An apparatus (21, 221, 231) for forming a butt seam (33, 233, 354) between opposed edges (32, 33, 231, 232) of resiliently compressible, fully cured, elastomeric, fabric sheets (28, 29, 228, 229, 351, 352), such as foamed
neoprene for wet suits and dry suits. In some embodiments (21, 221) the apparatus includes fabric manipulating
assembly (23, 223) which continuously compresses the sheets
proximate and inwardly of the edges, preferably by a roller
assembly (26, 27, 226, 227), to firmly press the opposed edges of the flexible and compressible sheets (28, 29, 228, 229) tightly together during movement and bonding along the seam (33, 233). The apparatus (21, 221, 331) preferably includes
adhesive activation device in the form of an ultrasonic
transducer (24, 222, 322) which contacts the
neoprene pieces to activate a dry
neoprene cement carried on the edges of the fabric pieces. Embodiments (221, 321) are shown which include a force applying
assembly (224, 324) that hammers the foam pieces against the ultrasonic
transducer horn (222), or the horn (322) against the foam pieces, to enhance sonic
energy coupling and to simultaneously press the pieces together for improved
adhesive bonding. A method for forming the butt seam (33, 233, 354) is described.