Rotogravure is a direct printing process based on the transfer method. It is used for printing on wood-pulp fiber based, synthetic, or laminated substrates, such as: films (polyester, OPP, nylon, and PE) paper, carton board or aluminum foil.
A modern rotogravure printing press has a laser engraved printing cylinder, with minute cells that retain ink and whose size and pattern reflect the image. The printed image results out of forcing these cells to transfer the ink directly on the substrate combining pressure and capillary action.
Commonly known as gravure printing, the process is used in manufacturing packaging (food and non-food), labels, transfer printing, wall coverings etc. It also works just as well in further applications: security printing, industrial and tobacco segments of industry.
Anyway the whole process is carried out by rotogravure printing presses and the following lines represent an attempt to “see” how do they work? But first let us get an idea on the components of such a machine. The layout follows an in-line arrangement, along a horizontal plane, are installed the required number of printing units.
Any conventional rotogravure printing press is made of: a printing cylinder – engraved with the image to be printed (which may be a seamless tubular sleeve or full cylinder, made from either steel, aluminum, plastic, or composite material); the doctor blade device -removes ink from the non-engraved portions of the printing cylinder and the excess ink from the engraved sections; the Impression roller, whose primary purpose is to press the substrate against the printing cylinder (a rubber covered sleeve mounted on a steel mandrel) the inking system made of an ink pan, ink holding tank, and ink pump with supply and return ink pipes and the drying system – a chamber whose purpose is to dry the ink on the substrate before going through the next printing unit.
The process starts with the printing cylinder rotating in the ink pan. Here the cells engraved on it fill with ink. Then, the doctor blade removes any excess ink, as the cylinder rotates clear of the ink pan. Further, the cylinder “gets in touch” with the substrate and it is pressed against it by the rubber covered impression roller.
By means of pressure exerted on the roller, along with the capillary draw of the substrate, occurs the direct transfer of ink from the cells in the printing cylinder to the surface of the substrate. The moment the printing roller rotates back into the ink pan, the printed area goes through a dryer and to the next printing unit, which usually is a different color or a varnish or coating.
The right color to color registration is possible through automatic side and length register control systems. In the case of web-fed printing presses, after applying each color and coatings, the web is ‘rewound’ into a finished roll.
The process allows consistent ink transfer in a wide density range, at high speeds, being suitable for applications that demand high image quality (publishing, packaging, labels, security print, and decorative printing).
The printing cylinders’ long-lasting nature makes rotogravure printing the best process because it provides high quality print on very long or repeating runs, resulting in cost advantages. But if you would like to go further with the cost advantages of your service developments why not consider a used rotogravure press?
If the machinery is completely refurbished and runs perfectly the results are the same. The best models and manufacturers are one click away: http://usedpresses.org/used-rotogravure-printing-machines/.
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