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FLEXO Magazine : June 2013
Post Exposure Conditions for Tack-Free Plates By Randy Reynolds The post exposure step is very critical for producing tack-free AVantage photopolymer printing plates. The quantity of post exposure salt, lamp intensity, post exposure time, and a clean post exposure bath, plus the frequency of bath changes all will impact the quality of the finished plate. Recommendations are provided below for the proper salt concentration and time of post exposure. Concentration of Post-X Salt Bath: 3040/3048 unit 1lbperday 4460 unit 2.5 lbs per day 5280 unit 3.5 lbs per day Per day rates are detailed because the bath should be clean and clear for the best Post-X results. Once the bath turns cloudy it will filter the UV light during Post-X. Changing the Post-X bath daily is recommended. Mixing: Pre-dissolve the Post-X salt in water using a one or two gallon container then pour the solution into the Post-X bath water. The Post-X bath water level should be deep enough to completely cover the plate. Lamps: New lamps will range from 15-20 mW/cm2 when measured with a UV light meter. After a short “burn-in” period the intensity will level off to around 15-18 mW/cm2. Bulbs should be replaced once the intensity falls to 7 mW/cm2. Bulb life is dependent upon the hours they are used. Under typical production conditions bulbs should last one year. Exposure Times: The correct Post-X exposure time is dependent upon lamp intensity. The following is the recommended guideline: Average Lamp Intensity Reading Post-X Time 9.0 mW/cm2 or higher 15 minutes 8.0 - 9 .0 mW/cm2 20 minutes 7.0 - 8 .0 mW/cm2 25 minutes About the Author: Randy Reynolds is business manager for AVantageTM liquid photopolymers manufactured by Anderson & Vreeland, Inc. Reynolds is responsible for all external sales and support for AVantageTM liquid photopolymers, including corrugated, multi-wall bag and stamp resins. He is a seasoned veteran in the flexo industry with 16 years of sales and management experience. Exclusive to FLEXO TechTip#11 Ink & Its Delivery 4th Annual Anilox Roll/Doctor Blade Selection Guide Realistic & Relevant FTA’s 2013 Forum Targets Packaging’s Challenges, Celebrates itsSuccesses I mage courtesyofHarperCorp .june2013