U.S. patent application number 16/078666 was filed with the patent office on 2019-01-31 for damped abrasive article.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Jonathan Charlotteau, Jean-Luc Rifaut.
Application Number | 20190030683 16/078666 |
Document ID | / |
Family ID | 59686524 |
Filed Date | 2019-01-31 |
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United States Patent
Application |
20190030683 |
Kind Code |
A1 |
Rifaut; Jean-Luc ; et
al. |
January 31, 2019 |
DAMPED ABRASIVE ARTICLE
Abstract
A damped abrasive article comprises a damping body and an
abrasive surface provided on at least a portion of the damping
body. The damping body comprises a synthetic polymer having a
Storage Modulus from 1000 MPa to 2500 MPa and a Loss factor from
0.025 to 0.10 at 25.degree. C. and 10 Hz.
Inventors: |
Rifaut; Jean-Luc; (Brussels,
BE) ; Charlotteau; Jonathan; (Couillet, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
Saint Paul |
MN |
US |
|
|
Family ID: |
59686524 |
Appl. No.: |
16/078666 |
Filed: |
February 21, 2017 |
PCT Filed: |
February 21, 2017 |
PCT NO: |
PCT/US2017/018623 |
371 Date: |
August 22, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62300476 |
Feb 26, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24D 5/16 20130101; B24B
19/009 20130101; B24D 5/06 20130101; B24D 7/18 20130101; B24D 7/066
20130101; B24D 3/001 20130101; B24D 7/16 20130101; B24B 9/08
20130101; B24B 41/007 20130101 |
International
Class: |
B24D 7/06 20060101
B24D007/06; B24D 7/18 20060101 B24D007/18 |
Claims
1. A damped abrasive article comprising: a damping body; and an
abrasive surface provided on at least a portion of the damping
body; wherein the damping body comprises a synthetic polymer having
a Storage Modulus from 1000 MPa to 2500 MPa and a Loss factor from
0.025 to 0.10 at 25.degree. C. and 10 Hz.
2. The damped abrasive article of claim 1 wherein the damping body
comprises polyamide 6.
3. The damped abrasive article of claim 1 wherein the damping body
comprises polyamide 6 and glass fibers.
4. The damped abrasive article of claim 3 wherein the glass fibers
comprise from 1 to 50 percent by weight of the damping body.
5. The damped abrasive article of claim 3 wherein the glass fibers
comprise 30 percent by weight of the damping body.
6. The damped abrasive article of claim 1 wherein the machine
attaching end and the damping body comprise a synthetic polymer
having a Storage Modulus from 1000 MPa to 2500 MPa and a Loss
factor from 0.025 to 0.10 at 25.degree. C. and 10 Hz.
7. The damped abrasive article of claim 1 wherein the Storage
Modulus obtained at 25.degree. C. and 10 Hz is greater than the
Storage Modulus obtained at 45.degree. C. and 10 Hz for the damping
body.
8. The damped abrasive article of claim 2 wherein the Storage
Modulus obtained at 25.degree. C. and 10 Hz is greater than the
Storage Modulus obtained at 45.degree. C. and 10 Hz for the damping
body.
9. The damped abrasive article of claim 3 wherein the Storage
Modulus obtained at 25.degree. C. and 10 Hz is greater than the
Storage Modulus obtained at 45.degree. C. and 10 Hz for the damping
body.
10. The damped abrasive article of claim 4 wherein the Storage
Modulus obtained at 25.degree. C. and 10 Hz is greater than the
Storage Modulus obtained at 45.degree. C. and 10 Hz for the damping
body.
11. The damped abrasive article of claim 5 wherein the Storage
Modulus obtained at 25.degree. C. and 10 Hz is greater than the
Storage Modulus obtained at 45.degree. C. and 10 Hz for the damping
body.
12. The damped abrasive article of claim 6 wherein the Storage
Modulus obtained at 25.degree. C. and 10 Hz is greater than the
Storage Modulus obtained at 45.degree. C. and 10 Hz for the damping
body.
Description
BACKGROUND
[0001] The present disclosure relates generally to abrasive
articles and, more particularly, to abrasive cutters and grinding
wheels for brittle materials such as glass, ceramics,
glass-ceramics and the like.
[0002] Brittle materials such as glass, ceramic, glass-ceramic are
sensitive to chips, cracks, or micro-cracks generated during the
machining process. These chips and cracks can reduce the lifetime
of the produced part or reduce its mechanical properties such as
fatigue strength and flexural strength. Thermal properties are also
affected and can lead to rejection of the machined part. The
maximum acceptable size of the chips or micro-cracks, which drives
their propagation behavior between grain boundaries when exiting or
through the solid material, is linked with the structure of the
material and the balance of forces applied on the part; it can be
calculated using the Griffith law and the Weibull distribution.
[0003] During the machining process of brittle materials like
glass, ceramic, glass-ceramic and similar materials, chips and
cracks may be generated due to the pressure applied on the machined
part when removing material. The chips and micro-cracks are due to
the contact force between the working abrasive diamonds and the
brittle material. The contact force is needed to penetrate the
abrasive diamonds into the material and the relative movement
between the diamonds on the tool and the material removes the
required material from the workpiece. If there is vibration between
the diamonds and the brittle material during the machining process,
each diamond acts as a hammer and can generate chips and
micro-cracks at the surface of the material or inside it.
[0004] Conventional techniques used to reduce the number and size
of chips and micro-cracks include reducing the diamond grit size or
grit quality, lowering the bond hardness, or modifying the machine
parameters, such as, by reducing the infeed speed. These
techniques, however, can negatively affect the productivity of the
grinding process by increasing the time needed for the operation
and by reducing the useful life of the tool.
[0005] Abrasive articles for glass are known in the prior art. US
Patent Publication 2002/0004362 (Lubke) discloses a countersink bit
for glass that has a shaft extending along and rotatable about an
axis, a head fixed to the shaft and having a frustoconical surface
centered on the axis, a layer of grinding material on the surface,
and an axially relatively incompressible plastic body capable of
transmitting torque between the surface and the shaft. The plastic
body has good damping capabilities so that any tendency of the head
to vibrate or chatter is largely eliminated.
SUMMARY
[0006] The industry is always seeking improved abrasive articles
for brittle materials. More particularly, it would be desirable to
provide a grinding wheel for brittle materials, such as glass,
ceramics, glass-ceramics and the like, that has improved durability
and produces fewer and/or smaller chips, cracks, or micro-cracks in
the brittle material during the machining process.
[0007] It has been discovered that improved damping, and thereby a
reduction in micro cracks and improved tool life, can be achieved
by positioning a damping body formed from a synthetic polymer
between a machine attaching end and an abrasive surface in a damped
grinding wheel. In particular, the synthetic polymer is selected to
have a specific modulus range and loss factor when tested under
dynamic cyclic cycling. The range for these properties that
achieves the purpose is a Storage Modulus of the damped body of
from 1000 MPa to 2500 MPa and a Loss Factor from 0.025 to 0.10 at
25.degree. C. and 10 Hz.
[0008] Thus, in one embodiment the invention resides in a damped
abrasive article comprising an abrasive surface comprising abrasive
particles and a damping body connected with the abrasive surface;
wherein the damping body comprises a synthetic polymer having a
Storage Modulus from 1000 MPa to 2500 MPa and a Loss Factor from
0.025 to 0.10 at 25.degree. C. and 10 Hz.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1 and 1A illustrate a damped abrasive article
according to one embodiment.
[0010] FIGS. 2 and 2A illustrate a damped abrasive article
according to another embodiment.
[0011] FIGS. 3 and 3A illustrate a damped abrasive article
according to another embodiment.
[0012] FIGS. 4 and 4A illustrate a damped abrasive article
according to another embodiment.
[0013] FIGS. 5 and 5A illustrate a damped abrasive article
according to another embodiment.
[0014] FIGS. 6 and 6A illustrate a damped abrasive article
according to another embodiment.
[0015] FIGS. 7 and 7A illustrate a damped abrasive article
according to another embodiment.
[0016] FIGS. 8 and 8A illustrate a damped abrasive article
according to another embodiment.
DETAILED DESCRIPTION
[0017] Referring now to FIGS. 1 and 1A, a damped abrasive article
10 in the form of a cutter is shown. More particularly, FIGS. 1 and
1A show an abrasive article 10 in the form of a grinding wheel 40
suited for grinding bio-ceramic prosthesis. The damped abrasive
article 10 includes a machine attaching end 12, a damping body 14,
and an abrasive cutting surface 16. The machine attaching end 12 is
configured to transmit driving torque and linear force from a
suitable machine (not shown) to rotate and translate the damped
abrasive article 10 relative to a work piece when machining or
removing material from the work piece.
[0018] The machine attaching end 12 may comprise a round, square,
hexagonal, or polygonal shaft, a tapered shaft and collet, a
threaded shaft, a round shaft with flats for the jaws of a chuck,
or other suitable mechanical structure to transmit the required
torque and linear force. In the illustrated embodiment, the machine
attaching end 12 include a first end attachment portion 12a for
attachment with the machine, a tapered middle portion 12b, and a
cylindrical portion 12c attached with the damping body 14. The
first end portion 12a can utilize external or internal threads
depending on the configuration of the spindle of the machine used
to rotate and translate the damped abrasive article 10. In the
illustrated embodiment, the first end portion 12a includes wrench
flats 24 or a hole for use with an open-end wrench for installing
and removing the first end portion 12a when replacing the damped
abrasive article 10.
[0019] Typically the machine attaching end 12 is made from a metal
material, such as steel or stainless steel, for use with cooling or
cutting fluids during the machining operation. Other suitable
metals, such as rigid plastics or the material selected for the
damping body 14, can be utilized for the machine attaching end
12.
[0020] In order to cool the damped abrasive article during use, an
optional longitudinal bore 26 can be provided through the machine
attaching end 12 and through the damping body 14 to supply cooling
fluid to the abrasive cutting surface 16. The size of the bore can
be selected based on the flow of coolant required.
[0021] Various mechanical interfaces can be used to connect the
abrasive cutting surface 16 and the machine attaching end 12 to the
damping body 14. For example, the abrasive cutting surface 16 can
comprise a hollow cylinder 28 with a recessed bore 30 that mates
with the damping body 14 having cylindrical projection 32 extending
from a shoulder 34.
[0022] Referring now to FIGS. 2-8, wherein like reference numerals
refer to like or corresponding parts throughout the several views,
FIGS. 2 and 2A show a grinding wheel 40 suited for fletting
tableware glass. The grinding wheel 40 includes an annular damping
body 14 and an annular cutting surface 16. The annular damping body
14 contains a central opening 42, opposed first and second major
surfaces 44, 46, and an outer circumferential edge surface 48. In
the illustrated embodiment, the annular cutting surface 16 includes
a beveled edge 16a adjacent the circumferential edge surface 48.
The annular abrasive cutting surface 16 is provided on an outer
annular region of the damping body 14 second major surface 46
adjacent the outer circumferential edge surface 48 of the damping
body. In the illustrated embodiment, the abrasive cutting surface
16 is not provided on an inner annular region of the damping body
16 second major surface 46. It will be recognized, however, that
the abrasive cutting surface 16 can be provided on the entirety of
the damping body 16 second major surface. In other embodiments, the
abrasive cutting surface 16 may be conterminous with the second
major surface of the damping body 14, or the cutting surface 16 may
be provided in the form of segments or patterns to cover selected
regions of the second major surface 46 of the damping body 14. In
one embodiment, the abrasive cutting surface 16 is a metal bonded
diamond layer glued directly to a polyamide glass fiber reinforced
damping body 14. In the illustrated embodiment, the damping body 14
is generally thin and flat and has a uniform thickness. More
particularly, the first and second major surface 42, 44 are
co-planar.
[0023] FIGS. 3 and 3A show a grinding wheel 40 suited for machining
construction glass. The grinding wheel 40 includes an annular
damping body 14, an annular cutting surface 16, and an optional
annular reinforcing plate 50 arranged between the damping body 14
and the cutting surface 16. The reinforcing plate 50 can be made of
metal or filled resin material like filled phenolic resin. The
annular damping body 14 contains a central opening 42, and has
opposed first and second major surfaces 44, 46 and an outer
circumferential edge surface 48. The annular reinforcing plate 50
is provided along an outer annular region of the damping body 14
second major surface 46 adjacent the outer circumferential edge
surface 48, and the annular abrasive cutting surface 16 is provided
on an outer annular region of the reinforcing plate 50. In the
illustrated embodiment, the outer diameters of the damping body 14,
the cutting surface 16 and the reinforcing plate 50 are equal and
the outer surfaces of the damping body 14, the cutting surface 16
and the reinforcing plate 50 contiguous. In the illustrated
embodiment, the grinding wheel 40 further includes an optional
annular race or central reinforcing hub 62 provided along the inner
annular surface defining the central opening 42. The reinforcing
hub 62 enhances the strength of the damping body 14 in the region
adjacent the central opening 42 of the grinding wheel 40, and
thereby improves the performance and durability of the grinding
wheel 40. The reinforcing hub 62 may be secured directly to the
damping body 14 by, of example, molding the reinforcing hub 62 and
damping body 14 together, or by pressing the reinforcing hub 62
into the damping body 14, or the reinforcing hub 62 may be secured
to the damping body 14 by fastening or bonding the reinforcing hub
62 to the damping body 14 using, for example, mechanical fasteners
or adhesives.
[0024] In the illustrated embodiment, the inner diameter of the
abrasive cutting surface 16 is greater than the inner diameter of
the reinforcing plate 50, whereby the radial dimension (i.e. the
thickness in the radial dimension) of the cutting surface 16 is
less than and the radial dimension of the reinforcing plate, and
the cutting surface 16 does not cover an inner annular portion of
the reinforcing plate 50. In addition, the inner diameter of the
reinforcing plate 50 is greater than the inner diameter of the
damping body 14, whereby the radial dimension of the reinforcing
plate is less than the radial dimension of the damping body 14 and
the reinforcing plate 50 does not cover an inner annular portion of
the damping body 14. It will be recognized, however, that the inner
and outer diameters of the damping body 14, the cutting surface 16
and the reinforcing plate 50 can be varied depending on the overall
construction and intended end-use application for the grinding
wheel 40.
[0025] FIGS. 4 and 4A show a grinding wheel 40 similar to the
grinding wheel depicted in FIGS. 3 and 3A except the optional
reinforcing plate 50 in FIGS. 3 and 3A has been eliminated, the
annular damping body 14 includes an annular shoulder portion 14a,
the annular abrasive cutting surface 16 is contiguous with the
damping body 14 annular shoulder portion 14a, and the annular
central reinforcing hub 62 has been enlarged to extend from the
central opening 42 to the outer circumferential surface 48.
[0026] FIGS. 5 and 5A show a grinding wheel 40 suited for flute
grinding operations on drills or milling tools. The grinding wheel
40 includes an annular damping body 14, an annular cutting surface
16, and an optional annular central reinforcing hub or plate 50.
The annular damping body 14 contains a central opening 42, opposed
first and second major surfaces 44, 46, and an outer
circumferential edge surface 48. In the illustrated embodiment, the
outer circumferential edge surface 48 is beveled and flares
radially outwardly in the direction from the first major surface 44
to the second major surface 46. The beveled edge surface 48
includes an outer annular recess 52 remote from the central
reinforcing hub 62 configured to receive the annular cutting
surface 16, whereby the annular abrasive cutting surface 16 is
provided along the beveled edge surface 48. The damping body 14
further includes an inner annular recess 54 adjacent the central
opening 42 configured to receive the reinforcing hub 62.
[0027] Referring now to FIGS. 6 and 6A, there is shown a grinding
wheel 40 suited for machining construction or automotive glass. The
grinding wheel 40 includes an annular damping body 14, an annular
abrasive cutting surface 16, and an optional annular central hub
62. The annular damping body 14 includes opposed first and second
major surfaces 44, 46, an outer circumferential edge surface 48.
The annular damping body 14 contains a central opening 42 and a
plurality of axial through bores 56. The annular damping body 14
further contains an annular recess or channel 58 adjacent the outer
circumferential edge surface 48 adapted to receive the annular
abrasive cutting surface 16. The annular damping body 14 includes a
pair of shoulder portions 14a that extend along each side of the
abrasive cutting surface 16. In the illustrated embodiment, the
abrasive cutting surface 16 contains an annular groove 60.
[0028] FIGS. 7 and 7A show a grinding wheel 40 similar to the
grinding wheel shown in FIGS. 6 and 6A except one of the shoulder
portions 14a has been eliminated and replaced with an annular
reinforcing plate 50. The reinforcing plate 50 may formed of an
electrically conductive metal material, such as steel, and may be
provided with an electrical connection to enable profiling by an
electro-erosion process. An electro-erosion process may be used to
profile or shape a grinding wheel in which the abrasive
incorporated is diamond, cubic boron nitride or similar hard
material. The electro-erosion process is able to achieve the
required profile precision. As based on fusion, vaporization and
ejection of the material due to the energy given by electrical
sparking between two electrodes (metal bonded grinding wheel and
profiling electrode) placed in a dielectric bath, an electrical
conductivity between the abrasive metal bonded layer and the
machine is needed.
[0029] Referring now to FIGS. 8 and 8A, there is shown another
embodiment of a grinding wheel 40 suited for machining construction
or automotive glass. The grinding wheel 40 include an annular
damping body 14 and an annular abrasive cutting surface 16. The
annular damping body 14 includes opposed first and second major
surfaces 44, 46, an outer circumferential edge surface 48. The
annular damping body 14 contains a central opening 42 and a
plurality of axial bores 56. The annular damping body 14 further
contains an annular recess or channel 58 adjacent the outer
circumferential edge surface 48 adapted to receive the annular
abrasive cutting surface 16. The annular damping body 14 includes a
shoulder portion 14a that extends along the second major surface 46
adjacent the abrasive cutting surface 16. In the illustrated
embodiment, the abrasive cutting surface 16 contains an annular
groove 60. The grinding wheel 40 further includes an annular
reinforcing plate 50 arranged along, and contiguous with, the first
major surface 44 of the annular damping body 14. As with the
embodiment in FIGS. 7 and 7A, the reinforcing plate 50 may formed
of an electrically conductive metal material, such as steel, and
may be provided with an electrical connection to enable profiling
by an electro-erosion process.
[0030] In any of the embodiments described herein, the damping body
14 is made of a synthetic polymer. The polymer can be a
thermoplastic, and selected from, for example, polyethylene,
polypropylene, polyester, polyamide, polyvinyl, polyetherimide,
polydimethylsiloxane or polyetheretherketone for thermoplastic
families. For adjusting mechanical, electrical and thermal
properties, the synthetic polymer can be reinforced or blended with
a filler. Suitable fillers can be fibers or tubes such as carbon
fibers or nanotubes, glass fibers, mineral fibers, ceramic fibers,
metal fibers or aramid fibers; it can be whiskers such as silicon
carbide whiskers or powder such as silicon carbide powder, aluminum
oxide powder or metal powder such as aluminum powder, copper
powder. Suitable fillers can also include mixtures of those
components.
[0031] A quantity of an anti-wearing agent can be added into the
mixture in order to reduce the possible wear of the synthetic
polymer body during the drilling and/or chamfering operation when
abrasive material is machined. Suitable anti-wearing agents include
molybdenum disulfide, graphite or PTFE
[0032] In one embodiment, the damping body 14 is made from
polyamide 6 reinforced with glass fibers. In one embodiment, glass
fibers are used as a reinforcing material at a level from 1 percent
to 50 percent, or from 10 percent to 50 percent, or from 30 percent
to 50 percent by weight of the polyamide 6 mixture. A 30 percent
glass fiber reinforced polyamide 6 mixture is commercially marketed
by Ensinger GmbH under the tradename TECAMID 6 GF30 Black. This
material was tested for the Storage Modulus and Loss Factor as
described below and found to have a Storage Modulus of 1943 MPa and
a Loss Factor of 0.033 at 25.degree. C. and 10 Hz.
[0033] Similar mixtures of polyamide 6 with glass fibers are
marketed by E.I. du Pont de Nemours--under the tradename DuPont.TM.
Zytel.RTM. 73G30T NC010 or DuPont.TM. Zytel.RTM. 73G30T BK261, or
by Rhodia SA under the tradename TECHNYL.RTM. C216 V30 BLACK Z/4.
Other polyamide 6 producers like EMS-Grivory part of the EMS Group
under the trade name Grilon.RTM. B provide suitable products.
[0034] It has been determined that in order to further reduce
and/or eliminate chips and micro cracks when using the damped
abrasive article 10, the Storage Modulus and the Loss factor of the
synthetic polymer is important. These properties can be measured
using ASTM D4065 Standard Practice for Plastics: Dynamic Mechanical
Properties: Determination and Report of Procedures
[0035] Dynamic mechanical analysis and sample preparation were
performed according to the ASTM D4065-12 standard and the
procedures mentioned therein. Dynamic mechanical measurements were
performed on a DMTA V (Rheometric Scientific) in single cantilever
mode in a frequency range from 0.1 to 10 Hz and fixed strain of
0.05% at a temperature of 25.degree. C. to 45.degree. C. Specimens
of rectangular shape measuring 20.times.5.times.4 mm are used. The
temperature calibration was done using a Fluke 724 Temperature
Calibrator, which is regularly calibrated by an accredited
calibration institute. PVC standards (available through RHEO
Service) were measured on the DMTA periodically to check
temperature accuracy. The Storage Modulus and Lost Factor values
are obtained at 25.degree. C., 35.degree. C., and 45.degree. C. and
at 10 Hz.
TABLE-US-00001 TABLE 1 Storage Modulus and Loss Factor (10 Hz)
Storage Loss Loss Modulus Modulus Factor E' E' Tan Material Temp.
Mpa Mpa Delta polyamide 6 glass fiber mix 25.degree. C. 1943 64
0.033 (GF30) 35.degree. C. 1575 128 0.081 45.degree. C. 1303 106
0.082 thermoset glass filled phenolic 25.degree. C. 2557 60 0.024
(x680) (Prior Art) 35.degree. C. 3084 69 0.022 45.degree. C. 3059
63 0.021
[0036] As shown in the Examples, a significant reduction in defects
during machining of brittle materials and an improved tool life was
achieved when the Storage Modulus of the material forming the
damped body is from 1000 MPa to 2500 MPa, or from 1000 MPa to 2000
MPa, or from 1200 MPa to 2000 MPa at 25.degree. C. and 10 Hz.
Additionally, for the improvements noted above, the Loss Factor of
the material forming the damped body is from 0.025 to 0.10, or from
0.03 to 0.10, or from 0.03 to 0.09 at 25.degree. C. and 10 Hz. As
listed in Table 1, the Storage Modulus at 45.degree. C. and 10 Hz
(1303 Mpa) is lower than the Storage Modulus at 25.degree. C. and
10 Hz (1943 Mpa) for the polyamide 6 glass fiber material used for
the damped abrasive article in one embodiment. The prior art
thermoset glass filled phenolic had a Storage Modulus that
increased as the temperature of the test was increased whereas the
Storage Modulus of the polyamide 6 glass fiber mix decreased as the
temperature of the test was increased. The Storage Modulus and Loss
Factor are determined in accordance with ASTM D4065 and the test
parameters described above.
[0037] Another factor in the design of the damped abrasive article
is the shape and size of the damped central body 14. In general,
the length of the damping body along the longitudinal axis of the
abrasive article is preferably from 3 mm to about 60 mm although
lengths outside of this range may be used as well. If the length
becomes too small insufficient damping may occur, and if the length
becomes too great excessive twisting or flexing of the abrasive
article may occur during use. In order to reduce such twisting or
flexing, a reinforcing plate 50 may be provided on the side of the
grinding wheel or in the bore of the grinding wheel.
[0038] In any of the embodiments described herein, the abrasive
cutting surface 16 may be provided as, for example, a cutting
member affixed to the damping body 14 or as a thin abrasive surface
coated onto the damping body 14. In addition, the abrasive cutting
surface 16 may be provided as a member, such as an annular member,
having a continuous surface, or the abrasive cutting surface 16 may
be provided in the form of separate (i.e. individual) segments that
define a discontinuous surface. The abrasive cutting member may be
affixed to the damping body 14 using mechanical fastening means or
bonded to the damping body 14 using, for example, glue or adhesive.
In some embodiments, the abrasive cutting surface 16 comprises an
abrasive particle in a binder. Any suitable abrasive particle may
be included in the abrasive cutting surface. Typically, the
abrasive particles have a Mohs' hardness of at least 8, or even 9
and 10. Examples of such abrasive particles include aluminum oxide,
fused aluminum oxide, ceramic aluminum oxide, white fused aluminum
oxide, heat treated aluminum oxide, silica, silicon carbide, green
silicon carbide, alumina zirconia, diamond, iron oxide, ceria,
cubic boron nitride, garnet, tripoli, alpha alumina sol-gel derived
abrasive particles, and combinations thereof.
[0039] Typically, the abrasive particles have an average particle
size of less than or equal to 1500 micrometers, although average
particle sizes outside of this range may also be used. For grinding
operations, useful abrasive particle sizes typically range from an
average particle size in a range of from at least 0.01, 1, 3 or
even 5 micrometers up to and including 35, 100, 250, 500, or even
as much as 1500 micrometers. In specific embodiments diamond grits
between 10 .mu.m and 300 .mu.m are used.
[0040] The abrasive cutting surface is generally made by a molding
process. During molding, a binder precursor, either liquid organic,
powdered inorganic, powdered organic, or a combination of thereof,
could be mixed or not with the abrasive particles. In some
instances, a liquid medium (either resin or a solvent) is first
applied to the abrasive particles to wet their outer surface, and
then the wetted particles are mixed with a powdered medium. The
abrasive cutting surface according to the present disclosure may be
made by compression molding, injection molding, transfer molding,
or the like. The molding can be done either by hot or cold pressing
or any suitable manner known to those skilled in the art.
[0041] The binder typically comprises a glassy inorganic material
(e.g., as in the case of vitrified abrasive wheels), metal, or an
organic resin (e.g., as in the case of resin-bonded abrasive
wheels).
[0042] Glassy inorganic binders may be made from a mixture of
different metal oxides. Examples of these metal oxide vitreous
binders include silica, alumina, calcia, iron oxide, titania,
magnesia, sodium oxide, potassium oxide, lithium oxide, manganese
oxide, boron oxide, phosphorous oxide, and the like. During
manufacture of a vitreous abrasive cutting surface, the vitreous
binder, in a powder form, may be mixed with a temporary binder,
typically an organic binder. The vitrified binders may also be
formed from a frit, for example anywhere from about one to 100
percent frit, but generally 20 to 100 percent frit. Some examples
of common materials used in frit binders include feldspar, borax,
quartz, soda ash, zinc oxide, whiting, antimony trioxide, titanium
dioxide, sodium silicofluoride, flint, cryolite, boric acid, and
combinations thereof. These materials are usually mixed together as
powders, fired to fuse the mixture and then the fused mixture is
cooled. The cooled mixture is crushed and screened to a very fine
powder to then be used as a frit binder. The temperature at which
these frit bonds are matured is dependent upon its chemistry, but
may range from anywhere from about 600.deg. C. to about 1800.deg.
C.
[0043] The binder, which holds the shape of the abrasive cutting
surface, is typically included in an amount of from 5 to 50
percent, more typically 10 to 25, and even more typically 12 to 24
percent by weight, based on the total weight of the bonded abrasive
wheel.
[0044] Examples of metal binders include tin, copper, cobalt,
bronze, aluminum, iron, cast iron, manganese, silver, titanium,
carbon, chromium, nickel, and combinations thereof in prealloyed
forms or not. Metal binders can include fillers such as silicon
carbide, aluminum oxide, boron carbide, tungsten, tungsten carbide
and combination thereof in prealloyed form or not. During
manufacture of a metal abrasive cutting surface, the metal binder,
in a powder form, may be mixed with a temporary binder, typically
an inorganic binder. The metal binders may also be formed from a
mix of pure and prealloyed powder or already pre-mix of metal
powders and fillers. These materials are usually mixed together as
powders, fired to sinter the mixture and then the sintered mixture
is cooled. The temperature at which these metal bonds are matured
is dependent upon the chemistry, but may range from anywhere from
about 450.degree. C. to about 1100.degree. C.
[0045] The binder, which holds the shape of the abrasive cutting
surface, is typically included in an amount of from 65 to 98
percent, more typically 75 to 96, and even more typically 88 to 96
percent by weight, based on the total weight of the bonded abrasive
wheel.
[0046] The binder may comprise a cured organic binder resin,
filler, and grinding aids. Phenolic resin is the most commonly used
organic binder resin, and may be used in both the powder form and
liquid state. Although phenolic resins are widely used, it is
within the scope of this disclosure to use other organic binder
resins including, for example, epoxy resins, polyimide resins,
polyamide-imide resins, polyetherimide resins, polyetherketone
resins, polyetheretherketone resins, polyethersulfone resins,
polyester resins, urea-formaldehyde resins, rubbers, shellacs, and
acrylic binders. The organic binder may also be modified with other
binders to improve or alter the properties of the binder. The
amount of organic binder resin can be, for example, from 15 to 100
percent by weight of the total weight of the binder.
[0047] Useful phenolic resins include novolac and resole phenolic
resins. Novolac phenolic resins are characterized by being
acid-catalyzed and having a ratio of formaldehyde to phenol of less
than one, typically between 0.5:1 and 0.8:1. Resole phenolic resins
are characterized by being alkaline catalyzed and having a ratio of
formaldehyde to phenol of greater than or equal to one, typically
from 1:1 to 3:1. Novolac and resole phenolic resins may be
chemically modified (e.g., by reaction with epoxy compounds), or
they may be unmodified. Exemplary acidic catalysts suitable for
curing phenolic resins include sulfuric, hydrochloric, phosphoric,
oxalic, and p-toluenesulfonic acids. Alkaline catalysts suitable
for curing phenolic resins include sodium hydroxide, barium
hydroxide, potassium hydroxide, calcium hydroxide, organic amines,
or sodium carbonate.
[0048] Phenolic resins are well-known and readily available from
commercial sources. Examples of commercially available novolac
resins include DUREZ 1364, a two-step, powdered phenolic resin
(marketed by Durez Corporation of Addison, Tex., under the trade
designation VARCUM (e.g., 29302), or HEXION AD5534 RESIN (marketed
by Hexion Specialty Chemicals, Inc. of Louisville, Ky.). Examples
of commercially available resole phenolic resins useful in practice
of the present disclosure include those marketed by Durez
Corporation under the trade designation VARCUM (e.g., 29217, 29306,
29318, 29338, 29353); those marketed by Ashland Chemical Co. of
Bartow, Fla. under the trade designation AEROFENE (e.g., AEROFENE
295); and those marketed by Kangnam Chemical Company Ltd. of Seoul,
South Korea under the trade designation "PHENOLITE" (e.g.,
PHENOLITE TD-2207).
[0049] In some embodiments, the abrasive cutting surface is affixed
to the damping body by an adhesive. Suitable industrial adhesives
can be used such as an epoxy product sold under the tradename
3M.TM. Scotch-Weld.TM. Epoxy Adhesive DP460. In other embodiments,
the abrasive cutting surface can be fixed to one or more
intermediate materials with sufficient strength to transmit the
torque from the damping body to the abrasive cutting surface
without slipping.
EXAMPLES
Example 1
[0050] A diamond metal bonded abrasive article as shown in FIG. 7
was made to grind the profile of an automotive front windshield in
2.1 mm thick glass. The abrasive article had a damping body made
from polyamide 6 reinforced with 30% glass fibers by weight. The
polyamide 6 glass fiber mix is commercially marketed by Ensinger
GmbH under the tradename TECAMID 6 GF30 Black. This material was
tested for the Storage Modulus and Loss Factor as described and
found to have a Storage Modulus of 1943 MPa and a Loss Factor of
0.033 at 25.degree. C. and 10 Hz. The abrasive article was operated
at xx rpm at a feed rate of xx m/min on a Bystronic machine,
dressing every xx pieces and cooled with water slightly emulsified
with a lubricant additive. The abrasive article. Lifetime number of
ground meters was xx.+GQM
Comparative 1
[0051] A diamond metal bonded abrasive article as shown in FIG. 7
was tested to grind the profile of an automotive front windshield
in 2.1 mm thick glass. The abrasive article had a central body made
of steel. The abrasive article was operated at 5,100 rpm at a feed
rate of 14 m/min, having a material removal of 0.5 mm and dressing
every 15 pieces and cooled with water slightly emulsified with a
lubricant additive. The abrasive article had a lifetime number of
57112 ground meters including 5 re-profiling. The quality
measurement was estimated having a GQM of 30.
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