Ultrasonic welding systems and methods using dual, synchronized horns on opposite sides of parts to be joined

An ultrasonic welding system for sealing together multiple layers of a part, the system comprising:

• a first ultrasonic welding stack including a first horn and a second ultrasonic stack including a second horn, the first horn having a first welding surface, the second horn having a second welding surface opposing the first welding surface to define a gap therebetween, wherein the gap is configured to receive therein the part to be sealed along a section of the part;
• an actuator assembly operatively coupled to the first and second ultrasonic welding stacks and configured to cause the first welding surface to move relative to the second welding surface;
• one or more controllers operatively coupled to the first and second ultrasonic welding stacks and to the actuator assembly, the one or more controllers operatively being configured to:
• cause the actuator assembly to urge the first and second welding surfaces of the first and second horns toward one another until contacting the part, and thereby apply toward the part a first ultrasonic energy via the first horn and a second ultrasonic energy via the second horn such that a frequency and a phase of the first and second ultrasonic energies are synchronized as the first and second ultrasonic energies are applied on both sides of the part simultaneously, to thereby the seal the part along the section.