U.S. patent application number 16/544965 was filed with the patent office on 2021-02-25 for intelligent continuous polishing machine and process.
This patent application is currently assigned to Laser Fusion Research Center, China Academy of Engineering Physics. The applicant listed for this patent is Laser Fusion Research Center, China Academy of Engineering Physics. Invention is credited to Fugong Chen, Jian Chen, Defeng Liao, Jian Wang, Shiyuan Wang, Ruiqing Xie, Qiao Xu, Shijie Zhao.
Application Number | 20210053174 16/544965 |
Document ID | / |
Family ID | 1000004293155 |
Filed Date | 2021-02-25 |
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United States Patent
Application |
20210053174 |
Kind Code |
A1 |
Liao; Defeng ; et
al. |
February 25, 2021 |
Intelligent continuous polishing machine and process
Abstract
An intelligent continuous polishing machine and an intelligent
continuous polishing process therefor are provided. The intelligent
continuous polishing machine includes a base platen, a rotary
platen, a multi-beam bridge mechanism, two workpiece holding
mechanisms, a lap measuring mechanism, a lap cutting mechanism, a
small-conditioner holding mechanism, a large-conditioner holding
mechanism, and a control computer. The intelligent continuous
polishing process includes a normal polishing procedure, a lap
surface shape measuring procedure, and three procedures for
correcting the lap surface shape error: a lap cutting procedure, a
sub-aperture correcting procedure, and a full-aperture correcting
procedure. All of these procedures are controlled by the control
computer through CNC programs.
Inventors: |
Liao; Defeng; (Chengdu,
CN) ; Xu; Qiao; (Chengdu, CN) ; Xie;
Ruiqing; (Chengdu, CN) ; Chen; Jian; (Chengdu,
CN) ; Chen; Fugong; (Chengdu, CN) ; Wang;
Shiyuan; (Chengdu, CN) ; Zhao; Shijie;
(Chengdu, CN) ; Wang; Jian; (Chengdu, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Laser Fusion Research Center, China Academy of Engineering
Physics |
Mianyang |
|
CN |
|
|
Assignee: |
Laser Fusion Research Center, China
Academy of Engineering Physics
|
Family ID: |
1000004293155 |
Appl. No.: |
16/544965 |
Filed: |
August 20, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24B 41/02 20130101;
B24B 13/0018 20130101; B24B 41/06 20130101; B24B 49/04
20130101 |
International
Class: |
B24B 13/00 20060101
B24B013/00; B24B 41/02 20060101 B24B041/02; B24B 49/04 20060101
B24B049/04; B24B 41/06 20060101 B24B041/06 |
Claims
1. An intelligent continuous polishing machine, the machine
comprises: a rotary platen mounted on a base platen, the base
platen placed on three supporting blocks that are mounted on
ground; a multi-beam bridge mechanism installed above the rotary
platen, the multi-beam bridge mechanism configured with four
horizontal beams. A first linear slide guide configured with a
movable block is installed on one side of the first horizontal
beam, and a second linear slide guide configured with a movable
block is installed on the other side. A third linear slide guide
configured with a movable block is installed on the third
horizontal beam, and a fourth linear slide guide configured with a
movable block is installed on the fourth horizontal beam. A guide
base is installed on the second horizontal beam through an
adjusting structure, and a precision aerostatic slide guide
configured with a movable block is fixed on the guide base; a first
workpiece holding mechanism installed on the movable block of the
first linear slide guide, and a second workpiece holding mechanism
installed on the movable block of the fourth linear slide guide; a
lap measuring mechanism installed on the movable block of the
precision aerostatic slide guide; a lap cutting mechanism installed
on the movable block of the precision aerostatic slide guide; a
small-conditioner holding mechanism installed on the movable block
of the second linear slide guide; a large-conditioner holding
mechanism installed on the movable block of the third linear slide
guide; a control computer that can control every subsystems of the
machine;
2. The machine of claim 1 in which the base platen is configured
with a group of through holes for compressed air at the center
area, compressed air with a preset pressure fed from the lower
ports of the through holes and released from the upper ports to
form a very thin cushion between the rotary platen and base
platen;
3. The machine of claim 1 in which the supporting height of the
three supporting blocks can be adjusted respectively so as to
control the absolute verticality error of the base platen rotary
axis;
4. The machine of claim 1 in which a layer of polishing pitch is
prepared on the top surface of the rotary platen to form a
polishing lap;
5. The machine of claim 1 in which the bottom side of the rotary
platen is processed into a lug section that has a smaller diameter,
a gear ring is installed around the circumference of the lug
section of the rotary platen, and a drive motor assembly is fixed
beside the lug section, the drive gear of the drive motor assembly
matches the gear ring around the lug section so as to rotate the
rotary platen;
6. The machine of claim 1 in which an electronic inclinometer is
mounted on the guide base for determining the inclination of the
guide base and the aerostatic slide guide, the inclination of the
guide base and the aerostatic slide guide can be regulated by the
adjusting structure, and the guide base is made from thermo-stable
materials such as granite assuring precision of the aerostatic
slide guide;
7. The machine of claim 1 in which the workpiece holding mechanism
comprises a supporting frame, three holding wheels, a work ring, a
drive motor and a septum; the supporting frame includes an upper
part fixed on the movable block of the first linear slide guide and
a lower part configured with an opening; the three holding wheels
are installed around the opening of the lower part, and the work
ring placed within the opening is held by the three holding wheels;
a gear belt is installed around the circumference of the work ring,
the drive motor is installed on the lower part of the supporting
frame, and the drive gear of the drive motor matches the gear belt
of the work ring so as to rotate the work ring; the septum is fixed
within the work ring and the workpiece is placed within the septum
during polishing;
8. The machine of claim 1 in which the lap measuring mechanism
comprises a displacement sensor, a featured measuring tool, and a
measuring object; the displacement sensor is fixed on the movable
block of the aerostatic slide guide through an adjustable
connector, they measuring tool includes an upper part fixed on the
movable block of the aerostatic slide guide and a lower part with a
work hole, the measuring object is placed within the work hole; the
measuring tool constrains the measuring object to move across the
lap surface, and the displacement sensor measures the position of
the measurement object that has a single degree of freedom in the
vertical direction;
9. The machine of claim 1 in which the lap cutting mechanism
comprises a fifth linear slide guide configured with a movable
block, a high-speed motor fixed on the movable block, and a cutting
knife installed on the rotor of the high-speed motor; the cutting
knife is driven by the high-speed motor to rotate at a high speed,
so as to cut the lap surface; the movable block is controlled to
move along the fifth linear slide guide in the vertical direction,
so that the cutting depth of the cutting knife into the lap surface
can be controlled instantaneously as the cutting knife moves along
the lap surface radially;
10. The machine of claim 1 in which the small-conditioner holding
mechanism is, configured to rotate the small conditioning tool with
a determined eccentricity under a constant loading, comprising a
drive motor, a drive belt, a pneumatic cylinder configured with a
piston rod, an eccentricity adjusting structure, and a small
conditioning tool; the drive motor rotates the piston rod of the
pneumatic cylinder through the drive belt; the eccentricity
adjusting structure includes an upper column fixed on the piston
rod and a lower column connecting the small, conditioning tool by a
ball joint structure, the eccentricity of the lower column with
respect to the piston rod can be adjusted by the eccentricity
adjusting structure; the applying force of the small conditioning
tool onto the lap surface can be altered and controlled by the
pneumatic cylinder through the piston rod;
11. The machine of claim 1 in which the large-conditioner holding
mechanism comprises a conditioner lifting structure, a large
conditioner, and a drive motor; the conditioner lifting structure
are fixed on one side of the movable block of the third linear
slide guide; the large conditioner is connected to the conditioner
lifting structure while placed on the lap, and the loading force of
the large conditioner onto the lap can be controlled; a gear belt
is installed around the circumference of the large conditioner, the
drive motor is fixed on the other side of the movable block, and
the drive gear of the drive motor matches the gear belt of the
large conditioner so as to rotate the large conditioner;
12. The machine of claim 1 in which the control computer uses
computer numerical controlled (CNC) programs, with proper feedback
from linear and rotary encoders, to allow the accurate positioning
and speed controls;
13. An intelligent continuous polishing process, the process
comprises a normal polishing procedure, a lap measuring procedure,
and three procedures for correcting the lap surface shape error
including a lap cutting procedure, a sub-aperture correcting
procedure, and a full-aperture correcting procedure); all the
procedures are controlled by the control computer though CNC
programs;
14. The process of claim 13 in which the normal polishing procedure
is conducted when polishing the workpiece, comprising: placing the
workpiece on the lap in the septum within the work ring; feeding
abrasive slurry onto the lap surface that is transported to the
polishing site by the slurry channels on the surface; controlling
the rotation of the pitch lap, the rotation and translation of the
work ring;
15. The process of claim 14 in which material is removed from the
workpiece surface by the slurry particles achieving a desired
surface figure;
16. The process of claim 13 in which the lap measuring procedure is
conducted when measuring the surface shape of the pitch lap,
comprising: determining and calculating the reference error of the
lap measuring procedure; measuring the surface shape of the pitch
lap by moving the measurement point of the displacement sensor in a
generally radial direction while the rotary platen rotates;
creating the actual surface shape of the pitch lap according to the
reference error and the lap measuring data; generating the error
map of the pitch lap by comparing the actual surface shape with the
desired surface shape;
17. The process of claim 16 in which the reference error of the lap
measuring procedure is divided into (a) the coupled error of the,
absolute inclination error and straightness error of the aerostatic
slide guide and (b) the absolute verticality error of the lap
rotary axis; the coupled error of the aerostatic slide guide is
determined using ,a displacement sensor fixed on the movable block
of the aerostatic slide guide to measure a water surface as the
movable block, is servo motorized to translate along the aerostatic
slide guide; the absolute verticality error of the lap rotary axis
is determined using an electronic inclinometer placed on a platen
that is mounted on the pitch lap, the absolute verticality error of
the lap rotary axis is derived according to the instantaneous
inclination of the electronic inclinometer passing through the
aerostatic slide guide (q.sub.1) and the opposing side (q.sub.2) on
the rotating pitch lap, q=(q.sub.1-q.sub.2)/2.
18. The process of claim 16 in which the movement of the
displacement sensor can be achieved using the aerostatic slide
guide configured the movable block;
19. The process of claim 16 in which measuring the surface shape of
the pitch lap generates a spiral path with a self-defined pitch and
provides an opportunity to create the entire surface shape with an
interpolation method;
20. The process of claim 13 in which the lap cutting procedure is
implemented by the lap cutting mechanism under the control of the
control computer, comprising deriving the radial profile of the
desired surface that is radial symmetric and generating the moving
profile of the cutting knife can be obtained by integrating the
radial profile of the desired surface and the reference error of
the lap measuring procedure; and further comprising rotating the
pitch lap and the cutting knife and controlling the cutting knife
to move along the pitch lap radially with the moving profile so as
to compensate for the desired lap profile and the reference error
and thus achieve a desired surface shape of the pitch lap in
despite of the initial surface shape;
21. The process of claim 13 in which the sub-aperture correction
procedure is implemented by the small-conditioner holding mechanism
under the control of the control computer, comprising: determining
the actual surface shape of the pitch lap; calculating the surface
shape error according to the actual surface shape and the desired
surface shape; configuring the small conditioning tool and
determining the work function, of the small conditioning tool;
calculating the tool dwell time over the lap surface and the
required motion; executing the calculated conditioning program;
22. The process of claim 21 in which configuring the small
conditioning tool comprises adjusting the eccentricity, rotary
speed, and loading pressure of the small conditioning tool to
obtain work functions of different sizes and profiles; the work
function of the small conditioning tool is obtained by measuring
the surface shape of the pitch lap before and after a determined
working duration time, and the positioning and dwell time of the
small conditioning tool, over the lap surface is implemented by
controlling the rotation of the pitch lap and the radial motion of
the small conditioning tool;
23. The process of claim 13 in which the full-aperture correction
procedure is implemented by the large-conditioner holding mechanism
under the control of the control computer; the large conditioner is
moved outwards a determined distance for correcting a concave
surface shape or inwards a determined distance for correcting a
convex surface shape.
Description
TECHNICAL FIELD
[0001] The present disclosure is related to an optical polishing
machine and process, more particularly, an intelligent continuous
polishing machine and process therefor.
BACKGROUND
[0002] Continuous polishing is one of the most important processes
in fabricating large flat optical elements. The continuous
polishing machine generally consists of a pitch layer prepared on a
substrate platen as the polishing lap. The pitch layer thickness
varies from several millimeters to centimeters. The pitch polishing
lap is usually built into an annular shape with a cut-off inner
area, which commonly has a diameter of about one third of the lap
diameter. On one side of the annular lap are one or more work
rings. The flat optical elements to be polished are placed on the
pitch lap in metal or plastic septums within these work rings. On
the remaining portion of the annular lap is a large circular truing
tool called "conditioner", which commonly has a diameter of about
half of the lap diameter. During continuous polishing, the pitch
lap, work rings and conditioner are driven by servo motors to
rotate counterclockwise at a nearly synchronous rate. Several
patterns of grooves can be cut into the pitch lap so as to improve
the fluidity of the pitch lap and transportation of the slurry on
the pitch lap surface. The abrasive slurry is sprayed onto the
pitch lap surface and transported to the polishing site by the
grooves on the surface. From the combination of the chemical and
mechanical actions of the slurry, micro/nano material removal takes
place, enabling surface finishing to be realized.
[0003] The key point for the continuous polishing process is to
converge the surface figure of the optical elements to a high
precision in a determined manner. The surface shape of the pitch
lap plays an important role in converging the surface figure.
However, the lap surface shape is continuously deteriorated by the
optical elements through squeeze and wears effects. Thus, a large
size conditioner is typically used to develop the desired surface
shape of the pitch lap, that is, to control the surface shape
development of the pitch lap. It is well known that the pitch is a
viscoelastic material. It has the ability to flow by time, enabling
the pitch to creep under the loading of the conditioner. In the
conventional control process, it has been thought that the pitch
lap can be brought to a flat condition that can be maintained for
long periods by adjusting the conditioner's radial position on the
lap. Slight adjustments in the conditioner position are made as
optical elements are found to be slightly convex or concave. The
principal has been thought that when the conditioner is moved
outward, the contact pressure of the pitch lap increases in the
outer zone but decreases in the inner zone, leading the surface
shape of the pitch lap changes convexly. However, this process
depends on operators' skills to achieve the target surface figure,
which is far from to be a determined process.
SUMMARY OF THE DISCLOSURE
[0004] In view of the problems of the prior art, the primary object
of the present disclosure is to provide an intelligent continuous
polishing machine. According to the embodiments of the present
disclosure, the machine comprises a rotary platen, a multi-beam
bridge mechanism, a first workpiece holding mechanism, a lap
measuring mechanism, a lap cutting mechanism, a small-conditioner
holding mechanism and a large-conditioner holding mechanism.
[0005] In one embodiment, the rotary platen is mounted on a base
platen, the base platen is placed on three supporting blocks that
are mounted on ground.
[0006] In one embodiment, the multi-beam bridge mechanism is
installed above the rotary platen, the multi-beam bridge mechanism
is configured with four horizontal beams. A first linear slide
guide configured with a movable block is installed on one side of
the first horizontal beam, and a second linear slide guide
configured with a movable block is installed on the other side. A
third linear slide guide configured with a movable block is
installed on the third horizontal beam, and a fourth linear slide
guide configured with a movable block is installed on the fourth
horizontal beam. A guide base is installed on the second horizontal
beam through an adjusting structure, and a precision aerostatic
slide guide configured with a movable block is fixed on the guide
base.
[0007] In one embodiment, the first workpiece holding mechanism is
installed on the movable block of the first linear slide guide, and
the second workpiece holding mechanism is installed on the movable
block of the fourth linear slide guide.
[0008] In one embodiment, the lap measuring mechanism is installed
on the movable block of the precision aerostatic slide guide.
[0009] In one embodiment, the lap cutting mechanism is installed on
the movable block of the precision aerostatic slide guide.
[0010] In one embodiment, the small-conditioner holding mechanism
is installed on the movable block of the second linear slide
guide.
[0011] In one embodiment, the large-conditioner holding mechanism
is installed on the movable block of the third linear slide
guide.
[0012] In one embodiment, the control computer can control every
subsystems of the machine.
[0013] In one embodiment, the base platen is provided with a group
of through holes for compressed air at the center area, compressed
air with a preset pressure fed from the lower ports of the through
holes and released from the upper ports to form a very thin cushion
between the rotary platen and base platen.
[0014] In one embodiment, the supporting height of the three
supporting blocks can be adjusted respectively so as to control the
absolute verticality error of the base platen rotary axis.
[0015] In one embodiment, the layer of polishing pitch is prepared
on the top surface of the rotary platen to form a polishing
lap.
[0016] In one embodiment, the bottom side of the rotary platen is
processed into a lug section that has a smaller diameter, a gear
ring is installed around the circumference of the lug section of
the rotary platen, and a drive motor assembly is fixed beside the
lug section, the drive gear of the drive motor assembly matches the
gear ring around the lug section so as to rotate the rotary
platen.
[0017] In one embodiment, an electronic inclinometer is mounted on
the guide base for determining the inclination of the guide base
and the aerostatic slide guide, the inclination of the guide base
and the aerostatic slide guide can be regulated by the adjusting
structure, and the guide base is made from thermo-stable materials
such as granite assuring precision of the aerostatic slide
guide.
[0018] In one embodiment, the workpiece holding mechanism comprises
a supporting frame, three holding wheels, a work ring, a drive
motor and a septum. The supporting frame includes an upper part
fixed on the movable block of the first linear slide guide and a
lower part configured with an opening. The three holding wheels are
installed around the opening of the lower part, and the work ring
placed within the opening is held by the three holding wheels. A
gear belt is installed around the circumference of the work ring,
the drive motor is installed on the lower part of the supporting
frame, and the drive gear of the drive motor matches the gear belt
of the work ring so as to rotate the work ring. The septum is fixed
within the work ring and the workpiece is placed within the septum
during polishing.
[0019] In one embodiment, the lap measuring mechanism comprises
displacement sensor, a featured measuring tool, and a measuring
object.
[0020] In one embodiment, the displacement sensor is fixed on the
movable block of the aerostatic slide guide through an adjustable
connector;
[0021] In one embodiment, the measuring tool includes an upper part
fixed on the movable block of the aerostatic slide guide and a
lower part with a work hole, the measuring object is placed within
the work hole.
[0022] In one embodiment, the measuring tool constrains the
measuring object to move across the lap surface, and the
displacement sensor measures the position of the measurement object
that has a single degree of freedom in the vertical direction.
[0023] In one embodiment, the lap cutting mechanism comprises a
fifth linear slide guide configured with a movable block, a
high-speed motor fixed on the movable block, and a cutting knife
installed on the rotor of the high-speed motor.
[0024] In one embodiment, the cutting knife is driven by the
high-speed motor to rotate at a high speed so as to cut the lap
surface. The movable block is controlled to move along the fifth
linear slide guide in the vertical direction, so that the cutting
depth of the cutting knife into the lap surface can be controlled
instantaneously as the cutting knife moves along the lap surface
radially.
[0025] In one embodiment, the small-conditioner holding mechanism
is configured to rotate the small conditioning tool with a
determined eccentricity under a constant loading, comprising a
drive motor, a drive belt, a pneumatic cylinder configured with a
piston rod, an eccentricity adjusting structure, and a small
conditioning tool.
[0026] The drive motor rotates the piston rod of the pneumatic
cylinder through the drive belt.
[0027] The eccentricity adjusting structure includes an upper
column fixed on the piston rod and a lower column connecting the
small conditioning tool by a ball joint structure, the eccentricity
of the lower column, with respect to the piston rod can be adjusted
by the eccentricity adjusting structure.
[0028] The applying force of the small conditioning tool onto the
lap surface can be altered and controlled by the pneumatic cylinder
through the piston rod.
[0029] In one embodiment, the large-conditioner holding mechanism
comprises a conditioner lifting structure, a large conditioner, and
a drive motor. The conditioner lifting structure is fixed on one
side of the movable block of the third linear slide guide. The
large conditioner is connected to the conditioner lifting structure
while placed on the lap, and the loading force of the large
conditioner onto the lap can be controlled.
[0030] In one embodiment, a gear belt is installed around the
circumference of the large conditioner, the drive motor is fixed on
the other side of the movable block, and the drive gear of the
drive motor matches the gear belt of the large conditioner so as to
rotate the large conditioner.
[0031] In one embodiment, the control computer uses computer
numerical controlled (CNC) programs, with proper feedback from
linear and rotary encoders, to allow the accurate positioning and
speed controls.
[0032] The present disclosure further provides an intelligent
continuous polishing process, the process comprises a normal
polishing procedure, a lap measuring procedure, and three
procedures for correcting the lap surface shape error including a
lap cutting procedure, a sub-aperture correcting procedure, and a
full-aperture correcting procedure. All the procedures are
controlled by the control computer through CNC programs.
[0033] The normal polishing procedure is conducted when polishing
the workpiece, which comprises:
[0034] placing the workpiece on the lap in the septum within the
work ring;
[0035] feeding abrasive slurry onto the lap surface that is
transported to the polishing site by the slurry channels on the
surface;
[0036] controlling the rotation of the pitch lap, the rotation and
translation of the work ring.
[0037] Material is removed from the workpiece surface by the slurry
particles achieving a desired surface figure.
[0038] The lap measuring procedure is conducted when measuring the
surface shape of the pitch lap, which comprises:
[0039] determining and calculating the reference error of the lap
measuring procedure;
[0040] measuring the surface shape of the pitch lap by moving the
measurement point of the displacement sensor in a generally radial
direction while the rotary platen rotates;
[0041] creating the actual surface shape of the pitch lap according
to the reference error and the lap measuring data;
[0042] generating the error map of the pitch lap by comparing the
actual surface shape with the desired surface shape.
[0043] The reference error of the lap measuring procedure is
divided into (a) the coupled error of the absolute inclination
error and straightness error of the aerostatic slide guide and (b)
the absolute verticality error of the lap rotary axis.
[0044] The coupled error of the aerostatic slide guide is
determined using a displacement sensor fixed on the movable block
of the aerostatic slide guide to measure a water surface as the
movable block is servo motorized to translate along the aerostatic
slide guide.
[0045] The absolute verticality error of the lap rotary axis is
determined using an electronic inclinometer placed on a platen that
is mounted on the pitch lap, the absolute verticality error of the
lap rotary axis is derived according to the instantaneous
inclination of the electronic inclinometer passing through, the
aerostatic slide guide (q.sub.1) and the opposing side (q.sub.2) on
the rotating pitch lap, i.e., q=(q.sub.1-q.sub.2)/2.
[0046] The movement of the displacement sensor can be achieved
using the aerostatic slide guide configured the movable block.
[0047] The step of measuring the surface shape of the pitch lap
generates a spiral path with a self-defined pitch and provides an
opportunity to create the entire surface shape with an
interpolation method.
[0048] The lap cutting procedure is implemented by the lap cutting
mechanism under the control of the control computer, which
comprises deriving the radial profile of the desired surface that
is radial symmetric and generating the moving profile of the
cutting knife which can be obtained by integrating the radial
profile of the desired surface and the reference error of the lap
measuring procedure.
[0049] The lap cutting procedure further comprises rotating the
pitch lap and the cutting knife and controlling the cutting knife
to move along the pitch lap radially with the moving profile so as
to compensate for the desired lap profile and the reference error
and thus achieve a desired surface shape of the pitch lap in
despite of the initial surface shape.
[0050] The sub-aperture correction procedure is implemented by the
small-conditioner holding mechanism under the control of the
control computer, which comprises:
[0051] determining the actual surface shape of the pitch lap;
[0052] calculating the surface shape error according to the actual
surface shape and the desired surface shape,
[0053] configuring the small conditioning tool and determining the
work function of the small conditioning tool;
[0054] calculating the tool dwell time over the lap surface and the
required motion;
[0055] executing the calculated conditioning program.
[0056] The step of configuring the small conditioning tool
comprises adjusting the eccentricity, rotary speed, and loading
pressure of the small conditioning tool to obtain work functions of
different sizes and profiles; the work function of the small
conditioning tool is obtained by measuring the surface shape of the
pitch lap before and after a determined working duration time, and
the positioning and dwell time of the small conditioning tool over
the lap surface is implemented by controlling the rotation of the
pitch lap and the radial motion of the small conditioning tool.
[0057] The full-aperture correction procedure is implemented by the
large-conditioner holding mechanism under the control of the
control computer. The large conditioner is moved outwards a
determined distance for correcting a concave surface shape or
inwards a determined distance for correcting a convex surface
shape.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] FIG. 1 is a perspective view of an intelligent continuous
polishing machine as viewed downward.
[0059] FIG. 2 is a perspective view of part of an intelligent
continuous polishing machine as viewed upward.
[0060] FIG. 3 is a perspective view of the workpiece holding
mechanism.
[0061] FIG. 4 is a perspective view of the lap measuring and
cutting mechanisms.
[0062] FIG. 5 is a perspective view of the small-conditioner
holding mechanism.
[0063] FIG. 6 is a perspective view of the large-conditioner
holding mechanism.
[0064] FIG. 7 is a diagram of configurations for determining the
coupled error of the aerostatic slide guide.
[0065] FIG. 8 is a diagram of configurations for determining the
absolute verticality error of the lap rotary axis.
[0066] FIG. 9 is a diagram of the absolute verticality error of the
lap rotary axis.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0067] Referring to FIGS. 1 and 2, the intelligent continuous
polishing machine 100 includes a rotary platen 2 mounted on a base
platen 1. The base platen 1 is configured with a group of through
holes for compressed air at the center area. Compressed air with a
preset pressure is fed from the lower ports of the through holes
and released from the upper ports to form a very thin cushion
between the rotary platen 2 and base platen 1, so that the rotary
platen 2 rides on the thin cushion of compressed air. The top
surface of the base platen 1 and the bottom surface of the rotary
platen 2 have a high precision surface shape so that the thin
cushion of compressed air can be formed.
[0068] The base platen 1 is placed on three supporting blocks 11
that are mounted on ground. The supporting height of the three
supporting blocks 11 can be adjusted respectively so as to control
the absolute verticality error of the base platen 1 rotary
axis.
[0069] A layer of polishing pitch is prepared on the top surface of
the rotary platen 2 to form a polishing lap 21. The bottom side of
the rotary platen 2 is processed into a lug section 22 that has a
smaller diameter. A gear ring 23 is installed around the
circumference of the lug section 22. A drive motor assembly 24 is
fixed beside the lug section 22, and the drive gear 241 of the
drive motor assembly 24 matches the gear ring 23 around the lug
section 22 so as to rotate the rotary platen 2.
[0070] This unique design of air bearing and gear ring driving
configuration has significant advantages. It virtually eliminates
vibration at the polishing surface, and dramatically improves
workpiece figure and finish results. In addition, the axial and
radial runout error of the rotary platen 2 during operation is
small which is required for the measuring the surface shape of the
pitch lap 21.
[0071] Referring to Figs. ,1 and 2, the intelligent continuous
polishing machine 100 includes a multi-beam bridge mechanism 3
installed above the rotary platen 2. The multi-beam bridge
mechanism 3 is configured with four horizontal beams 31-34. A first
linear slide guide 4 configured with a movable block 41 is
installed on one side of the first horizontal beam 31, and a second
linear slide guide 5 configured with a movable block 51 is
installed on the other side. A third linear slide guide 7
configured with a movable block 71 is installed on, the third
horizontal beam 33, and a fourth linear slide guide 8 configured
with a movable block 81 is installed on the fourth horizontal beam
34.
[0072] A guide base 321 is installed on the second horizontal, beam
32 through an adjusting structure 322. A precision aerostatic slide
guide 6 configured with a movable block 61 is fixed on the guide
base 321. An electronic inclinometer 323 is mounted on the guide
base 321 for determining the inclination of the guide base 321 and
the aerostatic slide guide 6. The inclination of the guide base 321
and the aerostatic slide guide 6 can be regulated by the adjusting
structure 322. The guide base 321 is made from thermo-stable
materials such as granite assuring precision of the aerostatic
slide guide 6. The movable block 61 can be controlled to move along
the aerostatic slide guide 6.
[0073] Referring to FIG. 3, the intelligent continuous polishing
machine 100 includes a first workpiece holding mechanism 90
installed on the movable block 41 of the first linear slide guide
4. The workpiece holding mechanism 90 comprises: a supporting frame
901, three holding wheels 902, a work ring 903, a septum 904 and a
drive motor 905. The supporting frame 901 includes an upper part
906 fixed on the movable block 41 of the first linear slide guide 4
and a lower part 907 configured with an opening. The three holding
wheels 903 are installed around the opening of the lower part 907,
and the work ring 903 placed within the opening is held by the
three holding wheels 902. A gear belt 908 is installed around the
circumference of the work ring 903. The drive motor 905 is
installed on the lower part 907 of the supporting frame 901, and
the drive gear of the drive motor 905 matches the gear belt 908 of
the work ring 902 so as to rotate the work ring 903. The septum 904
is fixed within the work ring 903, and the workpiece is placed
within the septum 904 during polishing.
[0074] The intelligent continuous polishing machine 100 includes a
second workpiece holding mechanism 91 installed on the movable
block 81 of the fourth linear slide guide 8. The configuration of
the second workpiece holding mechanism 91 is the same as the first
workpiece holding mechanism 90.
[0075] This unique design of workpiece holding mechanism
configurations has significant advantages. The work ring and the
septum are not placed on the pitch lap, which avoid deteriorate the
surface shape of the pitch lap.
[0076] Referring to FIG. 4, the intelligent continuous polishing
machine includes a lap measuring mechanism 92 installed on the
movable block 61 of the precision aerostatic slide guide 6. The lap
measuring mechanism 92 includes a displacement sensor 921, a
featured measuring tool 922 and a measuring object 923. The
displacement sensor 921 is fixed on the movable block 61 through an
adjustable connector 924. The measuring tool 922 includes an upper
part fixed on the movable block 61 and a lower part with a work
hole. The measuring object 923 is placed within the work hole.
[0077] The pitch lap 21 contains slurry channels that cause
discontinuities on the surface. The measuring object 923 is used as
a means to bridge small discontinuities on the lap surface and
provide physical averaging for the lap surface. The measuring
object 923 has a smooth surface that is in contact with the lap
surface, and the dimensions of the smooth surface are larger than
the maximum width of the channels. The measuring tool 922 is
configured to constrain the measuring object 923 to move across the
lap surface, and the displacement sensor 921 is configured to
measure the position of the measurement object 923 that has a
single degree of freedom in the vertical direction.
[0078] Referring to FIG. 4, the intelligent continuous polishing
machine 100 includes a lap cutting mechanism 93 installed on the
movable block 61 of the precision aerostatic slide guide 6. The lap
cutting mechanism 93 comprises: a fifth linear slide guide 931
configured with a movable block 932, a high-speed motor 933 fixed
on the movable block 932, and a cutting knife 934 installed on the
rotor of the high-speed motor 933. The cutting knife 934 is driven
by the high-speed motor 933 to rotate at a high speed so as to cut
the lap surface. The movable block 932 is controlled to move along
the fifth linear slide guide 931 in the vertical direction, so that
the cutting depth of the cutting knife 934 into the lap surface can
be controlled instantaneously as the cutting knife 934 moves along
the lap surface radially.
[0079] Referring to FIG. 5, the intelligent continuous polishing
machine 100 includes a small-conditioner holding mechanism 94
installed on the movable block 51 of the second linear slide guide
5. The small-conditioner holding mechanism 94 comprises: a drive
motor 941, a drive belt 942, a pneumatic cylinder 943 configured
with a piston rod 944, an eccentricity adjusting structure 945, and
a small conditioning tool 946. The drive motor 941 rotates the
piston rod 944 of the pneumatic cylinder 943 through the drive belt
942. The eccentricity adjusting structure 945 includes an upper
column fixed on the piston rod 944 and a lower column connecting
the small conditioning tool 946 by a ball joint structure. The
eccentricity of the lower column with respect to the piston rod 944
can be adjusted by the eccentricity adjusting structure 945. The
applying force of the small conditioning tool 946 onto the lap
surface can be altered and controlled by the pneumatic cylinder 943
through the piston rod 944. The small-conditioner holding mechanism
94 is configured to rotate the small conditioning tool 946 with a
determined eccentricity under a constant loading.
[0080] This unique design of the small-conditioner holding
mechanism 94 has significant advantages. The small conditioning
tool 946 rotating with an eccentricity is beneficial to generating
a work function of desired profile, and the small conditioning tool
946 controlled by the pneumatic cylinder 943 under a determined
pneumatic pressure is beneficial to keeping a stable work function.
Further, the size and magnitude of the work function can be altered
by adjusting the eccentricity of the small conditioning tool 946
and changing the pneumatic pressure of the pneumatic cylinder
943.
[0081] Referring to FIG. 6, the intelligent continuous polishing
machine 100 includes a large-conditioner holding mechanism 95
installed on the movable block 71 of the third linear slide guide
7. The large-conditioner holding mechanism 95 comprises: a
conditioner lifting structure 951, a large conditioner 952, and a
drive motor 953.
[0082] The conditioner lifting structure 951 are fixed on one side
of the movable block 71. The large conditioner 952 is connected to
the conditioner lifting structure 951 while placed on the lap, and
the loading force of the large conditioner 952 onto the lap can be
controlled by the conditioner lifting structure 951. A gear belt
954 is installed around the circumference of the large conditioner
952. The drive motor 953 is fixed on the other side of the movable
block 71, and the drive gear of the drive motor 953 matches the
gear belt 954 of the large conditioner 952 so as to rotate the
large conditioner 952. The large-conditioner holding mechanism 95
installed the movable block 71 can be controlled to move radially
along the third linear slide guide 7.
[0083] Referring to FIG. 1, the intelligent continuous polishing
machine 100 includes a control computer 200 that can control every
subsystems of the machine 100, including: 1) accurate angular
positioning and rotary speed of the rotary platen 2 and the pitch
lap 21 through the drive motor assembly 24; 2) accurate radial
positioning and rotary speed of the work ring 903 and the workpiece
10 through the first linear slide guide 4 and the drive motor 905;
3) accurate radial positioning and rotary speed of the large
conditioner 952 through the third linear slide guide 7 and the
drive motor 953; 4) accurate radial positioning and translation
speed of the measuring tool 922 in the lap measuring mechanism
through, the aerostatic slide guide 6; 5) accurate height
positioning and rotary speed of the cutting knife 934 through the
fifth linear slide guide 931 and the high-speed motor 933; 6)
accurate radial positioning and translation speed of the small
conditioning tool 946 through the second linear slide guide 5; 7)
accurate pressure of the small conditioning tool 946 through the
pneumatic cylinder 943.
[0084] Computer numerical controlled (CNC) programs can be used,
with proper feedback from linear and rotary encoders, to allow
these accurate positioning and speed controls.
[0085] An intelligent continuous polishing process includes a
normal polishing procedure, a lap measuring procedure, and three
procedures for correcting the lap surface shape error: a lap
cutting procedure, a sub-aperture correcting procedure, and a
full-aperture correcting procedure. All of these procedures are
controlled by the control computer 200 through CNC programs.
[0086] The normal polishing procedure is conducted when polishing
the workpiece. During the normal polishing procedure, the workpiece
100 to be polished is placed on the lap 21 in the septum 904 within
the work ring 903. The computer 200 controls the rotation of the
pitch lap 21, the rotation and translation of the work ring 903,
and sometimes the rotation and translation of the large conditioner
952 if the full-aperture correction procedure is being conducted
simultaneously. The abrasive slurry is fed onto the lap surface and
transported to the polishing site by the slurry channels on the
surface. Material is removed from the workpiece surface by the
slurry particles, achieving a desired surface figure.
[0087] The surface figure of the workpiece primarily depends on the
surface shape of the pitch lap 21. When the surface figure
deteriorates and does not meet the required specifications, one can
consider measuring and correcting the surface shape of the pitch
lap 21.
[0088] The lap measuring procedure is conducted when measuring the
surface shape of the pitch lap 21. The lap surface shape can be
measured by moving the measurement point of the displacement sensor
921 in a generally radial direction while the rotary platen 2
rotates. The movement of the displacement sensor 921 can be
achieved using the aerostatic slide guide 6 configured with the
movable block 61. It generates a spiral path with a self-defined
pitch and provides an opportunity to interrogate the entire lap
surface efficiently and repeatedly. When the radial motion of the
displacement sensor 921 and the rotary motion of the lap 21 are
servo controlled or monitored using encoder feedback, the exact
position on the lap surface for every measurement can be obtained
with precision.
[0089] The reference for measuring the lap surface shape is the
aerostatic slide guide 6. The aerostatic slide guide 6 is
positioned almost perpendicular to the lap rotary axis, but it
wouldn't be perfectly perpendicular. The slide perpendicularity
error with respect to the lap rotary axis should be considered
because it is interpreted as a tapered shape error in the lap 21.
Furthermore, as the displacement sensor 921 fixed on the movable
block 61 is servo motorized to translate along the aerostatic slide
guide 6 while moving across the lap surface, the straightness error
of the aerostatic slide guide 6 is also interpreted as the shape
error in the lap. Thus, the reference error of the lap measuring
procedure includes the slide perpendicularity error with respect to
the lap rotary axis and the slide straightness error. The slide
perpendicularity error with respect to the lap rotary axis can be
decomposed into the absolute inclination error of the slide
mechanism and the absolute verticality error of the lap rotary
axis. The coupled error of the absolute inclination error and
straightness error of the aerostatic slide guide 6 can be
determined using the displacement configured as FIG. 7. The
absolute verticality error of the lap rotary axis can be determined
using an electronic inclinometer configured as FIG. 8.
[0090] Referring to FIG. 7, it is configured to determine the
coupled error of the absolute inclination error and straightness
error of the aerostatic slide guide 6. A tank 300 filled with water
is placed under the aerostatic slide guide 6 on the lap 10. The
displacement sensor 921 fixed on the movable block 61 of the
aerostatic slide guide 6 is configured to measure the water surface
as the movable block is servo motorized to translate along the
aerostatic slide guide 6. As the water surface that is almost
horizontal would not introduce external errors, the measured error
is exactly the coupled error of the absolute inclination error and
straightness error of the aerostatic slide guide 6.
[0091] Referring to FIG. 8, it is configured to determine the
absolute verticality error of the lap rotary axis. An electronic
inclinometer 25 is placed on a platen 26 that is mounted on the
pitch lap 21, and the electronic inclinometer 25 is oriented to the
lap center. The pitch lap 21 is servo motorized to, rotate at a
constant rotary speed. The instantaneous inclination is recorded
when the electronic inclinometer 25 passes through the aerostatic
slide guide 6 as well as the opposing side, i.e., q.sub.1 and
q.sub.2. Then, the absolute verticality error of the lap rotary
axis can be attained, i.e., q=(q.sub.1-q.sub.2)/2.
[0092] Referring to FIG. 9, the absolute verticality error of the
lap rotary axis could be oriented to any direction. However, it can
be divided into two components. One is in a first vertical plane
within the aerostatic slide guide 6 (YOZ plane), while the other is
in a second vertical, plane perpendicular to the aerostatic slide
guide 6 (XOZ plane). Only the component of the absolute verticality
error in the first vertical plane, that can be determined with the
process above, affects the measured surface shape of the pitch lap
21.
[0093] The absolute verticality error of the lap rotary axis can be
improved. As the rotary platen 2 and base platen 1 are placed on
the three supporting blocks 11 that are mounted on ground, the
supporting height of the three supporting blocks 11 can be adjusted
respectively so as to control the absolute verticality error of the
lap rotary axis. Also, the absolute inclination error of the
aerostatic guide 6 can be regulated using the adjustment structure
322. Then, the slide perpendicularity error with respect to the lap
rotary axis can be eliminated.
[0094] In some implementations, measuring the surface shape of the
pitch lap 21 involves the following steps: (a) determination of the
coupled error of the aerostatic slide guide 6; (b) determination of
the absolute verticality error of the lap rotary axis; (c)
calculation of the reference error of the lap measuring procedure;
(d) measurement of the surface shape of the pitch lap 21; (e)
creation of the actual surface shape of the pitch lap 21 according
to the reference error and the lap measuring data. An error map
(e.g., surface shape error) of the pitch lap 21 is generated by
comparing the actual surface shape with the desired surface shape.
After the reference error of the lap measuring procedure and the
error map of the pitch lap 21 are obtained, one can correct the
surface shape error of the pitch lap 21 with one or some of the
three correction procedures.
[0095] The lap cutting procedure is implemented by the lap cutting
mechanism 93 under the control of the control computer 200. First,
a radial profile of the desired surface that is radial symmetric is
derived, and the moving profile of the cutting knife 934 can be
obtained by integrating the radial profile of the desired surface
and the reference error of the lap measuring procedure
[0096] During the lap cutting procedure, the pitch lap 21 is
rotated by the drive motor assembly 24 at a determined low speed.
The lap cutting mechanism 93 fixed on the movable block 61 of the
aerostatic slide guide 6 is controlled to move along the pitch lap
21 radially, and the high-speed motor 933 fixed on the movable
block 932 of the fifth slide guide 931 rotates the cutting knife
934 at a determined high speed to cut the pitch lap surface. The
cutting height of the cutting knife 934 moving along the pitch lap
21 radially is controlled with the moving profile through the fifth
slide guide 931 and the movable block 932, so as to compensate for
the desired lap profile and the reference error. Thus a desired
surface shape can be achieved for the pitch lap 21 in despite of
the initial surface shape.
[0097] The sub-aperture correction procedure is implemented by the
small-conditioner holding mechanism 94 under the control of the
control computer 200. During the sub-aperture correction procedure,
the small conditioning tool 946 is rotated by the drive motor 941
at a determined speed and is applied onto the lap surface by the
pneumatic cylinder 943 at a determined loading pressure so as to
achieve a stable work function. The eccentricity, rotary speed, and
loading pressure of the small conditioning tool 946 can be varied
to obtain work functions of different sizes and profiles. The work
function of the small conditioning tool 946 can be obtained by
measuring the surface shape of the pitch lap 21 before and after a
determined working duration time. With the work function, the
surface shape error of the pitch lap 21 can be corrected by
controlling the dwell time of the small conditioning tool 946 over
the lap surface. Then, the desired surface shape can be achieved.
The positioning and dwell time of the small conditioning tool 946
over the lap surface can be implemented, by controlling the
rotation of the pitch lap 21 and the radial motion of the small
conditioning tool 946.
[0098] In some implementations, correcting the surface shape error
of the pitch lap 21 by the sub-aperture correction procedure
involves the following steps: (a) determination of the actual
surface shape of the pitch lap 21; (b) calculation of the surface
shape error, according to the actual surface shape and the desired
surface shape; c) determination of the work function of the small
conditioning tool 946; (d) calculation of the tool dwell time over
the lap surface and the required motion; e) execution of the
calculated conditioning program. These steps can be repeated
continuously to achieve a desired surface shape of the pitch lap
21.
[0099] The full-aperture correction procedure is implemented by the
large-conditioner holding mechanism 95 under the control of the
control computer 200. During the full-aperture correction
procedure, the large conditioner 952 is loaded on the pitch lap 21
with a radial eccentricity (e.g., the distance of the conditioner
and lap centers), thus the pitch lap 21 made from viscoelastic
polishing pitch would creep and the surface shape of the pitch lap
21 would changes.
[0100] The radial eccentricity of the large conditioner 952 has a
significant effect on the surface shape of the pitch lap 21. When
the radial eccentricity of the large conditioner 952 is increased,
that is, the large conditioner 952 is moved outward, the contact
pressure at the outer zone increases but that at the inner zone
decreases. Thus, the surface shape of the pitch lap 21 becomes more
convex or less concave, or vice versa. After the surface shape
error of the pitch lap 21 is obtained, the adjustments of the
radial eccentricity of the large conditioner 952 can be made to
correct the surface shaper error. A convex surface shape error of
the pitch lap 21 can be corrected by decreasing the radial
eccentricity, while a concave surface shape error can be corrected
by increasing the radial eccentricity. The full-aperture correction
procedure can be conducted during the normal polishing process.
* * * * *