Impact printers:Dot matrix printer; Daisy Wheel Printer; Drum Printer; Chain Printer

1. Dot matrix printer:
Impact printers is most commonly used impact printer today. Dot matrix printers produce images by striking and inked ribbon with tiny pins on a print head that passes over the page a line at a time. The main component of dot matrix printer is a print head that has the rows of electromagnetically activated pins, which create tiny dots on output media. Most commonly used pin arrangements are 9, 24, 48 pins arranged in rows.
On receiving instruction from the PC, the printhead can push any of the pins out, in any combination. Thus enabling printedhead to create any alphanumeric characters. These pushed out pins strike an inked ribbon, which is held in between print head and the paper and press ink from ribbon onto a paper.

Dot matrix printers are popular as they are inexpensive and have print speed of 100-600 cps. They are also capable of producing more varied output in different fonts and sizes. These printers give us draft quality, standard quality and near-letter quality prints. They can even handle multicopy forms using tractor feed paper.

2. Daisy Wheel Printer:
Daisy wheel printers are very similar to typewriters. The print element is a flat spoke wheel with characters embossed along the outer edge of spokes flat. The element spins rapidly, pausing only to allow the printing hammer time to strike the character against the ribbon or paper. Daisy wheel printers are letter quality printers but they tend to be slow and print at the rate of 25-55 cps.

3. Drum Printer:
It is a character printer. The print element is a drum or a cylinder with a complete set of characters engraved on it around the drum. There are many bands as there are printing positions along the cylinder length. Each band has one each of the different characters (typically 64). The drum rotates at the rapid speed. For each print position, there is a hammer located behind the paper. These hammers strike the paper, along with the inked ribbon, against the proper character on the drum as it passes. One revolution of the drum is required to print each line. Typical speeds of the drum printers are in the range of 300 to 2000 lines per minute.

4. Chain Printer:
It is the character printer. The print element in a chain printer is a metallic band or chain containing the embossed characters that rotates horizontally in front of paper. A complete chain consists of the five sections; each section consists of 48 characters. As the print chain rotates, properly timed print hammers strike the paper along with linked ribbon, against the proper character on the chain as it passes. Chain printer are one of the fastest impact printers that can produce up to 400 to 2500 characters per second.


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