A full size rotational molding oven is large, hot and noisy, but does nothing without a mold. The primary
function of the mold is to define the shape of the molded part but consideration must be given to the attachment
of the mold to the moving machine parts, the opening and closing of the mold, the removal of the finished product
and keeping the parts of the mold together during the process.
Generally the molds are either of cast aluminium or fabricated from sheet metal. The type depends on a number of
factors, including the complexity of the shape to be produced, the size of the product and the cost of the
mold. Where the shape is complex it might be necessary to use a multi-piece mold. A majority of molds
will have a vent to ensure maintenance of atmospheric pressure in the cavity.
The mold is commonly supported by a frame which is usually fabricated from steel and has mounting lugs
to facilitate the placement in the oven. The frame itself should be properly designed to ensure that it
does not shroud some spots from receiving heat and the materials themselves must be of sufficient thermal
conductivity to ensure the heat gets from the oven interior to the plastic within the mold.
Notwithstanding the size, weight and apparent strength of the mold it is important that great care be taken
with it. Small imperfections caused by bumps and knocks can have a significant impact on the quality of the
finished product. Mold maintence and proper handling procedures are paramount.