Note: Descriptions are shown in the official language in which they were submitted.
W093/02837PCT/US92/05827
2112l179
Coated Abrasives Dressed By A
Multiple Point Cutting Tool
Technical Field
5The present invention relates generally to
continuous coated abrasive articles of the typ~ having
flexible backings with front and rear surfaces and
abrasive particles including abrasive graîns attached ~
along their front surfaces. ~`
Backaround of the Invention
The art is replete with abrasive articles
used to create new surfaces on objects. Examples of
such abrasîve articles are the endless abrasive belts
15 used în conjunction with the camshaft grinder disclosed
in U.S. Patent No. 4,833,834. Such endless abrasive
belts may be constructed using the abrasîve
agglomerates described în Bloecher et al. U.S. Patent
nu~ber 4,799,939 which may contain abrasîve graîns made -~
20 for~example according to the teachings in Schwabel U.S.
Patent Number 4,744,802. U.S. Patent 4,215,516 to
Huschle et al. discloses a splicing system for butt
splicing flexible abrasive belts to form a~ endless
abrasive belt.
Abrasive agglomerates may include a plurality
of ~brasive grains bonded together by a phenolic resin
(e.g. a phenolic based make and size coat) or any other
suitable binder to form a shaped mass, and the abrasive ~`
grains may be constructed from cerami aluminum oxide, -`
30 commercially available from the Minnesota Mining and
Manufacturing Company (3M) of St. Paul, ~innesota under
the tradejdesignation grade 120 "Cubitron" ceramic
aluminum oxide abrasive grains, and may have a particle
fiize of approximately 116 micrometers. As used in this
35 application, the phrase "abrasive agglomerate" is
defined as a plurality of abrasive grains bonded
together by a binder.
Figures 1 and 2 illustrate a coated abrasive
belt 10 (e.g., the abrasive belt sold by Minnesota
W093/0~837 ~g PCT/~S92/~5827
Mining and Manufacturing, St. Paul Minnesota, under the
trade designation 3M "Multicut" T.M. Resin Bond cloth
coated abrasive belts) after it is constructed but
before it is used to abrade a workpiece. Such an
5 abrasive belt may be used, for example, in conjunction
with the camshaft grinder disclosed in U.S. Patent No.
4,833,834 to grind pieces of metal stock having
generally cylindrical portions into camshafts.
The coated abrasive belt 10 includes a
10 flexible backing 11 (e.g. cloth or polymeric film, ~
vulcanized fiber, paper, combinations thereof and ~`
treated versions thereof) with front and rear or "back"
surfaces, and a mound or mountain-shaped abrasive `
coating 12 which includes abrasive agglomerates
15 attached along the front surface of the backing ll.
The mountain-shaped surface of the abrasive belt ~-
includes numerous peaks and valleys. The "height" of a
peak is defined in this specification as the shortest
distance between the back surface of the backing and
20 the top of the peak along the surface of the abrasive
belt.
These and other existing abrasive belts
encounter problems during "start up" or during their
initial use. Initially, before the belt is used to
25 grind a workpiece/ the heights of the mountains along
the mountain-shaped surface of the abrasive belt vary
widely, as much as forty (40~ percent. The uneven
thickness of the belt may be due to a variety of
factors such as, but not limited to coating variations,
30 backing variations, or splices. The tallest peaks tend
to cause undesirable results such as "wild scratches"
OF a coarse surface finish on the workpieces (e.g.
camshafts) which are ground during thP initial uses of
the abrasive belt. It is believed that pressure is
35 initially concentrated at the tallest peaks until they
break or shear from the remaining abrasive agglomerate
attached to the abrasive belt. The breakage or
shearing of the tallest peaks of the abrasive
agglomerate ultimately leads to a more uniform belt -~
W093/02837 2 1 1 2 ~ 7 g PCT/US92/05827
- 3 - I
thickness or caliper, but only after the end user risks
leaving deep or "wild" scratches or risks creating an
undesirably coarse finish on the workpiece.
The endless abrasive belts used with the
5 camshaft grinder disclosed in U.S. Patent 4,~33,834
should produce a consistent finish on the surface of
camshafts. A coated abrasive belt such as the belt
shown in Figures 1 and 2 may not leave the desirable -
finish on the workpiece until the mountain shaped
10 abrasive is sufficiently worn. Another problem
associated with the initial uses of the prior art
endless abrasive belts on a camshaft grinder such as
the camshaft grinder shown in U.S. Patent 4,833,834 is
that the caliper or "thicknessl' of the belt initially
15 changes rapidly as the mountain-shaped portions are
broken and worn away. The camshaft grinder is required ~-
to continually adjust for this rapid change of belt ~`
caliper until the wear characteristics of the belt
stabilizes~
Additionaily, existing abrasive belts
encounter problem$ even after their "start up" or
initial use. For example, when an abrasive belt is
used to abrade a metal workpiece (e.g. a camshaft) the
metal pieces which are abraded from the workpiece tend
25 to become welded over the surface of the abrasive.
This prematurely ends the useful life of a belt.
Some existing endless coated abrasive belts
encounter pro~lems due to th ir lack of uniform
thickness. Rnown butt splices are used to con5truct
30 some endless abrasive belts. In a butt splice, two `
edges of the backing of an abrasive sheet are abutted,
and thereafter joined together with a reinforcing strip
which i# bonded to the underside of the abrasive belt.
Coated abrasive belts which incorporate butt
35 splices may have a thickness which is greater at the
splice than elsewhere along the belt. The height of
the peaks of the agglomerate at the splice area will ~`
generally tend to be greater than the heights of the
peaks along the remainder of the endless belt due to
.~
.
Minnesota Mining 8~ :
Manufacturing Company
.~; . M- 7061 . ~ c~ ~ rt~ PCr/US32/05827
~ r~
':
the presence of the reinEorcing strip. Thls additional
thickness or "height" in the splice area tends to leave
"splice marks" or undes~rab~y deep "wild" scratches 1
the abraded workpiece.
Another known method of constructing an
endless belt is ~nown as a "lap splice" whereln two
ends of an abrasive belt sheet are overlapped to ~orm
an endless abrasive belt. The thicknes-~ of the belt ~t
the ~oint may be greater than the thickne~s o~ the belt
10 elsewhere due to the overlapped ends. Again, the
dlfference in thickness or caliper of the bel~ at the
lap splice tends to result in undesirable consequences
such as marks or deeper "wild" scratches in the abraded ~
workpiece. -
lS A known treatment of an abraslve product i8
dlsclosed in U.S. Patent No. 1,944,898 to McKee. McKee
discloses prov~ding a pair of rolls constructed from a
materl~l that i8 tougher than the abrasive material o~
the coated abrasive product (Figure 3). The mineral
20 particles of the abrasive article are "bro~en" down by -~
the touqher rolls. ~ -
Known methods for dressing a grinding wheel
are described by Kenneth B. Lewis and William F.
Schleicher in Chapter 14, pages ~49 to 164 o~ "The
25 Grinding Wheel" ~ Textbook o Modern Grinding Practice,
- The Grlnding Wheel Xnstitute, Cleveland, Ohio (1976).
5rinding wheels are generally dressed to sharpen the
wheel by exposing abrasive grains and are sometimes
dressed to `'true" the wheel.
~,
SU~ST~ T~: StlEET
21~2479 - `
Minnesota Mining &
Manufacturing Company
M 7061 - 4A - PCT/US92/05827
Other prior arts of interest are the following three
documents that were considered during the natent application
stage of the present invention.
:
Soviet Patent Abstracts Section PQ, Week 9027 15.08.1990,
Derwent Publications Ltd., London, GB; Class P, AN
90-208040/27 & SU-A-1 511 098. This prior art is concerned
with a method of dressing abrasive cloth. The method
comprises passing the cloth through a calibrating slit. The
calibrating slit is formed by a suPport and a clamping
element in the form of an abrasive drum. The hardness of
the abrasive drum grains has to be equal to, or more than,
the hardness of the abrasive cloth grains. The grains size
of the abrasive drum has to be less or equal to the size of
the abrasive cloth grains. As the grains of the cloth pass
through the slit they engage with the grains of the drum and
the apexes of the cloth grains are broken off.
Patent Abstracts of Japan, vol. 13, no. 163 (M-816) ~35111,
19.04.1989~ & JP-A-64-002 865.
This prior art discloses a method for dressing a polishing
belt wherein an endless abrasive polishing belt driven b~ a
roll is dressed b~ rubbing the belt with an abrasive cloth
whereby the ends of the abrasive grains on the polishing
belt are broken and fine grains of a desired mesh are said
to be produced on the polishing belt.
SUE~STITUTE SH~ET
2112479
Minnesota Mining &
Manufacturing Company
M 7061 ~ 4B - PCT~US92/05827
Soviet Patent Abstracts Section PQ, Week 9029, 29.08.1990,
Derwent Publications Ltd; London, GB; Class P, AN 90-223
266/ 29 & SU-A-1 516 325. This prior art discloses a
method of dressing a grinding belt by feeding the belt via a
contact roller positioned above a dressing disc~ The
contact line defined between the belt and the disc is offset
from the center of the disc. To provide a uniform wearing
out of the dressing disc a relative reciDrocal to-and-fro
motion across the disc is created between said contact
roller and said disc. The effect on the belt is described
with reference to a Fig. 4 of this prior art document which
sho~s that an initial profile with high peaks is reduced to
a profile in which the peaks no longer exist and the
remaining stumps that result from the removal of said peaks
have a rough top face.
Disclosure of the Invention
.
The present invention is as defined in the accompanying
claims.
The invention provides a coated abrasive comprising a
flexible backing with front and rear or "back" surfaces, a
generally uniform width, and mounds of abrasive particles
including abrasive grains attached along the front surface.
Initially, the mounds of abrasive particles project
different distances in a predetermined range from the front
surface of the bac~ing. A multiple point cutting means
Fr
W093/0~37 2 1 1 2 4 ~ ~3 PCT/US92/0~27
_ 5 ~
having a width at least substantially equal to the ;~
width of the backing and having a cutting surface
constructed from a material harder than the abrasive
grains i8 used to cut the mounds of the abrasive
S particles to form generally coplanar surfaces generally
parallel to the back surface. ~-
In a preferred embodiment of the coated -
abrasive, the mounds have heights measured from the -~
back surface of the Slexible backing, and the coplanar `.
10 surfaces have heights measured from the back surface of
the flexible backing such that the heights of the
mounds before cutting and the height of the coplanar
surfaces~after cutting are described by the equation: `
15; P1 ~ X (P2); ;~
wherein~
X is between 1.1 and 2; and ~ ~`
Pl~-~the~height of~the tallest mound of the
20~ a~ra&ive~ particles~before cutting, and -~
P2- = the height of the tallest co-planar
`surf~ce of the abrasive~particles after cutting by the
cùtting means. In one embodiment, X i8 equal to 1.35. "~
The present invention may be characterized as
25~ a~method of quickly and conveniently "dressing" a
coated~abrasive article that may be used in conjunction
with automatic dressing mechanisms, which provides a
more consistent uniform finish, which significantly
reduces the tendency of the resultant coated abrasive `
30 article to create wild scratches or an otherwise
deficient finish on a workpiece during the initial use
of the ~brasive` article, and which provides a coated
abrasive with more predictable wear characteristics and `
a more uniform caliper or thickness.
The coated abrasive of the present invention
may be prepared by the process comprising the steps of: ~
; (1) provlding~a~fleYible bàcking with front and rear ;`
surfaces~and~having~a generàlly uniform width, and
attàchlng~discrete mounds of~abrasive particles
~, :
WO g3/02837 ~ PCr/USg2/05827
including abrasive grains along the front surface, the
mounds of abrasive particles projecting different
distances in a predetermined range measured fro~ the
rear or back surface of the backing, (2) providing a
S multiple point cutting means having a width at least
substantially equal to the width of the backing and
having cutting surfaces constructed from a material
h_rder than the abrasive grains, and then (3) cutting
the mounds of the abrasive particles projecting more
10 than a predetermined distance within the range with the
cutting means to form generally coplanar surfaces
generally parallel to the back surface. The cutting
means may have surfaces constructed from diamonds,
boron~nitride or any other suitable cutting material so
15 long as the material is harder than the abrasive
grains.
AdditionaIly, the present invention may be
descr~ibed as~a m~thod of grinding workpieces using
~ endless coated~abrasive belts each comprising a
;~ 20~ flexible~backing with front and rear surfaces and
mounds of abrasive particles including abrasive grains
attached along the front surface. The endless coated
abrasive belts may be mounted on a means for driving
the endless abrasive belt, such as the camshaft grinder
25 described in U~S. Patent No. 4,833,~34. A multiple
; point cutting means having cutting surfaces harder than
the abrasive grains is provided.
Next, the abrasive belts are driven past a
grinding station and the belts are used to grind
30 several workpieces until the abrasive belt becomes
dull, and then the endless abrasive belt is dressed
while remaining mounted on the means for driving the
endless abrasive belt by cutting the abrasive particles
with the cutting means to remove debris and to
35 resharpen the belt. Additionally, each of the coated
abrasive belts may be simultaneously dressed while they
-~ are mounted on the camshaft grinder described in U.S.
Patent No. 4,833,834 and before they are used to grind
a~workpiece.
W093/02837 2 1 1 2 4 7 9 PCT/US92/OS827 :~
7 ~
Brief Description of the Drawing i~
The present invention will be further :
described with reference to the accompanying drawing ~-
wherein like reference numerals refer to like parts in .
5 the several views, and wherein:
Figure 1 is a cross~sectional phatographic
view of a prior art coated abrasive before it is used :
to abrade a workpiece; :--
Figure 2 is a photograph at a magnification
10 of twenty-five (25) of another portion of the coated i;
abrasive of Figure l; `.
~igure 3 is a cross-sectional photographic ~-
view of coated abrasive after it has been dressed by
the~method according to the present invention;
Figure 4 is a photograph at a magnification
of twenty-five (25) of another portion of the abrasive ~`~
of Figure 3; -~
Figure S is a cross-sectional photographic
view o~f a:coated abrasive belt after it has been used
~20 to grind 19 camshafts on a camshaft grinder; ~:~
Figure 6 is a photograph at a magnification ~`
of forty (40) of another portion of the coated a~rasive
: belt shown in Figure 5;
Figure 7 is a schematic illustration of a
25 f irct embodiment of the method of making or "dressing" -
a coated abrasiv~ according to the present invention;
Figure 8 is a perspective view of one
embodiment of cutting means according to the present
invention;
Figure 9 is a top view of a means for
simultaneously driving a plurality of belts past a
dressing/grinding station and the cutting means of
Figure 8, which ilIustrates a technique for
simultaneouæly dressing a plurality of abrasive belts;
Figure 10 is a schematic illustration of a
second embodiment of the method of making or "dressing"
a coated abrasive according to the present invention;
, ~
, ~ :,``.'
,:
.
W 0 93/02837 ~ ~ P~r/US92/05827
Figure 11 is a schematic illustration of a
third embodiment of the method of making or "dressing"
a coated abrasive according to the present invention;
Figure 12 is a cross-sectional photographic
5 view of a coated abrasive such as the coated abrasive
of Figure 5 after it has been dressed subsequent to the
grinding of (19) camshafts; and
Figure 13 is a photograph at a magnification
of forty (40) of another portion of the coated abrasive
10 belt of Figure 12.
Detailed Description
Referrinq now to Figures 3 and 4 of the
drawing, there is shown a coated abrasive according to
15 the present invention generally designated by the `~
reference number 20. The coated abrasive 20 comprises
a flexible backing 21 with front and rear surfaces, and
mounds of abrasive agglomerates 22 including abrasive
grain# 23 (e.g. ceramic aluminum oxide, commercially
~; 20 available from the Minnesota Mining and Manufacturing ~-
Company (3M) of St. Paul, Minnesota under the trade
designation grade 120 "Cubitron" ceramic aluminum oxide
abrasive grains with a particle size of approximately
116 micrometers) attached along the front surface (e.g.
2~ by phenolic based make and size coats). The mounds of
abrasive agglomerates 22 initially project different
distances in a predetermined range measured from the
rear or back surface of the backing 21.
To begin constructing the coated abrasive 20,
30 the csated abrasive 10 shown in Figures 1 and 2 (e.g.,
the abrasive belt sold by Minnesota Mining and
Manufacturing, St. Paul Minnesota, under the trade
designation 3M "Multicut" T.M Resin Bond Cloth coated
abrasive belts) may be selected. The coated abrasive
35 10 may be constructed using the abrasive agglomerates
described in Bloecher et al~ ~.S. ~atent number
4,799,939 which may contain abrasive grains made for
example according to the teachings in Schwabel U.S.
Patent Number 4,744,802.
W093/02837 PCT/US92/05X27
21~2~ 79
g ..
Referring now to Figures 7 and 9 there is
shown a schematic illustration of a first embodiment of
the method of making or "dressing" a coated abrasive
according to the present invention generally designated
5 by the reference number 40. The coated abrasives shown
in Figure 7 are endless coated abrasive belts 41 which
may be formed by utilizing a lap or butt splice. As
mentioned above, endless belts having lap or butt
splices may be thicker in some portions than others and
10 may tend to leave undesirable marks or wild scratches
in the workpiece.
Figures 7 and 9 illustrate the prior art
coated abrasives shown in Figures 1 and 2 after they
are formed into the endless belts 41 and after they are
15 mounted on a means for driving the endless abrasive
belt 41, such as the camshaft grinder described in U.S.
Patent No. 4,833,834 schematically illustrated as
reference character 42.
Figure 8 illustrates a multiple point cutting `
20 means which is preferably constructed from a generally
cylindrical piece of metal stock 50 which is similar to
the pieces of metal stock which are ultimately ground
into the asymmetrical cross-sections of the camshafts.
The use of a multiple point cutting means
25 substantially r~duces the time required to dress a
coated abrasive when compared with the time required to
dress a coated abrasive with a single point cutting
tool. ~`
The cutting means is used to cut material `"
30 from the mountain-shaped surfaces (Figure 1) to form
coplanar surfaces 25. The metal ætock 50 has cutting
~urfaces 53 harder than the abrasive grains 23 attached
thereto on surfaces which are generally spaced the same
as the spacings of the lobes on the camshafts.
35 Alternatively the cutting means may be continuously
coated with cutting surfaces 53.
The cutting surfaces 53 may be attached to
the periphery of the metal stock by any known method,
such as but not limited to flame spraying or plating.
W093/02837 ~ PCI`/US92/05827
For example, the cutting means may comprise a piece of
metal stock S0 having generally cylindrical periphery ^~
portions and a metal binder coated (e.g. electroplated
or brazed) to selected portions of its generally
S cylindrical periphery and with cutting surfaces 53
(e.g. diamonds or cubic boron nitride) applied to the
metal binder. Another method of making a suitable ~
cutting means comprises the steps of providing a ;
generally cylindrical piece of metal stock and
lO adhesively applying a strip of "DIAPAD" T.M. abrasive
(commercially available from Minnesota Mining and
Manufacturing, 3M, St. Paul, Minnesota) to the
periphery of the metal stock with, for example pressure
and a hot~melt adhesive.
~ Additionally, the cutting means may be
constructed by laminating (e.g. adhesively) or plating
a coated abrasîve containing the cutting surfaces 33 "~
birder~than the~abrasi~ve grain to the cylindrical piece ~-
of~ et~l~stock~30. Also, U.S. Patent Gorsuch 4,256,467
20~discloses;another method of making a cutting means for
use in~the method of the present invention by ~-~
electroplating a metal binder;and abrasive grains to a
~mesh~material.
, ~ .
- ~ In a preferred embodiment of the coated
25 abrasive 20, the mounds or mountain-shaped portions `
have heights measured from the back surface of the ~
flexible ~acking 21, and the coplanar surfaces 25 have
heights also measured from the back surface of the
flexible backing such that the heights of the mounds
30 before cuttinq (e.g. 12 of Figure 1) and the height of
the coplanar surfaces after cutting are described by
the equation:
,, ,
P1 ~ X tP2);
wherein:
Pl - the height of the tallest mound or
mountain-shaped portion of the abrasive particles
~before cutting, and ;
.-:
l~linn~s~ta i~in ~-lg &
Manufacturing Company
M 7061 2112 ~ 79 PC~/U~2/05~7 ~-
P2 = the height of the tallest co-pl~nar
surfacQ of the abrasive partlcles after cuttlng by the
cutting m~ans.
When "Multicut" T.M. Resin Bond cloth coatQd
5 abrasive belt~ are used as th~ abra~lve, X ~
preferably within the range of between 1.1 and 2, since
if X becomes less than 1.1 then the resultant abra~ive
i5 underdressed and the attendant problem~ of
scratching and rapid belt cal~par change are
10 encountered, and if X becomes greater than 2, then the
belts tend to be overdressed which prematurely ~nds the
useful llfe of thè belt.
For example, ~he~"Multicut" T.M. coated ~v
abraslve may initially have a height of the tallest
15 mound of.the abrasive agglomerate 12 of approximately 1
(0.066 inche~. Such coated abrasives are useful for a
variety of grinding operation~ and may be used, ror
example, as an endless coated abrasive belt used to
grind camshaft~ using a camshaft grinder such as the
20 camshaft grinder described ~n U.S. Patent No.
4,833,834. When using such coated abra~ives to grind `~
camshafts, ~t has been determined that dressing or
cutting the height of the tallest co-planar surface 25
of the abras~ve particles 22 to abo~t~70.049 inches)
25 provides an abrasive belt with a more unlform caliper
or thickness, and which significantly reduces the
tendency of the resultant coated abrasive article to
create wild scratching, damaging or an otherwise
def~cient ~inlsh on a workpiece durlng the initial use
30 o~ the abrasive article particularly when using an
endles~ belt which may have a raised abrasi~Q portion
prox1mate its seam. In this example X i8 equal to
1.3S.
Dressing of an abrasive belt also provides a
35 coated abrasive with more predictable wear
characteristics in that the useful life of a dressed
belt 1s more readily predicted than a belt that i8 not
drQssed. It i~ believed that the pressures at the
abrad~ng interface of a dressed belt are more evenly
SUBSTITUTE SHEET
W093/02837 2 ~ PCT/US92/05827
. - 12 -
distributed over the abrasive surface once the
mountain-shaped portions are cut into the plateau
shapes.
The width of the periphery of a portion of
5 the metal stock 50 having the individual cutting
surfaces 53 attached thereto is approximately the width
of a single belt. The total area of the periphery of
the metal stock 50 which has cutting surfaces 53
attached thereto is substantially egual to or greater
10 than the total of the widths of each of the endless
abrasive belts 41. Such a cutting means affords the
user the opportunity to dress multiple belts at the
same time which substantially reduces the time required
to dress the plurality of abrasive belts 41 when
15 compared with the time required to individually dress
individual belts. Optionally a plurality of single-
point diamond dressing tools may be used as the cutting
means.
To cut the mountain shapes shown in Figure 1
20 into the shapes shown in Figure 3, the cylindrical
piece of metal stock 50 may be rotated clockwise
(alternatively the stock 50 may remain stationary)
relative to the frame 45 of the grinding means 42
(Figure ~) by any suitable drive means as the belts 41
25 are driven by the grinding means 42, and then moved
toward the abrasive belts 41 in a direction generaliy
perpendicular to the axis of the cylindrical piece ~f
stock 50 into contact with the abrasive until the
desired amount of ~aterial is removed from the
30 abrasive.
When the abrasive belts 41 become dull or
loverly contaminated with grinding debris (e.g. after
they are used to grind several camshafts), the endless
abrasive belts 41 may also be redressed while remaining
35 mounted on the means 42 for driving the endless
abrasive belt by simply cutting the abrasive
agglomerate with the cutting means 50, 53.
Figures 5 and 6 illustrate a coated abrasive
after it is used to grind nineteen (19) camshafts on a ~`
-~
W093/02837 2 1 1 2 4 7 ~ PCT~US92/05827
- 13 -
camshaft grinder. At this point, the "Multicut"
abrasives tend to begin to become dull. Also, metal
particles tend to become welded over the front surface
of the abrasive.
Figures 12 and 13 illustrate the coated
abrasive of Figures 5 and 6 after it has been redressed
to resharpen and to clean the abrasive. Redressing or
cutting the abrasive belts with the cutting means after ;
the belts are used to a~brade several workpieces is
10 believed to "clean" the abrasive belt by, for example,
removing the metal particles which tend to weld
themselves to the surface of the abrasive during
grinding. Also, redressing the belts at this time
provides a belt with a more uniform thickness and thus `
15 restricts the likelihood of wild scratches. Also,
particularly when the abrasive comprises an abrasive
belt with an agglomerate that includes abrasive grains,
redressing the abrasive at this time is believed to
expo e additional grains to thereby sharpen and extend
20 the life of the abrasive belts.
While the present invention has been
described in conjunction with a camshaft grinder 42, it
should be noted that the present invention may be
practiced with any suitable grinding assembly which
2S utilizes a coated abrasive. For example, th~ formed
wheel grinding assembly, conveyorized grinding
assembly, centerless grinding assembly, surface
grind ing assembly, flexible bed shaet grinding
asse~bly, rotary table surface grinding assembly, and
30 swing grinding assembly described on pages 19-21 of
Metalworking, Reference Manual, published by the
Industrial Abrasives Division of Minnesota Mining and
Manufacturing, ISBN #60-4400-0366-7 ~1294)JR may
utilize the abrasive belts and the dressing methods of
35 the present invention. Also, the backstands, polishing
jacks or vertical slack belt machines sold by KLX
Industries, Crystal, Minnesota, or G & P Industries,
Indianapolis, Indiana may also utilize the abrasive
belts and dressing methods of the presen~ invention.
W093/02837 PCT/US92/0~27
~?, ~ 14 -
Moreover, it is possible to dress an abrasive
before it is mounted on the machine used to grind a
workpiece. Figure 10 illustrates a second method of
dressing coated abrasives according to the present
5 invention, generally designatèd by the reference
character 18. A multiple point cutting means having a
cutting surface 33 constructed from a material harder
than the abrasive grains 23 is again used to cut the
mounds of the abrasive particles 22 from the front
10 surface to form generally coplanar surfaces 25 (Figures
3 and 4) generally parallel to the front surface.
While Figures 7 and 9 illustrate coated
abrasive belts dressed on a grinding machine, Figure 10
illustrates an example of a method of dressing coated
15 abrasives at a location remote from the location of
their ultimate use. For example, the coated abrasives
20 may be dressed before they are shipped to the end
; user. ~;~
The coated abrasive 20 of the present
20 invention may be prepared by the process comprising the
steps of: (1) providing a flexible backing 21 with
front and rear surfaces, and attaching discrete mounds
of abrasive particles which includes abrasive grains 23
; along the front surface, the mounds of abrasive
25 particles projecting different distances in a
predetermined range measured from the back surface of
the backing tsee Figure 1), t2) providin~ multiple
point cutting means (e.g. 30) having cutting surfaces
33 constructed from a material harder than the abrasive
30 grains 23, and then (3) cutting the mounds of the
abrasive particles 12 projecting more than a
predetermined distance within the range with the
cutting means to form generally coplanar surfaces 25
generally parallel to the back surface.
Tbe cuttinq means has cutting surfaces 33
; constructed from "super abrasives" such as diamonds,
cubic boron nitride, metal carbides, metal nitrides or
any other suitable cutting material as long as the
material is harder than the abrasive grains 23. In
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W093/02837 ~ 7 9 PCT/US92/OS827
: :
- 15 -
Figure 10, the entire periphery of the cutting means
includes cutting surfaces 33, unlike the metal stock 50
which only has selected portions coated with the
cutting surfaces.
The width of the metal stock 30 ~hould be at
least substantially equal to the width of the coated
abrasive 20 to afford efficient, effective dressing of :
the entire width of the abrasive 20. The method of
making a coated abrasive 20 shown in Figure 10 is
lO particularly suitable for dressing large sheets or
rolls of an abrasive belt prior to shipment to the
ultimate user.
In the embodiment shown in Figure 10, the :
dressing tool or multiple point cutting means comprises
15 a cylindrical piece of metal stock 30. The stock 30
may be rotated clockwise as the coated abrasive 20 is
moved relative to the metal stoc~ 30 from left to right
in the figure. Back-up means (not shown) are provided
to support the coated abrasive 20. The cutting means
20 may be located proximate the coated abrasive then moved :
in a direction perpendicular to the axis of the
oylindrical stock 30 toward the co3ted abraæive 20 into
contact with the abrasive until the desired amount of
~aterial is cut from the coated abrasive 20. The
25 back-up means may comprise a hard flat surface or may
comprise a hard cylindrical member adapted fsr
clockwise rotation. Optionally, the cutting means may
remain stationery or it ~ay be oscillated.
Referring now to Figure 11 there is shown a
30 schematic illustration of a third embodiment of the
method of making or dr~ssing a coated abrasi~e
according to the present invention generally designated
by reference character 70.
The method illustrated in Figure ll is
3S particularly suitable for dressing a wound abrasive
from any suitable, known workpiece feed mechanism. The
workpiece feed mechanism may somprise an unwind wheel
or drum 87 having a sheet of coated abrasives 71 wound
z ~ PCTtUS92/05827
- 16 -
and journaled thereon, a back-up wheel 72, and a
take-up wheel 73.
A multiple point cutting means 82 te.g. a
generally cylindrical piece of metal stock) having
5 cutting surfaces 53 harder than the abrasive grains 23
i8 provided. Like the cutting means shown in Figure
10, the cutting means shown in Figure il may comprise a
generally cylindrical piece of metal stock 82 having a
periphery and a metal binder coated (e.g. electroplated
10 or brazed) to its periphery and with cutting surfaces
83 (e.g. diamonds or boron nitride) applied to the
metal binder. Alternatively the cutting means may be
constructed by laminating (e.g. adhesively) a coated
abrasive containing the cutting sur~aces 83 harder than ~.
15 the abrasive grains to the cylindrical piece of metal
tock 50.
The width of the metal stock 82 (not shown)
should be at least substantially the same as the width
of the coated abrasive roll 71. When a cutting means
20 having a width substantially equal to the total of the
widths of the ~oated abrasive 71 is used, a large stock
roll of coated abrasives ~ay be quickly, conveniently
and efficiently d~essed in a relatively short period of
time.
In the embodiment shown in Figure 11, the
cylindrical piece of metal stock 82 may be rotated
counterclockwise as the coated abrasive 71 is moved
relative to the metal stock 82 by the take-up wheel 73
in the direct.ion 5hown by the arrows in the figure.
30 For example, the cutting means 82, 83 is moved in
toward the back up wheel 72 into contact with the
abrasive to efficiently cut the mounds of abrasive
particles 22 until the desired amount of material is
cut from the coated abrasive. Optionally, the cutting
35 means may be oscillated while in contact with the
a~rasive.
The present invention has now been described
with reference to several embodiments thereof. It will
be apparent to those skilled in the art that many
Minnea~ta ,~ining & .
Manufacturing Company 91 ~ ~ ~ 7n
M 706~ ~ p~ 9~/058?7
- 17
- changes can be made in the embodiment described w~thout ;
departing from the scope of the present invention. For
example, while the method o dressing a coated abrasiYe
of the present invention has been described using the
S abrasive belt sold by Minnesota Mining and
Manufacturing, St. Paul, Minnesota, under the trade
designation 3M "Multicut" T.M. Resin Bond Cloth Coated
Abrasive Belts as exemplary, the method of the presQnt
inventlon may be described with respect to ~ny suitable
10 abrasive such as, but not }imited to the abrasive -
belts sold by Minnesota Mining and Manufacturing~ St.
Paul, Minnesota, under the trade designation 3M "Regal" ;~
T~.M. Resin Bond Cloth Belts, or the abrasive belt also
sold by~Minnesota~Mining and Manufacturing Company, St.
- 15 Paul, Minnesota, under~the trade designation 3M ~31D
"Three-M-lte" T.M. Resin Bond Cloth Belts, or other
ahraQ~i~ve-be~lts that are not agglomerates. Also, the
me;hod~of the present invention is particularly
suitable~for~use with automatic dressing mechanisms ;~
20~which~control the interference between the dressing
tool/cuttlnq means and the coated abra~lve.
Additlonally, while the cutting means ha~ been
descr~lbed as a cylindrical piece of metal 6toak, the
cuttlng means may comprise any suitable shape, such as,
25 but not limited to flat, arcuate, trianqular, hexa~o~al
or combinations thereof, as lonq as the cutting means
;~ 1ncludes cutting surfaces h~rder than the abrasive
gralns 23. For example, the cutting mean~ may compri6e
Diamond Impregnated Dresser Style No. 5S6, available
~0 from Carter Diamond Tool of Willoughby, Ohio that i~
intended for use with bonded wheels.
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STITUTE SHEET
