Transcript Printing methods – what you need to know

Printing methods – what you
need to know
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2.
3.
4.
Colour separation
Process colours
CMYK
Registration marks and the order of
application of colours
5. Digital printing
DEFINITIONS
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COLOUR BARS – bars of colour around a printed image to check the density of the
colours being printed
CROP MARKS – marks incorporated in a printed sheet to indicate where the paper is
to be trimmed or cut to size
DIGITAL PRINTING – a system where the printed sheet is directly linked to a
computer so there is no need to produce a printing plate, designs can be easily
customised and changed
FLEXOGRAPHY – used to print cartons, packaging and point of sale materials, used
for ling print runs at low costs
OFFSET LITHOGRAPHY – image is not printed direct from a plate but offset first on
to a rubber covered cylinder which performs the printing operation. The system is
based on the principle of water and oil not mixing. Generally used for long print runs.
PRINT RUN – the number of copies to be printed at one time
PROCESS COLOURS - cyan is a shade of blue, magenta is a shade of red, yellow
and black. These are combined in four colour printing processes to produce a full
colour image.
REGISTRATION MARKS - crossed lines printed around the edge of a design that
need to line up when each colour is applied in order to create a clear image
WEB FED - printing on to a continuous roll of paper rather than single sheets
SHEET FED – pre cut paper is fed in as individual sheets in to a printer.
CMYK: Four colour printing
– process colours
Only four colours are needed to reproduce the
millions of colours visible to the human eye
when printing.
Cyan Magenta Yellow BlacK
Any colour can be reproduced using a combination of these
colours.
These four colours are usually refered to as CMYK.
Before any picture is printed is has to be 'seperated' into these
four colours. This is unsurprisingly called colour seperation.
The centre image
has been divided
onto the four
colours need to
print in full colour.
Printed images are usually made up of millions of tiny dots of colour
placed close to one another. You can see these if you look closely at a
photo in a newspaper. When you stand back away from the image you
can no longer see the individual, CMYK dots but millions of different
colours.
Colours can also be reproduced by overlapping the four colours as the
inks are slightly transparent. Cyan put on top of yellow will appear
green.
Why is a K used to represent black? Wouldn't B be
better?
When we talk about making a colour with light we only need 3 colours,
RGB, Red, Green and Blue. These are the three colours used to make
the colour pictures on your tv, if you look closely as the screen you
will be able see the RGB dots on the screen. The initial 'B' is used here
to refer to blue. It would be confusing if it also meant black.
When full colour products are printed each
of the four printing colours are added
separately.
CMYK
The yellow is printed onto the paper, then
the cyan and so on...
Each colour is added to the paper in a
different part of the machine. The
paper travels from the yellow printer to
the yellow and so on...
It is important that each colour is lined up
exactly with the previous colour...
Registration marks are used for this...
They are usually a cross with a circle
around it. They are printed 4 times,
one in each colour over the top of
each other...
If the colours are lined up accurately you
should only see a black registration
mark. If one of the colours are out of
line you will see that colour registration
mark printed slightly to the side of the
black registration mark...
If the colours are out of line the final image
will appear blurred.
When printing a lot of something the
registration marks are checked every
so often to avoid reproducing a lot of
errors.
The registration mark above (called a colour bar) is
often found on the edge of products. It shows
the Printer at a glance whether one of any colour
has run out. It may be hard to tell by looking at
the image. These registration marks are often
cut off of the final product, though are often
visible of newspapers or maps.
Process
Applications
Advantages
Disadvantages
Lithography
More info...
Magazines
Posters
Cereal boxes
High quality,
Prints photos and text
Widely available
Expensive to set up
Only suitable for long production runs
Gravure
More info...
Expensive packaging
Stamps
Very high quality
Prints photos and text
More expensive than Lithography
Screen Printing
More info...
T-Shirts
Printing on to products such as TV
remotes and walkmans
Can print on uneven surfaces
Can print onto object that will not fit
through a printing press
Can be used for batch production
Flexography
Carrier bags
Yogurt pot lids
Letterpress
More info...
Books with large amounts of text
Only prints simple shapes
Will not print fine detail
Can print onto plastic films and foil
Cheaper to setup than lithography
Lower quality than Lithography
Very sharp letter quality
Only suitable for letters and line
drawings.
NOT SUITABLE FOR PHOTOS
• Lithography
• The process has a printing plate, with the image in relief
which is free to rotate. Ink is applied to the printing plate
which is dampened. This repels ink of any non image
areas. The printing plate then transfers an inked image
onto the rubber blanket cylinder which in turn presses
the image onto the paper as it is fed through.
• Areas to be printed on attract the ink (grease) and areas
not to be printed on attract water.
• High speed and cheap, most common used method.
• Print in full colour. 4 colour process called CYMK
process (yellow, cyan, magenta, black.)
Lithography
Digital Printing
• This type of printing does not need printing
plates as a computer is linked directly to a
printing machine
• It is cost effective for small print runs and the
work being printed can be modified easily
• Digital printing produces less waste in terms of
chemicals
• The ink does not soak into the product but it
forms a thin layer on the surface making the
product easier to recycle
Flexography
• Used on corrugated containers, folding cartons, paper
sacks, plastic carrier bags, milk and juice cartons, sweet
wrappers and labels
• Most common form of printing for packaging due to lower
quality needed and lower production costs
• A flexible plate, which has the images to be printed
raised from its surface, is produced and attached to the
plate cylinder. The material being printed is fed into the
printing press on a roll. Ink is transferred onto a roller
with a dimpled surface that transfers the ink to the plate
and finally on to the material to be printed. Each stage of
the process prints a single colour.
• The inks used for flexography are different than those
used for lithography. It can print onto a variety of
materials, inks dry quickly therefore production is quicker
resulting in lower costs.
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1 screen printing. No fine
detail, small production run,
cheap to set up
2 gravure. Very high quality
needed
3 letterpress. Very sharp
quality, no pictures needed
4 lithography. High quality
colour picture needed
5 lithography. High quality cd
inlay needed in full colour
6 screen printing. Can print
onto rough/uneven surfaces