The traditional technique for cold sheet cutting is shearing. Shearing, as in the name itself suggests, is performed by machines called shears. The most used shears can be classified into two different types: the guillotine shears and the circular blade ones. In both cases the cutting of the sheet metal is produced by the mechanical action of two blades whose effort exceeds the resistance causing the breakage of the material. The guillotine shears are the most common and also the most requested on the market. The guillotine shear is structurally composed of two blades, one fixed under the sheet metal and the other, upper, movable moved by hydraulic pistons powered by a hydraulic power unit (hydraulic compressor). All the shears are equipped with a device called blank holder, this allows the clamping of the material during the cutting phase, and by adjustable guides on which the sheet is made to slide.
The guillotine shears can be characterized by very different characteristics, with blade lengths of up to 6 m and cutting capacity up to sheet thicknesses of 20-30 mm. Usually, especially in large shears, the upper blade is not perfectly straight but is slightly curved or inclined in the longitudinal direction. These measures are intended to reduce the cutting effort by exploiting the scissor effect.