high speed inline coating for sheet fed printing presses
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High Speed Inline Coatingfor Sheet Fed Printing Presses
High Speed Inline Coating for Sheet Fed Printing Presses
Preconditions
- up to 12,000 prints/h the usual processing instructions are to be observed
- for High Speed Inline Coating with a printing speed of up to 18,000 sheets/h the processing range must be adapted regarding
- substrate- ink layer thickness- coating viscosity- coating selection- performance of the dryer- distance under the dryer
High Speed Inline Coating for Sheet Fed Printing Presses
Substrate - Ink
- the combination of substrate and ink should be selected in a way to assure a good bond between ink and substrate
- poor ink drying cannot be improved by coating
- the result is bad rub resistance and insufficient scotch tape resistance
High Speed Inline Coating for Sheet Fed Printing Presses
Adhesion Substrate - Ink
Paper
Ink C oating
High Speed Inline Coating for Sheet Fed Printing Presses
Ink Layer Thickness
- Overinking of the ink layer thickness with parallel inline coating will reduce the performance of the printing press
- as by reducing the printing speed the drying time is adjusted
High Speed Inline Coating for Sheet Fed Printing Presses
Paper Paper
Ink C oating Ink C oating
Normal Inking Overinking
Ink Layer Thickness
High Speed Inline Coating for Sheet Fed Printing Presses
Cell Volume of the Screen Rollers
- the cell volume of a screen roller is indicated with the scoop amount of water in ml/m²
- the coating application amount corresponds to about 1/3 of the indicated cell volume of the screen roller
Example:
A cell volume of the screen roller
of 15 g/m² corresponds to approx 5 g/m² coating application
High Speed Inline Coating for Sheet Fed Printing Presses
Gloss Diagram after 24h Drying
30
35
40
45
50
55
0 5 10 15 20
Glo
ss i
n %
Drying Time in h
3 g/m²2 g/m²
1 g/m²
Wet-on- Wet Printing
High Speed Inline Coating for Sheet Fed Printing Presses
Coating Viscosity
- the coating viscosity depends on the temperature and is determined with a 4 mm DIN cup at 20°C
- when the temperature in the coating rises the viscosity will decrease
- in case of a viscosity decrease, e.g. below 25 sec., an even coating application cannot be assured any more
High Speed Inline Coating for Sheet Fed Printing Presses
Viscosity depending on the Temperature
Vis
cosi
ty i
n s
20
40
60
80
100
15 25 35 45
Temperature in °C
High Speed Inline Coating for Sheet Fed Printing Presses
Variable Coating Viscosities
Cooling Units for Coatings by EASYLAC keep the coating stable in viscosity
High Speed Inline Coating for Sheet Fed Printing Presses
Too high Coating Viscosity
- a too high coating viscosity, e.g. above 65 sec. can be adjusted by dilution with water to the required viscosity
- a too high coating viscosity in connection with High Speed Inline Coating will lead to splashing
High Speed Inline Coating for Sheet Fed Printing Presses
Dilution of the Coatings with Water
20
30
40
50
60
70
80
0 4 8 12 16 20
Vis
cosi
ty in
sec
.D
IN 4
mm
Cu
p a
t 20
°C
approximate Water Amount in %
High Speed Inline Coating for Sheet Fed Printing Presses
Coating Selection
- the drying behaviour of coatings depend on the coating type
- if for example the following coating types are used:
- matt- semi matt- protection- gloss- high gloss- UV coatings
their drying behaviour will be considerably different
High Speed Inline Coating for Sheet Fed Printing Presses
Coating Selection
For dispersion coatings:
The higher the gloss, the slower the thorough drying
Rule of thumb:
0
10
20
30
40
50
60
70
80
90
CartonGD2-
printed
DL 1176 DL 1351 DL VP385
DL 1200 DL 1300DL 1650
DL 1150 DL VP9756
Gloss in % Drying time in s
High Speed Inline Coating for Sheet Fed Printing Presses
Gloss Diagram: different coatings on the same substrate
High Speed Inline Coating for Sheet Fed Printing Presses
Influence of the Surface Structure of the Substrate
30
40
50
60
70
80
0 2 4 6 8 10 12
Carton 1
Carton 2
Application Amount g/m² wet
Glo
ss i
n %
High Speed Inline Coating for Sheet Fed Printing Presses
UV Coatings
- UV coatings dry immediately by photo-polymerisation using short wave light
- the acetone test shows whether the coatings have dried thoroughly
High Speed Inline Coating for Sheet Fed Printing Presses
Performance of the Dryers
- the drying behaviour of the coatings is determined by the performance of the dryer
- the thorough drying of dispersion coatings is primarily determined by the available amount of air
The more air, the better for the thorough drying- beginning at a pile temperature of approx. 35 °C problems may occur in the pile
High Speed Inline Coating for Sheet Fed Printing Presses
Drying of UV Coatings
- for UV coating processes the condition of the UV lamps and a sufficient performance are responsible for a good coating result
- the temperature in the pile is also decisive for UV coatings and may be responsible for subsequent problems in print finishing
- too high temperatures may result in breaking of the printed matter during the grooving and folding process
High Speed Inline Coating for Sheet Fed Printing Presses
Drying Distance
An extended delivery between coating tower and delivery is advantageous for the printing speed.
A short delivery is a disadvantage for High Speed Inline Coating.
High Speed Inline Coating for Sheet Fed Printing Presses
Printing Press with Double Extended Delivery
High Speed Inline Coating for Sheet Fed Printing Presses
Special Coating Applications
- for special coating applications, as e.g. application of blister coating, a coating amount of 6 – 8 g/m² has to be applied in order to assure good bonding with the plastic foil
High Speed Inline Coating for Sheet Fed Printing Presses
Result
High Speed Inline Coating with 18.000 prints/h will not present any problems if the appropriate coatings are used and the printing press is well adjusted.