Flexographic printing, also commonly referred to as flexo printing, is a highly useful printing method, praised for its efficiency in printing large quantities of repetitive images very quickly and for a fraction of the price of other printing methods. It is a classic style of printing, with the first models being patented in the late 1800s.
Initially, it was a sub-par printing option, first due to problems with smearing ink, then due to health concerns regarding the ingredients found in the ink. Since then, however, it has become an increasingly reliable and high-quality printing option, and its speed and versatility make this one of the top choices for many companies. It is most commonly used for printing on packaging labels.
1. Feeding the materials
Step one of the flexographic printing process is that the material needs to be fed into the machine. Flexo printing supports almost any material, which is why it is so popular for food packaging. Some of the materials flexographic printing supports are paper, cellophane, plastic, cardboard, and metallic film. Flexographic printing uses the web-fed method to deliver materials to the printer, meaning the materials come in large rolls, allowing the machine to continually pull the material through.
One of the reasons this method of printing is so fast is that the materials are continually pulled through, and the space is used efficiently This means that printers will put as many labels both vertically and horizontally on the sheet as possible, keeping wasted material to a minimum. Flexographic printers can pull through almost 6.5 kilometres worth of material per hour.
2. Preparing the template
Plates that contain the desired design are wrapped around print cylinders which, as they turn, run through the ink and onto the material. Each new colour in a label requires a different plate, so many flexographic printing companies will have multiple print cylinders in a row, creating a kind of assembly line from start to finish. As the materials pass by each print cylinder, another layer is added until the final product comes out the other side. The plates are thin, bendable sheets that have a positive, mirror image of the visual.
3. Picking the colour
Nowadays, colours are matched and planned using computer programs. Companies will often have cyan, magenta, yellow, and black, which are the base colours needed to make pretty much any colour. Using the computer program to help them figure out the exact colours needed, the colours can then be mixed and added to the printer where the print cylinders will eventually roll through them. Colours are generally based on the Pantone Matching System (PMS), which allows for high levels of consistency.
4. Drying ink
After the printing has been done, the ink must dry. But the inks used in a flexographic printer are different than those one might find in their regular household printer. These inks are ultraviolet (UV) curable, which means they don’t dry in the air. They require a UV light to cure them instead. These inks are also water-based, and are less harmful to the environment, in general, than inks that are used for other purposes or than inks that have previously been used for flexographic printing.
Due to the continuous printing method used for flexographic printing, the labels must later be cut from the large sheets, and also from one another. The cutting die is another cylindrical unit used to remove all of the excess material from the labels. These pieces are custom-made for each individual label, which allows them to be detached perfectly from one another, and to all be identical in size and shape.