Dot matrix printer

A dot matrix printer is a computer printer that fails when printing a series of driven single needles on a ribbon and thereby brings the other side of the ribbon each selectively with the paper in contact. A printed character consists of a large number of such color points each.

Dot matrix printers were widespread in the 1980s in the home and small office area (SOHO ), and were later replaced by inkjet and laser printers, but are still occasionally encountered ( doctors' offices, ticket printer). Overall, they are because of their high noise and low resolution as out of date, but (for example, punches and delivery notes in the transport and logistics sector ) still used as a niche product and also still in production.

The dot matrix printer was developed in 1968 by the Japanese company OKI and OKI called Wiredot. 2013 received OKI purpose of the Information Processing Society of Japan ( IPSJ short ) the predicate " technologically valuable heritage "

Classification

A dot matrix printer as part of the daisy wheel printer to the impact printers ( English impact, " Impact, Impact " ), because during the printing process of physical pressure is applied. It can be produced including punches. Since the printed image of a matrix is composed of points, it counts, like most other types of printers, the dot matrix printers.

The technique

When printing, individually controlled needles beat (7, 8, 9, 12, 18, 24 or 48 pieces ) on a ribbon between the paper and print head, whereby the image points are mapped, which make up the signs. The higher the number of needles, the more closely the points can be set, and the better the image. With this technology you can reach depending on type and print quality, print speed of up to 1,000 characters per second ( CPS also for Characters per second). However, the quality of the copies is reduced with a higher number of needles. Therefore, 9- pin printers are for applications with up to 6 carbon copies often used.

Modes

Draft

In draft mode (English draft mode ), the print head moving at high speed. The needles can be controller in a coarse matrix row by row. The typeface is thus only useful to read. Often in this case a font with a height of only 8 × 9 points is used, even if the printer over 24 or even more needles has. However, the speed of the expression is thus very high. Typical are 200-400 cps. Some device models have an additional high-speed draft mode, which is even faster, but in turn also provides an even worse print result. In many cases, however, the compromise between speed and legibility is acceptable.

NLQ

In NLQ mode (Near Letter Quality to German almost correspondence quality) of the print head is moved at half speed in order to achieve a doubling of horizontal resolution with the same stop frequency of the needles. At the end of the line, a line feed is to ½ needle diameter and the line is printed again. Thus, the interstices of the printed image are now also filled in ( vertical resolution). Expression is required compared to the draft mode, up to four times more time. A possible optimization provides the bi-directional printing process here.

LQ

In the LQ mode ( Letter Quality ) corresponds to the printed image produced by a classical method page, just " letter quality ". This was previously only typewriters, whose typeface had also improved significantly by the use of carbon bands in comparison to the ink-impregnated fabric tape. Today, every commercial laser printer print quality reaches such. With a dot matrix printer that quality is achieved by a very high horizontal resolution as well as very fast and precise driving the needles.

Simplified one can say: the higher the print speed, the less time is available for a compressed character is available and the lower the printing quality.

Number of needles

The first needle printers could only work with eight needles. Hereby the pressure of letters with descenders (eg "g " or " j" ) was limited. There the standard character sets were used from the computer terminals in the printer software. This had a 8 × 8 matrix. Also underlined text was a problem. It was not until the ninth needle true descenders were possible.

From this developed the so-called 9- pin printer and the 24 - pin printer. Up to twelve needles are located in a single vertical row. A printing head with needles 18 has two staggered rows each of nine needles, a printer with 24 pins has twelve needles in a row. The offset of the second row doubles the vertical resolution.

Color and graphics

Dot matrix printers can print both monochrome and color depending on the type of text and graphics. The ribbon is this, from the colors cyan (cyan ), purple ( magenta ), yellow ( yellow) and black (key plate, dt " key plate " ) ( CMYK, see also: subtractive color mixing), which coexist in tracks on the tape are arranged. The printer can select each color by vertical movement of the ribbon on the appropriate track. Showing a matrix point with a specific color, the needle must be driven in accordance with the succession respective color band selection at the same point. Of the primary colors mixing different shades can only be displayed using a diffusion pattern. Because of the technology due to the lack of resolution and the insufficient repeatability achieve dot matrix printer using this method by far not the color fidelity of an inkjet printer.

Today's use

While Typenraddrucker hardly be used, you will find the equally reliable and robust dot matrix printers still frequent in companies, doctors' offices and in banks as savings banks in the cash shop. Dot matrix printers are also used in Fahrscheinentwertern, department store checkouts and parking machines because they require little maintenance and are resistant printouts. But also very common thermal printers are used for these applications, since in these devices, the Consumables Ribbon is no longer necessary. Furthermore, dot matrix printers used for their robustness in dusty workshops or on construction sites.

By far the most common application area even today are so-called protocol printer in large companies or in systems with high security requirements. The individual protocols eg switching states in switchgear are not only digitally secured, but also against subsequent modification immune as an immediate expression.

Advantages:

  • Print with copies available
  • Any type of printable paper
  • Low consumption costs ( ribbon)
  • Maintenance
  • Indelible
  • Can handle continuous paper
  • Waterproof expression
  • High life
  • Line by line pressure possible

Cons:

  • Noise pollution
  • Small print speed
  • Changing print quality ( the state of the ribbon -dependent)
  • Characteristic rasterized "Computer" print image
  • Poor color reproduction
  • Not all characters and graphics
  • Heat of the print head in continuous operation
  • Using special software "tapping"
590862
de