Plate Geometry


Laser measurement systems for plate mills - flatness, plate geometry, thickness and length measurement

  • Full control
  • High througput
  • Complete quality control

Application Report Baoshan Iron & Steel Group, Co. Ltd., China


Measurement of plate geometry behind cooling bed.

By measuring the plate contour, the subsequent processing steps of crop cutting, trimming, slitting, and cutting-to-length are optimized. In addition to effective length and width, saber, necking, crop shape and side profile are taken into consideration to "best fit" the finished sizes into the plate, thereby achieving optimal yield. Crop cut optimization reduces scrap and increases yield and utilization.

For width measurement, laser distance sensors with special beam geometry are used to eliminate the influence of vertical plate movement on accuracy. The plate side profile is assessed by scanning triangulation sensors.

Head and tail shapes are measured by structured light imaging, projecting a laser line across the plate, and then using matrix cameras to assess the outline measurement. This eliminates parallax errors that would otherwise result from vertical plate movements.

Assessing the complete plate geometry allows to perfectly control the trimming cuts.
A monitor in the control pulpit graphically displays all results.



Thickness and length measurement at cut-to-length line.

As a final step in the production process, thickness and length of the finished plates are assessed for documentation and archiving. This allows the capability to prove compliance of the specifications at any time.

The thickness of the finished plates is measured optically by laser triangulation sensors located above and below the plate.

Each sensor measures the distance to the respective plate surface, and the thickness is calculated as the difference of the fixed sensor-to-sensor distance and the measured distances to the plate surfaces. Plate thickness is measured in 3 tracks. Transversal positioning of all sensors allows optimal location of the measurement tracks for any given material width. Having this capability, even slitted plates can be measured.

The thickness profiles of the plates are displayed on a monitor, with color-coded highlighting of tolerance violations.

A Laser Doppler gauge is used to monitor the length of the plates. Additional laser photocells are used to trigger the length measurement, further enhancing measurement accuracy.



Flatness measurement with LAP LevellerCheck behind hot leveller.

Measurement of flatness after levelling allows optimal setting of the hot leveller. Immediately after the passing of a plate the levelling result is available for evaluation and the plate levelling can be repeated if needed. The leveller setting can therefore also be optimized for the following plates and the flatness results will be used to permanently optimize the control model of the rolling train.

The plate flatness is measured in 11 tracks across the plate width by the LAP LevellerCheck. A speed signal from the leveller is used to allocate the crossprofiles along the plate length. Combining subsequent cross-profiles yields the flatness information. This information is graphically displayed in the control pulpit of the leveller as I-Units, as longitudinal and transversal profiles, as well as colored topographical maps.

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