Printing Rates - Printronix P7000 Series Maintenance Manual

Chapter 7

Printing Rates

Printing Rates
A line matrix printer prints entire lines sequentially, and measures the printing
speed of text in lines per minute (lpm). This is faster than a moving-printhead
printer, which prints single characters sequentially and measures its speed in
characters per minute (cpm).
Many variables affect printing speed, the main ones being the font and the
vertical dot density selected by the user. Lines containing such print attributes
as bold or emphasized print, superscripts, subscripts, or elongated characters
also reduce print speed, but the speed reduction is never less than half the
rate of the same line 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.
The number of characters in a character set has no effect on printing speed.
The printing speed of graphics ("plot mode") is expressed in inches per
minute (ipm).
The ability of the printer to feed paper both downward and upward allows the
printing of multiple dot densities on a single line. This makes it possible to
print forms and text simultaneously and to mix fonts on the same print line.
The use of multiple dot densities and reverse paper feed affect printing rates
the same way print attributes do.
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 that is
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
•
Paper Transport System
•
Ribbon Transport System
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