Influence of Relative Transducer Positioning on Cavitation Performance in Ultrasonic Cleaning Baths

Cleaning of parts using ultrasonic cleaning baths (UCBs) is common in industrial manufacturing, especially for fields with high demands regarding the cleanliness of parts and products. However, so far, the design principles for the ultrasonic transducers and UCBs mostly remain as institutional knowledge of the manufacturers with limited publicly available resources. Therefore, the aim of this study is to identify design principles for improving the cleaning performance while reducing the power consumption and required number of transducers. A promising approach to improve these parameters is to optimize the wave interference within the UCB. Thus, aluminum foil tests were performed to compare the cavitation performance with a distance of 85 mm and 134 mm between the transducers. Further tests were performed with a movable back plate to simulate different lengths of the UCB and investigate the effects thereof on cavitation performance. Experiments using transducers with an operating frequency of 25 kHz showed that increasing the distance between transducers from 85 mm to 134 mm improved the cavitation performance, determined by total hole area, more than 6-fold despite a reduction in the amount of transducers from 35 to 23. Furthermore, positioning the movable plate at distances of integer-multiples of the wavelength increased the cavitation performance by about 80% over distances offset by half a wavelength relative to integer multiples. Overall, the results suggest that optimal transducer positioning depends on the wavelength of the ultrasound at the operating frequency and should be chosen accordingly to optimize cleaning performance and efficiency.