Rotational molding (commonly known as rotomolding) is a high-temperature, low-pressure thermoplastic manufacturing process used to produce hollow, one-piece seamless plastic articles characterized by
Rotational molding (commonly known as rotomolding) is a high-temperature, low-pressure thermoplastic manufacturing process used to produce hollow, one-piece seamless plastic articles characterized by heavy wall thicknesses and large structural volumes. Unlike injection molding or extrusion blow molding, rotomolding does not rely on high pressure or melt shear. Instead, the process utilizes a finely ground polymer powder that is distributed evenly over the inner surfaces of a heated mold rotating biaxially inside a closed oven chamber.
The physical cycle consists of four distinct, sequential phases:
The kinematic design of rotational molding demands simultaneous rotation of the mold about two mutually perpendicular axes: the major axis (arm rotation) and the minor axis (plate/platelet rotation). Motion is transmitted through a system of concentric drive shafts, bevel gears, and chains housed inside the mechanical arm.
Because rotational molding operates under zero external pressure (with only atmospheric pressure inside the cavity), molds are not subjected to severe mechanical loads. This enables the fabrication of lightweight tooling with thin walls to ensure rapid heating and cooling cycles. The primary mold types are classified by their manufacturing method:
| Category | Formative Manufacturing |
|---|---|
| Library | CNC machining |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert