Injection mould for Lego bricks, 1988.
© Science Museum / Science & Society Picture Library
As Lego shapes are complex, casting is the easiest way of producing them. They are injection moulded using a type of plastic called ABS (acrylonitrile butadiene styrene) which is melted and injected into the mould by a hydraulic plunger. This has a force equivalent to 700 bags of sugar balanced on the end of your finger and a single mould can produce 2880 Lego blocks an hour. Made by the Lego Group.