38
Chapter 4 Printing Rates
Printing Rates
Because a line matrix printer prints entire lines sequentially, it is faster than a
moving-printhead printer, which prints single characters sequentially. The
printing speed of text is measured in lines per minute (lpm) rather than
characters per minute (cpm).
Many variables affect printing speed, the main ones being the selected font
and the vertical dot density. Lines containing attributes such as bold or
emphasized print, superscripts, subscripts, or elongated characters also
reduce print speed to never less than half the rates of lines without such
attributes. The actual print rate of lines containing these attributes depends on
the specific print job, but software maximizes the throughput by dynamically
determining which dot rows contain adjacent dots and must be printed in two
strokes. Printing speed is not affected by the number of characters in a
character set.
The printing speed of graphics (“plot mode”) is expressed in inches per
minute (ipm).
The ability of the printer to feed paper downwards as well as upwards allows
the printing of multiple densities on a single line. This is useful for printing
forms and text together or for mixing fonts on the same print line. Use of
multiple densities and reverse paper feed also affects throughput.
Printing Mechanism
While the principles of line matrix printing are easy to state, the act of printing
dots accurately from a rapidly oscillating shuttle onto a piece of paper moving
vertically requires complex timing and coordination between printer logic and
the printing mechanism.
The printing mechanism consists of three integrated subassemblies:
• Shuttle Frame Assembly
• Ribbon Transport System
• Paper Transport System.
To Next Page
Loading...
Need help?
General