Research On Preheating Temperature Field And Accuracy Based On PS Powder Of Selective Laser Sintering

Compared with the traditional molding methods,selective laser sintering has the advantages of short production cycle,no need of molds,and material saving,and has significant advantages in the fields of individualization and trial production of small batch products.Due to the characteristics of "powder sintering,layer by layer accumulation" of the process,Its forming quality and accuracy are severely restricted by the proper preheating temperature field uniformity and technological parameters.However,Because of the design of the heating system,the temperature field of the selective laser sintering equipment is very uneven.The current selective laser sintering equipment has the phenomenon of high temperature in the middle area and low temperature around the side corner.but currently The choice of parameters often depends on experience.Therefore,this paper takes the work area of 400mm*400mm as the research object,establishes the mathematical model of preheating temperature field by MATLAB simulation software,analyzes the influence law of different heating system layouts on the preheating temperature field,and then puts forward the preheating optimization scheme;Based on the PS powder material,the influence rule of the process parameters on the dimensional deviation of the part and the optimization method were studied.The main research contents and conclusions of this paper are as follows:(1)The establishment of a mathematical model for preheating temperature field of selective laser sintering.By analyzing the energy transmission mechanism during the preheating process of the tube preheating device and the radiant heat flux density on the surface of the powder bed,a three-dimensional mathematical analytical model of the powder bed in the preheating process was established and numerical simulation was performed using MATLAB simulation software.(2)The effect of lamp length,height and spacing on the preheating temperature field.Based on different lamp lengths,heights,and spacings,the effect of the three on the preheat temperature field is explored.The results show that the homogeneity of the preheating temperature field becomes better first and then worse as the height of the lamp increases,and it becomes better as the length and spacing of the lamp increase.(3)Design of preheating scheme based on short pipe compensation.In view of the phenomenon of high temperature in the middle area and low temperature in the surrounding corner area,a compensation scheme is put forward to add short tube at the side corner of the original lamp,and the influence of the length of the short tube on the preheating temperature field uniformity is explored.The results show that the uniformity of preheating temperature field first becomes better and then becomes worse with the increase of short tube length.When the length of the short tube is 60 mm,the uniformity of the preheating temperature field is the best.(4)The influence of process parameters on dimensional deviations and the determination of optimal process parameters.Taking PS powder as the research object,based on BBD experimental design method and response surface analysis method,the influence of four parameters of laser energy,scanning distance,layer thickness and scanning speed on the dimensional accuracy of SLS parts was studied,The best combination of process parameters is obtained and verified by experiments.The results show that the size deviation rate decreases with the increase of scanning speed and laser power,increases with the increase of scanning distance,decreases first and then increases with the increase of layer thickness;the optimal combination of process parameters was laser power of 50%(15W),scan spacing of 0.12 mm,layer thickness of 0.20 mm,and scan speed of 2200 mm/s.