Printing - Flexographic printing - Label printing
Flexographic printing is undoubtedly one of the most universal and widespread printing methods. You can print on a variety of materials, with different print cylinder widths and different colors. Particularly suitable method for printing sleeve printed materials. Corrugated cardboard, paper, films, foils, cardboard, labels, newspapers, multilayer bags, tissue, liquid packaging, etc. are only a small part of the possibilities of flexographic printing. They are printed using water-based, solvent-based, UV or EB-inks, thin or thicker printing plates made of photopolymer, rubber or elastomer - analogue, digital or directly laser-engraved, made using solvent, water or thermal methods.
The plates are attached to the cylinders or sleeves using special products - rigid or foam strips of different hardness or compressibility. The machines used can be built on a different principle - satellite (around the central shape cylinder are printed cylinders) or in-line (as in offset printing) or in a way that the printed sheets must be fed and passed directly through the machine, etc.
Mounting tapes are widely used in the printing industry. They are used successfully in various printing technologies, but are perhaps most widely used in flexographic printing processes. The specifics of the materials used, inks and the introduced production conditions require the use of mounting tapes with different characteristics.
Typically, most large manufacturers offer formatted rolls cut to standard widths to make it as easy as possible for the end user. A number of ready-made standard widths are available: 310mm, 620mm, 910mm, 1065mm, 1130mm, 1240mm, 1280mm, and you can always request a size that is most comfortable for you. The length of the roll can also vary: 4.5m, 5m, 10m, 15m, 25m. Some manufacturers, for the convenience of customers, offer mounting strips of different colors, which helps to quickly distinguish them during the work process.
Depending on the type of printed image and the production itself, you can choose from a diverse range of mounting tapes. Each edition may require a different combination of clichés and clichés, inks and anilox shafts, materials, drying settings and more. The client can judge for himself whether the achieved print quality is optimal or it is necessary to change the used adhesive solutions. Of particular importance is not only the hardness of the adhesive layer itself, but also its thickness. In the most commonly used installation solutions, the layer thickness can be, for example, 0.10mm, 0.15mm, 0.20mm, 0.25mm, 400µm, 550µm, 1250µm. Each of the major manufacturers gives its recommendations for the use of different mounting tapes, depending on the type of product and the type of images for printing.
There are different types of mounting and adhesive tapes on the market for attaching the printing plates on the printing cylinder with different adhesion. This can often be due to whether they are intended to attach the adhesive layer first to the surface of the printing plate or directly to the printing cylinder / sleeve itself. Mounting tapes are also available on the market, using which you can choose where to apply at the beginning of the work process, depending on your established production practices.
Mounting on the printing cylinder
The first step to begin is to unscrew the mounting tape and secure the leading end to the surface of the print cylinder. You should wrap it around the print cylinder from end to end. You must be careful not to let air in, which will create air bubbles and bumps. Continue laying the tape on the cylinder while gently unrolling it. Keep the roll in an inclined position to avoid unwanted air entering between the adhesive layer and the cylinder surface. If this still happens, you can easily remove the air with a scalpel, but be careful not to damage the surface of the print cylinder.
If it is necessary to make a butt joint in cross section, then in order not to damage the surface, a ruler or blunt squeegee knife is placed under the leading end of the mounting tape. Wrap the mounting tape over the entire surface of the print cylinder and stack both ends on top of each other. If at all possible, try placing the squeegee at an angle of less than 45 ° to the surface of the print cylinder. Cut both layers of tape and remove the excess.
After applying the tape, it is recommended to press it to increase the contact surface and the adhesion itself, making sure that it is as even as possible. If the attachment of the printing plate is done manually, then one way is to use a special rubber roller.
Many mounting systems greatly facilitate the actions described above, especially when it comes to a larger print cylinder area. Such systems usually have a built-in cutting system. Whenever possible, we recommend the use of a laminator to ensure proper bonding. In order to minimize the detachment of the printing plate, it is recommended not to cut the mounting tape exactly to its size. For good results, leave a margin of at least 10 mm outside the cliché itself.
Fastening on the sleeve
Attaching the mounting tape to the sleeves is very close to attaching to a cylinder and many of the recommendations we have already mentioned are valid in this case as well. However, we must not forget that many of the sleeves are flexible and thin, so care must be taken during installation so as not to damage their structure.
It is recommended to follow the following instructions:
Always fasten the mounting strap while the sleeve is on the mounting table.
Use a minimum supply air pressure, as excessive pressure can affect the connection either between the sleeve surface and the strip, or between the mounting strip and the plate.
Remember that the material used to make the sleeve can always vary depending on the raw materials used, and for this reason you must be very careful when cleaning the surface.
Before you decide to use another type of sleeves, it is advisable to make a test run, as the type of surface is related to the strength of attachment and the characteristics of the mounting tape.
Fixing the cliché
Remove the protective liner from the mounting tape (if you think you can reuse it, save it) and place the plate in the correct position, taking care to achieve an accurate register. There are two key factors in achieving effective plate mounting:
The correct position of the plate on the mounting tape
Achieving perfect attachment
Good position is achieved by properly aligning the marks of the plate. There are different brands such as register crosses and micro-dots, but regardless of the type, make sure that you have aligned the plate correctly. Accurate positioning is essential, as otherwise the images will be reproduced with poor quality and without accurate color reproduction. If there is an overlap of the adhesive layers when attaching the mounting tape, it is good to make sure that the edges of the plate are not on the place of overlap.
Achieving a perfect fit is essential, otherwise the plate will move or lift during printing. Here it is recommended to press the plate as tightly as possible on the cylinder, making sure that you have achieved the best possible contact and adhesion. If this is done by hand, it is good to use a rubber roller to achieve a more even pressure, positioning and lamination.
Some mounting tapes with lower adhesion and fastening may not provide the required fastening strength immediately, especially in combination with rigid plates and / or small diameter printing cylinders. In such a configuration, the plate memory will naturally work against the connection and the plate, which is normally straight, will tend to separate from the cylinder or sleeve. To make it easier to achieve maximum adhesion in less time, you can use a thin wrapping foil to wrap around the bonded plate. This will significantly reduce the stress between the mounting tape - cylinder - plate surfaces and help to achieve the optimal degree of bonding.
Due to the peculiarities of the bonding process, valid for most photopolymers, when using larger plates, and especially when using mounting tapes with higher adhesion, it is recommended not to use the mounting tape for more than 4 weeks of continuous operation. If a larger circulation needs to be produced, it is recommended to remove the old mounting tape and use a new one. The same is true when working with thinner clichés due to the possibility of breakage or connection.
Cliché removal / Disassembly of photopolymer plates /
Even with a single use of the mounting tape, the plate must always be removed, after which the mounting tape must be removed from the cylinder or sleeve.
As the process involves the application of force, care must always be taken not to damage the printing plate. This should be a smooth and controlled action, given that over time, the strength of the adhesion has increased and the bonding between the individual surfaces is very strong.
Most often the dismantling process consists of the following:
First, carefully lift one of the corners, then gently lift the entire corner across the direction of the cylinder.
Then detach the plate from the mounting tape without squeezing or folding it. This would certainly have a detrimental effect on the condition of the plate. When using pressure-sensitive adhesives, it is recommended to separate at a 90-degree angle, which makes the operation as easy as possible.
Remember to clean the cliché carefully and thoroughly before taking it for storage. Be careful to completely remove any used coating on the back of the plate.
If the mounting tape will be used more than once, then it is recommended to protect its surface by re-wrapping it with its liner.
Disassembly of the double-sided adhesive mounting tape
Begin the process by slowly peeling off one end of the mounting tape from the cylinder surface. Follow the instructions for disassembling the plate. Take your time and pay attention to the process with a smooth motion. In this way you will not cause additional tearing and therefore an adhesive layer will remain on the surface of the cylinder. If you have used large clichés, then for easier removal you could cut the tape into sections to carefully remove one by one. Be careful not to damage the surface of the cylinder or sleeve.
If traces of adhesive still remain on the surface of the cylinder or sleeve, then they can be removed by scraping, but do not use sharp objects that could damage the surface of the cylinder or sleeve. It is important to remove each piece of adhesive. The whole process is facilitated as much as possible if clean and dry cylinders are used before installation.
And last but not least - make sure you clean your cylinders and sleeves well before storing in the warehouse. Pay attention to the removal of any ink residue.
Flexographic printing as a kind of advertising printing
Flexographic printing - another technology that we use to be of maximum benefit to our customers and to fulfill their wishes with quality. We have noticed that in addition to quality service, it is important to offer as many types of printing as possible so that we can offer a complete package of advertising printing services to you - our customers.
labels and packaging materials, bags, envelopes, packaging of all kinds and materials, nylon and polymeric materials, corrugated cardboard, paper, films, foils, cardboard, newspapers, multilayer bags, tissue, packaging for liquids and pastes and much much more
Like any printing technology, flexographic printing has its advantages and disadvantages. But the products that are produced thanks to flexographic printing are gaining more and more speed, gaining more and more popularity, namely: it is placed on all kinds of labels and packaging materials, bags, envelopes, packaging of all kinds and material, nylon and polymeric materials, corrugated cardboard, paper, films, foils, cardboard, labels, newspapers, multilayer bags, tissue, packaging for liquids and pastes and much much more. Well, what about the different types of bags, be they paper or polyethylene… This technology has no problem with almost any material from which bags are made.
Advantages of flexographic printing
Here are some benefits of flexographic printing that you may be curious to know. The main advantage is the ability to print on any substrate and especially on very thin and non-absorbent materials. A huge advantage for us as people who procure printing materials, in addition to offering the flexographic printing service itself, is that we can choose between different types of inks, each of which is suitable for this technology - both water-based inks and UV inks. Another advantage of flexographic printing is that it allows you to print packages of different sizes.