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High Speed Hole Detection System to Verify Sheet Integrity as It Is Being Rolled

Enhancing Quality & maximizing yield in a manufacturing process

Unrelenting pressure from the market for defect free materials is compelling mill operators to introduce newer technology for higher in process detection of defects so as to produce defect free end products. Holes in steel sheets are one such defect whichare extremely difficult to detect due to their small size at high rolling speeds.

If passed on to automobile customers, holes cause critical equipment damage in their plant resulting in huge losses.

Increase in in-process detection of holes will reduce losses to automobile customers.


Principle of Operation

The De Hole is a line-mounted hole detectorthat senses the light passing through holes in the strip. It uses simple, rugged & sophisticatedcameras as photo detectors and a LED source for illuminating the strip.

The working principle is that any hole in an opaque material will allowlight to be transmitted through it. With an LED light source at the bottom side of the strip &appropriatemasking of ambient light, the cameras will sense the light and generate a signal.

A custom made software efficiently detects the location, size & shape of the hole on the sheet & presents it to the operator in real time.The software has ample capability to eliminate any other images that are not holes so as to avoid false alarms.



  • Capable of detecting holes as small as 0.5 mm2 at speeds as high as 240 mpm
  • Audio-visual alarm and line stop on hole detection
  • High speed, high resolution system for 100% hole detection
  • Low power, highly reliable LED strip backlighting for 24x7 operation
  • Efficient blob detection and contour tracing algorithm for faithful hole detection
  • Hole location and size information immediately presented to the operator & embedded in the log history of the coil



  • Real time detection of holes during the rolling itself
  • 100% coverage of sheet surface
  • Supports quality control & grading of sheets
  • Helps monitoring of the casting & rolling processes


Typical Applications

  • Cold Rolling Mills
  • Tinplate rolling
  • Aluminium rolling