An apparatus, such as an extruding machine, configured to form a sheath, e.g. insulative layer, over an elongate member, e.g. a wire cable including an extruder to apply the material forming the sheath, a drive mechanism configured to move the elongate member through the extruder at a line speed, a thickness sensor to determine the thickness of the material, and a controller. The controller is programmed to determine a deviation between the actual material thickness a desired thickness, determine a correction factor value based on the deviation between the actual thickness and the desired thickness of the material applied, and adjust the line speed, via the drive mechanism, based on the line speed, an extruder feeder speed, the correction factor value and a material factor value that is based on rheological properties of the material. A method of operating such an extruding machine is also presented.