Rotational Molding Defined

Rotational Molding ( BrE moulding) involves a heated hollow mold which is filled with a charge or shot weight of material. It is then slowly rotated (usually around two perpendicular axes) causing the softened material to disperse and stick to the walls of the mold. In order to maintain even thickness throughout the part, the mold continues to rotate at all times during the heating phase and to avoid sagging or deformation also during the cooling phase. The process was applied to plastics in the 1940s but in the early years was little used because it was a slow process restricted to a small number of plastics. Over the past two decades, improvements in process control and developments with plastic powders have resulted in a significant increase in usage. Rotational molding, sometimes called rotomolding, is a process for creating mostly hollow, plastic items.  A calculated amount of pulverized plastic is added to a hollow mold, which is then heated and slowly rotated in at least two directions.  This causes the plastic to soften, disperse, and stick to the walls of the mold.  The mold continues to rotate throughout the heating and cooling process, after which the part is removed from the mold. Rotocasting (also known as rotacasting), by comparison, uses self-curing resins in an unheated mould, but shares slow rotational speeds in common with rotational molding. Spincasting should not be confused with either, utilizing self-curing resins or white metal in a high speed centrifugal casting machine.