Injection moulding thick thermoplastic sections in thin walled stages - using ribbed cavity inserts and successive over-moulding

摘要

Large components are injection moulded in stages using two or more moulds successively with inserts which subdivide the mould form into segments comprised of complementary thin-walled sub-components. Moulding of a gear leverl knob in two or three stages is illustrated. Used for moulding thermoplastic forms into shapes which would distort or rupture (internally) due to differential cooling and shrinkage if moulded as a thick section. The thin moulding sections may be cooled relatively efficiently, e.g. due to conduction to adjacent tool faces, so that the cumulative moulding cycle is shorter than that required for a thick one-piece moulding to become stable.