In this guide, we examine how replacing contact wheel encoders with non-contact velocimeters improves cutting accuracy and repeatability on cut-to-length lines.
Accurate strip length and speed measurements are crucial for cost efficiency and quality optimisation in industries such as steel strip processing or wood-based panels. For years, many manufacturing processes have relied on contact wheels with encoders to measure the length and velocity of the product during production. However, in many cases, this approach does not provide the desired outcome because the product being measured is either:
- Soft
- Sticky
- Coated in oil
- Subject to rapid acceleration or deceleration.
These issues can lead to inaccurate measurements with contact wheel encoders, not to mention a host of other problems.
Increased Maintenance Costs
In some processes, the traditional contact wheels require constant maintenance to ensure reliable measurement — a problem caused by:
- Particle pick-up on the wheel, which, in turn, changes its effective diameter
- Wear and tear on the wheel or the supporting mechanism.
Production Waste or Product Givaways
For operations where a continuous product is cut to shorter lengths, the final lengths can very often be longer than they should be, resulting in the manufacturer giving away a percentage of their total yearly production.
The Underlying Flaw of Contact Wheel Encoders
Measurements conducted on various processes have revealed that it is common to find, that the typical measurement error with a contact wheel or rotary encoder is in the region of 2–5%. However, the error is not constant and will vary depending on the product being measured, the line speed and the surface coating.
This inconsistency makes it difficult for process engineers to account for errors in the control system. Therefore, the actual accuracy will vary depending on the product being produced.
On some process lines, an encoder is connected to the drive roll and used as the reference for length control. As the drive roll’s primary function is to push or pull the material through, there is always an inbuilt slip with this type of measurement method.
Non-Contact Laser Velocimetry: A Superior Solution to Speed and Length Measurement
Optical sensors like laser surface velocimeters provide precise in-line monitoring of length and speed during production processes. Laser speed sensors enable non-contact speed and length measurement, ensuring robust and accurate measurement — even in challenging environments or difficult-to-measure materials providing maintenance-free measurement suitable for automatic process control applications.
Related Reading: Non-Contact Laser Gauges Pave the Way for Higher Accuracy Length and Speed Measurements at Converting Plants
Enter the LaserSpeed® Pro Series of Gauges
The LaserSpeed® Pro gauges are a direct replacement for a contact wheel and encoder system, improving the accuracy and repeatability of the measurement.
Using the principle of Laser Doppler Velocimetry (LDV), LaserSpeed® Pro laser Doppler gauges achieve exceptional precision in measuring the velocity and length of moving surfaces or objects — all without physical contact.
Used across more than 20,000 installations in various in-process applications, the LaserSpeed® Pro gauges are adaptable to diverse production lines handling materials, including:
- Wires
- Cables
- Non-wovens
- Extruded products
- Paper
- Plastic films
- Gypsum Board
- Insulation materials
- Aluminium
- Steel.
Related Reading: In-Process Length Measurement and Shrinkage Control During Gypsum Board Production
Key Features of the LaserSpeed® Pro Gauges
As the LaserSpeed® Pro gauges are unaffected by the product’s surface condition, oil coating, or moisture level (i.e., whether the surface is wet or dry), their accuracy and consistency of measurement are much better than can be achieved by a traditional contact wheel encoder.
The LaserSpeed® Pro gauges can achieve an accuracy of better than ±0.03% and a repeatability of ±0.02%, regardless of the product or conditions. Their non-contact measurement method also ensures that the gauges require little to no maintenance, resulting in lower running costs.
For these reasons, the LaserSpeed® Pro is used on many cut-to-length applications where a flying shear or saw is used in-process to cut a continuous product to shorter lengths. If you’re unsure what LaserSpeed® Pro gauge to use in your facilities, read our comparison chart that breaks down the key features of the LaserSpeed® Pro lineup.
Related Reading: LaserSpeed vs LaserSpeed — Which Is Right for You?
How to Connect a LaserSpeed® Pro Gauge
The LaserSpeed® Pro gauges have a full quadrature output, similar to a regular rotary encoder. The user can configure the pulse rate to emulate the rate of the existing encoder. This means the existing control system does not need to be changed or reprogrammed.
Once connected, an existing production line will benefit immediately from the improved accuracy of using the LaserSpeed®. In some cases, a 2-5% improvement in cutting accuracy has been achieved using a LaserSpeed® Pro gauge.
LaserSpeed® Pro Gauge Applications
The LaserSpeed® Pro can be used on all types of cut-to-length lines to replace an existing rotary encoder, including:
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LaserSpeed® Pro Gauge Benefits
LaserSpeed® Pro gauges have no moving parts and are permanently calibrated, resulting in significant time and money-saving.
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What Our Customers Say…
| [quote]We wanted to improve the accuracy and repeatability of the automated length cutting operation on our Agnati corrugator. From the first meeting, it was clear that LIMAB have a lot of experience in this area and they replaced our mechanical encoder with a LaserSpeed®. The implementation of the LaserSpeed® has enabled us to achieve our original goal and it has ultimately improved the quality of the products that we are supplying to our customers.[/quote]
Shaun Coombs – Engineering Manager
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Follow the LIMAB UK Blog to find more insights on non-contact measurement in industrial settings.
You can also explore our range of non-contact speed and length measurement solutions and get in touch with our team for a consultation. For more information or to speak to one of our product specialists, contact us at hello@limab.co.uk or give us a call at 01823 668633.
