A seamless elastic strap with forked structures and a manufacturing method thereof are provided, the elastic strap includes an upper layer fabric strap formed by interweaving an upper layer warp, an upper layer wrapped warp, and an upper layer weft and a lower layer fabric strap formed by interweaving a lower layer warp, a lower layer wrapped warp, and a lower layer weft. By changing the interweaving position of the upper and lower wrapped warps with the upper and lower wefts, a structure consisting of several forking parts and merging parts arranged at intervals on one elastic strap is achieved. It uses the staggered hot-cutting method to make the ends of both ends of the upper and lower fabric straps misaligned. It uses the ultrasonic welding method to form a loop fabric strap. It has the advantage of using adhesive pressing or ultrasonic welding to make seamless marks.

Provided is a thermal molding method for producing a thermally molded article having excellent abrasion resistance at its melt-fused part. Polyamide 6 and a copolyester are prepared separately. The copolyester contains terephthalic acid, ethylene glycol, and 1,4-butanediol as copolymerization units. The copolyester may further contain -caprolactone and/or diethylene glycol as a copolymerization unit. A multifilament yarn in which core-sheath type composite filaments each containing a core component and a sheath component at a ratio of 1 to 4:1 by mass are bundled is produced by a composite melt-spinning method using the polyamide 6 as the core component and the copolyester as the sheath component. Using the multifilament yarn, a product of filaments is produced by weaving, knitting, knitting and braiding, or braiding. The product of filaments is heated to melt the copolyester and fuse the core-sheath type composite filaments to each other while retaining the initial filament form of the polyamide 6, thus thermally molding the product of filaments.

A joining method using heat fusion includes layering a first joining body and a second joining body having a smaller plane area than the first joining body; and performing heating and pressurization with a heater from a side of the second joining body. The method further includes a resin dam interposed between the second joining body and the heater. The resin dam includes a base body having one of front and back surfaces in contact with the heater and the other of front and back surfaces in contact with the second joining body; and a dam main body extending from a circumferential edge of the base body in a direction away from the base body and having a shape control surface facing a side surface of the second joining body.

The objective of the present invention is to provide a vehicle door trim bonding device capable of quickly bonding sub-trims. In order to achieve the objective, the present invention provides a vehicle door trim bonding device for coupling a first sub-trim in which a projection is formed and which is made of a thermoplastic resin material, and a second sub-trim in which a receiving hole for receiving the projection of the first sub-trim is formed and which is made of a thermoplastic resin material, the device comprising: a heat supply unit for melting a part of the protrusion with radiation heat; and a molding part for compression-molding the molten protrusion.