In rotational molding, a ground plastic powder is heated in a rotating mold until it becomes molten. As the mold rotates, the molten plastic uniformly coats the inside of the mold cavity. When it is cooled, a hollow finished part is formed.

Several molds may be placed on the machine at the same time. Pre-measured plastic resin is loaded into each mold, and then the molds are moved into the oven where they are slowly rotated on both the vertical and horizontal axis. The melting resin sticks to the hot mold and coats every surface evenly.

The mold continues to rotate during the cooling cycle so the parts retain an even wall thickness. Once the parts are cooled, they are released from the mold. The rotational speed, heating and cooling times are all controlled throughout the process.

One of the most cost-effective molding methods, rotational molding can be used to produce complex parts that have features such as intricate contours, undercuts, molded-in inserts and double walls.

Rotational molded plastics are used in virtually any industry that requires the use of plastic parts. Common parts that are typically rotationally molded include specialty tanks and containers for water and chemical processing, and many recreational applications such as kayaks and boats, playground equipment and childcare seats.

Rotomolding is a good, general purpose molding technique for hollow plastic parts. Designs can be more demanding than in some other processes. Sharper corners, more controllable wall thicknesses, thicker corners, and with multi-section molds, backlocks and difficult geometry can be accommodated.

The longer cycle times are more conducive to smaller production quantities, while the tooling price is less than other processes. Material selection is ever-widening with today's formulations.

Rotational molding delivers the product the designer envisions. Designers can select the best material for their application, including materials that meet FDA requirements. Additives to help make the part weather resistant, flame retardant, or static free can be specified.