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Print Wire Frequency Dependent Compensation for Serial Printers

IP.com Disclosure Number: IPCOM000114411D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 8 page(s) / 329K

Publishing Venue

IBM

Related People

Downey, HA: AUTHOR [+6]

Abstract

In serial wire matrix printers, dots are formed on paper by the impact of a print wire. The kinetic energy present in the wire must be carefully modulated in order to avoid impacts which are too light because of insufficient energy, or which are destructive to the ribbon because of too much energy. If a wire is fired from a quiescent state, the energy content is fixed and reproducible. Typically, however, the wire is fired at frequencies above that at which the wire will come to rest before firings. In fact, printer performance is optimized by firing the wires at the maximum possible repetition rate that they will sustain. This results in a significant amount of residual kinetic energy in the wire from one firing to the next.

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Print Wire Frequency Dependent Compensation for Serial Printers

      In serial wire matrix printers, dots are formed on paper by the
impact of a print wire.  The kinetic energy present in the wire must
be carefully modulated in order to avoid impacts which are too light
because of insufficient energy, or which are destructive to the
ribbon because of too much energy.  If a wire is fired from a
quiescent
state, the energy content is fixed and reproducible.  Typically,
however, the wire is fired at frequencies above that at
which the wire will come to rest before firings.  In fact, printer
performance is optimized by firing the wires at the maximum possible
repetition rate that they will sustain.  This results in a
significant amount of residual kinetic energy in the wire from one
firing to the next.

      If very high operating speeds are to be achieved, it is
necessary to compensate for the amount of kinetic energy remaining in
the print wire at the time of each firing.

      This paper describes a unique, highly effective technique by
which the electrical input to the electro-magnetic actuator can be
dynamically adjusted to compensate for the mechanical energy
remaining in the wire at time of firing.  The method described is
effective in reducing the variations in both the force of impact and
the time of impact.

      This paper also describes a unique hardware configuration for
implementing this technique in a multiple print wire system.  This
configuration utilizes time sharing of common circuitry between print
wires, providing not only hardware savings, but a performance
advantage as well.

      Description of Print Wire Dynamics - Fig. 1 shows the typical
relationship of the flight time of a print wire versus the frequency
at which it is being fired.  Flight time is defined as the time of
application of the firing pulse to the time of impact with the paper
surface.  Fig. 2 shows the typical variation of the wire impact force
on the paper as a function of firing frequency.  Through empirical
testing, these relationships have been shown to be quite consistent
across the population of manufactured print heads of a particular
configuration.  The specific shape of these curves is design
specific, but the overall pattern has been found to be similar for
all wire matrix printheads.

      If a print head is operated such that all frequencies are used,
the variation in flight time causes horizontal misregistration of
dots, and the variation in impact force causes light dots if the
force is too low, or ribbon damage if the force is too high.  This is
the problem addressed by this paper.

      Figs. 1 and 2 show the frequency range divided into three
regions.  In the low frequency region (low firing rate), both flight
time, tf0, and print force, F0, are virtually constant.  This is
where the print wire has settled out, and print quality is
consistent.

      In the middle frequency band, the fli...