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Current
Negative Pressure Type
Sliders |
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The
anatomy of a typical negative
pressure type air bearing
is shown right.
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Benefits
of Negative Pressure Designs |
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“Negative”
(sub-ambient) Pressure has
several benefits: |
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Increases
Stiffness (Reduces FHT variations |
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Reduces
fly height drop at altitude |
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Reduces
speed sensitivity (minimizes
fly height drop at servo
write speeds) |
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Recent
Mechanical Spacing History |
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Mechanical
Spacing is Approaching
Zero |
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High
density drives of the future
will require that mechanical
spacing, or fly height,
approach zero. Similar reductions
will be required in disk
and head rotective overcoat
layers, since these layer
add to the magnetic spacing.
Three broad approaches are
possible: |
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Reduction
in spacing in conventional
designs. This approach requires
improved slider designs
and a tightening of all
tolerances which affect
magnetic spacing and fly
height variations |
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Wear-in
designs. Conventional bearings
often require a wear-in
period. Similar ideas have
been proposed for air bearing
sliders. |
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Contact
designs. Contact has been
studied for many years and
is still and active area
of research. Principal problems
include controlling interface
wear and achieving a stable
interface which permits
reading and writing magnetic
data. |
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What
is this thing called Fly
Height? |
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Fly
height: The distance from
the ABS surface to the mean
disk surface. In the ABS
code, the disk is idealized
as a perfectly flat surface
at 0 fly height. |
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Take
Off Height: The flying height
at which contact with highest
asperities occurs. |
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Glide
Height: The flying height
at which asperities are
detected with a slider equipped
with a PZT sensor. (Glide
Height > TOH) |
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Modeling
Contact Sliders |
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some modification, the
air bearing model
can handle contact calculations. |
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If
the disk is treated as
an elastic surface a contact
force can be calculated.
In
a contact design, suspension
parameters are more important
in control of contact
force variations.
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