Experimental investigation and numerical simulation of the heating/cooling process in rotational molding enhanced with fins

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 investigate, both experimentally and numerically, the heating/cooling process of rotational molds enhanced with fins. Rotational molding experiments were carried out in a laboratory scale uniaxial machine, which is capable of measuring internal air temperature in the cycle. Molds enhanced with three types of fins, including pin, rectangular, and triangular fins, were used to manufacture the parts. It was found that the mold surface enhanced with pins exhibited the highest heating and cooling rate. Nevertheless, from a design perspective, ease of manufacturing needs to be taken into account which could make triangular fin geometry a better choice to enhanced heat transfer. In addition, an unsteady-state, nonlinear heat transfer model of rotational molding has been proposed to numerically simulate the internal air temperature profiles. It is shown that the numerical predictions are in good agreement with experimental data. This model enables prediction of the heating and cooling time of rotational molding enhanced with fins, and hence the overall cycle time for the process.