anilox
A method used to provide a measured amount of ink to a flexo printing plate, involving a hard cylinder whose surface is covered in tiny cells that capture the ink.
anilox: the metering drum that measures ink dose
An anilox is a hard steel or ceramic cylinder, usually 2 to 4 inches in diameter, whose surface is engraved with thousands of tiny cells or wells arranged in a regular grid. It sits between the ink fountain and the printing plate in flexographic presses, rotating to pick up ink and deliver a precisely controlled layer to the plate. The cylinder itself is extremely hard, typically hardened to 58-62 HRC, so that the cell pattern holds its shape under the constant pressure and abrasion of operation.
The cells are cut into the surface at a specific angle and depth, measured in lines per inch (LPI) and microns, which determine how much ink the anilox can carry. A 200 LPI anilox with 6 micron cells carries less ink than a 150 LPI anilox with 8 micron cells. The press operator selects the anilox based on the ink viscosity, the substrate, the plate line screen, and the desired ink film thickness on the finished print. Higher LPI counts produce finer detail and less ink transfer; lower LPI counts carry more ink for heavier coverage.
The engraving can be done by mechanical means, laser, or by electromechanical engraving (EDM). Each method produces subtly different cell geometries. Laser-engraved aniloxes, introduced widely in the 1980s, have largely replaced older mechanical and EDM methods because they produce consistent hexagonal cells and allow finer line counts. The choice of cell pattern, dome or chamber geometry, affects ink release and transfer efficiency to the plate.
An anilox surface degrades over time through wear and contamination. Dried ink, dust, and mineral deposits build up in the cells, reducing ink transfer and causing print defects. Aniloxes are cleaned chemically or mechanically between jobs, and eventually must be re-engraved or replaced. A damaged or clogged anilox is one of the most common causes of inconsistent ink coverage in flexo shops, so maintaining cell integrity is critical to press performance.
The term itself is obscure in origin, sometimes said to derive from "aniline" (a common ink base) plus the Greek word for "sharp," though this is not certain. The device was developed for flexographic printing, which needs precise ink metering because the printing is done on soft, compressible substrates like film and paperboard that cannot tolerate irregular ink laydown. Without an anilox, flexo inks would flood the plate unpredictably.