Thickness Gauges for Rolling Mills and Strip Processing
Every micrometre matters when you are rolling metal strip. A deviation of just a few µm can mean the difference between material that meets specification and scrap that never leaves the mill. Vollmer thickness gauges give you the measurement precision needed to keep your production within tolerance — whether you are cold rolling foil at 0.003 mm or processing heavy plate at 24 mm.
Since 1963, we have supplied over 2,500 strip thickness gauges and more than 100 shape measuring systems to rolling mills in over 30 countries. Our contact, laser and X-ray gauges share a common principle: they measure absolute thickness, independent of alloy, so you always know the true dimension of your strip.
Why Vollmer Thickness Gauges
Thickness measurement in a rolling mill is not the same as measuring paint coatings or checking pipe walls with a handheld device. Strip thickness gauges operate inline, at speeds of up to 800 m/min, in environments with rolling oil, vibration, temperature swings, and mechanical stress. They feed directly into your Automatic Gauge Control (AGC) system and determine whether your thickness control loop is fast and accurate enough to produce strip within tolerance.
Vollmer gauges are built specifically for this environment:
- Absolute measurement, alloy-independent. Whether you are rolling steel, aluminium, copper, or special alloys — no material parameters need to be entered or updated. The gauges measure the actual physical thickness.
- Accuracy down to ±0.5 µm. Our contact gauges achieve repeatability of half a micrometre. Laser and X-ray systems match the accuracy of contact measurement but without physical contact.
- Proven reliability. Nearly 2,500 contact gauge systems have been put into operation over the past six decades. Many are still running today, forming an integral part of the measurement infrastructure in mills that demand the highest precision.
- Full integration. All systems come with PROFINET, PROFIBUS, hardware interfaces, and TCP/IP connectivity for seamless integration into your process control.
Different types of thickness gauges
We offer three fundamentally different measurement technologies. Each has its own strengths. The right choice depends on your material, your process speed, your rolling mill layout, and whether you need contact-based or non-contact measurement.
Contact Thickness Gauges
VBM, VBK & VBF Series
Contact gauges are the original Vollmer technology and remain the most precise method for measuring strip thickness. Two diamond-tipped transducers touch the upper and lower surface of the strip simultaneously. The distance between them is the true thickness — no calibration models, no alloy compensation, no assumptions.
How do contact-type thickness gauges work?
The diamond sensors physically contact both sides of the moving strip. Because the measurement is direct and mechanical, results are independent of material composition, surface finish, or oil film. When the gauge moves to its parking position during coil changes, the sensors touch each other and the system re-zeroes automatically.
Contact gauges are installed at all stages of the strip production process — on the cold rolling mill, on annealing lines, on finishing lines, in slitting operations, and in steel service centres. They are the reference standard in metrology labs and calibration facilities where absolute accuracy is non-negotiable.
| Parameter | VBF 1018 (Foil) | VBM 1063 (Standard) | VBM XX65 (Heavy) | VBK 512 (Wire & Narrow Strip) |
|---|---|---|---|---|
| Strip thickness range | 0,005–2,0 mm | 0,1–4,0 mm | Up to 9 mm | 0,1–9 mm |
| Accuracy | ±0,0005 mm | ±0,001 mm | ±0,001 mm | ±0,001 mm |
| Max line speed | 800 m/min | 800 m/min | 800 m/min | 800 m/min |
| Auto-zeroing | Yes | Yes (PLC recipes) | Yes (calibration plate) | Yes |
| Width measurement | — | Optional | Optional | Optional |
Laser thickness gauge
VTLG Series
The VTLG is a non-contact laser gauge built for measurement directly in the rolling mill. It is the only laser thickness gauge on the market designed to operate in the immediate vicinity of the roll gap during cold rolling — including foil rolling.
How do laser-based laser thickness gauges work?
Two synchronised laser sensors, mounted on a rigid C-frame, measure the distance from the strip surface to each sensor. The strip thickness is calculated from the known distance between the sensors minus the two measured air gaps. With an internal scanning rate of up to 80 kHz, the system delivers thickness data to your AGC within milliseconds.
Automatic self-calibration runs before every strip pass: the C-frame moves into the line and on its way measures the thickness of four captive, certified gauge blocks that represent the thickness spectrum of the mill. The gauge corrects itself continuously.
The VTLG is designed for cold rolling mills where non-contact measurement is required — either because the strip surface cannot tolerate physical contact, or because the gauge needs to operate inside the mill stand. It is equally suited for annealing lines, finishing sections, strip edge millers, and steel service centres.
| Parameter | VTLG (Standard) | VTLG 101/1 (Foil) | VTLG 1420/20 (Heavy) |
|---|---|---|---|
| Strip thickness range | 0,015–12,0 mm | 0,003–2,0 mm | Up to 20 mm |
| Accuracy | ±1 µm/mm | ±0,5 µm | ±5 µm |
| Scanning rate | Up to 80 kHz | Up to 80 kHz | Up to 80 kHz |
| C-frame air gap | 125 or 285 mm | 125 mm | 215 mm |
| Measuring depth | 400–1 200 mm | 400–1 200 mm | Upp till 1 480 mm |
| Self-calibration | Yes (4 gauge blocks) | Yes (4 gauge blocks) | Yes (4 gauge blocks) |
| Environmental protection | Air cleaning + temp. compensation | Air cleaning + temp. compensation | Air cleaning + temp. compensation |
| Interfaces | PROFINET, PROFIBUS, TCP/IP | PROFINET, PROFIBUS, TCP/IP | PROFINET, PROFIBUS, TCP/IP |
X-Ray and Isotope Thickness Gauges
For applications involving coated materials, multilayer composites, or situations where neither contact nor laser measurement is feasible, Vollmer supplies X-ray and isotope-based radiometric gauges. These systems measure thickness by detecting the absorption of radiation passing through the strip.
How do X-ray-based thickness gauges work?
An X-ray tube or isotope source sits on one side of the strip. A digital ionisation chamber detector on the other side measures the remaining radiation intensity after it passes through the material. Because different alloys absorb radiation differently, alloy compensation is applied — either using calibration plates, chemical alloy analysis from the customer's database, or by measuring absolute thickness with a small contact gauge at the start of each pass.
A distinctive feature of the Vollmer X-ray systems is the tungsten drawer: the radiation source is housed in a specially shielded tungsten container that can be quickly and safely removed from the gauge for maintenance or source replacement.
X-ray and isotope gauges are installed on cold rolling mills, tandem mills, skin-pass mills, annealing lines, pickling lines, and galvanising lines. They are particularly valuable for coated strip, multi-material laminates, and situations where non-contact measurement is required on materials where laser systems cannot achieve the needed accuracy.
| Parameter | Specification |
|---|---|
| Measurement principle | X-ray tube or isotope (Co-57, Am-241) |
| Detector | Digital ionisation chamber |
| Signal noise | Minimised through digital detector design |
| Alloy compensation | Calibration plates, chemical analysis, or contact gauge reference |
| Radiation source handling | Removable tungsten drawer for safe maintenance |
| C-frame width | From 120 mm (fits tight installations) |
| Control | PLC S7-based, open system integration |
| Evaluation | Industrial PC with diagnostics |
Contact vs. Laser vs. X-Ray
The table below compares the three technologies across the criteria that matter most in a rolling mill environment. Use it as a starting point — for a recommendation tailored to your specific line, contact our engineers.
| Criterion | Contact (VBM/VBK/VBF) | Laser (VTLG) | X-Ray / Isotope |
|---|---|---|---|
| Measurement principle | Direct physical contact | Laser triangulation (non-contact) | Radiation absorption (non-contact) |
| Accuracy | ±0.5 µm (best in class) | ±1 µm/mm strip thickness | ±0.1% of nominal thickness |
| Alloy dependent? | No | No | Yes (requires compensation) |
| Strip contact | Ja (diamantsensorer) | No | No |
| Scanning speed | Continuous | Up to 80 kHz | Continuous |
| Thickness range | 0,005–24 mm | 0,003–20 mm | Application-specific |
| Best for | Reference measurement, highest accuracy, AGC input | In-mill measurement, high-speed rolling, foil rolling | Coated strip, multilayer, where contact/laser not suitable |
| Environmental robustness | High (proven in mills for 60 years) | High (air cleaning, temp. compensation) | High (shielded radiation, digital detectors) |
| Calibration | Auto-zeroing on coil change | Self-calibration with gauge blocks before every pass | Calibration plates or reference gauge |
| Typical installations | Cold rolling, annealing, finishing, service centres | Cold rolling (incl. in-stand), annealing, finishing | Cold rolling, tandem, pickling, galvanising |
| AGC integration | Direct | Direct (millisecond response) | Direct |
When to choose contact: You need the highest absolute accuracy and your process allows physical contact with the strip. Contact gauges are the industry reference standard and the most reliable input for AGC systems.
When to choose laser: You need non-contact measurement, particularly inside the mill stand or close to the roll gap. The VTLG is the only laser system designed for this environment. Also ideal when strip surface must not be marked.
When to choose X-ray: Your strip is coated, multi-layered, or composed of materials where laser triangulation cannot deliver sufficient accuracy. X-ray gauges are also preferred where regulatory or process requirements favour radiometric measurement.
Not sure? Many mills use more than one technology in different positions on the same line. We help you determine the right combination.
Request for quotation
Contact us today for expert advice, a personalized quote, or a product demonstration. Let our experience and technical expertise guide you to the measurement solution that will elevate your quality assurance processes and drive operational excellence.