Machine with a galvanised eye on detail

Japanese steelmaker NKK has developed an automatic inspection tool for spotting surface flaws in its sheet steel products.

The NKK Delta Eye has been on trial for two years at the company’s Fukuyama plant. It claims the device can detect very fine flaws on the surface of steel strip and mark the defects before the coils are shipped to its customers.

An NKK spokesman said the system was tested on the hot-dip continuous galvanising line at the Fukuyama works.

‘The company is now installing additional systems at its number-three CGL and on the number-four continuous annealing line in the same plant. The new units are expected to be operational in early 2002.’

The Delta-Eye uses a polarised light source and three cameras. A computer linked to the cameras identifies the light reflecting on the surface of the steel strip. According to the company, the inspection system enables almost 100% detection of fine patterned flaws.

NKK said the system would benefit car manufacturers by reducing their workload in steel strip coil handling.

At present, without this flaw-detection system, manufacturers must shear off sections of the coil as defects are discovered.

The sheared sections are then considered waste, increasing material costs. Automotive sheets such as body panels, which require strict surface quality control, are currently inspected after pressing. Any pressed metal with a defect automatically becomes scrap as well.

The company hopes to expand applications of the NKK Delta Eye to other steel products, if the system is widely sold to other manufacturers.

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