| Vibration characteristics of a high-speed spindle and Dual-Spindle High-Speed Drilling Machine Head were studied to determine if the modal, free-run, and cutting characteristics allow for a stable machining system at the required operating speed of 167 Hz (10 000 RPM). A finite element analysis of the high-speed spindle model was conducted to determine the validity of the finite element method in modeling the bearing support structure of the spindle-bearing assembly.;The finite element analysis under simply applied boundary conditions does not provide valid results in terms of the displacement shape and the natural frequency of the spindle-bearing support structure. A detailed understanding of the structure's boundary interactions is required to correctly model such an assembly. Because of its scope, this problem was separated for future work.;Modal analysis indicates that the lowest natural frequency of the spindle assemblies occurs at 712 Hz (43 200 RPM). This value is beyond the required operating speed of 167 Hz (10 000 RPM), and with only two cutting edges on the drill bit, vibration problems during cutting were not expected.;Free-run characteristics indicate a fairly stable system with low vibration, and bearing thermal levels. Run-up and run-down tests were carried out at speeds up to 267 Hz (16 000 RPM).;Vibration levels during metal cutting with two different diameter drills were only slightly higher than those at the free run tests. There was no indication of any tendency to produce chatter or any other form of excessive vibration.;The vibration analysis of the dual-spindle high-speed drilling machine head demonstrates that the system is capable of operating under the required working parameters. |
