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CI flexo printing process

BOBST has actively contributed to the development of the printing industry over a period of 125 years and today its Fischer & Krecke range is dedicated to producing web-fed, CI flexo printing presses for the flexible materials industry.

Cutting edge technology and high manufacturing standards ensure premium print quality and long-lasting value. With their varied repeat lengths and medium to super-wide printing widths, BOBST CI flexo presses meet the requirements of the most demanding package printing applications.

Flexographic printing

Flexographic printing is a method which uses a flexible relief plate to print onto a substrate, which may be a wood-pulp based, synthetic, or laminated material. Such substrates may include:

  • Films such as polyester, OPP, nylon, and PE
  • Papers
  • Carton board
  • Non-woven textiles
  • Coated or un-coated liner board

Today's flexo printing presses use photopolymer printing plates containing a mirror relief image of the required print. The raised areas on the plate have ink applied to them by an anilox roller and then transfer it onto the substrate.

Press types and process description

There are three different architectures for flexographic printing presses, depending on the arrangement of the printing units, which may also be called printing decks:

  • Central impression, or CI, flexo presses: where the decks are arranged around a single, large diameter impression cylinder
  • Stack flexo presses: where the decks are stacked one above the other
  • In-line flexo presses: where the print units are laid out horizontally in a line

In a modern flexographic press, each print unit comprises of:

  • Anilox roller: a cylinder of highly engineered metal and/or ceramic, which is laser engraved with minute cells of a given angle, line screen, and volume to deliver the required fineness of print
  • Chambered doctor blade system: a device that delivers a measured amount of ink to the cells of the anilox roller
  • Plate cylinder: which the printing plate is mounted upon
  • Impression cylinder: a sleeve that supports the substrate as the printing plate is pressed against it
  • Inking system: ink holding tank, ink pump with delivery and return ink lines, plus other elements to ensure the maintenance of ink supply and viscosity

Between the print units, driers may be installed so that subsequent colors can be applied to the substrate without merging into those previously printed. These driers may utilize hot air, infra red or ultra-violet light, depending on the application.

During the printing process, the ink is pumped into the ink chamber of the doctor blade system. Two blades within the ink chamber, the barrier blade and the doctor blade, seal either end and confine the ink to the chamber while it is in contact with the anilox roller. As the anilox roller rotates, the cells in contact with the doctor blade system collect ink, and then any surface excess is removed as the roller passes under the doctor blade. As the anilox rotates, its surface comes into contact with the raised areas of the printing plates mounted on the plate cylinder, transferring the ink. The printing plate then rotates and transfers the image onto the substrate.

Applications

The applications of CI flexo printing include the manufacture of flexible and aluminum packaging, pre-print liners and labels, plastic and paper bags, heavy duty paper sacks, and shrink sleeves.

Process advantages

The flexo printing press offers users a number of advantages, not least that the most readily available inks are water based and therefore easier to work with and faster to dry.

The manufacture of flexo printing plates is relatively straightforward and the process is also easily adaptable to a wide range of substrates.

The high print quality and registration accuracy of CI (Central Impression) flexo printing is well established, while recent developments among in-line flexo printing presses have meant that flexographic presses are now able to compete against gravure and litho machines in areas such as fiber-board packaging manufacture.

BOBST expertise and knowledge

BOBST, with its Fischer & Krecke products, is the recognized technology leader in CI flexo printing for the flexible material and pre-printed linerboard industries.

Beyond the well-equipped standard configuration, all Fischer & Krecke flexo presses can be fitted with a multitude of additional technical options which adapt the press to specific production requirements and to the competitive advantage of users.

Innovative handling and maintenance concepts guarantee a unique degree of machine availability and reliability while minimizing the risk of operating errors. Additionally, every machine is supported by a comprehensive range of technical service and customer support solutions available from BOBST’s world-wide support network.

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