Rotomoulding is a way to manufacture hollow plastic products.In this process, very complicated shapes with the least cost and without any wastage are produced. Rotomoulding process is done under the pressure of atmosphere, and the materials are melted in the mould instead of melting the materials and injecting them inside the mould, In this process, movable materials are usually used to transfer suitable heat in the moulds .
The effective factors in this process are: heat, time of moulding, way and speed of cooling, speed of pivots turning the moulds and the ratio of the speed of turning. In this process the global shrinkage and the warpage are very important subjects.
This process is divided into four stages:
Charging :
The mould that has been designed in the shape of a final product is opened in this stage, and a certain amount of a considered polymer substance, in the form of powder or liquid, is poured in the low half of the mould.
Heating :
After the mould is closed, the machine starts to work and the mould is rotated and / or rocked about two principal axes at a relatively low speed in the oven. The polymer in the mould reaches its melting -point and begins to melt. The polymer near to the mould’s inner wall is melted in a layered way and stuck to the mould wall as a result of molecular adherence.
Cooling :
In this stage, the turning mould is put into a cooling compartment. Through cooling the mould by means of sprinkling water and the air course, the polymer in it also cooled and the final product is formed.
Demoulding :
The machine stops in this stage .Through opening the half of the mould, the final product is taken out of it.
