This document provides an overview of flexography, a modern letterpress printing technique. It discusses the history of flexography, including the development of the first flexography press in England. It describes how flexography has evolved since 1990 with advances in platemaking and inks, allowing it to rival offset printing quality. The document outlines the modern flexography printing process, including photopolymer plates, water-based inks, and various types of flexographic presses. It concludes by discussing common flexography applications in labels, food packaging, and other flexible packaging.
2. History
• The first flexography press was built
in England and was called aniline
printing
• The first rubber printing plates used
aniline oil-based inks
• In the early days the technique was
used mainly for the printing of food
packaging
3. Evolution
Originally flexography could not compete with offset
printing.
Since 1990 advances have been made in platemaking and
flexography inks.
By today full color picture printing is available and print
quality can rival the lithographic process.
4. Progress
Ammonia and Alcohol was used for
the ink as drying agents, that raised
concerns about air pollution
Photopolymer plates are replacing
rubber based plates. They produce a
sharper image.
5. Modern Flexography Inks
The oil-based inks used in letterpress can cause rubber to
swell.
Traditional flexography ink contains ammonia and alcohol.
Pollution control equipment is required for older inks.
Water based ink and a dryer has been pioneered, that
reduces costs.
6. Modern Flexography Inks
There are five types of inks that can be used in flexography:
solvent-based inks.
water-based inks.
electron beam (EB) curing inks.
ultraviolet (UV) curing inks and,
two-part chemically-curing inks (usually based on polyurethane
isocyanate reactions).
Although these are uncommon at the moment.Water based flexo inks
with particle sizes below 5 µm may cause problems when deinking
recycled paper.
7. Flexography Ink Control
The ink is controlled in the flexographic printing process by the
inking unit. The inking unit can be either of fountain roll system or
doctor blade system. The fountain roll system is a simple old
system yet if there is too much or too little ink this system would
likely not control in a good way. The doctor blade inside the
anilox/ceramic roller(Metering roller) uses cell geometry and
distribution. These blades insure that the cells are filled with
enough ink.
8. Modern Flexography Plates
Rubber plates are traditionally used, but the image quality is
not prefect with them.
Photopolymer plates are replacing rubber plates.
Photopolymer plates have a sharper image.
A light process (UV) is used to harden the printing parts of
the plate and the unexposed parts wash away.
Photopolymer plates are as flexible as rubber plates.
9. Platemaking
Method A
The most popular platemaking process uses the UV light
sensitive polymer. A negative is placed over the plate that is
exposed to UV. The polymer hardens at the printing area
and the rest is washed away either by water or some solvent.
Method B
The second method uses laser engraving process to engrave
the printing plate. This method is also called digital plate
making.
10. Platemaking
Method C
The third method is to create a metal negative by an
exposition and acid bath. In the second phase this metal plate
can be used to make a mold from glass, plastic and once it’s
cooled this master mold is used to press the rubber
component through a second molding process.
11. Mounting
In flexography for every printed color a different plate has to
be made, therefore mounting the flexographic plates need to
be very accurate.
Plates in Flexography have mounting marks, but since 2007
an automatic mounting machine (FAMM) is also available.
12. Printing
The ink roll is immersed partly in the ink tank and transfers
the ink onto the meter roll. The meter roll has a special
texture that hold a certain amount of ink. Different meter
rolls can be used for different print jobs. A doctor blade
(meter scraper) removes excess ink from the meter roll.
13. Printing
The scraped meter roll ink the plate finally and then the
substrate (paper) is “sandwiched” between the plate and the
impression cylinder so the imprint transfers to the substrate.
The printed substrate then moves into a dryer.
14. Basic parts of the press
Unwind and infeed section- The roll of stock must be held
under control so the web can unwind as needed
Printing section- Single color station including the fountain,
anilox, plate and impression rolls
Drying station- High velocity heated air, specially formulated
inks and an after-dryer can be used
Outfeed and rewind section- Similar to the unwind segment,
keeps web tension controlled.
15. Flexographic Presses
Stack press
Color stations stack up
vertically, which makes
it easy to access. This
press is able to print on
both sides of the
substrate.
Model NO. FKFS 20 30 40 STACK TYPE
Application OPP. PP. PE. WOVEN BAG. PAPER etc.
Printing Speed. 2~4 COLOR CYLINDERWIDTH *320~1000 6~
COLOR CYLINDER WIDTH*320~800
17. Flexographic Presses
In-line press
Color stations are placed horizontally. This press prints on both
sides, via a turnbar. Advantages: Can print on heavier substrates,
such as corrugated boards.
18. Ink roll – Fountain roller
The ink roll is partially submerged into the ink tank, this
roller transfers the ink onto the anilox or meter roller.
19. Meter roll – Anilox roller
This roller has engraved cells that carry a certain amount of
ink, the excess ink is removed by a doctor blade.
20. Plate cylinder
Usually a two way tape is used on the print cylinder to hold
the flexible printing plate. The ink is transferred to this
cylinder from the meter roll.
21. Impression cylinder
The impression cylinder applies pressure to the plate
cylinder so that the image is transferred to the substrate that
is sandwiched in-between the two cylinders.
22. Applications of Flexography
Labels (mostly by flexography)
Food containers (mostly by flexography)
Flexible packaging (mostly by flexography)
Beverage carriers (mostly by flexography)
Corrugated packaging (mostly by flexography)
Paper sacks (mostly by flexography)
23. Applications of Flexography
Flexographic has an advantage over lithography in that it can use a wider range of inks,
water based rather than oil based inks, and is good at printing on a variety of different
materials like plastic, foil, acetate film, brown paper, and other materials used in
packaging. Typical products printed using flexography include brown corrugated
boxes, flexible packaging including retail and shopping bags, food and hygiene bags and
sacks, milk and beverage cartons, flexible plastics, self-adhesive labels, disposable cups
and containers, envelopes and wallpaper. Printing press speeds of up to 600 meters
per minute (2000 feet per minute) are achievable now with modern technology high-
end printers. Flexo printing is widely used in the converting industry for printing
plastic materials for packaging and other end uses. For maximum efficiency, the flexo
presses produce large rolls of material that are then slit down to their finished size on
slitting machines.
24. Conclusion
Flexography printing can give superb print quality and it is
cost effective with a fast turn-around time. It allows for
printing on the widest range of substrates using a wide
range of ink types and custom colors.
25. References
Wikipedia [Flexography] –
http://en.wikipedia.org/wiki/Flexography
Accessed 21 January 2013
eHow [Flexography Printing Characteristics] -
http://www.ehow.com/info_8475499_flexography-printing-characteristics.html
Accessed 21 January 2013
ScienceDirect [A review of printing and coating techniques] -
http://www.sciencedirect.com/science/article/pii/S0927024808003486
Accessed 21 January 2013
TNT FlexPak [Technical Questions about Flexography and Flexible Packaging] -
http://www.flexpak.co.th/about/faq_technical
Accessed 21 January 2013
Editor's Notes
Flexography is a printing process, usually referred to as the modern version of letterpress. Letterpress is a printmaking process where protruding surface faces are inked and the ink is transferred to the substrate by pressure. The basic idea of flexography remains faithful to the letterpress process.