Paper, printing and converting

In the paper, printing and converting sectors, measuring the speed and length of web materials is decisive for cut-to-length, metre counting and machine synchronisation. ASTech optical speed meters and encoders measure without contact on paper, board, film and laminates, eliminating the slippage and wear typical of measuring wheels.

This section brings together practical solutions for converting and printing lines. For the operating principles, please refer to the Technologies section; the other application areas are described on the Steel and metals, Wood, furniture and flooring and Automation and process pages.

The requirements of converting and printing

Converting lines process thin, flexible and sometimes delicate materials, often at high speeds. In this context a contact measuring wheel can mark the surface, slip on smooth films or wear out quickly, introducing errors into the length count. Yet in precisely these operations the accuracy of the metres is crucial: it determines roll length, the number of pieces and correct print registration. A non-contact measurement is therefore the natural choice.

The VLM500 measures up to 50 m/s with an uncertainty below 0.025 %, while the VLM60, a compact optical encoder, replaces measuring wheels directly and measures down to 0 m/s. Both handle matt, glossy or printed surfaces thanks to automatic exposure and brightness control.

Typical applications

Optical solutions are used on rewinders, slitters, laminators, printing presses and lines producing bags and labels. In each of these applications, speed and length measurement feeds cut-to-length, piece counting and unit synchronisation. On a rewinder, for example, accurate metre counting determines the exact length of the finished roll.

Advantages in converting

• Non-contact measurement on paper, board, film and laminates
• No marking of the surface of delicate materials
• Accurate metre counting for rolls, labels and bags
• Direct replacement for measuring wheels (VLM60)
• Integration with slitters, rewinders and printing presses

Length measurement for cutting and counting

Optical length measurement, obtained by integrating speed, directly governs the cut-to-length and counting functions. In practice, every roll, sheet or bag is produced at the correct nominal length, reducing scrap and disputes. Since the measurement is free of slippage, the tolerance also remains constant throughout the production run, with no frequent recalibration. For this reason converters increasingly adopt optical speed meters as their standard.

A further advantage concerns registration on printing presses: a stable speed measurement helps to maintain synchronism between the printing units, improving colour register quality. Material and ink waste during start-up are consequently reduced.

Integration and reliability

ASTech instruments provide incremental encoder outputs, an analogue output and the main fieldbuses, for straightforward integration with PLCs and counters. The absence of contact parts also eliminates wear-related maintenance, increasing line availability. Ultimately, the optical solution lowers the total cost of operation and improves finished product quality — a decisive advantage in the competitive converting and printing markets.

Materials and surfaces in converting

Converting handles an enormous variety of materials: coated and uncoated papers, board, polyethylene and polypropylene film, thin aluminium, laminates and non-wovens. Each of these materials has a different surface in terms of colour, gloss and transparency. Thanks to automatic adjustment of exposure time and brightness, the optical speed meter adapts to all these cases without manual calibration, keeping accuracy constant even when the reel or the job changes.

On transparent or very glossy films in particular, where measuring wheels tend to slip, optical measurement remains fully reliable. This makes it possible to standardise on a single type of sensor across lines running heterogeneous materials, simplifying spare parts and staff training.

Reducing start-up waste

A significant share of waste in converting and printing is generated during start-up, when the line accelerates and the parameters are not yet at steady state. A responsive, stable speed measurement, with an update time below one millisecond, allows the control system to bring the line quickly to optimum conditions, reducing wasted material. Overall yield improves as a result, especially on production runs with frequent job changes.

Product quality and fewer complaints

In converting and printing, the declared length of a roll is a contractual commitment to the customer: shorter rolls generate disputes, longer rolls give material away. Accurate optical measurement keeps the length within tolerance repeatably, aligning what is produced with what is declared. Complaints decrease as a result and supply reputation improves.

Line speed and productivity

Modern converting lines aim at ever higher speeds to increase productivity. As speed rises, however, measuring wheel slippage grows and the length error worsens. The optical speed meter, measuring without contact, instead maintains the same accuracy at any speed, up to 50 m/s with the VLM500. For this reason it effectively enables higher productivity without sacrificing counting accuracy.

One standard for many machines

Adopting a single type of optical speed meter on rewinders, slitters and printing presses simplifies spare parts management, staff training and maintenance. In other words, the same measuring principle becomes a company standard, reducing complexity and indirect costs. RODER technical support helps define the optimum configuration for each machine.

Frequently asked questions