BCM – Cell Geometry Cell angle in Anilox Roller Calculation
What is an Anilox Roll?
An anilox roll is a precision-engineered metering roller used in flexographic printing to transfer a controlled and repeatable volume of ink, coating, adhesive, varnish, or other liquid from the ink supply to the printing plate.
It is one of the most critical components of the flexographic printing process because it precisely regulates the amount of fluid delivered to the plate, directly influencing print density, color consistency, image sharpness, and overall print quality.
The operating principle of an anilox roll is both simple and highly precise. Its surface is laser-engraved with millions of microscopic cells, each designed to hold a specific volume of liquid. As the roll rotates through the ink fountain or receives ink from a chambered doctor blade system, these engraved cells are filled with ink.
A doctor blade then removes excess ink from the roll’s surface, ensuring that ink remains only within the engraved cells. When the anilox roll contacts the flexographic printing plate, the ink contained in the cells is transferred to the raised image areas of the plate, which subsequently print onto the substrate.
The amount of ink transferred is determined by three primary engraving parameters:
Cell Count (Line Screen/LPI): The number of engraved cell rows per linear inch. Higher cell counts produce finer ink films for high-resolution graphics, while lower cell counts deliver larger ink volumes for solids and coatings.
Cell Geometry: The shape and orientation (typically 60°, 45°, or 30° engraving angles) of the engraved cells, which influence ink release efficiency, cleaning performance, and print stability.
Cell Depth: The depth of each engraved cell, which determines its individual ink-holding capacity.
These three parameters combine to determine the total ink volume carried by the anilox roll. This ink-carrying capacity is expressed as BCM (Billion Cubic Microns per Square Inch), the industry-standard measurement of engraved cell volume.
Selecting the correct combination of cell count, geometry, and BCM is essential for achieving consistent ink transfer, accurate color reproduction, optimum print quality, and maximum press efficiency.
Impact of Anilox Cell Angles
The engraving angle determines how the cells are arranged across the anilox surface and directly affects doctor blade wiping efficiency, ink release characteristics, and the consistency of ink transfer.
60° Hexagonal Cell
The 60° hexagonal engraving is the industry standard for most flexographic process printing applications. Its hexagonal pattern allows cells to be packed closely together, providing approximately 15% more cells per unit area than traditional diamond engravings. The thin cell walls promote excellent ink release, producing a uniform, geometrically neutral ink film with outstanding print consistency. This engraving is ideal for high-quality process printing, fine screens, and extended gamut (ECG) applications.
30° Channel Cell
The 30° channel engraving features elongated cells connected by vertical channels that improve ink flow and evacuation. This design enhances ink transfer while minimizing ink misting, making it particularly suitable for UV flexographic printing, high-speed presses, and high-opacity white inks on films. The channel structure also improves doctor blade cleaning and reduces the risk of cell plugging.
45° Diamond (Quad) Cell
The 45° diamond (quad) engraving is an older mechanical engraving pattern that remains suitable for heavy coatings, varnishes, and basic corrugated printing. Its thicker cell walls provide excellent structural strength and wear resistance. However, because it contains approximately 15% fewer cells per unit area than a 60° hexagonal engraving, ink transfer is generally less uniform. In process printing, this pattern may also increase the likelihood of ink spitting or interference with the plate screen angles.
70°–75° Longcell
The 70° to 75° longcell engraving consists of elongated cells with nearly vertical sidewalls that increase ink carrying capacity while maintaining controlled ink release. These engravings are particularly effective for heavy solids, combination plates, and paper and paperboard substrates, where higher ink densities and improved solid coverage are required. The longcell design promotes excellent ink transfer while maintaining print stability during long production runs.
Key Anilox Calculation Formulas
To relate an anilox roller’s line screen (LPI), cell geometry, and ink volume, the following formulas are commonly used.
- Cells per Square Inch
The total number of engraved cells per square inch depends on the engraving angle.
For 45° cell patterns:
Cells/in² = LPI × LPI
For 60° hexagonal and 30° channel engravings:
Cells/in² = LPI × LPI × 1.15
The 1.15 factor accounts for the increased packing density of hexagonal cell arrangements compared with a square (45°) pattern.
- Ink Volume Conversion
To convert the engraved cell volume from BCM (Billion Cubic Microns per Square Inch) to the international metric unit cm³/m², use:
Volume (cm³/m²) = Volume (BCM) × 1.55
Conversely:
Volume (BCM) = Volume (cm³/m²) ÷ 1.55
Example:
5.0 BCM × 1.55 = 7.75 cm³/m²
8.0 cm³/m² ÷ 1.55 = 5.16 BCM
Notes
LPI (Lines Per Inch) represents the number of engraved cell rows per linear inch.
Cells per square inch indicate the engraving density of the anilox roller.
BCM is the standard unit used primarily in North America, while cm³/m² is the internationally accepted metric unit for specifying anilox cell volume.
These formulas are widely used for estimating engraving density and converting ink-carrying volume between imperial and metric systems.
Actual ink transfer efficiency also depends on factors such as cell geometry, cell depth, opening size, engraving technology, doctor blade condition, ink rheology, and press operating parameters.
Why the Anilox Roll Matters More Than Any Other Press Component
Press operators often focus their troubleshooting efforts on printing plates, substrates, or ink formulations when the actual root cause lies with the anilox roll. The reason is straightforward: the anilox roll precisely controls the volume of ink transferred to the printing plate, thereby determining the ink film thickness applied to every square inch of the printed image.
Even a relatively small reduction in cell volume can have a significant impact on print quality. For example, if an anilox roll has lost approximately 15% of its ink-carrying volume due to cell plugging, contamination, or normal wear—a condition commonly found in rolls that have not been inspected or audited for more than a year—the press will be unable to achieve the required print density and color strength.
No amount of press adjustment, increased ink viscosity, or plate optimization can fully compensate for the reduced ink transfer caused by a worn or contaminated anilox roll.
For this reason, regular anilox inspection and volume auditing should not be viewed as routine maintenance alone. They are essential process control measures that ensure consistent ink transfer, accurate color reproduction, repeatable print quality, and predictable press performance.
A well-maintained anilox roll forms the foundation of stable flexographic printing, making it one of the most critical components in the entire printing process.
BCM Ranges by Application
The following ranges are widely used as practical industry guidelines. Final anilox selection should always be verified through press fingerprinting and optimized based on the ink system, printing plate, substrate, press configuration, and required print quality.
| Application | Typical BCM Range | Typical Line Count (LPI/CPI) | Typical Characteristics |
| Process Color (CMYK) – Fine Graphics | 1.5–4 BCM | 800–1,500 LPI | Produces thin, controlled ink films for high-resolution images, fine text, and smooth vignettes while minimizing dot gain. |
| Combination Printing (Solids + Graphics) | 3–8 BCM | 400–800 LPI | A balanced specification suitable for jobs containing both solid areas and halftones, offering good ink laydown and image detail. |
| Heavy Solid Coverage (Corrugated) | 8–20 BCM | 200–400 LPI | Delivers higher ink volumes required for kraft liners, corrugated board, and large solid areas where coverage is more critical than fine detail. |
| Opaque White Ink / Flood Coating | 15–40 BCM | 65–200 LPI | Provides the large ink volumes needed for high-opacity whites, flood coats, and specialty applications requiring maximum coverage. |
| Coatings, Varnishes & Adhesives | Application-Specific | Application-Specific | Selected according to coating weight, adhesive transfer requirements, viscosity, solids content, and desired film thickness. |
Important Selection Considerations
Anilox specifications should never be selected based on BCM alone.
The following factors must also be considered:
- Cell geometry (60° hexagonal, elongated, channel, etc.)
- Cell depth-to-opening ratio, which influences ink release efficiency
- Laser engraving technology and ceramic surface quality
- Ink type (water-based, solvent-based, UV, UV-LED, EB)
- Ink viscosity and rheology
- Printing plate technology (digital, flat-top dot, surface screening)
- Substrate characteristics (film, paper, labels, corrugated board, foil)
- Printing speed and press configuration
- Required print density, opacity, and color consistency
Engineering Perspective
Increasing BCM increases the volume of ink transferred to the printing plate. However, higher BCM does not always improve print quality.
Excessive ink transfer can lead to:
- Increased dot gain
- Poor fine-detail reproduction
- Slower drying or curing
- Mottling and dirty print appearance
- Ink spitting and reduced press stability
Conversely, selecting a BCM that is too low may result in:
- Low print density
- Weak solids
- Poor opacity (especially with white inks)
- Inconsistent color reproduction
For this reason, experienced flexographic printers select an anilox specification by balancing BCM, line count, cell geometry, and ink release characteristics to achieve the required print quality with maximum consistency and production efficiency.
Advantages of Optimized Anilox Roll and Ink Transfer
An optimized anilox roll and ink transfer system is fundamental to achieving high-quality, efficient, and repeatable flexographic printing. Proper selection of anilox specifications, combined with an effective doctor blade system, delivers measurable improvements in print performance, productivity, and operating costs.
Precise Ink Metering
The anilox roll meters a precise and repeatable volume of ink to the printing plate, allowing accurate control of ink film thickness. This consistency is essential for maintaining stable print density and achieving predictable color reproduction. Well-controlled ink transfer can help maintain color accuracy within commercial tolerances, typically with Delta E values below 2.0.
Superior Print Quality
Consistent ink transfer produces sharper images, cleaner fine text, smoother gradients, and more uniform solid areas. Optimized anilox selection also minimizes common print defects such as mottling, dirty print, excessive dot gain, and inconsistent ink laydown, resulting in higher overall print quality.
Improved Production Efficiency
Modern enclosed chamber doctor blade systems significantly improve press efficiency by reducing ink waste, minimizing solvent evaporation, and shortening cleaning cycles. Compared with traditional open ink pan systems, enclosed chambers can reduce solvent evaporation by as much as 70%, while maintaining stable ink viscosity throughout long production runs.
SUM UP :
- Consistent ink transfer for uniform print density and color.
- Improved print quality with sharper images and cleaner details.
- Reduced ink consumption by delivering the correct ink volume.
- Better color consistency throughout the production run.
- Reduced printing defects such as dirty print, pinholing, and uneven solids.
- Higher production efficiency with less waste and fewer press adjustments.
- Improved repeatability from job to job.
- Longer anilox roll life through proper selection and maintenance.