Tuesday, November 20, 2007

Dot matrix printer

Unlike a typewriter or daisy wheel printer, letters are tired out of a dot matrix, and thus, varied fonts and random graphics can be produced. Because the printing involves mechanical pressure, these printers can create carbon copies and carbonless copies. A dot matrix printer or impact matrix printer refers to a type of computer printer with a print head that runs back and forth on the page and prints by impact, outstanding an ink-soaked cloth ribbon beside the paper, much like a typewriter.

Each dot is formed by a tiny metal rod, also called a "wire" or "pin", which uses the power of a tiny electromagnet or solenoid to drive it forward, either directly or through small levers .Facing the ribbon and the paper is a small guide plate (often made of an artificial jewel such as sapphire or garnet) pierced with hole to provide as guides for the pins. The moving portion of the printer is called the print head, and prints one line of text at a time.The majority dot matrix printers have a single vertical line of dot-making apparatus on their print heads; others have a few interleaved rows in order to improve dot density.

These machines can be highly durable, but eventually wear out. Ink invades the direct 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 correct guidance to the printing wires. After about a million characters, even with tungsten blocks and titanium pawls, the printing becomes too unclear to read.


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