This paper studies heat transfer during rapid heat cycle injection molding process. Actually, the mold is heated and cooled with channels in which steam or water circulates. The purpose of this numerical study is to improve the design of heating/cooling system to ameliorate the quality of the polymer part and the cycle productivity. Transfers in mold, translating thermal phenomena are predicted by the finite volume method and the fractional area volume obstacle representation in cyclic transient regime. It was found that the steady cycle is obtained rapidly (after two or three cycles) for the rapid heat cycle molding process when compared to conventional injection molding. The mathematical modeling was developed to explore the effect of control temperature system characteristics on temperature uniformity of the cavity surface and thermal response efficiency. The three-dimensional simulation results show the limitations of the conventional system when compared to the conformal configuration. This research study also compares three conformal thermal control systems, and shows that the heating energy consumption can be greatly decreased (about 27%) with the amelioration of the temperature distribution by means of the improvement of the channel layout.

A three-dimensional study of the thermal regulation system of Rapid Heat Cycle Molding process producing complex-shaped automotive part was undertaken. This numerical study aims at improving the design of thermal control system so as to improve the quality of the molded part and the process productivity. The thermal responses in mold and cavity are predicted by the commercial Finite Volume Analysis software Fluent 6.3.26 in cyclic transient regime. It was shown that a regular regime is established from the second molding cycle. Besides, the three dimensional thermal responses have shown the limitations of the classic conformal design in terms of temperature uniformity and cycle time for the complex shaped automotive part. Hence, and based on conventional manufacturing process, the efficiency of a new conformal design has been shown. In fact, simple drillings coupled with concentric tubes are able to produce complicated conformal heating/cooling channels, which are easier to fabricate, assemble and which have low manufacture cost compared with other methods. By this proposed new conformal design, we could greatly reduce the cycle time, temperature gap and energy consumption.

Recently, rapid heat cycle molding technology has been developed based on the mold heating before each polymer injection stage. For this process, successful heating and cooling phases are of great importance to ensure the cycle productivity and product quality. In this study, a three-dimensional model was developed to investigate the thermal response during the rapid heat cycle molding process. The procedure uses the finite volume method and the fractional area volume obstacle representation to obtain the thermal behavior of both polymer and mold until reaching the regular cyclic regime. The authors' objective was to determine the operating parameter effect on rapid heat cycle molding process. Thus, four parameters were studied: the heating and cooling temperatures, the heat transfer coefficient of the cooling phase, and the fouling resistance at the channels. To investigate the influence of these parameters on the product quality and the process productivity and profitability, four criteria were selected: cycle time, consumed energy, temperature gap at the surface cavity, and temperature homogeneity in the polymer part. It was found that the operating conditions had a significant effect on the rapid heat cycle molding cycle performance. It was demonstrated that the heating medium temperature affects only the heating time; however, the cooling water temperature affects both heating and cooling times. In particular, the cooling temperature range of 50-60 C reduces the consumed energy compared with the lowest temperatures, without a significant increase in the cycle time.

In this work, a three-dimensional numerical study of thermal behavior of RHCM mold for automotive parts production was undertaken. Particularly, simulation of several heating/cooling cycles was conducted to determine, at the regular cyclic regime, thermal behaviors at cavity/core plates and polymer as well as thermal and hydrodynamic behaviors at cooling water. It was demonstrated that heating/cooling channels with split flow design are suitable for RHCM regulation. Besides, to further promote part quality, process productivity, and profitability, the effect of cooling parameters, such as the coolant temperature and flow velocity in channels, on the RHCM process efficiency was analyzed. To highlight the influence of these parameters on the productivity and profitability of the process, the cycle time and the consumed energy were used. Temperature gap at the cavity plate surfaces after the heating phase as well as the maximum temperature difference (MTD) in the polymer part after the cooling phase were used as criteria to evaluate the automotive part quality. The results show that the coolant temperature increase in the range between 30 and 60°C reduces the energy consumption and improves the finished product quality with almost the same cycle time obtained by low coolant temperature. As regards to coolant flow velocity effect, an optimum value of about 1 m.s À1 improves part quality and provides a compromise between the cycle time and process profitability.

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