All rotational machinery operates on the same principle: powdered resin is tumbled within a heated mold using continual rotation to create a hollow product with a uniform wall thickness.
While adhering to the basic principle, each type of rotational molding machine operates on a slightly different basis:
Carousel – one of the most popular rotational machines, features up to four independent or fixed arms and six stations. While fixed arms work well when identical cycle times are needed on each arm, independent arms allow for different cycle times and wall thicknesses.
Shuttle – usually has two arms that move the mold back and forth between the heating and cooling areas. This type of machine requires a minimum footprint compared to other machines.
Rock and roll – designed mainly to manufacturer long, narrow parts. It tips and rocks mold 45 degrees above or below the horizon in the opposite direction of the 360-degree rotation.
Clamshell – employs a single arm, usually supported by other arms on each end. It heats and cools the mold in the same chamber and takes up less space than similar shuttle and swing arm machines.
Vertical – allows for loading and unloading at the front of the machine between the heating and cooling areas. Its compact heating and cooling chambers make it energy efficient.
Swing arm – features up to four independent arms with bi-axial movement. It’s not necessary to operate all the arms at the same time.
Regardless of the mode of operation, all rotational machinery runs through the same four stages:
The resins most often used in rotational molding machines include:
Rotational machinery can be used to make small or large parts for a wide range of end markets, including: