by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
FLEXO Magazine : August 2010
Technologies & Techniques Possibly no other two items in the flexographic dictionary have been written or talked about as much as the anilox roll and the doctor blade— or, to be more precise, how to make the correct selection of anilox, engraving and volume, with the ideal doctor blade combination. A Brief History Flexographic historians believe that the original concept for flexography began with an American, J .A . Kingsley. He did actually receive a patent for his idea in 1853 but there does not appear to be any evidence that he actually did any printing using his ideas. It is known however, that Bonar Bibby and Baron in Liverpool, England, did apply for a patent in 1890, and in 1908 introduced what was a rotary web fed let- terpress machine that used low viscosity inks and soft printing plates. The aniline process, as this invention was originally known, used a felt-covered roll that transferred ink directly to the raised printing plate surface—the earliest two-roll system. But it became very obvious that a better solution was needed, as it generally either starved or flooded the plate most of the time. In fact, this first machine was commonly known as “ Bibby ’s folly.” But the seed was sown, and other manufactur- ers in both Europe and the U.S . quickly started to build their own improved versions of this rotary print process. This, in turn, led to the three-roll system, consisting of a rubber fountain roller, rubber metering roller and then the print cylinder. The first roll known as the fountain roller was partially sub- mersed in an ink pan. As it rotated, it would transfer ink onto the second rubber metering roll by means of allowing a small gap to be maintained between the two rolls. It was soon found that running a plain steel roll against the rubber roll allowed for more differential speeds between the two rolls, which aided the meter- ing process and reduced splashing and ink slinging. Looking for a better solution in 1938, Doug Tuttle and Joe Viner introduced the first mechanically engraved ink meter- ing anilox roll, based on the rotogravure engraved steel roll. Instead of an ink film splitting action, it led to a doctoring type of action. The anilox roll is, beyond doubt, the key element that has catapulted flexography from being a “John Bull” relief flexible plate process that was known to be a cheap and simple print process, and allowed it to become the fastest growing print process found in the world today. Things to Consider Before Making Anilox Selection • Ink system: solvent, water, UV. • Metering system: rubber roll, doctor blade, chamber system. • Substrate: absorbent or non-absorbent. • Speed of press. • Type of press and age. • Graphics to be printed: solid, solid and line, tints, process screen. • Line count to be used on printing plate, e .g . <65lpi, <85lpi, <100lpi, <133lpi, >150lpi. • Printing plate: rubber or photopolymer (yes, this is still relevant). • Operator skill level. Doctor Blade Materials • Generally, steel blades give the most consistent me- tering and print results. • Composite blades offer good resistance and longer life; most often used with abrasive inks. • Plastic blades have a lower coefficient of friction on ceramic rolls and are very popular in the corrugated industry. • Polyester and/or mylar blades tend to be the prefer- ence for most containment blades. Doctor blades, especially steel blades, should always be installed using protective gloves. Photo courtesy C-P Flexible Packaging. Anilox and Doctor Blade selection Guide By steve Wilkinson 86 FLeXO august 2010 www.flexography.org August2010_mech.indd 86 8/13/10 7:47 AM
Sustainable Summer 2010