What is Rotational Moulding ?

Rotational moulding is used for producing hollow plastic items, from the very simple to the very complex, allowing higher quality and more intricate designs to be produced than would be possible with other moulding and extrusion processes.

Rotational moulding differs from other processing methods in that no external pressure is applied during forming, because the heating, melting, shaping, and cooling stages all occur after the polymer is placed in the mould.
(See The Process below)

Rotational Moulding is also known as Rota-Moulding or Rotamoulding.

Why Rotational Moulding ?

The rotational moulding process offers more design freedom and flexibility of form than many other techniques, allowing surprisingly complex forms to be achieved that are unobtainable with other processes.

Rotational Moulding is also the economist's choice, with its simplicity and relatively cheap tooling allowing product ranges and production runs that would not otherwise be cost effective.

The advantages of rotamoulding are many and varied, including:

Ideal For Flexible Mouldings
Mouldings For High And Low Temperature Environments
Symmetrical And Asymmetrical Mouldings
Textured Mouldings
Flexibility Of Size
Engineering Polymers For High Strength And Minimum Weight
Undercuts
Low Materials Wastage And Recyclability

Low Tooling Costs
Production Runs Less Than 100
Economical Prototyping
Stress Free Moulds
Lead Times Cut To A Minimum
Hollow Shapes Moulded Without Seams, Sprues Or Injection Marks
Wall Thickness Remains Constant
Screw Heads, Bosses And Metal Inserts Can Be Moulded In

Rotational Moulding - The Process

Plastics powder or paste is heated inside a closed mould which is slowly rotated in two directions (biaxially) so that polymer forms a coating over the inside of the mould without pressure of centrifugal force.

The speed ratio between the two revolving axes is carefully planned according to the shape of the moulding. The cycle length varies from around three minutes to one hour, depending on wall thickness.

Rota-moulding is a four stage process:

Thermoplastic powder is placed inside a cold mould which closes and moves into an oven chamber.
The mould is heated to 230 - 400°C and starts to rotate simultaneously around the vertical and horizontal axes. As the mould rotates, its inner surface passes continually through the mass of powder at the bottom of the mould which fuses and adheres to the mould surface.
Still rotating, the mould moves round into the cooling chamber to be cooled by air or water jets.
The hollow moulding can be removed as soon as it can hold its shape.

Rotational Moulding - Where Now ?

Rotational moulding has grown into one of the fastest moving sectors of polymer forming in Europe. Once a relative newcomer on the plastics processing scene, it is now beginning to realise its considerable technical and design potential, and in the last five years has acquired a high degree of sophistication.

New materials, process control and growing awareness of the market value of good design are combining to propel rotamoulding from the early days of doll's heads and footballs to the high specification products of the future.

Rotational Mouldings - Examples

Rotational mouldings can be found everywhere these days, in a variety of industries such as: Aerospace, Medical, Construction, Leisure and so on.

You will find the rota moulding process is appropriate across a very wide product range including: