Design And Research Of Laser-assisted Two-stage Screw Rapid Fused Deposition Nozzle

As the frontier technology of science and technology development,3D printing technology is one of the research hotspots in the world today.Fused deposition modeling(FDM)is one of the most widely used 3D printing technologies because of its simple principle,low equipment cost,wide range of molding raw materials and short production cycle.At present,FDM printers generally have the problem of slow printing speed.In order to solve this drawback,some scholars have changed the printer nozzle into the traditional screw extrusion structure.However,compared with the traditional FDM printer,this method has greatly increased the volume and weight of the nozzle,and caused a decline in the resolution of printed parts,which makes it difficult to apply to desktop FDM printers.In this paper,a laser-assisted two-stage screw extrusion device is designed,which uses laser preheating to overcome the problem of low heat penetration rate of polymer wire,and uses screw to increase the pressure difference between both ends of nozzle to overcome the problem of nozzle blockage.It can ensure that the resolution of printed parts does not decrease and the volume of nozzle is not too large on the basis of increasing the printer speed.In this paper,a laser-assisted two-stage screw extrusion device is designed,which uses laser preheating to overcome the problem of low heat penetration rate of polymer wire,and uses screw to increase the pressure difference between both ends of nozzle to overcome the problem of nozzle blockage.It can ensure that the resolution of printed parts does not decrease and the volume of nozzle is not too large on the basis of increasing the printer speed.The main research contents of this paper are as follows:According to the structural design of extrusion nozzles in related patent documents of FDM printer,the advantages and disadvantages of these nozzles are compared and analyzed.Based on this,a laser-assisted two-stage screw extrusion nozzle is designed,and its working principle and characteristics are expounded.Using relevant formulas and referring to the dimensions of related serialized originals,the dimensions of each component in the new nozzle are preliminarily determined.This paper analyzes and optimizes the key components of the new printing nozzle,such as micro screw and extrusion nozzle.The internal pressure field and velocity field of micro screw were analyzed by finite element method,and compared with theoretical derivation,the key factors affecting extrusion ability were explored.The geometric parameters such as spiral angle,groove width,groove height and barrel clearance of micro screw were analyzed,and the key parameters affecting extrusion flow rate were obtained,and the micro screw structure was optimized.The flow conditions of molten polymer under different nozzle contraction angles and different die lengths are compared,and based on this,the optimal parameters of nozzle are determined.The morphology evolution of the molten polymer after leaving the nozzle was analyzed,and it was concluded that the extrusion swell ratio could be used as one of the indexes to evaluate the resolution of FDM printing nozzle.Simulation and experiment were designed to verify that the swell phenomenon of the new nozzle would not increase significantly compared with the traditional nozzle.The rheological properties of polymer materials are used to study the melting behavior of materials and the extrusion swell phenomenon of extruded polymers during FDM extrusion.The correctness of analysis and numerical simulation is verified by experiments,and the linear regression equation of swell ratio with nozzle temperature and extrusion speed is fitted according to experimental data.Based on the extrusion swell simulation of traditional nozzle,the swelling phenomenon of new nozzle is analyzed,and the influence of screw speed and nozzle temperature on extrusion swell phenomenon is studied.Compared with the regression equation of traditional nozzle,it is proved that the new nozzle can ensure that the resolution of printed parts does not decrease on the basis of improving printing speed.