Study On Temperature Field Simulation And Process Parameter Optimization Of Semiconductor Laser Heating Assisted FD

Fused deposition modeling(FDM)is one of the most widely used 3D printing technology due to its simple principle,low cost and wide range of materials.However,in the process of FDM,the polymer wire often appears incomplete heating due to its low thermal conductivity,which not only affects the adhesion effect between printing layers,but also leads to significant radial thermal gradient.If the wire is not sufficiently heated when it reaches the nozzle reduction,the required extrusion pressure will increase sharply with the increase of the feed rate.Therefore,because of the low heat penetration and incomplete heating of FDM printing wire,the printing speed is often slow and the nozzle is blocked.In this way,a research scheme of laser heating assisted FDM printing is proposed.Laser has a good thermal penetration ability for polymer printed wire.First,the laser irradiation wire preheating achieves a good thermal penetration effect,and then the resistance heating method is used to melt the wire,which can not only greatly improve the melting extrusion rate,but also effectively prevent nozzle plugging and other problems.In this paper,the theoretical model of continuous laser heating of plastic polymer was established,and the temperature field of polymer wire irradiated by semiconductor laser was simulated based on the finite element theory,so as to analyze the influence of laser process parameters on the temperature field distribution and the thermal penetration effect of wire,and optimize the combination of laser process parameters in the process of laser heating assisted FDM.Specific work is as follows:(1)Theoretical study on the thermal action of laser heating polymer.By analyzing the heat transfer process of laser heated plastic polymer,the theoretical model of continuous laser heated plastic polymer was established.Based on the theory of the interaction between laser and polymer,the expression of the relationship between laser parameters and polymer temperature change is derived according to the law of conservation of energy.Taking acrylonitrile-butadiene-styrene(ABS)wires commonly used in FDM as an example,the numerical calculation was carried out,and the relationship curves of irradiation time with laser power density and heat affected zone depth were obtained,as well as the laser parameter thresholds of glassy state and viscous state transformation of ABS wires under laser heating were obtained,which provided a theoretical basis for the selection of laser parameters of semiconductor laser heating ABS wires.(2)Simulation and experimental study on temperature field of laser heated ABS wire.The light source characteristics of semiconductor laser heat source were analyzed,and a Gaussian distribution laser heat source model was established.The DFLUX subroutine written in FORTRAN language was used to simulate the load.A three-dimensional finite element model was established,and the temperature field of laser heated ABS wire was simulated by using the heat conduction module in the standard implicit solution.The effects of laser power,spot radius and moving speed of laser heat source on laser heating effect were obtained by comparing and analyzing the simulation results.The depth and topography of the heat affected zone were observed by optical microscope.The rationality of the theoretical model,the accuracy of the numerical calculation and the validity of the simulation experiment were verified by comparing with the theoretical numerical calculation results and the simulated temperature field nephograph characteristics.In addition,an infrared thermal imager was used to measure the surface temperature of the moving ABS wire heated by laser.The reliability of the simulation model of the temperature field of the moving ABS wire heated by the moving laser heat source was verified by comparing it with the simulation temperature value.(3)Optimization of FDM process parameters assisted by laser heating.Through orthogonal design test and simulation experiment data,the primary and secondary relationship between process parameters affecting laser heating effect of ABS wire was obtained.With laser power and laser heat source moving speed as optimization parameters,with the constraint condition that the peak temperature of ABS wire surface heated by laser reaches 170℃,and with the maximum peak softening depth and minimum required irradiation time as optimization objectives,the response surface approximation model between the optimization objective parameters and process parameters was established through the full factor design of experiment(DOE).Using Curve fitting tool toolbox in MATLAB,the second-order polynomial fitting was performed on laser power and laser heat source moving speed respectively,with the peak softening depth fitting and laser irradiation duration fitting.Finally,based on NSGA-II algorithm,gamultiobj multiobjective optimization function solver was used to optimize the fitting function.A set of Pareto optimal solutions of laser process parameter combination were obtained successfully,and the optimal process parameter combination of laser heating assisted FDM was obtained.