Core Principle of Rotational Molding

Rotational molding, also known as rotomolding or rotational casting, is a low-pressure thermoforming process with an underlying working mechanism fundamentally different from high-pressure roto molding.

Its production workflow is straightforward yet rigorously controlled in terms of process logic. Powdered or paste plastic raw materials are loaded into a sealed mold. The mold rotates continuously on two axes simultaneously (main axis revolution + secondary axis rotation) while being heated entirely inside an oven. Under the combined effects of gravity and thermal energy, the raw materials melt gradually, flow freely, and evenly adhere and build up along the inner mold wall to form a consistent wall thickness. The finished hollow part is obtained after constant-temperature cooling, shaping and demolding.

The most distinctive technical feature of rotational molding lies in the entire molding process being free of high pressure, shearing force and stretching force. By contrast, injection molding relies on high-pressure extrusion to fill the mold cavity, leaving residual internal stress inside finished products, which makes them prone to deformation and cracking. Rotomolding forms parts under full low pressure; raw materials attach to the mold naturally without forced deformation, resulting in products with nearly zero internal stress. Therefore, rotomolded goods boast far superior structural stability, impact resistance and low-temperature crack resistance compared with parts made via conventional plastic molding techniques.

Standard production procedures can be summarized as: material loading into the mold → biaxial rotary heating & melting → uniform wall coating & forming → constant-temperature cooling & shaping → mold opening & demolding → trimming & post-processing. This complete production line is ideal for manufacturing large-sized, irregular-shaped, hollow, double-walled and insert composite products, offering irreplaceable advantages that cannot be matched by other plastic processing technologies.