| Fused deposition modeling is a kind of additive manufacture technology based on molten filament extrusion and bond accumulation layer by layer through the nozzle with heating device.Compared with other additive manufacturing technologies,fused deposition modeling has the advantages of high material utilization,low maintenance cost and simple post-processing without laser device,which is especially suitable for small multi batch and high flexible processing and manufacturing requirements.Polylactic acid(PLA)filament has been widely used in fused deposition modeling technology,which is characterized by degradable green,no pollution,good thermal stability and easy processing.Fused deposition modeling,however,relies on the layer-by-layer accumulation of the hot melt and adhesion properties of the wire,making the formed parts all anisotropic,and their mechanical properties are lower than those of injection molded parts of the same material.In addition,fused deposition modeling is still mainly based on thermoplastic materials such as PLA,which does not have any functionality.The scope of engineering applications is limited,which seriously restricts the development of this technology.Carbon nanotube(CNT)has excellent mechanical and electrical properties,which is ideal fillers for improving PLA performance.Therefore,in view of the method of CNT reinforced PLA functional parts of fused deposition modeling,a mass production method of CNT/PLA functional composite wire suitable for fused deposition modeling is proposed.The method of finite element simulations and experimental studies are employed to comprehensively research the fused deposition modeling process of the CNT reinforced PLA functional parts,in order to imporove the mechanical and electrical properties.A method of PLA functional parts of fused deposition modeling reinforced by carbon nanotubes is proposed.Based on the composite mechanism of functional polymer composites,the CNT/PLA composite wire was used to form functional parts by using its excellent mechanical and electrical properties.The direct relationship between the extrusion parameters and the diameter error of the filament was established.The influence of the parameters on the diameter error of the filament was analyzed.High quality CNT/PLA composites filaments were obtained by selecting the optimum process parameters.The thermal stability test and rheological property test are carried out for the obtained filaments,and the filaments with appropriate melt index is selected for fused deposition modeling process to obtain high mechanical properties and good conductivity.The microstructure of the formed part and the tensile fracture surface are obtained through experiments,and the relationship between the mechanical properties and conductivity of the formed part and the micro morphology is analyzed.A finite element numerical model for extrusion process of CNT reinforced PLA functional parts of fused deposition modeling is established.The temperature field and velocity field distribution during the extrusion process of fused deposition modeling are studied by means of finite element simulation and experiment.The dynamic viscosity of different CNT/PLA composites with different temperature were obtained by experimental measurement,which can be transformed into kinematic viscosity and fitted to obtain the second-order viscosity temperature curve.Based on the analysis of the influence of the nozzle fan and radiator on the convective heat transfer coefficient of the nozzle surface,a finite element numerical model for the extrusion process of fused deposition modeling considering the viscosity of the filament was established.The effects of nozzle diameter,forming temperature and feeding speed on the temperature distribution and velocity distribution in the extrusion process were obtained,and the effects of filament viscosity on the velocity distribution in the extrusion process were explored.The accuracy of the established model was verified by experiments,which laid a foundation for the realization of fused deposition modeling of high viscosity CNT/PLA composites and the development and research of new materials.The finite element numerical model of the temperature field in the deposition process of the fused deposition modeling is established,and the temperature field distribution in the deposition process studied by the combination of finite element simulation and experiment.Journal batch processing is used to divide the mesh and set boundary conditions.The deposition process of fused deposition modeling is realized by using fluent dynamic mesh technology and user-defined function.The effects of forming temperature,layer thickness and base plate temperature on the solidification time of the melt filament are analyzed,and the effect of solidification time on the bonding effect of the forming process is explored.The effects of different deposition process parameters on the mechanical properties and forming accuracy of the forming part are obtained through experiments,and the relationship between the solidification process and bonding effect and the mechanical properties and forming accuracy of the forming part is analyzed.A solderless printed circuit manufacturing method based on CNT reinforced PLA functional parts of fused deposition modeling technology is proposed.The direct relationship between the process parameters and the resistivity of the formed part is established.The influence law of the conductivity of the CNT reinforced PLA functional parts is analyzed.The influence of the shape and cross-section of the conductive circuit on the conductivity is studied.The optimal forming process parameter combination and the optimal circuit cross-sectional area obtained are applied to the geometric modeling and pre-processing layering of the solderless printed circuit.Using of carbon nanotube/polylactic acid functional composite wire with fused deposition modeling technology,the integrated design and manufacturing of parts and the solderless three-dimensional circuits are realized. |
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