Rotational molding [1] is one of the most important polymer processing methods for producing
hollow plastic articles. In this process, plastic powder is placed in one half of a mold. The mold is then closed and subjected to biaxial rotation in an oven at a temperature of 200–400 1C. The plastic powder inside the mold is melted [2–4] by heat transferred through the mold wall. When all the powder has melted, the mold is moved out of the oven while maintaining the biaxial rotation. Still air, a fan or a water shower is usually used to cool the mold. Once the product inside the mold is cooled to a state of sufficient rigidity, which in most cases occurs when all regions of the part have cooled to below the melting temperatures of the polymers, the mold opens and the product is removed [5–7]. Fig. 1