Rotational moulding, known also as Roto moulding or Roto casting, is a process for manufacturing hollow plastic products.   Rotational moulding is best known for the manufacture of tanks but it can also be used to make complex medical products, toys, leisure craft, and highly aesthetic point-of-dale products.   The process begins with specially developed and uniquely applied resins. They can include plastisols, polyethylene, polycarbonate, elastomers, polyurethane, polypropylene.   The principle of rotational moulding of plastics is simple. Basically the process consists of introducing a known amount of plastic in powder, granular, or viscous liquid form into a hollow, shell-like mould. The mould is rotated about two principal axes at relatively low speeds as it is heated so that the plastic enclosed in the mould adheres to and forms a monolithic layer against the mould surface. The mould rotation continues during the cooling phase so that the plastic retains its desired shape as it solidifies. When the plastic is sufficiently rigid, the cooling and mould rotation is stopped to allow the removal of the plastic product from the mould.   The main advantages of rotational moulding are:   A hollow part can be made in one piece with no weld lines or joints The end product is essentially stress-free The lead time for the manufacture of a mould is relatively short Short production can be economically viable There is no material wastage in that the full charge of charge of material is normally consumed in making the part It is possible to make multilayer products Different types of product can be moulded together on the one machine Inserts are relatively easy to mould into product High quality graphics can be moulded into product