Plastic injection molding is widely used for manufacturing a variety of parts。 Molding con- ditions or process parameters play a decisive role that affects the quality and productivity of plastic products。 This work reviews the state-of-the-art of the process parameter optimi- zation for plastic injection molding。 The characteristics, advantages, disadvantages, and scope of application of all of the common optimization approaches such as response sur- face model, Kriging model, artificial neural network, genetic algorithms, and hybrid approaches are addressed。 In addition, two general frameworks for simulation-based opti- mization of injection molding process parameter, including direct optimization and meta- modeling optimization, are proposed as recommended paradigms。 Two case studies are illustrated in order to demonstrate the implementation of the suggested frameworks and to compare among these optimization methods。 This work is intended as a contribution to facilitate the optimization of plastic injection molding process  parameter。 75751

1。 Introduction

Molding conditions or process parameters play an important role for the plastic injection molding。 The quality of the molded part including strength, warpage, and residual stress is greatly influenced by the conditions under which it is pro- cessed。 Molding conditions also affect the productivity, cycle time, and energy consumption of the molding process。 Molding conditions have a close relationship with other factors such as materials, part design, and tooling, which determine the qual- ity of the plastic products。 Molding conditions comprise the following important parameters [1]: melt temperature, mold temperature, fill time, packing time, and packing   pressure。

The quality of a given molded part depends not only on the plastic material properties but also on the process parameters。 Optimum process parameters reduce the cycle time and increase the quality of the product。 In practice, setting the process parameters is mainly based on the experience of the plastic engineer。 This method does not always ensure appropriate val- ues of process parameters。 Because the plastic exhibits a complex thermo-viscoelastic property, setting a proper molding condition that obtains a desired product quality is a challenge。 As the result, the process parameters are often selected from hand books and are then adjusted subsequently by the trial-and-error method。 It can be seen that trial-and-error method is costly  and time-consuming。

For the analytical approach, a number of mathematical equations have been developed for deriving proper process parameters of injection molding [2]。 However, they generally cannot always satisfy a reliable solution due to the complexity of the injection process when many simplifications are involved in the analytical equations。 Therefore, many researchers have made great effort to find the methods for optimizing molding process parameters。

Although there is a considerable amount of publications that focused on injection molding process parameters optimiza- tion, some of them still sound academic and are difficult to apply to practice。 Furthermore, there have been no comparisons, assessment about the scope of application as well as review of the strong points and weaknesses of optimization methods。 The selection of optimization method mainly depends on experience and subjective choice of each author。 Therefore, ana- lyzing the characteristics and the scope of application of existent optimization methods is a significant task。 Moreover, find- ing appropriate general frameworks that facilitate the optimization of process parameters in injection molding is  necessary。

2。 Theoretical background and survey of the injection molding process parameter optimization

2。1。