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CN-121989452-A - 3D printing method for improving mixing uniformity of five-mixing technology

CN121989452ACN 121989452 ACN121989452 ACN 121989452ACN-121989452-A

Abstract

The invention provides a 3D printing method for improving mixing uniformity of a five-mixing technology, which comprises the following steps of classifying and grouping various molten printing materials according to characteristics, dividing equipment temperature control areas according to material classification results, building a segmented gradient temperature control system, performing independent dynamic feeding regulation and control on each feeding mechanism according to material characteristics and mixing requirements, synchronously feeding materials into a mixing cavity according to a design proportion by matching with flow closed loop feedback, arranging auxiliary equipment at corresponding positions of the mixing cavity, regulating and controlling operation parameters of a stirring structure and residence time in the cavity of the material, pre-printing and detecting mixing uniformity by using the adapted materials, specifically adjusting and then curing an optimal technological parameter combination, and achieving good mixing uniformity and forming effect.

Inventors

  • YANG XIANGDONG
  • LU JIFU
  • ZHAI QIAN
  • ZHANG XIAOMIN
  • JIAN DAN
  • LV CHENG

Assignees

  • 广州华立学院

Dates

Publication Date
20260508
Application Date
20260228

Claims (10)

  1. 1. The 3D printing method for improving the mixing uniformity of the five-mixing technology is realized by 3D printing multi-mixing equipment, and the 3D printing multi-mixing equipment comprises a multi-independent feeding mechanism, a mixing cavity, a stirring structure and a printing nozzle and is characterized by comprising the following steps: S1, classifying and grouping various molten printing materials according to characteristics, wherein the characteristics comprise melting point, melt viscosity and components; s2, dividing a plurality of independent feeding mechanisms and a temperature control area of a mixing cavity according to melting point and melt viscosity, wherein the mixing cavity comprises a premixing section, an intermediate homogenizing section and a transition section; s3, determining initial feeding speeds of a plurality of independent feeding mechanisms according to the melt viscosity and the mixing proportion, detecting whether the actual proportion deviates from the designed proportion in real time, and dynamically adjusting the feeding speed of the corresponding feeding mechanism if the actual proportion deviates from the designed proportion; s4, arranging an ultrasonic device on the outer side wall of the mixing cavity, and dynamically adjusting ultrasonic power according to the printing speed and the material mixing state; s5, mixing the stirring structure by adopting different speeds in a premixing section, an intermediate homogenizing section and a transition section of the mixing cavity, and adjusting the feeding speed and the stirring speed according to the characteristics of different melting points and different melt viscosities in a grouping way; S6, identifying the defect condition of the printed product on the printing nozzle through an image identification algorithm, and correcting the power of the ultrasonic device, the stay time of the homogenization section in the middle of the mixing cavity, the stirring speed and the feeding speed according to the defect condition of the printed product.
  2. 2. The method for 3D printing for improving the mixing uniformity of the five-mixing technology according to claim 1, wherein the step S1 comprises the steps of S11, screening and classifying a plurality of molten printing materials, namely detecting the plurality of molten printing materials, recording the melting point T, the melting viscosity eta, the thermal expansion coefficient alpha and the components of each material, and classifying the plurality of materials into three groups, namely a high-melting-point high-viscosity group, a medium-melting-point medium-viscosity group and a low-melting-point low-viscosity group.
  3. 3. The 3D printing method for improving the mixing uniformity of the five-mixing technology is characterized by further comprising the following steps of S12, mixing five materials according to a preset proportion, preserving heat at a preset melting temperature, observing whether the appearance of the mixed materials is uniform, layering and discoloring or not, detecting the interface shear strength of the mixed materials, adding a compatilizer if the interface shear strength is smaller than a preset shear strength value or layering and discoloring occur, controlling the proportion of the compatilizer and the melting point of the compatilizer, and premixing a high-viscosity material and a low-viscosity material according to a preset mass ratio by adopting a premixing master batch treatment if the difference of the viscosity of the materials exceeds a preset standard, and then using the high-viscosity material and the low-viscosity material as the materials corresponding to the grading grouping; s13, drying pretreatment, namely respectively placing materials meeting compatibility regulation and control grading grouping into a drying oven, and performing high-temperature drying treatment.
  4. 4. The 3D printing method for improving the mixing uniformity of the five-mixing technology according to claim 1, wherein the step S2 comprises the steps of S21, dividing a temperature control area of the 3D printing multi-mixing equipment into a feeding channel temperature control area, a mixing cavity temperature control area and a nozzle temperature control area, and dividing the mixing cavity temperature control area into an inlet premixing section, an intermediate homogenization section and an outlet transition section; S22, setting gradient temperature, namely setting the temperature gradient of each temperature control area based on the classified materials, and following the gradient principle of 'the temperature of a feeding channel < the temperature of a premixing section at an inlet of a mixing cavity < the temperature of a homogenization section at the middle of the mixing cavity < the temperature of an outlet transition section of the mixing cavity < the temperature of a nozzle', S23, temperature control precision control, namely acquiring temperature data of each region once every preset time by adopting real-time temperature measurement feedback, and adjusting heating power if the temperature deviates from a set value, so as to realize temperature closed-loop control.
  5. 5. The 3D printing method for improving the mixing uniformity of the five-mixing technology is characterized in that the step S22 further comprises the steps of setting the temperature of a feeding channel temperature control area corresponding to the feeding channel of the grading grouping material, wherein the temperature T 1 =T High average -15 ℃ of a high-melting-point high-viscosity group feeding channel is set, the temperature T 2 =T Average in -10 ℃ of a medium-melting-point medium-viscosity group feeding channel is set, the temperature T 3 =T Low average -5℃,T High average of a low-melting-point low-viscosity group feeding channel is the average melting point of the high-melting-point high-viscosity group material, the average melting point T Average in of the medium-melting-point medium-viscosity group material is set, and the average melting point T Low average of the low-melting-point low-viscosity group material is set; The temperature T 4 = T Are all +5 ℃ of the premixing section at the inlet of the mixing cavity, the temperature T 5 =T Are all +10 ℃ of the homogenization section in the middle of the mixing cavity, and the temperature T 6 =T Are all +8℃,T Are all of the transition section at the outlet of the mixing cavity are the average melting points of various molten printing materials; Nozzle temperature T 7 =T Are all +12 ℃.
  6. 6. The 3D printing method for improving the mixing uniformity of the five-mixing technology according to claim 1, wherein the step S3 is characterized by comprising the following steps of S31, initial setting of feeding speed, namely, setting initial feeding speeds of a plurality of feeding mechanisms according to the melt viscosity and mixing proportion of a plurality of materials, wherein the feeding speed V1 of a high-melting-point high-viscosity group is smaller than the feeding speed V2 of a medium-melting-point medium-viscosity group and smaller than the feeding speed V3 of a low-melting-point low-viscosity group; s32, material flow data of a plurality of feeding mechanisms are collected in real time, deviation between actual feeding proportion and design proportion is calculated, and if the deviation is greater than a preset value, the feeding speed of the corresponding feeding mechanism is dynamically adjusted; S33, controlling feeding synchronism, namely adjusting starting and stopping time sequences of a plurality of feeding mechanisms, ensuring that a plurality of materials enter the inlet premixing section of the mixing cavity simultaneously, controlling fluctuation of feeding speed to be less than or equal to a preset fluctuation value, avoiding flow field disorder caused by sudden change of the feeding speed, and further improving mixing uniformity.
  7. 7. The 3D printing method for improving the mixing uniformity of the five-mixing technology according to claim 1, wherein the step S4 comprises the steps of S41, setting ultrasonic parameters, namely setting the frequency and the power density of an ultrasonic device, and adopting an intermittent starting mode for ultrasonic vibration; S42, dynamically adjusting ultrasonic power according to the printing speed and the material mixing state, wherein the ultrasonic power is adjusted to be the first ultrasonic power when the printing speed is a first preset value, the ultrasonic power is adjusted to be the second ultrasonic power when the printing speed is a second preset value, and the ultrasonic power is reduced to be processed on the basis of the first preset value or the second preset value when the low-viscosity materials are classified and grouped.
  8. 8. The 3D printing method for improving the mixing uniformity of the five-mixing technology according to claim 1, wherein the step S5 comprises the steps of S51 setting the stirring structure speed in a mixing cavity in a sectional manner, wherein the stirring structure speed in a premixing section is smaller than the stirring structure speed in an intermediate homogenizing section and smaller than the stirring structure speed in a discharging section; S52, regulating and controlling the feeding speed, namely controlling the total residence time of the mixed materials in the mixing cavity to be a preset value by regulating the feeding speed and the speed of the stirring structure, and simultaneously prolonging the first preset time value of the total residence time when the materials with high melt viscosity are combined and shortening the second preset time value of the total residence time when the materials with low melt viscosity are combined.
  9. 9. The 3D printing method for improving the mixing uniformity of the five-mixing technology according to claim 1, wherein the step S6 is characterized by comprising the following steps of S61, setting monitoring parameters, namely installing a visual detection device below a nozzle, shooting the defect condition of a printed product in real time, wherein the defect condition of the printed product comprises color uniformity, surface evenness, and identification of stripes and color blocks; S62, defect identification and feedback, namely analyzing an image of a printed product of the visual detection device in real time by utilizing an image identification algorithm, and identifying and marking the type and severity of the defect if the streak and color block defect are identified; S63, parameter dynamic correction, namely, according to the fed-back abnormal signals, pertinently adjusting the power of a corresponding ultrasonic device, the residence time of a homogenization section in the middle of a mixing cavity, the stirring speed and the feeding speed: If the streak defect occurs, the ultrasonic power is increased by 5-10%, the stay time of the material in the homogenization section in the middle of the mixing cavity is prolonged by 0.2-0.3 seconds, or the stirring rotating speed is increased by 20-30rpm; If the color lump defect occurs, adjusting the feeding speed of a corresponding feeding mechanism, correcting the feeding proportion, ensuring that the deviation of the design proportion is less than or equal to 2 percent, and simultaneously prolonging the retention time of the material in an inlet premixing section by 0.1 to 0.2 seconds; If the pressure of the mixing cavity is too high, the feeding speed is reduced by 0.1-0.2mm/s, or the temperature of a homogenization section in the middle of the mixing cavity is increased by 3-5 ℃; If the pressure of the mixing cavity is too low, the feeding speed is increased by 0.1-0.2mm/s, or the temperature of a homogenization section in the middle of the mixing cavity is reduced by 2-3 ℃; If the temperature deviates from the set value, the heating power of the corresponding temperature control area is regulated, and the temperature fluctuation is ensured to be less than or equal to +/-1 ℃.
  10. 10. The 3D printing method for improving the mixing uniformity of the five-mixing technology according to claim 1, further comprising the step of S7 performing calibration optimization on a printed product, wherein the step of S7 comprises the following steps of S71 detecting the mixing uniformity, namely cooling the printed product to room temperature after the printed product is finished, and comprehensively detecting the mixing uniformity of a sample by adopting three modes of a slicing observation method, a performance test method and a color difference detection method; s72, parameter targeted adjustment, namely, if the detection of the pre-printed sample is unqualified, the technological parameters are targeted adjusted according to the defect type: If the mixing uniformity does not reach the standard (98 percent), the ultrasonic power is increased by 10 to 15 percent, the total residence time of the materials in the mixing cavity is prolonged by 0.5 seconds, and the speed of the stirring structure is adjusted to the upper limit of the middle section; if the streak defect exists, adjusting parameters of an ultrasonic device, prolonging the starting time of the ultrasonic device by 1-2s, shortening the stopping time by 0.5-1s, and simultaneously improving the temperature of a homogenization section in the middle of a mixing cavity by 2-3 ℃; If the color lump defect exists, recalibrating the feeding proportion, adjusting the feeding speed of a corresponding feeding mechanism, ensuring that the proportion deviation is less than or equal to 1 percent, and simultaneously prolonging the residence time of the inlet premixing section by 0.3 seconds.

Description

3D printing method for improving mixing uniformity of five-mixing technology Technical Field The invention relates to the technical field of 3D printing, in particular to a 3D printing method for improving mixing uniformity of a five-mixing technology. Background The 3D printing technology, also called additive manufacturing technology, is a technology for constructing objects by depositing materials layer by layer based on digital model files, has the advantages of free molding, high customization degree, no need of a mold, short production period and the like, and is widely applied to a plurality of fields of manufacturing industry, medical treatment, aerospace, literature and the like. With the continuous development of 3D printing technology, single-material or dual-color/dual-material printing has failed to meet the requirements of high-end customization and functional integration, and multi-mixing technology has arisen, wherein five-mixing technology (mixing five materials/colors simultaneously) is taken as an important development direction of multi-mixing technology, so that the manufacturing of functional gradient, multi-color gradient or multi-performance integrated components can be realized, and the application boundary of 3D printing is further expanded. At present, five-mixing 3D printing technology is mainly based on FDM, polyJet, SLS and other technologies, and synchronous or on-demand mixed deposition of five materials (such as polymers with different performances, pigments and functional fillers) is realized through multi-extruder/multi-material-path integration. However, compared with the double-mixing technology, the five-mixing technology faces a technical bottleneck which is difficult to break through in terms of mixing uniformity, becomes a core problem which restricts the large-scale industrialized application of the five-mixing technology, and particularly in a printing scene of a molten high-viscosity material, the mixing uniformity problem is more remarkable, and is mainly represented by the following aspects: First, laminar diffusion of the molten high viscosity material is slow and the five phases of material are unevenly mixed. In the five-mixing technology, most of the five molten state materials are high-viscosity polymers (such as PLA, ABS, PETG, ASA, HIPS (high-impact polystyrene), PVA (polyvinyl acetate), soluble supporting materials and the like), the Reynolds number is extremely low, the flowing state is laminar, and the molecular diffusion speed is extremely slow. When five laminar materials are directly mixed, full diffusion of molecular level is difficult to realize, and uneven mixing defects such as stripes, color blocks and the like are easy to form, and particularly in printing of small-size and thin-wall parts, the defects are more obvious, and the appearance quality and the performance consistency of a printed finished product are seriously influenced. Secondly, the five-in-one flow channel design is easy to form dead zones, so that material residues and clamping materials are caused. The existing five-mixing cavity mostly adopts a straight barrel type flow channel design of five in and one out, and five materials directly enter the same mixing cavity from five feed inlets for mixing. Because the structural design of the runner is unreasonable, dead angle areas such as right angles and pits are easy to form at the intersection of the runners, and the areas are called dead areas. Molten materials are easy to remain in dead areas, cool and solidify, so that flow channel blockage and material clamping are caused, the continuity and stability of printing are affected, the maintenance cost and maintenance period of equipment are increased, meanwhile, the subsequent printing materials are polluted by the residual materials, and the mixing uniformity is further reduced. Aiming at the problems, some simple process optimization schemes are also provided in the prior art, such as adjusting temperature control parameters, changing feeding speed and the like, but most of the schemes are single, lack of cooperative optimization of the whole process, and cannot fundamentally solve the problem of mixing uniformity of five mixtures. For example, the problems of slow laminar flow diffusion, dead zone residue and the like cannot be solved by only adjusting the temperature control parameters, the problems of stirring and clamping materials and high flow resistance cannot be avoided by only changing the feeding speed, the defects of stripes and color blocks of a printed finished product still can be finally caused, and the mixing uniformity cannot meet the requirement of high-end printing. The patent application number is 202311498531.3, the publication date is 2024.02.09, a multi-material printing device and a gradient composite material preparation method are disclosed, the multi-material printing device comprises a mixing structure and a printing structure, the mixing structure c