U.S. patent application number 09/894485 was filed with the patent office on 2001-11-01 for apparatus and method for reducing disc surface asperities to sub-microinch height.
This patent application is currently assigned to Seagate Technology LLC. Invention is credited to Liners, William O., Schaenzer, Mark J..
Application Number | 20010036800 09/894485 |
Document ID | / |
Family ID | 26797673 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010036800 |
Kind Code |
A1 |
Liners, William O. ; et
al. |
November 1, 2001 |
Apparatus and method for reducing disc surface asperities to
sub-microinch height
Abstract
A honing head for microburnishing surface of a
recording/reproducing disc to a smoothness at which asperities are
limited to submicron heights including a hardened contact bearing
surface having an array of depressions with abrupt trailing edges
interconnected by recessed channels leading outwardly from the
honing head. The array of channels span a band in which an asperity
may be present, and the sharp edges shear off the asperities within
the band which extend above the chosen submicroinch height, with
the separated particulates being passed through the recesses and
channel system to the outer edge of the honing head. The trailing
edges act to shear off the unwanted heights of the asperities,
while the recesses enable pressure differentials and air flows to
direct the separated particulates outwardly relative to the disc,
centripetal forces of rotation bearing the particulates from the
disc. A diamond-like coating on the entire contact bearing surface
and the recesses aids in reducing wear and the stiction of the
smooth surfaces to the disc that is being burnished. This
arrangement has the further advantage that the honing head may be
prepared by photomicrolithographic techniques to generate the array
of recesses on a production basis, with the recesses having
precisely determined depths and perpendicular trailing edge walls.
Ion milling and other known techniques can be used to remove the
materials in the chose patterns quickly and efficiently.
Inventors: |
Liners, William O.;
(Minnetonka, MN) ; Schaenzer, Mark J.; (Eagan,
MN) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
Seagate Technology LLC
Scotts Valley
CA
|
Family ID: |
26797673 |
Appl. No.: |
09/894485 |
Filed: |
June 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09894485 |
Jun 28, 2001 |
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09404984 |
Sep 22, 1999 |
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6273793 |
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60100903 |
Sep 23, 1998 |
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Current U.S.
Class: |
451/41 |
Current CPC
Class: |
Y10S 451/901 20130101;
B24B 33/08 20130101; Y10T 29/47 20150115; B24D 99/00 20130101; B24B
39/06 20130101; Y10T 29/474 20150115 |
Class at
Publication: |
451/41 |
International
Class: |
B24B 001/00 |
Claims
We claim:
1. A honing head for burnishing a surface of a planar disc to be
used in data recording and reproduction, the head comprising: a
sliding body having a bearing surface with a polished finish; an
array of recesses formed into the bearing surface of the body,
wherein trailing edges of the recesses form shearing edged walls;
and at least one channel formed into the bearing surface wherein
the channel interconnects the array of recesses and extends towards
an outer edge of the slider.
2. A honing head as set forth in claim 1 above, wherein the array
of recesses includes a geometry in which individual recesses
overlap and in which the pattern of recesses includes recesses that
are aligned in separate rows, and wherein there are a number of
channels each extending through a number of recesses in a different
one of the rows.
3. A honing head as set forth in claim 2 above, wherein the array
of recesses is arranged in an oval configuration, and wherein the
bearing surface includes a diamond-like coating.
4. A honing head as set forth in claim 3 above, wherein the sliding
body comprises an aluminum oxide-titanium carbide material, and
wherein the honing head has dimensions of less than 0.10 of an inch
on a side and the dimensions of the recesses are less than 500
microns on a side.
5. The honing head as set forth in claim 4 above, wherein the
recesses are diamond shape, with a trailing edge corner being
directed in a direction toward the relative movement of a disc
relative to the honing head, and wherein the recesses are of a
depth of 10-20 microns.
6. A method for burnishing a surface of a planar disc to be used in
data recording and reproduction by employing a slider mechanism
having an array of surface recesses and at least one channel
interconnecting the array of surface recesses comprising the steps
of: rotating a planar disc having surface asperities about an axis
substantially normal to the disc surface; scanning a surface of the
planar disc to be burnished with a magnetic data-head equipped with
a piezo-electric element for detecting asperities, wherein the
magnetic data-head is matched in its flight properties to the
flight properties of a standard data-head which is later to scan
the disc surface in normal operation; monitoring electric signals
generated by the piezo-electric element during contact between the
data-head and surface asperities, wherein the electric signals are
stored in a computer to locate target locations; moving the slider
mechanism, maintained in substantially parallel relation to the
disc at a nominal height from the nominal surface of the disc, to a
desired target location; shearing upper surfaces of the asperities
with trailing edges of the surface depressions within the slider
mechanism; collecting the sheared asperities upper surfaces within
the surface depressions; expelling any excess debris away from disc
surface through the channels interconnecting the surface
depressions by centripetal forces; and continuing the
above-mentioned steps until a sufficient surface smoothness it
attained.
7. A method according to claim 6 above, wherein the slider
mechanism is urged against the disc with a force of less than 10
grams, the slider mechanism has a surface area of less than
{fraction (1/100)} inch in contact with the disc, and wherein the
asperities to be removed are of less than a microinch in height
above the nominal surface of the disc.
8. A method as set forth in claim 6 above, wherein the disc is
rotated at a surface velocity of from 400-600 inches per second,
and further including the steps of utilizing the rotational speed
of the disc to generate pressure differentials and air currents in
the recesses to move sheared particulates from the vicinity of the
honing head.
9. A method for removing minute surface imperfections from a planar
disc to be used in data recording and reproduction by employing a
slider mechanism having surface depressions comprising the steps
of: rotating a disc having surface imperfections about an axis
substantially normal to the disc surface; maintaining the slider in
substantially parallel relation to the disc at a height of less
than 1 min from a nominal surface of the disc; shearing upper
surfaces of imperfections with trailing edges of depressions;
continuing the operation at that radial location until a track of
desired surface smoothness is defined; and repeating the
above-mentioned steps at different radial locations.
10. A head for micro-burnishing a nominally flat surface to reduce
asperities to less than about 0.5 min. relative to a nominal plane
of a flat surface comprising: hardened planar surface of less than
1/100 in.sup.2 in area, the surface including an array of diamond
shaped depressions having apices angled in the direction of
relative movement between the element and the surface to be
micro-burnished and the surface also including a plurality of
recessed channels interconnecting depressions in the array with an
edge of the element to form outlets for the collected
particulate.
11. A head as set forth in claim 10 above, wherein the array of
depressions is arranged in rows within the hardened planar surface,
and wherein each channel intersects the recesses in a different
row.
12. A head as set forth in claim 11 above, wherein the recesses in
the array have dimensions of less than about 300 microns on the
side, wherein the recesses are of uniform depth of in the range of
about 10-20 microns, and wherein the hardened planar surface
includes a diamond like coating.
13. A head as set forth in claim 10 above, wherein the diamond
shaped depressions are not depressions but are recesses and they
are not even diamond shaped because they are of general shape which
could be oval or triangular and which have trailing edges which are
in communication with the channels that intersects that particular
head and furthermore wherein the array of heads overlaps in a
direction transverse to the direction of relative movement between
the disc and head so as to cover the entire band and the head has a
contact surface that has a chamfer on the leading edge and the
outline of the array is curvilinear in shape such as to provide a
transition between lesser number of recesses at the sides of the
array in comparison to lots of recesses in the middle of the
array.
14. A method for fabricating a honing head, having an array of
depressions, used for burnishing a planar disc to be used in data
recording and reproduction, using photolithographic techniques,
comprising the steps of: applying a photoresist material to a
bearing surface in a pattern defining an array of planar
geometries; exposing the bearing surface to a light source,
creating a mask in the form of an array of planar geometries,
wherein the array of planar geometries are unmasked and define the
surface topography of the bearing surface; exposing the head to
plasma rays, wherein the unmasked array of planar geometries will
be milled to a desired depth; and applying a diamond-like-carbon
coating to all surfaces of the head.
15. A method for burnishing a surface of a planar disc to be used
in data recording and reproduction by employing a slider mechanism
having an array of surface depressions and at least one channel
interconnecting the array of surface depressions comprising the
steps of media comprising the steps of: rotating a planar disc
having surface asperities about an axis substantially normal to the
disc surface; and positioning a surface of the slider mechanism
parallel and adjacent a nominal planar disc surface, wherein the
array of surface depressions provide negative pressure between the
nominal planar disc surface and the slider to enable the slider to
travel within about 0.6 .mu.in of the nominal planar disc
surface.
16. Apparatus for reducing disc surface asperities to sub-micro
inch height, the apparatus comprising: a burnishing head; and means
disposed on the burnishing head for micro-burnishing a normally
flat surface to reduce asperities to less than 0.5 min. relative to
a nominal plane of the flat surface.
Description
REFERENCE TO PRIOR APPLICATION
[0001] This application relies for priority on a previously filed
provisional application, Ser. No. 60/100,903, filed in Sep. 23,
1998.
FIELD OF THE INVENTION
[0002] This invention relates to the microfinishing of surfaces,
and particularly to the reduction of minute discontinuities or
asperities on the surface of discs used in the recording and
reproduction of data.
BACKGROUND OF THE INVENTION
[0003] As hard disc recording and reproduction systems for digital
data processing have evolved, there have been continuing increases
in track density and longitudinal recording density, such that data
recording capacities have increased by orders of magnitude. A
fundamental factor in achieving these results has been the
development of transducers which are supported by air bearings at
very small flying heights (1 microinch or less) above the surface
of the disc. The aerodynamics of the pad facing the disc, and a
sensitive and precise gimbal support arm, facilitate noncontact
operation with these minute gaps which in turn provides extremely
efficient coupling between the transducer and the active surface
(whether magnetic or magneto-optical) of the disc.
[0004] As advances have been made in these respects, corollary
advances have also been made in disc manufacture, and in
manufacturing processes and test procedures, to enable the disc
surfaces to be essentially planar, to a high degree of precision.
The discs are mass produced, enabling the virtually universal
adoption of hard disc files for data processors in small and large
capacity systems to become feasible because of the very low cost
and very high performance levels which have been reached. The discs
may be single sided or double sided, as they are burnished and
finished to a given smoothness. With submicroinch flight heights,
however, burnishing alone is not satisfactory, because very minor
irregularities, typically called asperities, still can exist. These
must either be eliminated before the disc can be installed, or the
disc must be rejected for use.
[0005] Automated test beds have been devised for use in a final
honing procedure for these high capacity hard discs. These test
beds include "glide head" mechanisms, each glide head having a
sensitive force sensor so that, with the glide head flying above
the disc surface at a given height (at the order of a microinch or
less) asperities can be detected. The disc is rotated at angular
velocities typical for normal operations, giving surface rates of
400 ips to 600 ips, depending upon radial position. The glide head
is scanned across the active recording surface of the disc, with
the sensor generating a signal excursion whenever an asperity is
encountered. Depending on the amplitude and duration of the signal
excursion, these asperities can be categorized (as for example
"hard" hits or "soft" hits) and the instrumentation system can
identify the radius for future processing. At this point, a honing
head, supported by a gimbal arm to be radially movable, is also
scanned across the disc, specifically to those radial positions at
which asperities had been detected. The honing head typically has
small projections from a flat surface, and flat contact areas on
the projections that are separated by grooves, such that the edges
of the projections engage and hone the asperities.
[0006] Such honing head designs, however, have disadvantages that
become most apparent when attempting to provide a surface for
recording/reproduction head operation at submicroinch levels.
Highly polished flat surfaces in contact induce forces of molecular
attraction between them, and thus introduce stiction effects which
can render operation non-uniform. In addition, with a honing head
of this design the top increment of an asperity may be separated
from its base, but is not necessarily removed from the disc itself,
thus representing an object that can possibly interfere with signal
transduction.
[0007] After honing head operation, the disc is again tested by the
glide head and instrumentation system, to verify that asperities
beyond the chosen threshold have been eliminated. Thereafter, the
disc can be approved for use in a production unit. These processes
are carried out in clean room conditions and the discs are confined
within closed environments with air properly filtered to remove all
but very minute particle sizes which can be tolerated.
SUMMARY OF THE INVENTION
[0008] Devices, systems and methods in accordance with the
invention utilize the trailing edges of an array of recesses formed
in a planar like surface having an anti-stiction coating and
including a plurality of channels leading from the recesses to the
radially outward portion of the honing head. The recesses
preferably converge toward the trailing edge, with straight or
curved sides, and shear off the apices of asperities, the channels
causing particulate matter to flow radially outwardly from the
honing head and to be urged by centripetal forces off the disc. Air
trapped under the leading edge of the honing head merely raises its
leading edge minutely, but the angle assists the shearing action by
the subsequent trailing edges. Concurrently, the recesses in the
outwardly angled channels are under negative pressure relative to
the surrounding ambient pressure, drawing the asperities from the
surface of the disc and toward the airflow region adjacent the
honing head that is created by the high speed disc.
[0009] In a more particular example of devices and methods in
accordance with the invention, useful in eliminating asperities so
that recording heads can fly at altitudes of 0.5 microinch or less,
the recesses are essentially diamond shaped trenches, each having a
trailing edge defined by converging sides of the diamond. Each
trench of this type has dimensions of about 168 microns by 168
microns, and a depth of 10 to 20 microns, while the overall
configuration of the pad is 40 mm by 80 mm in this practical
example. The honing head is mounted at the end of a gimbal arm, and
urged toward the disc with a pressure which depends upon head area,
in this instance about 6.5 grams. The channels extend at an angle
toward the trailing edge and are a depth corresponding to the
trenches, and so angled that they intercept each of a series of
intervening trenches along the path to the external radius. The
surface of the honing head incorporates a diamond like coating
(dlc) which hardens the surface, improves the shearing action and
enhances uniformity of operation because it substantially reduces
the stiction effect. Alternatively, superior results have also been
achieved with trenches that are curved, e.g. oval, in
configuration, and the advantages are also preserved in other
geometries, such as triangular trenches which have an apex at the
trailing edge.
[0010] Honing heads of this character may readily be fabricated
using photolithographic techniques, as by depositing a
photosensitive resist material on a planar head, exposing the
photoresist material through a photographic mask to leave a
removable pattern corresponding to the trenches and channels, and
then removing the material by ion milling, acid etching or plasma
etching to form straight sides for shearing, and recesses of the
chosen depth. After the honing head has been processed to this
extent, the dlc material is applied, readying the head for
attachment in the assembly in use.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A better understanding of the invention may be had by
reference to the following description, taken in conjunction with
the accompanying drawings, in which:
[0012] FIG. 1 is a simplified perspective view of a test bed
assembly employing a honing head in accordance with the
invention;
[0013] FIG. 2 is a perspective view showing the principal elements
of a honing head in accordance with the invention;
[0014] FIG. 3 is a fragmentary perspective view of a portion of the
honing head of FIG. 2, showing further details thereof;
[0015] FIG. 4 is a plan view of the contact side of a honing head
in accordance with the invention;
[0016] FIG. 5 is a fragmentary perspective view of the contact side
of a honing head in accordance with the invention, showing the
active portions of a trench and channel arrangement in the
head;
[0017] FIG. 6 is a simplified perspective view of the shearing
action on an asperity of a honing head in accordance with the
invention, the elements being shown in greatly exaggerated
form;
[0018] FIG. 7 is a plan view of the underside of an alternative
geometry of recesses in a honing head in accordance with the
invention; and
[0019] FIG. 8 is a flow chart diagram of steps in a method of
fabricating a honing head in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] In a typical test bed instrumentation system, utilized in a
high level clean room environment, a disc 10 that has been
burnished and is to be honed is mounted on a spindle 12 and rotated
by a drive motor 14 at an angular velocity giving a surface
velocity of 400-600 ips depending upon radius, this surface
velocity corresponding to typical recording system operations. For
a three and one half inch disc, the rotational rate is
approximately 6000-9000 rpm. The system includes a glide head 20,
having a narrow dynamic slider 22 and incorporating a sensitive
force sensor, such as a PZT device 24, mounted by a gimbal on the
end of an arm 26 which is moved between radial extremes on the disc
10 by a rotary arm or other scanning mechanism 28. Signals detected
by the PZT sensor are fed to a data processing system 30 which
controls the rate of radial increment of both the scanning
mechanism 28 and a honing mechanism described below. The data
processing system 30 includes conventional signal processing
circuits for measuring the height of signal excursions generated by
the PZT sensor 24 on encountering asperities, and conventional
means for storing the radial locations of the asperities.
[0021] A small honing head 34 is gimbaled on the end of a
positioning arm 36 that is moved by a honing head control mechanism
38 under signals from the data, processing system 30. The general
arrangement of the honing head 34 is depicted in FIGS. 2 and 3, to
which reference may now be made. The positioning arm has a thin but
still inflexible body 40 overlying a metal base strip 42 near the
free end of which is a gimbal cutout 44 in the base strip 42,
defining a support for the honing head 34 which flexes slightly
toward and away from the disc when in operation. On the superior
side of the gimbal cutout 44 is a dimple 48 which limits upward
flexure of the gimbal cutout 44 and the honing head 34 because the
body 40 acts a physical limit when engaged by the dimple 48.
[0022] With reference to FIG. 4, the honing head 34 includes a
slider pad 50 of substantially rectangular shape, which, in this
example, has dimensions of about 80 mls by 63 mls by 17 mls. A
bearing surface 52 on the contact side of the slider pad 50 is
perpendicular to the outer wall 54 of the slider pad 50, except at
a tapered leading edge 56, which includes a chamfer at an angle of
8 microrad and having a length in the direction of relative
movement of approximately 10 mls.
[0023] As seen in FIGS. 4 and 5, viewing the contact side of the
slider pad 50, the bearing surface 52 comprises an array 60 of
concavities or depressions in the otherwise substantially planar
surface. The array 60 is of circular or oval outline, to minimize
edge chipping and reduce edge effects thereby substantially
reducing the risk of damage to the disc media. The concavities and
depressions, in this example, are diamond shaped trenches 62, one
corner of which points in the direction of the leading edge 56,
while the trailing edge portions provide shearing walls and
accessible space for collecting particles from asperities as will
be described hereinafter. The trenches 62 are arrayed so that they
overlap laterally within the array outline so as to assure coverage
of a radial band of the disc when the honing head 34 is at a
particular position. The trenches 62 are interconnected by channels
64 that pass through rows of the trenches in a trailing edge
direction that leads to the outside wall 54 of the slider pad
50.
[0024] The trenches 62 preferably have diagonal dimensions of about
208 microns by 264 microns and depths of about 10-20 microns (14
microns in this example). Using micro lithographic techniques as
described hereafter, the trenches 62 have vertical back (trailing
edge) walls 66 with shearing edges 68. The channels 64, which have
depths corresponding to the depths of the trenches, are shown with
exaggerated depths for clarity in FIG. 5. The entire surface of the
slider pad 50 is treated with a known diamond like coating (dlc),
which not only enhances the hardness of the surface and reduces
wear rates, but also reduces any tendency toward stiction and
provides an inert surface which helps to eliminate generation and
redistribution of particle contamination on the disc surface. The
dlc coating in this instance is applied after the trenches and
channels are formed, and preferably is in a 75/25 ratio.
[0025] In the usage of this honing head, as in the context of the
sensing and honing approach used in the FIG. 1 system, the honing
head 34 is held in contact against the surface of the disc 10 at
the chosen radial position at which an asperity has been detected.
A force of approximately 6.5 grams is used in this example, based
upon the surface area of the slider pad 50, which is
proportionately smaller than prior honing heads. Experience has
shown that the contact force can be reduced in proportion to slider
pad contact area. In this instance the load of 6.5 grams provides
some 15,033 g/in.sup.2 of actual surface contact pressure on the
media. Where an asperity is to be removed, and especially in the
case of the "hard hits", the shearing action of the back wall of
the trenches 62 levels off the apex of the asperity, shown in
somewhat idealized form in FIG. 6. Since the objective is to allow
submicron flight height on the recording and reproduction
transducer head, the elevation of asperity tips or apices above the
nominal disc surface must be lowered, and particularly in a fashion
to provide a relatively level surface. The shearing edges 68
defined by the trench back walls 66 provide just such a function,
since the bearing surface 52 will pass over asperities 70 of lesser
submicron height, but only until a certain height is reached, at
which level the shearing edges 66 of trailing trenches in the array
shear off the excessive portions. At the speeds of rotation used
for the disc, the tapered leading edge 56 of the pad allows a
minimal amount of air to raise the leading edge slightly, thus
facilitating this successive shearing action.
[0026] The sheared matter in the form of minute particulates, of
course, cannot be allowed to either remain on the disc or function
to clog the honing head. In this respect, the trenches 62 and
channels 64 greatly facilitate the cleaning action of the honing
head and disc, since there are both air pressure differentials and
air flows, as well as centripetal forces, which tend to disperse
the particulates in a direction away from the disc 10. Air moving
as a boundary layer with the disc creates slightly negative
pressure in the trenches 62 and channels 64, thus initially
accumulating particulates in the trenches, until air flow along the
channels to the outer wall of the slider pad removes the
particulates, after which the centripetal force of the disc
rotation impels the particulates to the outer radius and off the
disc. If any particulates do remain within the trenches or channels
they are readily removable when the honing head is cleaned.
[0027] Thus, the honing head in accordance with the present
invention improves disc surface tribology so as to augment the
aerodynamic performance of read/write heads while reducing head
vibration due to asperities. Given that the asperities are only of
the order of 0.6 microinches or less, the improvement of stable
maintenance of ultralow flying heights which this honing action in
parts enables very high density recording and reproduction with
minimal head crash.
[0028] It will be recognized by those skilled in the art that
either side of a disc may be microburnished in the fashion
described, but that the honing head is then to be configured to
direct particulates toward the outer diameter of a disc, and
furthermore the contact force supplied to the head is to be
adjusted to compensate for gravity. Further in the present example,
although the gimbal cutout 44 (which acts as a suspension spring)
is of stress relieved stainless steel, other metals that may
provide similar pressure characteristics, such as aluminum,
titanium, and copper and various alloys, can alternatively be used.
It will also be recognized by those skilled in the art that other
configurations of depressions and concavities may be employed,
along with other outlines of arrays. In FIG. 7, for example, the
contact surface includes a substantially circular array of
oval-shaped depressions 72. In another form, the depressions may be
of triangular shape, with the trailing edge comprising two
converging sides of a triangle.
[0029] The array of recesses or depressions in the honing head may
conveniently be formed by modern photolithographic techniques,
which enable straight-sided depressions to be formed at precisely
controlled depths and with vertical sides for best shearing action,
particularly at the small sizes and shallow depths used in this
example. Referring to FIG. 8, for example, once the flat surface of
the honing head has been prepared, the process for formation of the
active surface begins by application of photoresist material
uniformly to the contact bearing surface on the honing head 80. The
photographic mask bearing the desired pattern is then superimposed
for exposure, with or without the use of reducing optics, and the
exposure is for a time sufficient to cure the material in the
desired pattern 81. A positive or negative photoresist material may
be used, as desired.
[0030] The photoresist is then washed off or otherwise removed in
conventional manner, as by washing 82, and the honing head is
treated to remove material in the desired pattern to the chosen
depth 83. Although ion milling is preferred because the equipment
is used for a number of other purposes as well other conventional
techniques such as acid etching, plasma etching and other
conventional approaches may readily be used alternatively.
[0031] After the configuration of the head has been defined, a dlc
coating 84 is applied to all surfaces of the head, including the
trenches and channels, to give the desired final properties.
[0032] In a preferred embodiment the sliding body comprises an
aluminum oxide-titanium carbide material and the honing head has
dimensions of less than 0.10 of an inch on a side and the
dimensions of the recesses are less than 500 microns on a side.
[0033] A method for burnishing a surface of a planar disc to be
used in data recording and reproduction is disclosed. The method
employs a slider mechanism having an array of surface recesses and
at least one channel interconnecting the array of surface recesses.
The method includes rotating a planar disc 10 having surface
asperities about an axis substantially normal to the disc surface.
A surface of the planar disc 10 to be burnished is scanned with a
magnetic datahead 20 equipped with a piezoelectric element 24 for
detecting asperities, wherein the magnetic datahead is matched in
its flight properties to the flight properties of a standard
datahead which is later to scan the disc surface in normal
operation. Electric signals generated by the piezoelectric element
during contact between the datahead 34 and surface asperities are
monitored, wherein the electric signals are stored in a computer 30
to locate target locations. The slider mechanism 34 is moved and
maintained in substantially parallel relation to the disc at a
nominal height from the nominal surface of the disc to a desired
target location. Upper surfaces of the asperities are sheared with
trailing edges of the surface depressions within the slider
mechanism. The sheared asperities are collected at the upper
surfaces within the surface depressions and any excess debris is
expelled away from disc surface through the channels
interconnecting the surface depressions by centripetal forces. The
above-mentioned steps are continued until a sufficient surface
smoothness is attained.
[0034] While a number of forms and variations in accordance with
the invention has been described, it will be appreciated that the
invention is not limited thereto but encompasses all variations and
alternatives within the scope of the appended claims.
* * * * *