Gravure Printing.

The distinctive feature of gravure printing technology is the fact that image elements are engraved into the surface of the cylinder. The non-image areas are at constant level. The ink used for gravure printing has a low viscosity.

Gravure printing is used for very long print runs. Weekly magazines of general interest and mail order catalogs are the main products produced by means of gravure printing. Another major area is in the printing of packaging.

With gravure printing, straight printing and perfecting is done in systems where the first side of the web is printed in multicolor and then on the opposite side.

Gravure printing technology has three types of platemaking: etching, electromechanical engraving and laser engraving.

Printing units consist of inking unit, gravure cylinder, impression roller and blade.

Every conventional printing process has two-roller system consisting of impression cylinder and gravure cylinder. The paper contacts with the inked surface of gravure cylinder, so the ink is transferred from the etched gravure cylinder onto the paper.

There are some advantages of gravure printing technology:

-high-quality and consistent reproduction of the finest photographic details in even the smallest of images on thin.

-flexible printing material

-large number of multi-ups on one gravure cylinder

-printing on both sides of the web can be carried out easily in the pass.

But gravure printing technology has some disadvantages:

-very long print runs

-cylinder must be prepared in a costly mechanical and galvanical process.

Screen Printing.

Screen printing is a process which means that during printing process the ink passes through the screen and onto the substrate.

Printing unit consists of the frame(2), printing plate (combination of screen and stencil), blade, squeegee, paper, base plate (print body). There are three types of screen presses: flat-bed, rotary screen printing, cylinder screen printing.

Printing can be done on paper, textiles, ceramics, plastics and glasses. The variety of using inks depends on a material. The stencil is fastened onto the surface on which printing is to be done and the ink passes through the stencil apertures where it is spreaded by a squeegee. The stencil is the carrier of the printed information. The advantage of this technology is that the use of stencils enables a fast application of information in the form of text and symbols on various materials. Stencil printing has one general disadvantage namely that all parts of the stencil must be connected to each other. But this disadvantage doesn’t occur with screen printing.

The production of screen printing is large-format posters, printing on CDs, clothes, shopping bags, ceramics and so on.

Letterpress

This is the method of printing Gutenberg invented in 1440 and since then it has been used for job and commercial printing.

It is a relief method of printing that can print from cast metal type, molded duplicate plates or photopolymer plates on which the image or printing areas are raised above the nonprinting areas.

Viscous oil-base and UV inks are used. The ink rollers come in contact with the raised areas only, and the inked image is transferred directly to the paper. Four types of presses were used: platen, flatbed cylinder, rotary and belt. Letterpress is making a comeback in specialty printing using photopolymer plates and UV inks on narrow web presses.

Printing unit consists of roller inking unit with 3 ink form rollers, plate cylinder with hard printing plate and impression cylinder with elastic packaging.

The fundamental disadvantages of letterpress printing compared to offset printing are the expensive printing plate, the costly make-ready of the printing plate, the limited print quality and the limit of production speed.

Letterpress is still used to print forms, labels, lottery tickets, security papers, telephone books, and paperbacks.

Flexography

Flexography is a form of rotary web relief printing like letterpress but using flexible rubber or resilient photopolymer relief plates, and fast-drying low viscosity solvent, water-based, or UV inks feb from anilox inking system.

Printing plates are either flat and fastened onto the plate cylinder with adhesive or double-sided adhesive film, or they are produced in cylindrical form (e. g., sleeve technology).

Printing units usually consist of an inking unit, a plate cylinder with soft printing plate and an impression cylinder (hard).

Products of the flexography are books, newspapers, inserts, publications and packaging printing markets.

Flexographic presses are web-fed machines of three types:

(1) stack type;

(2) central impression cylinder;

(3) inline;

The Advantages of this method of printing are:

Flexography is the least expensive and simplest of the printing processes used for decorating and packaging printing.

Printing can be done on materials with very rough surfaces and even on fabrics.

The disadvantage is that the print quality that can be achieved in flexography is lower compared to offset printing.

Digital printing.

Non-impact printing technologies (NIP technologies) are technologies that do not require a solid printing plate with a fixed image and that can basically produce successive pages with different printed images.

A laser sends information to an intermediate carrier, a drum with a photoconductive coating, without impact (non-impact) in the traditional sense. The latent (nonvisible), charged image stored on this drum is inked with toner and then transferred to the paper. There is contact between the inked (toned) information carrier and the paper during printing, but the information is not transferred by impact. This process is considered as non-impact printing.

In NIP technologies there is no printing plate carrying permanent information. This has given rise to new, efficient ways of producing printed media, such as print on demand, personalization, book on demand, and so forth.

Market segments: short-run jobs, proofing applications, personalization, office and DTP applications.

There is a number of non-impact printing technologies. They are named after physical or chemical principle they are based upon (electrophotography, ionography, Magnetography, ink jet, Thermography, electography, Photography, «X»-Graphy ). «X»-Graphy:«Direct imaging/inductive printing*, «TonerJet», «Elcography», «Zurography».

Toners: powder or liquid.

NIP technologies can be sheet-fed or web-fed printing.

Magnetography is a variant of the non-impact printing technologies. The magnetic fields attract ferrous magnetic powder toner particles via a special inking unit. In principle the magnetography imaging drum is capable of storing a magnetic pattern generated on the surface.

Disadvantage: circumference of the imaging cylinder is generally smaller than the image-length; magnetic pattern is not sufficiently stable to ensure constant print quality.

The magnetographical imaging occurs via an imaging system with micro-magnet heads. Then the magnetic toner is applied, which is fused in order to attain a permanent image.

The materials on the imaging cylinder surface and the fused toner have to be conditioned so that they are suitable for offset printing. The image is transferred via the blanket cylinder onto the paper using dampening solution and inking up with offset inks.

Print finishing process.

Finishing (postpress) is a segment of the print production flow in which the printed product is given its requested features of form and functions. The end products produced in the finishing process are characterized by the design (shape) and the functions that are determined by the information content.

The following products are produced in the finishing sector: Individual sheets(trimmed sheets, cuttings);Folded sheets; Newspapers; Booklets; Brochures; Hardcovers; Assortment of sheets; Packing material.

The following operations are carried out in the process sections:

1) Cutting and die-cutting:

The main applications are: Paper cutting, Cutting webs, Trimming, Cutting case material to size. Die-cutting is a process in which materials are cut in a specific pattern (perforating)

2) Folding: Folding machines are primarily designed according to two principles of function: the buckle fold principle; the knife fold principle (right-angle fold principle)

3) Forwarding

4) Assembling into books

5) Blocks binding:

Blocks binding is the production of a temporary or permanent connection of the collated book block by positive, non-positive, or bond jointing processes (fixing elements or adhesives).

Different methods of binding exist. They are: thread-stitching; perfect binding; thread-sealing; wire-stitching.

6) Trimming:

Materials and partial products to be processed are:

bound book blocks;

multi - layer brochures;

back - stitched brochures;

leaf assemblies.

7) Edge treatments on books and brochures:

They serve to improve the aesthetic appearance of the overall product. Processes are:

Edge staining/coloring; Attaching a bookmark; Rounding spine; Adding headbands.

8) Case making: The purpose of covers is: protection of the block; to describe the contents; as an advertising medium; as an object of art.

9) Book finishing: The process steps are: joining of book block and cover to a fixed binding; joining of finished supplement products into cases, blocks, or books; inserting enclosures; attaching book jackets.

10) Packaging: Packages have three basic functions: Protective function, Logistics function, Information function.

Mailing and distribution are also important postpress operations.

Binding.

Binding — is a combination of operations required to convert printed sheets or webs into books, magazines, catalogs, folders.

There are four methods of binding: thread-stitching; perfect binding; thread-sealing; wire-stitching.

Thread-stitching of a book block comprises the following elementary processes: Thread-stitching, Gluing block spines, Gauzing blocks, Back-stripping blocks.

Perfect binding is the domination binding process in industrial book and brochure production today.

Perfect binding systems have the following characteristic elements: endpaper feeder stations, jogging station, transport system, spine processing station, gluing unit, lining station, cover scoring and feed station, cover aligning and pressing station, dryer, delivery.

Thread-sealing – a process that is more economic than thread-stitching and also more reliable and more user friendly than perfect binding.

This process has two stages: the binding process of folded sheets to one another with textile threads during folding; the binding process of folded sheets to the block through block linings after gathering.

The dominating process is that of the wire-stitching of single-layer brochures, for which two or more staples are inserted into the back fold.