Freeman Roto Products, Inc. delivers superior-quality plastic products, accessibility to different manufacturing processes and personal customer service.
Rotational Molding Process
The principle of rotational molding of plastics is simple. Basically the process consists of introducing a known amount of plastic in powder, into a hollow, shell-like mold. The mold is rotated and/ or rocked about two principal axes at relatively low speeds as it is heated so that the plastic enclosed in the mold adheres to, and forms a thin layer against the mold surface. The mold rotation continues during the cooling phase so that the plastic retains its desired shape as it solidifies. When the plastic is sufficiently rigid, the cooling and mold rotation is stopped to allow the removal of the plastic product from the mold. At this stage, the cyclic process may be repeated. The basic steps of rotational molding are (a) mold charging, (b) mold heating, (c) mold cooling, and (d) part ejection.
Advantages of rotational molding are:
- A hollow part can be made in one piece with no weld lines or joints
- The end product is essentially stress-free
- Tooling is relatively inexpensive
- The lead time for the manufacture of a mold is relatively short
- Short production can be economically viable
- There is no material waste in that the full charge of material is normally consumed in making the part
- It is possible to make multilayer products
- Different types of product can be molded together on the one machine
- Inserts are easy to mold in
- High quality graphics can be molded in or onto parts
