a) You were assigned to determine the production rate for a polymer extrusion process. The extruder is found to have a barrel diameter = 4.5 in and length = 11 ft. The extruder screw rotates at 60 rev/min; it has channel depth = 0.35 inches and flight angle = 20°. Testing a sample of the plastic melt showed that it has a shear viscosity = 125 x 10-4 lb-sec/in2. The part is a round part with diameter 0.375 inches. Studying the die and the characteristics of the polymer, it has been found that the die swell (rs) is 1.2 and a land length Ld = 0.75 in. Determine: (a) Qmax and pmax, (b) the shape factor Ks (c) the values of Q and p at the operating point and (d) the production rate in length of the bar/min.
b) Your company is manufacturing a product in which all the gears are made of metal. The manager formed a committee to study the possibility of replacing some of the metal gears with plastic ones. You have been assigned to this committee. Make a list of the questions that you would raise before making such a decision (full mark for 8 relevant and related questions). Explain.