Design
The heart of the system is an interchangeable metal or plastic "daisy wheel" holding an entire character set as raised characters moulded on each "petal". In use a servo motor rotates the daisy wheel to position the required character between the hammer and the ribbon. The solenoid-operated hammer then fires, driving the character type on to the ribbon and paper to print the character on the paper. The daisy wheel and hammer are mounted on a sliding carriage similar to that used by dot matrix printers.
Different typefaces and sizes can be used by replacing the daisy wheel. It is possible to use multiple fonts within a document: font changing is facilitated by printer device drivers which can position the carriage to the center of the platen and prompt the user to change the wheel before continuing printing. However, printing a document with frequent font changes and thus requiring frequent wheel changes was a tedious task.
Many daisy wheel machines offer a bold type facility, accomplished by double- or triple-striking the specified character(s); servo-based printers advance the carriage fractionally for a wider (and therefore blacker) character, while cheaper machines perform a carriage return without a line feed to return to the beginning of the line, space through all non-bold text, and restrike each bolded character. The inherent imprecision in attempting to restrike on exactly the same spot after a carriage return provides the same effect as the more expensive servo-based printers, with the unique side effect that as the printer ages and wears, bold text becomes bolder.
Like all other impact printers, daisy wheel printers are noisy.
Read more about this topic: Daisy Wheel Printing
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