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FLEXO Magazine : October 2010
Technologies & Techniques the team’s goals, concerns, and possibly current problem areas. Never assume you don’t currently have problem areas! Combine your team of suppliers and production personnel to hammer out goals and concerns like the following: • Possible Goals: Color consistency Better ink mileage Predictability and repeatability Less plate separations, combo printing, screens and solids on same plate Reduction in set up times; less overall downtime Reduced number of anilox rolls in inventory • Possible Concerns You may currently have multiple ink systems Possible difficulty running combination solid/screen - Screens, vignettes, or fine type printing dirty - Over impression of screens to get good solids - Not enough stations to separate Banded Roll TRial Instead of dealing in generalities that often describe a top- view of standardization, I have chosen to shed light directly on the critical mechanics of the methods your team can use and should document to achieve your goals and address your printing concerns. We will start with the banded anilox. A banded anilox roll is like any other anilox with the exception it has the added test features of varied engravings across the face length. The main purpose of running a banded roll trial is to assist the printer when it comes to selecting the engraving type, cpi (cells per inch), and ink volume requirements for their specific process. How does our team design a banded anilox? Start by determining the roll layout. Roll layouts may vary due to the differences in ink systems and types as well as the substrates you are running. Examples of common layouts requested for water-based ink systems: 900cpi/3.0bcm, 600cpi/4.5bcm, 700cpi/4.0bcm, 800cpi/3.5bcm, 900cpi/3.0bcm. For solvent based ink systems: 800cpi/3.5bcm, 700cpi/4.0bcm, 600cpi/4.5bcm, 500cpi/5.0bcm, 400cpi/5.5bcm, 800cpi/3.5bcm. See Figure 1 and 2. Printers sometimes question the need for the outside bands having similar specs. They are referred to as control bands. The control bands are used to confirm that you have even impression across the web. addiTional ComponenTs We certainly cannot stop at the anilox for standardization. What other considerations should we make for testing? • Printing Plates. Plate types may vary in their ability to transfer ink or hold targeted dot gain. You may have reasons to trial multiple line screens. For example, you might currently run 133lpi but have a customer requesting 150 to 175lpi. Determine the print targets or test elements. For example: tonal scale, positive and reverse type, fonts, etc. • Mounting tapes. Different durometer tapes can affect both dot gain as well as solid ink density. • Ink supplier/system. Know if there are options to increase strength if needed. Remember: more pigment means fewer characteristics (rub, scuff, water resis- tance). Ink suppliers who designed a system, have an idea of volume requirements and starting point. Ink choice. Color, pigment, strength, chromo shift with strength (over tone/under tone), overprints/ability to trap. The ink’s ability to trap may affect print order. Running base colors. I am personally a big fan of this. Reflex and green are typically the hardest colors to hit. If you are able to achieve desired color strength with base colors, your formulas can be adjusted accord- ingly. Formulation adjustments can be time consuming, but can add up to huge savings when done prior to the inks being sent out to press. • Substrates. Start by testing the substrates that make up the majority of your product mix. Are you mostly using FiguRe 3. A test sheet. FiguRe 4. good dot structure (left) versus poor dot structure. www.flexography.org october 2010 FLeXO 53 FLX_Oct10_mech.indd 53 10/15/10 12:32 AM
Sustainable Fall 2010