Flexography

1. The modern letterpress
FLEXOGRAPHY
Presentation by
MD ALI HOSSAIN
Email: malihossain.88@gmail.com
Fb: students.gai@gmail.com
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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16. Flexographic Presses
Central Impression
press
All color stations are
located in a circle around
the impression cylinder.
This press can only print
on one side. Advantage:
excellent registry
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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.
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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.
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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.
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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.
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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.
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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)
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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.
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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.
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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
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