WHAT ROTATIONAL MOULDING IS ...

Rotational moulding, or rotomoulding, is a cost-effective way to produce large parts. Plastic resins are loaded into a mould that is heated as it is rotated slowly on both the vertical and the horizontal axis. This simultaneous heating and rotation distributes the material on the inner surfaces of the mould and fuses it.

Rotomoulding is a four-phase process, which comprises loading, heating, cooling, and unloading the mould. In the first stage the pre-measured plastic resin is loaded into the mould. (Polyethylenes and plastisols are the most common of the many materials used in rotomoulding resins.) Several moulds may be loaded on a given machine at the same time.

The charged moulds are then closed and moved into the oven, where they slowly rotate on two axes. As the heat penetrates the moulds, the melting resin adheres to the mould’s inner surface until it is thoroughly fused, evenly coating the entire surface.

During the cooling phase, the mould continues to be rotated to maintain even walls as air, water spray (or a combination of the two) gradually cools the mould. The mould is then opened, the finished part removed, and the mould is ready for its next cycle.

THE BENEFITS OF ROTOMOULDING

Unlike other plastic moulding processes, rotomoulding results in seamless parts with uniform wall thickness and more material in corners, to absorb shocks and stresses where they occur most. Since the material isn’t stressed during production (as in thermoforming or pressure forming) the finished part is stronger. Plus, the moulds don’t need to be designed to withstand the high pressures of injection moulding. Since the mould has no internal core to manufacture, tooling costs are lower – and minor changes can be easily made to existing moulds.

Rotomoulding also offers superb flexibility and precision. Complex contours, metal inserts, flanges, and moulded-in threads can be designed into the walls – requiring fewer steps to get to your finished product. And the color can never crack or chip off, because it’s moulded-in, all the way through. Of course, this means no painting is required.

Generally lighter in weight than metal or fiberglass, rotomoulded plastic products are easy to handle and less expensive to ship. They’re tough, long lasting, and corrosion-proof.

Other advantages of rotational moulding are:

• Short lead-time;
• Excellent load-bearing properties;
• Ability to produce multi-wall mouldings, which can be left hollow or foam-filled;
• Economical for short production runs as well as high volume output;
• Resins can be tailored to suit the application – e.g., to satisfy FDA requirements;
• Minor undercuts are possible – without the need for draft angles;
• Rotational moulding is incredibly versatile, able to handle a vast variety of shapes and sizes. Many parts cannot be readily produced by any other method.

INDUSTRIAL & COMMERCIAL APPLICATIONS – Agriculture, Health & Science, & Point of Sale (POS):

• Specialty tanks and containers for fuel, water, and chemical processing;
• Livestock feeders;
• Drainage systems;
• Food service containers;
• Instrument housings;
• Vending machines; and
• Highway barriers and road markers.

CONSUMER PRODUCTS APPLICATIONS – Recreational, Special Application, Toy, & Transportation:

• Boats and kayaks;
• Childcare seats;
• Light globes;
• Tool carts;
• Planter pots;
• Playing balls;
• Playground equipment;
• Headrests;
• Truck/cart liners; and
• Air ducts.