Anilox roller specifications: mesh line or mesh volume

The author used a typical case to prove that the mesh volume is the best parameter to measure the performance of the anilox roller, which can ensure the anilox roller to achieve the best ink transfer performance and color reproducibility.

Fifteen years ago, when the author first contacted the anilox roller, as with many other people involved in flexographic printing, the first criterion for judging the anilox roller was the number of screen lines, followed by the mesh volume. For example, if an anilox roll has 800 meshes per inch and each mesh volume is 2 BCM (billions of cubic microns, ie one billion cubic microns), the specification of this anilox roll is expressed as 800 × 2 BCM. . why? Should the number of mesh lines of the anilox roller (i.e. the number of grid holes per inch of length) or the volume of the mesh (i.e. the amount of ink transferred to the plate and finally to the substrate) be used as the specification parameter in the printing?

The purpose of this paper is to break the inertial thinking of the past and help printers and suppliers accurately understand which element is more critical in flexo printing: Mesh lines or engraved mesh volumes?

Typical case in the printing shop

A frequently-printed color job is about to be reprinted, and the printer has prepared four anilox rollers accordingly. According to the previous printing experience, four 800 line/inch anilox rollers are required to print the four colors of yellow, yellow, green and black. Just in the workshop, there are six 800-line/inch anilox rollers, and the printer randomly selects four of them for installation and pressurization. Under the correct printing pressure, the printer measured the density of the solid ink using a densitometer.

However, the results showed that the same substrate, ink, plate, and sticker tape failed to achieve the same color as the previous print. It is not correct that the anilox roller used 800 lines/inch as in the previous printing. Manufacturers clearly marked on the edges of the anilox roller are indeed 800 line/inch anilox rollers and the number of lines cannot be changed unless the anilox roller is re-engraved. Why is the color inconsistent? Why did you waste paper, ink, and time or get different results?

According to the data provided by the anilox roller supplier, the same volume is selected, and the change of the color of the printed product will be within the allowable range, that is, it is consistent. However, due to cleaning, damage, and wear, over time, the color of prints may also be inconsistent. Therefore, selecting four of the six anilox rollers to print to the same color as the previous one is not a good method based on the number of screen lines of the anilox roller.

Because the six anilox rolls change from half year to four years. The longer the time, the more severe the damage of the anilox roller due to improper off-line cleaning operations will be. The typical failure of some anilox rollers is caused by the improper use of the doctor blade, while the slight blockage of the majority of existing anilox rollers is due to poor on-line cleaning and lack of inspection prior to use. Regular check of the anilox roller, effective cleaning, correct inspection and judgment of the anilox roller in the past work, can minimize waste. By identifying the serial number and the mesh volume of the anilox roller, waste can be minimized or even eliminated. Learn which anilox rollers have a higher volume, which helps the printer to choose the application accordingly. Based on these volume parameters, the printer can choose the best anilox roller to print black ink, and the worst anilox roller to print yellow ink.

It is clear that the key to this problem is the mesh volume of the anilox roll, not the number of mesh lines, because the number of mesh lines is the same. Actually, this problem can be avoided through different ways of communication, and we have spent a lot of time and materials in identifying the causes of this potential problem.

About printing color density

The color density comes from the ink pigments formulated by the ink supplier. Pigments provide a color carrier, and additives provide various properties required after printing, such as scratch resistance, abrasion resistance, fade resistance, or moisture resistance. The ink system is formulated according to the density of the anilox roller reaching the density of the ink in the field or the minimum volume requirement for forming the thinnest ink film. The anilox roll supplier provides the mesh volume parameters necessary for ink production. This parameter ensures accurate and consistent ink color transfer for optimal performance and color reproducibility.

About mesh lines

The number of mesh lines refers to the number of mesh holes per inch. These mesh holes are engraved at an angle to the axis of the anilox roller, typically 30°, 45°, or 60°. Once the engraving is completed, the number of meshes is fixed. Anilox roller with low mesh lines, high mesh volume, suitable for field version and coating. An anilox roller with a mesh volume of 8.0 BCM engraves 165 to 300 holes per inch. Anilox rollers with a high number of mesh lines are suitable for smaller mesh volumes. 2.0 BCM anilox roll for overprinting and hybrid printing, the number of engraved meshes ranges from 700 to 1200 per inch. In order to achieve accurate mesh volume and good ink transmission, the mesh wall in the mesh needs to be thin and smooth, and the engraving depth should not be too shallow or too deep. According to historical experience, the depth of the shade is mainly applied to the glazing, so that it is easier to clean it later.

In order to achieve the same mesh volume under different mesh lines, the depth of the mesh with a higher mesh line depth is correspondingly deeper. An ink roller with a mesh of the same mesh height can form a smoother ink film. An increase of 200 meshes per inch, corresponding to an increase of 40,000 meshes per square inch, provides more support for ink delivery. Although the mesh line number is a conventional specification parameter, the mesh line number corresponds to the mesh volume, and it has little or no effect on the print quality.

About mesh volume

Mesh volume represents the ink storage capacity per square inch of sculpted surface in units of billion cubic microns (BCM). The volume of the mesh is large, and the solid ink density delivered is also larger, or the color is thicker and the coating thickness is greater. The mesh volume is small, the ink film thickness is thin, the printing quality is high, and the printing efficiency is high. Because of wear, clogging, and cleaning, the mesh volume will change over time. The mesh is dirty or clogged. This temporary failure can be corrected by restoring the original volume and color. However, wear and tear are irreversible and permanent damages because of the poorer color than the original volume.

According to market experience, according to the different substrates, the mesh volume also has a corresponding recommended range. Field full version/glazing: 5.0 BCM or more; mixed version printing: 2.0 to 4.0 BCM; color overprinting: 1.3 to 3.0 BCM. If the mesh volume alone is used as a reference, then the effect of judging the printing quality of the anilox roll becomes clear and easy to understand, and it will not cause problems due to the influence of the mesh line number on the print quality. Especially today, anilox roller manufacturers gradually express the engraving effect in combination with the mesh volume and the number of mesh lines, and this effect can be changed with the available laser technology.

Assume that the anilox roll only considers the mesh volume in the following applications—color overprint: 1.5 BCM; mixed print: 2.2 BCM; line version/field version: 3.5 BCM. So, how can managers, purchasers, testers, and printers rely more on mesh volumes to manage and identify applications more easily?

Nowadays, flexo printing continues to grow, and existing skilled printers are limited. Printers rely on internal staff training and mechanically seeking help from job seekers. Is there a better way to eliminate variable factors in the printing process so that more experienced operators and printers are in the same level?

For example, in the process of color printing, there is only a 1.5 BCM anilox roller, there is no other choice, there is no opportunity to install the wrong anilox roller, or to sacrifice the printing quality, use unqualified materials and repeatedly run and waste time. So what is the impact on the performance and type of anilox roller? Users say their anilox roller is 800s. Do they refer to the 800s refers to the traditional 2.0 BCM mesh volume anilox roller, or to an improved 3.5 BCM mesh volume anilox roller? As an ink supplier, we need to know this mesh volume in order to provide the correct amount of ink and to ensure accurate color reproduction. The number of mesh lines represents too little. It is just a means by which the anilox roller makers achieve their purpose. So, which of the 500 lines, 700 lines, 1000 lines, and 1500 lines is better? why? Engraving under the same volume, the solid ink density and dot gain of printing are relatively consistent. According to most of the published chart data, these four types of mesh lines can engrave a 2.5 BCM mesh volume. 500 of them are shallow, but this is only the result shown on the chart.

The same mesh volume = the same ink film thickness; the same ink film thickness = the same solid density; the same ink film thickness = the same dot gain value.

What is the number of anilox rollers supported by the traditional concept printing plate? In the past, the ratio of the number of screen lines of the anilox roller to the number of screen printing screen lines was once 4:1, and now the ratio has increased to 6:1. The ratio of the size of the minimum dot of the printing plate to the size of the opening carved into the hole is a big problem.

As flexo printing has entered the traditional high-quality printing field, almost all flexographic components require higher-quality printing capabilities, printing efficiency has increased, and flexo printing has also entered the previously inaccessible market.

Related improvements involved

Today's printing equipment, materials, and post-press processing equipment have few similarities in appearance and performance compared to ten years ago. The printing plate has been changed from a rubber plate to a resin plate, supporting dot reproduction below 1%, resolution of 200 dots per inch or more, and the production time has also been shortened. The original sensitive PH system has been developed into a water-based ink system with almost no maintenance costs. The UV ink can better maintain the ink color, and the viscosity has dropped to the level of water-based inks. Printing tools, squeegees, adhesive tapes, web inspection systems, and every other printed component have all been improved, helping to increase the capabilities and growth of the flexographic industry.

With the improvement of hardware equipment and the improvement of flexo printing technology, new ideas and opinions have also been encouraged and supported so as to continuously improve this dynamic industry. Therefore, after years of technological changes, many new ideas and new ideas have emerged regarding the relationship between anilox rollers, inks, printing plates and printing quality. We likened the anilox roller to the “heart” of the flexo press. It was related to the mesh volume and ink film thickness, not to the number of mesh lines.