A brief description of the process…
Conceptually the rotational moulding process is fairly simple. Plastic resin in the form of a powder is placed in a hollow steel or aluminium mould which is moved into an oven and rotated on two axes at a low speed. As the material heats, the polymer starts to adhere to the mould’s inner surface and the product forms until all the powder has completely fused. The mould is then cooled by air, water or both until the cooling crystalises the polymer. It is then opened and the product removed and the mould reloaded to repeat the cycle.
The process has low tooling costs, but comparitively long cycle times. Despite this it can be a very cost-effective method of production since many products can be produced simultaneously by a single machine. It is an ideal replacement for high production fibreglass products, where durability is required or alternatively where volumes do not justify an expensive mould for one of the other processes like injection moulding and blow moulding.
The advantages of rotational moulding…
There are a number of manufacturing methods used in producing plastic products. The major advantages of rotational moulding are the following:
* Stress free, one piece mouldings that produce extremely durable parts.
* Inexpensive moulds with short lead times.
* Design flexibility to produce complex geometries and slight undercuts.
* Potential to design one part to replace multiple parts.
* Resistance to stress cracking, corroding and flaking.
* Excellent load bearing qualities.
* No seams, joins or welding.
* Suited for medium to very large sized products.
* Low to medium volumes (50 to 30,000 per annum).
* Wall thickness variation using the same mould.
* Light weight alternative – especially compared to metal.
* Good chemical resistance.
* Hygienic, smooth, food grade surfaces.
* Permanent colour graphics or moulded-in logos.
* Excellent finishes and scratch resistant surfaces with new polymers.
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