Cycle Time Reduction in Injection Molding Process by Selection of Robust Cooling Channel Design

Cycle time of a part in injection molding process is very important as the rate of production and the quality of the parts produced depend on it, whereas the cycle time of a part can be reduced by reducing the cooling time which can only be achieved by the uniform temperature distribution in the molded part which helps in quick dissipation of heat. Conformal cooling channel design is the solution to the problem which basically “conforms” to the shape of cavity in the molds. This paper describes the analytical study of cooling analysis of different types of cooling channel designs. The best cooling channel design is also selected on the basis of minimum time to reach ejection temperature, uniform temperature distribution, and minimum warpage of part. “Creo Elements/Pro 5.0” is used to model the case study, its molds, and the cooling circuit whereas analytical study is done using “Autodesk Moldflow Advisor 2013 (AMFA).” 1. Introduction Injection molding is a major part of the plastic industry and is a huge business worldwide, consuming approximately 32？wt% of all plastic. It is in the second place to extrusion, which consumes approximately 36？wt% [1]. The injection molding process consists of melting of polymer and then its injection into the cavity in the molds. This molten material is ejected from the molds after reaching the cooling temperature. Thus, the main phases of the injection molding process are injection, packing, cooling, and part ejection. Among these, part cooling takes up 50 to 80 percent of the cycle time [2]. The amount of time in the injection and packing phases is low and cannot be reduced much further. However, because cooling time can be more than two-thirds of the molding cycle, a cooling time reduction will considerably increase the production rate as well as reduce costs [3]. But decreasing cooling time can result in excessive shrinkage and warpage in parts [4]. So there is a need of a cooling technique to reduce the cycle time without compromising on part quality. In the cooling phase, heat transfers between the molten material inside the cavity and the cooling fluid (generally water) flowing through the cooling channels inside the mold, until ejection temperature is achieved and part is stable enough for demolding. Thus this rate of heat exchange is very important and directly related to the time taken by the cooling phase. So it is important to understand and optimize the cooling channel design to optimize the rate of heat transfer in an injection molding process. Proper design of the cooling channel is required for a faster