Patent ID: 8757535

Claim:
A method for reducing feed rate variations in a web material when unwinding a parent roll about a longitudinal axis to transport the web material away from the parent roll at a web takeoff point, the method comprising the steps of: dividing the parent roll into a plurality of angular sectors disposed about the longitudinal axis; using an ideal speed reference signal to drive the parent roll at a driving speed corresponding to a web feed rate of a round parent roll and at a drive point being disposed on the outer surface either coincident with or spaced from the web takeoff point; correlating each of the sectors at the web takeoff point with a corresponding one of the sectors at the drive point; determining a rotational speed for each of the sectors, while at the drive point, as the parent roll is being driven; calculating a drive point radius of each of the sectors by calculating the radius at the drive point of the parent roll for each of the sectors as a function of the driving speed and the rotational speed; calculating an ideal drive point radius by determining an average for the drive point radii for all of the sectors; calculating a drive point correction factor for each of the sectors as a function of the drive point radius and the ideal drive point radius; measuring a web takeoff point radius for each of the sectors by measuring the radius at or near the web takeoff point of the parent roll for each of the sectors as the parent roll is being driven at the drive point; calculating an ideal web takeoff point radius by determining an average for the web takeoff point radii for all of the sectors; calculating a web takeoff point correction factor for each of the sectors as a function of the ideal web takeoff point radius and the web takeoff point radius; calculating a total correction factor for each of the sectors as a function of the drive point correction factor and the web takeoff point correction factor; multiplying the total correction factor for each of the sectors by the ideal speed reference signal to establish a corrected speed reference signal for each of the sectors; and, adjusting the driving speed of the parent roll for each of the sectors to a corrected driving speed as each of the sectors approaches or is at the drive point using the corrected speed reference signal to at least approximate the web feed rate of the round parent roll to reduce feed rate variations in the web material at the web takeoff point.