Organization / Terms / rotational mold

What is rotational mold Rotational molding, or rotomolding, is a cost-effective way to produce large parts. Plastic resins are loaded into a mold that is heated as it is rotated slowly on both the vertical and the horizontal axis. This simultaneous heating and rotation distributes the material on the inner surfaces of the mold and fuses it. Rotational mold is a four-phase process, which comprises loading, heating, cooling, and unloading the mold. In the first stage the pre-measured plastic resin is loaded into the mold. (Polyethylenes and plastisols are the most common of the many materials used in rotomolding resins.) Several molds may be loaded on a given machine at the same time.

The charged molds are then closed and moved into the oven, where they slowly rotate on two axes. As the heat penetrates the molds, the melting resin adheres to the mold’s inner surface until it is thoroughly fused, evenly coating the entire surface. During the cooling phase, the mold continues to be rotated to maintain even walls as air, water spray, or a combination of the two gradually cools the mold. The mold is then opened, the finished part removed, and the mold is ready for its next cycle. Rotational mold benefits Unlike other plastic rotational mold processes, rotomolding results in seamless parts with uniform wall thickness and more material in corners, to absorb shocks and stresses where they occur most. Since the material isn’t stressed during production as in thermoforming or pressure forming, the finished part is stronger.

Plus, the molds don’t need to be designed to withstand the high pressures of injection molding. Since the mold has no internal core to manufacture, tooling costs are lower in that regard as well – and minor changes can be easily made to existing rotational mold.