Study On Parameters Optimization Of Multi Index Molding Process For PS/ABS Composite Powders Based On Selective Laser Sintering

To address the problems of SLS polystyrene(PS)parts which currently do not fit the requirements for large-scale complex parts due to the surface is rough,the molding accuracy and strength are low in the selective laser sintering(SLS)process.This thesis proceeds the forming mechanism of SLS process,the selection of molding materials,the preparation,performance testing of composite powders and the selection and optimization of forming processing parameters for SLS process which were systematically studied.Firstly,according to the properties of PS powder,acrylonitrile-butadiene-styrene plastic(ABS)was selected to modify PS powder.PS/ABS composite powders were prepared by mechanical mixing method.The optimum ratio of PS/ABS composite powders was obtained by the single factor experiment and orthogonal tests.The optimum component of PS/ABS composites include 88.09% PS powder,10% ABS powder,1.5% antistatic agent,0.01%fluorescent brightener and 0.4% heat stabilizer.The performance of the composite powders consist of average particle size is 70.92?m,most of the shape of the particle is spherical,glass conversion temperature is 95.66 ?,ash content is 0.115%.Secondly,the forming process parameters affecting PS/ABS composite powder were analyzed comprehensively.According to the material properties and research needs,the preheating temperature,laser power,scanning speed and single layer thickness were selected as the process parameters to be studied.The forming quality was measured by the relative error of size,surface roughness and bending strength.The single factor experiment was employed to study the changing regularity between process parameters and test indexes.The suitable molding range of PS/ABS composite powder was determined.The preheating temperature is 80?~90?,laser power is 25W~35W,scanning speed is 1800mm/s~2200mm/s,and single layer thickness is 0.22mm~0.26 mm.Meanwhile,the morphology of the formingparts were studied by SEM under the different laser forming parameters.It is revealed that the microstructure of the parts is similar when the energy density is equal,However,when the energy density is different,the difference is greater.The larger the laser energy density is,the less the internal porosity of the forming part is.Finally,the optimal SLS process parameter was determined by using orthogonal test and comprehensive balance method,moreover,the best parameters combination is preheating temperature 85?,laser power 30 W,scanning speed 2000mm/s and single layer thickness0.24 mm.At this time,the relative error of Z-axis for SLS forming parts is 3.56%,the surface roughness is 17.95?m,and the bending strength is 4.81 MPa.On this basis,two prototype parts of PS/ABS composite powders with a certain degree of complexity were sintered.This verifies the rationality of parameter optimization,and lays the foundation for future research.This paper provides a reliable material basis for rapid melting mold precision casting,and also provides theoretical guidance for the selection and matching of laser parameters for sintered large-size complex prototype.