Flexo printing is a method of a rotating cylinder (printing plate cylinder)for every revolution of the printing plate cylinder an image is produced. If the image is stepped several times around a cylinder several images may be produced in one revolution. The plate cylinder will determine the size or sizes of the bag or pouch you are trying to produce.

Due to the nature of the printing process there are factors that don't exist with other print methods such as offset and gravure. Because flexographic employs a flat but flexible printing plate that is stretched around a curved cylinder and the image on the plate distorts when the plate is mounted on the printing cylinder. A circle shape for example distorts into an egg shape. The amount of distortion depends on many factors including cylinder size, plate size, and the amount of distortion depends on a number of factors, including cylinder size, plate size, and the amount of adhesive mounting tape used to attach the plate cylinder.

Another aspect of flexographic printing is the solids (line art) print differently than screens (dot patterns). That is because the printing plate is relatively soft and the ink on its surface must be pressed against the substrate to print. Thus the amount of pressure applied to the printing plate is critical For example more pressure that is needed to print a dense and heavy solid than to print a screen tint. The best of all worlds is to be able to have your screen printing plate and your solid printing plate on a different cylinder which in turns means another printing station.

Whichever method used to set up the printing press, one design implication must remain clear is that you may not be able to successfully print one color screens and solids on the same printing plate or printing station. Flexo is very different from offset printing where the solids and screens of a given color can be printed with a single printing plate.

Copyright (c) 2007 David Banig