Rotational moulding process
The rotational moulding process differs from other plastic moulding methods because the heating, moulding and cooling all take place when the raw material (polymer) is already inside the moulding tool, meaning no external pressure is required to form the shape.
It is an ideal process for a variety of manufacturing scenarios including:
Moulding hollow products for example fuel tanks or water tanks
Where uniform wall thickness or strengthened areas are required
Where the number of products to be manufactured is relatively low, because the cost of a mould is much lower than other methods
Moulding complex shapes, undercuts and for including metal inserts
Producing very large products from a single moulded piece (2m+ length)
Tools are typically manufactured from aluminium or steel in two halves.
Polymer powder is placed in the tool, which is locked and loaded into the oven.
The tool is then rotated on two axes, distributing the polymer evenly around the inside of the tool.
The tool is heated at a very controlled rate and the polymer sticks to the inside of the tool and because it is rotated simultaneously on two axes, an even coating builds up to form the product.
The tool is rotated for a period of time after the polymer has formed the shape to ensure that the product surfaces are properly formed and that no air bubbles have formed which could weaken the structure of the finished product.
The tool is then cooled down either using air jets, water mist or water spray causing the polymer to cool down and retain its shape.
Finally the mould is opened and the finished product removed.