A high-frequency non-resonant elliptical vibration-assisted cutting device for diamond turning microstructured surfaces

Abstract In recent years, research has begun to focus on the development of non-resonant elliptical vibration-assisted cutting (EVC) devices, because this technique offers good flexibility in manufacturing a wide range of periodic microstructures with different wavelengths and heights. However, existing non-resonant EVC devices for diamond turning can only operate at relatively low frequencies, which limits their machining efficiencies and attainable microstructures. This paper concerns the design and performance analysis of a non-resonant EVC device to overcome the challenge of low operational frequency. The structural design of the non-resonant EVC device was proposed, adopting the leaf spring flexure hinge (LSFH) and notch hinge prismatic joint (NHPJ) to mitigate the cross-axis coupling of the reciprocating displacements of the diamond tool and to combine them into an elliptical trajectory. Finite element analysis (FEA) using the mapped meshing method was performed to assist the determination of the key dimensional parameters of the flexure hinges in achieving high operational frequency while considering the cross-axis coupling and modal characteristics. The impact of the thickness of the LSFH on the sequence of the vibrational mode shape for the non-resonant EVC device was also quantitatively revealed in this study. Moreover, a reduction in the thickness of the LSFH can reduce the natural frequency of the non-resonant EVC device, thereby influencing the upper limit of its operational frequency. It was also found that a decrease in the neck thickness of the NHPJ can reduce the coupling ratio. Experimental tests were conducted to systematically evaluate the heat generation, cross-axis coupling, modal characteristics and diamond tool’s elliptical trajectory of a prototype of the designed device. The test results showed that it could operate at a high frequency of up to 5 kHz. The cross-axis coupling ratio and heat generation of the prototype are both at an acceptable level. The machining flexibility and accuracy of the device in generating microstructures of different wavelengths and heights through tuning operational frequency and input voltage have also been demonstrated via manufacturing the micro-dimple arrays and two-tier microstructured surfaces. High-precision microstructures were obtained with 1.26% and 10.67% machining errors in wavelength and height, respectively.