Research On Key Factors Affecting Molding Quality Of Selective Laser Sintering

Selective Laser Sintering Technology(SLS),as an additive manufacturing technology,has the characteristics of wide application of molding materials,high material utilization rate,and simple process.It can sinter complex parts in a short time and is increasingly subject to the favor of modern processing and manufacturing.However,the shrinkage and warpage deformation of the molded part during the molding process will lead to a deterioration in molding quality,and the degree of deformation of the molded part is directly related to the density of the powder before laser sintering and the preheating temperature field.Therefore,in view of the above problems,this paper studies the influence of process parameters of powdering and preheating on powder density and preheating temperature,optimizes the corresponding parameters,improves the density of powder layer and the uniformity of preheating temperature field,reduces the shrinkage deformation and warpage of molded parts,and improves the quality of the molded part.The specific research contents are as follows:Firstly,the influence of the process parameters of the powder spreading device on the powder density was investigated.Based on the kinematics analysis of the powder laying device,the force model of the powder particles under the action of the powder roller was established.According to the theoretical analysis of the model,the influence of the radius size,roughness,rotation direction,speed and the translation speed of the scraper and the powder roller on the quality of the powder was studied.The EDEM software was used to simulate the powdering process,and the influence of each parameter on the dusting density was analyzed.Secondly,the characteristics of the powder preheating temperature field were investigated.A method for comprehensively adopting lamp tube heat radiation and heating with heat conduction preheating metal powder was proposed.The heat radiation model of the lamp tube to the powder layer was established,the heat radiation effect of the lamp tube on the surface layer of the powder layer was analyzed,and the surface heat radiation problem of the powder layer was abstracted into the surface radiation problem in the three-dimensional space.According to the radiation heat transfer theory,the angle coefficient parameter was introduced to describe the proportion of the surface radiant energy emitted by the powder absorption tube;By using the symmetry characteristic of the powder in the cylindrical cavity along any one of the diameter directions,the heat conduction process of the heating zone to the powder layer was simplified to one-dimensional heat conduction in the radial direction.The heat transfer model of the heating belt to the powder was analyzed and the temperature value of the powder layer at different positions in the radial direction was calculated.The uniformity coefficient was introduced to reflect the uniformity of the preheating temperature field of the powder layer under the combined action of the thermal radiation of the lamp and the heat conduction of the heating zone.In view of the uncertainty of the powder preheating model,the fuzzy algorithm was used to control the preheating temperature value,and the adaptability of the preheating temperature control was improved.Finally,the experiment was verified.The software and hardware design of the powder coating module,the laser control module and the preheating temperature control module were completed.The correctness of the theoretical analysis was verified by the powder laying experiment,the preheating temperature field uniformity and the temperature value control experiment.