Rotational moulding is a unique and cost-effective plastic moulding process used to create seamless, stress-free and hollow one-piece items of almost unlimited size. This versatile process allows for the production of diverse shapes and sizes most of which are challenging to produce using any other method. Examples of typical rotomoulded products include almost everything from tanks (all sizes and shapes), containers, bins, road barriers, traffic cones, outdoor furniture and right down to children’s toys.
What is rotomoulding?
The rotomoulding process
The one major difference between rotomoulding and other plastics processing methods is that there is no pressure involved.
Depending on the product being manufactured, the process starts by filling a hollow mould, typically made of stainless steel or aluminium, with a pre-determined quantity of polymer powder. Thereafter the mould iis closed, locked and loaded into a heated oven (between 260 °C – 370 °C). The mould is then slowly rotated, both vertically and horizontally, on a rotating axis to ensure a consistent plastic coating on the inside of the mould. The end result is a seamless product with a standardized wall thickness and more resin in corners to absorb shocks and stresses where they occur most.
At the right time and after the heat has combined the polymer to the required level, the mould is removed and cooled down either using cold air or water or a combination of both. The cooling is necessary to give the polymer a chance to set into shape. The cooling rate is carefully monitored because if it happens too quickly, the polymer will shrink too fast and the product could distort.
The benefits of rotomoulding
- Rotomoulding is a casting process that requires no pressure, making it a competitive alternative to other plastics processing methods such as injection moulding.
- Rotomoulding is the answer to creating complicated shapes because it is accommodating of production difficulties.
- Rotomoulding ensures a uniform wall thickness with stress areas such as corners, tending to be thicker. The result is a product of superior quality, strength, consistency and integrity.
- Relatively low production costs
- A versatile and flexible manufacturing process that allows for unlimited shape, size and design possibilities as well as a variety of finishes and colours.
- Minimal wastage because the required weight of polymer powder, to produce specific product, is placed inside the mould.
- Light weight when compared to other materials such as metals or concrete