As the world of printing technologies continues to advance, everything around us is slowly turning into output produced by printers. At such a moment, it is important to know about all types of printers so that you can easily fish out the ones you require in times of need.
Today, we will explain flexographic printing; its evolution, principle, and process will be explained in depth. So please take a moment to go through the article and identify its applications, pros, and cons. By the end, you might even find that it is better suited than the other printing technologies you have been using!
Flexography Printing History
Although flexographic printing technology has managed to leave its mark in the printing world, it all started as a big mess. The first flexographic printing device was discovered in 1890 and is operated using a system that imprinted water-based inks onto webs. Unfortunately, the results were always smudged, meaning it wasn’t of much use.
A decade of research later, people were finally able to build a much more reliable printing press that used rubber flexo plates. Aniline oil-based inks were used to draw smudge-free results on substrates, causing the process known as aniline printing. However, the process still lacked precision and was only used to create food packaging and the like.
As image prints were unable to be produced using the flexographic printing technique, people tried to upgrade the printing parts. After many trials, in the late 20th century, the rubber plates were finally switched out for photopolymer ones which were easier to produce. This served as a major upgrade since the plate’s appearance always matched that of the negative films used to make them. Colored outputs could also be received as different plates could be developed for getting each colored ink.
Anilox rolls were manufactured in the last step of the flexographic press’ evolution. This increased efficiency and precision since inks were always carried within cells that were carved out with the assistance of laser-etching systems. Doctor blades were also installed on the surface of these rolls preventing excess ink from damaging the look of your hard copies. With time, more and more work was put into making such anilox rolls, serving users with higher definition results.
How Does Flexography Printing Work – Printing Principle
A typical flexographic printer hides many components that surround the polymer or magnesium-made flexo plates. All of the parts contribute to the printing process, so that we will explain the working principle through them!
The flexographic printing process starts as soon as the fountain roller collects ink on its surface. It does so by rolling in an ink tray or pan which holds your liquidated ink. Solvent-based ink, water-based ink, ultraviolet (UV) curing ink, electron beam (EB) curing ink, and two-part chemically-curing inks are some options that you can choose from.
Anilox rolls are connected right on top of the fountain rollers – an extremely special section of your flexography machine. These rolls are engineered uniquely so that their cells can hold a specific amount of ink, making it easy for them to absorb just that much. In addition, the pores in these cells are microscopic; hence, the ink particles need to be smaller to fit in.
Doctor blades made out of steel or polymer are always fixated on the surface of the printer’s anilox rolls. They have filed edges that wipe all excess ink off your anilox rolls’ surface, ensuring that ink is only present in the pores carved on the body. The extra ink is immediately discarded back into the fountain roller, successfully avoiding the wastage of expensive resources.
The plate cylinder is a cylindrical tube on whose surface you are supposed to mount your registered flexo plates. During the operation process of a flexographic printer, the anilox roller and plate cylinder are both spinning on an axis while being in contact. As a result, the fixed amount of ink from your anilox rolls is transferred to the flexo plates attached to the cylinder’s surface.
Flexo plates are made out of photopolymers that give off a flexible and soft texture. They can be bent and hence, are able to surround your plate cylinder effortlessly. Magnets, tension straps, and tapes are often used to hold them into position and prevent the creation of slanted images.
As flexo plates have raised sections etched onto their exterior, the ink is only pasted onto those surfaces. This means that any imprint created will have the same pattern as what is shown on your flexo plates.
Right next to the plate cylinder, you will find the impression cylinder or “print anvil.” This portion of your printer holds the substrate or web, which has the job of receiving your image. It also applies pressure, causing the ink to be received accurately.
When the ink has been completely received by the web, your printer has reached the end of the printing section. Now, the web will need to be dried to make sure that the ink applied does not get smudged.
The drying stations of your flexographic printers differ based on their ink compatibility. Most contain a constant flow of high velocity heated air, which speeds up the drying process. After-dryers are also present, ensuring that the printing process reaches a nice ending.
A special drying station is present for printers that use UV curing ink where UV rays are emitted instead. These rays cure the ink that was pasted onto the substrate, creating the final product that people wished to receive.
Outfeed and Rewind Section
At last, the web is given out through this section, ensuring no tension is created. It prevents tears from occurring and is responsible for untangling the segments for the users.
Once all this ends, users are presented with the awaited results of their flexography printing!
Types of Flexographic Printing Machine
Printers that run using flexographic printing technology can be distinguished into stack presses, satellite or CI presses, and in-line presses. Let us give you a quick introduction to each!
Stack Press Flexo (also known as Tiered Flexo)
When compared with other flexo machines, the stack type always has more compact dimensions. This is possible since all the printing units are shelved one above the other.
Small and even smaller running costs act as a benefit, making such printing devices suitable for offices or factories. In addition, users can print on both sides of their substrate, allowing them to save a lot of their resources whilst printing.
However, it needs to be noted that the stack-type flexo machines perform rather poorly in terms of print quality. In addition, the operation process is relatively complex because the large gaps between gears and color grouping are also pretty tough. Thus, when using these machines, it is best that you stick to printing text outputs only.
Satellite Flexo (also known as Central Impression Flexo)
The satellite flexo earns its name Central Impression (CI) due to its unique structure, which allows all printing units to be grouped in a central drum. This causes the color group of such machines to be dependent on the central drum’s proportions.
As for quality, the satellite flexo machines offer an unmatched level of precision for both – monochromatic and colored outputs. In addition, very little tension is created on the substrate while printing, making the printer ideal for thin webs which are quick to distort.
Drawbacks are only faced with cost as the initial purchasing price is pretty high. Printers with small cylinders also tend to have a very limited color group and complicated arrangement processes.
In-line Flexo Press (also known as Unite Type Flexo)
If you are looking for a flexographic printer that is easy to operate, the in-line flexo will undoubtedly be the best pick for you. The operation starts with a unwind and infeed section that looks after your webs and prevents them from getting damaged due to tension. Then, the printing section and its components use the ink before sending the substrate to a drying station. Lastly, a rewind and outfeed station are also present, all of which combine to provide flawless results. All of these stations are horizontally fixated, making operation and transmission rather straightforward.
What is the Flexographic Printing Process?
The flexographic printing process can be divided into four long steps:
Step One: Making Plates
Light-sensitive photopolymers are frequently used to make plates for flexographic printing. Images or text outputs are printed out on a negative film and then pasted onto the surface of your plates. These plates and the negative films are then exposed to UV light, causing the parts that receive the light to harden instantly. The remaining section gains a soft gum-like consistency, allowing it to be washed away when in contact with the liquid used during the washing process. This liquid consists of a combination of water and 1% dishwashing solutions with a temperature of 40 °C. Aside from this, acid baths or computer-guided laser rays can also be used to achieve the curing on such printing plates.
Step Two: Drawing the Registration Marks
To effectively mount your plates on the plate cylinder, you will need to draw the registration marks on your plate. This includes microdots or crosses, which are engraved using special machinery. Precision needs to be maintained to the dot as otherwise, mounting will be extremely time-consuming, and hindrances will keep on arising while printing.
Step Three: Mounting the Plates
Mounting the plates on a flexographic printer’s plate cylinder requires a microscopic level of precision that humans cannot achieve. So instead, you will need an automatic flexo plate mounter that uses video mounting to ensure accuracy. Throughout this process, many cameras with high magnification power are used to align the registration marks with your plate cylinder’s mounting signs.
Step Four: Printing
Once the flexo plates have been mounted accurately, you should try initiating the printing process. When you start the machine, the anilox rolls are automatically inked with the assistance of a fountain roller and ink tray. It then manages to apply ink on the raised portions of your flexo plate, which is pressured onto the substrate or web to give you your desired prints.
Flexography Printing Application
Flexographic printers are regularly used to print things like shopping bags, milk cartons, self-adhesive labels, disposable plastics, etc. This means that most factories or shipping platforms will resort to employing a flexographic printer to cater to their needs.
With time, as this printing technology becomes more and more renowned, people have started to explore new usage limits. This has introduced laminating and newspaper printing to some of the printer’s capabilities. Due to the excellent image quality, many people have also started producing magazines and pamphlets through this process. As the colors are separately laid onto the surfaces of the substrates, accuracy is maintained to the dot.
Flexography Printing Advantages and Disadvantages
- High-volume printing tasks can be finished in a jiffy because of the fast printing speed.
- Many types of ink can be used, giving the users many options.
- The production process remains continuous since cutting, drying, and varnishing are all accomplished in one go.
- Running costs are pretty low as photopolymer plates and substrates tend to be inexpensive.
- The process is environment-friendly.
- Start-up and setting times can be quite high.
- Operating the flexo machines is cumbersome and hence, requires professional knowledge.
- It can prove to be rather costly for small-scale tasks.
- Lots of plates need to be manufactured to get colored results.
Flexography printing can prove to be extremely useful in professional industries. Despite having a very complicated operating process, they bring along unrivaled printing speeds for large-scale print jobs. Furthermore, with time and advancement, the quality also keeps on increasing to provide admirable results. So, if you perform large-scale printing tasks and are interested in making labels, tapes, or cartons, then do look out for such printers. First, check out the different types available and then pick out the one that will suit you the most. Using them will definitely help you save some bucks along the way!