Fluid Movements
Suppliers trace popular and pending doctor blade usage trends.
By Susan Friedman
The smooth, even business of ink metering isn't without its grayer areas. Yes, flexo printers have long been heavily loyal to doctor blades, particularly chambered systems...but metering roll applications still remain. And yes, gravure printers still favor trailing blade configurations...but reverse angle's potential hasn't faded away. Here, suppliers explore the sometimes uneven ink metering terrain.
Flexo: chamber-made?
For many flexo printers, the decision to use doctor blades instead of a two-roll metering system has been pretty, well, cut and dry.
"There are not many scenarios where a two roll system will out-perform a doctor blade system," contends Matt Burie, account executive, at Printco Industries. Burie emphasizes doctor blades' strength lies in their basic function—metering excess fluid off the unengraved areas of the anilox roll or gravure cylinder. "By allowing the anilox or gravure roll to transfer as much fluid as it has been designed to carry instead of flooding the printing plates, sharper, cleaner print is achieved that is essential for process work," he explains.
Tom Allison, president, Allison Systems, seconds the "process work advantage" line of thinking. "Two-roll inking is mostly extinct in flexo due to the need to produce high-end graphics on packaging, which translates into the need for good control at high and especially low color densities," he comments. "To do this, the doctor blade and blade system must prevent dot gain due to surface ink left on the anilox roll. Regardless of how fine the anilox screen and how small and well controlled the cell volume, the surface ink left by a two-roll system is usually not acceptable."
Perhaps the two-roll metering system has become an endangered species of sorts. But don't put it on package printing's extinct list just yet.
"Flexo printers running chrome-surfaced anilox rolls will typically print with a two roll system, as the doctor blade wears the chrome anilox very rapidly," points out Anthony Foley, national marketing manager, Edward Graphics.
