|
Gravure Printing
Applications - Process Overview
- Inks - Press Design and Equipment
Applications:
Typical gravure printed products include:
- Food packaging
- Wall paper
- Wrapping paper
- Furniture laminates
- Paneling
- Greeting cards
- Magazines
Process Overview
Gravure printing is characteristically used for long run, high quality
printing producing a sharp, fine image. The number of gravure printing
plants in the U.S. is significantly lower than other printing processes.
This is due, in part, to the cost of presses and components. While a
lithographic press will cost in the range of $100,000 the cost of gravure
press will be in the range of $1 million. Additionally a single gravure
cylinder will cost around $5000 versus around $15 for a lithographic
plate. Additionally, the gravure cylinder has a long service life and will
yield a very large number of impressions without degradation.
More information...
Gravure Process Flow Diagram
Gravure printing is an example of intaglio printing. It uses a
depressed or sunken surface for the image. The image areas consist of
honey comb shaped cells or wells that are etched or engraved into a copper
cylinder. The unetched areas of the cylinder represent the non-image or
unprinted areas. The cylinder rotates in a bath of ink called the ink pan.
As the cylinder turns, the excess ink is wiped off the cylinder by a
flexible steel doctor blade. The ink remaining in the recessed cells forms
the image by direct transfer to the substrate (paper or other material) as
it passes between the plate cylinder and the impression cylinder.
The major unit operations in a gravure printing operation are:
- Image preparation
- Cylinder preparation
- Printing
- Finishing
Gravure Inks - Solvent Based, Water Based
Gravure inks are fluid inks with a very low viscosity that allows them
to be drawn into the engraved cells in the cylinder then transferred onto
the substrate. In order to dry the ink and drive off the solvents or
water, which essentially replaces most of the solvent, the paper is run
through Gas fired or electric fired driers. The ink will dry before the
paper reaches the next printing station on the press. This is necessary
because wet inks cannot be overprinted without smearing and smudging.
Therefore, high volume air dryers are placed after each printing station.
The solvent-laden air from the dryers is passed through either a
solvent recovery system or solvent vapor incinerator. A typical recovery
system uses beds of activated carbon to absorb the solvent. Saturated beds
are regenerated by steam. The solvent laden steam is then condensed and
the water and solvent separate by gravity. Greater than 95 percent of the
ink solvents can be recovered using this process (Buonicore). The solvents
can either be reused or destroyed by incineration.
Water based inks, especially used for packaging and product gravure,
require a higher temperature and longer drier exposure time in order to
drive off the water and lower vapor pressure constituents. As mentioned
subsequent sections, Flexo and Gravure inks are very similar and the
constituents are essentially the same. Again, a pollution control device
may be needed.
Gravure Press Design and Equipment
Web-fed gravure presses account for almost all publication, packaging,
and product gravure printing. These presses are generally custom
manufactured machines designed for a specific range of products. The
typical press is highly automated and consists of multiple print units.
The printing mechanism in a rotogravure press consists of a gravure
cylinder and a smaller, rubber clad impression cylinder.
Other types of gravure presses in commercial use today are sheet-fed,
intaglio plate, and offset gravure. These types of presses are used
primarily for special printing applications.
More information on Web Fed Gravure...
More information on Sheet Fed Gravure...
|
