Abstract: An extruder is operated continuously to produce a plastically deformable strand that is pulled through a calibrating die and a cooling by a withdrawal arrangement downstream of the die in the bath. A sensor detects the volume of the strand between the tool and the extruder and controls the withdrawal rate in accordance with the volume of the strand between the tool and the extruder so as to produce an accurately calibrated extrusion. The sensor may engage the strand at the bank formed immediately upstream of the mouth of the calibrating die or may be upstream therefrom and detect the hang or droop of the strand between the die and the extruder.