Fused Deposition Modeling With Variable Hierarchy Thickness

The intensified competetion under manufacturing globalization and the fast growth of diversified market demands motivate manufacturers to rapidly provide cusumers with customized products at a reasonably low cost. Rapid prototyping (RP)technology with its innovative manufacturing ideas, rapid product manufacturing speed and flexible product models, greatly shortens the product development cycle, reduces the development cost and improves the rapid reponse ability of enterprises to the market demand.As one of the most widely used PR techniques, fused deposition modeling(FDM) is less competetive in modeling precision and efficiency due to the trade-off between them. For this reason, the paper presents a new modeling method featuring variable hierarchy thickness, and collaboratively optimizes the modeling precision and efficiency in FDM from the perspectives of hierarchy orientation and thickness.Based on the impact analysis of the hierarchical orientation on modeling precision and efficiency, a FDM hierarchy orientation model was formulated with 3 objectives of minizing the volume error, workpiece height in the modeling orientation, and supporting volume. A non-dominated sorting genetic algorithm was designed to seek the Pareto optimal solutions of any complex model. Finally, the correctness of the proposed model and the efficiency of the devised algorithm were validated with 2 case studies.Hierarchy thickness is a key parameter in FDM in that it is closely related to the modeling precision and efficiency. In current work, it is generally fixed value considering the trade-off between the modeling precision and efficiency. The paper presented a modeling method consisting in regulating the hierarchy thickness Specifically, the contour hierarchy uses a small thickness to guarantee the workpiece surface qualith, while the packed hierarchy uses a layer thickness to increase the modeling efficiency. To asvertain the effectiveness of this method on modeling precision, efficiency and strength, experiments were conducted. Results show that this method is capable of improving the surface quality,and increasing the modeling efficiency as well.Modeling process of FDM was simulated with the birth-death element module of ANSYS package. Firstly, the temperature field was analyzed, and then stress and strain field using the results of temperature field. Through coupled thermal-mechanical analysis, the variations of temperature, temperature gradient and stress of different nodes with time were obtained. Further the workpiece deformation was obtained. Results showed that the stress mainly concentrated in the x and y directions due to hierarchical modeling, and the new modeling method caused a bigger deformation than that with the traditional methods.This paper provides the basis for the selection of FDM modeling parameters by optimizing the hierarchical orientation and thickness, It proves to be meaningful for collaborative optimization of modeling precision and efficiency in FDM.