The process of producing an aluminium lithography strip is a complex one 1. The starting material is rolling slabs weighing about 14 t, more than 4 m long and with maximum width 2200 mm and thickness 600 mm. The slabs are hot-rolled in up to 20 passes, down to a plate approximately 100 m long, which is then reduced in the subsequent tandem line to thicknesses between 2 and 6 mm. The strip acquires its final desired thickness by cold rolling, which takes place at speeds up to 1500 m/min. A strip thickness control system is responsible for ensuring that the thickness tolerances are preserved over the entire strip length. Besides thickness, already during cold rolling a suitable degree of flatness must be achieved ji the requisite flatness values are to be attained in the subsequent straightening stage. For straightening, the strip is plastically elongated in a continuous process. This is done by passing the strip over straightening drums with different circumferential speeds. The degree of straightening required to achieve strip flatness is controlled via the difference in the circumferential speeds.
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