Method and apparatus for producing a primary roll of material

摘要

The method is for producing a first primary roll having a predetermined lateral surface defined by a diameter Df. The primary roll is made of material wound around a spindle. The material is used to produce smaller secondary rolls of material. The method comprises steps of (a) calculating a portion Sf of the lateral surface, which is covered by the spindle; (b) calculating a portion Si of the lateral surface, Which represents material needed to produce the smaller secondary rolls of material; (c) calculating a compression factor K1 which is derived from a compression rate K of a previous second primary roll used to produce previous secondary rolls with respect to the previous secondary rolls; (d) calculating Df where: <IMAGE> (e) winding up material around the spindle to produce the first primary roll until a diameter of the first primary roll reaches said diameter Df; whereby loss of material is reduced by taking into account compression factor K1 which varies with respect to time. An apparatus to perform the present method is also provided.