VTLG
Laser Thickness Gauge
Non-contact thickness measurement—stable even in the harshest cold-rolling mill environments
Summary
VTLG combines laboratory precision with shop-floor robustness: non-contact, fast, and alloy-independent thickness measurement—even where optical methods were previously considered impossible. If you want to raise quality, reduce penalties, and ensure stable control, VTLG is a future-proof choice.
Why VTLG
- Alloy-independent, absolute measurement — no radiometric errors from varying alloy content.
- Built for cold rolling mills — stable measurement on oiled or wet strip (up to approx. 500 mg/m² per side) and insensitive to strip vibrations.
- High precision in real time — internal scanning up to 80 kHz provides a fast analog output for millisecond-speed control.
- Self-calibrating & temperature-compensated — passes a fixed reference station with DAkkS-certified gauge blocks and compensates for temperature to ensure reliable values over time.
- Proven in the field — more than 100 VTLGs in cold rolling mills worldwide and documented installations in highly vapor-laden 20-high mills.
How it works
Compact laser sensors are mounted on the top and bottom of a rugged C-frame to emit the measuring beam and receive the reflected light. Each sensor measures the distance to the strip surface; thickness is computed from the two sensor-to-surface distances and the known spacing between the sensors. The result is filtered with a selectable averaging time (Ti 1–1000 ms) and delivered as a scalable analog/digital signal to the line’s control system.
As the C-frame moves from parking to measuring position, it passes a permanent reference station. There, the gauge automatically checks and corrects itself against mounted, DAkkS-certified gauge blocks that cover the application’s full measuring range. Together with automatic air purging of the windows and beam path and the built-in temperature compensation, top accuracy is maintained even in harsh environments.
Performance
- Accuracy: up to ±0.5 µm (longitudinal profile) at Ti ≥ 10 ms.
- Resolution: down to 0.05–0.1 µm (model-dependent).
- Scanning rate max 80 kHz.
- Strip temperature: up to 180 °C.
- Strip speed: >0–2000 m/min.
- Spot size: approx. 0.1 mm.
- Protection rating: C-frame IP65; controller IP55.
- Interfaces: PROFINET, PROFIBUS DP, TCP/IP, plus analog/digital I/O; logging (VRecoS) and statistics (VGraph) as options.
Models & applications
- VTLG 101/1—foil & thin strip: Optimized for 0.003–2.0 mm and can be installed very close to the roll gap, even in foil rolling. Provides absolute accuracy of ±0.5 µm.
- VTLG xx6/6, xx12/20, xx20/20—wider and thicker strip: Measuring ranges up to 20 mm, resolution typically 0.1 µm, and throat depth up to 1480 mm for cross-profile.
Typical positions in the line: directly in the mill stand, on the pickling line, in the finishing section, at edge milling, or in service centers—thanks to non-contact, alloy-independent measurement that is immune to oil mist. (Basis: design and function descriptions in the datasheet and field applications.)
Proof from the field
In a documented 20-high mill at Outokumpu, X-ray gauges were replaced by VTLG to become independent of alloy variations. The extremely vapor-laden operating conditions were handled with protective solutions, and VTLG delivered stable measurement close to the process (see photos on pp. 24–27 of the presentation material). Today there are 100+ VTLG installations in cold rolling mills worldwide.
Integration & operation
VTLG is delivered with motorized horizontal/vertical positioning (±1 mm accuracy) and can traverse across the strip for cross-profile scans. The system connects easily to existing control systems via industrial fieldbuses or analog/digital signals. Compressed-air and environmental requirements are specified in the datasheet (DIN ISO 8573-1).
Request for quotation
Want the right model recommendation or a technical review of your line? Contact us and we’ll propose a configuration based on your measuring range, strip width, and installation space.