Method of controlling fly cutting rotary shear

A method of controlling an on-the-fly rotary shear in which a difference between a run length L.sub.1 of a stock and a circumferential length L.sub.2 which results from a rotation of a cutting edge is subtracted, together with a circumferential length L.sub.20 corresponding to one revolution of the cutting edge, from a preset cut length L.sub.0 to define a remaining length, which is then converted into a speed, referred to as a remaining length speed, which is subtracted from a stock running speed to define a speed reference for the rotation of the cutting edge, an acceleration or a deceleration being applied to the rotation of the cutting edge depending on the positive or negative sign of the remaining length to reduce the latter toward zero, thus achieving an on-the-fly cutting of the stock by the cutting edge while the rotational running of the cutting edge tracks the running of the stock in the proximity of the remaining length which is equal to zero;

• characterized in that a positioning settling time t.sub.s in the proximity of zero remaining length as well as a cutting time t.sub.T during which the cutting edge is brought into contact with the stock are excluded from a period of time allotted to a cutting operation which is determined by a present cut length L.sub.0 and a stock running speed V to define a remaining time, a fraction of the remaining time which is as long as possible being used to accelerate or decelerate the rotation of the cutting edge.

A method of controlling an on-the-fly rotary shear in which a difference between a run length L.sub.1 of a stock and a circumferential length L.sub.2 which results from a rotation of a cutting edge is subtracted, together with a circumferential length L.sub.20 corresponding to one revolution of the cutting edge, from a preset cut length L.sub.0 to define a remaining length, which is then converted into a speed, referred to as a remaining length speed, which is subtracted from a stock running speed to define a speed reference for the rotation of the cutting edge, an acceleration or a deceleration being applied to the rotation of the cutting edge depending on the positive or negative sign of the remaining length to reduce the latter toward zero, thus achieving an on-the-fly cutting of the stock by the cutting edge while the rotational running of the cutting edge tracks the running of the stock in the proximity of the remaining length which is equal to zero;

• characterized in that where a preset cut length L.sub.0 represents a longer preset length in which after each cut, the rotation of the cutting edge is decelerated to a stop, which continues for a stop interval before a next acceleration is entered, an entrance zone is provided during which the rotation of the cutting edge maintains a speed difference .DELTA. relative to the stock running speed V before the acceleration which occurs toward the cutting operation.