As a common manufacturing process, plastic injection molding
has been widely used to fabricate a variety of products. During a
plastic injection molding cycle, the plastic part and the mold must
be cooled to room temperature so that the molded part can be solidified
and with its shape maintained. A substantial portion of the
total molding cycle (e.g., as much as 80%) could be required for
cooling. To improve the efficiency, cooling channels are usually integrated
into the mold. In general, conventional cooling channels in
simple shapes are fabricated by drilling straight-line holes. These
usually lead to non-uniform mold cooling (Ref. [1]). Without attaining
the uniformity of surface temperature in a mold, the quality