Since the pioneering work on Extrusion was published in 1956 by DuPont’s Central Research, 50 years has passed with many follow-up excellent research and developments and tremendous growth of Extrusion Industry. The extrusion area is not of scientific curiosity alone. The practice was done without detailed understanding of its mechanism and most of scale-up was done with trial and error. Many practitioners had established their own technologies and kept mostly as trade secrets or patented. However, the extrusion research took a great leap with experimental work at Union Carbide and Western Electric which brought out more specific on the screw design and proposed mechanisms of solid conveying, melting and melt conveying with experimental data with many commodity polymers. These data were also limited to pilot plant scale extruder sizes. Some scale-up work were proposed and the scale-up was rather limited. In this talk, some of the past production scale-up work and recent scale-up with production data of Polystyrene foam (XPS) manufacturing will be reviewed to give a better insight in the screw design, sensitivity of process control and variation of temperature profiles in the extruder, especially in the tandem extruder system. Data presented here are difficult to get because it bears the burden of cost due to generation of out of specification products. In order to make sure data acquisition system will obtain on-line data for optimum operation of production line to increase the productivity, one needs minimum instrumentations to install for the line. Keywords: Extrusion, Scale-up, Sensitivity, Data acquisition