The gravure process is a high-quality, high-efficiency process used for package printing applications. Perfect register accuracy and easy and fast register setup are the keys to success. To meet these essential prerequisites, Windmoeller & Hoelscher developed EASY-SYNC, a preregister setting system, and Heliocontrol, a drive and register management system, for use on their HELIOSTAR gravure printing presses. Both systems are highly efficient tools giving perfect register and minimizing
both setup time and waste.
Excellent print results—the goal every printer wants to reach. To achieve this goal, many criteria must be met, and one essential criterion is to set and maintain the optimum print register. This means that the individual print cylinder must be perfectly matched with the print and register positions, which must be maintained at all speeds
The register-setting process consists of two steps: preregister (or startup register) setting, and print register setting during production. Ideally, after a job change and when a new web of material is fed into the printing press, both preregister and print register are set simultaneously and without waste.
EASY-SYNC Preregister Setting
For preregister setting on Heliostar rotogravure presses, W&H developed the new Easy-Sync system, which provides the operator with a rapid and efficient setup of the preregister. In the first step, the start point of the image to be printed (Zero position) is determined. In a second step, the start point on the material web (point of impression) is determined, and the print cylinder is positioned in a way that both Zero and impression points match exactly on top of each other.
Figure 1: The Easy-Sync marks to set the preregister are off the printed area.
How to Determine the Zero Position
The zero position of the print cylinder is determined by a laser scanning a mark off the printed area. Both mark and printing image are engraved on the cylinder surface so that no extra costs are incurred. The new preregister system, however, also allows for existing print cylinders without such special marks to be re-used. For this purpose, the cylinder is manually rotated into a zero position, which is then adopted by simply pushing a button. Any print cylinder can be used in the press without the need to mount “zero rings” or similar elements. The zero position is determined, automatically or manually, without a web passing through the machine and consequently, without any waste.
How to Determine the Point of Impression
Once the machine has recorded the Zero position of all print cylinders, the preregister system, in a second step, determines the point of impression roller diameters, changes in web tension and elongation of the substrate, drying temperatures and web travel—e.g., when using web turning bars, the web length and the distance between the impression points of the individual print stations may vary, and all these variables represent a major challenge when it comes to preregister setting. Since some of these variables are not known immediately, it is recommended to determine the distance between the individual impression points under production conditions.
To this end, the preregister system utilizes a standard adhesive tape that is applied onto the printing substrate and passes together with the web through all print stations. The print cylinder drives detect the position of the adhesive tape exactly when the impression points are reached. Immediately after detection, the angle between Zero position and impression point is set to preregister without the need to stop the machine.
System Benefits
Considering what has been outlined above, the new preregister system offers major technical and economic advantages when compared with manual preregister setting or other systems:
- There is no need for additional rows of marks. It is not an optical preregister setting system; optical systems need additional marks that must not superpose with other image information marks during the impression setting process for example.
- It allows the use of new and existing print cylinders.
- Transparent lacquers and cold seal compounds can reliably be handled.
- It is an inexpensive process since standard adhesive tape is used.
- Setup waste is minimized since the preregister is set immediately on the new web.
Optimum Print Register
Once the preregister has been set, the aim is to print the images exactly in relation to each other—at any speed, during role changes, and acceleration and deceleration of the rotogravure press.
Figure 2: Heliocontrol uses a super fast LED light sensor for perfect register control.
s outlined above, both preregister and print register are set simultaneously when a new web is fed into the printing machine. To achieve this, W&H gravure presses can be equipped with Easy-Sync and the new Heliocontrol drive and register management system.
When the preregister on one print station has been set, the new drive and register management system takes over without delay. It controls the register automatically and ensures exact print register for the entire job. Varying production parameters are allowed for and reliably corrected by continuous regulation and control of the print register.
Heliocontrol covers all operations in terms of register and drive management of the machine. With traditional concepts, the register controllers are integrated with the machine as separate systems, necessitating the matching of numerous interfaces, but the new drive and register management system directly acts on the print cylinder drives, offering the possibility of immediate intervention to correct the register and, consequently, achieve optimum print results
Operating Concept
The full integration of the new drive and register management system with the drive technology of the press translates into easy operation. The operator familiarizes quickly with the user interface, which is logically structured for intuitive operation. When a print job is stored, the data needed for register control is copied automatically into the job memory system so that data can be retrieved when a repeat job is run. On the basis of the known web parameters, the optimum settings for the register controller are generated automatically and there is no need for the operator to intervene.
Figure 3: Touch screen of the Heliocontrol drive and register management system for easy and intuitive operations.
Print Mark Sensor
The heart of the register controller is the print mark sensor, which identifies any existing type of wedge-shaped marks that are required to measure the circumferential and sideways register. When the machine is started, the sensor reads in all marks and displays them on the central operator terminal in their true color.
For color identification, the sensor is equipped with high-intensity, wear-free LEDs that are capable of identifying even low-contrast marks and displaying them with high contrast. Depending on the color of the mark, the light color offering the highest contrast is automatically selected. A super-fast, high-resolution signal processor determines the exact position of the printed image and transmits the data directly to the drive and register management system.
Advantages offered by the Heliocontrol drive and register management system include:
- Rapid register control within short intervals (within microseconds).
- Easy, intuitive operation and true-color display of register marks.
- System integration with the machine’s drive management without additional interfaces.
- Reduced job changeover times through easy storage and retrieval of previous job data.
- Drive parameters calculated based on the entered data of the substrate used.
- Drive and register parameters matched automatically, allowing a perfect register.
- Automatic light source selection for improved contrasts and optimized register mark representation using ultra-fast print mark sensor features.
Figure 4: The new modules are an integral part of the Heliostar rotogravure press installed
at the W&H Printing Technology Center in Lengerich, Germany.
Summary
The Easy-Sync and Heliocontrol modules for the preregister setting and precise register control during production are a perfect match and fully integrated with the Heliostar gravure press drive system. They allow a fully automatic startup of the printing press with maximum reliability, minimize setup time and waste, and guarantee a perfect register.
For more information, contact:
Heine Heininga, (US & Canada)
heine.heininga@wuh-group.com
1-800-854-8702
Clemens Brinkmann (All other regions)
clemens.brinkmann@wuh-group.com
+49 5481 14-0
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