The occurrence of chatter vibrations in 5-axis milling processes is a common problem and can result in part failure, surface defects and increased wear of the cutting tool and the machine tool. In order to prevent process vibrations, machining processes can be optimized by utilizing geometric physically-based simulation systems. Since the modal parameters of the machine tool are dependent on the position of the linear and rotary axes, the dynamic behavior of milling processes can change along the NC path despite constant engagement conditions. In order to model the pose-dependent modal properties at the tool tip, the frequency response functions (FRFs) were measured at different locations of the workspace of the machine tool for various poses of the rotary axis of the spindle. To take the varying compliance within the workspace of a machine tool into account in a geometric physically-based milling process simulation, different interpolation methods for interpolating FRFs or parameter values of oscillator-based compliance models (OPV) were applied. For validation, the resulting models were analyzed and compared to measured data. In OPV interpolation, the individual oscillation modes were interpolated in their respective characteristics based on the oscillator parameters (eigenfrequencies, modal masses and damping values). In FRF interpolation, however, there was no differentiation between the modes, resulting in a wrong interpolation. It can therefore provide good results when only a small shift of the eigenfrequencies is expected, as in case of the analyzed machine tool, with only small movements of the translatory axes.
The machining of free-formed surfaces, e.g., dies or moulds, is often affected by tool vibrations, which can affect the quality of the workpiece surface. Furthermore, in 5-axis milling, the dynamic properties of the system consisting of the tool, spindle and machine tool can vary depending on the tool pose. In this paper, a simulation-based methodology for optimising the tool orientation, i.e., tilt and lead angle of simultaneous 5-axis milling processes, is presented. For this purpose, a path finding algorithm was used to identify process configurations, that minimise tool vibrations based on pre-calculated simulation results, which were organised using graph theory. In addition, the acceleration behaviour of the feed drives, which limits the ability of adjusting the tool orientation with a high adaption frequency, as well as potential collisions of the tool, tool chuck and spindle with the workpiece were considered during the optimisation procedure.
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