The ultrasonic horn is the core component in ultrasonic-assisted micro-injection molding (UμIM). UμIM is a complex process with high temperature, high pressure, and high speed, and it is required that the ultrasonic horn should have a reliable performance to ensure the stability of its work. Therefore, the design of the ultrasonic horn is of great significance. Considering the demands for ultrasonic vibration energy in different filling directions in molding for the polymer parts with complex structures, the cubic B-spline curve transition section optimized based on orthogonal analysis is introduced into designing the stepped ultrasonic horn, and the two-dimensional ultrasonic vibration system (2D-UVS) with different resonant frequencies is constructed. The results indicate that the middle two control points of the cubic B-spline curve significantly affect the output performance of the 2D-UVS by means of constructing different cross-sectional profiles of the transition section, and showed different effects at different frequencies. In the paper, an optimal B-spline curve transition section is designed and constructed by optimizing the positions of the control points to receive a more balanced performance in terms of the desired frequency, amplification, and strength. The measurement results show that a two-dimensional ultrasonic vibration with trajectory stability of more than 95% is created from the front end of the horn, and the two-dimensional ultrasonic vibration trajectory can be controlled by different energizing voltage amplitudes and phase differences.
Keywords: B-spline curve; Flexure design; Two-dimensional vibration trajectory; Ultrasonic horn.
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