Erhardt+Leimer, the specialist for automation and inspection technology from Stadtbergen near Augsburg, recently placed in operation a newly developed control system for the automatic pre-positioning of the roll on a winding station. The goal is to feed the web, which in this case comprises a multiple layer packaging material, as precisely as possible to a pivoting frame, which in turn is ahead of the slitter unit.
Irrespective of how inaccurately the machine operator pushes the roll onto the shaft: a broadband sensor of type FE 45 provides the positions of the two edges of the web to the winding controller, which in turn positions the roll at the set position via an actuator (AG 26). If an adjustable limit for the movement of the pivoting frame is exceeded the unwinder corrects in small steps in the same direction. As a consequence the splice offset is minimised and creasing due to large corrections to the web offset by the subsequent pivoting frame is avoided. In this way the infeed and outfeed lengths for the pivoting frame can be reduced particularly for stiff materials, as the control window is kept in the middle.
The broadband sensor FE 45 is accurate to the millimeter over the complete width of the web without motorised follow-up and can output this information together with the edge positions and the center offset as measured values to the machine control system via an optional interface.
Another important advantage of this automated solution is the reduction of the setup time. There is also less waste, as it takes a large number of running meters to compensate for a large splice offset.