| 摘要 |
There are shallow protuberance(s) (9) on the wall (7) of the moulding cavity (2), each with its outer surface (10) running parallel to the mould wall. Pressurised fluid, preferably gas, is introduced by a special injector (6) near the outer surface, to form a gas cushion (8) between plastic and this surface. An Independent claim is included for the corresponding equipment to carry out the process. Preferred features: The sides (11) of the projection are tempered, locally modifying setting behavior of the plastic. They are heated and/or cooled (12) for predetermined intervals. The melt is injected under pressure, before forming the gas cushion. The cavity is completely filled under such a pressure, that during the first phase of setting, the plastic is in a state of pre-pressurisation. The gas injection pressure is a function of: pressure in the cavity, and/or time since start of injection, and/or the displacement of the injection screw. It may be controlled as time elapses, in accordance with a predetermined profile. |
