In respect of laser metal deposition (LMD) 3-D additive manufacturing technology, the method of non-parallel slicing is applied for the deposition of the overhanging and unequal-height parts and is capable of improving the deposition accuracy, stability and efficiency. Nevertheless, the produced uneven top surface derived from variable height deposition process has a possibility to result in instability and even failure of the deposition. In this study, the novel control strategies for the precise control of the unequal-height part were proposed. An inside-beam powder feeding nozzle was applied for the deposition with large overhanging angle. Based on a developed deposition height control system, multiple PI controllers were designed for varying desired deposition heights in an unequal-height layer. The actual heights of the uneven top surface in different positions were memorized by the deposition of a layer, and the process parameters for the next layer could be planned in advance to smooth this unevenness. Under the proposed control strategies, a geometrical stable and convergent process was made achievable when depositing a “fan-shaped” part and a “bent-pipe-shaped” part as the typical overhanging and unequal-height structures. The microstructures were observed to be uniform and compact, and the grain sizes and microhardness in different height positions were found to vary slightly.

对于激光金属沉积（LMD）3-D增材制造技术，采用非平行切片的方法来沉积悬垂和不等高的零件，并且能够提高沉积精度，稳定性和效率。然而，由可变高度的沉积过程产生的不平坦的顶表面有可能导致沉积的不稳定甚至失败。在这项研究中，提出了用于精确控制不等高部分的新颖控制策略。使用内束粉末进料喷嘴以较大的悬垂角度进行沉积。基于已开发的沉积高度控制系统，设计了多个PI控制器以在不等高的层中更改所需的沉积高度。通过沉积一层来存储不同位置的不平坦顶表面的实际高度，并且可以预先计划下一层的工艺参数以消除该不平坦。在提出的控制策略下，当沉积“扇形”部分和“弯管形”部分作为典型的悬垂和不等高结构时，可以实现几何稳定和收敛的过程。观察到微观结构均匀且致密，并且发现在不同高度位置的晶粒尺寸和显微硬度略有变化。当沉积“扇形”部分和“弯管形”部分作为典型的悬垂和不等高的结构时，就可以实现几何稳定和收敛的过程。观察到微观结构均匀且致密，并且发现在不同高度位置的晶粒尺寸和显微硬度略有变化。当沉积“扇形”部分和“弯管形”部分作为典型的悬垂和不等高的结构时，就可以实现几何稳定和收敛的过程。观察到微观结构均匀且致密，并且发现在不同高度位置的晶粒尺寸和显微硬度略有变化。