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FLEXO Magazine : June 2013
sure you have your Original Equipment Manufacturer’s doc- tor blade specifications. If you have a different OEM for your holders or chambers from your press manufacturer, be sure to use their specifications. Almost all doctor blade types come in widths ranging from 0.393 -in. (10mm) – 3 .5 -in. (90mm), and in thicknesses of .004- in.- . 012-in. The most common steel type used is white carbon, so typically we can start with that as our base. Next, let’s answer a few questions; 1. What type of ink do I use? Solvent, UV, or water based? if water, then you may need to look at using stainless steel 2. What kind of run lengths do I have on my schedule? 3. When do I want to change my doctor blades? (Once a day, twice a week or once a week) this will help deter- mine if you need to explore coated doctor blades for longer blade life 4. What is my anilox roll line screen count? This key infor- mation is what will help you determine the best direction for your doctor blade choice. If you look at the chart in Figure 5, you can see how we can categorize a few different blades by the anilox roll line screen. The higher the line screen the thinner the tip you will need to achieve a clean wipe of the anilox roller. This in turn will provide a clean ink transfer to the plate and a crisp, sharp printed image. Figure 5 Anilox Roller Line Screen Blade Tip Thickness 400ls 600ls 800ls 1000ls 1200ls . 075 Microns X . 095 Microns X . 125 Microns X . 150 Microns X X . 200 Microns X X . 250 Microns X Recommended Tip Style Straight Steel, Radius Tip Radius Tip Radius Tip, Lamella Bevel, Lamella Lamella With all these different doctor blade types to choose from, it can get to be overwhelming at some point, so why so many different doctor blades? If you look at Figure 6, this is a pic- ture of the tip of a doctor blade that comes into contact with the anilox roller. You can see the heavy wear patterns on the doctor blade. There is nothing wrong with this picture, it just shows how a low line screen count roller, like a 200, wears the doctor blade. Compare that to Figure 7 and the same doctor blade type ran on a 1,000 line screen. You can see the smooth wear pat- tern of the higher line screen roller. So, do you run the same doctor blade on both rollers? If you said yes, you are probably changing the lower line screen doctor blades two or three times more often because they will wear at a faster rate. As a general rule, anytime you change anilox rollers in a unit and go plus or minus 100 lpi, you should always change your doctor blade as well. Each anilox roller has its own unique pattern that it wears into a doctor blade and if not changed, the old wear lines can show up in the print. One more choice that will need to be made in chambered units is the setup type. Will you run a steel blade in the top and bottom, or a steel blade as the metering and a plastic/ Mylar blade as a containment blade? The main reason for Figure 6 Figure 7 www.flexography.org June 2013 FLEXO 79