| 摘要 |
Apparatus for injection moulding comprises two mould parts (1 and 2) defining a mould cavity. The cavity comprises a planar section (3) having pairs of parallel elongate ribs (4) disposed at intervals on one side of the section (3) and the central pair of ribs defines an elongate area (5) closed off at opposite ends by further ribs (6 and 7) thus producing two confined areas. Gas is fed to each via gas channel (8) each of which leads to a porous metal insert (9) on the surface of the mould cavity. Synthetic plastics material is fed to the mould cavity via a sprue and connected runners. During the moulding process after the injection and cooling of plastics material, gas is fed under pressure to the mould cavity via gas channel (8). This permits plastic in those areas to be pressurised and displaces plastics material to compensate for volumetric shrinkage of the plastics adjacent those areas. This in turn avoids sink marks. |
