Modern Printing Methods explained'

1
What do we need to know for our exam????

• The AQA (our examining board) specifies the
  following
• Quality checks such as colour registration marks,
  position marks.
• Commercial printing methods- letterpress,
  lithography, flexography, gravure and screen
  printing.
• Varnishing (oil, spirit, UV and water).
• Laminating, embossing and foil application.
• Multiple surface developments (nets) produced by
  die cutters and creasing bars.

2
The five main types of printing are

• Relief- Letterpress, Block printing, Flexography
  (foil blocking)
• Planographic (flat plate printing)- Lithography
  offset lithography
• Intaglio (etching) Gravure, Screen Printing
• Xenography (dry printing)- Photocopying, Laser
  printing, commercial digital printing
• Please note that while it is good to know what
  these are, not all are required for the AQA
  syllabus.

3
Flexography

• Flexography is a form of relief (a raised
  profile) printing.
• The image is slightly raised, inked and the
  printed straight onto the substrate (technical
  term for paper, card or whatever is being printed
  on).
• The plate is usually made from soft rubber or
  plastic and uses a quick drying ink.
• This high speed process is well suited to a
  number of materials such as acetate film,
  polyethylene (eg supermarket bags), brown paper
  and newsprint.
• For more information visit http//graphics.tech.u
  h.edu/MatProcesses/Flexography.html

Flexograph machine
a rubber flexograph plate
4
Offset Lithography

• Offset Lithography is by far the most common
  form of commercial printing. It accounts for over
  70 of commercial printing.
• Offset lithography works on a very simple
  principle oil and water dont mix. Images (words
  and art) are put on plates which are damped first
  by water the by oil-based ink. The ink sticks to
  the image area , the water to the non-image area
  which absorb moisture and repel ink. Then the
  image is transferred to a rubber roller and then
  to the substrate. This happens at an extremely
  fast speed as the plates are wrapped around a
  roller. The paper is web fed (a continuous roll).

5
What happens inside
An offset lithography machine has four of these
presses, printing the cyan, magenta, yellow and
black (CYMK) components of a print.
6

• Advantages of offset lithography
• Prints 4 colours onto flat materials
• It is a high quality process
• Very economical on medium to large production
  runs 500 - 500,000
• It is a fast process speeds of up to 50,000
  presses per hour can be acheived on a web fed
  press!
• Disadvantages of offset lithography
• Less economic than rotogravure and flexography on
  high volume printing 1,000,000
• Less economic than digital printing on small to
  medium runs 50 -100,000(although quality is
  slightly higher)
• Limited to the type of materials it can print
  onto the surface must be flat. Litho would not
  be accurate enough for newspaper print.

7
Gravure
Gravure is a printing process that uses intaglio
or engraved metal plates or cylinders. The image
to be printed is photo-etched onto the plate as
microscopic dots. Rotogravure is a printing
technique characterised by high print quality and
large numbers of copies hundreds of thousands
or even many millions. Tiny ink volumes are
transferred from the gravure printing cylinder to
printing dots on the paper. Millions of printing
dots show up to the human eye as letters/text or
images
The "doctor blade" is angled against the cylinder
to wipe away the excess ink, leaving ink only in
the cell wells
8

• The main application of gravure covers a wide
  range of commercial products.
• Gravure is especially suited to work in the four
  colour process on relatively
• cheap papers in quantities over 250,000. The
  reason being the expense of the
• original printing plates which can each run into
  thousands of pounds.
• Example applications include
• magazines
• mail-order
• catalogues
• Board packaging products such as folding box
  cartons for food and cigarette industries, also
  printed video cases.
• Flexible packaging such as printed cellophane
  and polythene used in food wrapping, display and
  production.

9

• Advantages of Gravure
• It can be used for the highest quality
  reproductions
• It uses lower grade, lighter paper than
  lithography
• High speed usually 6000-10,000 prints per hour
• Automatic registration.
• Disadvantages of gravure
• Initial cost of rotogravure plates extremely high
  therefore it is only economic for very high print
  runs
• Colour correction is difficult

10
Silk Screen Printing

• Screen Printing is unlike any other process as it
  uses a stencil through which ink is
• pushed. The process involves forcing ink through
  a fine mesh (screen) which helps to
• spread the ink evenly.

• Its easy to use, versatile and requires low
  capital investment.
• Relatively cheap on short and medium print runs
  automated presses which can print, varnish or
  gum up to 6000 per hour.
• Most importantly it can print onto curvrd and
  uneven surfaces

11
The main stages of modern print production
Stiching binding stapling
Embossing, blocking
Finishing
Varnish and laquer
Die cutting and creasing
12
The main stages of modern print production

• The basic stages of modern print production are
• Original artwork photographs, illustrations and
  text are scanned and entered into a computer
• These elements are combined into a document using
  page makeup or desktop publishing software
• Full size films are output using a
  high-resolution imagesetter. These could be
  either positives or negatives.
• Printing plates are made from films using a
  photochemical process
• The flexible plates are attached to the plate
  cylinders of a litho press and the job is
  printed.

13
Full Colour Printing

• For printing, and image is separated into its
• colours Cyan, Magenta, Yellow and Black
• (CMYK).
• Each colour is printed over the other as the
• paper (or substrate) moves through the
• presses. Each colour has its own press.

Cyan
magenta
yellow
black
For the original go to micro.magnet.fsu.edu/.../pr
imarycolors/ colorseparation/
14
Quality Control

• The two main quality checks are
• Registration
• Colour Density
• Registration can be checked by either eye or
  automatically and are used to check that the 4
  processes are aligned properly on the substrate.
  Images out of alignment can appear blurred.
• Colour density is checked using a Densitometer,
  which is a hand held device that measures the
  density of colour.
• The densitometer is held over the colour bar (one
  colour for each of the process colours and
  greyscale.

A colour density bar
15
Binding

• Once printed the next stage is the binding of the
  product. The bindery is where the
• printed product is completed. The huge rolls of
  now-printed paper are cut and put
• together so that pages fall in the correct order.
  Pages are also bound together by,
• staples or glue, in this step of the process.
• A machine called a stitcher takes the folded
  printed paper (called press signatures)
• and collates them together.
• The final components in the stitcher machine are
  the knives which trim the paper to its final
  delivered size.

A sticher machine
Paper being cropped manually
16
Cutting and Folding (creasing)

• Most cartons (packages, boxes) require cut outs
  and creases in order for them to be
• assembled. The machine tool used on modern
  presses is the die cutter.