Flexographic printing is a printing system widely implemented around the world for printing personalized labels at high speed. It is a traditional printing method that has been perfected over the years. Thanks to a set of evolutions in its prepress and printing techniques. Flexography is present in various markets and is, today, the most widely used printing system in Packaging, with materials as diverse as flexible packaging, corrugated cardboard, paper, compact cardboard and cardboard, sleeves, films, etc. Due to its advantages and characteristics, it has had an important growth in the production of labels.
This does not pretend to be an excessively technical article, there are specialized books for this purpose, but it will try to solve basic doubts about a printing system that has been said to be the secret of its good realization is in the control of the variables, due to the large quantity of processes and materials that take part in its elaboration.
What is flexographic printing
Flexography is a system of direct printing (iron directly transfers the ink to the support) and mainly rotational (roll and material coils of different sizes) in which flexible plates are used with high reliefs and a structure mainly formed by rollers. The word flexo comes from the Latin word "Flexus", which means bent.
This technique is a quick and inexpensive way to apply simple designs. As well as colored areas to a wide variety of materials such as corrugated cardboard, plastics, self-adhesive labels, envelopes, etc. The main advantage of flexographic printing is the ability to print on different substrates.
Flexible plates are used in this technique. Also known as clichés, which for high quality are made of photopolymer, a very durable material that allows finishes with greater detail. Rubber or rubber plates are also used to make, for example, the classic tampons. The water-based inks currently used in flexography dry quickly by evaporation and are safe to use for all types of coatings that come into direct contact with the product. For other types of inks such as UV (ultraviolet) their polymerizations with lamps are also accepted for many products, but in food products low migration inks are required. Currently, to save energy consumption and avoid ozone emission, UV LED inks are being implemented.
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History of flexography
The history of flexography dates back to 1890 when the first press was patented in Liverpool and used water-based ink, making it bleed easily. At the beginning of the 19th century other pens were developed with rubber plates and aniline oil-based ink . So this printing process is known as "aniline printing" (a term used until the 1950s). At this time the anilox roll was developed, an ink roll that was engraved and was suitable for transferring ink to an aniline printing plate. Today, that roller continues to be used in flexographic presses.
Over the years it was realized that aniline ink was unsuitable for food packaging and was declared toxic by the Administration Food and Drug Administration (Food and Drug Administration). Then, they began to look for alternatives until in 1949 the Food and Drug Administration approved new inks that were not harmful to health. However, the population remained concerned about their health, despite not using aniline. In 1951 it was decided to run a contest to change the name of this process and finally in 1952, for the good of the industry, the name was changed to flexographic printing.
Since then, the flexographic printing industry has undergone many innovations. At the end of the 20th century, flexography began to be used in newspapers thanks to its simplicity and ease. Currently, more than 60% of the packaging industry uses flexographic printing.
Flexographic printing process
First phase: prepress
The production of flexographic printing begins with an idea or a design, generally packaging (boxes, labels, containers, bottles, etc ...). This process begins with the creation of the design digitally and ends with the preparation of the plates, which can be done in-house or ordered from an external engraver. Finally, a plate is processed for each base color, which, later in the printing process, are superimposed to achieve a faithful reproduction of the design.
When the plates are ready they must be incorporated into a printing cylinder which is covered with mounting tape. The iron is placed on it. The placement of the plates is very important because poor placement may give unexpected results and the process must be started again.
Once ready, it is time to introduce the colors that in the case of four-color are CMYK (Cyan Magenta Yellow Black), but it also allows incorporating direct colors that are superimposed to reproduce the needs of the design. To avoid a second pass, the design should have a maximum of colors, varnishes, etc. equal to or less than the number of printing units of the printing machine.
Second phase: printing
For this, we need a flexographic machine suitable for the type of product to be printed. A label machine (generally in-line, coil-to-coil and narrow web) is not the same as a machine for corrugated cardboard (generally large-format and coil-to-sheet) or flexible material (generally central drum and broadband), as examples. Once we have the plates and the entire machine ready, the second process to follow arises when the molded plate is placed on the cylinder or plate holder roller, which is inserted inside the printing machine. Inside it comes into contact with the anilox roll, which can be made of ceramic or steel. In the anilox roller we have small cavities (cells) where the ink is housed which, when rotating, comes into direct contact with the raised areas on the printing plate. After being inked, it continues to rotate, until it finally comes into contact with the substrate, generating the impression by transferring the ink to the final support.
Although flexography, like any type of printing, has its limitations, today it is competing with other printing systems for different reasons. Also, it competes with gravure because the machines are getting faster, the quality is better and it is economically more viable for short runs, which is the market trend. It competes with digital printing for cost, except for very small runs. Likewise, it competes with offset for long runs in narrow web and why the quality, although not for the highest demands, begins to be excellent. In addition, flexography has the advantage that it can apply large masses of ink with a highly valued effect, and it is an essential body for combination or finishing machines, to apply varnishes, blanks, glues, etc.
Technically, we can accept that it has small disadvantages such as the squash effect, which is a splash of ink around the printed point that affects intonation and color adjustment, the fact that over time the printer plates end up deforming; that the four-color printing system has limitations; that causes marbling (areas that should be printed are not due to soiling on the cliché) although it can be avoided by keeping the plate clean, or that, due to the type of plates used and the printing system, the dot gain is greater, with which the lineatures and the minimum sizes of the fonts or lines are less precise than in other types of printing. However, the registry improvement has improved a lot, even though jobs need to be trapped,
Characteristics of flexography
Versatility
This system allows the use of various types of ink. For example water based ink, solvent based ink or UV curable ink. In addition, any flexible material can be used, whether porous or not.
Speed
Flexographic printing machines can reach high speed per minute. This allows for long runs. Even make short runs at an affordable price.
Automation
A flexo machine is very easy to program.
Little maintenance
flexo printing does not require a lot of maintenance. This reduces the maintenance price.
Low cost
The materials used in this type of machinery are usually very low compared to other types of printing. Although the iron is more expensive, it is a very profitable option and provides a quick return on investment.
Environmentally friendly
The machines allow the use of recycled, water-based inks. Even the plates are washable with water, this allows this type of printing to be more ecological than the others.
Color palette
Basic flexo uses 4 colors (CMYK): cyan, magenta, yellow, and black. But, you can incorporate as many spot colors as each machine configuration accepts to expand the gamut. In this way, we can print everything we want.
Flexographic printing machines
Nilpeter FA-Line Label Printer
The FA-Line is the most versatile flexo press on the market. Designed to meet the growing needs of the industry and built with an intuitive user interface and fully mobile printing controls. This equipment allows for improved performance. With the ability to add value-added units, application packages and automation based on application needs and budget.
Its technical specifications:
Nilpeter FB-Line Label Printer
The FB line responds to the growing need for process automation and greater ease of use. This line is presented with a series of additional features, such as the Automatic Plate Positioning System (APPS), the foot-registration and pre-registration functionality. This line is designed to print value-added labels in the most efficient way at high speeds. This kit is available in 13 '' width and 16 '' width. A flexographic press designed to offer maximum flexibility at an affordable price. Their characteristics are:
Eif 450 - Cliché maker
EiF 450 Video Plate Mounting Machine , the easiest and most accurate solution for polymer mounting The ergonomic and intuitive design allows it to fit most printing rollers. The mounting of the clichés is much faster than in the traditional assemblers.
Direct to Garment (DTG) T-Shirt printing or digital T-Shirt printing is the process of printing full-colour images onto garments.
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