Pressure injection molding machine, has continuously-operating transfer-plasticizer advanced in casing, coupled to separate piston-cylinder injector

摘要

A single- or dual screw (7) piston-cylinder (6) plasticizer (4) is employed. Its cylindrical casing is reversibly-guided within a casing (9) enclosing a melt collection chamber (10). The latter is connected by a melt line (19), to the mold injection unit (5) comprising an injection cylinder (15) forming the injection chamber (14) containing the injection piston (16). One valve (V, V2) is located in each of the melt line and the injection line (17). Preferred features: The screw plasticizer is a compounder with two co- or counter-rotating plasticizing screws. The screw plasticizer alternatively comprises a cylinder with a single plasticizing screw. Product supply is via one or more gravimetric dosing units discharging into the screw conveying section. Rotary speed of the screw(s) and/or axial screw piston motion are adjusted such that the back pressure in the melt collection chamber (10) is both constant and greater than the pressure loss delta p in the melt line. Using the gravimetric dosing unit, product is supplied uniformly. Product comprising several components is supplied through one or more openings, into the screw cylinder threads. Ratios supplied, meet the required percentage composition, and constant back pressure Pst is maintained in the melt chamber. With only a single plasticizer screw and a non-dosed product supply, or a product drawn in from the full supply hopper by the screw, the screw rotational speed maintains constant back pressure Pst.