Injection moulding hollow articles - by inserting baffles at suitable points in cavity to deflect polymer shot and finally produce thicker wall when gas is melt injected

摘要

A hollow moulding is produced, using a cavity with at least one dam near one surface. In the process material is injected into at least part of the cavity and a gas is next injected to produce a hollow part between the dam and a second surface; a solid part is then formed between the dam and the first surface, after which the hollow moulding is ejected. The shot is pref. polypropylene and the gas nitrogen. To produce a hollow handle for a car interior the mould cavity has two internal dams in the flow paths of injected gas and near the gate before the curved area. The dams are at about 1/3 the height of the cavity and stand out of one wall, and are 3 mm thick. The gas used is injected at 200 kg/cm2. ADVANTAGE - The method makes it possible to produce hollow mouldings with a thick part of the outer skin