What are the limitations of Rotational Molding?

Unlike other Plastics molding techniques like injection modeling, in Rotational Molding, it is not possible to make sharp threads.


The Rotational Molding process involves cooling the molds. To get the final product, it has to be cooled completely with mold. Whereas, in other Plastics molding techniques, only the product needs to cool down and not the mold. This saves a considerable time, unlike in Rotomolding. It takes more time to cool down the product as well as mold. The process of cooling down the mold will also increase the financial cost. Additionally, sometimes there are chances of Plastics getting degraded due to long heating processes.
The heating and cooling processes involves heat transfer from hot environment to polymer and then from polymer to the cooling medium. This process of heat transfer is non-linear. In the first step of heating a polymer, the mold and the polymer, both attracts the heat from the heating medium. Due to Rotational Molding, polymer has thinnest walls and hence, there heat absorbing capacity is less. But, mold absorbs high temperature and Plastics should have high resistance to fixed change in the properties caused because of heat.

There is need of using a Plastics that should have sufficient quantity of antioxidant molecules as the plastic inside the mold will interact with oxygen and will eventually lead to oxidation. To overcome this, it is necessary to use material with sufficient amount of antioxidant molecule to prevent further degradation.
In the Rotomolding process, no pressure is applied to push the Plastics into the mold. To achieve that the it will fit into the mold, selected Plastics should be able to flow easily in the hollow space. For this, the characteristics of the Plastics should be selected as per the design of the part

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