Abstract: Closed loop control apparatus and methods for reducing ripples in an extruded plastic sheet include, for example, a closed loop speed control system having a roll speed sensor, a roll speed controller, and a roll drive. The roll speed sensor is communicatively coupled to the active extruder roll and configured to determine an actual roll speed of the active extruder roll. The roll speed controller is communicatively coupled to the roll speed sensor and utilizes the actual roll speed and desired roll speed to generate a command signal and transmit such signal to the roll drive. The roll drive is communicatively coupled between the roll speed controller and the active extruder roll, and utilizes the command signal to drive the active extruder roll, through its controllers and power electronics.