DESIGN GUIDELINES FOR
On Overview of the Rotational Molding Process
Rotational molding is a process whereby a hollow mold is filled with a powder resin and then rotated bi-axially in an oven until the resin coats the inside of the mold and cures. The mold is then cooled and the part removed. There are many advantages to this process. A primary advantage over other processes is size, some of the largest ovens now incorporate a 5.5m swing. Entire boat hulls and automobile bodies are being rotomolded in one piece. On the small part end, many small PVC parts such as ear syringes and face masks are rotationally molded. Another advantage is unrestricted design. Complex geometry is easily to incorporate into a one-piece product design. The application of solid modeling and CNC tools enables the molder to produce virtually any design. Rotational molding is a very cost effective method of redesigning four or five thermoformed or sheet metal pieces into one hollow plastic product. Rotationally molded products are recognized for their strength and durability. In this no-stress process, material tends to collect in corners and ribs making these areas thicker and thus stronger. The material does not thin out in corners as with other processes. Finally, ease in prototyping. One of the reasons that Rotational molding is a cost effective alternative to other processes is the low cost of the tooling used in this process. Since Rotational molding is a stress free process, tools are primarily a thin hollow shell and can be produced from aluminum, stainless steel, mild steel and nickel. The product forms on the inside of the mold therefore tools do not require internal cores. Tooling can be produced quickly and relatively inexpensively to other processes.
For used roto rotational molding machines, Blue-reed recommends Plastiwin.