Flexography, offset, silk screen, digital printing are the most common types of printing. In this article we will discuss the differences between them, define the advantages of each type and write their scope.
Consumers are rarely interested in their differences; in most cases the selection of the printing type depends on manager of printing company. In general, this approach is justified because the customer is not required to know the technical details; he is interested in the end result - the finished product. But often the choice of printing is not done according to the client's needs, but depending on the equipment owned by printing company. If the equipment for different types of printing is available, a situation may arise when the manager chooses a certain kind of print, but does not provide the necessary explanations. So in this article we will talk about the types of printing, their advantages and applications.
First, let's talk about flexographic printing. It arose relatively recently (the first time the term "flexography" appeared in 1952), but now this type of printing is dominating in world.
In flexography flexible polymer forms are used and the word "flexography" comes from the Latin flexibilis - «flexible» and Greek graphein - "write", "draw". The advantage of using these forms is the ability to use a wide range of materials, including materials with a rough texture (which are not possible to use offset printing). Thus flexo printing allows using various materials and face layers, such as thermal paper, metalized paper, polyethylene, polypropylene, specialized materials and more.
Also forms elasticity allows it to function as a deckle. Deckle in offset printing – is a special elastic layer, which is placed between the pressing plate and the cliché and provides uniform distribution of paints on a material for printing. This ensures high print quality. In addition, polymer form is characterized by high circulation - possibility of operation for a long time.
Flexographic printing belongs to high rotary printing method. Printing is high, because printing elements in the form are above of whitespace (see. figure).
Rotary printing means that the image is obtained through the rotation of a shaft (cylinder with a certain diameter). First a rubber shaft transfers the paint on the rotating anilox shaft. Anilox shaft has microscopic depressions, making the transfers of a dosed amount of paint to a polymer form, which is fixed to the forming shaft. On the diameter of the forming shaft the length of repeated fragment depends. In printing the shaft of different diameters are used and polymer forms are made according to their parameters. Accordingly non-standard size labels may cause an increase in the distance between them. Printing shaft presses material to form. Last shaft is magnetic. It has attached cutting form - that sets the shape of the finished product (labels). The figure shows a schematic process of flexographic printing type.
The big advantage of flexographic printing type is the ability to print from roll to roll at high speed and associate processes after printing in one line (eg, foil, laminating, die-cutting). Flexo has higher environmental friendliness, as it allows printing with environmentally friendly paints, there is no need in alcohol moisture. It provides high speed and print quality. But the production of polymeric and cutting forms (preprint services) requires certain costs, that is why this printing type is used mostly for large print runs.
The next type of printing, which we consider - is the offset printing. Offset printing refers to the flat printing methods when the printing and blank elements are on the same plane and differ only in physical and chemical properties - image is transferred by means of special separations based on aluminum alloys. Thus one of the advantages of offset printing is a relatively low cost of preprint services. Photo forms consists of lighted parts that attract water and not lighted parts that attract oily substances (paint), and vice versa repel water. So the paint is applied only to some – not lighted parts and we get the desired image. The figure shows a simplified model of offset printing. Continuous humidification is necessary to prevent paint drying on the form, so to offset important detail is a moisturizing shaft, which washes the form with water on each rotation.
The main advantage of offset printing type is the highest quality of raster images. In addition, this type of printing allows you to produce one form for several smaller orders with the same or proportionate editions (layout of different types is done on one plate) and combine them for printing. Offset printing provides the ability to print text with overlay colors (unlike flexography), gives sharper colors and transmission of shades. This type of printing is characterized by the highest image quality - you can get photographic printing.
Most offset printing are sheet-fed, i.e. products not produced in rolls but in sheets or pieces. Accordingly offset disadvantage is that the use of sheet printing inks enables printing only on paper materials.
Silk screen type of printing images is performed on the account of pushing paint with special tool (squeegee) through form (stencil). The form is made by forming a net with the non photochemical method. Previously one used silk net for this type of printing, and its name comes from it, but now polyamide (nylon), polyester or metal nets are also used. After printing photo polymeric layer is washed out of the net and it can be used again.
The big advantage of screen printing is that the paint is applied thickly (0.5 mm). So print has volume (is palpable), paint is bright, saturated, with high cover properties, thus avoiding transparency effect for printing on transparent films. Therefore screen printing is visually quite different from the other because of the thick layer of paint and high quality of printing.
Possible is printing directly on the surface of the print and putting paint on the intermediate carrier, so that image has to be transferred to another surface (decal). In this way, for example, are made "the talking flowers " - printing on flower petals is transferred of the special sheets, pre-printed with silk screen type.
In screen printing one can use a wide range of special paints and materials, large areas print is available. This type of printing is also used for printing images on surfaces, such as wood, metal, leather, fabric, plastic, glass, ceramic and other. Moreover, the circulation may be minimal, because the cost of preprint services is low. Often with this type of printing are made business cards, stickers or labels of a small edition, packaging print and more.
Digital printing is performed by directly applying paint in special printer after reading electronic media. So big advantage of digital printing is the lack of preparation for preprint services (printing form production), which saves time and money, and also this type of print allows to produce minimal labels circulation (from 1 pieces). Printing digital equipment allows printing full-color labels in paper or polypropylene materials. Print quality in special printers is not worse than flekso, printing is fully computerized, rather quick and irreplaceable when you need to quickly get the finished product or test label design.
Printers are inkjet and laser. To print on an inkjet printer one must use liquid ink. The disadvantage of such labels is that it is not resistant to friction or moisture. Therefore, to protect the label lamination is required. Laser printing is carried out by painting powders that are seared to the material. The label made on a laser printer is not exposed to moisture, is more resistant in using. But the disadvantage of both varieties is that labels can burn out in the sun. In this case it is necessary to choose inkjet printing, but with solvent or UV inks.
Another type of digital printing is a printing using thermal printers or thermal transfer printers in a place of consumption. The customer can buy standard rolls of clean labels or labels with the previous print and use them as needed. The advantage of this type of printing is that you need not wait for the production of labels by printing company and can quickly print them in a place where it is needed. Digital printing also allows you to make changes at any time, which is impossible for other types of printing, where the print forms are used. For example, information about the date of packaging or weight of the goods is not sustainable and it is usually printed on printers or electronic scales. Example of digital printing can be seen on electronic scales in the supermarket – labels with the previous print are inserted in scale, where after each weighing variable information is printed (weight, time, product names, etc.).