What is Dot Matrix Printer?

What is Dot Matrix Printer?

Type of computer printer that uses tiny hammers in its print head to strike pins over an inked ribbon to form characters or images on paper, and is used mainly for multi-part forms. For general printing, dot matrix printers have largely been replaced by cheaper and faster non-impact printers such as ink jets and lasers which also produce output of far better quality (resolution). Long after the arrival of laser printers, dot matrix printers have been used to print continuous multi-part forms and mailing labels. The tractor feed contains a sprocket that grabs the perforated holes at both sides of the form and pulls it through uniformly. Dot matrix printers print columns of dots in a serial fashion. The more dot hammers (pins), the better looking the printed results. The print head can get very hot. Unlike laser and inkjet printers, which can create characters of any size, dot matrix printers have limited options.

Hammers Hit the Ribbon

The dot matrix printer uses one or two columns of dot hammers that are moved across the paper. The hammers rapidly press the ribbon into the paper, which causes the ink to be deposited. The more hammers, the higher the resolution. For example, 9-pin heads produce draft quality text, while 24-pin heads produce typewriter quality output. Speeds range from 200 to 400 characters per second, which is approximately 90 to 180 lines per minute (lpm). 

Dot Matrix Printing Works

Ink is administered to the paper in dots via a series of tiny metal pins which are driven forward through an ink-soaked ribbon by the power of electromagnets or solenoids. The pins are traditionally located on a moving mechanism called the print head which will move from left to right to generate text. Up to 48 pins may be moving simultaneously to speed up the process of creating the printed output. The pattern of the administration of the ink is determined by the computer, re-creating the on-screen text in a series of dots. Traditionally very durable machines, dot matrix printers were widely favored between the 1970 and 1990 due to their reliability and long life.

History of Dot Matrix Printing

First introduced onto the market by OKI in 1968, the original machine was known as the OKI Wire-dot. This was then improved upon by the Digital Equipment Corporation of Maynard, Massachusetts who created the DEC LA30 in 1970, which was capable of printing 30 characters every second. Four years later, the LA30 was followed by the LA36 which achieved far greater commercial success – becoming a standard for dot matrix technology in the process until 1979 when Epson got involved. The Epson MX-80 was the all-important ground-breaking model which really sparked interest in home printers. Affordable and capable of top print quality, the MX-80 proved to be hugely popular at a time when the personal computer market was really starting to blossom. Two years later Epson released the EPROM kit which was designed to allow MX-80 printers to print graphics – something which was previously unbelievable for affordable home printers. Over the years, the quality of the text, speed of the output and overall performance continued to improve – remaining popular throughout the 80s and the early 90s.

Advantages and disadvantages

Dot matrix printers, like any impact printer, can print on multi-part stationery or make carbon-copies. Impact printers have one of the lowest printing costs per page. low printing cost is more important than quality. The ink ribbon also does not easily dry out, including both the ribbon stored in the casing as well as the portion that is stretched in front of the print head.

   Impact printers create noise when the pins or typeface strike the ribbon to the paper. They can only print lower-resolution graphics, with limited color performance, limited quality, and lower speeds compared to non-impact printers. they support fan-fold paper with tractor holes well, single-sheet paper may have to be wound in and aligned by hand, which is relatively time-consuming, or a sheet feeder may be utilized which can have a lower paper feed reliability.

Advantage:- low purchase cost, can handle multi-part forms, cheap to operate, only needs fresh ribbons, rugged, low repair cost and the ability to print on continuous paper. This makes it possible to print long banners that span across several sheets of paper.

Disadvantages:- noisy, low resolution not all can do color, color looks faded and streaky, slowness and more prone to jamming - with jams that are more difficult to clear. This is because paper is fed in using two sprockets engaging with holes in the paper. A small tear on the side of a sheet can cause a jam, with paper debris that is tedious to remove.

Design

Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which is driven forward by the power of a tiny electromagnet or solenoid, either directly or through small levers (pawls). Facing the ribbon and the paper is a small guide plate named ribbon mask holder or protector, sometimes also called butterfly for its typical shape. It is pierced with holes to serve as guides for the pins. This plate may be made of hard plastic or an artificial jewel such as sapphire or ruby.

The portion of the printer containing the pins is called the print head. When running the printer, it generally prints one line of text at a time. There are two approaches to achieve this:

The common serial dot matrix printers use a horizontally moving print head. The print head can be thought of featuring a single vertical column of seven or more pins approximately the height of a character box. In reality, the pins are arranged in up to four vertically or/and horizontally slightly displaced columns in order to increase the dot density and print speed through interleaving without causing the pins to jam. Thereby, up to 48 pins can be used to form the characters of a line while the print head moves horizontally.

In a considerably different configuration, so called line dot matrix printers use a fixed print head almost as wide as the paper path utilizing a horizontal line of thousands of pins for printing. Sometimes two horizontally slightly displaced rows are used to improve the effective dot density through interleaving. While still line-oriented, these printers for the professional heavy-duty market effectively print a whole line at once while the paper moves forward below the print head.

The printing speed of serial dot matrix printers with moving heads varies from 30 to 1550 cps.  In contrast to this, line matrix printers are capable of printing much more than 1000 cps, resulting in a throughput of up to 800 pages/hour.

Because the printing involves mechanical pressure, both of these types of printers can create carbon copies and carbonless copies.

These machines can be highly durable. When they do wear out, it is generally due to ink invading the guide plate of the print head, causing grit to adhere to it; this grit slowly causes the channels in the guide plate to wear from circles into ovals or slots, providing less and less accurate guidance to the printing wires. Eventually, even with tungsten blocks and titanium pawls, the printing becomes too unclear to read, a common problem when users failed to maintain the printer with regular cleaning as outlined in most user manuals.

What is a Dot Matrix Printer?