pro active management of visual appearance of products
TRANSCRIPT
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Pro-active Management of Visual
Appearance of Products: from the
Automotive Sector to other Industries
Fco M. Martínez-Verdú
Color & Vision Group: http://web.ua.es/en/gvc
University of Alicante (Spain)
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Visual appearance of products Color & Texture managed currently in the automotive sector
Challenges for its optimal and efficient management Multi-scale approach (bottom-up vs. top-down)
Foundations for pro – active Quality Management: Visual and instrumental correlation
Multivariate statistics: visual psychophysics, DoE, etc.
Conclusions
OUTLINE
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Great variety of visual attributes in daily products
VISUAL APPEARANCE OF PRODUCTS
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VISUAL APPEARANCE OF PRODUCTS
Dyes & Pigments
New visual appearance
attributes
Multi-functional properties
Coloration processes
Market forces: performance – cost balance,
customer preferences, etc.
Continuous loop
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Color & Texture
Reflection & Transmission
Goniochromatism: BRDF
Sparkle & Graininess
VISUAL APPEARANCE IN AUTOMOTIVE
® Wikipedia
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MSc degree in Color Technology for the Automotive Sector
VISUAL APPEARANCE IN AUTOMOTIVE
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• Bottom – up:
• Many variables
• Impracticable
• Top – down:
• Feasible
• How?
CHALLENGES: MULTI – SCALE APPROACH
Color, Texture
Radiative
transfer theory
Particles
interaction
Light – Matter
interaction
particle models
Light sources tech.,
Pigments, dyes
Gloss, sparkle, etc.
Color differences
Visual appearance
Emission SPD(l)
Reflection r(l)
Transmission t(l)
Coefficients:
Absorption K
Scattering S
Substrate
Coloration
application
processes:
no. layers, etc.
Phys. + Chem.
Particles & Substrate:
Size, Shape, Thickness
Refraction index,
Extinction index,
Roughness, etc.
TH
EO
RE
TIC
AL
AP
PR
OA
CH
EX
PE
RIM
EN
TA
L A
PP
RO
AC
H
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• But, in this case (empirical approach = top – down), the
typical challenge is how we can understand and manage
by a pro-active way the relevance and interplay of
nano/micro (structural) parameters, and other ones
(coloration application processes, optical, etc.), on final
visual appearance attributes (color, texture, etc.).
• HOW?
• Metrology, Visual Psychophysics, and Statistics
• inter and multi-disciplinary (hybrid) approach
CHALLENGES: MULTI – SCALE APPROACH
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• IDEAL CONTEXT:
• BiRD motto:
• What You See Is What
You Measure Rightly = WYSIWYMR
• ICC profile format (Graphics Arts)
• Objective: WYSIWYG
VISUAL & INSTRUMENTAL CORRELATION
Instrumental scaling
Vis
ual assessm
en
t
?
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VISUAL & INSTRUMENTAL CORRELATION
Visual appearance of materials
DT = f(DE, DG, DS, ...) is the “GOAL”
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• Human visual perception tasks:• Detection
• Influence of viewing distance and geometry
• Spatio-chromatic dithering
• Scaling (ordering: from less to more)• Color (from spectral data to 3 dim.),
• Sparkle (2 dim.), Graininess (1 dim.), etc.• Color & Texture palettes
• Discrimination (differences):• Perceptibility vs. Acceptability
• FAIL vs. PASS controls by tolerance ellipses
VISUAL & INSTRUMENTAL CORRELATION
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Special equipment: Tele-spectro-radiometer
Radiometric, photometric and colorimetric measurements
without contact, and adjusted to the target size
Spectrofluorimeter
Multi-angle spectrophotometers
Lighting cabinets for visual assessments
VISUAL & INSTRUMENTAL CORRELATION
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UA – Research Technical Services:
XPS, WDX, FRX, SEM, FT-IR, ATR, Raman, etc.
Pending advanced instrumentation
multi – angle spectroscopic ellipsometry
spectral constants of absorption (K) and scattering (S) to different measurement
geometries (irradiation / observation)
multi-angle micro-spectrophotometer
X-CT (tomography)
(3D) transversal scanning of nanomaterials, etc.
interferometric microscopy using white light
3D surface contactless profilometer
VISUAL & INSTRUMENTAL CORRELATION
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• Current challenges in color industries:• Gonio – appearance: color & texture
• Spectral BRDF own color palette
• Formulation of new colors outside Rösch – McAdam solid
• Tolerances Total Visual Appearance (color, gloss, sparkle, etc.)
• Measurement without contact (by tele – spectroradiometer, etc.)• Reversible or irreversible electro / thermo- chromism, etc.
• Real colored products vs. its efficient digital simulation• Color gamut of displays technologies
• Pro – active prediction models for visual quality of products
VISUAL & INSTRUMENTAL CORRELATION
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Products: why? Earn money being competitive (Porter)
by differentiation: and better than … , impossible to be copied, etc.
faith perceptually digital simulation to the original
specific colors & textures functional (added value from color: resistance, etc.)
gonio – apparent
fluorescent, thermochromic, etc.
viewing distance effect: spatio – chromatic dithering near vs. far
lighting conditions changes effect: type of light source (wLED, etc.)
type of measurement geometry: diffuse vs. directional (gonio - )
MULTIVARIATE STATISTICS
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Processes: why? how? when? Design and production easy to be managed
Feasibility & stability of original product model (std. or master)
Ease for creativity & innovation
Repeatability & accuracy of batches Measure to save time & money:
Comparison with error range TOLERANCE
Multi – scale process: nano/micro visual From bottom – up approach top – down
Predictive model of pro – active management by: Statistical design of experiments (DoE)
Regression models
MULTIVARIATE STATISTICS
DEAUDI2000 < 2 = 1.41 OK
DEAUDI2000 [ 2 , 3 = 1.73] cOK
DEAUDI2000 > 1.73 FAIL
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• Statistical Design of Experiments (DoE)• Statistical technique used in quality control for planning,
conducting, analyzing, and interpreting sets of experiments
aimed at making sound decisions without incurring a too high
cost or taking too much time• Qualitative and quantitative variables optimization objective
• Selection of the minimal number of samples
• Non-linear / linear multidimensional regression models• Increasing sampling for an optimal prediction model
• even combining qualitative and quantitative (measureable) variables
MULTIVARIATE STATISTICS: DoE
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• Problem formulation• Aim (reproducible and measurable)
• Relevant factors (qualitative and quantitative)
• Screening design• Selection of levels for each factor
• Experiments (no. of samples)
• Analysis of the raw data
• Data analysis (Pareto, regression, etc.)
• Optimization & Robustness studies
MULTIVARIATE STATISTICS: DoE BASICS
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1 – Sparkle detection distance vs. metallic pigment size & shape
2 – Sparkle detection distance vs. concentration, achromatic
background, illuminance level & pigment type
3 – Sparkle detection distance vs. colored background
4 – Color matching vs. silver finishing process on a coated plastic
5 – Gonio-appearance of 3D printed parts vs. 3D printing technology
and its sub – processes
FIVE DoE EXAMPLES
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• Relevance and interplay of colored backgrounds by CIE-L*C*abhab
• Fixed structural and environmental data (factors)• Color mix: variable solid pigment + fixed effect pigment
• L*: 3 levels• C*ab: 3 levels• hab: 4 levels
SPARKLE DETECTION DISTANCE
Complete multi-level factorial table of experiments (samples)
Sample no. C L h Sample description [Hue / Lightness / Chroma]
1 0 1 1,00 RED / LIGHT / MEDIUM
2 1 -1 1,00 RED / DARK / STRONG
… … … … …
13 -1 1 -1,00 GREEN / LIGHT / WEAK
14 -1 -1 0,33 BLUE / DARK/ WEAK
… …
23 0 1 0,33 BLUE / LIGHT / MEDIUM
24 0 -1 -0,33 YELLOW / DARK / MEDIUM
… … … … …
34 1 0 1,00 RED / GRAY / STRONG
35 0 0 0,33 BLUE / GRAY / MEDIUM
36 -1 1 1,00 RED / LIGHT / WEAK
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• Goal: color matching (DEab = 0), L* = 82 , & maximum transparency
• Initial DoE proposal: Taguchi L16 (215-11) Matrix, before analysis
COLOR MATCH vs. SILVER FINISHING
Worksheet MEASURED RESPONSES
Nº experim. MaterialPVD
Thickness
PVD
Conc.Topcoat
Topcoat
RobotBasecoat
Basecoat
Robot DEab L* Transparency (T)
1 Metal A
Low
Low Low
translucent
white
Low Low Low
2Metal B
HighHigh High
3High
Low
4 Metal AHigh Low Low
5 Metal CLow
High
translucent
white
6Metal D
LowHigh High
7High
High
8 Metal CLow Low
Low
9 Metal A
High
LowHigh
10Metal B
HighHigh Low
11High
Low
12 Metal AHigh Low High
13 Metal CLow Low
translucent
white
14Metal D
LowHigh Low
15High
High
16 Metal C Low Low High
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• Can 3D printed parts for cars (body or interior) equal or better
color & texture without losing phys – chem performance?
• DoE aims: high sparkle, flop, chroma, colorfastness, etc.
• Factors:
• Qualitative:
• Technologies: FFF or FDM, MultiJet Fusion, ColorJet, Powder-bed, living AM, etc.
• Materials: (bio)polymers, pigments, additives, process sequence, etc.
• Quantitative:
• Temperature, irradiation, speed, layer height, infill, head size, etc.
GONIO-APPEARANCE IN 3D PRINTED PARTS
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• FFF experiment table (Taguchi L9): PLA fixed, simple interactions
• Head size (mm): 3 levels
• 100, 200 & 300
• Speed (mm/s): 3 levels
• 20, 40 & 60
• Infill (%): 3 levels
• 0, 20 & 100
• Color: 3 levels
• Without pigment
• Solid or special-effect pigment
GONIO-APPEARANCE IN 3D PRINTED PARTS
Sample no. HEAD SPEED INFILL COLOR
1 1 3 2 3
2 3 2 2 1
3 1 2 3 2
4 3 1 3 3
5 3 3 1 2
6 2 1 2 2
7 2 3 3 1
8 1 1 1 1
9 2 2 1 3
Plane printed samples for measuring flop
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• FFF experiment tables:
• Complete multi-level factorial:
• All previous factors with 2 levels, except color set = 24, all possible interactions
• Multi-level factorial + D – optimal design
• Only speed with 2 levels complete set = 54, but optimally reduced to 21
• Multi-level factorial + D – optimal design:
• All factors with 3 levels + new factor (polymer: ABS & PLA) complete set = 162, but
optimally reduced to 21, and simple interactions well detected
• Multi-level V2 factorial + D – optimal design:
• Only speed and polymer with 2 levels from 108 to 21, quadratic interactions
GONIO-APPEARANCE IN 3D PRINTED PARTS
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Hybrid multi – scale approach for visual appearance of materials
applied successfully in automotive can be extended to other
industries as ceramics, coatings, cosmetics, plastics, printing, etc.
Structural elements (pigments, etc.), advanced instrumental techniques,
visual and instrumental correlation methods, statistics (DoE, etc.), can save
time and money to implement new color & texture quality controls
successfully, etc., and even to make easy new competitive advantages for
companies.
CONCLUSIONS
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Pro-active Management of Visual
Appearance of Products: from the
Automotive Sector to other Industries
Fco M. Martínez-Verdú
Color & Vision Group: http://web.ua.es/en/gvc
University of Alicante (Spain)