Patent ID: 7124670

Claim:
A method of estimating a lifetime of a sheet cutter for cutting a sheet piece from a sheet by shearing, wherein the sheet cutter comprises a fixed blade; a movable blade which is movable along the fixed blade; and an apparatus for estimating a lifetime of the movable blade for cutting a sheet; and a receiving element that receives a sheet piece that is cut off from the sheet; said method comprising the steps of: (a) detecting a value of a parameter representing a cutting resistance during sheet cutting, wherein the parameter is a value of a current that is loaded onto a motor for driving the cutter; (b) comparing the detected value of the parameter with a predetermined reference value, wherein it is determined that the movable blade is unfit for use when the value of the parameter exceeds the predetermined reference value; and (c) outputting a result based on the comparison; wherein the movable blade comprises a disk which is rotatably supported, and the receiving element comprises a roller which is rotatably supported, and wherein the receiving element is vertically coplanar with the movable blade.