What is Flexographic Printing?
Today, we will study about Flexographic printing. It is a roll-feed web printing process. If you are looking to print a bulk amount of packaging and labels, then Flexographic printing is for you. Flexography presses use different types of foils, paperboard, papers, films, and corrugated board for printing. They can achieve speeds of 500 to 2000 feet per minute.
There are a variety of products printed on flexographic presses such as shrink-sleeve labels, adhesive, shopping bags, ice-cream cartons, gift wrap, pouches, folding cartons, wallpaper, tissue, disposable cups, and plates.
We can say that flexographic printing is a very beneficial technique for companies to advertise their products and business.
How does It work?
The first step in flexography is to wrap the flexible photopolymer around a rotating cylinder for each color. In the letterpress printing process, the text and graphics for all colors are raised from the plate’s surface. The same is done in flexography. The next step is to ink the raised areas of the photopolymer plate.
There are typically four types of rollers that we use in flexographic presses. These rollers include:
- Anilox Roller
- Impression Cylinder
- Fountain Roller
- Plate Cylinder
Rollers play an influential role in presses. The fountain roller sends ink from the ink pan to the ink-metering (steel or ceramic) anilox roller and then delivers it to the plate cylinder. Now we will apply ink to the substrate as our paper passes between a polished metal impression cylinder and the plate cylinder. The impression cylinder’s function is to use the suitable pressure, which is required for transferring the ink from the plate to the paper (substrate). In flexographic printing, the use of an anilox roller is to transfer the ink of uniform thickness to the flexible photopolymer printing plate. Each anilox roller has cells finely engraved that contains specific ink capacity.
There is an optional doctor blade that scrapes the anilox surface to make sure that the ink only delivers from the engraved cells to the printing plate. When the substrate passes through the press, a different coating or color is spread at each printing deck. Printing decks have drying units that make sure that all ink colors are thoroughly dried. Dryers use infrared or ultraviolet light or hot air for drying purposes, depending on the application.
In this type of press, we vertically stack the printing decks. The stack press can print on each side of the materials when it passes through the press.
Central Impression Press
There is a single large impression cylinder in the Central Impression press (CI) around which the printing decks are located. This press provides impressive registration.
In this type of press, the printing decks are located in a straight line for handling heavier substrates efficiently. It’s ideal for substrates like corrugated boards.
There are a variety of wide-web press models that are specifically built to handle rolls of material ranging from 21 inches up to 80 inches wider.
The Narrow-web presses’ primary function is to print labels. The labels are very small, that’s why the narrow-web presses are 10 inches wider or smaller.
Nowadays, narrow-web presses of up to 20 inches wide size are used to print shorter runs of flexible packaging, which includes pouches used for teas, flexible packaging such as bottle wraps and the smaller packets, single-serve packs, and drink mixes.
Flexographic printing uses a variety of inks such as energy – curable inks, solvent-based, and water-based inks for packaging. The most quickly cured ink is energy-curable and is fixed with the help of an electron beam (EB) system or ultraviolet (UV) light. EB curing systems are more beneficial as compared to UV-curable inks because it transfers energy directly to the inks in the form of energetic electrons and doesn’t need photo initiators.
The corrugated packaging printing uses water-based inks. Solvent-based inks are beneficial for industrial films and plastic shopping bags. EB and UV inks are ideal for printing outer wraps for food packaging.
Flexographic presses can print on various substrates which include:
- Liner board
- Coated or Uncoated papers
- Aluminum Foil
- Carton Board
It also uses various kinds of plastic films, including bio-oriented polypropylene (BOPP), low-density polypropylene (LDPE), polyester (PET), and polypropylene (PP). Flexography printing can be done a variety of laminates and on non-woven fabrics.
In the packaging industry, laminates are usually multi-layered materials that are made from various combinations of substrates, including paper, aluminum foil, and film. Laminates are a kind of protection from chemical contamination, moisture, or air for flexible packages.
Prepress, Platemaking, and Press Set-Up
As we know, that flexographic printing procedure involves high-speed processing, so there is always a fear of wastage of inks and other useful materials. We could face loss if we find shortcomings in print quality during the press run. Various factors affect the print quality, which includes the quality of plates used and how these plates were produced. As there are many factors involved in flexographic printing, it requires experienced and professional ones to be done.
Let’s assume that the image broadens as the flexible photopolymer plate is enacted to the cylinder. This shows that our pictures to be reproduced should be made a little smaller than their original size. The dots in a screened halftone picture can develop in width when printed because of the ease of the inks, the idea of the substrate, and the impression chamber’s weight. This dab addition can make hues look dim or sloppy. Alterations for the anticipated measure of dot addition can be made during designing and prepress.
The first flexographic printing plates were made of elastic. Today, they are commonly produced using photopolymers. These UV-light delicate materials are either gooey fluids of strong sheets of an assigned thickness.
In conventional plate making, an advanced image setter makes film negatives of substance that will be printed at each print deck. Photos and outlines with apparent degrees are prepared with halftone screening strategies that re-make tones with various sizes of ink mixes, dots, and dot placements. The film negative is set onto the photopolymer plate material and stacked into a presentation unit and presented to UV light controlled measures. The uncovered photopolymer plate material is then evolved with water or solvents that eliminate the plate’s unexposed picture territories. (Dry, warm polymer plate preparing is an option placemaking strategy that disposes of the requirement of washing the plates after the presentation.)
Computerized photopolymer plates wipe out the need to make film negatives. A dark, light-delicate layer covers the outside of the plate material. An automated imaging gadget at that point utilizes a powerful infrared laser to eliminate the dark layer where the picture will be delivered on the plate. This cycle is called laser removal.
When the advanced photopolymer plate is presented to UV light, the light actuates the photopolymer plate material where the dark layer has been eliminated. The plate is washed, dried, and slice to the size that will be mounted on the chamber. A few clients of flexographic presses send computerized documents to flexo-printing specialists at platemaking administration authorities. As desires for quick turnaround times develop, producers of prepress programming and gear have been robotizing the flexographic prepress and plate making measure. Robotization will lessen the need to re-appropriate plate making and limit the danger of mistakes in designing files for full-shading flexo prints that will be changed over into various sorts and sizes of bundles.
For instance, Esko bundling plan programming helps creators make and see three-dimensional structures for collapsing containers, contract sleeves, creased boxes, and adaptable bundling. The Print Control Wizard for Esko’s computerized plate making frameworks considers factors such as imaging goal, presentation settings, plate materials, substrate, anilox, press type, and inks to create the correct screens and dab gain pay bends for every application.
Registration (the exact arrangement of ink mixes on the substrate) is likewise necessary to shading exactness and print quality. Enrollment blunders can be brought about by prepress or plate mounting botches, absconds in the impression chamber, filthy chambers or plates, horizontal developments of the webbed substrate, the inappropriate surface pressure of the substrate and different components.
Finishing processes, including cold foil stamping, varnishing, and die-cutting, can be used in inline presses for improving the efficiency of developing rolls of labels that are ready to use.
There is a device named the slitting machine. Its purpose is to cut the big rolls of printed materials according to their specified size.
The material, including gluers, specialized folders, and converting types of equipment is useful for altering the printed rolls of substrates into corrugated boxes, folding cartons, sealable pouches, and a variety of packages.
Now, we will discuss the advancements happening in flexographic technology. It is rapidly improving due to a high demand in the market. It provides faster turnaround times, short-run lengths, and higher quality prints.
Let’s discuss the reasons for the growing flexographic technology.
It has reduced the requirements of expertise and reduced the time for plate making, prepress, and plate changeovers.
Enhanced the recycling ability of printed packages and labels.
It has also minimized the waste level, which is occurred by press set-up errors and prepress.
In 2013, the flexo-printer producer BOBST propelled the REVO Digi Flex venture related to makers of value control frameworks, inks, plates, shading estimation apparatuses, and other pressroom supplies. This consortium of organizations has been working together to manufacture a computerized, broadened shading range flexographic printing framework that will require insignificant administrator intercession.
The objective is to give worldwide shading consistency and repeatability in marks, adaptable bundling, collapsing containers, and layered sheets. The undertaking will likewise help guarantee shading coordination between digitally printed materials and flexographic materials.
Extended Color Gamut (ECG)
In this type of flexographic printing, cyan, yellow, black, and magenta inks are also used with green, violet, and orange inks for matching the highest percentage of Pantone colors.
Our digitally made systems keep the hold of mixing and delivering these multiple process colors of ultraviolet-curable inks. Systems will automatically become in contact with the plate cylinder for setting the correct impression. In this way, all the colors develop on the labels as well.
Hybrid flexo/inkjet printing systems
The inkjet printing method is the new evolution in printing technology. Some flexographic printing companies use inkjet-printing units. These units include full color floating data to flexography printed substrates.
It is beneficial for flexographic printing owners to deliver customers excellent quality. It’s ideal for those clients who wish to put in codes for packaging, tracking, authenticating packages, or allowing customers to remain connected to online content.
It is the most comprehensive guide; you will ever find about flexographic printing on the internet. We shared every single useful information with you, so you don’t need to search anywhere else. If you have any queries, then don’t hesitate and comment below to get a satisfactory reply.