The cost of wear is a real number and should be understood. For example at constant rpm a 60 mm feedscrew with .020” (.5 mm) of diameter reduction (wear) will produce 10 lbs (5 Kg) LESS sellable product per hour of operation. A 90 mm feedscrew will experience double this output loss. To combat this output loss the rpm can be increased which increases the wear rate, the power usage, the melt temperature and the scrap rates. A clear understanding of the cost that results as screws and barrels wear should quickly focus a company’s resources on preventing wear or repairing worn equipment rather than compensating for this wear with higher screw rpm.