needle printer
In the dot- matrix printer, ink is transferred to the paper or other media by means of pressure. The print head of the dot matrix printer has several needles, usually between 9 and 48, which are individually mounted and can be individually controlled. The number of needles determines the step size. For example, with 9 needles this is 1/240" and with 24 needles it is 1/360".
The needles transfer the printing ink, which is on an ink ribbon, to the print medium when they stop. For black and white prints, this is a black carbon ribbon; for color prints, it is a four-color ribbon with the primary colorscyan, magenta, yellow, and black, according to the CMYK color model.
A color print is made in four passes, since the ribbon must be repositioned for each pass for the following color.
Dot matrix printers do not have an overly high resolution; this is determined by the print head and the needle thickness. The paper is fed by a stepper motor that drives a tractor shaft with pressure rollers. In the case of continuous paper, sprocket wheels, which engage in the perforation holes of the paper, ensure the exact feed.