Large format printer

Wednesday, 17 January 2007

A large format printer or wide format printer is used for printing on wide format flexible substrates such as paper, card, vinyl and other polymers, and textiles. A printer is an essential computer peripheral that provides printing services to a computer user. Printers may include color and monochromatic (black-and-white) laser printers, inkjet printers, and plotters. In general, many printers and plotters operate using substantially similar or interchangeable technology and components, but are utilized in different applications. Most printers can only provide printouts of documents using print media, such as paper or transparencies, of commonly available, or standard, sizes. Due to other physical constraints, such printers would also only be able to handle print media not exceeding a maximum size. The proper printing of many graphic products, such as commercial artwork or signage, can require high quality wide format print work. Often, it is desired that the final multicolor graphic product be physically large, such as several feet wide by tens of feet long. Wide format printers are currently available can accommodate a printing sheet up to three feet wide and uses four full width (i.e., three feet wide) printheads, each interposing a different color donor sheet between the printhead and the printing sheet. By "large format" is typically meant graphic art, including photographic prints, printed on media widths ranging from 36 to 60 inches. In some printers, the media width may be varied, while in others, it may be fixed.

Inkjet printers, and thermal inkjet printers in particular, have come into widespread use in businesses and homes because of their low cost, high print quality, and color printing capability. Thermal ink-jet printers offer a low cost, high quality, and comparatively noise-free option to other types of printers commonly used with computers. An ink jet device is a printing device without impact that forms characters and other images by ejecting ink drops in a controllable way from a printhead. The printhead of an inkjet printer ejects ink through multiple nozzles in the form of minuscule drops which "fly" for a small space and strike a printing support. Different nozzles are used for different colors. Ink jet printers usually print within a range of 180 to 2400 or more dots per inch. The ink drops are dried upon the printing support soon after being deposited to form the desired printed images. The ink jet printing mechanisms may be used in different devices such as printers, plotters, facsimiles, and copiers. Large-format inkjet printers generally move a scanning carriage containing one or more printhead in a transverse or horizontal direction across a print medium, while incrementally advancing a print medium in a lengthwise or vertical direction in-between successive printing passes, or scans, of a reciprocating carriage. Large format color ink jet printers have a printhead carriage which is mounted for reciprocal movement on the printer in a direction orthogonal to the direction of movement of the paper or other medium on which printing is to take place through the printer. The printer carriage of a color printer typically has four removable piezoelectric or thermal ink jet printheads mounted thereon. In a thermal ink jet printhead the ink drops are ejected from individual nozzles by localized heating. Each of the nozzles has a small heating element. An electric current is made to pass through the element to heat it. This causes a tiny volume of ink to be heated and vaporized instantaneously by the heating element. Upon being vaporized, the ink is ejected through the nozzle. An exciter circuit is connected to individual heating elements to supply the energy impulses and to deposit in a controlled way ink drops from associated individual nozzles. These exciter circuits respond to character generators and other imaging circuits to activate selected nozzles of the printhead in order to form the desired images on the printing support. To print accurately and at higher resolutions, it is important to keep various parts of the inkjet printhead and carriage properly aligned. In particular, the printhead and carriage often experience a rotation about the z-axis perpendicular to the carriage direction due to imperfections in the carriage guide bars. In a large format printer, the printhead and carriage is typically guided by at least two such carriage guide bars. Large format ink jet printers are typically utilized to perform double-sided printing. When double-sided printing operations are conducted on cut sheets of print medium, i.e., sheets that have been packaged into various cut sizes, double-sided printing thereon may be effectuated with relative ease.

Wide format printers typically use one or more of a subset of the four subtractive primary colors: cyan, magenta, yellow, and black (CMYK) and rely upon color blending of these four ink colors to achieve accurate representations of desired colors. The printed image from an inkjet printer is made up of a grid-like pattern of potential dot locations, called picture elements or "pixels". A pixel generally refers to a coverage area that is defined by the incremental advance accuracy of the media (positioning resolution) of the media drive system along the X-axis, and the maximum number of colored dots the print-head can produce (marking resolution) along the Y-axis. Pixel density is often referred to as print resolution. Upon combining ink colors at a given pixel that a particular color combination can be formed by having multiple ink colors at a particular pixel location, either in a dot-on-dot or a dot-next-to-dot configuration. Large format printers are capable of using different types of ink without significant down time of the printer when changing or replacing the ink delivery system or components thereof. The different ink types may for convenience be broadly referred to as indoor ink and outdoor ink, meaning ink intend to be used for production of drawings, posters, and other printed material which may be displayed outdoors or indoors. Outdoor ink is pigment based, i.e. containing a plurality of discrete undissolved pigment particles suspended in a fluid carrier. In a wide format printer with a large ink consumption volume per print medium or in a network printer with a high operating efficiency, in particular, a large volume of ink is required. Large format printers generally use roll-type recording paper as the printing medium. Wide format printers using this roll-type paper are equipped with cutters for cutting paper after the paper is printed. Obviously, paper is a common material used in the roll-type recording medium, but non-paper materials, such as cloth and vinyl, are also widely used.

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