346 / 2021-07-05 09:43:33

Modelling the Dynamics of a CNC Spindle for Tool Condition Identification based on On-Rotor Sensing

Vibration; Tool wear condition; Finite element model; On-Rotor Sensing; Dynamic characteristics of spindle

Cutting tool plays an important role in modern manufacturing industry but tool wear is unavoidable and may degrade productivity. Aiming at studying an appropriate and efficient tool condition monitoring method to improve the accuracy of finished parts, the roughness of the turned surface, a novel On-Rotor Sensing (ORS) is installed on the rotating workpiece to obtain vibration signals. To get an in-depth understand of the vibration data, a multi-degree-of-freedom (MDOF) system consisted of spindle, chuck and workpiece is established. It is found that the dynamic response of the spindle end determines machining accuracy in the turning process. Such, the multi-mode natural frequency of the system is obtained by finite element modeling (FEM) and verified by experiments. It shows that the first several modes in the frequency range within 2000Hz are the main responses of the system, which can be effectively captured by the ORS. Especially, the modal responses are examined when the mass of workpieces decrease during the turning process and the spring stiffness is determined by FEM results. Based on the analysis, two frequency bands are advocated for ORS based online monitoring of tool wear conditions.