Probably referring to polymer ultrasonic welding, or less likely polymer thermal bonding. From experience I can tell you that ultrasonic welding is relatively complex in that it generally requires a shoe on the upper and lower side of the two pieces of fabric, correct pressure, correct ultrasonic frequency, and either (A) both pieces need to be held steady and the head must move; or (B) vice versa. It's not a process that is easy to replicate for complex geometries or novel materials and applications without significant preparation, jigs and fixtures. This is in direct contrast to cutting or marking where a head can simply glide over a flat material and effect a two dimensional geometry. https://en.wikipedia.org/wiki/Ultrasonic_welding
