Width measurement on flat metals
Single strip & multi-width slitting line Q&A

Range: Our width gauges can measure strip widths from a few millimetres up to 2,000 mm or more, depending on the model. Standard industrial ranges cover 50 mm to 1,600 mm.

Accuracy: Typical accuracy is ±0.05 mm for most flat metal applications, with repeatability better than ±0.02 mm. Higher accuracy models are available for narrow strip and precision slitting.

The system uses laser triangulation sensors (or high-resolution line-scan cameras) positioned on both sides of the strip. Each sensor measures the distance to the strip edge, and the width is calculated from the known baseline between the sensors.

For camber and wavy edges, we use a multi-point edge measurement — typically 2 to 5 measurement points per side — to compute an average edge position and filter out local anomalies. Burrs are detected as outliers and can be flagged separately.

Yes. The dual-sided sensor configuration measures both edges simultaneously, so lateral tracking (strip shifting left/right) is inherently compensated — the width is the difference between the two edge positions, independent of the strip's absolute position.

For vibration, we use high-speed sampling (up to 2,000 Hz) and averaging over a short time window. If vibration is severe, a stabilising roller or air cushion can be added before the measurement station.

Multi-width measurement is the simultaneous measurement of the width of each individual strip band (the "mult") produced by a slitting line. A single wide coil is slit into multiple narrower strips, and each strip must meet its own width tolerance.

Traditional single-width gauges only measure the total width of the mult or one strip at a time. Our multi-width systems use an array of sensors across the full width to measure every strip simultaneously, providing real-time width data for each band.

The number of strips depends on the total width and the minimum strip width. Our systems can measure up to 30 or more strips simultaneously in a single slitting line.

Minimum resolvable strip width is typically 10 mm, but narrower strips (down to 5 mm) can be measured with a high-resolution configuration. The sensor spacing and edge-detection algorithm determine the minimum width.

The system identifies each strip by detecting the gaps (slit gaps) between strips. Each gap is a low-reflection or no-signal zone between two adjacent strips.

If a strip is missing (e.g., due to a break or cobble), the system detects the absence of expected edges and flags the event. The software can also track strip count and reject the coil if the number of strips does not match the recipe.

Our width gauges handle line speeds up to 600 m/min (and higher for special configurations). Accuracy does not degrade with speed because the measurement is a snapshot of the strip edges at a given instant — the sampling rate is high enough (up to 2,000 Hz) to capture a clean profile even at maximum speed.

At 600 m/min (10,000 mm/s) and 2,000 Hz, the strip advances 5 mm between samples, which is more than sufficient for accurate width averaging.

Light oil films and coolant residues generally do not affect laser triangulation sensors, as long as the strip surface is not heavily contaminated or covered with thick emulsion. Heavy oil or foam can scatter the laser and cause dropouts.

For applications with heavy oil, we recommend an air knife or air wipe before the measurement station. The sensors themselves are available with air purging to keep the optics clean.

Flatness: The strip should be reasonably flat in the measurement zone. Excessive cross-bow or twist can cause the edge to appear at an angle, but our multi-point edge detection compensates for moderate deviations.

Edge quality: Slit edges with burrs or roughness are acceptable; the system detects the outermost edge and can filter burrs using outlier rejection.

Temperature: Strip temperature up to 80°C is acceptable with standard sensors. For higher temperatures, we offer cooled housings and remote sensor heads.

Vibration: The system is mounted on a rigid frame; if the strip vibrates vertically, the sensors have a sufficient depth of field to maintain measurement.