As a promising additive manufacturing method, direct energy deposition has been widely used to fabricate complex thin-walled parts. However, some defects such as uneven layer surface and excessive build-ups always occur in this process. In this study, a high-fidelity model adopting a novel laser/powder source is developed to simulate the detailed multi-layer deposition process. With layer surfaces being tracked in real-time, laser source model incorporates local incidence angle and defocusing amount to adjust absorbed energy and beam radius on the track surfaces. The powder catchment efficiency varies with the defocusing amount timely. The simulations demonstrate that build-ups are mainly induced by unstable linear powder feed rate and worsen due to laser/powder defocusing and accumulated heat. The layer surface unevenness results from powder positive defocusing, while molten pool dynamics, laser positive defocusing and accumulated heat plays a supplementary role. Eliminating methods are proposed based on the simulations and validated by experiments.

作为一种有前途的增材制造方法，直接能量沉积已广泛用于制造复杂的薄壁零件。但是，在此过程中总是会出现一些缺陷，例如层表面不均匀和过度堆积​​。在这项研究中，采用新的激光/粉末源的高保真模型被开发来模拟详细的多层沉积过程。通过实时跟踪层表面，激光源模型结合了局部入射角和散焦量来调整轨道表面上的吸收能量和光束半径。集粉效率随散焦量的变化而变化。模拟表明，堆积主要是由不稳定的线性粉末进料速度引起的，并且由于激光/粉末散焦和热量积累而加剧。层表面不均匀性是由粉末正散焦引起的，而熔池动力学，激光正散焦和积聚的热量起补充作用。在模拟的基础上提出了消除方法，并通过实验进行了验证。