Understanding Flexographic Printing

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 inked 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.
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. This is very
different from offset printing where the solids and screens
of a given color can be printed with a single printing
plate.

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David Banig has been in the Flexographic printing industry
for 32 years and has had various patents along with hands
on experience. If you are looking for someone to improve
your packaging P&R Fleible is the inovator of todays
packaging world. produced in one revolution.
http://www.prflexbag.com