Surface quality improvement under low-frequency and high-amplitude vibration in rotational vibration-assisted incremental sheet forming

Rotational Vibration-assisted Incremental Sheet Forming (RV-ISF) is a newly developed process variant that aims to improve upon conventional Incremental Sheet Forming (ISF), by the introduction of tool rotation-induced low-frequency and high-amplitude vibrations of deforming sheet. Different to existing ultrasonic vibration-assisted ISF processes with high-frequency and low-amplitude, the RV-ISF process introduces localised sheet vibrations under frequency typically below 300 Hz and amplitude from 5 to 100 µm. In this paper, an experimental study of the RV-ISF tool rotation-induced sheet vibrations on surface roughness reduction is presented. A trapezium test geometry using a helical toolpath is made by conventional ISF and RV-ISF processes with AA5251-H22 1 mm thickness sheets. Tool forming forces are measured by a piezoelectric force transducer and sheet vibrations are obtained by an Eddy current sensor. Optical measurements of surface roughness show that the RV-ISF tool is capable of reducing roughness of the sheet significantly and consistently across the entire sidewall of the trapezium samples, with a Ra reduction of up to 80% when compared to the conventional ISF tool.