End effectors having compaction feet for welding thermoplastic parts

A method for welding a first thermoplastic part to a second thermoplastic part via a welding head of an end effector coupled to a robot, the method comprising:

• positioning the first thermoplastic part against the second thermoplastic part;
• positioning a surface of the end effector toward the first thermoplastic part, the welding head further including a welder having a first central axis and a compaction foot having a second central axis, the welder being movable along the first central axis between a first retracted position and a first extended position relative to the surface, the compaction foot circumscribing the welder and being movable along the second central axis between a second retracted position and a second extended position relative to the surface;
• compacting a first area of the first thermoplastic part and a second area of the second thermoplastic part by moving the compaction foot from the second retracted position to the second extended position;
• moving the welder from the first retracted position to the first extended position;
• and
• welding, via a welding tip of the welder, a first portion of the first thermoplastic part located within the first area to a second portion of the second thermoplastic part located within the second area, the welding to occur while the welder is in the first extended position and the compaction foot is in the second extended position.