The rotational moulding process can be used to mould hollow items, but this does not mean that by the term “hollow item” it is intended to have a large hollow internal volume. It is, in fact, possible to mould “hollow items” that have two walls very close to each other which form a
part that has both the external section and the internal section produced by the mould surface.
Moulds that permit the moulding of a double wall part can be designed with a “core” that defines the inner part.
The distance between the two parallel walls may be relatively small, which makes the parts suitable as isolators for example. In this case, to give the powder the space needed to flow inside the mould, it is necessary to design the two walls with an adequate separation gap.