Effect of enhancing fins on the heating/cooling efficiency of
rotational molding and the molded product qualities
Rotational molding has become one of the most important polymer processing methods for producing hollow plastic
articles. However, the long cycle time required by the rotational molding process has confounded the overall success of this
technology. Molds with extended surfaces (fins) have the potential to enhance heat transfer by increasing surface area. This
report aims to examine the effects of enhanced fins on the heating/cooling efficiency of rotational molding and on molded
product qualities. Rotational molding experiments were carried out in a laboratory-scale uniaxial machine, which is
capable of measuring internal air temperature in the cycle. Three types of fins, including pin, rectangular and triangular
fins, were used to mold the parts. Cycle-time reductions by the fins were measured. Characterization of molded part
properties was also performed after molding. It was found that the mold surfaces with pin fins exhibited the highest heating
and cooling efficiency. The use of fins in rotational molding can be better justified under conditions for which the
convective heat transfer is small. In addition, molds with extended surfaces produce parts with less shrinkage but with
greater warpage. The internal surface quality and tensile strengths of molded parts were not affected by these fins. It was
shown that the heating/cooling efficiency can be increased by the fins, and this increase provides significant advantages in
terms of reduced cycle time.