bogota 2013 gotsick v1.5
DESCRIPTION
Given at the Novaflex Flexo meeting in Bogota on May 28, 2013.TRANSCRIPT
The Effect of Flexo Dot Geometry on Print Performance:
Theoretical and Empirical Models of Dot Gain Mechanisms
Timothy Gotsick
May 28, 2013
MacDermid Printing Solutions
A little bit about myself…
2
In my natural habitat, waiting for a delayed flight.
Timothy Gotsick, VP Technology• R&D• Application Development• Based in Atlanta, GA
• 10 years with MacDermid• Background in organic chemistry
• Still being tutored in print technology
• Management of new product development in chemical industries• Strong interest in understanding print fundamentals
Outline
• What is Print Gain?• Why and where is it a problem?• What causes Print Gain?• The effect of shoulder angle on print gain• Case Study: Corrugated Postprint “Fluting”• Case Study: Highlight dot gain• Further work: Effects of dot shape on ink distribution
4
Print is made of 2-D dots
5
Plates are made of 3-d dots
x
y
z
The 3rd Dimension
What is Print Gain?
Plate10%
Print25%
Standard Gain Analysis
CYAN
0%
10%
20%
30%
40%
50%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
REPRO
PR
INTThe Press
“The Black Box”
But where does print gain come from?
What are the root causes of dot gain?
Mechanism
Factors
Type of Effect
Print Result Dot Gain
Mechanical
Ink Spreading
Ink Rheology Substrate-Ink Interaction
Dot
Deformation
Inking (Anilox) Printing (Substrate)
Optical Density
Uniformity Smoothness
Truly Big Dots
• Molded from 32 Shore A photopolymer• 7 cm tall• 1 cm tip• Θ = 53°, 62°, 71°, 79°
Θ
Dot Compression Analyzer
Digital force gauge
Compression adjustment mechanism
The Dot
‘Print’ surface
Dot Compression LIVE!
Contact Patch Expansion
Compression
Contact Patch Measurement
Contact Patch Growth
0 2 4 6 8 10 12 14 16 18 2050
100
150
200
250
300
350
400
450
500
Contact Patch vs Compression by Angle
79
71
62
53
Compression, mm
Co
nta
ct P
ath
, m
m2
Dot Force vs Compression
0 2 4 6 8 10 12 14 16 18 200
10
20
30
40
50
60
Force vs Compression for multiple dot shoulder angles
53
62
71
79
Compression, mm
Fo
rce
, N
Dot Force Increase
Compression
CORRUGATED POSTPRINTCase Study
The Problem
Board vs Dot
• Board structure changes the impression level experienced by dots across the surface of the board– Dots printing on flute ‘tip’ are harshly compressed– Dots printing on flute ‘valley’ are minimally compressed
Print Pressure Variations
“Striping on Flexo Post-printed Corrugated Board”Martin Holmvall, Thesis Fibre Science and Communication Network, Department of Natural Sciences, Mid Sweden University, SE-851 70 Sundsvall, Sweden, 2007
36.1%7.43 mils
42.9%8.12 mils
Quantifying Fluting
Dot Shape affects Fluting
Liquid
12 13 2 140.0
1.19%Least Most
9
6.12%4.29%2.69%
Digital #14
Digital #12
Digital #13
Analog #2
7.0
Light Compression in Valleys
0 2 4 6 8 10 12 14 16 18 2050
100
150
200
250
300
350
400
450
500
Contact Patch vs Compression by Angle
79
71
62
53
Compression, mm
Co
nta
ct P
ath
, m
m2
High Compression at Tips
0 2 4 6 8 10 12 14 16 18 2050
100
150
200
250
300
350
400
450
500
Contact Patch vs Compression by Angle
79
71
62
53
Compression, mm
Co
nta
ct P
ath
, m
m2
Dot Shape sets Compression Response
Standard Digital
LUX Digital
Dot shapes
Dots Angle → F-factor
49 → 3.24
52 → 4.18
73* → 2.01
71* → 2.34
* Near dot top
Conclusions (pt. 1)
• Fluting is caused by differences in the impression environment the dots are subjected to at the flute tips and valleys
• Dot shoulder angle influences dot gain because:– Contact patch size (gain) increases with impression, but it
increases less for dots with shallower shoulder angles– Impression force increases with impression, but it increases
less for dots with shallower shoulder angles
• The dot shoulder angle model of gain prediction seems to explain empirical results well
HIGHLIGHT DOT STABILITYCase Study
The Quest for the Smallest Dot
1% <1%
Dot size vs stability: How low can you go?
Gain throughout the tone range
0 10 20 30 400.00
1.00
2.00
3.00
4.00
5.00
Theoretical
Measured
174 lpi File Dot Size, %
Do
t D
iam
eer,
mil
s
Gain is a bigger problem for smaller dots
0 10 20 30 400%
50%
100%
150%
200%
250%
300%
350%
400%
f(x) = 3.67285241014326 x^-0.536863975468506R² = 0.977911271044202
Gain vs Dot Size
174 lpi File Dot Size, %
Inc
rea
se
in D
ot
Siz
e f
rom
File
to
Pri
nt
Dot Compression, 79° shoulder
When Dots Fail
0 2 4 6 8 10 12 14 16 18 200
10
20
30
40
50
60
Force vs Compression for multiple dot shoulder angles
53
62
71
79
Compression, mm
Fo
rce
, N
Dot F
ailure
Round Top Dot Flat Top Dot
Dot Shape Test
Effect of Dot Shape on Stability
0 2 4 6 8 10 12 14 16 18 200
10
20
30
40
50
60
Flat Top Dot 79-2a
Round Top Dot 79-2
Compression, mm
Fo
rce
, N
DOT SHAPE EFFECTS ON PRINTING PRESSURE
Further Work
What are the root causes of dot gain?
Mechanism
Factors
Type of Effect
Print Result Dot Gain
Mechanical
Ink Spreading
Ink Rheology Substrate-Ink Interaction
Dot
Deformation
Inking (Anilox) Printing (Substrate)
Optical Density
Uniformity Smoothness
Ink Flow Effects on Gain
Printing Pressure
0 2 4 6 8 10 12 14 16 18 200.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Pressure vs Compression
79
71
62
53
Compression, mm
Pre
ssu
re,
N/m
m2
Industry Perspective in 2013
Flat top dots are important, but…
1.Are they all the same?
2.What is the best way to make them?
42
ConeAnalog Compound
Not all Flat Top Dots are Equivalent
DigitalKodak NXDigiFlow
Esko FTDFlint NExT
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LUX: It is that simple
Existing process LUX process
Ablate Plate
Digital Plate Expose Process
Plate
StandardDigital Plate
Me
mbr
ane
Remove Membrane
LUX Lamination
LUX Dot Formation
UV UV UV
O2 O2
Optimizing Dot Profile
• Lots of dots work. Some dots work better. – These factors seem to matter most
46
Dot SurfaceMorphology Shoulder AngleValley DepthEdge definition Dot Surface
47
Thank You
Timothy GotsickVP Technology, MacDermid Printing [email protected]://www.macdermid.com/printing
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