When replacing an anilox roller, many printing companies simply order a new roller with the same LPI and BCM specifications as the existing one. However, once the new roller is installed, the printed colour may appear darker or lighter, while solid coverage, dot reproduction or white ink opacity may also change.

This does not necessarily mean that the specifications of the new anilox roller are incorrect.

This does not necessarily mean that the specifications of the new anilox roller are incorrect.

The real reason is that LPI and BCM are only two basic anilox specifications. They do not fully describe the cell geometry, actual volume or ink-release performance of the roller.

Even when two anilox rollers have the same nominal LPI and BCM, differences in cell opening, depth, wall thickness, engraving geometry and manufacturing tolerances can produce noticeably different print results.

Why Are LPI and BCM Not Enough?

LPI, or lines per inch, indicates the number of cells within one inch of the roller surface. In Europe, anilox line count is also commonly expressed in lines per centimetre, or L/cm.

BCM refers to the theoretical cell volume per square inch. European specifications commonly use cm³/m².

These two values are important, but they do not tell you:

• the size of the cell opening;

• the depth of the cells;

• the thickness of the cell walls;

• the engraving geometry;

• how efficiently the ink is released;

• whether the volume is consistent across the entire roller.

For this reason, comparing only LPI and BCM is not enough when selecting or reproducing an anilox roller.

1. The Same LPI Can Have Different Cell Openings and Wall Thicknesses

The same LPI means that the number of cells is similar, but it does not mean that every cell has the same opening size.

For example, two 800 LPI anilox rollers may have very different structures. One may use larger cell openings with thinner walls, while the other may have smaller openings with thicker walls.

These differences can directly affect:

• how easily ink enters the cells;

• the effective ink-carrying area;

• ink-release efficiency;

• solid coverage and dot reproduction.

In high-resolution label and flexible packaging printing, even small variations in cell opening and wall structure can influence colour density and dot gain.

2. The Same BCM Can Have Different Cell Depths and Ink-Release Characteristics

BCM indicates how much ink the cells can theoretically hold. It does not mean that all of this ink will be transferred efficiently to the printing plate.

The same volume can be achieved with different cell geometries, such as:

• wider and shallower cells;

• narrower and deeper cells.

Although both structures may have the same nominal BCM, their ink-release performance can be different.

Deeper cells may provide the required theoretical volume, but more ink can remain at the bottom of the cell. This is especially important when printing with high-viscosity inks, opaque white inks, coatings or at high press speeds.

An anilox roller should therefore be evaluated not only by its volume, but also by its cell opening, depth and depth-to-opening ratio.

3. Different Engraving Geometries Transfer Ink Differently

Not all anilox rollers use the same cell design. In addition to conventional hexagonal cells, other options may include elongated cells, open-channel engravings and geometries developed for specific inks or coating applications.

Different engraving structures can affect:

• ink flow within the cells;

• ink behaviour after doctoring;

• ink-release speed;

• solid-print uniformity;

• white ink opacity;

• stability at higher press speeds.

As a result, two anilox rollers with identical LPI and BCM values may still produce different print results if their engraving geometries are different.

CMYK process printing, solid spot colours, opaque white and coating applications do not all require the same cell structure. The engraving should be selected according to the actual printing application, rather than by copying two specification values alone.

4. Actual Volume and Cross-Roller Consistency May Vary

The BCM value marked on an anilox roller is normally a target or nominal specification. The actual volume also depends on several manufacturing factors, including:

• ceramic coating quality;

• laser engraving stability;

• surface grinding and polishing;

• cell-depth consistency;

• measurement equipment and inspection methods;

• the manufacturer’s volume tolerance.

For high-quality flexographic printing, the average cell volume is not the only important factor. The volume should also remain consistent from the operator side to the centre and drive side of the roller.

Poor cross-roller consistency can result in:

• colour variation across the web;

• uneven solid coverage;

• local density fluctuations;

• difficulty maintaining brand-colour accuracy.

When purchasing an anilox roller, it is therefore important to ask whether the supplier provides multi-point inspection data rather than only one average volume value.

5. The Actual Condition of the Old Anilox Roller May Have Changed

This is one of the most commonly overlooked issues when replacing an anilox roller.

The specifications marked on an old roller normally describe its original condition when it was manufactured. After years of use, the cells may have worn and the effective volume may no longer match the original specification.

For example, an old roller may originally have been specified at 4.0 BCM. After extended use, its effective ink-carrying volume may be lower. If a new roller is manufactured to the original 4.0 BCM specification, it may transfer more ink than the current old roller, resulting in a darker printed colour.

For this reason, an old anilox roller should not be reproduced based only on the engraved or labelled specifications.

For colour-critical applications, it is advisable to inspect:

• actual cell volume;

• cell opening;

• cell depth;

• cell-wall condition;

• volume consistency across the roller.

Where inspection data is unavailable, the supplier should at least be provided with current print samples and the required colour target.

How Can You Determine Whether the Anilox Roller Is Causing the Difference?

When a new and an old anilox roller produce different results, the printing conditions should first be kept as consistent as possible.

This includes using:

• the same press and printing unit;

• the same printing plate;

• the same batch of ink;

• the same ink viscosity and temperature;

• the same doctor blade pressure;

• the same press speed;

• the same batch of substrate.

Once these variables are controlled, compare solid ink density, Lab values, white ink opacity and colour consistency across the web.

This makes it easier to determine whether the difference is caused by the anilox roller or by another part of the printing process.

What Information Should You Provide When Ordering a Replacement Anilox Roller?

To obtain an anilox roller that more closely matches the required print performance, provide the supplier with:

• press manufacturer and model;

• roller dimensions or technical drawing;

• current LPI or L/cm;

• current BCM or cm³/m²;

• ink type;

• substrate;

• press speed;

• printing application, such as CMYK, solid colour, opaque white or coating;

• current print sample or target colour;

• the specific printing problem that needs to be solved.

For demanding replacement projects, an inspection report of the existing roller is also recommended.

This allows the supplier to evaluate the line count, cell volume and engraving geometry according to the actual printing target, rather than simply copying the specifications shown on the old roller.

Conclusion

The same LPI and BCM do not always mean the same anilox performance.

Print results are also influenced by cell opening, depth, wall thickness, engraving geometry, actual volume tolerance, cross-roller consistency and the current condition of the existing roller.

When purchasing a replacement anilox roller, the objective should not be limited to reproducing the original numbers. The real goal is to reproduce stable ink transfer and the required colour performance.

Providing the press model, roller dimensions, ink type, substrate, current specifications and print samples will significantly improve the accuracy of the replacement anilox recommendation.