Global Roto-Moulding is an industry leader
in rotational moulded plastic in an
ABOUT ROTATIONAL MOULDING
THE INNOVATIVE FABRICATION OF PLASTIC PRODUCTS
PUSHING THE BOUNDARIES OF THE DESIGN AND APPLICATION OF PLASTIC PRODUCTS.
Rotational moulding (or rotomoulding) has grown in popularity for creating any number of plastic products, with tanks and containers being the most prominent. However with experience and innovative design, practically any product that is hollow can be made using this process.
Rotomoulding is a process of plastic fabrication, where a plastic is melted until it takes the shape of a mould. The mould is heated in an oven, and rotated until the melted plastic lines the inside of the mould.
The process is fairly straight-forward, yet take years to perfect. Design principles differ to fabricating with metals, so we’re often approached with product concept ideas and work with customers to design using plastic. Once designed, the rotational method produces complex shapes (such as tanks or mud guards) that are strong, lightweight, easy to replicate, and above all, cost-effective.
Moulds and Materials
Precise tooling for quality products
Moulds are the ‘tool’ of the project, and it should not be underestimate the importance of good quality tools. Fabrication of the tool is often the biggest investment in the process, especially for complex shapes, due largely to the need for the pattern. Once the pattern is known however, they are easy and affordable to replicate using this very precise method.
Complex shapes usually require fabricating cast aluminum moulds, while larger shapes like industrial fluid tanks would be made from a sheet metal mould. For a polished-look to the product, the moulds themselves can be finished with a fine gloss, textured, or left unfinished depending on the application of the final product.
Unlike injection moulds, rotational moulds are much cheaper to make as they operate under less pressure. Inside the mould, the plastic is heated and rotated. As the plastic melts it forms a pool at the bottom of the mould, and begins to stick to and coat the inside as the mould is rotated. With careful design and engineering, exceptional thicknesses control can be achieved using this method.
The perfect material for rotational moulding
Polyethylene is well suited to the process of rotomoulding, and for many years have been the most practical and economic. The ability to stay stable during the prolonged heating process and its flow characteristics that lead to uniform thickness inside the mould is why it remains the most popular plastic for rotomoulding.
The polyethylene is divided into three categories: low, medium, and high. Previously, higher density plastic products stronger products, but the trade-off was less impact strength and stress-crack resistance. Today, low-density polyethylene is both stiff and strong while retaining its tough and stress crack resistance.
The end results is a wide range of products that can be made from rotomoulded plastic. While the process is best known for making tanks, many designers now use it to create plastic parts for medical products, consumer products, agricultural and garden equipment, automotive components, toys, furniture and sporting equipment. Innovation is constant, especially here at Global, and new uses and market sectors are constantly evolving.