POE 4 parts, glycerin 3 parts, talc 2 parts, and antioxidant 1 part.

[0005] Preferably, the straw fiber grading stage uses a jaw crusher and a vibrating screen. The jaw crusher has a feed inlet of 150mm×250mm, a maximum feed particle size of 120mm, an adjustable discharge particle size of 5-20mm, a motor power of 5.5kW, and an inner liner made of 304 stainless steel. The vibrating screen is equipped with double-layer 304 stainless steel screens of 20 mesh and 120 mesh, an adjustable vibration frequency of 800-1800 times / min, an adjustable amplitude of 3-8mm, a motor power of 0.75kW, and a sealed dust cover. During processing, the corn straw is first dried for 24 hours, then fed into the jaw crusher with an output particle size of 8mm. After crushing, it is conveyed to the vibrating screen via a conveyor belt, with a vibration frequency of 1500 times / min and an amplitude of 5mm. After screening for 10 minutes, the upper layer of 20-40 mesh coarse fibers and the middle layer of 100-120 mesh fine fibers are collected separately. After screening, the screen is cleaned with compressed air.

[0006] Preferably, the raw material pretreatment stage uses a vacuum drying oven and a plasma treatment machine. The vacuum drying oven has an effective volume of 50L, a temperature control range of 5-200℃, a temperature control accuracy of ±1℃, and a vacuum degree of -0.095MPa. It is equipped with a detachable drying tray and a temperature sensor. The plasma treatment machine has a processing chamber volume of 10L, an adjustable power range of 0-500W, supports multiple protective gases, a gas flow control accuracy of ±0.1L / min, an adjustable processing time of 0-60min, and is equipped with a vacuum system and an exhaust purification device. During processing, the coarse and fine fibers of straw are evenly spread on the drying tray with a thickness of ≤2cm. The tray is placed in a vacuum drying oven at 80℃ and a vacuum degree of -0.09MPa for 4 hours. After cooling, it is transferred to a sealed container. The dried straw fibers are then placed in the plasma treatment chamber, evacuated to -0.08MPa, and purged with argon three times. The power is set to 300W and the treatment time is 5 minutes. The straw fibers are then removed under normal pressure. PLA, compatibilizer, talc, and antioxidant are placed in separate drying trays and vacuum dried at 60℃ for 2 hours. After cooling, they are transferred to the feed hopper of the mixer.

[0007] Preferably, the mixing and modification stage uses a twin-screw mixer and a co-rotating twin-screw extruder. The twin-screw mixer has an effective volume of 500L, a mixing chamber made of 304 stainless steel, an adjustable impeller speed of 30-80 r / min, a mixing uniformity variation coefficient ≤5%, and is equipped with a feed inlet, observation window, and discharge outlet. The co-rotating twin-screw extruder has a screw diameter of 36mm, a length-to-diameter ratio of 40:1, five temperature control zones, a temperature control range of 50-250℃, a temperature control accuracy of ±1℃, an adjustable screw speed of 50-300 r / min, and is equipped with a forced feeder and melt pressure transmitter. Sensors and screen changers; During processing, PLA, straw fiber, compatibilizer, talc powder, and antioxidant are added to the twin-screw mixer according to the formula and mixed at 60 r / min for 15 min. The mixture is then transported through pipelines to the twin-screw extruder forced feeder. The feeding speed is set to 50 kg / h, and the extruder temperatures are 160℃ in zone 1, 170℃ in zone 2, 180℃ in zone 3, 185℃ in zone 4, and 175℃ at the die head. The screw speed is 180 r / min. After the melt pressure is stabilized at 8-10 MPa, continuous extrusion is carried out. Samples are taken periodically to observe the state of the material strips and the temperature or feeding speed is adjusted accordingly.

[0008] Preferably, the granulation and 3D printing adaptation stage uses a pelletizer, an ultrafine pulverizer, and a vibrating screen. The pelletizer's cutting blade is made of high-speed steel with a blade hardness of HRC60 or higher. The pellet length is adjustable from 1 to 5 mm, and the pellet speed is adjustable from 0 to 50 m / min. It is equipped with a water cooling system and a material traction device. The ultrafine pulverizer's grinding chamber is made of zirconium corundum, with an adjustable grinding particle size of 10-150 μm. The motor power is 15 kW, and the vacuum degree during operation is ≥-0.09 MPa. It is equipped with a grading device and a dust recovery system. The vibrating screen is equipped with an 80-mesh 304 stainless steel screen. The screen has a mesh size of 180μm, a vibration frequency of 1500 times / min, an amplitude of 5mm, and is equipped with an oversize collection device. During processing, the extruded strip is cooled in a 3m cooling water tank at a water temperature of 25℃. It is then fed into a pelletizer by a traction machine with a pelletizing length of 3mm. After collecting the pellets, they are ventilated and dried. The dried pellets are then fed into an ultrafine pulverizer with a grinding particle size of 80μm. After pulverizing for 30 minutes, a sample is taken for testing. If the sample does not meet the standard, the pulverizing time is extended by 5-10 minutes. The pulverized material is then transferred to a vibrating screen for 10 minutes. The undersize particles are collected, and the oversize particles are returned to the ultrafine pulverizer for re-pulverization.

[0009] Preferably, the inspection and packaging stages utilize a universal testing machine, a melt flow rate meter, a fully automatic vacuum packaging machine, and a leak detector. During inspection, three samples are randomly selected from each batch to prepare standard tensile and bending specimens, which are then tested using the universal testing machine. A 5g sample is then tested using the melt flow rate meter at 190℃ / 2.16kg. During packaging, qualified granules are fed into the vacuum packaging machine via a screw conveyor, with each bag set to a weight of 25kg, a vacuum degree ≤-0.09MPa, a heat-sealing temperature of 160℃, and a heat-sealing time of 2s, completing the vacuuming, heat-sealing, and coding process. The packaged finished products are then tested using a leak detector, with a vacuum degree set to -0.05MPa and a testing time of 3s. Qualified products are stored in a warehouse with a temperature ≤25℃, relative humidity ≤65%, and stacking height ≤1.5m.

[0010] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves efficient resource utilization of natural biomass raw materials by grading straw fibers, avoiding the material performance shortcomings caused by single-size fibers. The process design incorporates raw material pretreatment and plasma activation, effectively improving the interfacial compatibility between straw fibers and PLA matrix. Combined with multi-component synergistic mixing and melt blending processes, the raw materials are fully integrated, significantly optimizing the internal structure of the material. The standardized production process and clear equipment operation specifications ensure the consistency of product quality across different batches, reduce fluctuations caused by human factors, and improve the repeatability and feasibility of the technical solution.

[0011] 2. The 3D printing material prepared by this invention combines the environmentally friendly properties of natural raw materials with the molding advantages of synthetic materials, meeting the needs of green production and sustainable development, while reducing dependence on traditional fossil-based raw materials; the product has good processing adaptability, can smoothly meet the feeding and molding requirements of 3D printing, and has strong storage stability after being sealed and packaged, and is not easily affected by environmental factors; in addition, the overall process is adapted to the needs of large-scale production, the operation process is clear and easy to understand, and no complex professional equipment and technology are required, which not only improves production efficiency, but also reduces production and application costs, and broadens the selection range and application scenarios of 3D printing materials. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0013] 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. 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.

[0014] This invention provides a method for preparing 3D printing materials by graded processing of straw fibers. The preparation method includes the following steps: S1. In the straw fiber grading stage, the corn straw is crushed and screened through a double-layer screen to obtain coarse and fine straw fibers of different particle sizes, and the dust and impurities under the screen are removed. S2. Raw material pretreatment stage: The straw fiber, PLA and other auxiliary raw materials are dried, and the straw fiber is subjected to plasma surface activation treatment. S3, Mixing and Modification Stage: All raw materials are dry-mixed evenly in proportion, and then melt-blended and extruded through a twin-screw extruder to form a uniform melt composite. S4. In the granulation and 3D printing adaptation stage, the extruded strip is cooled and then cut into pellets. The pellets are then ultra-finely pulverized and screened to obtain printing raw materials that meet the particle size requirements. S5. Inspection and Packaging Stage: Mechanical properties and melt flow rate of printing materials are tested. After passing the test, they are vacuum packaged and stored in the warehouse after sealing test. The raw materials are formulated in the following proportions for a total of 100 parts: PLA 55 parts, straw coarse fiber 20 parts, straw fine fiber 15 parts, maleic anhydride grafted POE 4 parts, glycerin 3 parts, talc 2 parts, and antioxidant 1 part. Specifically, the core logic is as follows: following the process of fiber grading, raw material pretreatment, mixing and modification, granulation and adaptation, inspection and packaging, through processes such as straw fiber grading and utilization, plasma activation, and melt blending, to achieve effective composite of natural fibers and synthetic resins, and finally obtain granular raw materials suitable for 3D printing. The core objectives of each step are as follows: The straw fiber grading stage obtains fibers of different particle sizes through grading and screening, which respectively undertake reinforcement and filling functions; the raw material pretreatment stage removes moisture from the raw materials, activates the fiber surface, and improves the compatibility and stability of the raw materials; the mixing and modification stage achieves uniform fusion of multiple components and improves interfacial bonding; the granulation and 3D printing adaptation stage pulverizes the composite to a particle size suitable for 3D printing, ensuring smooth feeding; and the inspection and packaging stage ensures product quality and storage stability through testing and sealed packaging. Raw material proportioning instructions: Total materials are quantified in 100 parts. PLA serves as the matrix material to provide the molding basis. Straw coarse and fine fibers work together to optimize the material structure. Maleic anhydride grafted with POE improves interfacial compatibility. Glycerin improves processing fluidity. Talc optimizes dimensional stability. Antioxidants prevent processing oxidation and degradation.

[0015] The straw fiber grading process uses a jaw crusher and a vibrating screen. The jaw crusher has a feed inlet of 150mm×250mm, a maximum feed particle size of 120mm, and an adjustable discharge particle size of 5-20mm. The motor power is 5.5kW, and the inner liner is made of 304 stainless steel. The vibrating screen is equipped with double-layer 304 stainless steel screens of 20 mesh and 120 mesh, with an adjustable vibration frequency of 800-1800 times / min and an adjustable amplitude of 3-8mm. The motor power is 0.75kW, and it has a sealed dust cover. During processing, the corn straw is first dried for 24 hours, then fed into the jaw crusher with an output particle size of 8mm. After crushing, it is conveyed to the vibrating screen with a vibration frequency of 1500 times / min and an amplitude of 5mm. After screening for 10 minutes, the upper layer of 20-40 mesh coarse fibers and the middle layer of 100-120 mesh fine fibers are collected separately. After screening, the screen is cleaned with compressed air. Specifically, the material requirements are as follows: Corn stalks must be mature, free from mold, insect infestation, and obvious impurities, and the initial moisture content after 24 hours of drying should be ≤15%; the coarse fiber of the stalks must meet the following requirements: 20-40 mesh, cellulose content ≥40%, lignin content ≤28%, and moisture content ≤8%; the fine fiber of the stalks must meet the following requirements: 100-120 mesh, cellulose content ≥45%, lignin content ≤25%, and moisture content ≤8%. Equipment supplement: Jaw crusher model PE-150×250; Vibrating screen model ZS-515; Equipment requirements: PE-150×250 jaw crusher: feed opening size 150mm×250mm, maximum feed particle size 120mm, discharge particle size adjustable from 5-20mm, motor power 5.5kW, inner liner made of 304 stainless steel, wear-resistant and corrosion-resistant, preventing metal impurities from contaminating raw materials; ZS-515 vibrating screen: equipped with 20-mesh and 120-mesh double-layer 304 stainless steel screens, vibration frequency adjustable from 800-1800 times / min, amplitude adjustable from 3-8mm, motor power 0.75kW, sealed dust cover to prevent dust from flying and secondary contamination of raw materials; Equipment Functions: The jaw crusher crushes lumpy corn stalks into uniform 8mm coarse material through compression crushing, while removing hard impurities such as stones and metal hidden in the stalks to prevent scratching subsequent processing equipment; the ZS-515 vibrating screen achieves fiber grading through high-frequency vibration. A 20-mesh screen separates 20-40 mesh coarse fibers (upper layer), and a 120-mesh screen separates 100-120 mesh fine fibers (middle layer). The dust under the screen is directly removed due to its low fiber content and high impurity content, ensuring uniform particle size of both types of fibers and laying the foundation for subsequent compounding processes; Pre-treatment and operation details: Sun-drying corn stalks for 24 hours is to initially reduce the moisture content and prevent fiber sticking during crushing; conveying them by conveyor belt after crushing can reduce human contact and contamination; after screening, the screen is cleaned with compressed air to prevent fiber residue from affecting the next use.

[0016] The raw material pretreatment stage utilizes a vacuum drying oven and a plasma treatment machine. The vacuum drying oven has an effective volume of 50L, a temperature control range of 5-200℃, a temperature control accuracy of ±1℃, and a vacuum degree up to -0.095MPa. It is equipped with detachable drying trays and temperature sensors. The plasma treatment machine has a 10L processing chamber, an adjustable power range of 0-500W, supports multiple protective gases, a gas flow control accuracy of ±0.1L / min, and an adjustable processing time of 0-60min. It also includes a vacuum system and an exhaust purification device. The coarse and fine fibers of straw are evenly spread on the drying tray, with a thickness of ≤2cm. The tray is placed in a vacuum drying oven at 80℃ and a vacuum degree of -0.09MPa for 4 hours. After cooling, it is transferred to a sealed container. The dried straw fibers are then placed in a plasma treatment chamber, evacuated to -0.08MPa, and purged with argon three times. The power is set to 300W and the treatment time is 5 minutes. The straw fibers are then removed under normal pressure. PLA, compatibilizer, talc, and antioxidant are placed in separate drying trays and vacuum dried at 60℃ for 2 hours. After cooling, they are transferred to the feed hopper of the mixer. Specifically, the material requirements are as follows: PLA type 4032D, melting point 155-165℃, melt flow rate 10-15g / 10min, purity ≥99%, conforming to GB / T29284-2012 standard; compatibilizer is maleic anhydride-grafted POE, grafting rate ≥1.2%, melting point 70-80℃, thermal weight loss at 200℃ ≤3%; talc particle size D 50 ≤5μm, whiteness ≥93%, surface activated; antioxidant is antioxidant 1010, purity ≥98%, melting point 110-115℃, conforming to GB / T19266-2003 standard; glycerol purity ≥99.5%, moisture ≤0.2%, color (APHA) ≤20, conforming to GB29950-2013 standard; Equipment supplement: Vacuum drying oven, model DZF-6050; Plasma treatment machine, model PT-100; Equipment requirements: The DZF-6050 vacuum drying oven has an effective volume of 50L, a temperature control range of 5-200℃, a temperature control accuracy of ±1℃, and a vacuum degree up to -0.095MPa. It is equipped with detachable drying trays and temperature sensors, supports continuous operation, and ensures uniform drying. The PT-100 plasma processor has a processing chamber volume of 10L, an adjustable power range of 0-500W, supports multiple protective gases such as argon and nitrogen, has a gas flow control accuracy of ±0.1L / min, an adjustable processing time of 0-60min, and is equipped with a vacuum system and exhaust purification device to avoid waste gas pollution. Equipment Functions: The DZF-6050 vacuum drying oven removes moisture from raw materials in a low-temperature vacuum environment. Straw fibers are dried at 80℃ and a vacuum of -0.09MPa for 4 hours, reducing the moisture content to below 8%, thus preventing moisture vaporization and bubble formation during subsequent melting and processing. PLA, compatibilizers, and other raw materials are vacuum dried at 60℃ for 2 hours, reducing the moisture content to below 0.5%, preventing hydrolysis and degradation during processing. The PT-100 plasma treatment machine introduces argon gas (flow rate 3L / min) and treats straw fibers at 300W power for 5 minutes. Through the physical bombardment and chemical activation of plasma, active groups such as hydroxyl and carboxyl groups are introduced onto the fiber surface, reducing the surface roughness of the fiber, improving the interfacial bonding force with the PLA matrix, and solving the problem of poor compatibility between natural fibers and synthetic resins. Operational details: The thickness of the straw fiber layer is ≤2cm to ensure uniform drying and avoid localized excessive moisture content due to accumulation; PLA and auxiliary materials are dried in separate drying trays to prevent cross-contamination between different materials; after drying, they are transferred to a sealed container to avoid moisture absorption; argon gas is purged three times before plasma treatment to completely remove air from the treatment chamber and prevent oxygen from affecting the activation effect.

[0017] The mixing and modification stages utilize a twin-screw mixer and a co-rotating twin-screw extruder. The twin-screw mixer has an effective volume of 500L, a mixing chamber made of 304 stainless steel, adjustable impeller speed of 30-80 r / min, and a mixing uniformity variation coefficient ≤5%. It is equipped with a feed inlet, observation window, and discharge outlet. The co-rotating twin-screw extruder has a screw diameter of 36mm, a length-to-diameter ratio of 40:1, five temperature control zones, a temperature control range of 50-250℃, a temperature control accuracy of ±1℃, and an adjustable screw speed of 50-300 r / min. It is also equipped with a forced feeder, melt pressure sensor, and... Screen changer; During processing, PLA, straw fiber, compatibilizer, talc powder, and antioxidant are added to the twin-screw mixer according to the ratio and mixed at 60 r / min for 15 min. The mixture is then transported through pipeline to the twin-screw extruder forced feeder. The feeding speed is set to 50 kg / h, and the extruder temperature is 160℃ in zone 1, 170℃ in zone 2, 180℃ in zone 3, 185℃ in zone 4, and 175℃ at the die head. The screw speed is 180 r / min. After the melt pressure is stabilized at 8-10 MPa, continuous extrusion is carried out. Samples are taken periodically to observe the state of the material strips and the temperature or feeding speed is adjusted accordingly. Specifically, the equipment includes: a twin-screw mixer (model WHS-500) and a co-rotating twin-screw extruder (model SHJ-36). Equipment requirements: WHS-500 twin-screw mixer with an effective volume of 500L, a mixing chamber made of 304 stainless steel, adjustable twin-screw blade speed of 30-80r / min, mixing uniformity variation coefficient ≤5%, equipped with a feed inlet, observation window and discharge outlet, supporting continuous feeding and batch mixing; SHJ-36 co-rotating twin-screw extruder with a screw diameter of 36mm, length-to-diameter ratio of 40:1, five temperature control zones from zone one to the die head, temperature control range of 50-250℃, temperature control accuracy ±1℃, adjustable screw speed of 50-300r / min, equipped with a forced feeder, melt pressure sensor and screen changer, the screen changer can filter impurities in the melt; Equipment Functions: The WHS-500 twin-screw mixer uses the shearing and convection action of inner and outer propeller blades to thoroughly dry-mix multiple components such as PLA, straw fiber, compatibilizer, talc, and antioxidants, achieving uniform dispersion within 15 minutes and avoiding excessively high or low concentrations of components in certain areas. The SHJ-36 co-rotating twin-screw extruder transforms dry-mixed raw materials into a uniform molten composite through forced feeding, shear melting, and mixing homogenization processes. The high shearing action of the screws breaks up straw fiber agglomerates, promotes the diffusion of compatibilizers at the fiber-PLA interface, forms a stable interfacial layer, and improves the mechanical properties of the material. The segmented temperature control design avoids localized overheating and degradation of raw materials, ensuring processing stability. Operating details: The extruder's five-stage temperature control is set according to the logic of preheating in zone one, gradual heating from zone two to four, and heat preservation at the die head, adapting to the melting characteristics of PLA; the forced feeder is set to a feeding speed of 50 kg / h to ensure uniform feeding; the melt pressure is stabilized at 8-10 MPa to ensure uniform density and smooth surface of the extruded strip; the strip condition is sampled regularly, and if problems such as surface roughness, bubbles, or breakage occur, the temperature or feeding speed needs to be adjusted in time to ensure the quality of the molten composite.

[0018] In the granulation and 3D printing adaptation stage, a pelletizer, an ultrafine pulverizer, and a vibrating screen are used. The pelletizer's cutting blade is made of high-speed steel with a blade hardness of HRC60 or higher. The pellet length is adjustable from 1 to 5 mm, and the pellet speed is adjustable from 0 to 50 m / min. It is equipped with a water cooling system and a material traction device. The ultrafine pulverizer's grinding chamber is made of zirconium corundum, and the grinding particle size is adjustable from 10 to 150 μm. The motor power is 15 kW, and the vacuum degree during operation is ≥-0.09 MPa. It is equipped with a grading device and a dust recovery system. The vibrating screen is equipped with an 80-mesh 304 stainless steel screen. The extruded material has a diameter of 180μm, a vibration frequency of 1500 times / min, an amplitude of 5mm, and is equipped with a screen collection device. During processing, the extruded strip is cooled in a 3m cooling water tank at a water temperature of 25℃. It is then fed into a pelletizer by a traction machine with a set pellet length of 3mm. After collecting the pellets, they are ventilated and dried. The dried pellets are then fed into an ultrafine pulverizer with a set grinding particle size of 80μm. After pulverizing for 30 minutes, a sample is taken for testing. If the sample does not meet the standard, the pulverizing time is extended by 5-10 minutes. After pulverizing, the material is transferred to a vibrating screen for 10 minutes. The undersized particles are collected, and the oversized particles are returned to the ultrafine pulverizer for re-pulverization. Specifically, the equipment supplements are as follows: pelletizer model SLJ-800; ultrafine pulverizer model WFM-100; vibrating screen model ZS-515; Equipment Requirements: The SLJ-800 pelletizer uses high-speed steel blades with a hardness of HRC60 or higher. The pellet length is adjustable from 1-5mm, and the pellet speed is adjustable from 0-50m / min. It is equipped with a water cooling system and a material traction device to ensure uniform pelleting. The WFM-100 ultrafine pulverizer uses zirconia corundum as the grinding chamber material, which is wear-resistant and corrosion-resistant. The grinding particle size is adjustable from 10-150μm. The motor power is 15kW, and the vacuum degree during operation is ≥-0.09MPa. It is equipped with a grading device and a dust recovery system to prevent raw material oxidation and dust contamination. The ZS-515 vibrating screen is equipped with an 80-mesh 304 stainless steel screen (screen aperture 180μm), a vibration frequency of 1500 times / min, an amplitude of 5mm, and an oversize collection device for easy recycling of unqualified particles. Equipment Functions: The SLJ-800 pelletizer cuts cooled continuous feed strips into 3mm×3mm cylindrical particles after water cooling (water temperature 25℃), facilitating storage, transportation, and subsequent pulverization; the WFM-100 ultrafine pulverizer pulverizes particles to 80-100μm (D) through the impact and shearing action of a high-speed rotating grinding disc and grinding rod. 50 This particle size is suitable for the feeding requirements of 3D printing (fused deposition modeling, FDM), and can pass smoothly through the printing nozzle without clogging; the ZS-515 vibrating screen is used to screen the crushed particles, remove excessively large particles with a particle size >180μm, ensure that the particle size of the printing material is uniform, and improve the smoothness of the printing process and the surface quality of the molded parts. Operating details: The cooling water tank is 3m long and the water temperature is 25℃, which can quickly cool the material strips to room temperature and prevent the strips from sticking together; the particles need to be air-dried until the surface moisture content is ≤0.5% to prevent clumping during crushing; after crushing, samples are taken to test the particle size. If D 50 If the particle size is less than 80μm, the grinding time needs to be extended by 5-10 minutes; oversized particles on the sieve should be returned to the ultrafine pulverizer for re-grinding, which can improve the utilization rate of raw materials and reduce waste.

[0019] During the inspection and packaging stages, a universal testing machine, melt flow rate meter, fully automatic vacuum packaging machine, and leak detector are used. For inspection, three samples are randomly selected from each batch to prepare standard tensile and bending specimens, which are then tested using the universal testing machine. A 5g sample is also tested using the melt flow rate meter at 190℃ / 2.16kg. During packaging, qualified granules are fed into the vacuum packaging machine via a screw conveyor. Each bag is set to weigh 25kg, with a vacuum degree ≤-0.09MPa, a heat-sealing temperature of 160℃, and a heat-sealing time of 2s, completing the vacuuming, heat-sealing, and coding process. The packaged finished products are tested using a leak detector with a vacuum degree set to -0.05MPa and a testing time of 3s. Qualified products are stored in a warehouse with a temperature ≤25℃, relative humidity ≤65%, and stacking height ≤1.5m. Specifically, the equipment supplements are as follows: Universal testing machine model CMT-5105; Melt flow rate meter model XNR-400; Fully automatic vacuum packaging machine model DZ-600; Leaking bag detector model LDJ-50; Equipment Requirements: CMT-5105 universal testing machine with a testing force range of 0-100kN and a testing accuracy of ±0.5%, supporting various mechanical tests such as tension, bending, and compression, equipped with a computer data acquisition and analysis system; XNR-400 melt flow rate meter with a temperature control range of 50-400℃, a temperature control accuracy of ±0.5℃, a loading weight range of 0.325-21.6kg, a timing accuracy of ±0.1s, conforming to GB / T3682-2000 standard; DZ-600 fully automatic... The vacuum packaging machine has a vacuum chamber volume of 600×400×180mm, a vacuum degree of ≤-0.09MPa, an adjustable heat sealing temperature of 100-200℃, and an adjustable heat sealing time of 0.5-5s. It is equipped with a quantitative feeding device and a date coding device, and the packaging speed is 60 bags / h. The LDJ-50 leak detector uses the vacuum negative pressure method, with an adjustable vacuum degree range of -0.02~-0.08MPa and an adjustable detection time of 1-30s. It is equipped with an audible and visual alarm device and can automatically reject unqualified packaging. Equipment Functions: The CMT-5105 universal testing machine is used to test the tensile strength and flexural strength of materials, verifying whether the mechanical properties of the materials meet the usage requirements; the XNR-400 melt flow rate meter is used to detect the melt flow rate of materials, ensuring that the materials have good printing fluidity; the DZ-600 fully automatic vacuum packaging machine uses vacuuming and heat sealing processes to package qualified raw materials in 25kg / bags, isolating them from air and moisture to prevent them from absorbing moisture and deteriorating; the date coding device prints the production batch number and shelf life for easy product traceability; the LDJ-50 leak detector is used to test the sealing performance of the packaging, preventing the raw materials from absorbing moisture due to packaging damage, and ensuring the stability of product storage. Inspection and Operation Details: During inspection, three samples are randomly selected from each batch to prepare standard tensile test specimens (GB / T1040.2-2006) and bending test specimens (GB / T9341-2008). The qualified threshold for tensile strength is ≥18MPa, and the qualified threshold for bending strength is ≥25MPa. Take 5g of sample and test it with a melt flow rate tester at 190℃ / 2.16kg. The qualified threshold is 8-12g / 10min. During packaging, the screw conveyor can avoid secondary contamination of raw materials, and the quantitative feeding device ensures that the weight error of each bag is ≤±0.2kg. During storage, the warehouse temperature is ≤25℃, the relative humidity is ≤65%, and the stacking height is ≤1.5m. Direct sunlight and compression should be avoided to prevent particle agglomeration and degradation.

[0020] The method of use and working principle of this invention are as follows: Usage: Select corn stalks, PLA, and other auxiliary materials. First, dry the corn stalks and then crush them. Use a double-layer screen to separate the coarse and fine fibers of different particle sizes, removing dust and impurities. Then, dry the straw fibers, PLA, and other auxiliary materials separately. The dried straw fibers are then subjected to plasma surface activation treatment. Add all the raw materials to a mixing device in proportion and dry mix evenly. Then, use a twin-screw extruder for melt blending and extrusion to form a composite. After cooling the extruded strip, cut it into pellets, and then perform ultra-fine grinding on the pellets. After sieving, obtain the printing material that meets the requirements. Finally, test the mechanical properties and melt flow rate of the printing material. After passing the test, vacuum package it and store it in the warehouse after confirming that the sealing is correct.

[0021] Working Principle: Based on the core logic of graded utilization of straw fiber and multi-component synergistic compounding, straw fibers of different particle sizes are obtained through grading and sieving, each serving as reinforcement and filler, thus optimizing the internal structure of the material. In the raw material pretreatment stage, drying removes moisture to avoid defects during processing, while plasma activation introduces active groups onto the surface of the straw fibers, enhancing their interfacial bonding with the PLA matrix. In the mixing and modification stage, dry mixing and melt blending achieve uniform dispersion and deep integration of the raw materials. Compatibilizers further improve interfacial compatibility, while plasticizers and fillers optimize processing flowability and dimensional stability, respectively. In the granulation and sieving stage, the composite is processed to a particle size suitable for 3D printing, ensuring smooth feeding. Finally, inspection and sealed packaging ensure product quality meets standards and storage stability. The entire process forms a complete closed loop of raw material optimization, composite modification, molding adaptation, and quality assurance, achieving an effective combination of natural fibers and synthetic resins.

[0022] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing 3D printing materials by graded processing of straw fibers, characterized in that, The preparation method includes the following steps: S1. In the straw fiber grading stage, the corn straw is crushed and screened through a double-layer screen to obtain coarse and fine straw fibers of different particle sizes, and the dust and impurities under the screen are removed. S2. Raw material pretreatment stage: The straw fiber, PLA and other auxiliary raw materials are dried, and the straw fiber is subjected to plasma surface activation treatment. S3, Mixing and Modification Stage: All raw materials are dry-mixed evenly in proportion, and then melt-blended and extruded through a twin-screw extruder to form a uniform melt composite. S4. In the granulation and 3D printing adaptation stage, the extruded strip is cooled and then cut into pellets. The pellets are then ultra-finely pulverized and screened to obtain printing raw materials that meet the particle size requirements. S5. Inspection and Packaging Stage: Mechanical properties and melt flow rate of printing materials are tested. After passing the test, they are vacuum packaged and stored in the warehouse after sealing test. The raw materials are formulated in the following proportions for a total of 100 parts: PLA 55 parts, straw coarse fiber 20 parts, straw fine fiber 15 parts, maleic anhydride grafted POE 4 parts, glycerin 3 parts, talc 2 parts, and antioxidant 1 part.

2. The method for preparing 3D printing material by graded treatment of straw fiber according to claim 1, characterized in that, The straw fiber grading stage uses a jaw crusher and a vibrating screen. The jaw crusher has a feed inlet of 150mm×250mm, a maximum feed particle size of 120mm, and an adjustable discharge particle size of 5-20mm. The motor power is 5.5kW, and the inner liner is made of 304 stainless steel. The vibrating screen is equipped with double-layer 304 stainless steel screens of 20 mesh and 120 mesh, with an adjustable vibration frequency of 800-1800 times / min and an adjustable amplitude of 3-8mm. The motor power is 0.75kW, and it has a sealed dust cover. During processing, the corn straw is first dried for 24 hours, then fed into the jaw crusher with an output particle size of 8mm. After crushing, it is conveyed to the vibrating screen with a vibration frequency of 1500 times / min and an amplitude of 5mm. After screening for 10 minutes, the upper layer of 20-40 mesh coarse fibers and the middle layer of 100-120 mesh fine fibers are collected separately. After screening, the screen is cleaned with compressed air.

3. The method for preparing 3D printing material by graded treatment of straw fiber according to claim 1, characterized in that, The raw material pretreatment stage utilizes a vacuum drying oven and a plasma treatment machine. The vacuum drying oven has an effective volume of 50L, a temperature control range of 5-200℃, a temperature control accuracy of ±1℃, and a vacuum degree up to -0.095MPa. It is equipped with detachable drying trays and temperature sensors. The plasma treatment machine has a processing chamber volume of 10L, an adjustable power range of 0-500W, supports multiple protective gases, a gas flow control accuracy of ±0.1L / min, and an adjustable processing time of 0-60min. It is equipped with a vacuum system and an exhaust purification device. During processing, the coarse and fine fibers of straw are evenly spread on the drying tray, with a thickness of ≤2cm. The tray is placed in a vacuum drying oven at 80℃ and a vacuum degree of -0.09MPa for 4 hours. After cooling, it is transferred to a sealed container. The dried straw fibers are then placed in a plasma treatment chamber, evacuated to -0.08MPa, and purged with argon three times. The power is set to 300W and the treatment time is 5 minutes. The straw fibers are then removed under normal pressure. PLA, compatibilizer, talc, and antioxidant are placed in separate drying trays and vacuum dried at 60℃ for 2 hours. After cooling, they are transferred to the feed hopper of the mixer.

4. The method for preparing 3D printing material by graded treatment of straw fiber according to claim 1, characterized in that, The mixing and modification stage utilizes a twin-screw mixer and a co-rotating twin-screw extruder. The twin-screw mixer has an effective volume of 500L, a mixing chamber made of 304 stainless steel, adjustable impeller speed of 30-80 r / min, and a mixing uniformity variation coefficient ≤5%. It is equipped with a feed inlet, observation window, and discharge outlet. The co-rotating twin-screw extruder has a screw diameter of 36mm, a length-to-diameter ratio of 40:1, five temperature control zones, a temperature control range of 50-250℃, a temperature control accuracy of ±1℃, and an adjustable screw speed of 50-300 r / min. It is also equipped with a forced feeder and a melt pressure sensor. With screen changer; during processing, PLA, straw fiber, compatibilizer, talc powder, and antioxidant are added to the twin-screw mixer according to the ratio and mixed at 60 r / min for 15 min. The mixture is then transported through pipeline to the twin-screw extruder forced feeder. The feeding speed is set to 50 kg / h, and the extruder temperature is set to 160℃ in zone 1, 170℃ in zone 2, 180℃ in zone 3, 185℃ in zone 4, and 175℃ at the die head. The screw speed is 180 r / min. After the melt pressure is stabilized at 8-10 MPa, continuous extrusion is performed. Samples are taken periodically to observe the state of the material strips and the temperature or feeding speed is adjusted accordingly.

5. The method for preparing 3D printing material by graded treatment of straw fiber according to claim 1, characterized in that, The granulation and 3D printing adaptation stage utilizes a pelletizer, an ultrafine pulverizer, and a vibrating screen. The pelletizer's blades are made of high-speed steel with a hardness of HRC60 or higher. The pellet length is adjustable from 1-5mm, and the pelletizing speed is adjustable from 0-50m / min. It is equipped with a water cooling system and a material traction device. The ultrafine pulverizer's grinding chamber is made of zirconium corundum, with an adjustable grinding particle size of 10-150μm. It has a 15kW motor, operates with a vacuum degree ≥-0.09MPa, and includes a grading device and a dust recovery system. The vibrating screen is equipped with an 80-mesh 304 stainless steel screen. The pore size is 180μm, the vibration frequency is 1500 times / min, the amplitude is 5mm, and it is equipped with a screen collection device. During processing, the extruded strip is cooled in a 3m cooling water tank at a water temperature of 25℃. It is then fed into a pelletizer by a traction machine with a set pellet length of 3mm. After collecting the pellets, they are ventilated and dried. The dried pellets are then fed into an ultrafine pulverizer with a set grinding particle size of 80μm. After pulverizing for 30 minutes, a sample is taken for testing. If the sample does not meet the standard, the pulverizing time is extended by 5-10 minutes. After pulverizing, the material is transferred to a vibrating screen for screening for 10 minutes. The undersized particles are collected, and the oversized particles are returned to the ultrafine pulverizer for re-pulverization.

6. The method for preparing 3D printing material by graded treatment of straw fiber according to claim 1, characterized in that, The inspection and packaging stages utilize a universal testing machine, a melt flow rate meter, a fully automatic vacuum packaging machine, and a leak detector. During inspection, three samples are randomly selected from each batch to prepare standard tensile and bending specimens, which are then tested using the universal testing machine. A 5g sample is then tested using the melt flow rate meter at 190℃ / 2.16kg. During packaging, qualified granules are fed into the vacuum packaging machine via a screw conveyor. Each bag is set to weigh 25kg, with a vacuum degree ≤-0.09MPa, a heat-sealing temperature of 160℃, and a heat-sealing time of 2s, completing the vacuuming, heat-sealing, and coding process. The packaged finished products are then tested using a leak detector, with a vacuum degree set to -0.05MPa and a testing time of 3s. Qualified products are stored in a warehouse with a temperature ≤25℃, relative humidity ≤65%, and stacking height ≤1.5m.

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