Printing Rates; Printing Mechanism - Printronix P5000 Maintenance Manual

Chapter 6

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 such attributes as bold or
emphasized print, superscripts, subscripts, or elongated characters also
reduce print speed, but the reduction is never less than half the rates of the
same lines printed without such attributes. The actual print rate of lines
containing these attributes depends on the specific print job, but printer
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 makes it possible to
print forms and text simultaneously and to mix fonts on the same print line.
Such use of multiple densities and reverse paper feed also affects the printing
rate.

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.
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