Impact Printer

 DOT MATRIX PRINTER

Dot matrix printing or impact matrix printing is a type of computer printing which uses a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like the print mechanism on a typewriter. However, unlike a typewriter or daisy wheel printer, letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced.

Pseudo-color

Several manufacturers implemented color dot-matrix impact printing through a multi-color ribbon. Color was achieved through a multi-pass composite printing process. During each pass, the print head struck a different section of the ribbon (one primary color). For a 4-color ribbon, each printed line of output required a total of 4 passes. In some color printers, such as the Apple ImageWriter II, the printer moved the ribbon relative to the fixed print head assembly. In other models, the print head was tilted against a stationary ribbon.

DAISY WHEEL PRINTER

Daisy wheel printing is an impact printing technology invented in 1969 by David S. Lee at Diablo Data Systems. It uses interchangeable pre-formed type elements, each with typically 96 glyphs, to generate high-quality output comparable to premium typewriters such as the IBM Selectric, but two to three times faster. Daisy wheel printing was used in electronic typewriters, word processors and computers from 1972. The daisy wheel is considered to be so named because of its resemblance to the daisy flower.
By 1980 daisy wheel printers had become the dominant technology for high-quality print. Dot-matrix impact or thermal printers were used where higher speed was required and poor print quality was acceptable. Both technologies were rapidly superseded for most purposes when dot-based printers—in particular laser printers—that could print any characters or graphics rather than being restricted to a limited character set became able to produce output of comparable quality. Daisy wheel technology is now found only in some electronic typewriters.
Thimble printers are closely related to daisy wheel printers, but instead of a flat wheel the petals were bent to form a cup-shaped "thimble" print element. Introduced by NEC in 1977 as their "Spinwriter" series, the replaceable thimbles each held 128 characters.


THIMBLE PRINTER

 A printer that uses a typing element known as thimble, which contains a full set of alphanumeric characters that are pressed through an ink ribbon onto the paper. A thimble printer acts much like many typewriters do. These printers were popular before inkjet and laser computer printers became popular; however, they are no longer used by computer users today.




CHAIN PRINTER

 

Chain printers (also known as train printers) placed the type on moving bars (a horizontally-moving chain). As with the drum printer, as the correct character passed by each column, a hammer was fired from behind the paper. Compared to drum printers, chain printers had the advantage that the type chain could usually be changed by the operator. A further advantage was that vertical registration of characters in a line was much improved over drum printers, which needed extremely precise hammer timing to achieve a reasonably straight line of print. By selecting chains that had a smaller character set (for example, just numbers and a few punctuation marks), the printer could print much faster than if the chain contained the entire upper- and lower-case alphabet, numbers, and all special symbols. This was because, with many more instances of the numbers appearing in the chain, the time spent waiting for the correct character to "pass by" was greatly reduced. Common letters and symbols would appear more often on the chain, according to the frequency analysis of the likely input. It was also possible to play primitive tunes on these printers by timing the nonsense of the printout to the sequence on the chain, a rather primitive piano. IBM was probably the best-known chain printer manufacturer and the IBM 1403 is probably the most famous example of a chain printer


BAND PRINTER

 
Band printers are a variation of chain printers, where a thin steel band is used instead of a chain, with the characters embossed on the band. Again, a selection of different bands were generally available with a different mix of characters so a character set best matched to the characters commonly printed could be chosen. Dataproducts was a well known manufacturer of band printers, with their B300, B600, and B1000 range, the model number representing the lines per minute rate of the printer. (The B300 was effectively a B600 with only half the number of hammers—one per two character positions. The hammer bank moved back and forth one character position, requiring two goes to print all characters on each line.)

DRUM PRINTER

In a typical drum printer design, a fixed font character set is engraved onto the periphery of a number of print wheels, the number matching the number of columns (letters in a line) the printer could print. The wheels, joined to form a large drum (cylinder), spin at high speed and paper and an inked ribbon is stepped (moved) past the print position. As the desired character for each column passes the print position, a hammer strikes the paper from the rear and presses the paper against the ribbon and the drum, causing the desired character to be recorded on the continuous paper. Because the drum carrying the letterforms (characters) remains in constant motion, the strike-and-retreat action of the hammers had to be very fast. Typically, they were driven by voice coils mounted on the moving part of the hammer.