Automatic Print Position Adjustment - Canon BJ-W3000 Service Manual

CHAPTER 2. BASIC OPERATION

6. Automatic print position adjustment

When cartridges are installed on the carriage, the nozzle positions of the cartridges may be
displaced, causing displacement of dots of different colors on the paper. The automatic print
position adjustment compensates for this displacement.
The head is automatically adjusted vertically (paper feeding) and horizontally (carriage move-
ment) as follows.
a. Vertical adjustment (paper feed)
The line patterns for 1 band in the horizontal direction are printed in the order of black, cyan,
magenta, and yellow as the carriage moves backward and forward. Then black lines for 1 band
are printed as the carriage moves backward. This process is repeated 15 times.
The distance between the center of the second black line patterns and the center of the color
pattern is measured for each of the 15 sets, the average value is calculated, and the calibration
value is determined.
b. Horizontal adjustment (carriage movement)
As before, line patterns in the vertical direction are printed, and the distance between the
center values of the black line patterns and color patterns are measured and divided into 29
intervals, the average value is calculated to determine the compensation value. Theoretically the
horizontal adjustment is accurate to 1/270 dot. The adjustment covers 6 cases as follows.
(1) The tolerances of the carriage drive components can cause the positions of ink dots on the
media to shift. The printer detects the shifted value of the black line pattern with medium
drops printed as the carriage moves forward with a drive frequency of 7.2kHz, and corrects
the standard position where ink is placed.
(2) When the carriage moves forward, the divergence between the black line pattern printed
with small drops at a drive frequency of 7.2kHz and the color line pattern is adjusted.
(3) When the carriage moves backward, the divergence between the black line pattern printed
with small drops at a drive frequency of 7.2kHz and the color line pattern is adjusted.
(4) When the carriage moves backward, the divergence between the black line pattern printed
with large drops at a drive frequency of 7.2kHz and the color line pattern is adjusted.
(5) The divergence between the black line pattern when the carriage moves forward and
backward at a drive frequency of 7.2kHz and the line pattern is adjusted.
(6) The divergence between the black line pattern when the carriage moves forward and
backward at a drive frequency of 14.4kHz and the line pattern is adjusted.
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