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.
Modern Printing Methods explained.
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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.
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3. Modern Printing Methods explained.
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:
Flexograph machine
a rubber flexograph plate
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4. Modern Printing Methods explained.
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 don’t 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).
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5. Modern Printing Methods explained.
What happens inside…
An offset lithography machine has four of these presses, printing the cyan, magenta, yellow and black (CYMK) components of a print.
Modern Printing Methods explained.
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6. Modern Printing Methods explained.
Advantages of offset lithography:
Prints 4 colours onto flat materials
It is a high quality process
Very economical on medium to large production runs ,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 ,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.
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7. Modern Printing Methods explained.
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
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8. Modern Printing Methods explained.
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.
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9. Modern Printing Methods explained.
Advantages of Gravure:
It can be used for the highest quality reproductions
It uses lower grade, lighter paper than lithography
High speed usually ,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
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10. Modern Printing Methods explained.
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
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11. The main stages of modern print production
Prepress
origination
compostion
Colour separation
Plate production
print
sheet or web fed
4 colour printing
Quality control
Stiching binding stapling
Embossing, blocking
Finishing
Varnish and laquer
Die cutting and creasing
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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.
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13. Modern Printing Methods explained.
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/.../primarycolors/ colorseparation/
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14. Modern Printing Methods explained.
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.
Registration marks at about 10X magnification
A colour density bar
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15. Modern Printing Methods explained.
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
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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.
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