Th The Effect of f Contact Roller Topography on Cleanability in in Roll-to to-Roll l Manufacture Student: Dan Miszewski-Wall Supervisor: Professor Liam Blunt
Project Brief • Quantitatively evaluate the cleanability of several Teknek contact rollers with respect to contact roller surface topography.
Project Objectives • Measure cleanability of different contact roller surface topographies on PET film. • Quantitative data analysis relating the contact roller surface topography to cleanability. • Hypothesise the relationship between contact roller surface topography and cleanability.
Project Background Surface Cleanliness, Cleanliness Methods & Particle Adhesion
Surface Cleanliness in R2R • Surface cleanliness of the film is vital during production as any defects (e.g. dust particles) may lead to reductions in product yield. • “ Surface cleanliness is achieved when product functionality is not hindered as a function of contamination ” (Hovestad, 2015). (a) (b) (c) Negative Effects of Contamination Within R2R Manufacture (Teknek, 2015)
Local Vs Global Substrate Cleaning Local Global (NanoMend) (Teknek)
CO 2 Snow Cleaning • Local, contact free cleaning method. • Expensive - gas consumption. • Risk - substrate deformation. Web Direction Left to Right TNO R2R Lab Pilot Scale CO 2 Cleaning (Hovestad, 2015) • Sensors required to detect contamination. (a) (b) Cleaning Mechanisms; (a) Momentum Transfer (b) Organic Removal (Kohli & Mittal, 2008)
Contact Cleaning • Global cleaning method. • One of the most efficient methods with minimal environmental impact. Teknek Contact Roller (Ope Journal, 2014) Efficiency of R2R Cleaning Methods (Teknek, 2015) • Efficiency dependent on particle adhesive forces. Teknek Contact Roller Cleaning Mechanism
Particle Adhesion • The two dominant forces which cause a particle to adhere to a surface are van der Waals and electrostatic interactions (Kohli & Mittal, 2008). • Van Der Waals - all attractive intermolecular forces acting between electrically neutral particles. Adhesion Forces as a Function of Particle Diameter (Hamilton, 2012) • Electrostatic - occurs when two materials of opposing charges are attracted to each other. (a) (b) (a) Van der Waals & (b) Electrostatic Attraction Interaction Illustrations (Mattson, 2014)
Surface Roughness • Surface roughness is a function of particle adhesion. • Highest particle adhesion occurs when the particle size matches the surface asperities. Adhesion as a Function of Contact Area (Hamilton, 2012)
Methodology Contact Cleaning Trials & Contact Roller Surface Characterisation
Surface Contamination Measurement Standardised Sample Size Specimen Fixture Design 35mm Photography Frame Specimen Holder Lego Specimen Fixture
Surface Contamination Measurement Keyence – Light Settings Keyence – Data Capture Keyence Observation of Paper Fibre & Human Hair Sample Measurement at 50x Magnification
Contamination Modelling Natural Contamination Polystyrene Micro Particles Natural Contamination Collected From A Clean Room Uniformly Sized Polystyrene Micro Particles Were Office; Representative Of R2R Environment Used To Artificially Model Surface Contamination *U *Use sed as Mod odel Conta tamination In n NanoMend Proje ject
Contact Cleaning Trials Three cleaning trials performed in total using a single pass of each contact roller; 1. Natural Contamination 2. Natural Contamination (Anti-Static) 3. Polystyrene Micro Particles Teknek Handheld Contact Roller
Contact Cleaning Station b a c d (a) Ioniser Blow Gun (b) Teknek Hand Contact Roller (c) Teknek FastPad (d) PET Film Sample
Quantitative Analysis - ImageJ • Open source image processing program which includes software enabling scientific image analysis. • Particle Analysis enabled analysis of data captured by Keyence. ImageJ Post-Processing to Analysis Phase (ImageJ, 2016)
Quantitative Analysis - ImageJ Natural Contamination Polystyrene Micro Particles ImageJ Automatic Particle Analysis ImageJ PointPicker Analysis Tool
Contact Roller Surface Characterisation Alicona InfiniteFocus Contact Roller Measurement Contact Roller Surface Measurement in SurfStand
Results
Natural Contamination Anti-Static Effect on Cleanability Defect Density After Single Roller Pass 6000 5000 Defect Density (um 2 ) 4000 3000 2000 1000 0 PANEL FILM NANO ULTRA UTF Contact Roller Variant Natural Contamination Natural Contamination Anti-Static
Polystyrene Micro Particles Polystyrene Micro Particle Reduction After Single Roller Pass 100% Polystyrene Micro Particle Reduction (%) 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% PANEL FILM NANO ULTRA UTF Contact Roller Variant
Contact Roller Surface Characterisation Two Subgroups Identified; 1. 1. Panel el & Film ilm Low Average Surface Roughness (Sa) Sm Smooth surface Low Developed Interfacial Ratio (Sdr) Low surface area Negative Skewness (Ssk) Valley dominated surface Low RMS Surface Slope (Sdq) Low degree of surface slopes Low Auto-Correlation Length (Sal) Finely spaced surface textures Low Shore Hardness Sof Soft material 2. 2. Nano, Ultr ltra & UTF High Average Surface Roughness (Sa) Roug ough surface High Developed Interfacial Ratio (Sdr) Large surface area Positive Skewness (Ssk) Peak dominated surface High RMS Surface Slope (Sdq) High degree of surface slopes High Auto-Correlation Length (Sal) Widely spaced surface textures High Shore Hardness Har ard material
Cleanability Trial Evaluation Co Contact Roll oller Cl Cleanabil ilit ity Ra Rankin ing Cleanin Cl ing Tri rial 1 2 3 4 5 (Best) (Bes (W (Wor orst) 1. 1. Na Natural l Co Contamin inatio ion ULTRA NANO UTF PANEL FILM 2. 2. Na Natural l Co Contamin inatio ion (An (Anti-Static ic) NANO FILM PANEL ULTRA UTF 3. 3. Poly olystyrene Mi Micro Par artic icle les ULTRA NANO FILM UTF PANEL * Cleaning Trials 1 & 2 ranked by Defect Density Reduction %. Cleaning Trial 3 ranked by Particle Count Reduction %
Cleanability Trial #1 • Higher surface area may increase contact area between the adhered particle and roller, thus increasing particle removal effectiveness. • Nano & Ultra feature longitudinal ridges along the roller axes which may serve to mechanically shear the adhered particle from the surface. Contact Roller Cleanability Ranking Cleaning Trial 1 2 3 4 5 (Best) (Worst) • UTF has scattered islands which 1. Natural Contamination ULTRA NANO UTF PANEL FILM may explain its comparatively 2. Natural Contamination (Anti-Static) NANO FILM PANEL ULTRA UTF inferior cleanability. 3. Polystyrene Micro Particles ULTRA NANO FILM UTF PANEL
Cleanability Trial #2 • All contact roller variants demonstrated high cleanability > 80%. • Comparison of trials 1 & 2 suggest rougher rollers demonstrate the highest cleanability when electrostatic forces are present. • Film & Panel are both ‘soft’. Contact Roller Cleanability Ranking Cleaning Trial 1 2 3 4 5 Able to deform around adhered (Best) (Worst) particles, increasing the contact 1. Natural Contamination ULTRA NANO UTF PANEL FILM area, thus increasing particle 2. Natural Contamination (Anti-Static) NANO FILM PANEL ULTRA UTF removal effectiveness. 3. Polystyrene Micro Particles ULTRA NANO FILM UTF PANEL
Cleanability Trial #3 • All contact roller variants demonstrated high cleanability > 90%. • Two similarities between trials 1 & 3; Electrostatic forces were present and both Ultra and Nano demonstrated the highest cleanability. Contact Roller Cleanability Ranking Cleaning Trial 1 2 3 4 5 (Best) (Worst) 1. Natural Contamination ULTRA NANO UTF PANEL FILM 1. Natural Contamination (Anti-Static) NANO FILM PANEL ULTRA UTF 3. Polystyrene Micro Particles ULTRA NANO FILM UTF PANEL
Summary • Nano demonstrated the most effective cleanability; • ‘Rough’ surface topography proven to be more effective than ‘smoother’ surfaces at overcoming electrostatic adhesion forces. • Longitudinal ridges which were thought to increase particle removal effectiveness by mechanically shearing adhered particles from the surface. • Nano was found to have inherent static dissipation properties. • No clear correlation between topography and cleanability over 3 cleaning trials. • Different topographies excelled in each cleaning trial, suggesting specific topographies are required for optimum cleaning of specific applications.
Conclusions
Conclusions • Method developed to quantitatively measure contact roller cleanability. • Removal of electrostatic demonstrated enhanced or parity cleanability. • All rollers demonstrated cleanability >90% of polystyrene micro particles. • Relationship between roller topography and cleanability was hypothesised. • Results suggests there is no set topography which provides optimum cleaning for all applications, rather certain topographies are suited to specific applications.
NanoMend In Process Surface Metrology for High Value Manufacturing Prof Liam Blunt Project Co-ordinator NanoMend Project/University of huddersfield The NanoMend project has received funding from the European Community’s Seventh Framework Program (FP7/2007-2013) UNDER Grant Agreement No. 280581
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