Preform extruder produces variable thickness profiled thermoplastic tube for blow moulding

摘要

This unit profiles the wall thickness of plastic tubes produced by continuous or batch extruders, for further processing into end products. At the feed screw (1) outlet, is a tool, its body (43) enclosing the sliding mandrel (23) with upper spring loading. A novel annular nozzle of variable width is formed between the conical foot of the mandrel and the outlet (43). There is a melt space between mandrel and heated (18) body with temperature sensor (19). Nozzle width (29) corresponds to the wall thickness extruded (31), and is adjusted indirectly, as a function of melt pressure and spring constant, through the drive motor (10) and feed screw (1). The nozzle width variations determine the profile history of extrudate thickness.