Research On The Optimization Of 3D Printing Equipment And The Enhancement Process Of Products Based On Melt Differential Principle

The rapid development of 3D printing technology has changed the traditional cutting mode,which can realize quick and near net forming of complex products,and reduce the cost of product development,shorten product development cycle and so on.In view of the problems of high cost,less species and high requirements for rigidity and toughness of printing consumables in the current FDM technology,a screw plasticizing melt differential 3D printer,which can use plastic particles as printing consumables,has been developed.Based on the melt differential 3D printer as the basic experimental platform,this subject analyzed and summarized the existing problems of the 3D printer and put forward the improvement plan by 3D printing and testing many high-viscoelastic polymers;The enhancement mechanism of 3D printing carbon fiber(CF)composites and the enhancement mechanism of heat treatment of 3D printed samples were studied.The optimization scheme of this 3D printer head was proposed through the simulation of heat transfer in ANSYS.On the basis of this,a melt pump type-3D printing device was proposed innovatively and trial-manufactured successfully.The heat transfer differences before and after the improvement was analyzed and compared by heat transfer simulation as well.The extrusion process of the melt gear pump was simulated by Poly flow,which provides the parameter basis for its accurate application in 3D printing.The main works were summarized as follows:1.Through the printing test of high viscosity cellulose acetate(CA),the feasibility of CA for 3D printing consumables was analyzed.The bonding strength of CA samples bonded by acetone is tested,which had explored the feasibility of the blocked-printing and bonding-forming of large CA products.In addition,the shortcomings of the printer were summarized,and the improvement scheme was put forward and implemented.2.The effects of different fiber's content,different fiber's length,different filling angles and the nitric acid treatment of carbon fiber's surface on the tensile,bending and impact strength of 3D printed PLA/CF composites specimens were studied and compared with injection molded parts.The enhancement mechanism of 3D printed carbon fiber reinforced specimens was analyzed as well.In addition,the influence of different heat treatment temperature on the tensile strength of 3D printed PLA specimens was also studied and further interpreted from the perspective of the change of material's crystallinity.3.The heat transfer of the original head of 3D printer was analyzed by using the internal steady heat transfer module in ANSYS workbench and the reason for the larger temperature difference in the hot runner of the head was explained and the printer's head was improved later.On the basis of this,a melt pump type-3D printing device was proposed innovatively and trial-manufactured successfully.The heat transfer differences before and after the improvement was analyzed and compared by heat transfer simulation as well.The advantages of using the melt pump as the head of the 3D printer in terms of heat transfer were summarized.4.Using the Poly flow module in ANSYS workbench,the melt's extruding process in the melt pump was simulated,including the influence of different inlet pressure and gear speed on the outlet mass flow and the average extruding pressure at the outlet.The relationship between these parameters of inlet and outlet of the melt pump was obtained through linear fitting,which provided the basis for its accurate application in 3D printing.