Injection compression molding of wedge-shaped plates: Effects of processing parameters

Thermoplastic wedge-shaped plates have been widely used as a light guide module in thin film transistor (TFT) liquid crystal display (LCD). This article studied the injection compression molding of thermoplastic wedge-shaped plates. The effects of various processing parameters on the dimensional quality of molded parts were studied including melt temperature, mold temperature, melt filling pressure, short shot size, packing pressure, compression pressure, and cooling time. The material used was general-purpose polystyrene. Injection compression molding experiments were conducted on a modified injection-molding machine equipped with a melt compression unit. After molding, the quality of parts was evaluated by the deviation from mold dimensions. An experimental study, based on the Taguchi orthogonal array design, was conducted to identify the relative significance of all these parameters. Among the processing parameters in this study, short shot size and melt temperature were found to be the principal parameters affecting the dimensional accuracy of molded parts. The effects of the compression stage on the birefringence of molded plates were also investigated. The final goal of this study was to better understand the effects of various processing factors on the injection compression molding of wedge-shaped plates, so that steps could be taken to optimize the molding process. This provides significant advantages in terms of improved product quality.