Abstract
The connection characteristics of HSK tool holder-spindle system have great influences on machining precision and security of computer numerical control machine tools. In order to predict dynamic behaviors and avoid connection failure of HSK tool holder-spindle system, a nominal radial stiffness prediction model for HSK tool holder-spindle flange interface is constructed. Contact stress of spindle and HSK tool holder can be obtained by considering actual interference and actual clamping force. Considering elastic contact deformation, the plastic contact deformation, and two different regimes of elastoplastic contact deformation, a fractal model of nominal contact stiffness of HSK tool holder-spindle flange interface is proposed. In order to prove the rationality of the model, the tests are validated by a self-designed equipment. The effects of different parameters to the maximal permissible rotational speed, critical bending moment, and nominal radial stiffness of HSK tool holder-spindle connection system are researched. The results can be used as an instruction for the application of HSK tool holder and optimization of geometry parameters.
Highlights
The tool holder-spindle system is an important component in computer numerical control (CNC) tools, and the dynamic characteristics of the system have great influences on the dynamic behaviors of the entire system
The clamping force has a great influence on the increase of the critical bending moment; this is because the contact stress of the flange surface increase with the increase of the clamping preload
In order to meet the requirement of the maximal permissible rotational speed, critical bending moment, and high nominal stiffness for HSK tool holder, clamping preload and interference should be designed synchronously according to the working condition
Summary
The tool holder-spindle system is an important component in computer numerical control (CNC) tools, and the dynamic characteristics of the system have great influences on the dynamic behaviors of the entire system. This article presents a nominal stiffness prediction model for the HSK tool holder-spindle flange interface considering fractal multi-scale contact properties. According to the elastic mechanics theory[20] and equations (2)–(4), the contact stress due to the actual interference between the taper surface of HSK tool holder and spindle is written as ÁÀ sinterference =. The nominal radial contact stiffness of the HSK tool holder-spindle flange interface can be determined by solving the above equations. In order to ensure the contact of the flange interface, the clamping preload should be increased This results in the taper interface stress becoming larger, which decreases the service life of the HSK tool holder. The clamping force has a great influence on the increase of the critical bending moment; this is because the contact stress of the flange surface increase with the increase of the clamping preload. Under light-bending moment conditions, increasing the clamping force has a limited effect on increasing the nominal stiffness
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