Automated ultrasonic press systems and methods for welding physically variant components

An ultrasonic welding method for welding a pair of workpieces having different physical characteristics, including workpieces that have differing materials or differing geometric properties, the method comprising:

• pressing an ultrasonic welding stack against a first workpiece in the pair of workpieces, wherein the first workpiece includes an energy director that comes into contact with a second workpiece in the pair of workpieces in response to the pressing;
• initiating a weld phase by outputting energy from the ultrasonic welding stack to the first workpiece;
• monitoring, with at least one sensor, a weld force;
• determining whether the weld force has reached a predetermined level;
• ending the weld phase by ending outputting energy from the ultrasonic welding stack to the first workpiece, before reaching a full length of energy director;
• and
• initiating a hold phase and continuing to press the ultrasonic welding stack against the first workpiece,
• wherein the first workpiece and the second workpiece comprise different physical characteristics, and
• wherein the ending outputting energy from the ultrasonic welding stack to the first workpiece is based on determining that the weld force has reached a predetermined level.