Flexography and packaging

1. FLEXOGRAPHY
& Packaging
Chapter - 2

2. ● 4 – 8 Color units
● Limited to one side printing
● Ideal press for hairline register at high speeds on
stretchable films
● Longer make-ready times required because printing
units are more difficult to access
Central Impression Press

3. ● 1 – 8 Color units
● Some presses can print on both sides
● Traps should be no less than 1/64” for thin films
● Often used inline with other converting operations such
as lamination, rotary and flat bed diecutting, and
sideseal bag converting
Stack Press

4. ● Up to 12 color units
● Can print two sides with the aid of a turn-bar
● Used for printing thick substrates such as paperboard
● Often used inline with other converting operations such as
lamination,rotary and flatbed diecutting, cross perforation.
In-Line Press

5. ● Same configuration as the inline press
● Sheet-fed; widths up to 120 “
● Usually no more than 4 color
● Limited to one sided printing
● Less accurate registration capabilities
Corrugated Press

6. Plate cylinders with different diameters can be mounted on many
flexographic presses, allowing for variable repeat lengths. Printing a roll
of packaging, such as gift wrap, uses a continuous repeat, where the
same set of images is repeated many times on a continuous stream of
substrate. To avoid the plate seam, images may require nesting, an
arrangement that creates a staggered effect. Staggering images gives the
appearance that the design is continuous, no matter where the substrate is
cut.
Repeat Length

7. ● Molded rubber plates shrink when they are
removed from the molding press. Plate films
should be adjusted to compensate for
shrinkage, which is typically 1.5% - 2.0%
in the direction of the rubber grain, and
0.5% - 1% across it.
● Exact shrinkage amounts should be
communicated between production artists
and platemakers.
● Line screening is limited to 120 lpi
● Registration can be more difficult than with
photopolymer plates.
● Nesting is required for the appearance of
continuous repeat.
● It is difficult to mold accurate rubber plates
larger than 24”x 36”. Larger designs must be
placed on multiple plates for each other.
Plate types (Molded Rubber)

8. ● Line screening is at least 150 lpi
and can be as high as 200 lpi.
● Nesting is required for the
appearance of continuous repeat.
● Positioning and register devices on
most modern flexographic presses
are designed for one-piece
photpolymer plates.
● Direct-to-plate laser imaging is
available
Plate types (Photopolymer)

9. ● Line screening is limited to 100 lpi for
tone reproduction, but can be 200 to
300 lpi for tints.
● Film is not required
● Design rolls can provide a true
continuous repeat with a continuous
background color.
● Plates or design rolls imaged directly
on the cylinder do not require
compensation for plate elongation.
● Laser ablating is available for both
rubber and photopolymer
Plate types (Laser Ablated)

10. When designing images for
flexographic printing, it is important to
understand the effects of plate
elongation. Because flexographic
plates are made with soft material,
they tend to stretch when mounted on
the plate cylinder,sometimes distorting
images and text. A circle, for example,
may be stretched to look more like
oval.
Fortunately,special flexographic
software can compensate for plate
elongation by slightly distorting
images.
Plates Elongation

11. Distortion is usually performed
within the flexographic software
application or at the RIP stage
before the film is imaged. The
amount of distortion depends on
the thickness of the plate and the
mounting tape used to fasten it,
and on the circumference of the
cylinder(the repeat length). In
general, thicker plates and shorter
repeat lengths increase the
elongation.
To be sure that images will be printed with the correct size and shape, the design should be output
to film after plate thickness has been determined and the proper distortion factor has been applied.
Plates Distortion

12. Flexography is ideal for printing
packaging materials because the
soft plates can transfer ink to
many different kinds of substrates-
--anything from corrugated board
to candy wrappers. The qualilty of
a printed product is determined not
only by the type of plate, but also
by the substrate itself.
Different substrates allow varying
degrees of ink absorption, gloss,
brightness, and color defination.
Substrates

13. Because the appeal of packaging
is significantly enhanced by color,
flexographic presses commonly
offer six & eight colors, and even as
many as twelve for limited
applications.
Designers can choose from a
number of different combinations,
including multiple spot colors and
HIFI printing, which is a method of
increasing the color gamut by
printing six or seven process colors.
Color capabilities

14. Most flexographic inks consist of
opaque or semi-opaque pigments. To
ensure proper ink coverage, the spot
colors are usually printed from
lightest to darkest. Process colo inks
are made from transparent pigments
and can be applied in any sequence.
Transparent substrates, such as
polypropylene, require a white
backup plate provided by a “Choke”
plate, as a background for colors;
otherwise, colors would appear flat
and translucent.
Another technique used for
applying inks to transparent
substrates is reverse-side printing.
The image is laterally reversed,
and colors are printed instead from
darkest to lightest; the packaging
is then displayed from the non-ink
side of the substrate.
This provides a scratch proof
surface to the ink layer, and a
glossy finish. In some cases
waterbased ink is used for
reverse-side printing lamination.
Color capabilities

15. To be continued
Author : Mohammed Abdul Haleem
Email : ah.flexomaster@gmail.com
With almost 29 years of experience in the Printing industry, he offers proactive recommendations on anilox roll
specifications, testing, inventory management, flexographic equipments applications,training, drawing from experience in
technical sales,marketing,production,technical service,parts and supplies. His experience covers the spectrum of
flexographic markets including: wide web film, narrow web, tag & labels,foil, folding carton, corrugated packaging
applications