ROLE OF ANILOX ROLLER IN FLEXO PRINTING
The
ceramic anilox roller is often referred to as the heart of the flexographic press. It is designed to deliver a precise and consistent amount of ink to the printing plate.
An anilox roll is a hard cylinder, usually constructed of a steel or aluminum core which is coated by an industrial ceramic whose surface contains millions of very fine dimples, known as cells. The choice of the correct anilox roller is of central importance for an optimal printing result. Depending on the printing type, we recommend different engravings and cell volumes. The choice of the correct anilox roller is of central importance for an optimal printing result.
A flexographic printer often faces problems due to the nonavailability of the correct anilox roller. The purpose of this article is to make an attempt to throw some light on this very important subject.
Anilox roll:
The flexo printing/coating process depends upon the precise controlled transfer of a liquid ink, varnish or coating. An anilox roll is simply a metering roll designed to consistently supply a uniform and measurable volume of ink onto the image carrier.Anilox roll is considered to be the heart of the flexographic press. Older methods of mechanically engraving cells in to the surface of a roll have been replaced, to a large extent, by the precise computer controlled laser engravings of ceramic coated steel rolls. In this process, millions of minute holes (cells) are drilled into the ceramic surface of the roll. Ink receptivity and releasing capabilities of the anilox roll is of higher importance and ink transfer capabilities of the plate are determined by the surface technology of plate, surface tension of plate & ink and plate to ink compatibility.
The central part of the press is the anilox roller, the ink metering system unique to this process that allows the correct amount of ink to be carried to the printing plate. On the surface of the anilox roll are etched the cells which act as ink carriers.
The latest
chrome anilox roller is laser engraved, with cell counts currently up to 500 cells/cm, from a steel roller and coated in fine ceramic. These laser engraved ceramic rolls could last up to 10 years, depending on the wear they are exposed to from contact with the doctor's blade. They provide an even, and consistent ink delivery in a controlled manner and provide narrow web flexo with a competitive edge in the leading packaging markets eg self-adhesive labels for wines. Once the anilox is ‘charged’ with ink, the excess is wiped off with a flexible steel doctor blade.
Besides the cell geometry, ink release capabilities of the cell are also affected by rheological properties of ink like; viscosity, surface tension, printing pressure between the plate cylinder and the impression cylinder, substrate properties, etc.
Anilox engraving angles:
Available engraving angles for anilox rolls are as follows; 90 degree angle, 45 degree angle, 30 degree angle and 60 degree angle.
In 60 degree anilox angle, the hexagonal cell offers 15 per cent more cells on the same area. Higher quantity of cells indicates a plus point concerning the ink transfer, as well as homogeneity.
Anilox sleeves:
Some of today's servo driven narrow web presses make use of anilox sleeves, which are much lighter than the standard solid anilox. The advantage is ease of handling and loading. On the narrow web side there is no difference in performance than with a conventional roll.
Ceramic anilox sleeves initially were profiled in a scenario of short-run environments where anilox changes are very common and required, but have shown their usefulness regardless of the frequency of changeover. Sleeves are easier to store and inventory.
The disadvantages of sleeves are their cost as well as the different care and handling that is required. Converters need to design special racks to store sleeves so that the chance of damage is minimized. In addition, sleeves cannot be cleaned in the same fashion as rolls, which may add more time and cost.
Mirror rollers are generally used in plastics, packaging, printing, steel and other industries. Since traditional hard chrome electroplating cannot fully meet the requirements of wear resistance and corrosion resistance, our matting rollers can perfectly solve these problems. Its hardness is increased from HRV800 with hard chrome layer to HRV1200, the corrosion resistance is greatly improved, and the service life is long.
Dr blade materials, on the other hand, are a little more complicated of a subject than that of their shape. There are five materials commonly used to create blades today and they are as follows: plastic (UHMW/UHMWPE), stainless steel, carbon steel, tool steel and graphite. While the steel blades have upsides and are favored by many within the industry, current trends and advancements in technology are heating up the playing field for plastic and graphite.