Rotational moulding is the method by which many plastics are moulded 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 mould is spun at a slow, even speed with the poly resin inside, causing the material to coat the sides of the mould. 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 mould. While this is an expanding industry with many advantages, there are also a few disadvantages to rotational moulding.
Unlike traditional moulding where turnaround is fairly quick, rotational moulding 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 moulding is limited to poly-based resins such as polythene, 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 moulding.
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 moulding. 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.