Stewo's high-quality wrapping papers are often printed with six colours (Source: Stewo)
As a manufacturer of high-quality wrapping paper and packaging, STEWO has the highest requirements on the production quality of its machines. Against this background, the Swiss company had its Lucerna Concorde Schiavi 6-coloor gravure printing press upgraded by Bobst with a Registron S6100-D register control system, and the latest drive and control technology.
The register control system reliably measures web stretch and tension and automatically triggers preventive corrections before register errors occur in the gravure printing process. BOBST has developed special algorithms that make this possible and are unique on the market in this form. Another reason why register control today can proactively exert a corrective influence on the printing process is the interconnectivity of the printing units and thus also of the Registron S6100-D system components. They communicate with each other.
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Most reliable readings
The performance of sensor technology plays a key role in controlling the colour register during gravure printing. It needs to be able to reliably read the print marks it uses to control the process – even under difficult conditions. The new register control’s RGB sensors give Stewo flexibility that they had never previously had. They can recognize the print marks straight away, even with low-contrast inks, metallic inks and coatings, and on hologram paper.
One example is an aluminum-coated wrapping paper that Stewo prints with six colours. In order for the sensors of the previous register control to detect the print marks on this material, a strip of white ink used to be printed in front of the aluminum coating. So in the end, they printed the paper with seven colours. Since their gravure press only has six printing units, it had to run through it twice. The aluminum coating is not even a challenge for the Registron S6100-D sensor technology. Therefore, the white stripe is no longer needed and the wrapping paper is produced in one process.
Less waste with more operating convenienc
Stewo processes several very special papers and prints – many of them in six colours. In some cases, the rear sides of the wrapping papers are also printed in multiple colours. In the past, this required the input of various parameters when setting the register control. Machine operators can now select the functions and parameters they need from drop-down menus and see at a glance the options available. The Registron S6100-D reduces the error possibilities of manual entries to a minimum.
Operator guidance is even simpler for repeat jobs. When creating new jobs, Stewo saves all register control parameters in reference jobs. They can subsequently be recalled at any time by pressing a key and the register control system adjusts automatically. But Stewo is also some minutes faster in printing new orders these days. The order sizes generally vary between 5,000 and 250,000 meters. Among them are many smaller orders. The time saved in the setup process has a particularly positive effect.
