Machining of Aluminium with MHz High-Intensity Focused Ultrasound

Cavitation-induced surface erosion has been studied for decades. High-intensity focused ultrasound (HIFU) enables localized erosion, with applications in many fields. However, no research has been published on machining solely with HIFU. Compared to existing micro-machining technologies, HIFU exhibits a unique set of benefits: inexpensive, minimal maintenance due to non-contact machining without slurry, mitigated chemical load, and monitoring capability. We demonstrate controlled surface machining of mirror-polished aluminium (AW-5754) using high-frequency (12 MHz) HIFU-induced cavitation erosion. Optimal sonication parameters (transducer-sample distance, amplitude, cycles per burst, number of bursts, and pulse repetition frequency) for stationary surface erosion were first identified experimentally. These parameters served as a basis for studying the effect of sonication parameters during on-the-fly erosion, i.e., engraving lines. The effect of stage translation velocity and the number of repeated passes across the engraved line were also studied. Subsequently, the acronym of our laboratory, “ETLA”, was engraved, with a 500 µm letter height and an average line width of 53 µm.