When the flexographic process was first used, the printing plates were originally made out of rubber stereos.  Today, most are made from ultra violet sensitive (UV) polymer resins.  The plates have a base-relief (raised image) that print directly to the substrate with a light ‘kiss’ impression (Flexography, 1997).  In the prepress operation the polymer plates are mounted with double-sided tape to the plate cylinders.  This allows for proofing of each cylinder prior to production to check for registration, and confirmation of client requirements and printer specifications.

Flexography uses a unique system whereby an anilox roll transfers ink onto the raised images on the plates.  The anilox roll is laser engraved such that the amount of ink delivered to the plates is measured by the screen size of the cells.  The coarser the cell count the larger and deeper the cells are engraved onto the roll.

Finally, flexography uses fluid inks that dry between the print stations of the press.  Both solvent and water-based inks are used.  The term substrate refers to the kinds of paper and plastic that can be printed-on, which is one of the beneficial features of flexography.

Flexography

The printing process called flexography is related to letterpress printing.  It uses relief-printing plates (photopolymer) with raised images.  Flexography today is able to print on more types of material than any other printing process.

As defined “flexography” is a method of direct rotary printing that uses resilient relief image plates of photopolymer material.  The photopolymer plates are affixed to a plate cylinder of various repeat lengths (sizes). The plates are inked by a cell structured ink-measuring roll (anilox roll) and with the aid of a sharp (doctor) blade and fast drying fluid inks, transfer the image from the plates onto any substrate that is absorbent or non absorbent.  Flexography is a rotary printing method in that for every revolution of the printing plate an image is produced on the substrate.

Generally there are 3 types of printing presses commonly used in the flexographic industry namely Stack, Inline (figure 3.4) and Central Impression (CI) (figure 3.5).  More recently digital press technology has evolved to start competing with traditional mechanical presses.