The process of roto-molding, also known as rotational molding, allows for the production of large hollow parts or components in virtually any size or shape. In this technique, plastic resins are carefully poured into the open cavity of a two or more part mold. The selection and quantity of resin are determined by the part's predefined "recipe," considering factors such as desired wall thickness and other specific characteristics. The mold is then securely closed and tightly sealed. Attached to one of the arms of the rotational molding machine, the mold or tool undergoes a series of stages.
The rotational molding machine follows a three-stage process, which includes loading and unloading, high-temperature gas ovens, and a cooling station. Once the open mold is loaded and closed, the machine's arm positions it inside the gas oven. Through the movement of the arm, the mold begins rotating, utilizing centrifugal force to melt and uniformly distribute the resin within the mold, ensuring an even coating throughout, even in intricate corners. The rotation of the mold typically continues for a specific duration specified in the recipe, ranging from 90 seconds to a few minutes. Subsequently, the molds are transferred to the cooling chamber, still spinning, and cooled using either cold water or air. The rotomolding process reaches completion when the mold is returned to the worker's platform, opened, and the finished part is carefully removed. The mold is then refilled, closed, securely bolted, and prepared for another cycle.
It's important to note that parts produced through the rotomolding process exhibit a visible seam where the two or more sides of the mold meet. A well-designed part will strategically conceal or position the seam in non-critical or inconspicuous areas. Rotationally molded parts find extensive use in applications requiring air or water tightness, such as flotation devices, tanks, rain barrels, road barriers, and more.
