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Auto Alignment
Auto alignment is a process to determine the X and Y coordinates of the spindle center
based on an actual written data track evaluation. The spindle center coordinates are
important because it is the reference position when the spinstand places the head on a
specific location on the media. Auto alignment is performed when the spinstand is shipped
from the factory. However, if the individual differences of the HGA's dimensions or other
dimensional errors are critical for your measurement, you can perform the auto alignment
in order to eliminate such errors. The auto alignment is also performed when some of the
spinstand mechanical parts are replaced for repair.The auto alignment must be performed
for both up and down face HGAs.
Auto Alignment Algorithm
The VEE measurement program (Test Environment) performs the auto alignment in
accordance with the following algorithm.
1. Preprocessing
Perform the band erase and write a data pattern at the position of radius = "start radius"
and skew = 0°. "start radius" should be set manually in advance using the auto
alignment menu.
2. Rough tune (see Figure 5-62)
Find a rough skew = 0° position on the track by searching the written track.
3. Fine tune first step (see Figure 5-62)
Using the skew = 0° coordinates (obtained by the rough tune) and start radius data,
move the head to the three positions (skew = 0°, +3°, −3°) on the track, determine the
accurate coordinates of the three positions by searching the trace, and calculate spindle
center coordinates.
4. Fine tune (step 1) (see Figure 5-62)
Using the spindle center coordinates obtained in the previous step, move the head to
three positions (skew = 0°, "step 1 positive," "step 1 negative") on the track, determine
the accurate coordinates of the three positions by searching the track, and calculate
more accurate spindle center coordinates. "step 1 positive" (positive skew angle for
step 1) and "step 1 negative" (negative skew angle for step 1) should be set manually in
advance using the auto alignment menu.
5. Fine tune (step 2) (see Figure 5-62)
Using the spindle center coordinates obtained in the previous step, move the head to
three positions (skew = 0°, "step 2 positive," "step 2 negative") on the track, determine
the accurate three positions by searching the track, and calculate more accurate spindle
center coordinates. "step 2 positive" (positive skew angle for step 2) and "step 2
negative" (negative skew angle for step 2) should be set manually in advance using the
auto alignment menu.
6. Storing data
Save the spindle center coordinates data obtained in the previous step in the
non-volatile memory of the spinstand.
Chapter 5
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Measurement Definition
Auto Alignment
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