Rotational molding, or more commonly called rotomolding, is an economical way to produce large parts. Different types of plastic such as polyethylene, PVC, nylon, and polypropylene, are broken down into a usable resin. This plastic resin is then loaded into a mold that is combination heated and rotated in a slow, yet constant motion. This simultaneous process of heating and rotation distributes the material on the inner surfaces of the mold and combines it together.
Rotomolding is a four-step process, made up of Loading, Heating, Cooling, and Unloading the mold. In the Loading stage the pre-measured plastic resin is loaded into the mold. The filled molds are then closed and moved into the oven, where they slowly rotate on two axes. As the heat penetrates into 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 stage, the mold continues to be rotated to maintain even walls as a high velocity air current gradually cools the mold. The mold is then opened, the finished part removed, and the mold is ready for its next step. Unlike other plastic molding processes, rotomolding produces seamless parts with consistent wall thickness and more material in corners. This is in order to absorb shocks and stresses where they are most likely to occur.