Web Tension and Guiding
Integrated web tension control with fl exibility and accuracy
he hybrid web offset sleeve presses from DG press are used for a number of different products. For example, the DG-AUXO web offset press series can be used for printing relatively elastic materials, such as 15-micron OPP as well as for 700-micron cardboard. Such a large range of materials places high demands on the control of the web tension in the press. This ranges from 0.05 to 20 N per cm web width. When developing the DG-AUXO, much attention was paid to web tension management and keeping the setting options clear for the printers.
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Web tension in a printing press is created by small speed differences between the web feeding rollers. In older presses, these speeds are often fixed by the selected roller diameters. The consequence of these fixed diameters is that the range of materials to be printed is limited. Modern printing presses with servo drive technology do not have this limitation. Circumferential speeds of rollers can be set very accurately and adapted to the application and to the material to be printed. The basic principle of web tension by speed differences generally produces a stable register and a stable product length. However, due to the small speed differences, it can take a long time before the web tension becomes stable for example, at the start-up of a print job. As a result, an unnecessary amount of start-up waste is created. Finding the right speed settings is also not always easy and therefore increases the set-up time. In the web offset presses of DG press, the speed control is therefore often supplemented with a web tension control.
Figure 2 Example of a hybrid press confi guration
Figure 1 DG-AUXO hybrid web off set press
web tension is achieved much faster when starting up the press. Even when the press is at a standstill, the web is already at the correct tension, reducing start-up waste at print start. It also shortens set-up time because it is not needed to search for the correct speed setting. The integration of the web tension control into the press controls system ensures that the correct web tension is used at all times during the start-up cycle. Especially for hybrid web offset presses that have multiple web tension control areas along the line, this integration is even more important because otherwise the tension controls might influence each other.
This ensures that the web tension at the measuring roller remains stable by continuously monitoring and adjusting the speed of the web feeding rollers when necessary. The most common location for a web tension control is in the infeed unit of a web offset press, but for example also at a cooling roller or in an outfeed unit the web tension can be controlled provided that a web tension measurement is possible. This allows different web tensions to be set and monitored in various sections of the press, depending on the processes taking place in those areas.
To eliminate unnecessary start-up waste, DG press has developed and implemented several solutions. The most important is the integration of web tension control into the press control system, ensuring that the correct
The ability to accurately set roller speeds and adjust them based on web tension allows the DG-AUXO press series to print on a wide range of materials. However, having many options can also lead to longer setup times and a higher risk of errors. To prevent this, the settings that affect web tension are linked to the material being printed. Before starting a new job, the printer simply selects the material type from a database. The required speed and web tension values for that material are then automatically uploaded to the press control.
The engineers from DG press have extended the precise and accurate web tension control to complex web offset press configurations, integrating various other printing technologies, such as Flexo, Roto, Digital and Rotary Screen, to name a few. Interested in learning more about how the web offset presses from DG press can support your production needs? Contact DG press at
sales@dgpress.nl.
www.convertermag.com
April 2025
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