Effect Of Heat Dissipation Conditions On The Bonding Quality Of FDM Filaments

Fused Deposition Modeling (FDM) is widely used in the field of Additive Manufacturing technology. Improving the processing property of FDM equipment, enhancing the quality of parts and achieving the transformation from ordinary prototype to functional parts, is of great significance for the development and improvement of FDM process.The purpose of this paper is to improve the filaments bonding quality of FDM parts. Filaments bonding strength, modeling dimensional accuracy and warpage deformation are selected to be the evaluation objectives. The cooling factors such as the ventilation velocity in the modeling regional, the envelope temperature, the platform temperature and the layered area are investigated primarily.Based on the theory of polymer melt interface diffusion, the bonding mechanism of amorphous polymer filament is elaborated, and the theory model of bonding strength between filaments is set up, which provide a criterion to assess the bonding degree. On the basis of heat transfer theory and reasonable assumptions, the cooling model of a single deposited filament is derived, and the influence rules of different cooling factors on the temperature history of filament are obtained under certain conditions. Several shrinkages and deformations of filaments are analyzed, it is verified that the molecular orientation and flow deformation shrinkage have influences on modeling dimensional accuracy, and the uneven orientation contraction of filaments is the cause of warpage deformation.The cooling factors effecting on the bond strength, shrinkage, warpage deformation of FDM part are investigated and analyzed by methods of orthogonal design, interlaminar tensile test, microstructure observation, temperature data collection as well as disorientation through water bath. The impact trend and significance degree of cooling factors and levels that influence on the measurements are evaluated. According to the characters of filament disorientation, the measuring method of orientation shrinkage rate and flow deformation shrinkage rate is presented. Some measures are proposed to improve filaments bonding quality for different sectional parts.