Modeling and Investigation of Spatial Operation Stiffness in Robotic Milling Process Considering Bidirectional Weak-Stiffness of Robot-Workpiece System

Abstract Complex cylindrical light alloy structural castings are widely used in the aerospace industry due to the simple forming process and complex internal cavity structure. Robots can make up for the shortcomings of traditional thin-walled cylindrical parts machining because of the low cost, high flexibility and good space accessibility. This will lead to difficulties in controlling the deformation caused by milling processing. A bidirectional weak stiffness machining system is proposed in this paper. The multi-body small deformation theory and the deformation superposition principle are used to provide the operational stiffness model. Compared with the conventional robot stiffness model, the proposed bidirectional weak stiffness operating stiffness model takes into account the stiffness characteristics of both the machining end and the workpiece end, which is more practical and comprehensive. At the same time, a milling vector stiffness performance index for thin-walled cylindrical parts robot machining is proposed, which can reflect the influence of the system stiffness characteristics on the machining wall thickness accuracy more intuitively. The stiffness characteristics of the machining system are studied by finite element analysis, and the applicability of the proposed stiffness model and stiffness index is verified. This study can guide the subsequent robot machining trajectory planning and process parameter optimization.