WARPAGE PREDICTION IN PLASTIC INJECTION MOLDED PART USING ARTIFICIAL NEURAL NETWORK

Abstract

The main objective of this paper is to predict the warpage of a circular injection molded part based on different processing parameters. The selected part is used as spacers in automotive, transmission, and industrial power generation industries. The second goal is facilitating the setup of injection molding machine without (any) need for trial and error and reducing the setup time. To meet these objectives, an artificial neural network (ANN) model was presented. This model is capable of warpage prediction of injection molded plastic parts based on variable process parameters. Under different settings, the process was simulated by Moldflow and the warpage of the part was obtained. Initially, the effects of the melt temperature, holding pressure and the mold temperature on warpage were numerically analyzed. In the second step, a group of data that had been obtained from analysis results was used for training the ANN model. Also, another group of data was applied for testing the amount of ANN model prediction error. Finally, maximum error of ANN prediction was determined. The results show that the R-Squared value for data used for training of ANN is 0.997 and for the test data, is 0.995. It would be difficult to imagine the modern world without plastics. Today, plastics are an integral part of everyone's life. Properties of the plastic materials such as high strength to weight ratio, the volume to price ratio, corrosion resistance, ease and speed of production have resulted in an ever-increasing use of them. Nowadays, in new part designs, plastics are used not only as a material for producing parts but also as alternative material for the metal alloys (1). Injection molding with its excellent dimensional tolerance is one of the most common methods in mass production of plastic parts. Generally, injection molded plastic parts do not need any finishing or secondary operations (2). This process consists of four stages that include melting, injection, holding and cooling (3). Process parameters, plastic material properties and product design criteria are the basic factors in determining the final product quality. Warpage of the molded plastic parts is one of the most important problems in injection molding process. Warped parts may not be functional or visually acceptable. Different shear rate profiles along the cross-section of part cause differences in orientation and these phenomena affect the shrinkage. Therefore, there will be variation in shrinkage in the part. Warpage occurs due to the non-uniform shear rate and temperature distribution in part material. Imbalance of shrinkage in any section of a part will produce a net force that could warp it. The stiffness of the part and the shrinkage imbalance level determine the warpage