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In recently year, the plastic product is almost made by injection molding method. In this paper, a hot gas was used for mold heating with the gas temperature varied from 200°C to 400°C. The results showed that with three types of gas temperature, the heating rate is high in the first 20 s and the highest heating speed of 8.25°C/s could be achieved with 400°C gas. In all cases, the mold temperature has a limitation after 30 s of heating. In our experiment, the limitation of cavity temperature is 172.2°C. This cavity temperature is almost good for the melt flow in to the cavity, especially with the thin wall molding cases.

Parting direction selection and evaluation plays an important role in injection mold design. In order to select suitable parting direction, several criteria need to be taken into account including undercut feature, parting line complexity, draw depth, project area, and flatness. This paper proposes an extension of fuzzy multi-criteria decision making (MCDM) approach to support parting direction selection and evaluation process. In proposed approach, the rating of alternatives and important weight of criteria are expressed linguistic terms. We then develop the membership functions for the final fuzzy evaluation values of alternatives by the interval arithmetic of fuzzy numbers. Next, this paper uses the new left and right indices ranking approach to defuzzify the normalized weighted ratings into crisp values to determine the ranking order of alternatives. Finally, a numerical example is used to illustrate the applicability and efficiency of the proposed method.