Robotic machining could provide a solution for removing supports from metal additive manufactured workpieces, replacing labor-intensive work. However, the robot’s intrinsic weaknesses of low positioning accuracy and structural rigidity primarily restrict its applications. Improving the accuracy of robotic machining remains an unresolved issue. A mixed solution is proposed, in which a portable CNC machine with the capability of visual feature recognition is equipped with a universal industrial robot. The robot implements positioning motions in a large space, while the portable CNC fulfills accurate machining motions on a local feature of the workpiece. A sizeable weight of the portable CNC exerts a moderate load on the industrial robot’s joints, increasing joint stiffness. The mixed machining system exhibits high accuracy and stiffness when milling a steel/titanium alloy workpiece, achieving tolerances up to ±0.04 mm on a 60×80 mm U-shaped path without exciting any structural vibration modes. When the dimension of the workpiece exceeds the machining range of the portable CNC, a combined algorithm of coarse-fine registration based visual identification and robot error compensation is designed to align the spatial coordinates of the machining motion with that of the positioning motion, thereby extending the machining range with high accuracy. Through the proposed mixed robot machining method, experiments of doubling the machining range have been done to verify that the mixed machining robotic system is able to slot a 550 mm-long path with accuracy of ±0.1 mm. Furthermore, the mixed robotic machining system is applied to recognize and remove multiple supports of lattices, grids and ribs from a titanium-alloy additive manufactured thin-wall workpiece with high accuracy and high efficiency.

中文翻译：

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混合机器人加工系统的设计及其在金属增材制造薄壁零件支撑去除中的应用


机器人加工可以提供一种解决方案，从金属增材制造的工件上去除支撑，取代劳动密集型工作。然而，该机器人定位精度低、结构刚度低等固有缺点主要限制了其应用。提高机器人加工的精度仍然是一个尚未解决的问题。提出了一种混合解决方案，其中具有视觉特征识别能力的便携式数控机床配备了通用工业机器人。机器人在大空间内实现定位运动，而便携式数控系统则在工件的局部特征上实现精确的加工运动。便携式数控系统的较大重量对工业机器人的关节施加了适度的负载，增加了关节的刚度。该混合加工系统在铣削钢/钛合金工件时表现出高精度和刚度，在 60×80 mm U 形路径上实现高达 ±0.04 mm 的公差，且不会激发任何结构振动模式。当工件尺寸超出便携式数控加工范围时，设计基于视觉识别的粗精配准与机器人误差补偿相结合的算法，将加工运动的空间坐标与定位运动的空间坐标对齐，从而扩展加工范围。加工范围大，精度高。通过所提出的混合机器人加工方法，进行了加工范围加倍的实验，验证了混合加工机器人系统能够以±0.1 mm的精度开槽550 mm长的路径。 此外，混合机器人加工系统还应用于高精度、高效率地识别并去除钛合金增材制造薄壁工件上的格子、网格和肋的多个支撑。