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LDV Laser- und Lichtsysteme GmbH: Laser makes chatter and roll marks visible

LDV Laser- und Lichtsysteme GmbH has developed a visual laser-based inspection system for work rolls, which makes smallest irregularities of the roll surface visible. The system ensures that defects on the surface of rolls are detected during roll grinding. This prevents any improperly repaired rolls from damaging the strip.

The work rolls in rolling stands are crucial to the production process and the quality of the metal strip being rolled. Work rolls reduce the strip thickness and give the strip surface a clearly defined structure.

If in the roll grinding process not all defects are eliminated from the roll surface, these defects will later on leave marks on the strip – which usually show in the form of chatter or rolling marks. In the past, such defects were only detectable at the end of the rolling process by automatic or visual inspection of the rolled strip, or often at an even later stage – in the laboratory.

Now, the iLux roll inspection system makes defects on the roll surfaces visible as early as during grinding in the roll shop. This has the advantage that the defects can be securely removed before the rolls are reinstalled in the rolling stand.

The principle is strikingly simple: The laser module illuminates a narrow section of about 70 mm length on the roll surface. The light band is projected onto a white surface, which shows an image of the roll surface structure with up to 40 times magnification. Any irregularity in the surface structure immediately leaps to the eye.

Defects on the roll surfaces can be detected at a glance and the operator immediately sees whether he has ground off enough material to remove all defects or whether he has to continue grinding.

The iLux system also has a positive effect on the service life of the rolls. So far, it was necessary to remove rather more than less material from the roll surface to make sure that all defects were completely gone. Now, it is sufficient to remove just as much material as needed to eliminate the defects. This saves roll material and markedly extends the lives of the expensive work rolls.

LDV designed the first iLux systems installed in roll shops for roll diameters between 40 and 100 mm and roll barrel lengths of up to 850 mm. The system can be adjusted to other roll dimensions on demand. For rolls of larger diameters, the iLux LightBox has proved to be a highly successful option.