System and methods for the calculation of additional local stretching in a web

A method for calculating in real-time the additional local stretching of a moving web through a converting process and using the calculated additional local stretching for estimating the position of a web defect in a web during rewinding comprises the steps of:

• providing a moving web (5) of material,
• providing a control system (19, 19′),
• marking the moving web with a plurality of coded position markers at predetermined intervals,
• examining the web for web defects and recording the distance of each web defect from at least one of the two closest coded position markers while winding the web on a reel (11),
• rewinding the web from the reel (11), detecting coded position markers and measuring the distance between at least one pair of coded position markers, and
• using the control system, within a time period equal to or less than one second after measuring the distance between said at least one pair of coded position markers, to:
• divide the measured distance between said at least one pair of coded position markers by the predetermined distance between said pair of coded position markers to determine the additional local stretching of the rewound web between said pair of coded position markers;
• and
• when approaching, or immediately after passing, the coded position marker before a web defect, multiply the recorded distance of the web defect from said coded position marker before a web defect, by said additional local stretching of the web determined for at least one pair of coded position markers to determine the estimated position of the web defect in the machine direction on the rewinding web.

A method for calculating in real-time the additional local stretching of a moving web through a converting process and using the calculated local stretching for estimating the position of a web defect in a web during rewinding comprises the steps of:

• providing a moving web (3) of material,
• providing a control system (19, 19′),
• marking the moving web with a plurality of coded position markers at predetermined intervals,
• examining the web for web defects and recording the distance of each web defect from at least the next following coded position marker while winding the web on a reel (11),
• rewinding the web from the reel (11), detecting the coded position markers and measuring the distance between at least one pair of coded position markers, and
• using the control system, within a time period equal to or less than one second after measuring the distance between said at least one pair of coded position markers, to:
• divide the measured distance between each said pair of coded position markers by the predetermined distance between said pair of coded position markers to determine the additional local stretching of the rewinding web between said pair of coded position markers;
• and
• when approaching, or immediately after passing, the coded position marker closest to a web defect, multiply the recorded distance of the web defect from the coded position marker before the web defect by the local additional stretching of the web determined for said pair of coded position markers to determine the estimated position of the web defect in the machine direction on the rewinding web.