Optimal two-stage single-screw design for polymethyl methacrylate extrusion by taguchi technique

The optimal screw design for polymethyl methacrylate (PMMA) extrusion was studied. The Taguchi method was used to determine the optimal screw geometry and processing conditions for the extrusion of PMMA sheet and/or film. To get the high quality of sheet and/or film, perfect melting, adequate melt temperature, and enough metering pressure were necessary. The six factors relating screw geometry and processing condition were chosen with three levels for each factor. The orthogonal array was selected as the most suitable for fabricating the experimental design, L2736, with 6 columns and 27 variations. The smaller-the-better was used as an optimization criterion. The optimal values of these parameters were 8D of feeding zone length, 15 mm of feeding zone depth, 4D of melting zone length, 3 of compression ratio, 49 rpm of screw speed, and 165/180/200/250/260/2660/260 of barrel temperature. Under these conditions, the completeness of melting of solid bed, the stability of solid bed, the melt pressure at vent zone, and the melt temperature at the end of screw were 0, 0, 0 bar, and 279.5 °C, respectively.