rotational called rotational molding is a method for manufacture of a variety of sizes and shapes of the hollow seamless product processing methods. Traditionally, it is mainly used in thermoplastic materials , in recent years , cross-linkable polyethylene rotational molding thermoset materials are also developing rapidly . As rotational higher injection pressure does not need higher shear rates or precise metering compound . Therefore, the mold together and machine are relatively inexpensive, and longer service life . Its main advantages are: the machine's performance / price is relatively high ; complex parts after molding does not require assembly ; variety of products and a variety of colors can be simultaneously molding ; die less expensive ; easy to change colors and materials ; scrap loss.

basic process is simple , the powdery or liquid polymer in the mold , heating simultaneously about two perpendicular axes , and then cooled. In the first heating stage , if using a powdered material , a porous layer formed on the surface of the mold , and with the cycle gradually melted to form a homogeneous layer of uniform thickness , if using a liquid material , the first flow and the coating in the mold surface , when it reaches the gel point is completely stopped . Then transferred to the mold cooling work area , by forced air or water cooling and then is placed in the working area , where the mold is opened , the finished parts are removed, and then during the next iteration of the loop .