Method for manufacturing of shell shaped articles or hollow bodies from a thermoplastic material

摘要

A length of extruded tubular preform (2) is produced and divided to form at least a single strip of material (2a,2b). The strip is gripped by segments (6) of a manipulator, removed from the die(1) and spread out transverse to the extrusion direction and/or stretched. In this condition the strip is transferred to a molding tool for production of the desired product. A length of extruded tubular preform (2) is produced and divided to form at least a single strip of material (2a,2b). The strip is gripped by segments (6) of a manipulator, removed from the die (1) and spread out transverse to the extrusion direction and/or stretched. In this condition the strip is transferred to a molding tool for production of the desired product. Tubular preforms are extruded to hang freely downwards. Thin circumferential line are produced at prescribed spacing during the extrusion stage allowing the material strip to be torn away from the die by the manipulator. The preform is axially divided at one or more points around the circumference either inside the die or outside by a cutter below the die. When preform division occurs inside the die thin strips of a thermoplastic dividing material are used, which do not melt, weld or bond to the preform material and hence ensure cut lines do not rejoin. The wall thickness of the preform may vary over the length and/or circumference.