Subject 2 : Rotational moulding

Rotational moulding involves a heated hollow mold which is filled with a charge or shot weight of material. It is then slowly rotated (usually around two perpendicular axes) causing the softened material to disperse and stick to the walls of the mold. In order to maintain even thickness throughout the part, the mold continues to rotate at all times during the heating phase and to avoid sagging or deformation also during the cooling phase. The process was applied to plastics in the 1940s but in the early years was little used because it was a slow process restricted to a small number of plastics. Over the past two decades, improvements in process control and developments with plastic powders have resulted in a significant increase in usage.

I have also been able to witness the rotational moulding at first hand in two different factories , Numantic international where they produce the very famous henry vacuums and Leafield corporations where they specialise in using rotational moulding as a main production method. We witness first hand the step by step process that rotational moulding will need to do.

220px-Rotocasting_machine 220px-Rock&Roll_HRM1800

Advantages of rotational moulding is that its a low cost production which can also use recyclable materials to produce the products also another advantage is that you can use rotational moulding to produce all different kinds of forms using the one machine, the only thing that need to be changed is the frames .

Disadvantages of rotational moulding is that its a slow production process which require the product to be cool down , also the product itself is not always consistent and the wall thickness of the product itself cannot be the same thickness and with the design there are restrictions such as not being able to create open areas due to the manufacturing method.


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