A disadvantage of rotational moulding is the relatively long cycle times and hence production output. It is essential therefore, to calculate the most cost-effective process given the volume of business against the tooling, overheads and material costs.

Rotationally moulded products may be simple or complex in shape and include features such as strengthening ribs, inserts of brass or steel, moulded threads, holes, textured and engraved surfaces.

The process provides an extremely uniform wall thickness even at corners and sharp angles. In comparison, blow moulding tends to stretch the molten plastic and the finished product has inherent stress and thus, locations where failure may occur in service.

The rotational moulding process has a limited range of mouldable polymers available which is a slight disadvantage to many designers. Polyethylene is the most commonly used material for rotomoulding but to its advantage it is extremely versatile.

In summary, large products may be produced without incurring high start-up costs. The fact that production rates are relatively slow is offset by the fact that you don't have to make millions of parts before the tooling costs are recovered.

image of carousel type rotational moulding machine courtesy of Alan Yorke Engineering Ltd