The present invention has as its technical problem to provide a punching method able to stably secure a stretch-flangeability equal to or greater than the case of using a punch having a flat blade at its bottom surface. The punching method of the present invention is a method of punching a metal sheet using a punching and shearing device provided with a punch having an upper blade having a horizontal part with respect to the cutting line in part and having parts other than the horizontal part comprised of inclined parts and a die having a lower blade wherein the upper blade used for the punching process has a shape where the inclined parts first contact the metal sheet at the time of a punching process.

The present invention has as its technical problem to provide a punching method able to stably secure a stretch-flangeability equal to or greater than the case of using a punch having a flat blade at its bottom surface. The punching method of the present invention is a method of punching a metal sheet using a punching and shearing device provided with a punch having an upper blade having a horizontal part with respect to the cutting line in part and having parts other than the horizontal part comprised of inclined parts and a die having a lower blade wherein the upper blade used for the punching process has a shape where the inclined parts first contact the metal sheet at the time of a punching process.

There is provided a cutting method for cutting a workpiece using a cutting tool comprising a die and a punch, including: arranging the workpiece between the die and the punch, and in a state in which a wedge-shaped first cutting part of the die and a wedge-shaped second cutting part of the punch are opposed, pushing the punch relatively to the die side to cut the workpiece; wherein: a front end angle 1 of the first cutting part and a front end angle 2 of the second cutting part are each 10 or more and 120 or less, and a front end radius R.sub.1 of the first cutting part and a front end radius R.sub.2 of the second cutting part are each 0.5% or more and 35.0% or less of a sheet thickness.

There is provided a cutting method for cutting a workpiece using a cutting tool comprising a die and a punch, including: arranging the workpiece between the die and the punch, and in a state in which a wedge-shaped first cutting part of the die and a wedge-shaped second cutting part of the punch are opposed, pushing the punch relatively to the die side to cut the workpiece; wherein: a front end angle 1 of the first cutting part and a front end angle 2 of the second cutting part are each 10 or more and 120 or less, and a front end radius R.sub.1 of the first cutting part and a front end radius R.sub.2 of the second cutting part are each 0.5% or more and 35.0% or less of a sheet thickness.

A cropping system for cropping a metal slab (102) includes at least one of a cropping length (1035, 524) system and a slab positioning system. The cropping length (1035, 524) system includes an optical sensor (118A, 118B, 318A, 318B, 518) for detecting a defect in an end (1031) of the metal slab (102), and the cropping length (1035, 524) system may determine a cropping location on the metal slab (102) based on the detected defect. The slab positioning system includes an optical sensor (118A, 118B, 318A, 318B, 518) for measuring a position of the end (1031) of the metal slab (102) relative to a cropping device of the cropping system.

A cropping system for cropping a metal slab (102) includes at least one of a cropping length (1035, 524) system and a slab positioning system. The cropping length (1035, 524) system includes an optical sensor (118A, 118B, 318A, 318B, 518) for detecting a defect in an end (1031) of the metal slab (102), and the cropping length (1035, 524) system may determine a cropping location on the metal slab (102) based on the detected defect. The slab positioning system includes an optical sensor (118A, 118B, 318A, 318B, 518) for measuring a position of the end (1031) of the metal slab (102) relative to a cropping device of the cropping system.