Roll Measurement Systems for Roll Grinding Machines
Strip quality in a rolling mill starts at the roll grinder. If the roll profile, roundness and eccentricity are not within specification before the roll enters the mill, no amount of AGC tuning will fully compensate. Every micrometre of crown error becomes a flatness defect. Every micrometre of eccentricity becomes a periodic thickness variation.
Vollmer's roll measurement systems give you the data to grind rolls right the first time. The VSL series measures form, diameter, roundness and eccentricity in-process during grinding — with ±1 µm precision and a bi-directional CNC link that feeds corrections directly into the grinding program. The VFR straddle gauges provide fast, portable offline verification for rolls on the grinder, on the floor, or anywhere in the roll shop.
More than 100 roll grinding machines worldwide are equipped with Vollmer roll measurement systems.
Why Roll Measurement Matters
A roll is not a simple cylinder. It has a designed crown profile — a carefully calculated shape across the roll body that determines the thickness profile and flatness of the strip. It has a roundness specification — how close to a perfect circle the cross-section is at any point along the body. And it has eccentricity and run-out values that determine whether the roll will produce periodic disturbances during rolling.
When these parameters drift out of specification, the consequences appear in the strip:
Crown error → flatness problems If the roll profile deviates from the target crown, the strip develops edge waves (crown too high) or centre buckles (crown too low). These shape defects cannot be corrected downstream.
Taper → wedge. If the roll diameter differs from one side to the other, the strip comes out thicker on one side — a wedge defect that affects downstream processing and may result in rejected coils.
Eccentricity → periodic thickness variation. If the roll is not perfectly round, every rotation produces a periodic thickness bump in the strip. This shows up as a characteristic frequency in the thickness signal — often detectable with FFT analysis — and can cause vibration, chatter marks and increased scrap.
Over-grinding → shorter roll life. Without accurate in-process measurement, operators tend to over-grind to ensure the roll is within specification. Every unnecessary pass removes material and shortens the roll's service life.
Precise roll measurement at the grinder eliminates these problems at the source — before the roll enters the mill.
VSL Series — In-Process Roll Measurement During Grinding
The VSL is Vollmer's automatic roll measuring system for use directly on the roll grinding machine. It measures the roll during and between grinding passes, giving the operator — and the grinding machine's CNC — real-time data on every critical parameter.
What the VSL Measures
| Parameter | Precision | Description |
|---|---|---|
| Crown profile | ±1 µm | The shape of the roll body from edge to edge — flat, convex, CVC, cosine or compound crown |
| Diameter | ±1 µm | Absolute diameter at any point along the roll body |
| Roundness (TIR) | ±1 µm | Total Indicated Runout — how close the cross-section is to a perfect circle |
| Eccentricity | ±1 µm | Deviation of the roll centre from the axis of rotation |
| Taper | ±1 µm | Diameter difference between the two ends of the roll body |
| Height alignment | Measured before grinding | Vertical position of the roll relative to the grinding wheel — used for set-up |
| Lateral alignment | Measured before grinding | Axial position of the roll — used for set-up |
How the VSL Works
The VSL gauge is mounted on the grinding machine and traverses the length of the roll body. As it moves, it continuously records the roll diameter at every position. With the roll rotating, it captures the roundness and eccentricity at each measurement station. The data is processed in real time and displayed on the operator's screen as a profile graph, roundness polar plot and deviation table.
The measurement happens during and between grinding passes — the operator does not need to stop the machine, dismount the roll, or bring it to a separate measurement station. The VSL measures in the same set-up as the grinding, which eliminates re-chucking errors and saves time.
Bi-Directional CNC Communication
If the grinding machine has a CNC controller, the VSL communicates bi-directionally: it sends the measured profile to the controller, and the controller uses it to update the grinding program automatically. If the measurement shows that the crown is 2 µm too high on the left side, the CNC adjusts the next pass to remove exactly that amount — no manual correction, no guesswork.
This adaptive, closed-loop grinding reduces the number of passes needed to reach specification, reduces over-grinding, and produces more consistent results from roll to roll and from operator to operator.
Machine Compatibility
Vollmer produces VSL systems for both major types of roll grinding machines:
Carriage-type (bench-mounted) grinders — where the roll moves along the grinding wheel. The VSL gauge is mounted on the carriage and traverses with the roll.
Support-type grinders — where the grinding wheel moves along the stationary roll. The VSL gauge traverses independently along the roll body.
The system is suitable for a broad spectrum of roll diameters — up to 2,000 mm — and roll body lengths beyond 12 metres. The Side-Shift option enables the gauge to automatically avoid chocks, roll neck attachments and other obstructions during traversal.
Nyckelspecifikationer för VSL
| Parameter | Specification |
|---|---|
| Measurement precision | ±1 µm (form, TIR, eccentricity) |
| Roll diameter range | Up to 2,000 mm |
| Roll body length | Beyond 12 m |
| Grinder types | Carriage-type and support-type |
| CNC interface | Bi-directional (read/write) |
| Side-Shift | Automatic obstruction avoidance |
| Pre-grind alignment | Height and lateral measurement for fast set-up |
| Data interfaces | Industry 4.0-ready, open data interfaces for cloud analytics and predictive maintenance |
VFR Straddle Gauges — Offline Roll Measurement
The VFR traversable straddle gauges are portable measurement devices for offline roll verification. They are placed directly onto the roll — on the grinder, on the floor, or at any location in the roll shop — and moved manually across the roll body, measuring the profile from crown edge to crown edge.
When to Use VFR
Incoming inspection — Verify a roll's profile and condition before it is chucked into the grinder. Detect problems (damage, uneven wear, thermal deformation) before grinding begins.
Final verification — Confirm that the ground roll meets specification before it is released to the mill. This independent check complements the in-process VSL measurement.
On-floor measurement — Measure rolls that are stored in the roll shop, in transport cradles, or at the mill stand — anywhere the roll is accessible. No grinding machine required.
Troubleshooting — When a strip quality problem is traced back to roll geometry, VFR provides the data to confirm or rule out specific rolls.
How the VFR Works
The straddle gauge sits on the roll body, resting on the roll surface with two contact points on either side of the measurement sensor. As the operator moves the gauge along the roll body, the sensor records the profile — the diameter variation from one end to the other. The result is a continuous crown profile graph, equivalent to the profile measured by the VSL, but captured offline without a grinding machine.
VSL + VFR: Online and Offline Working Together
The full value of Vollmer's roll measurement portfolio comes from combining in-process and offline measurement:
Before grinding (VFR): Inspect the incoming roll to understand its current condition. This data helps the operator plan the grinding — how much material needs to be removed, whether the roll has damage or thermal deformation that needs to be addressed first.
During grinding (VSL): The VSL measures the roll in real time, feeding corrections to the CNC. The grinding converges on the target profile with minimum passes and minimum material removal.
After grinding (VFR): An independent offline verification confirms that the finished roll meets specification. This measurement is independent of the grinding machine's set-up, providing a separate quality record.
In the roll shop (VFR): Rolls in storage can be checked periodically for thermal drift, relaxation or handling damage before they are scheduled for the mill.
Request for quotation
Vollmer’s Roll Measurement portfolio unites online and offline gauges to secure every critical roll gap measurement and roll measure parameter. The combination of ± 1 µm precision sensors, proven software, and modular delivery cuts set-up time, stabilises product quality and reduces total cost per tonne.