Commercial Printing

Commercial Printing

There are various process meant for commercial printing which are used as needed for the application the following are the various processes for the commercial printing.

Relief Process

Letterpress

This is the oldest of the major commercial printing processes and is not very commonly used anymore. This process uses plates which were first made of wood and later they were made of metal. The print image on the plate is raised and when inked, the plate is placed in contact with a platen that holds the paper and the image is transferred.

Flexography

Flexography is most commonly seen in the packaging industry as it provides the flexibility to print on a wide variety of surfaces. The process is very similar to Letterpress except for the fact that the plate used is made of a flexible material such as rubber or plastic.

Intaglio Process

Gravure

Gravure is used for a variety of purposes such as magazines, catalogs, packaging, tablecloths, wallpaper, etc. in that this print image is recessed through an engraving/etching process and uses a metal cylinder as the image carrier. When the substrate comes into contact with the cylinder, ink is transferred from the recessed cells on the cylinder to the substrate.

Screen Process

Serigraphic Printing (Silk Screen):
In this process a squeegee forces ink through a mesh or screen. The non-image areas are blocked so that the ink does not pass through. Screens can be made of a variety of materials including polyester, nylon or metal. This is the only printing process in which the ink passes through the image carrier. Common uses include T-shirts, mugs, mouse pads, etc.

Plano graphic Process

Lithography

This is the most commonly used commercial printing process and also the most complicated. It is used to create magazines, books, newspapers, reports, brochures and much more. This type of printing is done on an offset press that uses an indirect printing process. This means that the image carrier and the substrate do not come into contact with each other. These presses can be either sheet fed or web fed in nature. Sheet fed presses send individual sheets through the press while web fed presses use a very large roll of paper.

The first step is to create a plate which is typically made of aluminum, polyester or paper depending on how long the run is and how durable the plate needs to be for archiving. Traditionally, plates are created through a time consuming prepress process that involves creating CMYK color separations and then developing large film negatives from which the plates are made. CTP improves the time and effort involved considerably by using a device that accepts electronic files and then images the plates, removing the necessity for film development.

Once the plate is created, it is wrapped around the plate cylinder and water is applied to the non-image areas and ink is applied to the image areas. The plate cylinder then comes into contact with the blanket cylinder and the image is transferred to it. The blanket cylinder is has a rubber blanket wrapped around it that picks up the image from the plate cylinder. The substrate passes between the blanket cylinder and the impression cylinder where the image is passed to the substrate. Commercial presses are very fast and have very high quality output.

Digital Printing

Digital printing is typically used for shorter run paper based jobs such as reports, newsletters, books, brochures, etc. Digital printing has some distinct advantages over the other printing processes. The other processes are incapable of producing variable data which is the ability to create sections of a job that vary from page to page. This is possible because, unlike the other processes, a digital printer’s image carrier is imaged on a page by page basis. This can't be done on an offset press (for example) where permanent plates are fixed to a drum. Digital printing comparatively has very little prepress time and provides the ability to easily edit a job. Digital Printing's weaknesses are it's comparative lack of speed, resolution and color reproduction, however, technological advances are improving these factors all of the time.

Digital printing uses a positive electric charge on the image areas of a drum while non-image areas possess a negative charge. The drum is passed by negatively charged toner particles that are attracted to the positively charged areas of the drum. The paper passes across the drum and the toner is transferred. From here, the paper passes through a fusing unit that uses heat and pressure to bond the toner to the paper. Digital printing cuts down on much of the prepress labor involved with using an offset press and are very popular for shorter run jobs where the speed and quality of a press is not needed.

Commercial Printing