Robotic wire arc additive manufacturing has been widely adopted due to its high deposition rates and large print volume relative to other metal additive manufacturing processes. For complex geometries, printing with variable height within layers offer the advantage of producing overhangs without the need for support material or geometric decomposition. This approach has been demonstrated for steel using precomputed robot speed profiles to achieve consistent geometric quality. In contrast, aluminum exhibits a bead geometry that is tightly coupled to the temperature of the previous layer, resulting in significant changes to the height of the deposited material at different points in the part. This paper presents a closed-loop approach to correcting for variations in the height of the deposited material between layers. We use an IR camera mounted on a separate robot to track the welding flame and estimate the height of deposited material. The robot velocity profile is then updated to account for the error in the previous layer and the nominal planned height profile while factoring in process and system constraints. Implementation of this framework showed significant improvement over the open-loop case and demonstrated robustness to inaccurate model parameters.

翻译：机器人电弧增材制造因其相对于其他金属增材制造工艺具有高沉积速率和大打印体积而被广泛采用。对于复杂几何形状，在层内采用可变高度打印具有无需支撑材料或几何分解即可生成悬垂结构的优势。该方法已在钢材打印中得到验证，通过预计算的机器人速度曲线实现一致的几何质量。相比之下，铝材的焊道几何形状与前一层的温度紧密耦合，导致零件不同位置的沉积材料高度发生显著变化。本文提出了一种闭环方法来修正层间沉积材料的高度变化。我们使用安装在独立机器人上的红外相机追踪焊接火焰并估计沉积材料的高度。随后更新机器人速度曲线，以考虑前一层的误差和名义规划高度曲线，同时兼顾工艺和系统约束。该框架的实施结果表明，相较于开环情况有显著改进，并对不精确的模型参数表现出鲁棒性。