Numerical Simulation And Experimental Study On Selective Laser Sintering Of Baozhu Coated Sand

The use of selective laser sintering technology to achieve sand rapid prototyping can solve the problems of long cycle and high mold cost in traditional sand casting,and provides an effective and effective solution for the manufacture of single-piece small-volume complex thin-walled parts used in industry.However,due to the special molding method of the selective laser sintering technology and the speciality of the process,there are new requirements for the coating process and material properties.China's preparation process and sintering process for selective laser-sintered coated sand materials are relatively late.There is still a problem of insufficient strength and precision of the sintered sample.In this paper,Baozhu sand with low angular coefficient is selected as raw material,and thermoplastic phenolic resin is used as binder to coat the film by thermal method.The process factors affecting thermal coating are analyzed to determine the addition of thermal coating.The temperature at which the resin is applied and the temperature at which the curing agent is added determine the mixing time of the addition of the resin and the addition of the curing agent.The performance of the material is compared by differential scanning calorimetry curve analysis,thermogravimetric curve analysis and normal temperature tensile strength measurement of different binder ratios,and the ratio of binder ratio is determined by single layer sintering.Sintering process parameters range.The heat transfer and flow characteristics in the sintering process were analyzed,and the bond model between the sand particles was established.The sintering mechanism of the SLS coated sand was explored.Based on the sintering mechanism and numerical simulation theory,the finite element method was used,and the software comsol was used as the platform.The finite element heat source model and geometric model of the coated sand material are established.The physical properties of the material and the boundary conditions of the simulation process are considered.The multi-field coupling simulation analysis of the coated sand sintering process is carried out to obtain the temperature field data and the multi-particle model sintered neck.The variation law,the influence of processing parameters and binder ratio on the simulation results are discussed,which provides theoretical support for the preparation of coated sand materials and optimization of sintering process parameters.Using orthogonal test method,the optimal binder ratio was selected to optimize the sintering process parameters.Taking the tensile strength and precision as the considerations,the influence factors of the four factors(preheating temperature,laser power,scanning speed and powder layer thickness)which have great influence on the sintered parts are analyzed,and the optimal process parameters of SLS are obtained.And using this parameter to print the sand mold of the part,the precision and quality of the obtained parts are good.