The design stage requires that consideration be given to desirable wall thickness,
the corner radii, stiffening ribs, "kiss-off" ribs, holes, threads, inserts and undercuts.
With a thorough understanding of the requirements to be met by the product the designer is
able to determine the plastic material which will satisfy the functional needs of the product.
Important too is the consideration of human engineering and appearance, or industrial design.
The corner radii is an important consideration to improve the molding of the part and to
distribute the stresses on a corner over a broad area.
Rotational molded parts often have walls which are thin in comparison to the their size. The
use of ribs can increase the stiffness of the part while keeping the wall thickness to a
minimum. Kiss-off ribbing is a technique in which closely-spaced walls are attached to
each other to provide added strength and dimensional stability. An obvious example is the
slim-line water tank. Water pressure will cause bulging unless the side walls are supported,
either internally or externally.