February 14 2019
Flexographic printing is defined as a method of direct rotary printing that uses special rubber or photopolymer material. The printing plates are affixed to plate cylinders of various repeat lengths, which are linked by a cell structure (anolox roll) which is used to meter the flow of the ink on roll. It carries a fast drying fluid ink to the plates that print on a variety of substrates (paper / plastic / nylon / polypropylene / cellophane / LDPE / LLDPE / etc.).
Flexographic printing is a rotating method 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.
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 is needed to print a dense and heavy solid than to print a screen tint.
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. This is very different from offset printing where the solids and screens of a given color can be printed with a single printing plate.