Flexo printing - folding-gluing inline process

In-line flexo folder gluers, or FFG’s, represent a complete box making solution. With close to a century of experience in the production of such equipment, BOBST is perfectly placed to deliver the machinery that corrugated packaging manufacturers around the world need.

Increasingly, RSC makers need their flexo folder gluers to deliver high quality graphics and FFG range of BOBST has been at the forefront of developing systems to achieve this, including vacuum transfer systems and the ability to handle coated boards.

Along with paying close attention to ensuring the quality of the finished product, Bobst Lyon designers have worked continuously to incorporate features which ensure ease of use and the highest possible productivity rates, especially if the boxes are destined for machine erection or are made from light weight papers.

Flexo printing and folding-gluing inline process

The basic purpose of the flexo folding and gluing inline process is to produce regular slotted cases (RSC's) from sheets of corrugated board, in a single pass. Laid out horizontally as an integrated system, a flexo folder gluer will incorporate a number of complimentary units that feed and flexo print the board, in several colors, then die-cut, fold, and glue it to produce a finished box.

Flexo-Folder-Gluers (FFG)

The main elements of an inline flexo folder gluer are:

  • Feeder: which stacks and squares the incoming board before introducing it into the machine at the required speed
  • Several flexographic print units, one for each color required
  • Creasing and slotting units to cut and score the case, allowing the formation of panels, flaps and the glue tab of the box
  • An optional rotary die cut unit which will create any complex die-cut shapes required
  • Folder-gluer section: to apply adhesive to the glue tab and fold part of the board along a crease line to meet it
  • Counter-ejector: stacks the cases in the required quantities according to the thickness of the material. The counter ejector delivers a bundle of completed cases ready to be strapped and palletized manually or with an automatic palletizer

Flexographic printing units

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.

Process description

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, 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.

By carrying out these processes inline users get a simplified supply chain, savings on waste and energy, and a much faster time-to-market.

BOBST expertise and knowledge

Today’s market requirements for high quality graphics on packaging, together with a trend towards more sophisticated packaging shapes, has led BOBST to develop additional functionalities within the flexo folder gluer range. These include 'high graphics' configurations for the printing of four color process on coated paper and larger die-cutting units for the production of display or shelf-ready-packaging.