Whodat? Whodunit? Solving U V Cu r in g Mysteries with Measurement Jim Raymont
Solving UV Mysteries Anything that you can measure, you have a better chance of controlling. Things that you do not measure become the cause of mysterious problems Larry Goldberg-Beta Industries UV Can Be Mysterious Unless You Understand It • Cannot see it with the visible eye • Wavelength is a nanometer (nm)-a billionth of a meter • Reduce UV mysteries and process variables to increase profit • Ask questions as we go • Will share this presentation as PDF • Here to help during the SGIA show (Booth 2800)
UV Curing-Crime Scene Producing a large amount of product before detecting a problem.
Round Up The Usual Suspects Suspect 1A: The Formulator Suspect 1B: The Equipment Supplier
Please Describe the …….. � Abrasion Resistance � Tensile Strength � Scratch Resistance � Gloss � Chemical Resistance � Coating Viscosity � Hardness � Film Thickness � Weatherability � Ability to Over Coat � Non-Yellowing � TBD � Flexibility � TBD What properties are formulation driven? What properties are process/UV source driven?
The UV Process
The UV Process-Analogy Cake: Bake at 350 ° F for 30 minutes Oven Temperature ( ° F) is similar to Irradiance (Watts/cm 2 ) Bake Time (Minutes or seconds) is similar to Energy Density (Joules/cm 2 ) Not Specified: Oven Type Changing the Cake Process Window • 350 ° X 30 = 10,500 Equal Degree Minute Options • 700 ° F for 15 minutes? • 175 ° F for 60 minutes? What if the cake mix only gave you the time?
Speaking the Same Terminology Irradiance (Intensity) • Expressed in watts or milliWatts per square centimeter (W/cm 2 or mW/cm 2 ) • Total radiant power of (all) wavelengths passing from all incident directions onto an infinitesimally small area (cm 2 ) • Depth of cure, penetration through pigments and opaque colors, adhesion to the substrate Energy Density (Dose) • Expressed in Joules (J/cm 2 ) or milliJoules (mJ/cm 2 ) per square centimeter • Incorporates time as part of the measurement • One watt for One second = One Joule • Area under the irradiance curve • Often the only UV exposure guide number supplied
Speaking the Same Terminology Peak Irradiance Time Communication • Process Development • Transition to Production • Production • Within a company • With Supply Chain
Speaking the Same Language Broadband UV Spectrum • UVA: 320-390nm “Black light”, UV Inks, adhesion • UVB : 280-320nm “Toughness” , skin response • UVC : 200-280nm, germicidal (254 nm), surface cure, tack, chemical or scratch resistance • UVV : 395-445nm, opaque/white, thick coats, adhesion, depth of cure Broadband Instrument Responses • Instrument Bandwidths are not defined and vary from manufacturer to manufacturer and how they are specified • EIT UVA 320-390 nm, Full Width Half Max (FWHM), CWL 365 nm • IL UVA 250-415 nm CWL 365 nm IL UVA UV LEDs 250-415 EIT nm Discussed UVA 320- 390 nm Later
Process Window “I am loose and tight in all the wrong places”
Process Window • The range in which a process will work with the desired results – Adhesion, hardness, flexibility, gloss, texture, stain or scratch resistance, chemical rub, cross hatch, abrasion rub, color ID, registration – Often a compromise • Invest before production & confirm when things are working! – Starting guidelines from formulator? – Define your lower limits and document the readings – Increase line speed/decrease applied power until you undercure, note readings and cushion by 20% – Upper limits? • Monitor your readings by job, hour, shift or day as required to maintain quality • Establish your process window during the design/development phase and start monitoring from day one in production
Process Window • Starting Point: Formulator Guidelines • Testing can define a process window Lab testing is less expensive than production testing or • no process window Variables: • Line speed • Lamp distance • Lamp output • Bulb Type • Source Type • Coating
Process Window Normal Operating Window Caution 20% Undercure Buffer Range Stop!Undercure Limit Over cure or over temperature ?
Gathering UV Evidence We can’t ask a UV lamp or a power supply to confess, but we can gather evidence using other means…
Gathering UV Evidence “ Did you perform the maintenance? Did You?”
Gathering Evidence
Gathering UV Evidence Right Tools? • • Right Tests? • Right Expectations? • Documentation?
Gathering UV Evidence = Gather and preserve evidence to use it for when conditions change
Preserving UV Evidence For each UV lamp system • Hour meter • Indicated vs. actual process speed • Power settings (WPI, Amps) Irradiance (W/cm 2 ) • Radiant Energy Density(J/cm 2 ) • • Lamp matched to chemistry • Focus/Reflector condition Poor chain of custody • TBD Line Speed Dwell UV System: North Line Lamp: 2 Time Date FPM/RPM Ind. Actual. Power Hour Irradiance Energy Density (W/cm 2 ) WPI Meter (J/cm 2 ) 10/9 25 22 400 780 0.859 1.45
Gathering UV Evidence Profiling Radiometers Focused lamp • Profile helps determine focus of system and tracks changes UV W/cm 2 • Lamp types • Break down multi-lamp systems Time in seconds Distance Change-Same lamp Non-Focused lamp FOCUSED 858 mW/cm 2 2096 mJ/cm 2 UV W/cm 2 UV W/cm 2 NON-FOCUSED 290 mW/cm 2 1707 mJ/cm 2 Dimensional Curing Gloss Control Time in seconds Time in seconds
Gathering UV Evidence Differences in: • Irradiance values • Lamp Types • Focus of Lamps • Speed collected A typical Irradiance Profile
Gathering UV Evidence In God we trust, all others bring data Dr. W. Edwards Deming
Gathering UV Evidence What Data (Evidence) Is Needed? • Consistent Data Collection Techniques • Fooled by the Equipment? • Do not contaminate the crime scene or • measurement tools
Gathering UV Evidence Unit Ref Readings Readings % Deviation Power Puck Power Puck Unit II II s/n 15678 17654 Speed (f/m) 25 feet/min 25 feet/min UVA mJ/cm2 mW/cm2 mJ/cm2 mW/cm2 mJ/cm2 mW/cm2 1 109.000 450.000 99.000 445.000 -9.17% -1.11% 2 105.000 442.000 103.000 461.000 -1.90% +4.30% 3 104.000 460.000 109.000 439.000 +4.81% -4.57% Average 106.000 450.667 103.667 448.333 -2.09% -0.46% % STEDV 2.496% 2.001% 4.855% 2.537% 7.142% 4.488% Repeat for other UV bands
Analyzing the UV Evidence A Scandal in Bohemia
My Best Cases Inspector Jacques Clouseau : It's amazing how he fell perfectly into the chalk outline on the floor. Ponton : I think they drew the outline after he was shot. Inspector Jacques Clouseau : Ah! We must be working with some kind of mastermind!
Cases of Absent Minded Staff
Human Error … Temperature Reading UV Readings Unit was sent through UV system upside down
Arc lamp performance-Data 55” (140 cm) bulb Irradiance mW/cm 2 Data collected 3/24/16 Band Left Center Right Highest Delta UVA 797 983 635 35.4% UVB 713 888 573 35.5% UVC 200 257 167 35.0% UVV 612 757 492 35.0% Energy Density mJ/cm 2 UVA 243 282 234 17.0% UVB 206 239 195 18.4% UVC 58 68 55 19.1% UVV 231 264 222 15.9% Bulb not installed correctly in UV system
Arc Lamp Performance-Graph Graphically display UV across width of bulb
Instrument Care • Radiometers work better when properly maintained
Optics & Sensor Care • Optics work better when properly maintained
UV Measurement Challenges Irradiance W/cm 2 Data Collected 3/24/16 Before: Data collected Band Before After Difference with contaminated UVA 1223 983 -19.6% optics UVB 1066 888 -16.7% After: Data collected UVC 277 257 -7.2% after cleaning UVV 889 757 -14.9% Energy Density J/cm 2 Band Before After Difference UVA 349 282 -19.2% UVB 284 239 -15.9% UVC 75 68 -9.33% UVV 309 264 -14.6%
UV Measurement Challenges • Two recommended methods: o Lint/Detergent free wipes or IPA with cotton swab • Advantages and disadvantages to each method • First do no harm • Avoid shirt sleeve, shop towel, etc. • Avoid ‘dry’ cleaning instrument
UV Measurement Challenges You Tube Video Link on EIT website
The Case of the Missing ID
How Old Are You? Hour Meter
Lamp Symptoms - Aging Mirroring Devitrification / Clouding Contaminated Airflow Blackening / Erosion
Aged Arc Lamp Middle End 440mW/cm 2 in the middle vs. 317 mW/cm 2 at the end How wide is your line compared to the product?
Variable: UV Energy Wavelength Mercury Gallium Iron Courtesy Heraeus Fusion UV
Variable: UV Energy Wavelength Ratio of different bands to identify bulb type
The Real World: Readings Profiling Radiometers • Trouble shoot two ‘identical’ production lines (Speed, bulb types) Line UVA 1 UVV Blue UVA Red UVV Line Speed Changed Bulb Type Changed UVV Line 2 UVA
UV Sources: Spectral Output With 600 hours of run time would you change this bulb? OLD NEW UVA Energy Density: 537 to 487 mJ/cm 2 UVA Irradiance: 309 to 290 mW/cm 2
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