Method and apparatus for injection moulding plastics material

摘要

The invention provides a method and apparatus for injection moulding a plastics article having thin and thick wall sections (14; 15). A quantity of molten plastics material (19) is introduced sufficient to fill the mould cavity, followed by a further quantity of molten plastics material sufficient to pack at least the portion or portions of the mould cavity in which the thin wall section or sections (14) are formed. Pressurized fluid is introduced through the or each fluid injection member to penetrate the plastics material whereby a fluid-filled void (20) is formed within the plastics material adjacent to the inner end of the fluid injecting member, and fluid pressure is maintained within the or each void so that the void expands in response to the shrinkage of the immediately surrounding plastics material, during cooling, until the plastics material is self-supporting.