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Rotational molding is the method by which many plastics are molded into hollow forms without the need for clamping or seams. This improves the integrity of the piece when it is finished. You can see examples of this technology everywhere, from the interior of your car to the case that houses your television or computer. The mold is spun at a slow, even speed with the poly resin inside, causing the material to coat the sides of the mold. The temperature gradually changes from very hot to cool, allowing the layer of melted poly resin to harden while maintaining its shape. It is then removed from the mold. While this is an expanding industry with many advantages, there are also a few disadvantages to rotational molding.
Unlike traditional molding where turnaround is fairly quick, rotational molding takes more time. The material must be spun slowly enough to coat and dry evenly, and this takes patience. Due to the reduced output, it takes longer to market fewer materials.
Rotational molding is limited to poly-based resins such as polyethylene, polycarbonate, polyurethane, polyamide and polypropalene, to name a few. Nylon and plastisols may also be used. These plastics must be ground to a very fine powder before they can be used in rotational molding.
The materials costs are high due to the nature of the plastics that must be used. In addition, the grinding of the plastics into powder is another cost consideration. This takes time and money. There are also additives that must be included, and these pose an additional cost.
There are a few limitations to rotational molding. Some shapes and features are difficult to incorporate, so anything more involved than a simple shape may slow down production, thus raising production costs. In a world where time is money, this can be considered a disadvantage.