Tool Chucking Mechanism with Insensitiveness to Centrifugal Force for Ultra High-speed Spindle

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In order to improve accuracy and efficiency, the development of high-speed machining is demanded strongly. To achieve this demand, it is essential to develop the high-performance tool-chucking mechanism applicable to high-speed spindle. Under the high-speed rotation, accuracy and stiffness drop worse because of effect of large centrifugal force on the connection between the tool and spindle. To solve this problem, various types of double-face contact tool-interface are developing actively. By using those interfaces, the allowable rotational speed becomes higher. However, there is still the limit of the rotational speed possible to use those interfaces, and this limitation is one of the essential obstructions for speed-up of spindle in the future. In this study, to solve this problem essentially, the novel tool chucking mechanisms, which make use of the centrifugal force in order to strengthen the tool chucking force, is proposed. At first, the basic specification needed for the mechani … More sm is determined. And then, the basic model of the mechanism is designed, and its tool-chucking characteristics are examined with finite element method. Furthermore, the test model is actually made in order to measure the tool chucking performance. As the result, it is found out to be difficult to obtain enough tool-chucking torque, since the tolerances of the components are too severe to machine practically. Then the structure of the mechanism is simplified drastically and becomes insensitive to dimensional error of components. In addition, by incorporating the tool-stopper for locating tools and the guide mechanism for wedge movement, the performance of chucking action is improved. Finally, the characteristics of improved model are evaluated with theoretical analysis and finite element method, and then, followings are confirmed : the tool chucking force can be magnified more than ten times as strong as the drawing force. The mechanism provides almost same torque as conventional tool-chucks such as collet chucks. By action of the centrifugal force, the tool chucking force under the spindle rotation of 10,000min-1 becomes 18% larger than that under standstill. From above mentioned results, it can be said that the developed tool-chucking mechanism is applicable to ultra-high speed spindle. Less