Performance evaluation of a shape memory alloy tool holder for high-speed machining

With recent increases in demand for small products such as mobile devices and artificial teeth, there is a growing need for small precision machine tools. The tool holder is one of the key enabling technologies for small precision machine components. Increases in the rotational speed require reduced inertia. Collet chucks and hydraulic chucks have been proposed as tool holders for micromachining; however, they are limited in scope for miniaturization because of the complexity of their components. Here, this paper reports a tool holder formed of a shape memory alloy (SMA). This holder does not require a collet and can be used with small changes in temperature. However, a design process for SMA holders has not yet been established. Here, this paper proposes a simplified equation describing the behavior of the tool holder and verifies the results of this equation experimentally. First, a description of the behavior of the SMA ring is given. The SMA tool-clamping device is defined with a simple shape and described using a mathematical model. The magnitude of the deflection of the SMA tool holder is then calculated using the mathematical model. Finally, the simulation results are verified by measuring the deflection of the holder. Using the model described here, it is possible to design SMA tool holders with various radii.