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What is Flexographic Printing? Definition and Essential Principles

Have you ever wondered how the colorful packaging of your favorite snacks, bread bags, or labels on beverage bottles are printed? Most likely, the answer is: with flexographic printing! But what exactly is this technology, and how does it work?

Flexography, or flexo printing as it is often abbreviated, is a modern and versatile direct printing method. What does “direct” mean? Simply that the ink is transferred directly from the printing plate (the form containing the image) to the material you want to print on (the substrate). It is considered a relief printing technique, which means that the areas on the plate that are to transfer color are raised, much like a rubber stamp you use on paper. Furthermore, flexographic printing presses typically operate in a rotary manner, i.e., with cylinders that rotate at high speed, making this technology ideal for roll-to-roll printing on large volumes of material.

The name itself, “flexography,” gives us a fundamental clue about its operation. This term, officially adopted in the 1950s, derives from the word “flexible” and primarily refers to two key aspects:

The printing plates: These forms, technically called clichés, are made from flexible materials. Originally, rubber was used, while today modern photopolymer materials, which are also elastic, are predominantly employed. This flexibility allows them to adapt to a wide range of surfaces.
The printing substrates: Often, the materials on which flexographic printing is performed are also flexible, such as thin plastic films, paper, aluminium, or labels.

Another distinctive principle of flexographic printing is the so-called “kiss printing.” This term describes the very light and controlled pressure exerted by the inked plate on the printing substrate. It’s a delicate “touch,” sufficient to transfer the ink cleanly and precisely from the raised part of the cliché, without excessively crushing the flexible plate or deforming the underlying material. This feature is crucial when working with delicate or compressible substrates.

In summary, flexographic printing is a direct rotary printing process that uses flexible, raised-image printing plates to transfer ink with light pressure onto a wide range of materials. These principles make it an extremely efficient and adaptable flexo printing solution, especially in the world of packaging, as we will explore further later.

The Origins and Evolution of Flexographic Printing

Flexographic printing, today a sophisticated and widely used technology, has roots that go back to the end of the 19th century. The first patent for a similar printing press dates back to 1890, filed in England by Bibby, Baron & Sons. At the time, water-based inks tended to smudge easily, so much so that the invention was ironically nicknamed “Bibby’s Folly.”

In the early 1900s, other printing presses in Europe began to use rubber plates and aniline oil-based inks. This led the process to be known as “aniline printing.” In Germany, for example, it was called “gummidruck,” meaning “rubber printing.” This early form of flexo printing found extensive use throughout the 20th century, especially for flexo printing on food packaging in the United States.

However, the history of flexographic printing suffered a significant setback in the 1940s. The U.S. Food and Drug Administration (FDA) classified aniline dyes as toxic and therefore unsuitable for food contact. Although flexographic printers were already beginning to use different types of inks, the name “aniline” remained, carrying negative connotations that caused sales to plummet. Attempts were made to rename the process with names like “Lustro Printing” or “Transglo Printing,” but with little success. Even after new, safe inks were approved in 1949, the shadow of the old name persisted.

It became clear that a radical change was necessary. In 1951, Franklin Moss, then president of Mosstype Corporation (a pioneering company in the development of plates and mounting systems for flexographic printing), launched a survey through his newsletter to find a new name. Among over two hundred proposals, a Packaging Institute committee selected three: “permatone process,” “rotopake process,” and “flexographic process.” On October 21, 1952, it was announced that the overwhelming choice of readers had fallen on “flexographic process,” or simply flexography. Thus, the term we know today was officially born. A fundamental contribution to the development of the modern inking system, with the introduction of the anilox roller, had already come in 1938 thanks to an insight inspired by rotogravure cylinders, developed by two men at the International Printing Ink Corporation.

From that moment on, flexography has not stopped evolving. Starting in the 1990s, in particular, enormous progress has been made. Flexographic machines (or flexo machines) have become increasingly sophisticated, innovative plate materials (like photopolymers) have been developed, more precise inking systems (like the central impression flexo drum for better substrate stability), and more performant and safer flexographic inks. These continuous improvements have transformed flexography from a process initially considered of rudimentary quality into a printing technique capable of competing with other more established technologies, becoming a mainstay for numerous flexographic printing companies and for the global packaging industry. Continuous research and development in flexographic machines and flexo printing plants ensure that flexographic printing continues to improve in terms of quality, efficiency, and sustainability.

Inside the Flexographic Machine: the essential components that bring printing to life

Now that we know the definition and history of flexographic printing, it’s time to delve into the beating heart of this technology: flexographic printing presses (or flexo machines). Understanding their key components is fundamental to appreciating the precision and efficiency of flexography. Each flexographic machine is a complex assembly of engineered parts, but some elements are universally recognized as vital for the flexo printing process.

1. The Anilox Roller: the precision Ink metering roller

Often called the “heart” of flexo printing, the anilox roller is a critical component that distinguishes flexographic printing from many other techniques. Its primary function is to pick up ink and transfer a uniform, precisely measured layer of it to the flexible printing plate.

Materials and Structure: Modern anilox rollers are typically steel or aluminum cylinders coated with a ceramic layer, a material chosen for its hardness and wear resistance. The surface of this ceramic coating is engraved with millions of tiny cells or alveoli.
The Cells: These cells are the key element for ink metering. Each cell has a specific shape and depth, designed to hold an exact volume of flexographic ink. The main characteristics of the cells include:
- Lines Per Inch (LPI) or Cells Per Inch (CPI): Indicates the number of cells engraved per linear inch on the roller’s surface. A higher CPI (e.g., 1200 CPI) means smaller, more closely packed cells, ideal for transferring a thinner ink film, necessary for printing fine details and high-resolution halftones. Lower values (e.g., 200 CPI) are used for solid areas or more absorbent substrates.
- Cell Volume (BCM – Billion Cubic Microns per square inch): Measures the ink capacity of a single cell. A larger volume carries more ink. Generally, as CPI increases, BCM tends to decrease.
- Engraving Angle: Cells are usually engraved at a specific angle (commonly 30°, 45°, or 60° relative to the roller’s axis). The 60° angle is often preferred because it allows for better coverage and more uniform ink transfer, reducing the risk of moiré effects (unwanted visual interference).
Operation: The anilox roller rotates partially immersed in an ink bath or receives ink from a feeding system. The ink fills the cells. A doctor blade then removes excess ink from the roller’s surface, leaving ink only within the cells. When the anilox roller comes into contact with the printing plate, the ink is transferred from the cells to the raised areas of the plate.

2. Flexographic Plates (Clichés): the image carriers

Flexographic plates, or clichés, are the flexible matrices that carry the raised image to be transferred to the printing substrate. Their evolution has played a decisive role in improving the quality of flexographic printing.

Materials: The very first plates were made of rubber. Today, most plates are created from photopolymers, UV light-sensitive materials. These can be supplied as solid sheets of predetermined thickness or as liquid resins.
Production Methods:
- Conventional (Analog) Production: This traditional method involves creating a film negative for each color/layer of the image. The negative is placed in contact with the photopolymer plate, and the assembly is exposed to UV light. The exposed areas of the plate harden (polymerize), while the unexposed areas remain soft and are removed during a development process (washing with solvents or water, or more recently, dry processes for thermal plates).
- Digital Production (Computer-to-Plate – CTP): This more modern technology eliminates the need for film negatives. A digital imaging device uses a high-power laser (often infrared) to ablate (selectively remove) a black masking layer from the surface of the photopolymer plate, exposing the underlying photopolymer in the image areas. Subsequently, the plate is exposed to main UV light (which hardens the ablated areas) and then processed to remove the unexposed polymer and residual black layer. CTP plates offer greater precision, repeatability, and reduced preparation times. Some flexographic machines can also use design rolls, cylinders with a laser-engraved rubber coating, particularly useful for continuous patterns.
Mounting: Once produced, the plates are carefully mounted on the plate cylinders of the flexographic printing press. This mounting typically uses special double-sided adhesive tapes, which must ensure secure and precise fastening to maintain registration between the various colors.

3. The Inking System: feeding the Anilox

The inking system is responsible for supplying a constant and controlled flow of flexographic ink to the anilox roller. Several configurations exist:

Two-Roller System with single doctor blade: Typical of older flexographic machines or narrow-web ones. A fountain roller, often rubber-covered, rotates in an ink pan (ink tray), picking up ink and transferring it to the anilox roller. A doctor blade presses against the anilox roller to remove excess ink, ensuring that only the ink in the cells is transferred. The pressure between the fountain roller and the anilox, and the speed difference between the two, contribute to metering.
Enclosed Chamber Doctor Blade System (Chambered Doctor Blade System): This is the most common configuration in modern high-performance printing machines, especially wide-web ones. In this system, the anilox roller is partially enclosed in a sealed chamber. Ink is pumped directly into the chamber, submerging the portion of the anilox within it. Two doctor blades seal the chamber: a “containment” blade prevents ink leakage, while the “metering” blade (main doctor blade) removes excess ink from the anilox surface as it exits the chamber. This system offers superior control of ink viscosity (as it’s less exposed to air), prevents contamination, and allows for higher printing speeds.
Other Systems: Variations exist, such as systems that pump ink directly onto the anilox surface (which is above a collection tray) with a single doctor blade for metering.

4. The plate cylinder: support for the Cliché (Plate)

This is a precision cylinder, usually made of steel, on which the flexographic plate is mounted. It must be perfectly cylindrical and balanced to ensure smooth rotation and uniform printing pressure. Various types exist, such as integral, demountable, sleeve-type (which slide onto an air-compressed mandrel for faster job changes), or magnetic for plates with a metal backing.

5. The impression cylinder: the Final “Kiss”

The impression cylinder is a smooth cylinder, also usually made of steel, that presses the printing substrate against the inked plate mounted on the plate cylinder. It is this contact, the “kiss printing,” that allows the image to be transferred from the plate to the material. Its surface must be perfectly smooth and clean. In Central Impression (CI) presses, a single large impression cylinder serves all color units, ensuring excellent registration control on thin and extensible materials. In some specific applications, especially to prevent ink buildup, it can be replaced by an impression bar.

6. Printing units and Press configuration:

A flexographic printing press is composed of one or more printing units, each dedicated to a single color. Each unit typically includes the inking system, the anilox roller, the plate cylinder, and the impression cylinder (or a portion of the central drum). The main configurations of printing machines for flexography include:

In-line Presses: The printing units are arranged horizontally, one after the other. They are versatile, suitable for thicker substrates like cardboard, and often integrated with other converting operations (die-cutting, lamination). They allow for front-and-back printing with the use of turn bars.
Stack Presses: The printing units are stacked vertically, often in two parallel columns. They also allow for front-and-back printing and are accessible, but can present challenges in registration control on very thin materials due to the longer web path.
Central Impression (CI or CIC) Presses: Here, all printing units (typically 4 to 8, but sometimes more) are arranged around a single, large common impression cylinder. The printing substrate is wrapped around this central drum and passes through each color station. This configuration is ideal for high-speed printing with precise registration on thin and extensible flexible films (like those for food packaging), as the material is constantly supported. However, they require longer setup times.
Corrugated Presses: Similar in configuration to in-line presses, they are however sheet-fed and designed to handle the rigidity and thickness of corrugated cardboard. They usually support a limited number of colors.

These are the pillars on which the flexographic printing machine is based. Their precise and controlled interaction is what allows flexographic printers to produce high-quality prints on a myriad of products we encounter every day. The continuous evolution of these components, driven by the needs of flexographic printing companies and flexo printing plant manufacturers, constantly pushes the limits of what can be achieved with the flexo printing machine.

How printing works: the flow of the flexographic process

After examining the key components, let’s now see how these interact to bring flexographic printing to life. The process, although complex in its internal mechanisms, can be understood by following the path of the ink and material through the flexographic printing press.

The heart of the flexo printing process lies in the controlled transfer of flexographic ink:

Ink Feed: The ink, characterized by low viscosity (i.e., very fluid), is drawn from a reservoir or ink pan. Depending on the flexo machine’s inking system, a fountain roller can transfer it to the anilox roller, or, in enclosed chamber systems, the ink is pumped directly into the chamber that partially encloses the anilox.
Metering with the Anilox Roller: The anilox roller, with its microscopic engraved cells, rotates and picks up ink. A doctor blade removes excess ink from the roller’s surface, leaving a precise and uniform amount of ink only within the cells. This step is crucial for the final quality of the flexo print.
Transfer to the Plate (Cliché): The anilox roller, now with its cells filled with metered ink, comes into contact with the flexographic plate mounted on the plate cylinder. The ink is transferred from the anilox cells to the raised areas of the plate.
Printing on the Substrate: The inked plate rotates and lightly presses (“kiss printing”) against the printing substrate (paper, plastic film, etc.). The substrate is guided between the plate cylinder and the impression cylinder (or the central drum in CI flexographic machines). At this moment, the inked image is transferred from the plate to the substrate. This cycle is repeated for each printing unit, each dedicated to a different color, to create multicolor images.

Parallel to ink transfer, the printing press manages the material flow:

Material Feed (Unwinding): Flexographic printing is typically a roll-to-roll (web-fed) process. The material to be printed, wound in large rolls, is loaded onto an unwinding system. Accurate web tension control from this stage is essential to avoid registration problems or material breakage during its passage through the printing machines.
Guiding and Passage through Printing Units: The web of material is guided through the various printing units. Precision in maintaining registration between colors is fundamental, especially on multi-color flexographic machines.
Drying/Curing: After the application of each color (or sometimes after a group of colors), the ink must be dried or cured before the substrate comes into contact with the next roller or is rewound. This is done via:
- Hot air dryers: Mainly used for water-based or solvent-based flexographic inks, where heat evaporates the liquid vehicle.
- Infrared (IR) lamps: Can assist with evaporative drying.
- UV (ultraviolet) lamps or EB (Electron Beam) systems: Used for special inks that cure (chemically harden) instantly when exposed to these radiations. This technology is increasingly common in flexographic printers due to its speed and environmental benefits.
Rewinding (or In-line Operations): Once all colors have been printed and dried/cured, the web of printed material is rewound onto another roll. Alternatively, many flexographic printing machines are flexo printing plants that integrate in-line finishing operations, such as die-cutting, lamination, slitting, or creasing, before rewinding or separation into sheets.

This continuous, high-speed flow is what makes flexographic printing an efficient solution for high-volume production, a characteristic valued by many flexographic printing companies. Precision in every phase, from ink metering to material control, is the key to achieving high-quality printing results with flexographic machines.

Why choose flexographic printing? the numerous advantages of a versatile technology

Flexographic printing hasn’t become one of the most widely used printing technologies in the world by chance. Flexographic printing presses and the entire flexo printing process offer a series of significant advantages that make it the ideal choice for a wide range of applications, especially in the packaging and label sector. Here are the main strengths that lead many flexographic printing companies and their clients to prefer flexography:

High Printing Speed: Modern flexographic machines (or flexo machines) are designed to operate at impressive speeds, often covering hundreds of linear meters of material per minute. This high-speed production capability makes flexo printing extremely efficient for handling large volumes and long runs, helping to reduce delivery times.
Versatility of Printable Substrates: One of the most distinctive advantages of flexographic printing is its incredible ability to print on an almost limitless range of materials. Whether it’s porous substrates like paper and cardboard (including robust corrugated cardboard for flexo printing on corrugated), or non-porous substrates like plastic films (polyethylene, polypropylene, PET, PVC), aluminum foils, adhesive labels, and even fabrics, the flexographic machine adapts effectively. This flexibility is crucial in the packaging world, where material requirements are extremely varied.
Competitive Costs for Long Runs: Although the initial setup and the cost of flexographic plates can represent an investment, this is quickly amortized over large print volumes. Production speed, efficiency in the use of flexographic inks, and plate durability contribute to making flexographic printing an economically advantageous solution for the long runs typical of the packaging industry.
Wide Range of Inks and Colors: Flexography supports the use of different types of flexographic inks, including water-based (increasingly popular for their sustainability and safety, especially for food contact), solvent-based (for specific adhesion and resistance needs), and innovative UV (ultraviolet) or EB (Electron Beam) curable inks. The latter offer instant drying, greater brilliance, and resistance. It is possible to print with a high number of colors in a single pass, allowing for the creation of complex and eye-catching designs.
Adaptability to Diverse Packaging Needs: Thanks to its versatility, flexographic printing is the technology of choice for countless types of packaging: from flexible food pouches to beverage cartons, from shrink sleeves to consumer product containers. The ability to print directly on materials like corrugated cardboard also makes it indispensable for secondary and tertiary packaging.
Possibility of In-line Finishing Operations Integration: Many modern flexo printing machines do more than just print. They are true flexo printing plants that can integrate various converting and finishing operations directly in-line with printing. These include die-cutting (to create specific shapes as in labels or boxes), lamination (to add protective or barrier layers), varnishing (for glossy or matte effects), embossing, slitting, and creasing. This integration optimizes workflow, reduces production steps, and delivery times.
Continuously Evolving Print Quality: While in the past flexographic printing was considered inferior to other techniques for fine detail quality, enormous technological advancements in plates (such as high-definition CTP plates), anilox rollers, flexographic inks, and process control in flexographic machines have significantly raised the quality level. Today, flexography can produce complex and photographic prints with excellent results, rivaling other technologies.
Efficiency and Waste Reduction: With proper setup and thanks to the automation present in modern printing machines, flexographic printing can be very efficient, reducing waste of materials, time, and resources, especially once long runs are started.

These numerous advantages explain why flexographic printing plays such a central role in modern industry, especially for everything related to packaging and labels. It is a technology that continues to evolve, offering increasingly performant and sustainable solutions to flexographic printers and their clients.

Inks, Materials, and infinite Applications: The World of Flexographic Printing

The versatility of flexographic printing is fully manifested when we observe the wide range of flexographic inks it can use, the numerous materials it can print on, and, consequently, the incredible variety of final products it is capable of producing.

The Inks: the color of flexography

Flexo printing employs low-viscosity liquid inks, essential for proper operation with anilox rollers and for rapid drying. The main types of flexographic inks include:

Water-based inks: Increasingly popular due to their reduced VOC (Volatile Organic Compounds) emissions and greater safety, they are ideal for food packaging and applications where environmental impact is a priority. They require drying with hot air.
Solvent-based inks: Offer excellent adhesion on a wide range of plastic films and non-porous surfaces, and good resistance. Drying occurs through solvent evaporation, often assisted by hot air or infrared.
UV (Ultraviolet) curable inks: These inks contain photoinitiators that, when exposed to UV light emitted by special lamps on the flexographic machine, cause an almost instantaneous hardening (curing) of the ink. They offer high gloss, excellent resistance, and do not emit solvents.
EB (Electron Beam) curable inks: Similar to UV inks, but they cure via an electron beam. They do not require photoinitiators and are suitable for demanding applications, including some safe food packaging, given the absence of substance migration.

The choice of ink depends on the printing substrate, the final application of the product, and the required performance (e.g., resistance to grease, moisture, abrasion).

The Printing substrates: a limitless canvas

One of the great strengths of flexographic printing is its ability to adapt to a multitude of substrates. Flexo printing machines can work with:

Porous materials: Various types of paper (kraft, coated, label paper), paperboard (for folding cartons, food boxes like milk or ice cream cartons), and corrugated cardboard (for flexo printing on corrugated cardboard intended for shipping boxes and displays).
Non-porous materials: A wide range of flexible plastic films such as polyethylene (PE), polypropylene (PP, both oriented and non-oriented), polyester (PET), PVC. These form the basis for bags, pouches, snack wrappers, shrink sleeves, and many other types of packaging.
Metallic foils: Mainly aluminum foils, used for example in yogurt lids or barrier packaging.
Laminates: Multilayer materials composed of different combinations of paper, plastic films, and aluminum, created to offer specific barrier properties (against moisture, oxygen, light) crucial for product preservation.
Adhesive labels: Self-adhesive materials of various kinds, printed in rolls and then die-cut.
Other materials: Flexography can also be used on fabrics, non-woven fabrics (TNT), and wallpaper.

The applications: flexography in everyday Life

Given the variety of inks and substrates, it is not surprising that products made with flexographic printing are ubiquitous:

Flexible Packaging: The largest market share. Includes bags for chips, coffee, pasta, pet food, candy wrappers, pouches for baked goods.
Labels: Another key sector. Adhesive labels for bottles, jars, cosmetic and pharmaceutical products; wrap-around labels; shrink sleeves that conform to the container’s shape; In-Mould Labels (IML).
Beverage and Food Cartons: Cartons for milk, fruit juices, broths, ice cream.
Corrugated Cardboard Boxes: From simple shipping boxes to more elaborate ones with colorful graphics for point-of-sale displays.
Sacks and Bags: Paper bags for groceries or bread, plastic bags.
Disposable Products: Paper or plastic cups, napkins.
Gift Wrap and Wallpaper.
Sanitary Napkins/Pads.

The ability of flexographic printing machines to handle these different flexographic inks and substrates efficiently and at competitive costs for large volumes has made flexography an indispensable technology for the global packaging and label printing industry. Flexo printing plants are designed to maximize this versatility, often integrating finishing processes that transform the printed material into the final product within the same printing machine.

From its definition as a relief printing process using flexible plates, through its fascinating historical evolution to the name “flexography,” we have explored the internal mechanisms of flexographic machines. We have seen how crucial components like the anilox roller, photopolymer plates, and sophisticated inking systems work in synergy to achieve flexo printing.

The process itself, starting from the feeding of ink and material through to drying and rewinding, is a ballet of mechanical and electronic precision, optimized for speed and efficiency.

We then understood the wide range of flexographic inks available: water-based, solvent-based, UV, and EB, and the incredible variety of substrates, from paper to the most complex plastic films, that can be enhanced with this technique. This flexibility translates into a universe of applications that touch our daily lives: from food packaging that preserves product freshness, to labels that inform and attract us, to sturdy boxes that transport goods around the world.

The advantages of flexographic printing: speed, material versatility, competitive costs for large volumes, customization possibilities, and integration of finishes – have decreed its success and continuous growth in the industrial landscape. Despite competition from other technologies, flexographic printing remains a cornerstone, especially for the packaging world, a constantly expanding sector that requires increasingly high-performing, customized, and sustainable printing solutions.

Flexographic printing, with its continuously evolving printing machines and flexo printing plants, is more than just a simple technique: it is a fundamental engine of modern industry, dressing and protecting the products we consume, communicating values and information effectively and colorfully. It is the high-tech evolution of a simple idea, perfectly adapted to the needs of our packaged world.

Written by Andrea G. | Team Giugni®