U.S. patent application number 12/845149 was filed with the patent office on 2011-02-03 for polishing method for a workpiece and polishing tool used for the polishing method.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Kenichi Masuyama.
Application Number | 20110028074 12/845149 |
Document ID | / |
Family ID | 43033624 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110028074 |
Kind Code |
A1 |
Masuyama; Kenichi |
February 3, 2011 |
POLISHING METHOD FOR A WORKPIECE AND POLISHING TOOL USED FOR THE
POLISHING METHOD
Abstract
Provided is a polishing tool capable of forming a high-quality
surface of a workpiece for a short period of time. A polishing tool
includes: a rotation shaft arranged parallel to a sending direction
of moving the polishing tool relative to a workpiece; and at least
two polishing bodies. The polishing body includes a foamed resin
such as a foamed polyurethane resin, and has an outer peripheral
surface having a porosity higher than that of the polishing body.
The polishing body includes a non-foamed resin such as a non-foamed
polyurethane resin being a material more rigid than that for the
polishing body. When polishing-processing, the polishing body
performs polishing removal on a surface of the workpiece, and the
polishing body smoothes a waviness formed on the surface through
the polishing removal.
Inventors: |
Masuyama; Kenichi;
(Saitama-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
1290 Avenue of the Americas
NEW YORK
NY
10104-3800
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
43033624 |
Appl. No.: |
12/845149 |
Filed: |
July 28, 2010 |
Current U.S.
Class: |
451/57 ;
451/65 |
Current CPC
Class: |
B24B 41/002 20130101;
B24B 27/0076 20130101; B24D 13/20 20130101; B24D 5/10 20130101;
B24D 13/02 20130101; B24D 5/066 20130101 |
Class at
Publication: |
451/57 ;
451/65 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2009 |
JP |
2009-181085 |
Claims
1. A polishing tool for polishing-processing a surface of a
workpiece, comprising: a rotation shaft; a disk-like first
polishing body, which is provided to the rotation shaft and
includes an outer peripheral surface serving as a work surface; and
a disk-like second polishing body, which is provided to the
rotation shaft so as to be adjacent to the first polishing body and
includes an outer peripheral surface serving as a work surface,
wherein: the outer peripheral surface of the first polishing body
is formed into a shape having a porosity higher than a porosity of
the outer peripheral surface of the second polishing body; and the
second polishing body comprises a material more rigid than a
material for the first polishing body.
2. The polishing tool according to claim 1, further comprising a
support member provided for deformation prevention on a side
surface of at least one of the first polishing body and the second
polishing body.
3. The polishing tool according to claim 1, wherein the first
polishing body comprises a foamed resin.
4. The polishing tool according to claim 1, wherein the outer
peripheral surface of the second polishing body comprises multiple
grooves formed parallel to a direction of the rotation shaft.
5. A workpiece processing method for polishing-processing a surface
of a workpiece, comprising: bringing a disk-like first polishing
body and a disk-like second polishing body into press-contact with
a workpiece, the first polishing body and the second polishing body
being adjacently provided to a same rotation shaft and each
including an outer peripheral surface serving as a work surface;
and moving the first polishing body and the second polishing body
relative to the workpiece in a direction parallel to the rotation
shaft, to thereby process the surface of the workpiece, wherein:
the outer peripheral surface of the first polishing body is formed
into a shape having a porosity higher than a porosity of the outer
peripheral surface of the second polishing body; the second
polishing body comprises a material more rigid than a material for
the first polishing body; and the second polishing body removes a
waviness formed through processing performed by the first polishing
body.
6. The workpiece processing method according to claim 5, wherein
the second polishing body is arranged, with respect to the first
polishing body, upstream in a direction of moving the first
polishing body and the second polishing body.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polishing method and a
polishing tool used for polishing workpieces including an optical
element such as a lens or a mirror, and a die for molding an
optical element.
[0003] 2. Description of the Related Art
[0004] Nowadays, in a case of finish-polishing a surface shape of a
so-called non-axisymmetric free-form surface different in curvature
at each point of a workpiece including an optical element such as a
lens or a mirror, and a die for molding an optical element, the
polishing-processing is performed with use of a polishing tool
having a contact area smaller than an area of a surface of the
workpiece. The polishing tool has a configuration having a
disk-like polishing body provided onto a rotation shaft, and is
mounted to a polishing apparatus. When the polishing-processing is
performed by the polishing tool of this type, an outer peripheral
surface of the polishing body is brought into press-contact with
the surface of the workpiece at a constant pressure while the
polishing body is rotated at a constant rpm, and then a sending
speed in a forwarding direction is changed based on a standstill
period of time calculated in accordance with a removal depth, to
thereby partially remove the surface of the workpiece to an
arbitrary depth while forming a straight groove. Then, the
workpiece or the polishing tool is shifted by a sending pitch in a
direction orthogonal to the sending direction, and portions to be
removed in this way are partially overlapped to each other, whereby
an entire surface of the workpiece is polishing-processed into an
arbitrary shape. At this time, a polishing removal amount r is
varied as shown in the following Preston's empirical formula.
r=P.times.V.times.K.times.T
[0005] Note that, r represents a polishing removal amount, P
represents a pressure, V represents a relative speed between the
polishing tool and the surface of the workpiece, K represents a
process variable (including a material and an outer peripheral
surface state of the polishing tool), and T represents a standstill
period of time. It is known that, when polishing removal is
performed based on the above-mentioned formula, due to the
pressure, the speed, and a distribution of a tool surface property
in one-rotation cycle of the polishing tool, a waviness in the
one-rotation cycle of the polishing tool is generated on the
surface of the workpiece and thus quality of the surface of the
workpiece such as the optical element is degraded. This is because,
due to the pressure, a tool rotation speed, a pore area
distribution of a polishing body surface, and a thickness
distribution during one-rotation of the tool, process variation in
one-rotation cycle of the tool occurs. For that reason,
conventionally, degrading of the quality of the surface of the
workpiece such as the optical element is suppressed in the
following manner. Specifically, after the polishing tool is scanned
in an X axis direction and the surface of the workpiece is
polished, polishing-processing is performed again with use of a
different polishing tool, or the same polishing tool is scanned in
a Y axis direction orthogonal to the X axis direction to polish the
surface of the workpiece, to thereby smooth the waviness (see
Japanese Patent Application Laid-Open No. H11-090806).
[0006] However, in the above-mentioned conventional method, in
order to smooth the waviness formed on the surface of the workpiece
after performing the polishing-processing by the polishing tool, it
is necessary to perform the polishing-processing again with use of
a different polishing tool, and hence a polishing period of time is
extended. As a result, productivity of the workpiece such as the
optical element is reduced, and manufacturing cost of the workpiece
is adversely affected.
[0007] Further, in the above-mentioned conventional method, though
it is possible to reduce the waviness formed on the surface of the
workpiece, the surface of the workpiece is polishing-processed
multiple times with the same polishing body. Thus, a target shape
is not sometimes obtained so that the quality of the surface of the
workpiece such as the optical element is degraded. For example,
depending on a processing condition, polishing liquid does not
enter uniformly between the polishing body and the workpiece so
that polishing removal is sometimes proceeded at variable speed in
contact surfaces between the polishing body and the workpiece. As a
result, a finished surface having polishing removal depths
different from point to point is formed, and thus the quality of
the surface of the workpiece is sometimes degraded.
[0008] Therefore, it is an object of the present invention to
provide a polishing tool capable of forming a high-quality surface
of a workpiece for a short period of time.
SUMMARY OF THE INVENTION
[0009] According to the present invention, there is provided a
polishing tool for polishing-processing a surface of a workpiece,
including; a rotation shaft, a disk-like first polishing body,
which is provided to the rotation shaft and includes an outer
peripheral surface serving as a work surface, and a disk-like
second polishing body, which is provided to the rotation shaft so
as to be adjacent to the first polishing body and includes an outer
peripheral surface serving as a work surface, in which; the outer
peripheral surface of the first polishing body is formed into a
shape having a porosity higher than a porosity of the outer
peripheral surface of the second polishing body, and the second
polishing body includes a material more rigid than a material for
the first polishing body.
[0010] Further, according to the present invention, there is
provided a workpiece processing method for polishing-processing a
surface of a workpiece, including; bringing a disk-like first
polishing body and a disk-like second polishing body into
press-contact with the workpiece, the first polishing body and the
second polishing body being adjacently provided to the same
rotation shaft and each including an outer peripheral surface
serving as a work surface, and moving the first polishing body and
the second polishing body relative to the workpiece in a direction
parallel to the rotation shaft, to thereby process the surface of
the workpiece, in which; the outer peripheral surface of the first
polishing body is formed into a shape having a porosity higher than
a porosity of the outer peripheral surface of the second polishing
body, the second polishing body includes a material more rigid than
a material for the first polishing body, and the second polishing
body removes a waviness formed through processing performed by the
first polishing body.
[0011] According to the present invention, the outer peripheral
surface of the first polishing body is formed into the shape having
the high porosity, and hence a film of polishing liquid is less
likely to be formed between the surface of the workpiece and the
outer peripheral surface of the first polishing body. As a result,
floating of the first polishing body caused by the film is
suppressed, and thus it is possible to achieve high polishing
removal efficiency. Further, the second polishing body different
from the first polishing body includes the material more rigid than
a material for the first polishing body, and hence the outer
peripheral surface of the second polishing body is less likely to
be held in contact with a valley portion of the waviness, but more
likely to be held in contact with a peak portion of the waviness,
whereby the second polishing body has a high performance in
smoothing the waviness. Further, the first polishing body and the
second polishing body, which have different functions from each
other, are adjacently provided to the rotation shaft, and hence it
is possible to perform polishing removal and smoothing of the
waviness at one time. As a result, it is possible to obtain a
high-quality surface of the workpiece for a short period of
time.
[0012] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is an explanation view of a polishing tool according
to a first embodiment of the present invention.
[0014] FIGS. 2A and 2B are explanations view of a polishing tool
according to a second embodiment of the present invention.
[0015] FIGS. 3A, 3B, and 3C are each an explanation view of a
polishing tool according to another embodiment of the present
invention.
DESCRIPTION OF THE EMBODIMENTS
[0016] In the following, embodiments for carrying out the present
invention are described in detail with reference to the
drawings.
First Embodiment
[0017] A polishing apparatus 100 illustrated in FIG. 1 performs
processing, with use of a polishing tool 10 mounted to a polishing
apparatus main body, on a surface of a workpiece W placed on an XY
stage (not shown). The workpiece W has a surface Wa, which is a
flat surface, a spherical surface, or a non-horizontal surface such
as a non-axisymmetric free-form surface. The workpiece W is, for
example, an optical element such as a lens or a mirror, or a die
for molding an optical element. The polishing tool 10 includes a
rotation shaft 1, and at least two disk-like polishing bodies 7, 8
provided to the rotation shaft 1 so as to be adjacent to each
other. The rotation shaft 1 of the polishing tool 10 is fixed to a
tool rotating device of the polishing apparatus 100, whereby the
polishing tool 10 is supported to be rotatable relative to the
polishing apparatus main body. The first polishing body 8 and the
second polishing body 7 respectively have outer peripheral surfaces
serving as working surfaces 8a, 7a. The first polishing body 8 and
the second polishing body 7 are fixed onto the rotation shaft 1
passing through a center portion of each disk-like surface of each
of the polishing bodies. With this configuration, the first
polishing body 8 and the second polishing body 7 are fixed onto the
rotation shaft 1 so as to be adjacent to each other. The polishing
tool 10 is fixed to the tool rotating device 3, and is driven by
the tool rotating device 3 to rotate about the rotation shaft 1.
Then, the polishing tool 10 is brought into press-contact with the
workpiece W, and the first polishing body 8 and the second
polishing body 7 are moved relative to the workpiece W in a
direction parallel to the rotation shaft, whereby processing is
performed. Moving of the polishing bodies is executed, for example,
through moving of the workpiece W with the XY stage (not
shown).
[0018] The polishing apparatus 100 includes a Z column (not shown)
for moving, in upward and downward directions, a support member 4
coupled to the tool rotating device 3. Herein, as illustrated in
FIG. 1, the upward direction is referred to as a Z axis direction,
and the downward direction is referred to as a -Z axis direction.
The polishing apparatus 100 operates in such a manner that the Z
column is lowered in the -Z axis direction while the rotation shaft
1 of the polishing tool 10 is rotated at a constant rpm, and thus
the outer peripheral surfaces 7a, 8a of the respective polishing
bodies 7, 8 of the polishing tool 10, which serve as the working
surfaces, are brought into press-contact with the surface Wa of the
workpiece W. Then, the polishing apparatus 100 regulates a
press-contact force applied onto the surface Wa of the workpiece W,
and a relative speed and a standstill period of time of the outer
peripheral surfaces 7a, 8a of the polishing bodies 7, 8 with
respect to the surface Wa, and thus controls indentation depths of
the respective polishing bodies 7, 8 with respect to the surface Wa
of the workpiece W. Then, under a state in which the respective
polishing bodies 7, 8 are rotated in a pressing direction parallel
to the -Z axis direction while being held in press-contact with the
surface Wa of the workpiece W, the polishing tool 10 or the
workpiece W is sent in a sending direction S which is a moving
direction parallel to the rotation shaft, and thus the following
groove is formed in the surface Wa. Specifically, the groove has a
predetermined cut depth extending straight in the sending direction
S and a predetermined width. As a method of moving the polishing
tool 10 relative to the surface Wa of the workpiece W, the
workpiece W may be moved relative to the polishing tool 10, or the
polishing tool 10 may be moved relative to the workpiece W.
[0019] In the first embodiment, the rotation shaft 1 of the
polishing tool 10 is arranged in parallel to the moving direction
relative to the workpiece W serving as an object to be polished.
Each of the polishing bodies 7, 8 is fixed onto the rotation shaft
1 passing through the center portion of each disk-like surface of
each of the polishing bodies, and is rotated integrally with the
rotation shaft 1 about the center portion.
[0020] The polishing body 8 is a first polishing body made of a
foamed resin, and a large number of pores are formed in the outer
peripheral surface 8a of the polishing body 8. It is preferred that
the foamed resin include a foamed polyurethane resin. In contrast,
the polishing body 7 is a second polishing body made of a
non-foamed resin, and few pores are formed in the outer peripheral
surface 7a of the polishing body 7. In other words, the outer
peripheral surface 8a of the polishing body 8 is formed into a
shape having a porosity higher than that of the outer peripheral
surface 7a of the polishing body 7. It is preferred that the
non-foamed resin include a non-foamed polyurethane resin. The
polishing body 7 includes the non-foamed polyurethane resin, and
hence is more rigid and less likely to be elastically deformed than
the polishing body 8 made of the foamed polyurethane resin. In
other words, the polishing body 8 is less rigid and more likely to
be elastically deformed than the polishing body 7.
[0021] The polishing body 7 is arranged so as to be adjacent to the
polishing body 8, and the polishing body 7 is arranged so as to be
positioned on an upstream side with respect to the polishing body 8
when the relative moving direction between the polishing tool 10
and the workpiece is along the sending direction (X axis
direction). Further, the polishing body 8 is formed to have a
diameter slightly larger than that of the polishing body 7. In
other words, the polishing body 8 is formed to have a radius larger
than that of the polishing body 7 by an amount corresponding to a
difference between an elastic deformation amount of the polishing
body 7 and an elastic deformation amount of the polishing body 8
caused by a pressing pressure applied onto the surface Wa of the
workpiece W. With this shape, the polishing body 7 and the
polishing body 8 are pressed under the same load onto the workpiece
W when the pressure is applied.
[0022] Note that, it is preferred that a thickness of the polishing
body 7 range from 1.0 mm to 1.5 mm. When the thickness is less than
1.0 mm, rigidity of the polishing body 7 is low, and hence the
polishing body 7 is deformed along the shape of the surface Wa of
the workpiece W. Thus, it is impossible to remove the waviness.
When the thickness is more than 1.5 mm, a length including the
thickness of the polishing body 7, the thickness of the polishing
body 8, and an interval between the polishing body 7 and the
polishing body 8 exceeds 4 mm so that a size of a removal trace is
larger than 4 mm. Thus, it is impossible to correct a shape having
a short wavelength, and to obtain necessary processing accuracy.
Further, it is preferred that a thickness of the polishing body 8
be larger than that of the polishing body 7 and that the length
including the thickness of the polishing body 7, the thickness of
the polishing body 8, and the interval between the polishing body 7
and the polishing body 8 be 4 mm or less. When the polishing body 7
is thicker than the polishing body 8, the polishing body 8 cannot
smooth the waviness generated by the polishing body 7. In other
words, the polishing body 8 is formed to be thicker than the
polishing body 7. The thickness of the polishing body refers to a
distance between disk-like surfaces that are side surfaces of the
polishing body crossing perpendicularly to the rotation shaft.
Further, in the first embodiment, it is preferred that an interval
between the adjacent polishing bodies 7, 8 be 0.5 mm or less. This
is to secure the necessary processing accuracy through setting a
total length of the thickness of the polishing body 7, the
thickness of the polishing body 8, and the interval between the
polishing body 7 and the polishing body 8 to be 4 mm or less so as
to set the size of the removal trace to be 4 mm or less. In this
way, the polishing bodies 7, 8 are arranged onto the rotation shaft
1 with the interval.
[0023] With the above-mentioned configuration, when
polishing-processing the surface Wa of the workpiece W with use of
the polishing tool 10, the polishing bodies 7, 8 are lowered in the
-Z axis direction while being rotated in a rotating direction of
the rotation shaft 1, and then the outer peripheral surfaces 7a, 8a
of the polishing bodies 7, 8 are brought into press-contact with
the surface Wa of the workpiece W. The polishing body 8 includes
the foamed polyurethane resin, and hence is rotated while being
elastically deformed and held in close contact with the surface of
the workpiece W.
[0024] Further, the polishing body 8 includes the foamed
polyurethane resin, and hence the large number of pores are formed
in the outer peripheral surface 8a. Thus, polishing liquid
(abrasive grain) easily enters the formed pores. Therefore, it is
possible to suppress formation of a film of the polishing liquid
between the outer peripheral surface 8a of the polishing body 8 and
the surface Wa of the workpiece W, and thus possible to suppress
floating of the polishing body 8 from the surface Wa. Further, the
large number of pores can hold a large amount of abrasive grains so
that the number of the abrasive grains supplied between the outer
peripheral surface 8a of the polishing body 8 and the surface Wa of
the workpiece W is increased. As a result, polishing removal
efficiency is increased. Though the surface Wa of the workpiece W
is polished by the polishing body 8 effectively in this way, a
periodic waviness is sometimes formed by the polishing body 8 on
the surface Wa of the workpiece W.
[0025] As illustrated in FIG. 1, in a case where the moving
direction of the polishing tool 10 with respect to the workpiece W
is along the sending direction S (X axis direction), the waviness
formed by the polishing body 8 on the surface Wa of the workpiece W
is smoothed by the polishing body 7 passing the workpiece W
subsequently to the polishing body 8 (or last). Specifically, the
polishing body 7 includes the non-foamed polyurethane resin, and
hence is more rigid than the polishing body 8 and less likely to be
elastically deformed than the polishing body 8 even when being
brought into press-contact with the surface Wa of the workpiece W.
Therefore, the outer peripheral surface 7a of the polishing body 7
is less likely to be held in contact with a valley portion of the
waviness, but more likely to be held in contact with a peak portion
of the waviness, and hence the polishing body 7 has a high
performance in smoothing the waviness. The polishing body 7 removes
the peak portion of the waviness formed on the surface Wa of the
workpiece W, and effectively smoothes the surface Wa of the
workpiece W.
Second Embodiment
[0026] Next, a second embodiment of the present invention is
described. FIG. 2A illustrates a polishing tool 11 according to the
second embodiment. Portions identical to those of FIG. 1 are
denoted by the same symbols, and description thereof is omitted.
The polishing tool 11 includes the rotation shaft 1, and three
disk-like polishing bodies 7, 8, and 9 provided to the rotation
shaft 1 so as to be adjacent to each other. The rotation shaft 1 of
the polishing tool 11 is fixed to the tool rotating device 3 of the
polishing apparatus 100, whereby the polishing tool 11 is supported
to be rotatable relative to the polishing apparatus main body. The
first polishing body 8, the second polishing body 7, and the third
polishing body 9 respectively have outer peripheral surfaces
serving as working surfaces 8a, 7a, and 9a. The first polishing
body 8, the second polishing body 7, and the third polishing body 9
are fixed onto the rotation shaft 1 passing through the center
portion of each disk-like surface of each of the polishing bodies.
With this configuration, the first polishing body 8, the second
polishing body 7, and the third polishing body 9 are fixed onto the
rotation shaft 1 so as to be adjacent to each other, and are each
rotated integrally with the rotation shaft 1 about the center
portion.
[0027] Similarly to the polishing body 7, the polishing body 9
includes the non-foamed resin, and few pores are formed in the
outer peripheral surface 9a of the polishing body 9. In other
words, the outer peripheral surface 8a of the polishing body 8 is
formed into a shape having a porosity higher than that of the outer
peripheral surface 9a of the polishing body 9. It is preferred that
the non-foamed resin include the non-foamed polyurethane resin. The
polishing body 9 includes the non-foamed polyurethane resin, and
hence is more rigid and less likely to be elastically deformed than
the polishing body 8 made of the foamed polyurethane resin. In
other words, the polishing body 8 is less rigid and more likely to
be elastically deformed than the polishing body 9.
[0028] Next, a workpiece processing method according to this
embodiment performed with use of the polishing tool 11 is described
with reference to FIG. 2B.
[0029] After the polishing tool 11 forms a groove in the surface Wa
of the workpiece W in the X axis direction, the polishing tool 11
is shifted by a constant pitch P (sending pitch) in a Y axis
direction orthogonal to the sending direction S (X axis direction),
and is moved in a returning direction (-X axis direction) while
being overlapped to part of the groove which has been already
formed. In this embodiment, as described above, the polishing tool
11 is slid by the constant pitch P in the Y axis direction each
time. The moving direction of the polishing tool 11 with respect to
the workpiece is switched alternately between the sending direction
(X axis direction) and the returning direction (-X axis direction),
and an entire surface of the workpiece W is polishing-processed
into an arbitrary shape. Note that, as a method of moving the
polishing tool 11 relative to the surface Wa of the workpiece W,
the workpiece W may be moved relative to the polishing tool 11, or
the polishing tool 11 may be moved relative to the workpiece W.
[0030] The polishing body 9 is arranged so as to be adjacent to the
polishing body 8, and the polishing body 9 is arranged on the
upstream side with respect to the polishing body 8 when the moving
direction of the polishing tool 11 with respect to the workpiece is
along the returning direction (-X axis direction).
[0031] Further, in a case where the polishing tool 11 is moved in
the returning direction (-X axis direction) relative to the
workpiece W, the waviness formed by the polishing body 8 on the
surface Wa of the workpiece W is smoothed by the polishing body 9
passing the workpiece W subsequently to the polishing body 8 (or
last). That is, the polishing body 9 includes the non-foamed
polyurethane resin, and hence, similarly to the polishing body 7,
the polishing body 9 is more rigid and has a higher performance in
smoothing the waviness than the polishing body 8, to thereby
effectively smooth the surface Wa of the workpiece W. Therefore, in
the second embodiment, the polishing bodies 7, 9 more rigid than
the polishing body 8 are arranged adjacently on both sides of the
polishing body 8. Thus, in a case where the moving direction of the
polishing tool 11 with respect to the workpiece is switched
alternately between the sending direction S (X axis direction) and
the returning direction (-X axis direction), it is possible to
smooth the waviness in any directions after polishing removal.
[0032] As described above, in the case where the moving direction
of the polishing tool 11 with respect to the workpiece is along the
sending direction (X axis direction), the polishing body 7 smoothes
the waviness of the surface Wa after the polishing body 8 performs
polishing removal on the surface Wa. Meanwhile, in the case where
the moving direction of the polishing tool 11 with respect to the
workpiece is along the returning direction (-X axis direction), the
polishing body 9 smoothes the waviness of the surface Wa after the
polishing body 8 performs polishing removal on the surface Wa.
Therefore, while the polishing tool 11 is shifted by the pitch P
each time in a direction orthogonal to the moving direction of the
polishing tool 11 with respect to the workpiece, the polishing tool
11 is moved under alternate switching of the moving direction, and
thus it is possible to perform polishing removal of the entire
surface of the workpiece W and smoothing of the waviness at one
time. In other words, one-time scanning of the polishing tool 11
with respect to the surface Wa of the workpiece W enables the
polishing tool 11 to perform the polishing removal and the
smoothing of the waviness. As described above, the polishing bodies
have different functions from each other, and hence it is possible
to obtain a high-quality surface of the workpiece for a short
period of time when polishing a free-form surface shape.
Third Embodiment
[0033] Next, a third embodiment of the present invention is
described. FIG. 3A illustrates a polishing tool 12 according to the
third embodiment. Portions identical to those of FIGS. 2A and 2B
are denoted by the same symbols, and description thereof is
omitted.
[0034] In FIG. 3A, multiple grooves 9b with a depth (for example,
0.35 mm) of from 0.1 mm to a size corresponding to the thickness of
the polishing body 9 are formed in the outer peripheral surface 9a
of the polishing body 9 at intervals of 2.degree. or less in a
direction parallel to the rotation shaft. In the case where the
depth of each of the grooves is extremely shallow, when the
polishing body 9 is pressed, the polishing body 9 is deformed so
that bottoms of the grooves are brought into contact with the
surface Wa of the workpiece W. Thus, the polishing body 9 cannot
exert an effect of the grooves. The multiple grooves 9b are formed
in the outer peripheral surface 9a of the polishing body 9, and
hence it is possible to suppress formation of a film of the
polishing liquid between the outer peripheral surface 9a of the
polishing body 9 and the surface Wa of the workpiece W, and thus
possible to suppress floating of the polishing body 9 from the
surface Wa. Therefore, the performance in smoothing the waviness
formed on the surface Wa of the workpiece W is further improved.
The grooves may be formed also in the polishing body 7, or may be
formed only in the polishing body 7 but not in the polishing body
9. The polishing body with the grooves has the improved performance
in smoothing the waviness, and hence it is possible to determine
whether to form the grooves depending on the required accuracy.
Fourth Embodiment
[0035] Next, a fourth embodiment of the present invention is
described. FIG. 3B illustrates a polishing tool 13 according to the
fourth embodiment. Portions identical to those of FIGS. 2A and 2B
are denoted by the same symbols, and description thereof is
omitted.
[0036] In FIG. 3B, in the fourth embodiment, the polishing tool 13
includes the polishing body 8 serving as the first polishing body,
and disk-like support members 21a, 21b provided for deformation
prevention, the support members 21a, 21b being respectively
provided to be held in contact with (both) side surfaces 7c, 7c of
the polishing body 7 serving as the second polishing body and being
formed of a metal plate such as a stainless steel plate. In order
to prevent contact with the surface Wa of the workpiece W, each of
the support members 21a, 21b is set to have a radius smaller than
that of the polishing body 7. An elastic deformation amount of each
of the support members 21a, 21b is set to be smaller by 0.1 mm than
the elastic deformation amount of the polishing body 7. In the case
where the difference is more than 0.1 mm, when the polishing body 7
is deformed, the support members 21a, 21b are brought into contact
with the surface Wa of the workpiece W. In the case where the
difference is less than 0.1 mm, the support members 21a, 21b cannot
obtain rigidity enough to support the polishing body 7. Note that,
each of the support members 21a, 21b is set to have a thickness of
from 0.1 mm to 0.5 mm. In the case where the thickness is more than
0.5 mm, the support members 21a, 21b are brought into contact with
another polishing body. In the case where the thickness is less
than 0.1 mm, the support members 21a, 21b cannot obtain the
rigidity enough to support the polishing body 7.
[0037] With the above-mentioned configuration, even if the
polishing body 7 receives a force in the sending direction S during
polishing-processing, the polishing body 7 is supported by the
support members 21a, 21b, and hence it is possible to prevent
deformation of the polishing body 7. With this configuration, it is
possible to suppress unevenness generated during polishing removal
due to the deformation of the polishing body 7, and thus possible
to obtain a higher-quality surface of the workpiece. Further, owing
to the support members 21a, 21b, it is possible to select a less
rigid material in terms of rigidity of the polishing body 7. The
support members may be formed also in the polishing body 9, or may
be formed only in the polishing body 9 but not in the polishing
body 7. When the support members are formed only in one of the
polishing body 7 and the polishing body 9, it is possible to
suppress the unevenness generated during polishing removal by the
polishing body including the support members. When the support
members are formed both in the polishing body 7 and the polishing
body 9, it is possible to suppress the unevenness generated during
polishing removal by both the polishing bodies. Thus, it is
possible to obtain a higher-quality surface of the workpiece.
Fifth Embodiment
[0038] Next, a fifth embodiment of the present invention is
described. FIG. 3C illustrates a polishing tool 14 according to the
fifth embodiment. Portions identical to those of FIGS. 2A and 2B
are denoted by the same symbols, and description thereof is
omitted.
[0039] In FIG. 3C, the polishing tool 14 includes three disk-like
polishing bodies 22, 23, and 24. The polishing body 23 serves as
the first polishing body made of the foamed polyurethane resin
exemplified as the foamed resin, and a large number of pores are
formed in an outer peripheral surface 23a of the polishing body 23.
In contrast, the polishing body 22 serves as the second polishing
body made of the non-foamed polyurethane resin exemplified as the
non-foamed resin, and the polishing body serves as the third
polishing body made of the non-foamed polyurethane resin
exemplified as the non-foamed resin. Few pores are formed in an
outer peripheral surface 22a of the polishing body 22 and an outer
peripheral surface 24a of the polishing body 24. In other words,
the outer peripheral surface 23a of the polishing body 23 is formed
into a shape having a porosity higher than that of the outer
peripheral surface 22a of the polishing body 22 and that of the
outer peripheral surface 24a of the polishing body 24.
[0040] Further, each of the polishing bodies 22, 24 includes the
non-foamed polyurethane resin, and hence is more rigid and less
likely to be elastically deformed than the polishing body 23 made
of the foamed polyurethane resin. In other words, the polishing
body 23 is less rigid and more likely to be elastically deformed
than the polishing bodies 22, 24. Each of the polishing bodies 22,
24 is arranged so as to be adjacent to the polishing body 23. The
polishing body 22 is arranged upstream in the moving direction with
respect to the polishing body 23 when the moving direction of the
polishing tool with respect to the workpiece is along the sending
direction S (X axis direction). Meanwhile, the polishing body 24 is
arranged upstream in the moving direction with respect to the
polishing body 23 when the moving direction is along the returning
direction (-X axis direction). The polishing body 23 is formed to
have a diameter slightly larger than that of the polishing body 22
and that of the polishing body 24.
[0041] Note that, a thickness of each of the polishing body 22 and
the polishing body 24 is, for example, 1.0 mm. A thickness of the
polishing body 23 is, for example, 2.0 mm. In other words, the
polishing body 23 is formed to be thicker than the polishing body
22 and the polishing body 24. With this configuration, a total
thickness of the polishing body 22, the polishing body 23, and the
polishing body 24 is set to be as small as possible (to be, for
example, 4 mm or less) so that the size of the removal trace is 4
mm or less. Thus, it is possible to obtain the necessary processing
accuracy. Further, multiple grooves 22b with a depth of 0.35 mm are
formed in the outer peripheral surface 22a of the polishing body 22
at intervals of 2.degree. or less in the direction parallel to the
rotation shaft. Similarly, multiple grooves 24b with a depth of
0.35 mm are formed in the outer peripheral surface 24a of the
polishing body 24 at intervals of 4.degree. in the direction
parallel to the rotation shaft. In the case where the depth of each
of the grooves is 0.1 mm or less, when the polishing body 9 is
pressed, the polishing body 9 is deformed so that the bottoms of
the grooves are brought into contact with the surface Wa of the
workpiece W. Thus, the polishing body 9 cannot exert an effect of
the grooves. Further, when the interval angle is larger than
2.degree., the film of polishing liquid is generated to inhibit the
polishing body from being held in contact with the surface of the
workpiece, and thus processing efficiency is significantly
decreased. Further, in the fifth embodiment, an interval between
the adjacent polishing bodies 22, 23 and an interval between the
adjacent polishing bodies 23, 24 are set to 0 mm, and the polishing
bodies 22, 23, and 24 are arranged onto the rotation shaft 1.
Without the intervals, the removal trace generated by the entire
tool is reduced, and hence it is possible to correct and process
even a shape having a shorter wavelength. As a result, it is
possible to obtain a high-quality surface of the workpiece.
[0042] In the fifth embodiment, the polishing body 22 and the
polishing body 24 are made of the same material and formed into the
same shape (with the same diameter, the same width, and the same
groove intervals), and are configured to be symmetric with respect
to the polishing body 23. Therefore, in the fifth embodiment, the
same operation and effect as those of the first embodiment are
provided. In addition, in each of the polishing bodies 22, 24, when
the moving direction of the polishing tool with respect to the
workpiece is along any of the +X axis direction and the -X axis
direction, it is possible to similarly smooth the waviness
generated by the polishing body 23. Therefore, it is possible to
obtain a higher-quality surface of the workpiece for a short period
of time when polishing a free-form surface shape. Further, in the
fifth embodiment, the grooves 22b, 24b are formed in the polishing
bodies 22, 24, respectively. Thus, when the moving direction of the
polishing tool with respect to the workpiece is along any of the +X
axis direction and the -X axis direction, it is possible to
suppress floating of each of the polishing bodies 22, 24, and to
effectively smooth the waviness.
[0043] Note that, though the present invention is described based
on the above-mentioned embodiments, the present invention is not
limited thereto.
[0044] Further, in the fourth embodiment, the shape of the support
members 21a, 21b is set to a disk-like shape, and the material of
the support members 21a, 21b is set to stainless steel. However, as
long as it is possible to prevent the deformation of the polishing
body 7, the shape and the material thereof may be set arbitrarily.
Further, in the fourth embodiment, the polishing body 7 is provided
with the support members 21a, 21b. However, similarly, the
polishing body 8 or the polishing body 9 may be provided with
support members (that is, at least one of the first polishing body
and the second polishing body may be provided with support
members). Also in this case, the same effect is provided.
[0045] Further, in the first embodiment, the interval between the
adjacent polishing bodies 7, 8 is set to 0.5 mm. However, the
interval may be set arbitrarily, and the same effect is provided
even when any interval is set. Further, in the fifth embodiment,
the interval between the polishing bodies 22, 23 and the interval
between the polishing bodies 23, 24 are set to 0 mm. However, the
intervals may be set arbitrarily as long as the polishing bodies
are arranged symmetrically, and the same effect is provided even
when any intervals are set.
[0046] Further, in the second to fifth embodiments, the case where
the three polishing bodies are used is described. However, the
present invention is not limited thereto. In the second to fifth
embodiments, the case where the moving direction of the polishing
tool with respect to the workpiece is switched alternately between
the X axis direction and the -X axis direction is described.
However, in a case where the moving direction is along one
direction, it is possible to omit the polishing body situated
downstream in the sending direction with respect to the polishing
body 8 (polishing body 23).
[0047] Further, another polishing body may be interposed between
the polishing body 8 and the polishing body 7, and still another
polishing body may be interposed between the polishing body 8 and
the polishing body 9. Similarly, another polishing body may be
interposed between the polishing body 23 and the polishing body 22,
and still another polishing body may be interposed between the
polishing body 23 and the polishing body 24. In this case, the
polishing body 7, 22 or the polishing body 9, 23 passes the surface
of the workpiece last, and thus it is possible to effectively
smooth the waviness. Note that, in this case, it is preferred that
the same number of polishing bodies be provided on each side of the
polishing body 8, 23 so as to be symmetric with respect to the
polishing body 8, 23.
[0048] Further, in the first to fifth embodiments, the case where
the foamed polyurethane resin is exemplified as the foamed resin is
described. However, the foamed resin may include a foamed epoxy
resin and a foamed phenolic resin. Similarly, the case where the
non-foamed polyurethane resin is exemplified as the non-foamed
resin is described. However, the non-foamed resin may include a
non-foamed epoxy resin and a non-foamed phenolic resin.
[0049] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0050] This application claims the benefit of Japanese Patent
Application No. 2009-181085, filed on Aug. 3, 2009, which is hereby
incorporated by reference herein in its entirety.
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