EBS
Ink-Jet Systems
®
EBS-6100
Printer User's Manual
Paragraph 4 - Operating the Printer
20070529#20.5
93
a better shaft-encoder is used, a higher rate is reached - see the consideration for the
shaft-encoder constant of 44000 below.
In order to ensure that the real resolution of a diversified value is obtained in practice for
each of the resolutions
r
specified above, you need to choose a better shaft-encoder
whose constant is for example 44000.
NOTE:
If the shaft-encoder constant is increased by decreasing the diameter of the roll travelling
on the conveyor, the spread of the parameter values is usually greater.
The following values can be obtained for the shaft-encoder constant of
S
=44000:
r D R
20 22
20.00
21 21
20.95
22 20
22.00
23 19
23.16
24 18
24.44
If the shaft-encoder with the constant of
S
=44000 is used, the maximum rate of 29.296
m/min can be obtained for the given resolution of
r
=20 and
Ttot
=1024µs. This maximum
rate is much higher than for the shaft-encoder whose constant is
S
=8820.
The above data show that it may appear that the real resolution is greater than required
and the maximum rate given in metres per minute corresponds to the real resolution and
not to the given value. The percentage error
Us
increases along with an increase in the
encoder constant.
1.
Stability of the conveyor’s travel speed.
Every real installation suffers from conveyor vibration. The actual speed varies,
sometimes it is higher and sometimes it is lower. Therefore the real, temporary speed of
the conveyor is V(1+/-
∆
V). If the maximum print rate is not to be exceeded, it must not be
exceeded at any moment of time. It is not enough to measure the average conveyor
speed. The higher the vibration (instability) of conveyor travelling, the lower the maximum
achievable conveyor speed. The percentage error is
Ut
=
∆
V*100%.
2.
Accuracy of measurement of the shaft-encoder constant and conveyor travel speed.
Every measurement involves a measuring error which depends on the class of measuring
equipment and the experience of the person who takes the measurement. The pooled
percentage errors of the measurement are marked as
Up
. It may appear that the real
print rate is greater than that determined by measurement due to measuring inaccuracy.
3.
Spread of the shaft-encoder constant vs. angle of rotation.
While measuring the shaft-encoder constant we measure the average value. The
measurement usually consists of counting of (many thousand of) pulses for a number of
full shaft-encoder rotations. Whereas the real printer reacts to a distance between
successive pulses and not to the average value. Thus the accuracy of the manufacture of
the shaft-encoder (the spread between successive pulses) and the spread of the radius of
the shaft-encoder roll running along the conveyor make the distance timed by successive
shaft-encoder pulses vary. And also the print rate varies even if the conveyor speed is
stable as perfectly as possible.
In addition, if the shaft-encoder constant is to be increased (doubled) (which is vital – see
point
1
above), the electronic circuitry of the printer will react to both rising and falling
edges of shaft-encoder pulses (series
I
in the drawing below) by using them to generate
series
J
. If the duty factor of pulses from the shaft-encoder (measured at the input to the
XILINX circuit) differs by 50%, then there is an additional error
∆
b
which appears only for
odd values of the divider
D
.
Summary of Contents for EBS-6100
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