Optimizing HD Flexo for Different Plate Technologies and Substrates

Transcription

International Circular of Graphic Education and Research, No. 7, 2014
Optimizing HD Flexo for Different Plate Technologies and
Substrates
Tatiana Bozhkova, A. Ganchev and Jana Kisova
Keywords: HD Flexo, screen elwements, increase of the tonal value, printing plates
Flexo printing is a technology widely used in the packaging industry – for labels, packaging for food, pharmacy
and for many other applications. Flexo printing is suitable for printing on a large variety of substrates like different foils, paper, carton, corrugated or combined materials. With the development of the market, customers and
print buyers are asking for top quality, especially as this is related to the printing of labels. This is the reason why
in April 2009 Esko developed an entirely new approach towards the flexo printing, named HD Flexo. The goal is
to achieve High Definition Flexo by combining two elements – high resolution (4000 dpi) and a special algorithm
for screening that would make the smooth transition to zero in vignettes. As a result of the implementation of
the new technology, according to Esko, several improvements are observed, i.e. smooth transitions to 0%, and
increased tonal range, similar to offset and gravure printing. Additional advantage of HD that are claimed by
Esko include a full range of printing plates (solvent, thermal or water processed); higher run length, due to the
perfected shape of the screen elements, resulting in a higher stability of the dots during printing process and
increased tonal range, when HD Flexo is used. For test purposes, analyses of parameters of HD Flexo at real
production conditions were done. Test samples were printed on two different substrates - paper and polyethylene. Printing conditions were the standard for the printing house and some higher screen rulings were tested to
establish the possibility to increase the commonly used screen ruling.
1. Introduction
The growth observed nowadays in the packaging
industry and particularly in the flexo printing technology
is related to the increased level of print quality in flexo.
This is valid not only for the already developed world
but also for the so called emerging markets, including
Bulgaria. Interest in state of the art technologies is easy
to understand – this could be the best way to compete
for print buyers, who look to reduce costs, but are not
ready to compromise with the quality.
There were several developments that help the flexo
industry to become stronger, but the impact of the new
technologies in the plate making process is a really big
contributor to this trend. The goal of going digital was
to eliminate one additional step, such as film making
and all critical aspects of copying a negative film to the
photopolymer plate. One step less of course gives a big
advantage – we can forget about all troubles like dust,
poor vacuum, lost of fine elements etc. But dot shrinking (or the so called now round dot vs flat top dot) during digital plate making was a real gift for technology.
It gave the flexo a chance to reproduce a very fine and
small half tone dots with steep shoulders, reducing the
dot gain to the level of offset printing. The result was
a big increase in the tonal range, which improved the
reproduction of fine details, especially in the highlights.
Conversion from analog to digital plate practically gave
a chance for flexo to successfully compete with other
print methods, such as offset and gravure. The chance
to make flexo a leading technology in the packaging
industry gave a strong push to the key suppliers to allocate a lot of resources to further develop it. We can
say that in practice, the reproduction with flexo printing
became very close to what can be achieved by offset
printing, but there were still some open questions and
one of them was a smooth transition to “zero”. Partly,
this was solved with the invention of the hybrid screening, an elegant way to make such transition practically
invisible. But, it was correct only when such transition
was in one color. If the reproduction required it to be
applied in more than one color, then it does not look so
nice. Overlapping of stochastic screening in more than
one color is always a challenge and the results are not
always good. The main goal of the HD Flexo is to solve
this problem. However, implementing it in practice requires the definition of optimal parameters and settings.
The objective of the present research is to analyze the
parameters, required to implement the HD Flexo technology in real production conditions and to specify how
much screen ruling can be increased without compromising with the speed and stability of printing.
2. Materials and Methods
Conditions of test trials
Tests were made using a digital plate making technology on the following photopolymer plates: DuPont Cyrel
DPR45 – Solvent washable plate and DuPont Cyrel FAST
DFQ45 – Thermal Plate.
44
science & technology
Printing plates are produced on the following equipment:
•Cyrel® Digital Imager - CDI Spark 4835 and CDI
Advance Cantilever 1450;
on many factors – the RIP characteristics, the printing
press and especially the anilox roller parameters, the
print substrates, the dot gain and many others. That is
why printing with a screen ruling of more than 200 lpi is
very difficult to achieve, due to all these factors, which
are influencing final results.
Once the screen ruling has been chosen, a magnifying
glass is used to observe the created dots at 0.5% imprint
on the four different screen fields (HD Flexo C56, C46,
C36 and C30). For example C30 means that the smallest
dot is created by 30 pixels at 4000dpi.
Dot size and dot gain gain were measured with
Gretag Macbeth densitometer.
Based on this, a print characteristic curve is created.
The interesting part in the HD Flexo technology is that
bump curves are not applied, or if they are applied, the
bump up is minimal. As for the dot gain compensation
in mid tones – it remains the same, because HD Flexo is
changing the algorithm for screen generation at highlights and shadows only.
•Exposure unit Cyrel 2000 ECLF;
•Solvent plate making processor Cyrel 1000P and
Cyrel Dryer 1000D;
•Thermal plate making processor Cyrel FAST TD1000;
•Printing press Edale Beta 330, 8 colors, width 330
mm, maximum production speed 150 m/min.
Test plates with a thickness of 1.14mm were produced at Polyflex Ltd. according to the standard for
the company plate making process used in their daily
production.
Print trials were done in Janet Printing house.
The photopolymer plates used were a thickness of
1.14 mm and were produced using the CTP technology
from a “Polyflex” form. Better results are received when
an anilox cylinder is chosen with a lower ink transfer.
For the printed images the same set of anilox rolls were
used, with a cell count of 1200 lpi and the ink transfer
for Cyan is 2.3 g/m2.
Methodology of the research and analysis of results
The photopolymer plates are chosen according to a digital plate making technology with solvent and thermal
washing. Six different plate sets of solvent and thermal
plates were prepared with screen ruling of 198 lpi, 174
lpi and 161 lpi. The preferred solid ink density was from
1.30 to 1.40.
HD Flexo benchmark test targets are combined with
test targets developed by Polyflex. The control elements
used were measured and visually controlled.
The samples are printed on two different substrates:
paper and polyethylene. The control test target, marked
as DuPont Cyrel® DPR, is shown on (Fig. 1).
At first, the circles for transition to zero are checked
– they have to transition to zero without a visible halo
effect. This can be observed without special measuring
devices. Based on this, the preferable screen ruling is
selected. The higher screen ruling gives the possibility to
reproduce more fine details of the image, but it depends
Figure 1: HD Flexo benchmark test plate
45
Fig. 1 HD Flexo benchmark test plate.
Dot size and dot gain gain were measured with Gretag Macbeth densitometer.
Based on this, a print characteristic curve is created. The interesting part in the HD
Flexo technology is that bump curves are not applied, or if they are applied, the bump up is
minimal. As for the dot gain compensation in mid tones – it remains the same, because HD
Flexo is changing the algorithm for screen generation at highlights and shadows only.
3. Results
A print characteristic curve based on the results obtained
from a test print on paper with solvent washed plate
type and screen ruling of 161 lpi shown in Figure 2. As
it can be seen from the graphic, the best results were
achieved at value HD C 46 (Fig. 2 b).
AAprint
characteristic
on aobtained
print test
print characteristic
curve curve
is basedbased
on the results
from trial,
a test print on paper
with
screen ruling
of 161 lpi and with
solvent
washedwashed
plate type. plate
As it can
printed
on polyethylene
with
solvent
at be seen from the
graphic (Fig. 2 a, b), the best results were achieved at value HD C 46.
screen ruling of 161 lpi is drawn in Figure 5 a). Field HD
C36 is selected as at this value the transition to zero is
the100smoothest (Fig. 5 b ).
90
The results of the print trials, printed on paper with
solvent washed plate and screen ruling of 174 lpi are
shown in Figures 3 a,b.
Print,%
A80print characteristic curve of a print test trial on
70
polyethylene
with solvent washed photopolymer plate at
HD C46
60
screen
ruling 174 lpi is drawn (Fig. 6 a, b) – best results
50
Dot=C, 37°,
are achieved at HD C 46.
Bump 6,0%
Fig. 1 HD Flexo benchmark test plate.
Dot size and dot gain gain were measured with Gretag Macbeth densitometer.
40
According
toa the
forcurve
printis created.
test trials
on
Based on this,
printmethod
characteristic
The interesting
part in the HD
Flexo technology is that bump curves are not applied, or if they are applied, the bump up30is
paper
described
above,
the
results
for
solvent
washed
minimal. As for the dot gain compensation in mid tones – it remains the same, because HD
20
photopolymer
plate atforscreen
ruling ofat highlights
198 lpi,and
theshadows
best only.
Flexo
is changing the algorithm
screen generation
10
results are achieved at HD C56 (Fig. 4 a, b).
0
A print characteristic curve is based on the results obtained from a test print on paper
with screen ruling of 161 lpi and with solvent washed plate type. As it can be seen from the0
graphic (Fig. 2 a, b), the best results were achieved at value HD C 46.
20
40
60
80
100
File,%
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14
100
90
12
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40
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0
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File, %
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14
paper – solvent washed photopolymer plate,
10
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8
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6
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18
HD C36
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4
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Bump 6,0%
80
2
4
a. Graduation of the reproduction
HD C56
HD C56
12
HD C46
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0
0
2
4
6
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8
10
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Print,%
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Print, %
Print,%
8
Gradation of reproduction in the bright areas
Figure 2: a)a. Gradation
thereproduction
reproduction, b) Gradation of the reproduction in b.highlights;
Gradations of the
0 2 Gradation
Fig.
of the reproduction at screen ruling of recording 161 lpi,
screen ruling: 161 lpi; substrate: paper; plate: solvent washed photopolymer
plate
12
Print,Print,%
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6
File, %
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20
File,%
b. Gradation of reproduction in the bright areas
20
Fig. 2 Gradation of the reproduction at screen ruling of recording 161 lpi,
20
40
60
80
HD C36
8
HD C30
6
Dot=C, 37°,
Bump 6,5%
4
2
0
0
10
0
100
File,
%
File,%
40
2
4
6
8
10
12
File,%
File, %
18
Figure 3: a) Gradation of the reproduction, b) Gradation of the reproduction in highlights;
b. Graduation of the reproduction in highlights
screen ruling: 174 lpi; substrate: paper; plate: solvent washed photopolymer plate
Fig. 3 Graduation of the reproduction at screen ruling at
174 lpi, paper – solvent washed photopolymer plate
16
14
12
46
,%
HD C46
10
According to the method for print test trials on paper described above, solvent washed
plate at screen ruling of 198 lpi, the best results are achieved at HD C56 (Fig. 4
HD C56 photopolymer
a, b).
80
70
Print,%
60
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50
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Bump 7,5%
40
30
20
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80
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Bump 6,0%
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60
80
100
200
File, %
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8
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a. Graduation
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Figure
4: a) Gradation
of the reproduction, b) Gradation of the reproduction 0in highlights;
20
40
60
80
100
b. Graduation
screen ruling: 198 lpi; substrate: paper; plate: solvent washed photopolymer
plate of the reproduction in highlights
File,%
Fig. 4 Graduation of the reproduction at screen ruling
198
lpi, paper –ofsolvent
washed photopolymer plate
a. Graduation
the reproduction
A print characteristic curve based on a print test trial, printed on polyethylene with
solvent 25
washed plate at screen ruling of 161 lpi is drawn (Fig. 5 a). Field HD C36 is selected
as at this value the transition to zero is the smoothest (Fig. 5 b ).
16
120
14
12
100
HD C56
20
HD C46
8
HD C36
60
6
Dot=C, 37°,
Bump 6,0%
HD C30
440
HD C56
15
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80
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6
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12
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20
5: a) Gradation
of the reproduction,
b) Gradation of the reproductionb.inGraduation
highlights;of the reproduction in highlights
Fig.Figure
4 Graduation
of the reproduction
at screen ruling
25
0
screen
ruling:
161
lpi;
substrate:
polyethylene;
plate:
solvent
washed
photopolymer
plate
198 lpi, paper – solvent washed photopolymer plate
20
40
60
Fig. 5 0Graduation
of the
reproduction
at80screen100
ruling
A print characteristic curve based on a print test trial, printed on polyethylene with
161 lpi, polyethylene
File,% – solvent washed photopolymer plate
washed plate at screen ruling of 161 lpi is drawn (Fig. 5 a). Field HD C36 is selected
solvent
20
as at this value the transition to zero is the smoothest (Fig. 5 b ).
HD C56
HD C46
HD C56
HD C30
100
5
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Bump 6,0%
80
Print,
%
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20
HD C36
120
10
0
60
a. Graduation
of the
A print characteristic
curve
of reproduction
a print test trial on polyethylene with solvent washed
25
photopolymer
plate at screen ruling 174 lpi is drawn (Fig. 6 a, b) – best results are achieved at
HD C 46.
Print, %Print,%
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15
HD C46
0
40
20 b.
2
4
6
8
10
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Bump 6,5%
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15
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6
HD C30
10
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5
Graduation of the reproduction in highlights
Fig.
5 Graduation of the reproduction at screen ruling
0
16120lpi, polyethylene
photopolymer plate
0
40
60– solvent
80 washed
100
0
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2
4
6
8
10
12
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A print characteristic curve
of%
a print test trial on polyethylene with solvent washed
File,
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photopolymer plate
at screen of
ruling
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a. Graduation
the reproduction
HD C 46.Figure 6: a) Gradation of the reproduction, b) Gradation of the reproduction inb.highlights;
25
20
screen ruling: 174 lpi; substrate: polyethylene; plate: solvent washed photopolymer
plate– solvent washed photopolymer plate
174 lpi, polyethylene
A print characteristic curve of a print test trial printed on polyethylene with solvent
washed photopolymer plate and screen ruling 198 lpi is drawn (Fig. 7 a, b) - the selected value
is HD C56.
47
HD C56
t,%
15
HD C46
HD C36
7
7
Print,
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60
Dot=C, 37°,
Bump 7,5%
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20
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20
40
60
80
100
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20
18
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16
14
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100
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Bump 7,5%
40
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12
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10
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8
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Bump 7,5%
6
4
20
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20
40
60
80
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100
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6
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8
10
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Figure 7: a) Gradation of the reproduction, b) Gradation of the reproduction in highlights;
Fig.photopolymer
7 Graduation ofplate
the reproduction at screen ruling
screen ruling: 198 lpi; substrate: polyethylene; plate: solvent washed
20
18
16
14
HD C56
198 lpi, polyethylene – solvent washed photopolymer plate
Following the above mentioned steps, a benchmark test is made for the thermal
technology, and the only difference is that at the FAST® technology the HD dot values are
lower (HD C31, C29, C27, C23).
For the print test on paper – thermal photopolymer plate with screen ruling 161 lpi,
and from the drawn curves (Fig. 8 b), the smallest dot to be built with 27 pixels at 4000 dpi is
The
graphics on Figure 9 b shows, that on print
selected,
100 i.e. HD C27 (Fig. 8)
Print,%
Print,%
Following the above mentioned steps, a benchmarkHD C46
HD C36
test10 is made for the thermal technology, and the only
samples,
printed on paper with thermal plate and screen
90
HD C30
®
difference
is that at the FAST technology the HD dot Dot=C, 37°,ruling
80 174 lpi, the smoothest transition is observed
8
Bump 7,5%
70 HD C23 is applied (Fig. 9 a).
values
are lower (HD C31, C29, C27, C23).
when
6
12
4
For
the print test on paper – thermal photopolymer
2
plate
with screen ruling 161 lpi, and from the drawn
0
0 (Fig. 28 b), the
4
6
12
curves
smallest
dot8 to be 10built with
27
File,%
pixels at 4000 dpi is selected,
i.e. HD C27 (Fig. 8).
60
50
HD C27
The
graphics on Figure10 b shows that on print
40
samples,
printed
on
paper
with
thermal
plate
and
screen
30
Dot=C,
37°,
Bump 3,5%
20 198 lpi, the smoothest transition is observed with
ruling
10
27 pixels,
i.e. HD C27 (Fig. 10).
0
198 lpi, polyethylene – solvent washed photopolymer plate
Following the above mentioned steps, a benchmark test is made for the thermal
technology, and the only difference is that at the FAST® technology the HD dot values are
lower (HD C31, C29, C27, C23).
20
For the print test on paper – thermal photopolymer plate with screen ruling 161 lpi,
100
and from the drawn curves (Fig. 8 b), the smallest dot to be built with 27 pixels at 4000 dpi18is
16
selected,90i.e. HD C27 (Fig. 8)
80
40
Print,%
HD C27
Print, %
Print,%
Print, %
50
30
Dot=C, 37°,
Bump 3,5%
20
20
40
60
80
100
File,%
HD C31
HD C29
12
HD C27
10
8
HD C23
6
Dot=C, 37°,
Bump 3,5%
9
4
2
10
0
0
0
20
40
60
80
0
100
2
4
6
8
10
12
File,%
File,%
File, %
File, %
Fig.in8highlights;
Graduation of the reproduction at screen ruling
Figure 8: a) Gradation of the reproduction, b) Gradation of the reproduction
screen ruling: 161 lpi; substrate: paper; plate: thermal photopolymer plate
161 lpi, paper – thermal photopolymer plate
20
18
16
HD C31
14
Print,%
0
14
70
60
9
The graphics on Fig. 9 b show, that on print samples, printed on paper with thermal
plate and screen ruling 174 lpi, the smoothest transition is observed when HD C23 is applied
(Fig. 9 a).
HD C29
12
HD C27
10
8
HD C23
6
Dot=C, 37°,
Bump 3,5%
4
2
0
0
2
4
6
8
10
12
File,%
48
10
Pri
40
Dot=C, 37°,
Bump 4,0%
30
20
10
0
0
20
40
60
80
100
File,%
18
100
16
90
14
80
Print,%
60
Print, %
Print,
%
Print,%
HD C31
12
70
HD C23
50
40
Dot=C, 37°,
Bump 4,0%
30
20
Print,%
10
0
0
20
40
60
80
100
File,%
File,
%
HD C29
10
HD C27
8
100
HD C23
90
6
80
4
70
2
60
0
50
40
Dot=C, 37°,
Bump 4,0%
0
2
4
6
8
10
12
File,%
30
File, %
20b. Graduation of the reproduction in highlights
Fig.
9
Graduation
of
the
reproduction
at screen ruling
10 in highlights;
HD C27
Dot=C, 37°,
Bump 5,0%
0
18
0
16
14
HD C31
80
100
16
90
6
HD C23
80
4
70
Dot=C, 37°,
Bump 4,0%
2
60
0
50
40
60
18
HD C27
100
8
40
20
HD C29
10
HD C27
0
2
4
6
8
10
12
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Bump 5,0%
File,%
30
20b.
Print, Print,%
%
Print,%
Print,
%
Print,%
12
20
The graphics on Fig. 10b show that on print samples, printed on paper with thermal
plate and screen ruling 198 lpi, File,%
the smoothest transition is observed with 27 pixels, i.e. HD
C27 (Fig. 10)
0
9 Graduation of the reproduction at screen ruling
20
40
60
80
HD C31
12
HD C29
10
HD C27
Dot=C, 37°,
Bump 5,0%
6
2
0
0
100
2
4
6
8
10
The graphics on Fig. 10b show that on print samples, printed on paper with thermal
File,%
File,%
%
plate and screen ruling 198 lpi, File,
the smoothest
transition is observed with 27 pixels, i.e. HD
File, %
C27 (Fig. 10) a. Graduation of the reproduction
Fig. in
10highlights;
Graduation of the reproduction at screen ruling
20
12
A print characteristic curve of print samples, printed on polyethylene with thermal
plates and screen ruling 161 lpi is drawn (Fig.11 a) using HD C36, because on Fig.11 b is
seen, that at this value the smoothest transition to zero is observed.
18
16
14
11
HD C23
8
4
Fig.
10
0
14
HD C31
Print,%
A12 print characteristic curve of print samples, printed HD C29
A print characteristic curve of a test target, printed on
on 10polyethylene with thermal plates and screen rulingHD C27 polyethylene with a thermal plate and screen ruling 198
11
1618lpi is drawn (Fig.11 a) using HD C36, because on HD C23 lpi is drawn (Fig.13 a) using HD C27, because on Fig.13b
37°,it is seen that at this value the transition to zero is the
Fig.11
b is seen, that at this value the smoothest transi-Dot=C,
6
Bump 5,0%
tion4to zero is observed.
smoothest.
2
A0 print characteristic curve of a test print, printed
0
2
6
8 and screen
10
12
on polyethylene
with4 thermal
plates
ruling
174 lpi is drawn (Fig.12 a)File,%
using HD C29, as on Fig.12b
Graduation
the reproduction
in highlights
it is seen b.that
at thisofvalue
the transition
to zero is the
smoothest.
12
A print characteristic curve of print samples, printed on polyethylene with thermal
plates and screen ruling 161 lpi is drawn (Fig.11 a) using HD C36, because on Fig.11 b is
seen, that at this value the smoothest transition to zero is observed.
49
12
Print,
HD C27
50
40
Dot=C, 37°,
Bump 3,5%
30
20
10
0
0
20
40
60
80
100
File,%
25
100
90
20
HD C31"
80
Print, %
Print,%
60
Print,
%
Print,%
70
HD C27
50
40
Dot=C, 37°,
Bump 3,5%
30
HD C29
15
120
HD C27
HD C23
100
10
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Bump 3,5%
80
5
Print,%
20
10
0
0
20
40
60
80
100
HD C29
60
0
0
40
2
4
6
File,%
File,
%
8
10
Dot=C, 37°,
Bump 4,0%
12
File,%
File, %
20
Graduation
of theofreproduction
Figure a.
11:
a) Gradation
the reproduction, b) Gradation of the reproduction
in highlights;
Fig. 11 Graduation
screen ruling: 161 lpi; substrate: paper; plate: thermal photopolymer
plate of the reproduction at screen ruling 198 lpi, paper - thermal photopolymer
0
plate
25
0
20
HD C29
120
40
60
80
100
25
HD C27
100
10
20
Dot=C, 37°,
Bump 3,5%
80
5
Print,Print,%
%
HD C23
HD C31
HD C29
Print, %
Print,%
Print,%
HD C31"
15
20
A print characteristic curve
of a test print, printed on polyethylene with thermal plates
File,%
and screen ruling 174 lpi is drawn (Fig.12 a) using HD C29, as on Fig.12b it is seen that at
a. Graduation
this value the transition
to zeroofisthe
thereproduction
smoothest.
60
Dot=C, 37°,
Bump 4,0%
0
0
2
40
4
6
8
10
12
File,%
20
0
20
40
60
80
Print,%
Fig. 11 Graduation of the reproduction at screen ruling 198 lpi, paper - thermal photopolymer
0
plate
100
15
HD C29
120
10
HD C27
HD C23
100
5
13
Dot=C, 37°,
Bump 4,0%
80
0
60
0
2
4
6
8
10
12
HD C27
Dot=C, 37°,
A print characteristic curve File,%
of a test print, printed on polyethylene with thermal plates
File,%
Bump 5,0%
File, %a) using HD C29, as on Fig.12b it is seen that at 40
File, %
and screen ruling 174 lpi is drawn (Fig.12
a.
Graduation
of
the
reproduction
b.
Graduation
of
the
reproduction
in
highlights
this value the transition to zero is the smoothest.
25 Figure 12: a) Gradation of the reproduction, b) Gradation of the reproduction
Fig. 12 20
Graduation
of the reproduction at screen ruling e
in highlights;
174plate
lpi, polyethylene - thermal photopolymer plate
A print characteristic curve of a test target, printed on polyethylene with a thermal
0
20
plate and 0screen ruling
198 lpi 40
is drawn (Fig.13
a) using
HD C27,
because on Fig.13b it is
20
60
80
100
seen that at this value the transition to zero is the smoothest.
120
10
18
HD C23
5
Print,%
Print, %
40
13
Dot=C, 37°,
Bump 4,0%
80
60
0
20
HD C27
100
0
File,%
HD C29
2
4
6
8
File,%
10
12
HD C27
Dot=C, 37°,
Bump 5,0%
Print, %
Print,%
Print,%
HD C31
15
16
14
HD C31
12
HD C29
10
HD C27
8
HD C23
6
Dot=C, 37°,
Bump 5,0%
4
Fig. 12 Graduation
of the reproduction at screen ruling e
20
174 lpi, polyethylene - thermal photopolymer plate
2
A print characteristic curve of a test target, printed on polyethylene with a thermal
plate and0 screen ruling 198 lpi is drawn (Fig.13 a) using HD C27, because on Fig.13b it 0is
0
20
40
60
80
100
0
seen that at this value the transition to zero is the smoothest.
File,%
2
4
6
8
10
14
12
File,%
File, %
File, %
Fig. 13 Graduation
of the reproduction at screen ruling
in highlights;
198plate
lpi, polyethylene - thermal photopolymer plate
18
20
Print,%
16
Comparison of the print quality for digital plate making with thermal plates, at screen
ruling 174 lpi, with a selected value HD C46 and without applying HD Flexo is given on Fig.
14.
14
HD C31
12
HD C29
10
HD C27
8
HD C23
6
Dot=C, 37°,
Bump 5,0%production
4
50
14
Analysis of the received results
The conclusion is that the HD Flexo technologies are suitable for testing standard
conditions and allow for increasing the print quality of the image.
for both substrates.
Comparison of the print quality for digital plate making
with thermal plates, at screen ruling 174 lpi, with a
selected value HD C46 and without applying HD Flexo is
given on Figure 14.
(a)
(b)
a. Conventional screen
16
Figure 14: Comparison of tested print samples, a) Conventional screen, b) Using HD Flexo C46
.
b. Using HD Flexo C 46
Fig. 14 Comparison of tested51
print samples
4. Conclusions
References
The conclusion is that the HD Flexo technologies are
suitable for testing standard production conditions and
allow for increasing the print quality of the image.
When using HD Flexo technology, the reproduction in
highlights and transitions to zero is improved.
Increased screen ruling allow better reproduction in
mid tones, neutralizing the negative effect of visible
rosettes in grey and full color areas of the image.
The digital printing plates reproduce the tonal range
better, with finer details and with a decrease in the dot
gain.
Screen ruling selection must be based on particular
print conditions, design characteristics, screen ruling for
the image and for aniloxes, and should be specified in a
way to achieve the best results when HD Flexo is used.
The higher screen ruling of the image leads to a
higher quality only if the proper screen and anilox ruling
combination is selected and necessary settings on HD
Flexo are correctly applied.
It was established, that after the implementation
of the new technology HD Flexo, the quality of the
received imprints has been significantly ameliorated, and
the smooth reproduction of the bright tones and the
transition to zero is ameliorated as well.
Based on the recent research, the printed test trials
and the print result evaluation, the best settings for
solvent and thermal plates were specified for printing
on two mostly used print substrates – polyethylene and
paper.
For polyethylene and for paper, the best results were
achieved for screen ruling 174 lpi and HD C46 when
printed with solvent plates.
For thermal plates, best results were achieved for
screen ruling 161 lpi and HD C27 for both substrates.
[1] Computer to Plate for flexography: Key aspects of
the technology, Moscow, 2001.
[2] Ganchev, A. (2004): New technologies for elaborating of plates for flexoprinting. Packing and printing,
No.1.
[3] Sardjeva, R. (2009): Technologies for printing. Pub.
Ciela, Sofia.
[4] Barco Graphics (2000): Samba Flex Screen User
Manual. Gent, Belgium.
[5] Gantchev, A.: “Technology of the screening at
flexoprinting”
[6] Company materials of DuPont
[7] Pavlova, N.; Bozhkova, T.; Gantchev, A. (2010):
Digital technologies for elaborating of flexoprinting
plates. Packing and printing, No.2, pp 7-12.
[8] Rozalinov, D. (2005): Technology of the packing
from papers and cardboards. Sofia, Bulgaria.
[9] Kipphan, H. (2001): Handbook of Print Media,
Technologies and Production Methods. Springer
Verlag, Heidelberg, Berlin.
[10] Katchin, N.; Spiridonov, I. (2000): Printing processes
Part 1: Theoretical bases. Sofia, Bulgaria.
[11] Rozalinov, D. (2004): Characteristics of anylox
(screen) rolls. Printing and packing.
[12] Rozalinov, D. (2005): Control of anylox (screen)
rolls. Packing and printing.
[13] Rochester Institute of Technology (2006): A Study
of Producing Smoother Gradients in the Flexographic Process on Oriented Polypropylene with
UV Ink by Varying Screening Techniques, Gradient
Lengths and the Surrounding.
[14] http://www.kursiv.ru/kursivnew/flexoplus_magazine/
[15] http://gallery.unipack.ru/company_rubric/703/
[16] Esko Artwork- HD Flexo Application Guide
52
Tatiana Bozhkova
A. Ganchev
Jana Kisova
Department of Pulp, Paper
and Polygraphy,
University of Chemical
Technology and Metallurgy,
Sofia,
Bulgaria
and Polygraphy,
Sofia,
Bulgaria
and Polygraphy,
Sofia,
Bulgaria
[email protected]
53

Optimizing HD Flexo for Different Plate Technologies and Substrates

Transcription

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