Dynamic optimization of an electro-spindle for robotic machining

A methodology is proposed to optimize an electro-spindle for robotic machining applications. In addition to the common maximization of the material removal capability, other requirements are specific for the robotic application: minimization of the weight and estimation of the cutting force on the tool by a special embedded sensor. A parametric dynamic model of the spindle is built, integrating reduced order finite element models of the main structural elements (housing, rotating shaft, preload piston and tools), taking into account the boundary conditions provided by the robot end-effector. A damping solution based on elastomeric dampers is considered. The dynamic performance are evaluated by computing objective functions that take into account critical speeds, imbalance vibrations, regenerative chatter stability and forced vibrations for two reference milling operations. Additionally, the embedded sensor requires to assure a sufficient shaft displacement at sensor locations, to get the desired resolution in cutting force estimation.