Design and simulation of a large tubular horn for ultrasonic plastic welding

Abstract

Designing large horns for ultrasonic systems is usually very complex as it involves delivering the specified longitudinal mode at the operating frequency with uniform displacement amplitude at the face of the horn. Large horns are usually designed with slots parallel to the longitudinal motion to control the modal characteristics. The position and dimensions of the slots are critical in achieving the desired longitudinal mode with uniform amplitude at the horn face. Innumerable design iterations followed by analysis are required to achieve this objective. The present study uses design of experiments to optimise the position and size of the slots with minimum design and analysis effort. The response variables studied are the natural frequency, displacement amplitude and von Mises stress of different horn designs found using modal and harmonic analysis by finite element analysis (FEA). The results of the dynamic analysis are used to form regression equations. The optimum design parameters are arrived at based on the regression equation and the plots of main effects of the slot parameters. A horn fabricated using this design was successfully tuned and tested in the industry.