Injection molding of vehicle bodywork, avoiding surface defects

摘要

Initially, a first end region (A) of the mold is filled, then a second adjacent region (B), and so on by stages, until the final region (C) is reached at the opposite end of the mold. An Independent claim is included for the mold used. Its mold cavity has cold filling channels, with valve plugs across and blocking them. Independent claims are also given for the plastic molding obtained, especially a vehicle wing or door panel. Preferred features: The plastic is a type which must be injected at over 290 deg C. The mold has several cold channels conveying plastic into the mold cavity. These are blocked initially, and then sequentially opened to inject plastic into each successive region. Having opened each cold channel, it is closed individually before opening the next in sequence. All channels are opened to compact the plastic, keeping it under pressure during cooling. The cold channels are each closed by a tube moving axially in a bore across and blocking the cold channel. The tube also ejects the plastic sprue (6) arising from the cold channels, when the molding is removed.