Study On Temperature Control And Precision Improvement Of Molding Chamber For Fused Deposition Modeling

The Fused Deposition Modeling(FDM)is a combination of the melt-solidification and CAD technology,which accumulates materials through layers.After years' development,FDM has become an important method of the additive manufacturing on the basis of the fact that it is easy to manufacture and design the complex parts with less manufacturing cycle and cost.Currently,it has a wide range of demands in aerospace,industrial manufacturing,etc.Driven by the demands,FDM has higher requirements for the quality as well as the accuracy of the molded parts.However,in the printing process of FDM technology,there are many existing problems,such as molded parts' warping and interlayer separation caused by the thermo-physical properties of ABS wire and the temperature field of the molding room.Since the FDM technology makes the high temperature plastic wire directly adhere to the solidified wire on the heating base plate,The temperature gradient and thermal stress accumulation during processing will greatly affect the quality and accuracy of the molded parts.In this thesis,the quality and accuracy of the molded parts are optimized by adjusting the temperature of the molding room.Specifically,ANSYS software's finite element numerical simulation technology and the life-death element technology are applied to conduct the transient numerical simulations of the temperature field,stress field,and the deformation in the FDM process.At the same time,the modal changes of the molded part wire,the realization theory,and the forming experiment are employed to conduct the overall analysis and local analysis to obtain FDM's suitable temperature field,the molding process theory,and the model.Through the temperature control of the molding chamber manufactured by melt deposition additive,the error of warping length of box,gear,shaft and other standard parts(formed parts)can be reduced by 0.9 to2.1 mm per 100 mm,and the error of linear length can be reduced by 0.2 to 0.6 mm per 100 mm.The research contents of this thesis can be divided into the following parts:1)At first,the properties and composition relationship of ABS material is analyzed.After that,the factors and results influenced by the heating nozzle,the curing material,and the heating base plate of ABS wire in the molding process are analyzed.Finally,the thermo-physical properties,adhesion,and elastic changes from each mode of the ABS material during printing are determined.2)The heat source load of the molding chamber is analyzed.The processes are as follows:numerically simulate the temperature field of the nozzle heat source load and the heat source load of the heating base plate,and conduct theoretical analysis and actual temperature testing to determine the nozzle of the FDM transient 3D molding process model as well as the sorts and models of the heating base plate heat source load.3)The temperature field of the molding chamber,the material's thermo-physical properties,and the latent heat of the molded part are integrated to establish a FDM transient three-dimensional molding process model.Moreover,APDL language programming is employed to realize the FDM accumulation process,initial conditions,boundary conditions,and loads,and set the material parameters.4)The transient temperature field of the FDM process is analyzed by finite element method,and the local analysis and the global analysis of the molded part are carried out.5)The thermal stress analysis and deformation verification are performed on the molded parts of the FDM process through indirect coupling.The local analysis and global analysis of the molded parts can obtain the causes for the quality and accuracy of the molded parts.Subsequently,in combination with the numerical simulation of the variable parameters,good temperature field parameters are obtained,and the results of temperature field analysis are verified by the stress field and the shape variable.The FDM experiment plan is designed,and the experiment is conducted according to the simulation molding room parameters.The actual molding quality and THE accuracy of the collection and analysis are consistent with the simulation data results,which is applied to verify the appropriate molding room's temperature field parameters and simulation conclusions.