| Vibration control is a critical function of the bar feeders which are used to automatically feed stock to high-volume computer-numeric-controlled turning operations. Current technology employs continuous rigid support along the length of the bar; however, the need to quickly load fresh bar stock and change between stock sizes makes the physical implementation cumbersome, which in turn introduces process challenges. Specifically, each different stock diameter requires a specially matched guide channel, introducing a significant amount of changeover time between jobs as well as a significant capital investment. This research investigates how the rheology of a single discrete support might be tuned to affect the dynamics of the bar, providing comparable vibration control without these disadvantages. The bar stock is modeled as a Bernoulli-Euler beam, and a method of predicting the natural frequencies with a general viscoelastic support is developed. Magnetorheological fluids in direct contact with the bar are evaluated as an alternative for implanting the variable-rheology support. Theoretical and experimental results are presented, and a control algorithm is proposed. Finally, the viscoelastically supported beam model is used to explore how various support configurations, without regard to their physical manifestation, may be located and tuned to avoid resonant vibration in beams. |
