Rotational molding, sometimes called "rotomolding", is a process for the creation of large, hollow, one-piece parts of
unusual shapes. It is a low pressure process and compared to plastic parts produced by other
processes, the parts have relatively lower levels of molded-in stress which improves
impact strength and chemical resistance.
The process consists of charging a hollow, closed mold with a plastic material in a liquid or
powder form. The mold is then continuously rotated around its vertical and horizontal axes in
an oven where the mold, and therefore the plastic, is heated to fusion temperature. The still
rotating mold is then removed from heat to allow the part to solidify so that it will retain the
shape of the mold. The mold is opened and the part removed. The mold is recharged
and the process begins again.
Rotational molding should not be confused with centifugal casting, which throws the plastic
material out to the sides of the cavity. In rotational molding process the mold is heated
and the plastic material builds up on the inside surface of the cavity as the mold rotates
and the sides continually come into contact with the puddle of plastic material at the
bottom portion of the mold.