Strip thickness

Laser optical thickness measurement

Contact-free and irrespective of the alloy

The VTLG laser-optical thickness measuring systems combine the highest precision with a rolling mill-oriented design. With a measuring precision of up to ± 0.5 μm and a scanning rate of up to 80 kHz, they offer the precision and speed necessary for control of the strip thickness.

VTLG systems operate at strip temperatures of up to 180°C – even with dense rolling oil mist and despite of emulsion on the strip. They are therefore the only laser thickness gauges that can be installed in the immediate vicinity of the rolling gap, thus opening up completely new possibilities for our customers for the control of their processes.

As with our contact gauges, they measure the thickness irrespective of the alloy – ideal preconditions for use in the rolling mill, but also on the pickling line, in the finishing section, on the strip edge miller or in the steel service centre.

At a glance:

  • µm precision
  • Irrespective of the alloy
  • Contact-free and from a safe distance
  • Extremely compact
  • Precise even with poor visibility

Many of the systems have proven themselves under conditions that for a long time made the use of optical methods seemingly impossible – for example in the cold rolling of high-strength strip, where dense rolling oil mist is created. But the VTLG operates reliably even then.

We manufacture the VTLG thickness gauges with a measurement throat depth of up to 1,480 mm and a measurement resolution of 0,1 µm so that they can measure transverse thickness profiles even on wide strips.

The VTLG 101/1 has been specially designed for the cold-rolling of foils with thicknesses between 0.003 and 2.0 mm, and is the only laser measuring system available on the market that can be installed very close to the roll gap even when rolling foils. It operates with an absolute measuring precision of ± 0,5 µm.

Simple and safe

The automatic air cleaning system for the measuring window and beam path and the innovative temperature compensation ensure the highest precision even under difficult environmental conditions.

The technology

Thickness measurement is based on laser triangulation. On the upper and lower sides of a sturdy C-frame is a compact measuring head which both transmits the measurement beam and receives the reflected light. Both sensors measure the distance from the strip surface from their perspective. The thickness of the strip is then calculated from the measured distances and the distance between the two sensors.

With an internal scanning rate of up to 80 kHz, the scalable analog output provides the input signal for the high-speed thickness control within milliseconds.


Permanently precise

When the C-frame moves out of its parking position into the measuring position on the strip, the measuring system passes through the permanently installed adjustment station. There the system measures the inserted captive DAkkS-certified gauge blocks that represent the whole measuring range of the respective application. The VTLG calibrates itself and makes any necessary corrections automatically. This ensures that the system measures accurately at all times.