This Wikipedia entry provides a description of rotational moulding including history, equipment and tooling, production process, materials, typical products, design considerations, and process: advantages, limitations, and material requirements.
Rotational molding, also known as rotomolding, rotocasting or spin casting, is a molding process for creating many kinds of mostly hollow items, typically of plastic. A heated hollow mold 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.
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