EBS-6100
Printer User's Manual
Paragraph 4 - Operating the Printer
EBS
Ink-Jet Systems
®
92
20070529#20.5
When the printer works with an internal generator, it is very easy to reach the maximum print
rate because printing is controlled by the printer’s computer which uses a common, very
accurate, quartz oscillator to generate ink drops and release printing of successive rows.
Therefore the two processes are absolutely synchronous and cophasal.
When the printer works with a shaft-encoder, it is much more difficult to reach the maximum
print rate because two asynchronous generators need to be used. The first one is a quartz
oscillator and the other is the shaft-encoder. In addition the pulses from the shaft-encoder are
unstable and in no way are they synchronous with the pulses generated by the oscillator.
The symptoms of speeding are also different:
●
When an internal generator is used, successive rows are timed at the same time intervals.
A change in the conveyor speed results in a change of the distance between the vertical
rows and the change is proportional to the change of the conveyor speed. If the maximum
speed is exceeded slightly, the effect is hardly visible.
●
When a shaft-encoder is used, the symptoms of speeding depend on the versions of the
software that is installed on the printer. For version
20_0A
or later, each time the print rate
is exceeded rows of print are spaced widely, as it is the case when an internal generator
is used. For earlier versions, the subsequent vertical row is shifted significantly and
visibly, because no printing of a subsequent row can start until the previous row is printed
completely.
4.6.5.
Problems with reaching the maximum print rate when a shaft-
encoder is used
The description given below is a case study of the maximum print rate.
If the rates are
smaller than the maximum (with a tolerance specified below) no problems occur
. The
printers on which software version
20_0A
or later is installed switch automatically to printing
at the maximum (constant) rate when this maximum rate is exceeded.
The encoder constant.
If the shaft-encoder constant is too small, it will be difficult to reach a set resolution - the
real resolution will be rather distant from the setting. The shaft-encoder constant,
S
, is
given as a number of pulses generated when the conveyor travels over a distance of one
metre. For a given resolution
r
the printer sets the value of the system divider,
D
, which
matches the two quantities with each other. The divider can be set to integral values only
according to the following formula:
D=[(S/(100*r))+0.5],
where:
S
– encoder constant,
r
– given resolution.
The real resolution is determined from the following formula:
R=S/(100*D).
Example
The shaft-encoder constant
S
is 8820 and resolution
r
is 19.
The divider value
D
is calculated in the following way:
D
=[(
S
/(100*
r
))+0.5]=[(8820/(100*19))+0.5]=[4.64+0.5]=
5
(in round figure).
The real resolution is
R
=
S
/(100*
D
)=8820/(100*5)=
17.64
.
If the resolution is
r
=20, 21, 22, 23 and 24, the divider value
D
is always the same (as it is
given in round figure) and amounts to
D
=4. This value corresponds to the real resolution
of
R
=22.05.
If
r
=20 is chosen out of the above range, the error is 100%*((22.05/20)-1)=10.25%. The
maximum rate to be obtained corresponds to the resolution of
R
=22.05 and not to the
given value of
r
=20. Therefore for
Ttot
=1024µs the maximum rate is 26.573 m/min. If
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