Thickness and width measurement on hot strip after pickling at Hoesch Hohenlimburg GmbH

The Hoesch Hohenlimburg works produce small lots for special purpose. The medium wide strips are treated in a continuous and push pickler after rolling. Production in the push pickler handles thicknesses of 1.5 mm to 17 mm, widths between 150 mm and 700 mm and lengths up to 2000 m.

Thickness measurement is done by two laser triangulation sensors, one above and one below the strip. A CCD line camera detects the angle to the laser spot, which changes with the distance to the surface. The sensor calculates the displacement from the measured angle. The strip thickness results from the difference of the displacement values and the offset of the two sensors.

Width measurement takes place by detection of the edges, using backlight for clear visibility. As the hight position is known from the thickness measurement, errors from vertical movement are compensated directly.

The operators get the results by visualisation in the control stand. Line graphics show thickness and width along the strip.