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Patent 2324578 Summary

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(12) Patent: (11) CA 2324578
(54) English Title: ABRASIVE TOOLS
(54) French Title: OUTILS ABRASIFS
Status: Deemed expired
Bibliographic Data
(51) International Patent Classification (IPC):
  • B24D 5/06 (2006.01)
  • B24D 3/08 (2006.01)
(72) Inventors :
  • RAMANATH, SRINIVASAN (United States of America)
  • WILLISTON, WILLIAM H. (United States of America)
  • BULJAN, SERGEJ-TOMISLAV (United States of America)
(73) Owners :
  • NORTON COMPANY (United States of America)
(71) Applicants :
  • NORTON COMPANY (United States of America)
(74) Agent: GOWLING WLG (CANADA) LLP
(74) Associate agent:
(45) Issued: 2004-11-02
(86) PCT Filing Date: 1999-02-04
(87) Open to Public Inspection: 1999-09-30
Examination requested: 2000-09-19
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): Yes
(86) PCT Filing Number: PCT/US1999/002399
(87) International Publication Number: WO1999/048646
(85) National Entry: 2000-09-19

(30) Application Priority Data:
Application No. Country/Territory Date
09/049,623 United States of America 1998-03-27
09/218,844 United States of America 1998-12-22

Abstracts

English Abstract




Abrasive tools suitable for precision
grinding of hard brittle materials, such as
ceramics and composites comprising ceramics, at
peripheral wheel speeds up to 160 meters/second
are provided. The abrasive tools comprise a
wheel core (2) attached to an abrasive rim of
dense, metal bonded superabrasive segments (8)
by means of a thermally stable bond (6). A
preferred tool for backgrinding ceramic wafers
contains graphite filler and a relatively low
concentration of abrasive grain (4).


French Abstract

L'invention concerne des outils abrasifs appropriés à une rectification précise, à des vitesses périphériques de roue atteignant 160 mètres par seconde, de corps fragiles durs, tels que la céramique et les composites contenant de la céramique. Ces outils abrasifs se composent d'un moyeu (2) sur lequel est fixée au moyen d'une liaison (6) thermiquement stable une couronne abrasive de segments (8) superabrasifs denses liés par métal. Un outil préféré pour rectifier la surface de tranches de céramique contient une charge de graphite et une concentration relativement faible de grains (4) abrasifs.

Claims

Note: Claims are shown in the official language in which they were submitted.




We claim:

1. A surface grinding abrasive tool comprising a core,
having a minimum specific strength parameter of 2.4 MPa-cm3/g,
a core density of 0.5 to 8.0 g/cm3, a circular perimeter, and
an abrasive rim defined by a plurality of abrasive segments;
wherein the abrasive segments comprise, in amounts selected to
total a maximum of 100 volume %,.from 0.05 to 10 volume %
superabrasive grain, from 10 to 35 volume % friable filler,
and from 55 to 89.95 volume % metal bond matrix having a
fracture toughness of 1.0 to 3.0 MPa M1/2.

2. The abrasive tool of claim 1, wherein the core comprises
a metallic material selected from the group consisting of
aluminum, steel, titanium and bronze, composites and alloys
thereof, and combinations thereof.

3. The abrasive tool of claim 1, wherein the abrasive
segments comprise 60 to 84.5 volume % metal bond matrix, 0.5
to 5 volume % abrasive grain, and 15 to 35 volume % friable
filler, and the metal bond matrix comprises a maximum of 5
volume % porosity.

4. The abrasive tool of claim 1, wherein the friable filler
is selected from the group consisting of graphite, hexagonal
boron nitride, hollow ceramic spheres, feldspar, nepheline
syenite, pumice, calcined clay and glass spheres, and
combinations thereof.

5. The abrasive tool of claim 1, wherein the abrasive grain
is selected from the group consisting of diamond and cubic
boron nitride and combinations thereof.

6. The abrasive tool of claim 5, wherein the abrasive grain
is diamond having a grit size of 2 to 300 micrometers.

7. The abrasive tool of claim 1, wherein the metal bond
comprises 35 to 84 wt% copper and 16 to 65 wt% tin.

8. The abrasive tool of claim 7, wherein the metal bond
further comprises 0.2 to 1.0 wt% phosphorus.

9. The abrasive tool of claim 1, wherein the abrasive tool
comprises at least two abrasive segments and the abrasive
segments have an elongated, arcurate shape and an inner


28



curvature selected to mate with the circular perimeter of the
core, and each abrasive segment has two ends designed to mate
with adjacent abrasive segments such that the abrasive rim is
continuous and substantially free of any gaps between abrasive
segments when the abrasive segments are bonded to the core.

10. The abrasive tool of claim 1, wherein the tool is
selected from the group consisting of type 1A1 wheels and cup
wheels.

11. The abrasive tool of claim 1, wherein the thermally
stable bond is selected from the group consisting essentially
of an epoxy adhesive bond, a metallurgical bond, a mechanical
bond and a diffusion bond, and combinations thereof.


29

Description

Note: Descriptions are shown in the official language in which they were submitted.



CA 02324578 2004-O1-12
ABRASIVE TOOLS
This application is related to U.S. Patent 6,102,789.
The invention relates to abrasive tools suitable for precision
grinding of hard brittle materials, such as ceramics and
composites comprising ceramics, at peripheral wheel speeds up
to 160 meters/second, and suitable for surface grinding of
ceramic wafers. The abrasive tools comprise a wheel core or
hub attached to a metal bonded superabrasive rim with a bond
which is thermally stable during grinding operations. These
abrasive tools grind ceramics at high material removal rates
(e. g., 19-380 cm3/min/cm), with less wheel wear and less
workpiece damage than conventional abrasive tools.
An abrasive tool suitable for grinding sapphire and other
ceramic materials is disclosed in U.S.A - 5,607,489 to Li.
The tool is described as containing metal clad diamond bonded
in a vitrified matrix comprising 2 to 20 volume % of solid
lubricant and at least 10 volume % porosity.
An abrasive tool containing diamond bonded in a metal
matrix with 15 to 50 volume % of selected fillers, such as
graphite, is disclosed in U.S.A. - 3,925,035 to Keat. The
tool is used for grinding cemented carbides.
A cutting-off wheel made with metal bonded diamond
abrasive grain is disclosed in U.S.A. - 2,238,351 to Van der
Pyl. The bond consists of copper, iron, tin, and, optionally,
nickel and the bonded abrasive grain is sintered onto a steel
core, optionally with a soldering step to insure adequate
adhesion. The best bond is reported to have a Rockwell B
hardness of 70.
An abrasive tool containing fine diamond grain (bort)
bonded in a relatively low melting temperature metal bond,
such as a bronze bond, is disclosed in U.S.-Re-21,165. The
low melting bond serves to avoid oxidation of the fine diamond
grain. An abrasive rim is constructed as a single, annular
abrasive segment and then attached to a central disk of
aluminum or other material.
None of these abrasive tools have proven entirely
satisfactory in the precision grinding of ceramic components.
1


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
These tools fail to meet rigorous specifications for part
shape, size and surface quality when operated at commercially
feasible grinding rates. Most commercial abrasive tools
recommended for use in such operations are resin or vitrified
bonded superabrasive wheels designed to operate at relatively
low grinding efficiencies so as to avoid surface and
subsurface damage to the ceramic components. Grinding
efficiencies are further reduced due to the tendency of
ceramic workpieces to clog the wheel face, requiring frequent
wheel dressing and truing to maintain precision forms.
As market demand has grown for precision ceramic
components in products such as engines, refractory equipment
and electronic devices (e.g., wafers, magnetic heads and
display windows), the need has grown for improved abrasive
tools for precision grinding of ceramics.
In finishing high performance ceramic materials, such as
alumina titanium carbide (AlTiC), for electronic components,
surface grinding or "backgrinding" operations demand high
quality, smooth surface finishes in low force, relatively low
speed grinding operations. In backgrinding these materials,
grinding efficiency is determined as much by workpiece surface
quality and control of applied force as by high material
removal rates and abrasive wheel wear resistance.
The invention is a surface grinding abrasive tool
comprising a core, having a minimum specific strength
parameter of 2.4 MPa-cm3/g, a core density of 0.5 to 8.0
g/cm3, a circular perimeter, and an abrasive rim defined by a
plurality of abrasive segments; wherein the abrasive segments
comprise, in amounts selected to total a maximum of 100 vol %,
from 0.05 to 10 vol % superabrasive grain, from 10 to 35 vol %
friable filler, and from 55 to 89.95 vol % metal bond matrix
having a fracture toughness of 1.0 to 3.0 MPa M1/2. The
specific strength parameter is defined as the ratio of the
lesser of the yield strength or the fracture strength of the
material divided by the density of the material. The friable
filler is selected from the group consisting of graphite,
hexagonal boron nitride, hollow ceramic spheres, feldspar,
nepheline syenite, pumice, calcined clay and glass spheres,
2


CA 02324578 2000-09-19
WO 99/48646 PCTNS99/02399
and combinations thereof. In a preferred embodiment, the
metal bond matrix comprises a maximum of 5. vol % porosity.
Description of the Drawincts
Figure 1 illustrates a continuous rim of abrasive
segments bonded to the perimeter of a metal core to form a
type lAl abrasive grinding wheel.
Figure 2 illustrates a discontinuous rim of abrasive
segments bonded to the perimeter of a metal core to form a cup
wheel.
Figure 3 illustrates the relationship between quantity of
stock removed and normal force during grinding of an AlTiC
workpiece with the abrasive grinding wheels of Example 5.
The abrasive tools of the invention are grinding wheels
comprising a core having a central bore for mounting the wheel
on a grinding machine, the core being designed to support a
metal bonded superabrasive rim along the periphery~of the
wheel. These two parts of the wheel are held together with a
bond which is thermally stable under grinding conditions, and
the wheel and its components are designed to tolerate stresses
generated at wheel peripheral speeds of up to at least 80
m/sec, preferably up to 160 m/sec. Preferred tools are type
lA wheels, and cup wheels, such as type 2 or type 6 wheels or
type 11V9 bell shaped cup wheels.
The core is substantially circular in shape. The core
may comprise any material having a minimum specific strength
of 2.4 MPa-cm3/g, preferably 40-185 MPa-cm3/g. The core
material has a density of 0.5 to 8.0 g/cm3, preferably 2.0 to
8.0 g/cm3. Examples of suitable materials are steel,
aluminum, titanium and bronze, and their composites and alloys
and combinations thereof. Reinforced plastics having the
designated minimum specific strength may be used to construct
the core. Composites and reinforced core materials typically
have a continuous phase of a metal or a plastic matrix, often
in powder form, to which fibers or grains or particles of
harder, more resilient, and/or less dense, material is added
as a discontinuous phase. Examples of reinforcing materials
suitable for use in the core of the tools of the invention are
glass fiber, carbon fiber, aramid fiber, ceramic fiber,
3


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
ceramic particles and grains, and hollow filler materials such
as glass, mullite, alumina and Zeolite~ spheres.
Steel and other metals having densities of 0.5 to 8.0
g/cm3 may be used to make the cores for the tools of the
invention. In making the cores used for high speed grinding
(e. g., at least 80 m/sec), light weight metals in powder form
(i.e., metals having densities of about 1.8 to 4.5 g/cm3),
such as aluminum, magnesium and titanium, and alloys thereof,
and mixtures thereof, are preferred. Aluminum and aluminum
alloys are especially preferred. Metals having sintering
temperatures between 400 and 900° C, preferably 570-650°C, are
selected if a co-sintering assembly process is used to make
the tools. Low density filler materials may be added to
reduce the weight of the core. Porous and/or hollow ceramic
or glass fillers, such as glass spheres and mullite spheres
are suitable materials for this purpose. Also useful are
inorganic and nonmetallic fiber materials. When indicated by
processing conditions, an effective amount of lubricant or
other processing aids known in the metal bond and
superabrasive arts may be added to the metal powder before
pressing and sintering.
The tool should be strong, durable and dimensionally
stable in order to withstand the potentially destructive
forces generated by high speed operation. The core must have
a minimum specific strength to operate grinding wheels at the
very high angular velocity needed to achieve tangential
contact speed between 80 and 160 m/s. The minimum specific
strength parameter needed for the core materials used in this
invention is 2.4 MPa-cm'/g.
The specific strength parameter is derined as the ratio
of core material yield (or fracture) strength divided by core
material density. In the case of brittle materials, having a
lower fracture strength than yield strength, the specific
strength parameter is determined by using the lesser number,
the fracture strength. The yield strength of a material is
the minimum force applied in tension for which strain of the
material increases without further increase of force. For
example, ANSI 4140 steel hardened to above about 240 (Brinell
4


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
scale) has a tensile strength in excess of 700 MPa. Density
of this steel is about 7.8 g/cm'. Thus, its specific strength .
parameter is about 90 MPa-cm'/g. Similarly, certain aluminum
alloys, for example, A1 2024, A1 7075 and A1 7178, that are
heat treatable to Brinell hardness above about 100 have
tensile strengths higher than about 300 MPa. Such aluminum
alloys have low density of about 2.7 g/cm3 and thus exhibit a
specific strength parameter of more than 110 MPa-cm3/g.
Titanium alloys and bronze composites and alloys fabricated to
have a density no greater than 8.0 g/cm3, are also suitable
for use.
The core material should be tough, thermally stable at
temperatures reached in the grinding zone (e.g., about 50 to
200 °C), resistant to chemical reaction with coolants and
lubricants used in grinding and resistant to wear by erosion
due to the motion of cutting debris in the grinding zone.
Although some alumina and other ceramics have acceptable
failure values (i.e., in excess of 60 MPa-cm3/g), they
generally are too brittle and fail structurally in high speed
grinding due to fracture. Hence, ceramics are not suitable
for use in the tool core. Metal, especially hardened, tool
quality steel, is preferred.
The abrasive segment of the grinding wheel for use with
the present invention is a segmented or continuous rim mounted
on a core. A segmented abrasive rim is shown in Fig. 1. The
core 2 has a central bore 3 for mounting the wheel to an arbor
of a power drive (not shown). The abrasive rim of the wheel
comprises superabrasive grains 4 embedded (preferably in
uniform concentration) in a metal matrix bond 6. A plurality
of abrasive segments 8 make up the abrasive rim shown in Fig.
1. Although the illustrated embodiment shows ten segments,
the number of segments is not critical. An individual
abrasive segment, as shown in Fig. 1, has a truncated,
rectangular ring shape (an arcurate shape) characterized by a
length, 1, a width, w, and a depth, d.
The embodiment of a grinding wheel shown in Fig. 1 is _
considered representative of wheels which may be operated
successfully according to the present invention, and should
5


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
not be viewed as limiting. The numerous geometric variations
for segmented grinding wheels deemed suitable include cup-
shaped wheels,. as shown in Fig. 2, wheels with apertures
through the core and/or gaps between consecutive segments, and
wheels with abrasive segments of different width than the
core. Apertures or gaps are sometimes used to provide paths
to conduct coolant to the grinding zone and to route cutting
debris away from the zone. A wider segment than the core
width is occasionally employed to protect the core~structure
from erosion through contact with swarf material as the wheel
radially penetrates the work piece.
The wheel can be fabricated by first forming individual
segments of preselected dimension and then attaching the pre-
formed segments to the circumference 9 of the core with an
appropriate adhesive. Another preferred fabrication method
involves forming segment precursor units of a powder mixture
of abrasive grain and bond, molding the composition around the
circumference~of the core, and applying heat and pressure to
create and attach the segments, in situ (i.e., co-sintering
the core and the rim). A co-sintering process is preferred
for making surface grinding cup wheels used to backgrind
wafers and chips of hard ceramics such as AlTiC.
The abrasive rim component of the abrasive tools of the
invention pan be a continuous rim or a discontinuous rim, as
shown in Figures 1 and 2, respectively. The continuous
abrasive rim may comprise one abrasive segment, or at least
two abrasive segments, sintered separately in molds, and then
individually mounted on the core with a thermally stable bond
(i.e., a bond stable at the temperatures encountered during
grinding at the portion of the segments directed away from the
grinding face, typically about 50-350° C). Discontinuous
abrasive rims, as shown in Fig. 2, are manufactured from at
least two such segments, and the segments are separated by
slots or gaps in the rim and are not mated end to end along
their lengths, l, as in the segmented, continuous abrasive rim
wheels. The Figures illustrate preferred embodiments of the
invention, and are not meant to limit the types of tool
6


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
designs of the invention, e.g., discontinuous rims may be used
on lA wheels and continuous rims may be used on cup wheels.
For high speed grinding, especially grinding of
workpieces having a cylindrical shape, a continuous rim, type
lA wheel is preferred. Segmented continuous abrasive rims are
preferred over a single continuous abrasive rim, molded as a
single piece in a ring shape, due to the greater ease of
achieving a truly round, planar shape during manufacture of a
tool fram multiple abrasive segments.
For lower speed grinding (e. g., 25 to 60 m/sec)
operations, especially grinding of surfaces and finishing flat
workpieces, discontinuous abrasive rims (e. g., the cup wheel
shown in Figure 2) are preferred. Because surface quality is
critical in low speed surface finishing operations, slots may
be formed in the segments, or some segments may be omitted
from the rim to aid in removal of waste material which could
scratch the workpiece surface.
The abrasive rim component contains superabrasive grain
held in a metal matrix bond, typically formed by sintering a
mixture of metal bond powder and the abrasive grain in a mold
designed to yield the desired size and shape of the abrasive
rim or the abrasive rim segments.
The superabrasive grain used in the abrasive rim may be
selected from diamond, natural and synthetic, CBN, and
combinations of these abrasives. Grain size and type
selection will vary depending upon the nature of the workpiece
and the type of grinding process. For example, in the
grinding and polishing of sapphire or AlTiC, a superabrasive
grain size ranging from 2 to 300 micrometers is preferred.
For grinding other alumina, a~superabrasive grain size of
about 125 to 300 micrometers (60 to 120 grit; Norton Company
grit size) is generally preferred. For grinding silicon
nitride, a grain size of about 45 to 80 micrometers (200 to
400 grit), is.generally preferred. Finer grit sizes are
preferred for surface finishing and larger grit sizes are
preferred for cylindrical, profile or inner diameter grinding
operations where larger amounts of material are removed.
7


CA 02324578 2000-09-19
WO 99/48646 PCTNS99/02399
As a volume percentage of the abrasive rim, the tools
comprise 0.05 to 10 volume % superabrasive grain, preferably
0.5 to 5 volume %. A minor amount of a friable filler
material having a hardness less than that of the metal bond
matrix, may be added as bond filler to increase the wear rate
of the bond. As a volume percentage of the rim component, the
filler may be used at 10 to 35 volume %, preferably 15 to 35
volume %. Suitable friable filler material must be
characterized by suitable thermal and mechanical properties to
survive the sintering temperature and pressure conditions used
to manufacture the abrasive segments and assemble the wheel.
Graphite, hexagonal boron nitride, hollow ceramic spheres,
feldspar, nepheline syenite, pumice, calcined clay and glass
spheres, and combinations thereof, are examples of. useful
friable filler materials.
Any metal bond suitable for bonding superabrasives and
having a fracture toughness of 1.0 to 6.0 MPa~ml~2, preferably
2.0 to 4.0 MPa~ml~z, may be employed herein. Fracture toughness
is the stress intensity factor at which a crack initiated in a
material will propagate in the material and lead to a fracture
of the material. Fracture toughness is expressed as
Klc = (6f) (y/z) (ci/2) . where
K1~ is the fracture toughness, of is the stress applied at
fracture, and c is one-half of the crack length. There are
several methods which may be used to determine fracture
toughness, and each has an initial step where a crack of known
dimension is generated in the test material, and then a stress
load is applied until the material fractures. The.stress at
fracture and crack length are substituted into the equation
and the fracture toughness is calculated (e. g., the fracture
toughness of steel is about 30-60 Mpa.ml/Z, of alumina is about
2-3 MPa.ml/Z, of silicon nitride is about 4-5 Mpa.ml~2, and of
zirconia is about 7-9 Mpa.ml~2) .
To optimize wheel life and grinding performance, the bond
wear rate should be equal to or slightly higher than the wear
rate of the abrasive grain during grinding operations.
Fillers, such as are mentioned above, may be added to the
metal bond to decrease the wheel wear rate. Metal powders
a


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
tending to form a relatively dense bcnd structure (i.e., less
than 5 volume % porosity) are preferred to enable higher
material removal rates during grinding. .
Materials useful in the metal bond of the rim include,
but are not limited to, bronze, copper and zinc alloys
(brass), cobalt and iron, and their alloys and mixtures
thereof. These metals optionally may be used with titanium or
titanium hydride, or other superabrasive reactive (i.e.,
active bond components) material capable of forming a carbide
or nitride chemical linkage between the grain and the bond at
the surface of the superabrasive grain under the selected
sintering conditions to strengthen the grain/bond posts.
Stronger grain/bond interactions will limit premature loss of
grain and workpiece damage and shortened tool life caused by
premature grain loss.
In a preferred embodiment of the abrasive rim, the metal
matrix comprises 55 to 89.95 volume % of the rim, more
preferably 60 to 84.5 volume %. The friable filler comprises
10 to 35 volume % of the abrasive rim, preferably 15 to 35
volume %. Porosity of the metal matrix bond should be
maintained at a maximum of 5 volume % during manufacture of
the abrasive segment. The metal bond preferably has a Knoop
hardness of 2 to 3 GPa.
In a preferred embodiment of a type lA grinding wheel,
the core is made of aluminum and the rim contains a bronze
bond made from copper and tin powders (80/20 wt. %), and,
optionally with the addition of 0.1 to 3.0 wt %,.preferably
0.1 to 1.0 wt %, of phosphorus in the form of a
phosphorus/copper powder. During manufacture of the abrasive
segments, the metal powders of this composition are mixed with
100 to 400 grit (160 to 45 microns) diamond abrasive grain,
molded into abrasive rim segments and sintered or densified in
the range of 400-550° C at 20 to 33 MPa to yield a.dense
abrasive rim, preferably having a density of at least 95 % of
the theoretical density (i.e., comprising no more than about 5
volume % porosity).
In a typical co-sintering wheel manufacturing process,
the metal powder of the core is poured into a steel mold and
9


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
cold pressed at 80 to 200 kN (about 10-50 MPa pressure) to
form a green part having a size approximately 1.2 to 1.6 times
the desired final thickness of the core. The green core part
is placed in a graphite mold and a mixture of the abrasive
grain (2 to 300 micrometers grit size) and the metal bond
powder blend is added to the cavity between the core and the
outer rim of the graphite mold. A setting ring may be used to
compact the abrasive and metal bond powders to the same
thickness as the core preform. The graphite mold contents are
then hot pressed at 370 to 410°C under 20 to 48 MPa of
pressure for 6 to 10 minutes. As is known in the art, the
temperature may be ramped up (e.g., from 25 to 410°C for 6
minutes; held at 410°C for 15 minutes) or increased gradually
prior to applying pressure to the mold contents.
Following hot pressing, the graphite mold is stripped
from the part, the part is cooled and the part is finished by
conventional techniques to yield an abrasive rim having the
desired dimensions and tolerances. For example, the part may
be finished to size using vitrified grinding wheels on
grinding machines or carbide cutters on a lathe.
When co-sintering the core and rim of the invention,
little material removal is needed to put the part into its
final shape. In other methods of forming a thermally stable
bond between the abrasive rim and the core, machining of both
the core and the rim may be needed, prior to a cementing,
linking or diffusion step, to insure an adequate surface for
mating and bonding of the parts.
In creating a thermally stable bond between the rim and
the core utilizing segmented abrasive rims, any thermally
stable adhesive having the strength to withstand peripheral
wheel speeds up to 160 m/sec may be used. Thermally stable
adhesives are stable to grinding process temperatures likely
to be encountered at the portion of the abrasive segments
directed away from the grinding face. Such temperatures
typically range from about 50-350° C.
The adhesive bond should be very strong mechanically to
withstand the destructive forces existing during rotation of
the grinding wheel and during the grinding operation. Two-


CA 02324578 2000-09-19
WO 99/48b4b PCT/US99/02399
part epoxy resin cements are preferred. A preferred epoxy
cement, Technodyne~ HT-18 epoxy resin (obtained from Taoka
Chemicals, Japan), and its modified amine hardener, may be
mixed in the ratio of 100 parts resin to 19 parts hardener.
Filler, such as fine silica powder, may be added at a ratio of
3.5 parts per 100 parts resin to increase cement viscosity.
Segments may be mounted about the complete circumference of
grinding wheel cores, or a partial circumference of the core,
with the cement. The perimeter of the metal cores may be
sandblasted to obtain a degree of roughness prior to
attachment of the segments. The thickened epoxy cement is
applied to the ends and bottom of segments which are
positioned around the core substantially as shown in Fig. 1
and mechanically held in place during the cure. The epoxy
cement is allowed to cure (e.g., at room temperature for 24
hours followed by 48 hours at 60°C). Drainage of the cement
during curing and movement of the segments is minimized during
cure by the addition of sufficient filler to optimize the
viscosity of the epoxy cement.
Adhesive bond strength may be tested by spin testing at
acceleration of 45 rev/min, as is done to measure the burst
speed of the wheel. The wheels need demonstrated burst
ratings equivalent to at least 271 m/s tangential contact
speeds to qualify for operation under currently applicable
safety standards 160 m/s tangential contact speed in the
United States.
The abrasive tools of the invention are particularly
designed for precision grinding and finishing of brittle
materials, such as advanced ceramic materials, glass, and
components containing ceramic materials and ceramic composite
materials. The tools of the invention are preferred for
grinding ceramic materials including, but not limited to,
silicon, mono- and polycrystalline oxides, carbides, borides
and silicides; polycrystalline diamond; glass; and composites
of ceramic in a non-ceramic matrix; and combinations thereof.
Examples of typical workpiece materials include, but are not _
limited to, AlTiC, silicon nitride, silicon oxynitride,
stabilized zirconia, aluminum oxide (e. g., sapphire), boron
11


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
carbide, boron nitride, titanium diboride, and aluminum
nitride, and composites of these ceramics, as well as certain
metal matrix composites such as cemented carbides, and hard
brittle amorphous materials such as mineral glass. Either
single crystal ceramics or polycrystalline ceramics can be
ground with these improved abrasive tools. With each type of
ceramic, the quality of the ceramic part and the efficiency of
the grinding operation increase as the peripheral wheel speed
of the wheels of the invention is increased up to 80-160 m/s.
Among the ceramic parts improved by using the abrasive
tools of the invention are ceramic engine valves and rods,
pump seals, ball bearings and fittings, cutting tool inserts,
wear parts, drawing dies for metal forming, refractory
components, visual display windows, flat glass for
windshields, doors and windows, insulators and electrical
parts, and ceramic electronic components, including, but not
limited to, silicon wafers, AlTiC chips, read-write heads
magnetic heads, and substrates.
Unless otherwise indicated, all. parts and percentages in
the following examples are by weight. The examples merely
illustrate the invention and are not intended to limit the
invention.
Example 1
Abrasive wheels of the invention were prepared in the
form of lAl metal bonded diamond wheels utilizing the
materials and processes described below.
A blend of 43.74 wt % copper powder (Dendritic FS grade,
particle size +200/-325 mesh, obtained from Sintertech
International Marketing Corp., Ghent, NY); 6.24 wt%
phosphorus/copper powder (grade 1501, +100/-325 mesh particle
size, obtained from New Jersey Zinc Company, Palmerton, PA);
and 50.02 wt% tin powder (grade MD115, +325 mesh, 0.5%
maximum, particle size, obtained from Alcan Metal Powders,
Inc., Elizabeth, New Jersey) was prepared. Diamond abrasive
grain (320 grit size synthetic diamond obtained from General
Electric, Worthington, Ohio) was added to the metal powder
blend and the combination was mixed until it was uniformly
12


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
blended. The mixture was placed in a graphite mold and hot
pressed at 407°C for 15 minutes at 3000 psi (2073 N/cmz)
until a matrix with a target density in excess of 95% of
theoretical had been formed (e.g., for the #6 wheel used in
Example 2: > 98.5% of the theoretical density). Rockwell B
hardness of the segments produced for the #6 wheel was 108.
Segments contained 18.75 vol. % abrasive grain. The segments
were ground to the required arcurate geometry to match the
periphery of a machined aluminum core (7075 T6 aluminum,
obtained from Yarde Metals, Tewksbury, MA), yielding a wheel
with an outer diameter of about 393 mm, and segments 0.62 cm
thick.
The abrasive segments and the aluminum core were
assembled with a silica filled epoxy cement system~(Technodyne
HT-18 adhesive, obtained from Taoka Chemicals, Japan ) to
make grinding wheels having a continuous rim consisting of
multiple abrasive segments. The contact surfaces of the core
and the segments were degreased and sandblasted to insure
adequate adhesion.
To characterize the maximum operating speed of this new
type of wheel, full size wheels were purposely spun to
destruction to determine the burst strength and rated maximum
operating speed according to the Norton Company maximum
operating speed test method. The table below summarizes the
burst test data for typical examples of the 393-mm diameter
experimental metal bonded wheels.
13


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WO 99/48646 PCT/US99/02399
Experimental Metal Bond Wheel Burst Strength Data
Wheel Wheel Burst Burst Burst Max.


# Diameter RPM speed speed Operating


cm ( inch) (m/s ) Speed


(sfpm) (m/s)


39.24 9950 204.4 40242 115.8


(15.45)


39.29 8990 185.0 36415 104.8


(15.47)


7 39.27 7820 160.8 31657 91.1


(15.46)


9 39.27 10790 221.8 43669 125.7


(15.46)


According to these data, the experimental grinding wheels
of this design will qualify for an operational speed up to 90
5 m/s (17,717 surface feet/min.). Higher operational speeds of
up to 160 m/s can be readily achieved by some further
modifications in fabrication processes and wheel designs.
Example 2
Grinding Performance Evaluation:
Three, 393-mm diameter, 15 mm thick, 127 mm central bore,
(15.5 in x 0.59 in x 5 in) experimental metal bonded segmental
wheels made according to the method of Example 1, above, (#4
having segments with a density of 95.6 % of theoretical, #5 at
97.9 % of theoretical and #6 at 98.5 % of theoretical density)
were tested for grinding performance. Initial testing at 32
and 80 m/s established wheel #6 as the wheel having the best
grinding performance of the three, although all experimental
wheels were acceptable. Testing of wheel #6 was done at three
speeds: 32 m/s (6252 sfpm), 56 m/s (11,000 sfpm), and 80 m/s
(15,750 sfpm). Two commercial prior art abrasive wheel
recommended for grinding advanced ceramic materials served as
control wheels and they were tested along with the wheels of
the invention. One was a vitrified bonded diamond wheel
(SD320-N6V10 wheel obtained from Norton Company, Worcester,
MA) and the other was a resin bonded diamond wheel (SD320-
R4BX619C wheel obtained from Norton Company, Worcester, MA).
14


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The resin wheel was tested at all three speeds. The vitrified
wheel was tested at 32 m/s (6252 sfpm) only, due to speed
tolerance considerations.
Over one thousand plunge grinds of 6.35 mm (0.25 inch)
wide and 6.35 mm (0.25 inch) deep were performed on silicon
nitride workpieces. The grinding testing conditions were:
Grinding Test Conditions:
Machine: Studer Grinder Model S40 CNC
Wheel Specifications: SD320-R4BX619C, SD320-N6V10,
Size . 393mm diameter, 15 mm thickness and
127 mm hole.
Wheel Speed: 32, 56, and 80 m/s (6252, 11000, and 15750
sfpm)
Coolant: Inversol 22 Q60% oil and 40% water
Coolant Pressure: 270 psi (19 kg/cm2)
Material Removal Rate: Vary, starting at 3.2 mm3/s/mm (0.3
in3 /min/ in)
Work Material: S13N4 (rods made of NT551 silicon nitride,
obtained from Norton Advanced Ceramics, Northboro,
Massachusetts) 25.4 mm (1 in.) diameter X 88.9 mm (3.5 in.)
long
Work Speed: 0.21 m/s (42 sfpm), constant
Work Starting diameter: 25.4 mm (1 inch)
Work finish diameter: 6.35 mm (0.25 inch)
For operations requiring truing and dressing, conditions
suitable for the metal bonded wheels of the invention were:
Truing Operation:
Wheel: 5SG46IVS (obtained from Norton Company)
Wheel Size: 152 mm diameter (6 inches)
Wheel Speed: 3000 rpm; at +0.8 ratio relative to
the grinding wheel
Lead: 0.015 in.(0.38mm)
Compensation: 0.0002 in.
Dressing Operation:
Stick: 37C220H-KV (SiC)
Mode: Hand Stick Dressing .


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
Tests were performed in a cylindrical outer diameter
plunge mode in grinding the silicon nitride rods. To preserve
the best stiffness of work material during grinding, the 88.9
mm (3.5 in.) samples were held in a chuck with approximately
31 mm (1-1/4 in.) exposed for grinding. Each set of plunge
grind tests started from the far end of each rod. First, the
wheel made a 6.35 mm (1/4 in.) wide and 3.18 mm (1/8 in.)
radial depth of plunge to complete one test. The work rpm was
then re-adjusted to compensate for the loss of work speed due
to reduced work diameter. Two more similar plunges were
performed at the same location to reduce the work diameter
from 25.4 mm (1 in.) to 6.35 mm (1/4 in.). The wheel was then
laterally moved 6.35 mm (1/4 in.) closer to the chuck to
perform next three plunges. Four lateral movements were
performed on the same side of a sample to complete the twelve
plunges on one end of a sample. The sample was then reversed
to expose the other end for another twelve grinds. A total of
24 plunge grinds was done on each sample.
The initial comparison tests for the metal bonded wheels
of the invention and the resin and vitrified wheels were
conducted at 32 m/s peripheral speed at three material removal
rates (MRR') from approximately 3.2 mm3/s/mm (0.3 in3/min/in)
to approximately 10.8 mm3/s/mm (1.0 in3/min/in). Table 1
shows the performance differences, as depicted by G-ratios,
among the three different types of wheels after twelve plunge
grinds. G-ratio is the unit-less ratio of volume material
removed over volume of wheel wear. The data showed that the N
grade vitrified wheel had better G ratios than the R grade
resin wheel at the higher material removal rates, suggesting
that a softer wheel performs better in grinding a ceramic
workpiece. However, the harder, experimental, metal bonded
wheel (#6) was far superior to the resin wheel and the
vitrified wheel at all material removal rates.
Table 1 shaves the estimated G-ratios for the resin wheel
and the new metal bonded wheel (#6) at all material removal
rate conditions. Since there was no measurable wheel wear
after twelve grinds at each material removal rate for the
metal bonded wheel, a symbolic value of 0.01 mil (0.25 ~tm)
16


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WO 99/48646 PCT/US99/02399
radial wheel wear was given for each grind. This yielded the
calculated G-ratio of 6051.
Although the metal bond wheel of the invention contained
75 diamond concentration (about 18.75 volume % abrasive grain
in the abrasive segment), and the resin and vitrified wheels
were 100 concentration and 150 concentration (25 volume % and
37.5 volume %), respectively, the wheel of the invention still
exhibited superior grinding performance. At these relative
grain concentrations, one would expect superior grinding
performance from the control wheels containing a higher volume
% of abrasive grain. Thus, these results were unexpected.
Table 1 shows the surface finish (Ra) and waviness (Wt)
data measured on samples ground by the three wheels at the low
test speed. The waviness value, Wt, is the maximum peak to
valley height of the waviness profile. All surface finish
data were measured on surfaces created by cylindrical plunge
grinding without spark-out. These surfaces normally would be
rougher than surfaces created by traverse grinding.
Table 1 shows the difference in grinding power
consumption.at various material removal rates for the three
wheel types. The resin wheel had lower power consumption than
the other two wheels; however, the experimental metal bonded
wheel and vitrified wheel had comparable power consumption.
The experimental wheel drew an acceptable amount of power for
ceramic grinding operations, particularly in view of the
favorable G-ratio and surface finish data observed for the
wheels of the invention. In general, the wheels of the
invention demonstrated power draw proportional to material
removal rates.
17

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WO 99/48646 PCTNS99/02399
TABLE 1
Sample MRR' Wheel Tangen Unit SpecificG- SurfaceWavi-


mm3/s/ Speed -tial PowerEnergy Ratio Finish ness


mm m/s Force W/mm W~s/mm3 Ra ~m Wt
~tm


N/mm



Resin


973 3.2 32 0.48 40 12.8 585.9 0.52 0.86


1040 6.3 32 0.98 84 13.3 36.6 0.88 4.01


980 8.9 32 1.67 139 9.5 7.0 0.99 4.50


1016 3.2 56 0.49 41 13.1 586.3 0.39 1.22


1052 6.3 56 0.98 81 12.9 0.55 1.52


293.2


992 3.2 80 0.53 45 14.2 586.3 0.42 1.24


1064 6.3 80 0.89 74 11.8 293.2 0.62 1.80


1004 9.0 80 1.32 110 12.2 586.3 0.43 1.75


Vitrified


654 3.2 32 1.88 60 19.2 67.3 0.7 2.50


666 9.0 32 4.77 153 17.1 86.5 1.6 5.8


678 11.2 32 4.77 153 13.6 38.7 1.7 11.8


Metal Exflerimeatal
407 3.2 32 2.09 67 2.1 6051 0.6 0.9


419 6.3 32 4.03 130 20.6 6051 0.6 0.9


431 9.0 32 5.52 177 19.7 6051 0.6 0.8


443 3.2 56 1.41 80 25.4 6051 0.6 0.7


455 6.3 56 2.65 150 23.9 6051 0.5 0.7


46? 9.0 56 3.70 209 23.3 6051 0.5 0.6


479 3.2 80 1.04 85 26.9 6051 0.5 1.2


491 6.3 80 1.89 153 24.3 6051 0.6 0.8


503 9.0 80 2.59 210 23.4 6051 0.6 0.8


When grinding performance was measured at 80 m/s (15,750
sfpm) in an additional grinding test under the same
conditions, the resin wheel and experimental metal wheel had
comparable power consumption at material removal rate (MRR) of-
9.0 mm3/s/mm (0.8 in3/min/in). As shown in Table 2, the
experimental wheels were operated at increasing MRRs without
18


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WO 99/48646 PCT/US99/02399
loss of performance or unacceptable power loads. The metal
bonded wheel power draw was roughly proportional to the MRR.
The highest MRR achieved in this study was 47.3 mm3/s/mm
(28.4cm3/min/cm) .
Table 2 data are averages of twelve grinding passes.
Individual power readings for each of the twelve passes
remained remarkably consistent for the experimental wheel
within each material removal rate. One would normally observe
an increase of power as successive grinding passes are carried
and the abrasive grains in the wheel begins to dull or the
face of the wheel becomes loaded with workpiece material.
This is often observed as the MRR is increased. However, the
steady power consumption levels observed within each MRR
during the twelve grinds demonstrates, unexpectedly, that the
experimental wheel maintained its sharp cutting points during
the entire length of the test at all MRRs.
Furthermore, during this entire test, with material
removal rates ranging from 9.0 mm3/s/mm (0.8 in3/min/in) to
47.3 mm3/s/mm (4.4 in3/min/in), it was not necessary to true
or dress the experimental wheel.
The total, cummulative amount of silicon nitride material
ground without any evidence of wheel wear was equivalent to
271 cm3 per cm (42 in3 per inch) of wheel width. By contrast,
the G-ratio for the 100 concentration resin wheel at 8.6
mm3/s/mm (0.8 in3/miri/in) material removal rate was
approximately 583 after twelve plunges. The experimental
wheel showed no measurable wheel wear after 168 plunges at 14
different material removal rates.
Table 2 shows that the samples ground by the experimental
metal bonded wheel at all 14 material removal rates maintained
constant surface finishes between 0.4 ~,m (16 din.) and 0.5 ~tm
(20 din.), and had waviness values between 1.0 ~,m (38 din.)
and 1.7 ~m (67 ~.in.). The resin wheel was not tested at these
high material removal rates. However, at about 8.6 mm3/s/mm
(0.8 in3/min/in) material removal rate, the ceramic bars
ground by the resin wheel had slightly better but comparable -
surface finishes (0.43 versus 0.5 Vim, and poorer waviness
(1.73 versus 1.18 Vim).
19


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WO 99/48646 PCT/US99/02399
Surprisingly, therewas apparent deterioration in
no


surface finish whe n ceramicrods were ground with the
the new


metal bonded wheel as e material removal rate increased.
th


This is in contras t he commonly inish
to observed
t surface
f


deterioration with increase rates for standard whe els,
cut


such as the contro l ls usedherein.
whee


Overall resul ts metal
demonstrate
that
the
experimental


wheel was able to grindeffectively over
at 5
a MRR
which
was


times the MRR achi evablewith standard, commercially used
a


resin bond wheel. The xperimental times
e wheel
had
over
10


the G-ratio compar ed the in wheel at the lower
to res MRRs.


TAHLE
2


14 MRRs 80 m/s Wheel Speed
Tested
At



Sample MRR' Tangen- Unit Specific G- Surface
Waviness


mm3 tial Power Energy Ratio Finish Wt ~tm


/s/m ForceW/mm Ws/mm3 Ra ~m


m N/mm



Resin


1004 9.0 1.32 110 12.2 586.3 0.43 1.75


Metal


Invention


805 9.0 1.21 98 11.0 6051 0.51 1.19


817 18.0 2.00 162 9.0 6051 0.41 0.97


829 22.5 2.62 213 9.5 6051 0.44 1.14


841 24.7 2.81 228 9.2 6051 0.47 1.04


853 27.0 3.06 248 9.2 6051 0.48 1.09


865 29.2 3.24 262 9.0 6051 0.47 1.37


877 31.4 3.64 295 9.4 6051 0.47 1.42


889 33.7 4.01 325 9.6 6051 0.44 1.45


901 35.9 4.17 338 9.4 6051 0.47 1.70


913 38.2 4.59 372 9.7 6051 0.47 1.55


925 40.4 4.98 404 10.0 6051 0.46 1.55


937 42.7 5.05 409 9.6 6051 0.44 1.57


949 44.9 5.27 427 9.5 6051 0.47 1.65


961 4T.2 5.70 461 9.8 6051 0.46 1.42


20


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WO 99/48646 PCT/US99/02399
When operated at 32 m/s (6252 sfpm) and 56 m/s (11,000
sfpm) wheel speeds (Table 1), the power cansumption for the
metal bonded wheel was higher than that of resin wheel at all
of the material removal rates tested. However, the power
consumption for the metal bonded wheel became comparable or
slightly less than that of resin wheel at the high wheel speed
of 80 m/s (15,750 sfpm) (Tables 1 and 2). Overall, the trend
showed that the power consumption decreased with increasing
wheel speed when grinding at the same material removal rate
for both the resin wheel and the experimental metal bonded
wheel. Power consumption during grinding, much of which goes
to the workpiece as heat, is less important in grinding
ceramic materials than in grinding metallic materials due to
the greater thermal stability of the ceramic materials.
As demonstrated by the surface quality of the ceramic samples
ground with the wheels of the invention, the power consumption
did not detract from the finished piece and was at an
acceptable level.
For the experimental metal bonded wheel G ratio was
essentially constant at 6051 for all material removal rates
and wheel speeds. For the resin wheel, the G-ratio decreased
with increasing material removal rates at any constant wheel
speed.
Table 2 shows the improvement in surface finishes and
waviness on the ground samples at higher wheel speed. In
addition, the samples ground by the new metal bonded wheel had
the lowest measured waviness under all wheel speeds and
material removal rates tested.
In these tests the metal bonded wheel demonstrated
superior wheel life compared to the control wheels. In
contrast to the commercial control wheels, there was no need
for truing and dressing the experimental wheels during the
extended grinding tests. The experimental wheel was
successfully operated at wheel speeds up to 90 m/s.
Example 3
In a subsequent grinding test of the experimental wheel
(#6) at 80 m/sec under the same operating conditions as those
used in the previous Example, a MRR of 380 cm3/min/cm was
achieved while generating a surface finish measurement (Ra) of
21


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
only 0.5 ~m (12 din) and utilizing an acceptable level of
power. The observed high material removal rate without
surface damage to the ceramic workpiece which was attained by
utilizing the tool of the invention has not been reported for
any ceramic material grinding operation with any commercial
abrasive wheel of any bond type.
Example 4
A cup shaped abrasive tool was prepared and tested in the
grinding of sapphire on a vertical spindle "blanchard type"
machine.
A cup shaped wheel (diameter = 250 mm) was made from
abrasive segments identical in composition to those used in
Example 1, wheel #6, except that (1) the diamond was 45
microns (U.S. Mesh 270/325) in grit size and was present in
the abrasive segments at 12.5 vol. % (50 concentration), and
(2) the segments sizes were 46.7 mm chord length (133.1 mm
radius), 4.76 mm wide and 5.84 mm deep. These segments were
bonded along the periphery of a side surface of a cup shaped
steel core having a central spindle bore. The surface of the
core had grooves placed along the periphery which formed
discrete, shallow pockets having the same width and length
dimensions as those of the segments. An epoxy cement
(Technodyne HT-18 cement obtained from Taoka, Japan) was added
to the pockets and the segments placed into the pockets and
the adhesive was permitted to cure. The finished wheel
resembled the wheel shown in Fig. 2.
The cup wheel was used successfully to grind the surface
of a work material consisting of a 100 mm diameter sapphire
solid cylinder yielding acceptable surface flatness under
favorable grinding conditions of G-ratio, MRR and power
consumption.
Example 5
Type 2A2 cup shaped abrasive tools (280 mm in diameter)
suitable for backgrinding AlTiC or silicon wafers were
prepared with the abrasive segments described in Table 3 _
below. Except as noted below, the segment sizes were 139.3 mm
radius length, 3.13 mm wide and 5.84 mm deep. Diamond
22


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WO 99/48646 PCT/U599/02399
abrasive containing bond batch mixes sufficient to manufacture
16 segments per wheel in the proportions given in Table 3 were
prepared by screening the weighed components through a U.S.
Mesh 140/170 screen, and mixing the components to uniformly
blend them. Powder needed for each segment was weighed,
introduced into a graphite mold, leveled and compacted. The
graphite segment molds were hot pressed at 405° C for 15
minutes at 3000 psi (2073 N/cm2). Upon cooling, segments were
removed from the mold.
Assembly of a wheel by adhering the segments onto a
machined 7075 T6 aluminum core was carried out as in Example
1. Segments were degreased, sandblasted, coated with adhesive
and placed in cavities machined to conform to the wheel
periphery. After curing the adhesive, the wheel was machined
to size, balanced and speed tested.
Table 3
Bond Composition
Weicrht % Volume
Sample Cu Sn P Graphite Cu Sn P Graphite
Control 49.47 50.01 0.52 0.00 43.71 59.03 2.26 0.00
(Ex. 1)
(1) 46.50 47.01 0.49 6.00 35.70 44.14 1.86 18.30
7.5/204
0
(2) 46.50 47.01 0.49 6.00 35.70 44.14 1.86 18.30
7.5/204
0
(3) 45.76 46.26 0.48 7.50 34.02 42.07 1.75 22.16
7.5/205
1
(4) 46.50 47.01 0.49 6.00 35.70 44.14 1.86 18.30
5/2040
(5) 43.53 44.01 0.46 12.00 29.55 36.54 1.53 32.37
25/2052
23


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WO 99/48646 PC'T/US99/02399
Table 4
Abrasive Sernnent Composition Vol%
Sample Bond Graphite Diamonds Porosityb


Control > 8 0 0 . 0 0 18 . 7 5 < 5


(Ex.l) (75 cons)


(1) >80 17.93 1.88 <5


7.5/2040 (7.5 COI1C)


(2) >80 17.93 1.88 <5


7.5/2040 (7.5 conc)


(3) >75 21.72 1.88 <5


7.5/2o5i (7.5 conc)


(4) >80 18.07 1.25 <5


5/2040 (5 conc)


(5) >63 30.35 6.25 <5


25/2052 (25 COriC)


a. All diamond grain used in the segments was 325 mesh ( 49
micrometers) grit size, except sample (1) which was 270 mesh
57 micrometers) grain. The diamond concentration levels are
given below the vol % diamond.
b. Porosity was estimated from observation of microstructure
of segments. Due to formation of intermetallic alloys,
density of test samples often exceeded theoretical density of
materials used in segments.
Example 6
Grinding Performance Evaluation:
Samples of 280 mm diameter, 29.3 mm thick, 228.6 mm
central bore, (11 in x 1.155 in x 9 in) low diamond
concentration, graphite filled, experimental segmental wheels
made according to Example 5 were tested for grinding
performance. The performance of these samples was compared to
that of the control backgrinding wheel of Example 5 which was
made according to the high (75 concentration) diamond abrasive
segment composition of Example 1 (wheel #6) without graphite
filler.
Over 70 grinds, each 114.3 mm (4.5 inch) wide and 1.42 mm
(0.056 inch) deep, were performed on AlTiC workpieces (210
Grade AlTiC obtained from 3M Corporation, Minneapolis, MN) of
either 4.5 in (114.3 mm) or 6.0 in (152.4mm) square
dimensions, and the microns of stock removed and the normal
grinding force were recorded. The grinding testing conditions_
were:
24


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
Grindina Test Conditions:
Machine: Strasbaugh Grinder Model 7AF
Grinding Mode: Vertical spindle plunge grinding
Wheel Specifications: 280 mm diameter, 29.3 mm thickness
and 229 mm hole.
Wheel Speed: 1,200 rpm
Work Speed: 19 rpm
Coolant: Deionized water
Material Removal Rate: Vary, 1.0 micron/sec to 5.0
micron/sec
Wheels were trued and dressed with a 6 inch (152.4 mm)
dress pad of specification 38A240-HVS dress pad obtained from
Norton Company, Worcester, MA. After the initial operation,
truing and dressing was conducted periodically as needed and
when down feed rates were changed.
Results of the grinding test (normal force versus stock
removed) for Example 5, samples 2, 4 and 1, are shown below in
Table 5, and in Figure 3.
Table 5
Normal Grindincr Force versus Stock Removed
Wheel Control Control Control 2a 2a 2b 4
S amp 1 a (Ex. 1 ) (Ex. 1 ) (Ex. l )
rtRR 1 3 5 1 2 2 2
(/sec)
Total Stock Normal Grindina Force lbs (Ka)
~.
Ground (u)
6(2.7) 8(3.6) 11(S.0) II(S.0)
SO 16(7.3) 20(9.1) 23(10.4) 6(2.7) 7(3.2) 19(8.6) 20(9.1)
75 12(S.4) 7(3.2) 23(10.4) 22(10.0)
100 24(10.9) 34(15.4) 40(18.2) 17(7.7) 7(3.2) 27(12.3) 28(12.7)
1S0 27(12.3) 4S(20.4) SO(22.7) 22(10.0) 7(3.2) 31(14.1) 32(14.5)
200 33(15.0) SO(22.7) S9(26.8) 28(12.7) 21(9.S) 34(15.4) 36(16.3)
250 37(16.8) 53(24.1) 60(27.2) 31(14.1) 30(13.6) 38(17.3) 38(17.3)
300 40(18.7) S7(25.9) 63(28.6) 33(15.0) 3S(15.9) 40(18.2) 36(16.3)
350 36(16.3) 39(17.7) 42(19.1) 38(17.3)
400 39(17.7) 41(18.6) 40(18.2) 33(15.0)
4S0 42(19.1) 42(19.1) 40(18.2) 34(15.4)
500 42(19.1) 4S(20.4) 41(18.6) 34(15.9)
SSO 43(19.5) 46(20.9) 43(19.5) 3S(15.9)
600 46(20.9) 46(20.9) 39(17.7) 31(14.1)
a. 2a is sample 2 from Table 3 with an abrasive segment rim
width of 3.13 mm.


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
b. 2b is sample 2 from Table 3 with an abrasive segment rim
width of 2.03 mm.
These results demonstrate that a significant increase in
normal force was needed to remove larger amounts of stock at
higher MRRs (going from 1 to 3 to 5 microns/second MRR) when
surface grinding with the control wheel sample having no
graphite filler and 75 concentration diamond abrasive. In
contrast, the low diamond concentration, graphite filled
wheels of Example 5 of the invention (samples 2a, 2b and 4)
needed significantly less normal force during grinding. The
force needed to remove an equivalent amount of stock at a MRR
of 2 micron/second for the inventive wheel was equivalent to
that needed at a MRR of 1 micron/second for the comparative
wheel sample.
In addition, wheel 2a samples needed approximately equal
normal forces to grind at either a MRR rate of 1 micron/second
or a MRR of 2 micron/second. The inventive wheels 2a, 2b and
4 of Example 5 also exhibited relative stable normal force
demands as the amount of stock ground progressed from 200 to
600 microns. This type of grinding performance is highly
desirable in backgrinding AlTiC wafers because these low
force, steady state conditions minimize thermal and mechanical
damage to the workpiece.
The control wheel (Ex. 1) could not be tested at higher
stock removal levels (e. g., above about 300 microns) because
the force needed to grind with these wheels exceeded the
normal force capacity of the grinding machine, thereby causing
the machine to automatically shut down and preventing
accumulation of data at the higher stock removal levels.
While not wishing to be bound by a particular theory, it
is believed that the superior grinding performance of the low
diamond concentration, graphite filled inventive wheels is
related to the smaller number of individual grains per unit of
area of the abrasive segment that come in contact with the
surface of the workpiece at any point in time during grinding.
Although one skilled in the art would expect a lower MRR at
lower diamond concentration, the grinding force improvement of_
the invention unexpectedly is accomplished without
compromising MRR. Wheel 2b, having an abrasive segment width
26
minutes at 3000 psi (2073 N/cm2). U


CA 02324578 2000-09-19
WO 99/48646 PCT/US99/02399
of 2.03 mm; needed less force to grind at the same rates and
amounts of stock removal than did wheel 2a, having an abrasive
segment width~of 3.13 mm. The wheel 2b sample has a smaller
surface area and fewer grinding points in contact with the
surface of the workpiece at any point in time during grinding
operations than does the wheel 2a sample.
27

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date 2004-11-02
(86) PCT Filing Date 1999-02-04
(87) PCT Publication Date 1999-09-30
(85) National Entry 2000-09-19
Examination Requested 2000-09-19
(45) Issued 2004-11-02
Deemed Expired 2009-02-04

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Request for Examination $400.00 2000-09-19
Registration of a document - section 124 $100.00 2000-09-19
Registration of a document - section 124 $100.00 2000-09-19
Application Fee $300.00 2000-09-19
Maintenance Fee - Application - New Act 2 2001-02-05 $100.00 2001-01-18
Maintenance Fee - Application - New Act 3 2002-02-04 $100.00 2002-01-23
Maintenance Fee - Application - New Act 4 2003-02-04 $100.00 2003-01-23
Maintenance Fee - Application - New Act 5 2004-02-04 $200.00 2004-01-28
Final Fee $300.00 2004-08-23
Maintenance Fee - Patent - New Act 6 2005-02-04 $200.00 2005-01-20
Maintenance Fee - Patent - New Act 7 2006-02-06 $200.00 2006-01-19
Maintenance Fee - Patent - New Act 8 2007-02-05 $200.00 2007-01-17
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
NORTON COMPANY
Past Owners on Record
BULJAN, SERGEJ-TOMISLAV
RAMANATH, SRINIVASAN
WILLISTON, WILLIAM H.
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Description 2004-01-12 27 1,336
Claims 2004-01-12 2 70
Abstract 2000-09-19 1 58
Claims 2000-09-19 2 71
Cover Page 2001-01-03 1 53
Drawings 2000-09-19 3 81
Representative Drawing 2001-01-03 1 19
Description 2000-09-19 27 1,347
Claims 2000-09-20 2 70
Cover Page 2004-10-05 1 51
Prosecution-Amendment 2004-01-12 5 159
Correspondence 2000-12-20 1 2
Assignment 2000-09-19 15 525
PCT 2000-09-19 9 278
Prosecution-Amendment 2000-09-19 1 19
Prosecution-Amendment 2000-09-19 3 89
Assignment 2001-08-30 13 458
Assignment 2001-11-01 1 29
Correspondence 2002-01-15 1 22
Prosecution-Amendment 2003-07-15 2 41
Correspondence 2004-08-23 1 32