The choice of print technology has a great effect on the cost of the printer and cost of operation, speed, quality and permanence of documents, and noise. Some printer technologies do not work with certain types of physical media, such as
carbon paper or
transparencies. A second aspect of printer technology that is often forgotten is resistance to alteration: liquid
ink, such as from an inkjet head or fabric ribbon, becomes absorbed by the paper fibers, so documents printed with liquid ink are more difficult to alter than documents printed with
toner or solid inks, which do not penetrate below the paper surface. Cheques can be printed with liquid ink or on special cheque paper with toner anchorage so that alterations may be detected. The machine-readable lower portion of a cheque must be printed using
MICR toner or ink. Banks and other clearing houses employ automation equipment that relies on the
magnetic flux from these specially printed characters to function properly.
Modern print technology The following
printing technologies are routinely found in modern printers:
Laser printers and other toner-based printers A
laser printer rapidly produces high quality text and graphics. As with digital
photocopiers and multifunction printers (MFPs), laser printers employ a
xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a
laser beam across the printer's
photoreceptor. Another toner-based printer is the
LED printer which uses an array of
LEDs instead of a
laser to cause toner
adhesion to the print drum.
Liquid inkjet printers Inkjet printers operate by propelling variably sized droplets of liquid ink onto almost any sized page. They are the most common type of computer printer used by consumers.
Solid ink printers Solid ink printers, also known as phase-change ink or hot-melt ink printers, are a type of
thermal transfer printer, graphics sheet printer or 3D printer . They use solid sticks, crayons, pearls or granular ink materials. Common inks are
CMYK-colored ink, similar in consistency to candle wax, which are melted and fed into a piezo crystal operated print-head. A Thermal transfer printhead jets the liquid ink on a rotating, oil coated drum. The paper then passes over the print drum, at which time the image is immediately transferred, or transfixed, to the page. Solid ink printers are most commonly used as color office printers and are excellent at printing on transparencies and other non-porous media. Solid ink is also called phase-change or hot-melt ink and was first used by Data Products and Howtek, Inc., in 1984. Solid ink printers can produce excellent results with text and images. Some solid ink printers have evolved to print 3D models, for example, Visual Impact Corporation of Windham, NH was started by retired Howtek employee, Richard Helinski whose 3D patents US4721635 and then US5136515 was licensed to Sanders Prototype, Inc., later named Solidscape, Inc. Acquisition and operating costs are similar to
laser printers. Drawbacks of the technology include high
energy consumption and long warm-up times from a cold state. Also, some users complain that the resulting prints are difficult to write on, as the wax tends to repel inks from
pens, and are difficult to feed through
automatic document feeders, but these traits have been significantly reduced in later models. This type of thermal transfer printer is only available from one manufacturer,
Xerox, manufactured as part of their
Xerox Phaser office printer line. Previously,
solid ink printers were manufactured by
Tektronix, but Tektronix sold the printing business to Xerox in 2001.
Dye-sublimation printers A dye-sublimation printer (or dye-sub printer) is a printer that employs a printing process that uses heat to transfer dye to a medium such as a
plastic card, paper, or
canvas. The process is usually to lay one color at a time using a ribbon that has color panels. Dye-sub printers are intended primarily for high-quality color applications, including color photography; and are less well-suited for text. While once the province of high-end print shops, dye-sublimation printers are now increasingly used as dedicated consumer photo printers.
Thermal printers Thermal printers work by selectively heating regions of special heat-sensitive paper. Monochrome thermal printers are used in cash registers,
ATMs,
gasoline dispensers and some older inexpensive fax machines. Colors can be achieved with special papers and different temperatures and heating rates for different colors; these colored sheets are not required in black-and-white output. One example is
Zink (a portmanteau of "zero ink").
Obsolete and special-purpose printing technologies MX-80, a popular model of dot-matrix printer in use for many years The following technologies are either obsolete, or limited to special applications though most were, at one time, in widespread use.
Impact printers Impact printers rely on a forcible impact to transfer ink to the media. The impact printer uses a print head that either hits the surface of the ink ribbon, pressing the ink ribbon against the paper (similar to the action of a
typewriter), or, less commonly, hits the back of the paper, pressing the paper against the ink ribbon (the
IBM 1403 for example). All but the
dot matrix printer rely on the use of
fully formed characters,
letterforms that represent each of the characters that the printer was capable of printing. In addition, most of these printers were limited to monochrome, or sometimes two-color, printing in a single typeface at one time, although
bolding and
underlining of text could be done by "overstriking", that is, printing two or more impressions either in the same character position or slightly offset. Impact printers varieties include typewriter-derived printers, teletypewriter-derived printers, daisywheel printers, dot matrix printers, and line printers. Dot-matrix printers remain in common use in businesses where multi-part forms are printed.
An overview of impact printing contains a detailed description of many of the technologies used.
Typewriter-derived printers Several different computer printers were simply computer-controllable versions of existing electric typewriters. The
Friden Flexowriter and
IBM Selectric-based printers were the most-common examples. The Flexowriter printed with a conventional typebar mechanism while the Selectric used IBM's well-known "golf ball" printing mechanism. In either case, the letter form then struck a ribbon which was pressed against the paper, printing one character at a time. The maximum speed of the Selectric printer (the faster of the two) was 15.5 characters per second.
Teletypewriter-derived printers The common
teleprinter could easily be interfaced with the computer and became very popular except for those computers manufactured by
IBM. Some models used a "typebox" that was positioned, in the X- and Y-axes, by a mechanism, and the selected letter form was struck by a hammer. Others used a type cylinder in a similar way as the Selectric typewriters used their type ball. In either case, the letter form then struck a ribbon to print the letterform. Most teleprinters operated at ten characters per second although a few achieved 15 CPS.
Daisy wheel printers Daisy wheel printers operate in much the same fashion as a
typewriter. A hammer strikes a wheel with petals, the "daisy wheel", each petal containing a letter form at its tip. The letter form strikes a ribbon of
ink, depositing the ink on the page and thus printing a character. By rotating the daisy wheel, different characters are selected for printing. These printers were also referred to as
letter-quality printers because they could produce text which was as clear and crisp as a typewriter. The fastest letter-quality printers printed at 30 characters per second.
Dot-matrix printers The term
dot matrix printer is used for impact printers that use a matrix of small
pins to transfer ink to the page. The advantage of dot matrix over other impact printers is that they can produce
graphical images in addition to text; however the text is generally of poorer quality than impact printers that use letterforms (
type). Dot-matrix printers can be broadly divided into two major classes: • Ballistic wire printers •
Stored energy printers Dot matrix printers can either be
character-based or line-based (that is, a single horizontal series of pixels across the page), referring to the configuration of the print head. In the 1970s and '80s, dot matrix printers were one of the more common types of printers used for general use, such as for home and small office use. Such printers normally had either 9 or 24 pins on the print head (early 7 pin printers also existed, which did not print
descenders). There was a period during the early home computer era when a range of printers were manufactured under many brands such as the
Commodore VIC-1525 using the
Seikosha Uni-Hammer system. This used a single solenoid with an oblique striker that would be actuated 7 times for each column of 7 vertical pixels while the head was moving at a constant speed. The angle of the striker would align the dots vertically even though the head had moved one dot spacing in the time. The vertical dot position was controlled by a synchronized longitudinally ribbed platen behind the paper that rotated rapidly with a rib moving vertically seven dot spacings in the time it took to print one pixel column. 24-pin print heads were able to print at a higher quality and started to offer additional type styles and were marketed as
Near Letter Quality by some vendors. Once the price of inkjet printers dropped to the point where they were competitive with dot matrix printers, dot matrix printers began to fall out of favour for general use. Some dot matrix printers, such as the NEC P6300, can be upgraded to print in color. This is achieved through the use of a four-color ribbon mounted on a mechanism (provided in an upgrade kit that replaces the standard black ribbon mechanism after installation) that raises and lowers the ribbons as needed. Color graphics are generally printed in four passes at standard resolution, thus slowing down printing considerably. As a result, color graphics can take up to four times longer to print than standard monochrome graphics, or up to 8–16 times as long at high resolution mode. Dot matrix printers are still commonly used in low-cost, low-quality applications such as
cash registers, or in demanding, very high volume applications like
invoice printing. Impact printing, unlike laser printing, allows the pressure of the print head to be applied to a stack of two or more forms to print
multi-part documents such as sales invoices and
credit card receipts using
continuous stationery with
carbonless copy paper. It also has security advantages as ink impressed into a paper matrix by force is harder to erase invisibly. Dot-matrix printers were being superseded even as receipt printers after the end of the twentieth century.
Line printers Line printers print an entire line of text at a time. Four principal designs exist. •
Drum printers, where a horizontally mounted rotating drum carries the entire character set of the printer repeated in each printable character position. The
IBM 1132 printer is an example of a drum printer. Drum printers are also found in adding machines and other numeric printers (POS), the dimensions are compact as only a dozen characters need to be supported. •
Chain or train printers, where the character set is arranged multiple times around a linked chain or a set of character slugs in a track traveling horizontally past the print line. The
IBM 1403 is perhaps the most popular and comes in both chain and train varieties. The
band printer is a later variant where the characters are embossed on a flexible steel band. The LP27 from Digital Equipment Corporation is a band printer. •
Bar printers, where the character set is attached to a solid bar that moves horizontally along the print line, such as the
IBM 1443. • A fourth design, used mainly on very early printers such as the IBM 402, features independent type bars, one for each printable position. Each bar contains the character set to be printed. The bars move vertically to position the character to be printed in front of the print hammer. In each case, to print a line, precisely timed hammers strike against the back of the paper at the exact moment that the correct character to be printed is passing in front of the paper. The paper presses forward against a ribbon which then presses against the character form and the impression of the character form is printed onto the paper. Each system could have slight timing issues, which could cause minor misalignment of the resulting printed characters. For drum or typebar printers, this appeared as vertical misalignment, with characters being printed slightly above or below the rest of the line. In chain or bar printers, the misalignment was horizontal, with printed characters being crowded closer together or farther apart. This was much less noticeable to human vision than vertical misalignment, where characters seemed to bounce up and down in the line, so they were considered as higher quality print. •
Comb printers, also called
line matrix printers, represent the fifth major design. These printers are a hybrid of
dot matrix printing and line printing. In these printers, a comb of hammers prints a portion of a row of pixels at one time, such as every eighth pixel. By shifting the comb back and forth slightly, the entire pixel row can be printed, continuing the example, in just eight cycles. The paper then advances, and the next pixel row is printed. Because far less motion is involved than in a conventional dot matrix printer, these printers are very fast compared to dot matrix printers and are competitive in speed with formed-character line printers while also being able to print dot matrix graphics. The
Printronix P7000 series of line matrix printers are still manufactured as of 2013. Line printers are the fastest of all impact printers and are used for bulk printing in large computer centres. A line printer can print at 1100 lines per minute or faster, frequently printing pages more rapidly than many current laser printers. On the other hand, the mechanical components of line printers operate with tight tolerances and require regular
preventive maintenance (PM) to produce a top quality print. They are virtually never used with
personal computers and have now been replaced by high-speed
laser printers. The legacy of line printers lives on in many
operating systems, which use the abbreviations "lp", "lpr", or "LPT" to refer to printers.
Liquid ink electrostatic printers Liquid ink electrostatic printers use a chemical coated paper, which is charged by the print head according to the image of the document. The paper is passed near a pool of liquid ink with the opposite charge. The charged areas of the paper attract the ink and thus form the image. This process was developed from the process of
electrostatic copying. Color reproduction is very accurate, and because there is no heating the scale distortion is less than ±0.1%. (All laser printers have an accuracy of ±1%.) Worldwide, most survey offices used this printer before color inkjet plotters become popular. Liquid ink electrostatic printers were mostly available in width and also 6 color printing. These were also used to print large billboards. It was first introduced by Versatec, which was later bought by
Xerox.
3M also used to make these printers.
Plotters Pen-based
plotters were an alternate printing technology once common in engineering and architectural firms. Pen-based plotters rely on contact with the paper (but not impact, per se) and special purpose pens that are mechanically run over the paper to create text and images. Since the pens output continuous lines, they were able to produce technical drawings of higher resolution than was achievable with dot-matrix technology. Some plotters used roll-fed paper, and therefore had a minimal restriction on the size of the output in one dimension. These plotters were capable of producing quite sizable drawings.
Other printers QL-500 label printer A number of other sorts of printers are important for historical reasons, or for special purpose uses. •
Digital minilab (
photographic paper) •
Electrolytic printers •
Spark printer • Barcode printer multiple technologies, including:
thermal printing,
inkjet printing, and
laser printing barcodes • Label printer •
Wide-format printer • Billboard / sign paint spray printers • Laser etching (product packaging) industrial printers • Microsphere (special paper) == Attributes ==