A dual pre-stacking system of steel plates for a single cutting line and a stacking method therefor. The dual pre-stacking system comprises: a cooling bed inspection stand, a crop shear with a cut-to-length function, a bilateral shear, 1# inkjet printer, a front pre-stacker, a cut-to-length shear, a length and thickness gauge, 2# inkjet printer, surface check/size inspection and fitting, and a rear pre-stacker arranged in order along the roller. The dual pre-stacking system and the stacking method therefor of the present invention solves the problem that the inkjet printing, size fitting and pre-stacking in the later zone of the cutting line are slow when producing steel plates with high magnification, simultaneously performs pre-stacking operation after bilateral cutting and surface check in one cutting line, achieves synchronous inkjet printing/imprinting, size fitting and pre-stacking of the steel plates at two sites along the cutting line, and improves production rate of the cutting line and warehousing efficiency of finished products.

A dual pre-stacking system of steel plates for a single cutting line and a stacking method therefor. The dual pre-stacking system comprises: a cooling bed inspection stand, a crop shear with a cut-to-length function, a bilateral shear, 1#inkjet printer, a front pre-stacker, a cut-to-length shear, a length and thickness gauge, 2#inkjet printer, surface check/size inspection and fitting, and a rear pre-stacker arranged in order along the roller. The dual pre-stacking system and the stacking method therefor of the present invention solves the problem that the inkjet printing, size fitting and pre-stacking in the later zone of the cutting line are slow when producing steel plates with high magnification, simultaneously performs pre-stacking operation after bilateral cutting and surface check in one cutting line, achieves synchronous inkjet printing/imprinting, size fitting and pre-stacking of the steel plates at two sites along the cutting line.

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.