1. Principles of Half-Wavelength Resonant Sonotrodes

An ultrasonic horn (sonotrode) is a tuned mechanical acoustic waveguide that vibrates longitudinally at high frequencies (typically 15kHz, 20kHz, 28kHz, or 35kHz). Its primary role is to transfer acoustic vibrational energy from the piezoelectric transducer/booster stack into the plastic workpiece with a calculated gain in amplitude.

The length of an ultrasonic horn must equal an exact half-wavelength ($\lambda / 2$) or integer multiple of the acoustic speed of sound in the selected metal:

Where $c$ is acoustic velocity in the alloy (approx. 5,100 m/s for titanium, 5,000 m/s for 7075 aluminum) and $f$ is operating frequency (e.g., 20,000 Hz).

2. Finite Element Analysis (FEA) & Acoustic Slotting

When an ultrasonic horn exceeds a width of approximately 80–90 mm at 20kHz, Poisson's ratio induces severe lateral transverse vibrations. These unwanted secondary modes cause non-uniform face amplitude (dead spots), rapid acoustic overheating, and premature fatigue cracking.

UltraLanank engineers conduct 3D ANSYS modal simulations to isolate the fundamental longitudinal mode at least 1,000 Hz away from nearest flexural or torsional modes. We integrate precision EDM-cut acoustic slots that isolate vertical acoustic columns, delivering uniform amplitude across wide bar horns up to 350 mm in length.

3. Horn Metallurgy: Titanium vs. Aluminum vs. Steel

4. Custom Horn Tooling & Equipment

• Custom Ultrasonic Horns, Sonotrodes & CNC Nest Fixtures: Custom-engineered in Zhaoqing with FEA simulation and laser vibrometer tuning.
• Explore our full range of Industrial Ultrasonic Plastic Welding Systems.

5. Acoustic Tooling Technical FAQ