Plastic Injection Moulding: Containers, Buckets, Fittings and Preforms

Most plastic objects with a lid, a handle or a fitting are injection moulded. A screw melts the pellets and, moving forward like a plunger, injects the melt into a closed steel or aluminium mould; pressure is held while the part shrinks, then it cools, the mould opens and the part is ejected. The clamp must hold the mould shut against the melt: roughly 1.8 to 7.2 tonnes for every square centimetre of the part's projected area. Injection itself often takes well under a second. A benchtop moulder with an aluminium mould does the same at maker scale. Food containers need a food-grade resin.