Quasi-real-time monitoring of variable milling parameters during multi-axis machining

The milling parameters under complex machining conditions have strong time-varying characteristics. Their accurate acquisition is an important foundation for analyzing the cutting mechanics and dynamics. The traditional methods usually perform an off-line calculation on them, resulting in difficulty for real-time monitoring of machining process. Therefore, the paper proposes a quasi-real-time monitoring method for variable milling parameters during multi-axis machining. By replacing the local cut-off allowance of workpiece with a tool entity set at past neighboring cutter location points (PNCLPs), a fast calculation for cutter-workpiece engagement (CWE) entities is achieved through the Boolean operations among the current tool, workpiece blank, and past tool entity set. Then, a 2-dimensional (2D) image processing is used to obtain the CWE window function. For the curved tool path in multi-axis machining, the spatial feed motion of tool is decomposed based on the trochoid motion of tooth side and bottom cutting edges, and an analytical expression of the instantaneous undeformed chip thickness (IUCT) is derived subsequently. During the actual machining process, a self-developed monitoring system is utilized to collect the internal command data of CNC system, further drive the CWE Boolean operation and IUCT calculation model, and obtain the strongly variable milling parameters promptly. Finally, the validity of the proposed method is verified through three-axis and five-axis milling experiments. The maximum average single-step monitoring time is 3.77s. The timely monitoring of milling force can accurately reflect the changing trend of its actual values. The study results indicate that the proposed method can successfully achieve an accurate and real-time monitoring of variable milling parameters during multi-axis milling process.