Study On Forming Mechanism And Process Of 3D Printing Based On Polymer Metal Composites

Compared with traditional manufacturing technology,layered manufacturing and layer-by-layer superimposed method is used in 3D printing technology to manufacture products.It has the advantage that complex products without the need of molds can be manufactured,and the application range is more and more extensive.However,the traditional metal 3D printing technology has the shortcomings of expensive equipment and high energy consumption,a polymer metal composite material suitable for fused deposition molding(FDM)is developed and the printing process is explored in the paper to achieve low-cost metal 3D printing manufacturing.Firstly,according to the requirement of FDM forming process for printing faliment,polyformaldehyde(POM),polypropylene(PP),zinc oxide,dioctyl phthalate(DOP)and dibutyl phthalate(DBP)were selected to extrude and draw with 316L stainless steel powder and SKD11mold steel powder respectively,and 316L stainless steel faliment and SKD11 mold steel faliment were prepared.The final printability of two kinds of faliment were verified by characterization test.The POM and PP is added to make the metal powder disperse well;the zinc oxide is added to improve the thermal decomposition temperature of POM and PP;the DOP and DBP mixture is added to improve the molecular chains'mobility of POM and PP,the crystallinity is reduced so that the melting temperature is lowered and the temperature range of FDM process is broadened.L9(3~4)orthogonal experiment was designed to study the effect of printing process parameters on the dimensional accuracy of green parts.The experimental results show that the the filling line width has a significant effect on the dimensional accuracy of green parts.When the value of filling line width is 0.8 mm,the dimensional accuracy of green parts is the highest.When the thickness of the layers is less than 0.3mm,the structure with a hanging angle of 25degrees can be formed and the surface quality keeps good.A warpage deformation model of FDM parts is established and the experiment proves that the layer thickness has the most significant effect on the warpage deformation of FDM parts.The bigger the layer thickness makes the smaller the warpage deformation.Under the condition of guaranteeing the requirement of dimensional accuracy for the green parts,layer thickness,filling ratio,nozzle temperature,hot bed temperature and printing speed are selected as experimental factors,after printing out test splines,the finished metal parts are obtained by degreasing and sintering.The effects of experimental factors on mechanical properties of metal parts are analyzed.The results show that the effects of various experimental factors on 316L stainless steel faliment and SKD11 mold steel faliment are basically the same.The effect of layer thickness on the tensile strength of metal parts is relatively weak;the increase of nozzle temperature and the higher bed temperature are helpful to enhance the tensile strength of metal parts;the stable printing quality is easier to be obtained by lower printing speed.The filling rate has the most significant effect on the mechanical properties of the metal parts.The higher the filling rate,the better the mechanical properties of the finished product,and it has a linear relationship.When the layer thickness is 0.25 mm,the filling ratio is 100%,the nozzle temperature is235?,the printing platform temperature is 113?and the printing speed is 20 mm/s,the metal parts of SKD11 mold steel faliment achived the maximum tensile strength for 1073MPa;when the layer thickness is 0.30mm,the filling ratio is 100%,the nozzle temperature is 230?,the printing platform temperature is 117?and the printing speed is 20mm/s,the metal parts of316L stainless steel faliment achived the maximum tensile strength for 442 MPa.