Method and system for registering pre-produced webs with variable pitch length

A method for registering an off-line produced web having pre-produced objects longitudinally spaced at a pitch interval to a converting line manufacturing disposable absorbent articles, such as diapers, pull-ups, feminine hygiene articles, and the like, or a component of a disposable absorbent article, the off-line produced web being manipulated as a controlled web in order for the pre-produced object of the controlled web to be registered in relation to a target bias position and in control automatically with a first pitched unit operation and automatically phase the first pitched unit operation in order to maintain phase of the pre-produced web with a second pitched unit operation, the method comprising the steps of;

• a. providing a controlled web having pre-produced objects spaced at a controlled pitch interval, wherein the controlled web being provided at a controlled velocity in a machine direction;
• b. providing an actual bias position of the pre-produced object on the controlled web by detecting the pre-produced object with a sensor within a manufacturing cycle of a pitched unit operation;
• c. providing a target bias position constant at a desired position within a manufacturing cycle of the first pitched unit operation;
• d. generating a correction signal based upon the actual bias position data and the target bias position constant;
• e. adjusting the controlled velocity of the controlled web in order to register the pre-produced object of the controlled web in relation to the target bias position constant;
• f. coupling the first pitched unit operation with at least one controlled web metering point by providing a converter position reference signal fed forward from the second pitched unit operation functioning as an independent axis to the controlled web metering point functioning as a dependent axis in order for the pre-produced object of the controlled web be in phase automatically with the first pitched unit operation;
• g. inferring the pre-produced object pitch from the registration control loop output and using feedforward gain to automatically adjust a target phase offset position of the second pitched unit operation in order to compensate for variations in the pre-produced object pitch and to maintain the proper phase relationship.