Trade.Information

Product Name: Eliminating Common Problems In Platemaking

Product Description

Some ways to avoid (or at least minimize) air pockets, troublesome pinholes and static electricity For years, pinholes, air pockets and static electricity problems have plagued flexographic platemakers who work with film and polymer plates. Many of the problems can be avoided (or minimized) with a better understanding of their causes. There also are a number of products that address these problems. In flexo platemaking operations, static electricity attracts dust and dirt particles to the Krene, resulting in troublesome pinholes in negatives and plates. The cause of static is the charges that develop from friction between non-conducting surfaces when they are rubbed together. For example, the cleaning of the Krene with a wiper and alcohol (film cleaner) is a friction source that attracts dust and airborne particles. Static-producing friction also can be described as contact and separation, such as that which occurs when simply rolling and unrolling the Krene sheet. Static charges develop and can build up over several days, reaching as high as 50,000 volts from these unsuspected sources. Myths persist when it comes to humidity-related static problems. Many experienced printers believe that static electricity vanishes with high humidity in the summer months, and that low humidity in the winter can be overcome by using a moisture spray. The fact is, however, that high humidity doesn't mean static electricity isn't present. It's simply that the voltage generated is below the threshold of human feeling, as your fingertips don't feel the discharge of electricity. You still have to neutralize the charge to ensure your equipment and materials are clean. Applying an anti static, microscopic protective coating to the Krene will neutralize the static charge that attracts dust and particles. This anti static treatment creates a slick microscopic barrier that prevents dust particles from adhering to the Krene. It also eliminates friction, thus reducing static build-up. When evaluating platemaking cleaning methods, the choice of wiping fabric also should be taken into consideration to effectively minimize static electricity and pinhole problems. The long-standing practice of cleaning with cheesecloth is suspect; the fabric sheds fibers badly. It is better to use a glass cleaner and soft, low-lint wipe to remove dirt from the vacuum bed. A special magnetic wiping cloth can be used dry, by itself, to remove dirt from the Krene, film or plate surface. By means of inherently charged fibers, this cloth attracts and holds dirt like a magnet. It also minimizes friction and reduces static build-up. REMOVING AIR POCKETS The ordinary method of eliminating air pockets between plate mineral, film and the Krene by using your hand or a squeegee also creates problems. Surface friction is generated by this method, as is static electricity that attracts dust. Instead, a specially weighted film draw-down wand can be used to remove trapped air pockets. When treated with an anti static protective coating solution, the wand smoothes out trapped air pockets while removing dust and dirt particles. It ensures cleaner contacting and reduced static electricity build-up. In addition, vacuum draw down time can be reduced by as much as 50%. The Label Group Graphic Resource Division of Engraph, a commercial platemaker, experienced serious dust problems until the company began using anti static protective coating solution, magnetic wiping fabric and film draw-down wand. "My most recent month I made 1200 plates, with only two plates rejected because of dust" says Bryan Davis, who works in the plate department. To prevent pinholes in negative and flexo plates, air purification and static neutralization considerations are necessary. Air must be filtered to remove sold airborne contaminants. Standard fiberglass filters on heating, ventilation and air conditionin g systems (HVAC) allow small particles to pass, so finer filters for incoming air are recommended. If possible, filtered air should be drawn in from a system separate from the HVAC system and maintained at a positive air pressure in the room. This prevents particles from streaming into the room when doors are opened. Conventional removal of airborne particles by air purifying units utilizing a high-turbulence fan with filters or with electronic air cleaning cells is sufficient for most industries. However, special considerations are required for the graphic arts industry. Gentle airflow is important to avoid excess turbulence that can stir up settled dust from ceilings, walls, equipment surfaces and floors. These particles could be scattered to many work surfaces before they reach the capture point at the air-cleaning unit itself. Although this type of conventional air cleaner would decrease the actual particle count in the room, it is not an effective solution. Air ionization equipment installed in film handling operations is recommended. Positioning an air ionization unit within two or three feet of platemaking equipment helps neutralize static when handling both film and polymer plates. A gentle, adjustable flow of ionized air removes contaminates while neutralizing static charges from the job material surfaces. While ionization improves conditions dramatically, particles still can settle through gravity or be transferred to job materials through contact with dirty tabletops or work stations. Additional measures to minimize particle generation within the platemaking area can be taken. Paint or coat walls and floors with a sealant (or use suitable construction material). Do not use acoustical ceiling tile. Remove carpets; although they initially trap particles, carpets release them into the air when they are walked on. Strictly enforce regular clean up procedures. Prepress personnel should refresh their understating of static electricity problems and stay up-to-date with new systems that prevent friction and static build-up. A few moments of preventative maintenance will keep quality levels high, interdepartmental arguments low, and production anxiety levels at a manageable rate.