INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 11, No. 6, pp. 879-890 DECEMBER 2010 / 879 DOI: 10.1007/s12541-010-0107-z NOMENCLATURE α = Thermal diffusivity of polymer (m 2 /s) σ T = Standard deviation of temperature distribution d = Diameter of baffle (mm) h c = Heat transfer coefficient (W/m 2 °C) k m = Thermal conductivity of mold material (W/m°C) k p = Thermal conductivity of polymer (W/m°C) q = Instantaneous heat flux (W/m 2 ) s = Thickness of molded part (mm) t c = Cooling time (s) T avg = verage temperature through part’s thickness (°C) T e = Ejection temperature (°C) T i = Injection temperature (°C) T m = Mold temperature (°C) T max = Maximum temperature at center line of thickness (°C) T ps = Molded part surface temperature (°C) T w = Coolant temperature (°C) x = The pitch of baffles in x direction (mm) y = The pitch of baffles in y direction (mm) z = Distance from baffle’s tip to cavity surface (mm) 1. Introduction Injection molding has been the most popular method for making plastic product due to high efficiency and manufacturability. The injection molding process includes three significant stages: filling and packing stage, cooling stage and ejection stage. Among these stages, cooling stage is very important one because it mainly affects the productivity and molding quality. It is well known that more than two thirds of the molding cycle is taken up by cooling process. An appropriate design of cooling channel reduces cooling time, increases the productivity and minimizes undesired defects such as sink marks, differential shrinkage, thermal residual stress and warpage. For many years, the importance of cooling stage in injection molding has drawn a great attention from researchers and mold designers. They have been struggling for the improvement of the cooling system in the plastic injection mold. This field of study can be divided into two groups: optimizing conventional cooling channels (straight-drilled cooling lines) and finding new Optimization of Conformal Cooling Channels with Array of Baffles for Plastic Injection Mold Hong-Seok Park 1,# and Xuan-Phuong Dang 1 1 School of Mechanical and Automotive Engineering, University of Ulsan, San 29, Mugeo 2-dong, Namgu, Ulsan, Korea, 680-749 # Corresponding Author / E-mail: phosk@ulsan.ac.kr, TEL: +82-52-259-2294, FAX: +82-52-259-1680 KEYWORDS: Conformal cooling channel, Array of baffles, Injection molding, Optimization Cooling system has an important role in the injection molding process in terms of not only productivity and quality, but also mold-making cost. In this paper, a conformal cooling channel with an array of baffles is proposed for obtaining uniform cooling over the entire free-form surface of molded parts. A new algorithm for calculating temperature distribution through molding thickness, mold surface temperature and cooling time was presented. The relation among cooling channels’ configuration, process parameters, mold material, molding thickness and temperature distribution in the mold for a given polymer is expressed by a system of approximate equations. This relation was established by the design of experiment and response surface methodology based on an adequate physical-mathematical model, finite difference method and numerical simulation. By applying this approximate mathematical relation, the optimization process for obtaining target mold temperature, uniform temperature distribution and minimizing the cooling time becomes more effective. Two case studies were carried out to test and validate the proposed method. The results show that present approach improves the cooling performance and facilitates the mold design process in comparison to the trial-and-error simulation-based method. Manuscript received: May 14, 2010 / Accepted: July 7, 2010 © KSPE and Springer 2010