Note: Descriptions are shown in the official language in which they were submitted.
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MET~:OD AND APPARATUS FOR KNURLING A WORKPIECE, METHOD
OF MOLDING AN ARTICLE WIT~ SUC~ WORKPIECE, AND SUC~
MOLDED ARTICLE
TECHNICAL FIELD
The present invention relates to a method and appal ~lus for knurling a
workpiece, a production tool molded with the knurled workpiece, and a method andapparatus for making an abrasive article with the production tool.
BACKGRQIJN~ QF THE ~VENTIQN
The present invention is useful for making an abrasive article in which a
structured abrasive coating is provided on a substrate. The abrasive coating comprises
abrasive particles and a binder in the form of a precise, three dimensional abrasive
15 composites molded onto the substrate.
A structured abrasive is a form of an abrasive article in which a substrate bears
on a major surface thereof abrasive composites comprising a plurality of abrasive
grains dispersed in a binder. The binder serves as a medium for dispersing the abrasive
20 grains, and it may also bind the abrasive composites to the substrate. The abrasive
composites have a predetermined three-dimensional shape, e.g., pyramidal. In oneforrn, the dimensions of a given composite shape can be made substantially uniform
and the composites can be disposed in a predetermined arra~. The predetermined arra~
can be in linear form or matrix form.
Such a structured abrasive article can be prepared by a method generally as
follows. A slurry cont~ining a mixture of a binder precursor and a plurality of abrasive
grains is applied onto a production tool having cavities which are the negative of the
final shape of the abrasive composites. A substrate is brought into contact with the
30 exposed surface of the production tool such that the slurry wets the first major surface
of the substrate to form an intermediate article. Then, the binder is at least partially
solidified, cured, or gelled before the intermediate article departs from the exposed
surface of the production tool to form a structured abrasive article. The abrasive
article is then removed from the production tool and fully cured if it was not fully
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cured in the previous step. Alternatively, the slurry can be applied onto the first major
surface of the substrate and then the production tool can be brought into contact with
the first major surface of the substrate. The precise nature of the abrasive composites
provides an abrasive article that has a high level of consistency. This consistency
s further results in excellent performance.
Structured abrasives, and methods and apparatuses for making such structured
abrasives, are described in U.S. Patent No. 5,152,917, "Structured Abrasive Article,"
(Pieper et al.), issued October 6, 1992, the entire disclosure of which is incorporated
10 herein by reference. In one embodiment, Pieper et al. teaches an abrasive article
comprising precisely shaped abrasive composites bonded to a backing in which thecomposites comprise abrasive particles and a binder. Pieper et al. te~ches, among
other things, a method of making the structured abrasive article generally in
accordance with the method described briefly above. Pieper et al. teaches that the
production tool can be a belt, a sheet, a coating roll, a sleeve mounted on a coating
roll, or a die, and that the pl efel l ~d production tool is a coating roll. Pieper et al.
teaches that, in some instances, a plastic production tool can be replicated from an
original tool by embossing a therrnoplastic resin onto a metal tool, for example. Such
a metal tool can be fabricated by diamond turning, engraving, hobbing, assembling as a
20 bundle a plurality of metal parts machined in the desired configuration, or other
mechanical means, or by electroforming.
Other examples of structured abrasives and methods and apparatuses for their
m~nllf~ctllre are disclosed in U.S. Patent No. 5,435,816, "Method of Making an
25 Abrasive Article," (Spurgeon et al.), issued July 25, 1995, the entire disclosure of
which is incorporated herein by reference. In one embodiment, Spurgeon et al. teaches
a method of making an abrasive article comprising precisely spaced and oriented
abrasive composites bonded to a backing sheet generally in accordance with the
method described briefly above. Spurgeon et al. teaches that, in addition to other
30 procedures, a thermoplastic production tool can be made according to the following
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procedure. A master tool is first provided. The master tool is preferably made from
metal, e.g., nickel. The master tool can be fabricated by any conventional technique,
such as engraving, hobbing, knurling, electroforming, diamond turning, laser
m~chinin~ etc. The master tool should have the inverse of the pattern for the
s production tool on the surface thereof. The thermoplastic material can be embossed
with the master tool to form the pattern. Embossing can be concl~lcted while thethermoplastic material is in a flowable state. After being embossed, the thermoplastic
material can be cooled. Spurgeon et al. also teaches that the production tool can be
made of a thermosetting resin or a radiation cured resin. While Spurgeon et al.
lo mentions briefly that the master tool can be made by knurling, no specific method of
knurling a master tool is shown, taught, or suggested by Spurgeon et al.
Two general methods of knurling are known. Knurling is typically performed
by the first knurling process, referred to as roll knurling or form knurling. Form
15 knurling is done by pressing a knurling wheel having a pattern on the working surface
thereof against a workpiece. The knurling wheel has the inverse of the pattern that is
to be imparted to the workpiece. The working surface of the knurling tool is pressed
against the workpiece with sufficient force to cold form or press the outer surface of
the workpiece into general conformity with the pattern on the knurling wheel. The
20 second knurling process, referred to as cut knurling, is performed by orienting the
knurling wheel relative to the workpiece such that the wheel cuts a pattern into the
workpiece by removing metal chips. Both conventional knurling processes typically
impart a diamond-based pattern in which the diamonds are aligned in the direction
perpendicular to the longitudinal axis of the cylindrical workpiece. Conventional
25 knurling processes have also been used to impart a square-based pattern, in which the
squares are oriented to have their sides at 45~ to the longitudinal axis of the workpiece.
As with the diamond-based pattern, the square-based pattern is also aligned in the
direction perpendicular to the longih~ n~l axis of the cylindrical workpiece. These
~ processes are typically used to impart a non-slip pattern on a tool handle, machine
30 control knob, or the like.
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One known conventional cut knurling appal~L~ls and method is described with
reference to Figures 1-10. As seen in Figures 1-2, knurling tool ~0 is used to knurl a
pattern into the outer cylindrical surface 34 of workpiece 30. First knurling wheel 12
and second knurling wheel 14 are mounted onto knurling wheel holder 16. As seen in
s Figure 3, tool holder 16 inrllldes a pair of mounting posts which each comprise first
portion 20 and second portion 22. Cap screw 18 is inserted through the central
opening of the knurling wheel and fastened into the second portion of the mounting
post 22. First and second wheels 12 and 14 are free to rotate about axes 26 and 28
respectively. The knurling wheel holder 16 has center plane of symmetry 24. The first
10 mounting post portions 20 are parallel to plane 24. The second mounting post
portions 22 are oriented at an angle from the center plane 24. This arrangement
orients axis of rotation 26 of the first knurling wheel 12 at angle (a) relative to the
center plane 24. Angle (a) is defined as the angle between a plane perpendicular to the
plane of the page and inclll~ing axis 26 and center plane 24 perpendicular to the page.
5 The axis of rotation 28 of second wheel 14 is oriented at angle (b) relative to the
center plane 24. Angle (b) is defined as the angle between a plane perpendicular to the
plane of the page and including axis 28 and center plane 24 perpendicular to the page.
Also, as seen in Figure 6, the orientation of the second portion of the mounting post
causes the axis 26 ofthe first knurling wheel to be inclined towards the workpiece 30
20 by angle (fi). Angle (f~) is defined as the angle between a first plane tangential to the
surface of the workpiece at the point of engagement of the first knurling wheel and a
second plane perpendicular to the page and including axis 26. Similarly, the axis 28 of
the second knurling wheel is inclined towards the workpiece 30 by angle (f2) seen in
Figure 8. Angle (f2) is defined as the angle between a first plane tangential to the
25 surface of the workpiece at the point of engagement of the second knurling wheel and
a second plane perpendicular to the page and inrl~iing axis 28.
Knurling wheel 12 is illustrated in greater detail in Figures 9 and 10. Knurlingwheel 12 has along its outer working surface a plurality of teeth 44. Each tooth 44
includes tooth ridge 48, tooth valley 50 and side surfaces 52. Wheel 12 also includes
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major opposed surfaces 42 (only one illustrated). Where the side surfaces ~2 of the
teeth 44 meet the major surface 42, an edge 46 is formed. The teeth 44 have a ridge
in-llldecl angle ~. The teeth 44 of second knurling wheel 14 are ofthe same
configuration as the teeth of first knurling wheel 12.
One typical knurling tool 10 is available commercially from Eagle Rock
Technologies Int'l Corp. of Bath, Pennsylvaniat and is known as ZeusTM Cut-Knurling
Tool No. 209. As shown in Figure 3, this knurling tool 10 is typically provided with
first and second knurling wheels 12, 14 in which the teeth 44 are oriented parallel to
10 the respective wheel axis 26, 28. Accordingly, the teeth have an included angle (c)
measured at the point of contact of the wheels with the workpiece which is the sum of
angles (a) and (b), and which is centered on center plane 24. Angles (a) and (b) are
typically each 30~, resulting in angle (c) being 60~. Under this arrangement, the
knurling tool 10 will form a diamond-based knurl pattern, the four-sided diamondbases having opposed 60~ corners and 120~ corners. This knurling tool 10 also isconfigured to allow each mounting post to rotate about the longitudinal axes of its
respective first portion 20. Such rotational adjustments are calibrated to the diameter
of the workpiece 30. The adjustments are intended to orient angles (a), (b), (f,) and
(f2) to the particular workpiece to allow cut knurling of various sized workpieces
2()
The operation of known cutting tool 10 is illustrated in Figures I and 2. The
mounting posts are pivoted to the appropriate calibration for the diameter of the
workpiece to adjust angles (a), (b), (f,) and (f2). Workpiece 30 is rotated by aconventional lathe drive means in direction A. The tool 10 is moved towards the
2s workpiece 30 until the desired engagement between teeth 44 and workpiece 30 is
obtained. The rotation ofthe workpiece 30 in direction A causes the knurling wheels
to rotate in the opposite direction. Tool 10 is mounted in a suitable tool drive means
as is known in the art, and is traversed in direction B parallel to the longit~-tlin~l axis 36
ofthe workpiece 30. Accordingly, knurling begins at first end 32 ofthe workpiece 34,
and continues in direction B toward the second end (not shown). Because the bisector
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ofthe teeth in~luded angle (c) and the center plane 24 ofthe cutting tool 10 areparallel to the lon~ihlllin~l axis 36 ofthe workpiece, the diamond-based knurl pattern
is aligned in the direction perpendicular to the longitu~lin~l axis 36 of the workpiece
30.
As mentioned above, known knurling tool 10 is capable of i~lpal ling a square-
based knurl pattern in a workpiece. This is done by arranging the knurling tool as
illustrated in Figure 4. The knurling tool of Figure 4 differs from that of Figure 3 only
in that knurling wheels 12' and 14' replace wheels 12 and 14, respectively. In first
lo knurling wheel 12', the teeth 44 are oriented from the wheel axis 26 by first teeth
incline angle (d). In second knurling wheel 14', the teeth 44 are oriented away from
the wheel axis 28 by second teeth incline angle (e). It is known that angles (d) and (e)
can both be oriented relative to axes 26,28 away from the center plane 24 as
illustrated, or both towards center plane 24. Accordingly, the included angle (c)
15 formed by the teeth on each wheel is equal to the sum of angles (a) and (d) added to
the sum of angles (b) and (e). With the known commercially available tool described
above, angles (a) and (b) are each 30~, and angles (d) and (e) are each 15~. This
results in the teeth of wheels 1'7' and 14' each being oriented at 45~ from center plane
24. This forrns an included angle (c) of 90~, the bisector of which is parallel to center
20 plane 24. The operation of the tool 10 of Figure 4is as described above with respect
to the tool of Figure 3 .
The pattern imparted by the tool of Figure 4 will be a square-based pattern
which is aligned in the direction perpendicular to the longitudinal axis 36 of the
25 workpiece 30. This pattern is illustrated in Figure 13. The knurl pattern will comprise
pyramids 60 e~t~n~lin~ outward from the surface ofthe workpiece. Pyramids 60 will
have peaks 62, side edges 64, and side surfaces 66. The base of each pyramid is
defined by base edges 68. It is the 90~ angle (c) which causes the base edges 68 to
forrn a square. And because the angle (c) is centered on plane 24, the pyramidal30 pattern is aligned perpendicular to the longitudinal axis 36 of the workpiece 30. This
=
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can be seen by noting the peaks 62a, 62b of ~ c~:nt pyramids 60 are aligned on a line
perpendicular to the longitudinal axis 36 of the workpiece 30.
While the just-described commercially available knurling tool is purported to bea cut knurling tool, careful observation by the present inventors has determined that,
surprisingly, the second cutting wheel 14 does not cut a pattern into the workpiece by
removing metal chips, but instead cold forms a pattern. In this regard, the known
apparatus and method does not perform as a true cut knurling tool as that term is used
herein to describe a knurling process in which both knurling wheels cut metal bylo removing chips. The actual operation of the known knurling method is explained with
reference to Figures 5-8.
Figures 5 and 6 illustrate the orientation of first knurling wheel 12 relative to
the workpiece 30. For clarity, the remainder of tool 10 is not illustrated. As seen in
Figure 11, clearance angle a is formed between the ridges 48 of teeth 44 and theworkpiece surface. As seen in Figure 3, rotation of the workpiece 30 in direction A
causes first knurling wheel 12 to rotate in direction of motion M l . The workpiece
rotation A can be resolved into two components: l ) wheel motion M,; and
2) tangential motion T, relative to the surface of the workpiece. Tangential motion T,
20 is parallel to the longitudinal axis 36 of the workpiece and is in the direction to cause
teeth 44 to first engage the workpiece with edge 46, thus causin_ cut knurling. It can
be seen that tangential component of motion T, is equal to sin(a). As angle (a)
approaches zero, the tangential component T, approaches zero, thus the relative
motion of the cutting edge 46 of the knurling teeth to the workpiece surface also
25 approaches zero.
As seen in Figure 5, the relative motion of the workpiece and the first wheel 12is such that the workpiece is first engaged by the leading edge 46 of each of the
respective teeth 44. Figure 11 is an enlarged partially schematic view illustrating this
30 engagement. The relative motion is indicated by arrows C. It is the edge 46 at the
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intersection of teeth side surfaces 52 with major surface 42 which acts as a cutting
edge to remove materia1 from the surface 34 of the workpiece. Rake angle ~ is seen to
be inclin~d in the direction of travel of the cutting edge 46. This is referred to as
"negative rake angle" and is not as efficient as a positive rake angle, in which the rake
5 angle is inclined away from the direction of travel of the cutting edge. Figures 3, 5, 6,
and 11 illustrate that first cutting wheel 12 actually performs cut knurling. This is so
for sufficiently large values of angle (a) such that t~ngP.nti~l motion Tl is large enough
to cause cut knurling.
o Figures 7 and 8 illustrate the orientation of second knurling wheel 14 relative to
the workpiece 30. For clarity, the rem~incler oftool 10 is not illustrated. As seen in
Figure 12, clearance angle a is formed between the ridges 48 ofteeth 44 and the
workpiece surface. As seen in Figure 3, rotation ofthe workpiece 30 in direction A
causes second knurling wheel 14 to rotate in direction of motion M2. Workpiece
rotation A can be resolved into two components: I) wheel motion M2; and
2) tangential motion T2 relative to the surface of the workpiece. Tangential motion T2
is parallel to the longitudinal axis 36 ofthe workpiece, and is in the direction such that
the edge 46 of the teeth 44 is not the first element of teeth 44 to engage the workpiece.
lt can be seen that tangential component of motion T2 is equal to sin(b). As angle (b)
approaches zero, the tangential component T, approaches zero.
As seen in Figure 7, the relative motion of the workpiece and the second wheel
14 is such that the workpiece is first engaged by the ridge 48 of the tooth rather than
the edge 46. Figure 12 is an enlarged partially schematic view illustrating thisengagement. The relative motion is indicated by arrows C. Edge 46 at the intersection
of teeth side surfaces 52 with major surface 42 is actually dragged behind the direction
of relative motion. Accordingly, the workpiece is first engaged by the ridge 48 away
from edge 46. This causes the second wheel 14 to press or form rather than cut and
remove material from the workpiece 30.
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Thus it is seen that there is a need for a knurling appal ~LLIS and method which~ actually cut knurls a ~,1 kl,iece. There is also a need to provide a knurling apparatus
and method in which the knurling pattern does not align itself in the direction
s perpendicular to the lon~itll-lin~l axis of the workpiece. Additionally, there is a need to
provide a workpiece that can be used to make economically an uninterrupted
production tool of any desired length. There is a further need to provide a cut knurling
wheel which provides a positive rake angle.
10 SUMMARY OF THE INVENTION
One aspect of the present invention presents a method of knurling a workpiece
such that the knurl pattern is not aligned in the direction perpendicular to thelongitu~in~l axis of the workpiece. The method comprises the steps of:
a) imparting a first plurality of grooves to a workpiece, wherein the first
15 plurality of grooves have a first groove helix angle with respect to a reference plane
normal to the longitudinal axis of the workpiece; and
b) imparting a second plurality of grooves to the workpiece~ wherein the
second plurality of grooves have a second groove helix angle with respect to thereference plane. The second plurality of grooves intersects the first plurality of
20 grooves, thereby imparting a knurl pattern to the outer surface of the workpiece. The
pattern imparted by the method is continuous and uninterrupted around the
circumference of the workpiece, and the first and second groove helix angles are of
substantially unequal magnitude.
The above method can form, among other patterns, a plurality of pyramids on
the outer surface of the workpiece, each of said pyramids including first opposed side
surfaces formed by the first grooves and second opposed side surfaces formed by the
second grooves. In one embodiment, the pyramids are truncated pyramids. This
30 method inc,~ es both cut knurling and form knurling.
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Another aspect of the present invention pl ese-"~ a knurled workpiece formed
by the just-described method.
s A further aspect of the present invention pl ese.lLs a method of molding a
molded article with the workpiece made by the above-described method. The methodof molding a molded article comprises the steps of:
a) applying a moldable material to the outer surface of the workpiece;
b) while the moldable material is in contact with the workpiece, applying
lo sufficient force to the moldable material to impart the inverse of the pattern on the
outer surface of the workpiece to a first surface of the moldable material in contact
with the workpiece; and
c) removing the moldable material form the workpiece.
The above method can be used to make a molded article of any desired length,
in which the inverse of the knurl pattern imparted to the molded article is continuous
and uninterrupted for the length of the molded article. Such a method comprises the
additional step of:
d) rotating the workpiece at least I revolution concurrently with steps a)
20 through c) to thereby mold an article having a length greater than the circumference of
the workpiece, wherein the pattern imparted to the molded article its continuous and
uninterrupted along its length.
Another aspect of the present invention presents a molded article made
25 according to the just-described methods.
Yet another aspect of the present invention presents a knurled workpiece in
which the knurl pattern is not aligned in the direction perpendicular to the longitudinal
axis ofthe cylindrical workpiece. The knurled workpiece comprises:
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a cylindrical body having a longit~ in~1 axis and an outer cylindrical surface,
said outer surface having a knurl pattern thereon;
- wherein said knurl pattern comprises
a first plurality of grooves, said first plurality of grooves having
s a first groove helix angle with respect to a reference plane normal to
said longitudinal axis of said workpiece;
a second plurality of grooves, said second plurality of grooves
having a second groove helix angle with respect to said reference plane,
said second plurality of grooves intersecting said first plurality of
lo grooves; and
wherein said knurl pattern is continuous and uninterrupted
around the circumference of said workpiece, and wherein said first and
second groove helix angles are of substantially unequal m~gnitllde.
In one embodiment, the intersection of the first and second grooves forms a
plurality of pyramids on said outer surface of said workpiece, each of said pyramids
including first opposed side surfaces formed by said first grooves and second opposed
side surfaces formed by said second grooves. The pyramids can be truncated
pyramids.
Also presented is a method of molding a molded article with the just-described
knurled workpiece. The method comprises the steps of:
a) applying a moldable material to the outer surface of the knurled workpiece;
b) while the moldable material is in contact with the knurled workpiece,
25 applying sufficient force to the moldable material to impart the inverse of the pattern
on the outer surface of the knurled workpiece to a first surface of the moldablematerial in contact with the knurled workpiece; and
c) removing the moldable material from the knurled workpiece.
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This method can be used to mold a molded article of any desired length in
which the inverse of the knurled pattern i~ u&l Led to the molded article is continuous
and uninterrupted for the length ofthe molded article. This method comprises thefurther step of:
s d) rotating the knurled workpiece at least 1 revolution concurrently with steps
a) through c), to thereby mold an article having a length greater than the circumference
of the knurled workpiece, wherein the pattern imparted to the molded article itscontinuous and uninterrupted along its length. Also presented is a molded article made
according to the just-described method.
A still further aspect of the present invention presents a method of cut knurling
a workpiece. The method comprises the steps of:
a) rotating the workpiece in a first rotational direction about its longitudinalaxis,
b) erlg~ging the workpiece with a first knurling wheel, wherein the first
knurling wheel includes a plurality of teeth on a working surface of the knurling wheel,
the teeth each including a cutting edge on a first end thereof, and wherein the first
knurling wheel is configured so as to engage the workpiece with the cutting edge of
the teeth;
c) traversing the first knurling wheel in a direction parallel to the longitudinal
axis of the workpiece, thereby forrning a first plurality of grooves in the workpiece;
d) diseng~ging the first knurling wheel forrn the workpiece;
e) rotating the workpiece in a second rotational direction opposite to the firstrotational direction;
f) f~ng~ging the workpiece with a second knurling wheel, wherein the second
knurling wheel in~hldes a plurality of teeth on a working surface of the knurling wheel,
the teeth each including a cutting edge on a first end thereof, and wherein the second
knurling wheel is configured so as to engage the workpiece with the cutting edge of
the teeth; and
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g) traversing the second knurling wheel in a direction parallel to the
lon~ih~ n~l axis of the workpiece, thereby forming a second plurality of grooves in the
workpiece, the second plurality of grooves intersecting the first plurality of grooves,
thereby imparting a pattern to the outer surface of the workpiece, wherein the pattern
s is continuous and uninterrupted around the circumference of the workpiece.
Also presented is a workpiece made according to the just-described method, a
method of molding a molded article with a knurled workpiece made according to the
just-described method.
Still another aspect of the present inventions presents methods and apparatuses
of making structured abrasive articles with the molded articles described herein, and
such abrasive articles.
15 BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be further explained with reference to the appended
Figures, wherein like structure is referred to by like numerals throughout the several
views, and wherein:
Figure I is a partially schematic end view of a known apparatus and method for
20 knurling a workpiece;
Figure 2 is a top view of the apparatus of Figure l;
Figure 3 is an elevational view taken along Line 3-3 of Figure I of a known
knurling tool and two knurling wheels;
Figure 4 is a view like Figure 3, showing an alternative embodiment of known
25 knurling wheels;
Figure 5 is a view of a first known knurling wheel çng~ging a workpiece in a
known manner, with the holder removed for clarity;
Figure 6 is a view taken in direction 6 of the wheel of Figure 5;
Figure 7 is a view of a second known knurling wheel eng~ging a workpiece in a
30 known manner, with the holder removed for clarity;
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Figure 8 is a view taken in direction 8 of the knurling wheel of Figure 7;
Figure 9 is a plan view of a known knurling wheel;
Figure 10 is a partial cross-sectional view taken along line 10-10 ofthe wheel
of Figure 9;
Figure 1 1 is an enlarged view of the first known wheel long~ging the workpiece
when used in a known manner;
Figure 12 is an enlarged view ofthe second known wheel ~ng~ging the
workpiece when used in a known manner;
Figure 13 is a plan view of the pattern imparted on the workpiece by the known
lo knurling tool used in a known manner;
Figure 14is an elevation view of the knurling tool according to the present
invention;
Figure 15 is a partially schem~tic end view of an apparatus and one step of a
method for knurling a workpiece according to the present invention;
Figure 16 is a top view ofthe appal~Lus and workpiece of Figure 15;
Figure 17 is a view like Figure 15, showing a second step of the method
according to the present invention;
Figure 18 is a top view of the apparatus and workpiece of Figure 17,
Figure 19 is a plan view of the pattern imparted on the workpiece by the
apparatus and method of the present invention~
Figure 20iS a partial cross-sectional view taken along line 0-20 of the
workpiece of Figure 19;
Figure 21 is a partial cross sectional view of a knurling wheel according to thepresent invention;
2s Figure 22 is an enlarged view ofthe knurling wheel of Figure 21 eng~ging a
workpiece;
Figure 23iS a partially schematic view of an appal ~LLIS and method for making
a production tool according to the present invention;
Figure 24iS a plan view of the production tool of Figure 23;
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Figure 25 is a partially schPm~tic view of an appa~ s and method for making
an abrasive article with the production tool of the present invention;
Figure 26 is a view like Figure 25 of an alternate embodiment of an apparatus
and method;
s Figure 27 is a plan view of an abrasive article made in accordance with the
present invention; and
Figure 28 is a cross-sectional view taken along line 2~-28 of the abrasive article
of Figure 27.
DETA~ILED DESCRIPTION OF T~ rNV~NTION
The present invention provides novel methods and apparatuses for knurling a
workpiece. The resulting workpieces may be used to m~n~lf~cture an improved
production tool for making structured abrasive articles. Of course, the methods and
apparatuses described herein may be used to knurl workpieces for other purposes, and
for making articles from the workpieces other than the production tools described
herein.
KNIJRLING M~THOD AND APPARAT~JS
Referring to Figure 14, there is seen a knurling tool 10 according to one
preferred embodiment of the present invention. Knurling tool 10 is used to knurl a
pattern into the outer cylindrical surface 34 of workpiece 30. First knurling wheel I ''
and second knurling wheel 14 are mounted onto knurling wheel holder 16. Tool
holder 16 includes a pair of mounting posts which each comprise first portion 20 and
second portion 22. Cap screw 18 is inserted through the central opening of the
knurling wheel and fastened into the second portion of the mounting post 22. First and
second wheels 12' and 14 are free to rotate about axes 26 and 28 respectively. The
knurling wheel holder 16 has center plane of symmetry 24. The first mounting post
portions 20 are parallel to plane 24. The second mounting post portions 22 are
oriented at an angle from the center plane 24. This arrangement orients axis of
rotation 26 ofthe first knurling wheel 12' at angle (a) relative to the center plane 24.
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Angle (a) is defined as the angle between a plane perpendicular to the plane of the page
and inclu~inf~ axis 26 and center plane 24 perpen~lic~ r to the page. The axis of
rotation 28 of second wheel 14 is oriented at angle (b) relative to the center plane 24.
Angle (b) is defined as the angle between a plane perpendicular to the plane of the
s page and including axis 28 and center plane 24 perpendicular to the page. As with the
prior art tool illustrated in Figures 3, 6, and 8, the orientation of the second portion of
the mounting posts causes the axis 26 of the first knurling wheel to be inclined towards
the workpiece 30 by angle (fi) and causes the axis 28 ofthe second knurling wheel to
be inclined towards the workpiece 30 by angle (f2). Knurling tool 10 is configured to
0 allow each mounting post to rotate about the longitudinal axes of its respective first
portion 20. Such rotational adjustments are calibrated to the diameter of the
workpiece 30. The adjustments are intended to orient angles (a), (b), (f,) and (f2) to
the particular workpiece to allow cut knurling of various sized workpieces.
As seen in Figures 9 and 10, the knurling wheels each have along their outer
working surface a plurality of teeth 44. Teeth 44 include tooth ridge 48, tooth valleys
50 and side surfaces 52. Each wheel also includes major opposed surfaces 42 (only
one illustrated) Where the side surfaces 52 of the teeth 44 meet the major surface 42
an edge 46 is formed The teeth have a ridge included angle
One preferred tool holder 16 is available commercially from Eagle Rock
Technologies Int'l Corp. of Bath, Pennsylvania, and is known as ZeusTM Cut-Knurling
Tool No. 209. Angles (a) and (b) are typically each 30~, resulting in angle (c) being
60~. As discussed above, this knurling tool 10 is typically provided in a known manner
2s with first and second knurling wheels in which the teeth 44 are oriented parallel to the
respective wheel axis 26, 28, or in which the teeth on each wheel are offset an equal
amount from axes 26, 28. Accordingly, when the tool 10 is provided in a known
manner, the teeth have an included angle (c) which is centered on center plane 24.
This arrangement provides a knurling pattern which is aligned in the direction
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perpendicular to the longit~-lin~l axis 36 of the workpiece as ~ cl~sed above. In some
instances, such an arr~n~m~nt is desirable for use with the present invention.
Alternatively, as illustrated in Figure 14, the present invention provides a
s knurling tool 10 in which the first knurling wheel 12' and second knurling wheel 14
have tooth patterns of dirre~ incline angles (d) and (e). For example, wheel 12' is
illustrated as having a first wheel teeth incline angle (d) relative to wheel axis 26, and
wheel 14 is illustrated as having its teeth aligned with wheel axis 28 such that second
wheel teeth incline angle (e) is 0~. The resulting included angle (c) between the teeth is
10 thus the sum of angles (a) and (d) added to angle (b). This causes bisector of angle (c)
to be non-parallel to center plane 24 by angle (g) (as illustrated with reference to plane
24' which is parallel to center plane 24). It can be seen that angle (g) is equal to one
half of angle (d). The offset angle (g) results in a knurling pattern which is not aligned
in the direction perpendicular to the longitudinal axis 36 of the workpiece, but instead
15 has a helix angle (h) relative to the direction perpendicular to the longitudinal axis 36,
as will be discussed more fully below.
In one preferred arrangement, the first wheel angle and second wheel angles (a)
and (b) are each 30~, the first wheel tooth incline angle (d) is 30~~ and second wheel
20 tooth incline angle (e) is 0~. This provides a cutting tooth included angle (c) of 90~~
which will impart a square-based knurl pattern on the workpiece. This arrangement
also provides an included angle offset from the center plane 24, angle (g), of 15~. This
will impart a helix angle (h) on the knurling pattern on the workpiece 30, as best seen
in Figure 19. It would be expected that the offset angle (g) of the teeth included angle
25 (c) would be equal to the helix angle (h) of the pyramids on the workpiece. However,
the observations of the present inventors have been that the helix angle (h) on the
workpiece has been approximately equal to the tooth offset angle (g), but is typically
somewhat smaller than the tooth offset angle (g). It is currently believed that the effect
of the non-zero angles (f,) and (f2) causes this small difference between the values of
30 angles (g) and (h).
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Other arrangel"~ . are also possible. The wheel axis angles (a) and (b) can be
any desired angle sufficiently large to ...~ ;.. cut knurling as described above, and
can be equal to one another or not. Either, both, or neither knurling wheel may have a
5 tooth incline angle (d), (e). To provide a non-zero helix angle (h) on the knurl pattern,
it is necessary to provide some offset angle (g) to the tooth included angle (c). This
can be done by properly selecting the combination of wheel axis angles (a) and (b) with
a desired tooth incline offset (d) and (e). If angles (a) and (b) are the same, the tooth
incline angles on wheels 12 and 14 must be dirre~ t. If the tooth inclines are equal, it
10 is necessary to provide unequal wheel angles (a) and (b). If unequal wheel angles (a)
and (b) are provided, wheel tooth incline angles (d) and (e) may be the same, or they
may be different as long as they do not negate the difference between wheel angles (a)
and (b). Also, it will be recognized that it is possible to provide a helix angle (h) to the
knurl pattern with a tool 10 having a knurling teeth included angle (c) centered on
15 plane 24 with no offset (g), by rotating the entire tool l 0 relative to the longitudinal
axis 36 of the workpiece 30.
For a square-based knurl pattern. the wheel angles (a) and (b), and the tooth
incline angles (d) and (e) must be selected to provide a tooth included angle (c) of 90~
20 Diamond-based knurl patterns of any desired internal angle may be provided byselecting the wheel angles and tooth inclines to provide an angle (c) of other than 90~.
For example, as ~liccucsed above, and included angle (c) of 60~ will impart a knurl
pattern in which the diamond base has opposed 60~ corners and opposed 120~ corners.
Other commercially available tool holders which may be advantageously
employed in the present invention include, but are not limited to, the CNC-107-100
tool, available commercially forrn Dorian Tool, International of East 13ernard, Texas.
One pr~r~l l ed method of knurling a workpiece according to the present
invention is illustrated in Figures 15-18. As seen in Figure 15, cutting tool 10 is first
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provided with a first knurling wheel 12' only, without a second knurling wheel. The
workpiece 30 is rotated in direction A about its longih~ n~l axis 36. The tool 10 is
- then moved towards workpiece 30 until the desired engagement between the knurling
wheel and the workpiece is obtained. Rotation of the workpiece in direction A causes
s the first knurling wheel to rotate in the opposite direction. As seen in Figure 16, the
tool 10 is traversed in direction B parallel to the axis 36 ofthe workpiece, starting at
first end 32. The teeth 44 on first wheel 12' will then form a first helical groove pattern
in the outer surface 34 of the workpiece. The engagement of the cutting edge 46 of
the knurling teeth with the workpiece is illustrated in Figure 11. As explained with
o reference to Figure 3, the rotation of the workpiece 30 drives the knurling wheel in
direction Ml which has a tangential motion component T, relative to the surface of the
workpiece in the direction to cause the edge 46 of the knurling teeth 44 to first engage
the workpiece 30. This causes wheel 12' to cut knurl when used as described withreference to Figures 15 and 16. For a small value of clearance angle ~ and rake angle
15 ,~, the groove angle of the first plurality of grooves cut in the workpiece will be
approximately equal to the ridge included angle ~ of the knurling tooth. The helical
grooves in the workpiece will have first ridges 38 corresponding to the cutting wheel
tooth valley 50. The grooves will also have first valleys 40 corresponding to the first
wheel tooth ridges 48. The first grooves will ha~e a helix angle substantially equal tc
2() the sum of the first wheel angle (a) and tooth incline angle (d). The first groove heli~;
angle is illustrated in Figure 16 as angle Gl measured as positive when
counterclockwise from reference R which is perpendicular to the longitudinal axis 36
of the workpiece. The value of helix angle G,, and all helix angles referred to herein, is
defined as follows. The lead of the helix is first measured as the distance the helix
25 advances in one revolution. The helix angle is then defined as the arc tangent of ~
times the diameter of the helix divided by the lead of the helix. The helical angles as
- illustrated in the appended Figures have been somewhat simplified, and are indicated
for illustrative purposes. In one pl ~r~ d embodiment, tool holder 16 is configured to
have a first wheel angle (a) of 30~ and a first wheel tooth incline angle (d) of 30~, such
30 that the first grooves will have a helix angle Gl substantially equal to 60~. The
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clearance angle a and the direction of relative motion between the workpiece 30 and
the first knurling wheel 12' which causes cutting ~n~ m~nt by edge 46 is primarily
dete~ ned by the direction of rotation A rather than relatively small traverse rate in
direction B. Accordingly, it is also possible to traverse the tool 10 in the direction
from second end ofthe workpiece 30 to the first end 32 to cut knurl the first helix
groove pattern.
After the first grooves are formed, the first wheel 12'is removed, and second
wheel 14 is attached to the holder 16 as illustrated in Figure 17. Workpiece 30iS now
o rotated in direction A' opposite to that when first wheel 12' was present. The tool 10 is
then moved towards workpiece 30 until the desired engagement between the second
knurling wheel 14 and the workpiece is obtained. Rotation of the workpiece in
direction A' causes the second knurling wheel to rotate in the opposite direction. As
seen in Figure 18, the tool 10 is traversed in direction B parallel to the axis 36 ofthe
workpiece, starting at first end 32. The teeth 44 on first second wheel 14 will then
form a second helical groove pattern in the outer surface 34 of the workpiece. These
grooves will cross the first grooves. The engagement of the cutting edge 46 of the
knurling teeth with the workpiece is seen in Figure 11. Referring back to the
description of wheel 14 when used in the conventional manner described in Figure 3, it
2() is seen that tangential motion T2 causes the wheel to form knurl rather than cut knurl
when used in the conventional manner. However, when the workpiece is rotated in
direction A' in accordance with the present invention, the rotation of the workpiece
drives the second wheel to rotate in direction M2 opposite to that of the known manner
shown in Figure 3. This reversed motion component M2 of the wheel has a tangential
component T2 relative to the surface of the workpiece and parallel to the longitudinal
axis 36 in the direction causing the edge 46 of the teeth to first engage the workpiece,
thus allowing the wheel 14 to cut knurl when used in accordance with the presentinvention. This provides cut knurling for both of the first and second knurling wheels.
As discussed above, for a small value of clearance angle a and rake angle ~, the angle
of the groove cut in the workpiece will be approximately equal to the ridge included
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angle ~ of the knurling tooth. The second helical grooves in the workpiece will have
second ridges 38' corresponding to the cutting wheel tooth valley S0. The secondgrooves will also have second valleys 40' corresponding to the first wheel tooth ridges
48. The helix angle of the second grooves will be substantially equal to the sum of the
5 second wheel angle (b) and the second wheel tooth incline angle (e). This is
illustrated in Figure 18 as second groove helix angle G2 measured as positive when
clockwise from reference R. In one p,e~l,~d embodiment, tool holder 16 is
configured to have a second wheel angle (b) of 30~ and a second wheel tooth incline
angle (e) of 0~. The second grooves will then be perpendicular to the first grooves,
lo forming a square-based knurl pattern on the workpiece 30. As with the first cutting
wheel, the clearance angle a and the direction of relative motion between the
workpiece 30 and the second knurling wheel 14 which causes cutting engagement byedge 46 is primarily determined by the direction of rotation A' rather than relatively
small traverse rate in direction B. Accordingly, it is also possible to traverse the tool
10 in the direction from second end ofthe workpiece 30 to the first end 32 to cut knurl
the second helix groove pattern.
The ability to perform true cut knurlin.~s with the above apparatus and method
provides the following advantages over forrn knurling Cut knurling allows imparting a
20 knurl pattern in harder workpieces than is possible with form knurling. This allows for
the use of harder, more corrosion resistant materials for the workpiece 30.
Additionally, cut knurling can be performed with less force applied to the workpiece by
the tool holder than with form knurling. This makes for easier m~n~lfacturing, and
reduces the wear and distortion on the tool holder and workpiece. Cut knurling also
25 does not increase the outer diameter ofthe workpiece 30 as happens with form
knurling. Furthermore, cut knurling provides better defined grooves in the workpiece
than does form knurling, providing the capability to better control the size andconfiguration of the pyramids 60. Also, cut knurling is able to easily create groove
geometries other than the V-shaped grooves just described, while form knurling is not
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well suited for creating groove geometries which would require pressing or cold
rc" Il.,n~, a subsl~Lial amount of material in the ~o~ kp:ece.
The rotational rate of the workpiece, advance rate of the knurling tool, and
s cutting depth can be selected to provide the desired results. The following parameters
have been found to be useful, although the present invention is not thereby limited:
workpiece rotational speed of 50 to l O0 r.p.m.; tool advance per revolution of
workpiece is from 0.13 to 0.25 mm (0.005 to 0.010 in); and knurl groove depths of
from 0.25 to 0.91 mm (0.010 to 0.036 in). The full desired depth ofthe grooves may
o be obtained in a single pass with the knurling tool, or multiple passes of increasing
depth may be made until the desired groove depth is obtained. Furthermore, where it
is desired that the first and second grooves have the same depth, this may be easier to
obtain by the method just described, in which one knurling wheel is used at a time.
Knurling is preferably done in the presence of a suitable lubricant/coolant introduced
1S onto the workpiece at the knurling wheels as is well known in the art.
The knurl pattern formed by the just-described method and apparatus is
illustrated in Figure 19. The knurl pattern comprises a plurality of pyramids 60projecting from the workpiece 60. The pyramids each comprise peak 62, side edges20 64 extending from the peak, base edges 68~ and sides surfaces 66 bounded by the side
edges and base edges. When cutting tool 10 is configured to have a tooth included
angle (c) with a bisector that is non-parallel to the center plane 24 by angle (g), this
will impart a helix angle (h) approximately equal to angle (g) on the knurling pattern as
illustrated in Figure 19. That is, the helix angle (h) is oblique (not 0~ or 90~) in
2s contrast to prior knurl patterns which are aligned around the circumference of the
workpiece in a direction perpendicular to the longitll~in~l axis of the workpiece. A
cross section of the pyramids 60 is illustrated in Figure 20. The first plurality of
grooves have groove sides 66a which are intersected by the second plurality of
grooves having groove sides 66b. The intersection of the two sets of grooves thus
30 forms the pyramids 60. Each pyramid has a pair of opposed sides 66a formed by
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c~nt first grooves and a pair of opposed sides 66b formed by 2~ cent second
grooves. It is seen that the grooves cut by the knurling teeth 40 have an angle ~ that
will be sub~ y equal to the ridge inr.luded angle ~ of the knurling teeth for a small
value of clearance angle a and rake angle ,B. The pyramid peaks will then have an
s internal angle of ~, which will be equal to ~. In one p~ere~ d embodiment, theknurling wheel tooth angle ~ is 90~, resulting in a pyramid peak internal angle ~ of 90~.
Tooth angle ~ other than 90~ may be used, imparting a pyramid peak included angle
of other than 90~.
The knurl pattern is illustrated herein as having pyramidal peaks which come to
a point at 62. This occurs when the cutting wheel teeth 44 are engaged to their full
depth into the workpiece, en~ging the workpiece to their full extent at edge 46 from
ridge 48 to valley 50. Other patterns are also attainable with the present invention.
For example, truncated pyramids, that is pyramids with flat tops rather than pointed
15 peaks 62, can be made by engaging the knurling teeth 44 for only a portion of their
depth. By engaging the teeth 44 to a partial depth, the edge 46 will not engage all the
way up to tooth valley 50. This will leave a portion of outer surface 34 of workpiece
30 in its original, unknurled condition, providing a truncated top to the pvramids 60 lt
is also possible to use teeth 44 configured to have flat or curved spaces between the
20 teeth 44 at valley 50, or a flat or other configuration at 48 rather than an edge ridge
Knurl patterns having a non-zero helix angle (h) can also be obtained in
accordance with the present invention by form knurling. In such an arrangement, the
knurling tool 10 and knurling wheels 12, 14 are configured such that edge 46 does not
25 have a sufficiently large tangential component of motion T, or T2 relative to the
workpiece 30. Thus, rather than being cut with tooth edge 46, the knurl pattern is
- pressed or formed by the ridge 48 of the teeth. To forrn or press the knurl the pattern
with a helix angle (h), the angles (a), (b), (d) and (e) are selected as described herein so
that the bisector of teeth included angle (c) is non-parallel to center plane 24 to
30 provide offset angle (g).
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An aleernate embodiment ofthe knurling wheel 12 according to the present
invention is illustrated in Figure 21. In this embodiment, the major surface 42 ofthe
knurling wheel has been undercut at 54. Undercut 54is illustrated as an arcuate
5 surface extending around the full circumference of wheel 12. The undercut provides
an improved rake angle ~ as illustrated in Figure 22. The undercut 54 can instead be
flat or any other configuration to provide a zero or positive rake angle. The undercut
54 preferably extends to ridge 48 in one direction, and extends far enough inward from
ridge 48 to improve the cutting characteristics of edge 46 and major surface 42,o preferably at least as far as tooth valley 50. A zero or positive rake angle ,~ provides
more efficient cutting than the negative rake angle described above with respect to
known cutting wheels and also reduces the amount of burring of the workpiece.
While the knurling teeth 44 are illustrated herein as forming a ridge at 48 and a
5 valley at 50, knurling teeth of other profiles can be advantageously used with the
present invention. For example, rather than coming to a line or edge at ridge 48 and
valley 50, the ridge 48 or valley 50 can instead comprise a flat surface, rounded
surface, or other contour. Also, teeth side surfaces 52 can be curved or other profiles
rather than planar. These alternate tooth configurations are better suited for use uith
20 cut knurling rather than form knurling, although certain configurations may be used
under some conditions with form knurling.
MPLDED ARTICLE
One pleÇ~"ed method of using workpiece, or master tool, 30 to fabricate a
2s molded article such as a production tool, is illustrated in Figure 23. The production
tool 82is fabricated by extruding at station 100 a moldable material, preferably a
thermoplastic material, onto the knurled outer surface 34 of master tool30. The
thermoplastic material is forced against surface 34 at nip 102. Production tool 82is
then peeled away from the master tool 30 and wound onto mandrel 106. In this
30 manner, a production tool 82 of any desired length may be obtained. The molding
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surface 86 will have the inverse of the pattern on the knurled outer surface 34 of
master tool 30. When the pattern impa"ed on outer surface 34 of master tool 30 is a
- positive ofthe pattern ofthe Illtim~te fabricated structured abrasive article (or other
article as desired), the pattern on mold surface 86 will be the inverse of the pattern of
5 the ultimate article. As seen in Figure 24, the production tool mold surface 86
comprises a plurality of pyramidal pockets 88 which are the inverse of the pyramids 60
on master tool 30. Pyramidal pockets include bottom point 90, side edges 92, side
surfaces 94, and upper edges 96. When the master tool 30 has a knurl pattern with a
helix angle (h), the pyramidal pocket pattern in the molded article will have an angle
lo (h) relative to the longitudinal axis of the article of equal magnitude and opposite
direction the angle (h) on the master tool. Back surface 84iS relatively flat and
smooth. It may be desired that production tool 82iS the ultimate fabricated article, in
which case the pattern on the outer surface 34 of master tool 30 will be the negative or
inverse of the desired ultim~te pattern on production tool 82.
Thermoplastic materials that can be used to construct the production tool 82
include polyesters, polycarbonates, poly(ether sulfone), polyethylene. polypropylene,
poly(methyl meth~crylate), polyurethanes, polyamides, polyvinylchloride, polyolefins,
polystyrene, or combinations thereof. Thermoplastic materials can include additives
20 such as plasticizers, free radical scavengers or stabilizers, thermal stabilizers,
antioxidants, ultraviolet radiation absorbers, dyes, pigments, and other processing
aides. These materials are preferably substantially transparent to ultraviolet and visible
radiation.
2s Because the workpiece, or master tool, 30 has a continuous, uninterrupted
knurled pattern around its circumference, a production tool of any desired length in
direction D may be economically molded without seams or interruptions on the
molding pattern. This will allow for the production of structured abrasive articles of
any length with an uninterrupted structured abrasive composite pattern. Such
structured abrasive articles will be less likely to shell or dçl~min~te than other
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structured abrasive articles which have a seam or interruption in the pattern due to
seams in the production tool.
The production tool 82 can also be formed by embossing a moldable material
5 with the knurled master tool 30. This can be done at the required force and
temperature so as to impart the mold surface 86 of the production tool with the inverse
of the knurl pattern on the workpiece. Such a process can be used with single layer or
multiple layer production tools 82. For example, in a multiple layer production tool,
the mold surface 86 can comprise a material suitable to be molded into the desired
10 pattern, while the back surface 84 can comprise a suitably strong or durable material
for the conditions to which the production tool 82 will be subjected to in use.
The production tool 82 can also be made of a cured thermosetting resin. A
production tool made of thermosetting material can be made according to the
5 following procedure. An uncured thermosetting resin is applied to a master tool 30.
While the uncured resin is on the surface of the master tool, it can be cured orpolymerized by heating such that it will set to have the inverse shape of the pattern of
the surface of the master tool. Then, the cured thermosetting resin is removed from
the surface of the master tool. The production tool can be made of a cured radiation
20 curable resin, such as, for example acrylated urethane oligomers. Radiation cured
production tools are made in the same manner as production tools made of
thermosetting resin, with the exception that curing is conducted by means of exposure
to radiation e.g. ultraviolet radiation.
While the inventive methods and apparatuses described herein are particularly
well suited for use in m~n~lf~r~hlring structured abrasives, the present invention is not
thereby limited. For example, the inventive knurling methods and appa. ~LIlses
described herein may be used on a workpiece 30 that is the Illtim~tc m~nllf~ctllred
article having its own use, rather than a master tool to be used in subsequent
processes. Additionally, when the workpiece is a master tool, its use is not limited to
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making a production tool for use in subsequent processes. That is, the molded article
which is molded with the knurled workpiece may be the l~itim~te m~mlf~r,tllred article
- having its own use. Furthel,llole, the knurled workpiece 30 can be used as a
rotogravure coater for making abrasive or other articles
METHOD OF MAKING A STRUCTURED ABRASIVE ARTICLE
The first step to make the abrasive coating is to prepare the abrasive slurry.
The abrasive slurry is made by combining together by any suitable mixing technique the
binder precursor, the abrasive particles and the optional additives. Examples of mixing
10 techniques include low shear and high shear mixing, with high shear mixing being
pl er~l, ed. Ultrasonic energy may also be utilized in combination with the mixing step
to lower the abrasive slurry viscosity. Typically. the abrasive particles are gradually
added into the binder precursor. The amount of air bubbles in the abrasive slurry can
be l~ ni7ed by pulling a vacuum during the mixing step. In some instances it is
15 preferred to heat the abrasive slurry to a temperature to lower its viscosity as desired.
For example, the slurry can be heated to approximately 30~C to 70~C. However, the
temperature of the slurry should be selected so as not to deleteriously affect the
substrate to which it is applied. lt is important that the abrasive slurry have a rheology
that coats well and in which the abrasive particles and other fillers do not settle.
2n
There are two main methods of making the abrasive coating of this invention.
The first method generally results in an abrasive composite that has a precise shape.
To obtain the precise shape, the binder precursor is at least partially solidified or gelled
while the abrasive slurry is present in the cavities of a production tool. The second
25 method generally results in an abrasive composite that has a non-precise shape. In the
second method, the abrasive slurry is coated into cavities of a production tool to
generate the abrasive composites. However, the abrasive slurry is removed from the
production tool before the binder precursor is cured or solidified. Subsequent to this,
the binder precursor is cured or solidified. Since the binder precursor is not cured
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while in the cavities of the production tool this results in the abrasive slurry flowing
and distorting the abrasive composite shape.
For both methods, if a thermosetting binder precursor is employed, the energy
s source can be thermal energy or radiation energy depending upon the binder precursor
chemistry. For both methods, if a thermoplastic binder precursor is employed thethermoplastic is cooled such that it becomes solidified and the abrasive composite is
formed.
lo Figure 25 illustrates schematically a method and apparatus 110 for making an
abrasive article. A production tool 82 made by the process described above is in the
form of a web having mold surface 86, back surface 84, and two ends. A substrate112 having a first major surface 113 and a second major surface 114 leaves an unwind
station 1 15. At the same time, the production tool 82 leaves an unwind station 1 16.
5 The mold or contacting surface 86 of production tool 82is coated with a mixture of
abrasive particles and binder precursor at coating station 1 18. The mixture can be
heated to lower the viscosity thereof prior to the coating step. The coating station 1 18
can comprise any conventional coating means, such as knife coater, drop die coater,
curtain coater, vacuum die coater, or an extrusion die coater. After the mold surface
20 86 of production tool 82is coated, the substrate 1 12 and the production tool 82 are
brought together such that the mixture wets the first major surface 1 13 of the substrate
112. In Figure 25, the mixture is forced into contact with the substrate 112 by means
of a contact nip roll 120, which also forces the production tool/mixture/backingconstruction against a support drum 122. It has been found useful to apply a force of
25 45 pounds with the nip roll, although the actual force selected will depend on several
factors as is known in the art. Next, a sufficient dose of energy, preferably radiation
energy, is transmitted by a radiation energy source 124 through the back surface 84 of
production tool 82 and into the mixture to at least partially cure the binder precursor,
thereby forming a shaped, handleable structure 126. The production tool 82is then
30 separated from the shaped, handleable structure 126. Separation ofthe production
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tool 82 from the shaped, handleable structure 126 occurs at roller 127. Examples of
materials suitable for production tool 82 include polycarbonate, polyester,
polypropylene, and polyethylene. In some production tools made of thermoplastic
material, the operating conditions for making the abrasive article should be set such
s that excessive heat is not generated. If excessive heat is generated, this may distort or
melt the thermoplastic tooling. In some instances, ultraviolet light generates heat.
Roller 127 can be a chill roll of suff~cient size and temperature to cool the production
tool as desired. The contacting surface or mold surface 86 of the production tool may
contain a release coating to permit easier release of the abrasive article from the
o production tool. Examples of such release coatings include silicones and
flourochemicals. The angle y between the shaped, handleable structure 126 and the
production tool 82 immediately after passing over roller 127 is preferably steep, e.g., in
excess of 30~, in order to bring about clean separation of the shaped, handleable
structure 126 from the production tool 82. The production tool 82 is rewound on
mandrel 128 so that it can be reused. Shaped, handleable structure 126 is wound on
mandrel 130. If the binder precursor has not been fully cured, it can then be fully
cured by exposure to an additional energy source, such as a source of thermal energy
or an additional source of radiation energy, to form the coated abrasive article.
Alternatively, full cure may eventually result without the use of an additional energy
2() source to form the coated abrasive article. As used herein, the phrase "full cure" and
the like means that the binder precursor is sufficiently cured so that the resulting
product will function as an abrasive article, e.g. a coated abrasive article.
After the abrasive article is formed, it can be flexed and/or humidified prior to
converting. The abrasive article can be converted into any desired form such as a
cone, endless belt, sheet, disc, etc. before use.
Figure 26 illustrates an apparatus 140 for an alternative method of preparing anabrasive article. In this apparatus, the production tool 82 is an endless belt having
contacting or mold surface 86 and back surface 84. A substrate 142 having a first
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major surface 143 and a second major surface 141 leaves an unwind station 145. The
mold surface 86 of the production tool is coated with a mixture of abrasive particles
and binder precursor at a coating station 146. The mixture is forced against the first
surface 143 ofthe substrate 142 by a contact nip roll 148, which also forces the5 production tooVmixture/backing construction against a support drum 150, such that
the mixture wets the fist major surface 143 of the substrate 142. The production tool
82iS driven over three rotating mandrels 152,154, and 156. Energy, preferably
radiation energy, is then transmitted through the back surface 84 of production tool 82
and into the mixture to at least partially cure the binder precursor. There may be one
10 source of radiation energy 158. There may also be a second source of radiation energy
160. These energy sources may be of the same type or of different types. A~er the
binder precursor is at least partially cured, the shaped, handleable structure 162is
separated from the production tool 82 and wound upon a mandrel 164. Separation of
the production tool 82 from the shaped, handleable structure 162 occurs at roller 165.
The angle y between the shaped, handleable structure 162 and the production tool 82
immediately after passing over roller 165is preferably steep, e.g., in excess of 30~, in
order to bring about clean separation of the shaped, handleable structure 16 from the
production tool 8''. One of the rollers, for example roller 152, can be a chill roll of
sufficient size and temperature to cool production tool 82 as desired. lf the binder
2~) precursor has not been fully cured, it can then be fully cured by exposure to an
additional energy source, such as a source of thermal energy or an additional source of
radiation energy, to form the coated abrasive article. Alternatively, full cure may
eventually result without the use of an additional energy source to form the coated
abrasive article.
After the abrasive article is formed, it can be flexed and/or humidified prior to
converting. The abrasive article can be converted into any desired form such as a
cone, endless belt, sheet, disc, etc. before use.
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In either embodiment, it is often desired to completely fill the space between
the cont~ctin~ surface of the production tool and the front surface of the backing with
~ the mixture of abrasive particles and binder precursor. Also in either embodiment, it is
possible to apply the slurry to the substrate 112 and contact the slurry with the
s production tool rather than coating the slurry into the production tool and cont~-,ting
the slurry with the substrate.
In a p~erelled method ofthis embodiment, the radiation energy is transmitted
through the production tool 82 and directly into the mixture. It is p, erel, ed that the
lo material from which the production tool 82 is made not absorb an appreciable amount
of radiation energy or be degraded by radiation energy. For example, if electron beam
energy is used, it is prere" èd that the production tool not be made from a cellulosic
material, because the electrons will degrade the cellulose. If ultraviolet radiation or
visible radiation is used, the production tool material should transmit suffcient
15 ultraviolet or visible radiation, respectively, to bring about the desired level of cure.
Alternatively, the substrate 1 12 to which the composite is bonded may allow
transmission of the radiant energy therethrough. When the radiation is transmitted
through the tool, substrates that absorb radiation energy can be used because the
radiation energy is not required to be transmitted through the substrate.
The production tool 82 should be operated at a velocity that is sufficient to
avoid degradation by the source of radiation. Production tools that have relatively
high resistance to degradation by the source of radiation can be operated at relatively
lower velocities; production tools that have relatively low resistance to degradation by
25 the source of radiation can be operated at relatively higher velocities. In short, the
a,opl op, iate velocity for the production tool depends on the material from which the
production tool is made. The substrate to which the composite abrasive is bondedshould be operated at the same speed as the production tool. The speed, along with
other parameters such as temperature and tension, should be selected so as not to
30 deleteriously affect the substrate or the production tool. Substrate speeds of from 15
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to 76 meters/min. (50 to 250 feetJmin.) have been found advantageous, however other
speeds are also within the scope of the invention.
A prefel l ed embodiment of an abrasive article 200 provided in accordance with
the above-described method is illustrated in Figures 27 and 28. Abrasive article 200
includes substrate 112 having first major surface 113 and second major surface 114.
Structured abrasive composites 212 are bonded to first major surface 113 of substrate
112. Composites 212 comprise abrasive particles 213 dispersed in binder 214.
Surfaces 215 define the precise shapes of the composites 212 as discussed above. As
lo illustrated in Figure 28, composites 212 can abut one another at their bases. The
configuration of composites 212 will substantially conform to the configuration of the
pyramids 60 on workpiece 30, and will be substantially the inverse of the pyramidal
pockets 88 on production tool 82. When the knurl pattern on the master tool 30 has a
helix angle (h), the abrasive article will have abrasive composites arranged in a pattern
with an angle (h) relative to the longitudinal axis of the abrasive article. This provides
the functional advantage of avoiding "scribing" the surface that is abraded by the
abrasive article 200. Scribing can occur when the abrasive composites 212 are aligned
so as to more heavily abrade a surface along the line of the peaks of the composites
212 in the composite pattern. For a sufficiently large angle (h), scribing can be avoided
when abrading a surface with abrasive article 200.
Ener~ Sources
When the abrasive slurry comprises a thermosetting binder precursor, the
binder precursor is cured or polymerized. This polymerization is generally initiated
upon exposure to an energy source. Examples of energy sources include thermal
energy and radiation energy. The amount of energy depends upon several factors such
as the binder precursor chemistry, the dimensions of the abrasive slurry, the amount
and type of abrasive particles and the amount and type of the optional additives. For
thermal energy, the temperature can range from about 30 to 150~C, generally between
40 to 120~C. The time can range from about 5 minutes to over 24 hours. The
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radiation energy sources include electron beam, ultraviolet light, or visible light.
Electron beam radiation, which is also known as ionizing radiation, can be used at an
energy level of about 0.1 to about 10 Mrad, preferably at an energy level of about 1 to
about 10 Mrad. Ultraviolet radiation refers to non-particulate radiation having a
wavelength within the range of about 200 to about 400 nanometers, preferably within
the range of about 250 to 400 nanometers. It is plerelled that 300 to 600 Watt/inch
ultraviolet lights are used. Visible radiation refers to non-particulate radiation having a
wavelength within the range of about 400 to about 800 nanometers, preferably in the
range of about 400 to about 550 nanometers. Other energy sources include infrared
0 and microwave.
Substrate
Materials suitable for the substrate 1 12 of the abrasive article 200 described
herein include polymeric film~ paper, cloth, metallic film, vulcanized fiber, nonwoven
15 substrates, combinations of the foregoing, and treated versions of the foregoing. It is
preferred that the polymeric film backing be primed or otherwise treated as is known in
the art to improve adhesion of the abrasive coating.
Abrasive Coatin~
The abrasive coating suitable for use with making abrasive articles according tothe methods described herein comprises a plurality of precisely shaped abrasive
composites 200, wherein the abrasive composites comprise a plurality of abrasiveparticles 213 dispersed in a binder 214. The binder can bond the abrasive composites
to the first major surface ofthe substrate. The abrasive composite preferably has a
25 discernible precise shape. It is ~l~r~:lled that the abrasive grains do not protrude
beyond the planes of the shape before the coated abrasive article is used. As the
coated abrasive article is used to abrade a surface, the composite breaks down
revealing unused abrasive grains.
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The e~pl~s~ion "precisely shaped abrasive composite," as used herein, refers to
abrasive composites having a shape that has been formed by curing a flowable rnixture
of abrasive grains and curable binder while the mixture is both being borne on asubstrate and filling a cavity on the surface of a production tool. Such a precisely
shaped abrasive composite would thus have precisely the same shape as that of the
cavity. A plurality of such composites provide three-dimensional shapes that project
outwardly from the surface of the substrate in a non-random pattern, namely the
inverse of the pattern of the production tool. Each composite is defined by a
boundary, the base portion of the boundary being the interface with the substrate to
o which the precisely shaped composite is adhered. The rf m~ining portion of the
boundary is defined by the cavity on the surface of the production tool in which the
composite was cured. The entire outer surface of the composite is confined, either by
the substrate or by the cavity, during its formation. The abrasive composites can be
formed from a slurry comprising a plurality of abrasive grains dispersed in an uncured
ungelled binder referred to as a binder precursor. Upon curing or gelling, the abrasive
composites are set, i.e., fixed. in the predetermined shape and predetermined array
The ratio, based on weight, of abrasive grain to binder ~enerally ranges from
about I I to 4.1, preferably from about 2 1 to 3.1 This ratio v aries depending upon
2(~ the size of the abrasive grains and the type of binder employed
Abrasive Particles
The abrasive particles 213 ofthe abrasive coating typically have a particle sizeranging from about 0.1 to 1500 micrometers, preferably between about 0.1 to 400
micrometers and more preferably between 0.1 to 100 micrometers. A narrow
distribution of particle size can often provide an abrasive article capable of producing a
finer finish on the workpiece being abraded. Examples of such abrasive particlesinclude fused aluminllm oxide (which includes brown ~IIlminllm oxide, heat treated
alllminum oxide, and white all-minum oxide), ceramic ~luminum oxide, silicon carbide
(inclu~ing green, white, and black), chromia, ~IIlmin~ zirconia, diamond, iron oxide,
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ceria, cubic boron nitride, boron carbide, garnet, and col-lbindLions thereof. One
example of a suitable heat treated ~lllmimlm oxide, grade P-240, is commerciallyavailable from H.C. Starck GmbH & Co., of Gusler, Germany.
The term "abrasive particles" also encompasses when single abrasive particles
are bonded together to form an abrasive agglomerate. Abrasive agglomerates are
known in the art and are exemplified by U.S. Patent Nos. 4,311,489 (Kressner);
4,652,275 (Bloecher et al.) and 4,799,939 (Bloecher et al.).
0 It is also possible to have a surface coating on the abrasive particles. The
surface coating may have many different functions. In some instances the surfacecoatings increase adhesion to the binder, alter the abrading characteristics of the
abrasive particle and the like. Examples of surface coatings include coupling agents,
halide salts, metal oxides including silica, refractory metal nitrides, refractory metal
carbides and the like.
In the abrasive composite there may also be diluent particles. The particle sizeof these diluent particles may be on the same order of magnitude as the abrasiveparticles. Examples of such diluent particles include gypsum, marble, limestone, flint~
silica, glass bubbles, glass beads, aluminum silicate. and the like.
Binder
The abrasive particles are dispersed in an organic binder 214 to form the
abrasive composite coating. The binder must be capable of providing a medium in
which the abrasive grains can be distributed. The binder is preferably capable of being
cured or gelled relatively quickly so that the abrasive article can be quickly fabricated.
Some binders gel relatively quickly, but require a longer time to fully cure. Gelling
preserves the shape of the composite until curing commences. Fast curing or fastgelling binders result in coated abrasive articles having abrasive composites of high
consistency. The organic binder can be a thermoplastic binder, however, it is
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preferably a thermosetting binder. The binder is formed from a binder precursor.During the m~mlf~ctllre of the abrasive coating, the thermosetting binder precursor is
exposed to an energy source which aids in the initiation of the poly~ ~alion or curing
process. Examples of energy sources include thermal energy and radiation energy
5 which includes electron beam, ultraviolet light, and visible light. After thispolymerization process, the binder precursor is converted into a solidified binder.
Alternatively for a thermoplastic binder precursor, during the m~nuf~ctl~re of the
abrasive article the thermoplastic binder precursor is cooled to a degree that results in
solidification of the binder precursor. Upon solidification of the binder precursor, the
lo abrasive composite is formed.
The binder in the abrasive composite is generally also responsible for adhering
the abrasive composite to the first major surface of the substrate. However, in some
instances there may be an additional adhesive layer between the surface of the substrate
5 and the abrasive composite. This additional adhesive can be selected from the various
binders described herein, or may be any other suitable binder.
There are two main classes of thermosetting resins, condensation curable and
addition polymerized resins. The preferred binder precursors are addition polymerized
20 resin because they are readily cured by exposure to radiation energy. Addition
polymerized resins can polymerize through a cationic mechanism or a free radicalmechanism. Depending upon the energy source that is utilized and the binder
precursor chemistry, a curing agent, initiator, or catalyst is sometimes preferred to help
initiate the polymerization.
Examples of typical binders precursors include phenolic resins~ urea-
formaldehyde resins, melamime formaldehyde resins, acrylated urethanes, acrylated
epoxies, ethylenically unsaturated compounds, aminoplast derivatives having pendant
unsaturated carbonyl groups, isocyanurate derivatives having at least one pendant
30 acrylate group, isocyanate derivatives having at least one pendant acrylate group, vinyl
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ethers, epoxy resins, and mixtures and con~l.i,.ations thereof. The term aclylate
encomp~ses acrylates and meth~crylates.
Phenolic resins are widely used in abrasive article binders because of their
thermal properties, availability, cost and ease of h~n~iling There are two types of
phenolic resins, resole and novolac. Resole phenolic resins have a molar ratio of
formaldehyde to phenol of at least 1: 1, typically from 1.5: 1 to 3: 1. Novolac resins
have a molar ratio of formaldehyde to phenol of less than 1: 1. Examples of
commercially available phenolic resins include those known by the tradenames "Durez"
o and "Varcum" from Occidental Chemicals Corp.; "Resinox" from Monsanto;
"Aerofene" from Ashland Chemical Co. and "Arotap" from Ashland Chemical Co.
Acrylated urethanes are diacrylate esters of hydroxy termin~ted NCO extended
polyesters or polyethers. Examples of commercially available acrylated urethanesinclude "UVITHANE 782", available from Morton Thiokol Chemical, and "CMD
6600", "CMD 8400", and "CMD 8805", available from Radcure Specialties.
Acrylated epoxies are diacrylate esters of epoxy resins, such as the diacrylate
esters of bisphenol A epoxy resin. Examples of commercially available acrylated
epoxies include "CMD 3500", "CMD 3600", and "CMD 3700'', available from
Radcure Specialities.
Ethylenically unsaturated resins include monomeric or polymeric compounds
that contain atoms of carbon, hydrogen, and oxygen, and optionally, nitrogen and the
2s halogens. Oxygen or nitrogen atoms or both are generally present in ether, ester,
urethane, amide, and urea groups. Ethylenically unsaturated compounds preferablyhave a molecular weight of less than about 4,000 and are preferably esters made from
the reaction of compounds cont~ining aliphatic monohydroxy groups or aliphatic
~ polyhydroxy groups and unsaturated carboxylic acids, such as acrylic acid, meth~.rylic
acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and the like.
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Representative examples of acrylate resins include methyl meth~crylate, ethyl
meth~erylate styrene, divinylbel-2e.le, vinyl toluene, ethylene glycol diacrylate, ethylene
glycol meth~crylate, hexanediol diacrylate, triethylene glycol diacrylate, trimethylol
propane triacrylate, glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol
5 methacrylate, pentaerythritol tetraacrylate and pentaerythritol tetraacrylate. Other
ethylenically unsaturated resins include monoallyl, polyallyl, and polymethallyl esters
and amides of carboxylic acids, such as diallyl phth~l~te/ diallyl ~lip~te, and N,N-
diallyladipamide. Still other nitrogen co~ g compounds include tris(2-acryloyl-
oxyethyl)isocyanurate, 1,3,5-tri(2-methyacryloxyethyl)-s-triazine, acrylamide,
0 methylacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone,
and N-vinylpiperidone.
The aminoplast resins have at least one pendant alpha, beta-unsaturated
carbonyl group per molecule or oligomer. Examples of such materials include N-
(hydroxymethyl)-acrylamide, N,N'-oxydimethylenebisacrylamide, ortho and para
acrylamidomethylated phenol, acrylamidomethylated phenolic novolac, and
combinations thereof. These resins are known in the art and are exemplified by U.S.
Patent Nos. 4,903.440 (Larson et al.) and 5, 36,47~ (Kirl;).
2n Isocyanurate derivatives having at least one pendant acrylate group andisocyanate derivatives having at least one pendant acrylate group are exemplified by
U.S. Patent 4,652,274 (Beottcher et al.). The preferred isocyanurate material is a
triacrylate of tris(hydroxy ethyl) isocyanurate.
2~ Epoxy resins have an oxirane and are polymerized by the ring opening. Such
epoxide resins include monomeric epoxy resins and oligomeric epoxy resins. Examples
of some p~er~l l ed epoxy resins include 2,2-bis[4-(2,3-epoxypropoxy)-phenyl propane]
(diglycidyl ether of bisphenol) and commercially available materials under the trade
design~tion "Epon 828", "Epon 1004", and "Epon 1001F" available from Shell
Chemical Co., "DER-331 ", "DER-332", and "DER-334" available from Dow Chemical
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Co. Other suitable epoxy resins include glycidyl ethers of phenol formaldehyde
novolac (e.g., "DEN-431 " and "DEN-428" available from Dow Chemical Co.).
The epoxy resins of the invention can polymerize via a cationic mechanism with
5 the addition of an appropriate cationic curing agent. Cationic curing agents generate
an acid source to initiate the polymerization of an epoxy resin. These cationic curing
agents can include a salt having an onium cation and a halogen cont~ining a complex
anion of a metal or metalloid. Other cationic curing agents include a salt having an
organometallic complex cation and a halogen cont~ining complex anion of a metal or
0 metalloid. Such curing agents are known in the art and are exemplified by U.S. Patent
4,751,138 (Tumey et al.) (especially column 6, line 65 to column 9, line 45). Another
example known in the art is an organometallic salt and an onium salt as exemplified by
U.S. Patent 4,985,340 (Palazzotto) (especially column 4, line 65 to column 14, line 50)
and European Patent Applications 306,161 (Brown-Wensley et al.) and 306,162
15 (Palazzotto et al.). Still other cationic curing agents known in the art include an ionic
salt of an organometallic complex in which the metal is selected from the elements of
Periodic Group IVB, VB, VIB, VIIB and VIIIB which is described in European Patent
Application 109,851 (Palazzotto et al.).
Regarding free radical curable resins, in some instances it is preferred that the
abrasive slurry further comprise a free radical curing agent. However in the case of an
electron beam energy source, the curing agent is not always required because theelectron beam itself generates free radicals.
Examples of free radical thermal initiators include peroxides, e.g., benzoyl
peroxide, azo compounds, benzophenones, and quinones. For either ultraviolet or
visible light energy source, this curing agent is sometimes referred to as a
photoinitiator. Examples of initiators, that when exposed to ultraviolet light generate a
free radical source, include but are not limited to those selected from the group
con~i~tinp; of organic peroxides, azo compounds, quinones, benzophenones, nitroso
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compounds, acryl halides, hydrozones, ~,-elcal Lo compounds, pyrylium compounds,triacrylimi~ oles, bi~imi~ oles, chloroalkyL~ s~ benzoin ethers, benzil ketals,
thioxanthones, and acetophenone derivatives, and mixtures thereof. A p-ere- ~ ~dphotoinitiator for use with ultraviolet radiation is 2,2-dimethoxy- 1 ,2-dephenyl- 1-
5 ethanone. Examples of initiators known in the art that generate a free radical sourcewhen exposed to visible radiation can be found in U.S. Patent No. 4,735,632, (Oxman
et al.). A preferred initiator for use with visible light is "Irgacure 369" commercially
available from Ciba Geigy Corporation.
0 Additives
The abrasive slurry to make the abrasive coating can further comprise optional
additives, such as, for example, fillers (inc~ ing grinding aids), fibers, lubricants,
wetting agents, thixoprotic materials, surfactants, pigments, dyes, ~nti~t~tic agents,
coupling agents, release agents, plasticizers, suspending agents, and mixtures thereof.
The amounts of these materials are selected to provide the properties desired. The use
of these can affect the erodability of the abrasive composite. In some instances an
additive is purposely added to make the abrasive composite more erodable, thereby
expelling dulled abrasive particles and exposing new abrasive particles.
The term filler also encompasses materials that are known in the abrasive
industry as grinding aids. A grinding aid is defined as particulate material that the
addition of which has a significant effect on the chemical and physical processes of
abrading which results in improved performance. Examples of chemical groups of
grinding aids include waxes, organic halide compounds, halide salts and metals and
2s their alloys. The organic halide compounds will typically break down during abrading
and release a halogen acid or a gaseous halide compound. Examples of such materials
include chlorinated waxes like tetrachloronaphthalene, pentachloronaphthalene; and
polyvinyl chloride. Examples of halide salts include sodium chloride, potassium
cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroboate, sodiumtetrafluoroborate, silicon fluorides, potassium chloride, m~gnesillm chloride. Examples
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of metals include, tin, lead, bismuth, cobalt, antimony, c~mi--m, iron tit~nj~lm Other
mi~cell~neous grinding aids include sulfilr, organic sulfur compounds, graphite and
metallic sulfides.
Examples of antistatic agents include graphite, carbon black, v~n~ lm oxide,
humectants, and the like. These 5~nti!;;t~tic agents are known in the art and are
exemplified by U.S. Patent Nos. 5,061,294 (Harmer et al.); 5,137,542 (Buchanan et
al.), and 5,203,884 (Bllch~n~n et al.).
A coupling agent can provide an association bridge between the binder
precursor and the filler particles or abrasive particles. The addition of the coupling
agent significantly reduces the coating viscosity of the slurry used to form abrasive
composites. Examples of coupling agents include silanes, titanates, and
zircoaluminates. One example of a suitable silane coupling agent, 3-
methacryloxypropyl-trimethoxysilane, is commercially available from Union Carbide
under the trade designation "A- 174". The abrasive slurry preferably contains anywhere
from about 0.01 to 3% by weight coupling agent
An example of a suspending agent is an amorphous silica particle having a
surface area less than 150 meters square/gram that is commercially available from
DeGussa Corp., under the trade name "OX-50".
It is also within the scope of the present invention to make abrasive composite
particles. In general, the method involves the steps of: a) coating an abrasive slurry
into the cavities of a production tool; b) exposing the abrasive slurry to conditions to
solidify the binder precursor, form a binder, and forrn abrasive composites; c)
removing the abrasive composites form the production tool; and d) converting theabrasive composites into composite particles. These abrasive composite particles can
- be used in bonded abrasives, coated abrasives, and nonwoven abrasives. This method
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is described in greater detail in PCT WO 95/01241, the entire disclosure of which is
incorporated herein by l~;;rc;-c'~ce.
The operation of the present invention will be further described with regard to
5 the following detailed examples. These examples are offered to further illustrate the
various specific and pl ere. led embodiments and techniques. It should be understood,
however, that many variations and modifications may be made while rem~ining within
the scope of the present invention.
10 EXAMPLE I
Knurlin~ Process
An eight inch diameter, 28 inch long, 1026 mild steel workpiece was first
plated with a thin layer of bright nickel to prevent corrosion and improve adhesion to
plated copper. Next, 0.050 in. of hard copper, 240 knoop, was plated over the bright
nickel. One end of the plated workpiece was mounted in a four jaw chuck and the
other end supported with a center in the tail stock of a Clausing engine lathe equipped
with a low pressure pump and water-based coolant. The workpiece outer surface was
faced offsmooth, leaving 0.030 in. of hard copper.
A Zeus Cut-Knurling Tool Model N0. ''09 was provided with a high speed
steel ("HSS") first knurling wheel 12'. First knurling wheel had a 30~ left tooth incline~
36 teeth per inch ("TPI"), with the teeth having a 90~ inc!~lded angle at the tooth ridge.
The tool was also provided with a HSS second knurling wheel 14. The second
knurling wheel had a 0~ tooth incline angle, 36 TPI, with a 90~ included angle at the
tooth ridge. Both wheel orientations were adjusted by setting the wheel mountingposts to the 200 mm (7.9 inch) workpiece O. D. position. The wheel axis were each
approximately 30~ relative to the tool center plane 24. The Cut-Knurling Tool was
then mounted on the cross slide of the lathe. The height of the tool was adjusted so
that both wheels would contact the workpiece at the same time. The top wheel 12'
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was then removed. Coolant flow was directed at the second wheel 14 to wash away
chips as they formed.
1) Second wheel 14 was çn~çd with the workpiece. The lathe rotated the
workpiece in direction A' at 80 rpm with a tool feed rate in direction B of 0.010
inch/revolution from right to left. The depth of cut of the first wheel 14 was adjusted
to give about 75% of a full knurl.
2) The second wheel 14 was then removed and the first wheel 12' was
reinstalled. The lathe rotated the workpiece in direction A at the same conditions as
o above with tool direction B from right to left.
3) The first wheel 12' was removed, and second wheel 14 was reinstalled.
This third step repeated the first step, except the tool was adjusted to provide full knurl
depth.
4) The second wheel 14 was removed, and first wheel 12' was reinstalled.
This fourth step repeated the second step, except the tool was adjusted to provide full
knurl depth.
5) The first wheel 12' was removed and the second wheel 14 was reinstalled.
This fifth step repeated the third step again at full knurl depth.
The resulting knurled workpiece surface was covered with a knurl pattern of
36.7 square-based pyramids per inch measured in the direction parallel to an edge of
the base of the pyramid, having an average height of 0.0099 inches. The tops of the
pyramids were rounded corresponding to the rounded valley of the knurl wheels. The
peaks ofthe pyramidal pattern had a 11.5~ helix angle with respect to a plane
25 perpendicular to the longit~ltlin~l axis of the workpiece. The workpiece was coated
with a protective layer of electroless nickel to prevent corrosion and improve polymer
release characteristics before use.
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Production Tool
The workpiece was used to make production tooling by the process shown in
Figure 23. First the wc"k~,icce was installed at 30. The workpiece, or master tool was
held at 60~C (140~F) and roll 102 at 21~C (70~F). Escorene Polypropylene 3445 at214~C (417~F) was extruded on to the master tool. A 0.022 inch thick seamless film
was collected at 3.6 meters/minute (11.8 fpm). The surface of the film had an
uninterrupted pattern of pyramidal pockets on its surface which were the inverse of
those on the knurled workpiece.
lo Abrasive Article
An abrasive article was prepared using the process illustrated in Figure 25. Theproduction tool was installed as component 82 with the pockets on side 86. The
substrate 112 was an X weight poly cotton. It had a latex/phenolic resin treatment
(85 parts/15 parts based upon cured resin) on the front side 113.
A radiation curable precursor was prepared by mixing components in the
following table with a high shear mixer until all agglomerated solids have dispersed.
Component Wt percent
Trimethvlol propane triacrylate 39.54
Triacrylate oftris(hydroxyethyl) isocyanurate 16.95
Potassium tetrafluoroborate, 98% pure micropulverized 38.97
Amorphous silica, Degussa OX-50 1.99
Silane coupling agent, Union Carbide A-174 1.99
Irgacure 369, Ciba Geigy Corp. 0.56
Next, a radiation curable abrasive slurry was prepared by mixing 41.5 wt
percent ofthe above precursor with 58.5 wt percent of grade 180 BT-R available from
U.S. Electrofused Minerals, lnc., Baltimore Maryland, for 20 minlltes at 1200 rpm in a
high shear mixer.
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The abrasive slurry was coated into the pockets of the production tool using a
knife coater, 118, with a 51 micrometer (2 mils) gap. The radiation source was two
visible lamps each op~l~Lil~g at 600 watts/inch. The process was run at 15
meters/minute (50 feet/minute). The abrasive article was removed from the apparatus
of Figure 25 and heated for 12 hours at 115~C (240~F) to fully cure the latex/phenolic
backing tre~mçnt
The structured abrasive was converted to a 7.6 cm (3 inch) by 335 cm (132
inch) endless belt and tested on a 304 stainless steel test piece on a back.ct~nc~ grinder.
o No scribing or groove pattern was observed in the surface of the abraded surface of
the test piece.
EXAMPLE 2
Knurlin~ Process
An eight inch diameter, 28 inch long steel workpiece was plated to provide a
0.060 inch layer of soft copper on its surface. The workpiece was mounted in a four
jaw chuck and the other end supported with a center in the tail stock of a Lodge and
Shipley engine lathe equipped with a low pressure pump and water-based coolant. The
2() workpiece outer surface was faced-off smooth~ leaving 0.015 inch of the soft copper
A Dorian CNC-107-100-3M knurling tool was fitted with two cobalt chrome cut
knurling wheels, 50 TPI, tooth ridge included angle of 90~. The tooth inchne angle of
each wheel was 0~. The mounting posts ofthe knurling tool oriented the first wheel 12
at angle (a) 43~ and the second wheel 14 at -47~ with respect to the center plane 24 of
the workpiece, thus having tooth included angle offset (g) of 2~. The knurling tool
was mounted on the cross side of the lathe. The tool shank was checked to make sure
~ it was perpendicular to the workpiece. The second wheel 14 was removed. Coolant
flow was directed at the wheel to wash away chips as they forrned.
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1) The lathe was run in direction A at 66 rpm, with the tool feed rate of 0.010
inch/rev in direction B from left to right. The depth of cut of first wheel 12 was
adjusted to get full depth. The wheel produced 1.5 inch long chips.
2) The first wheel 12 was removed and reinstalled in the position of second
wheel 14. The lathe was run in direction A' at 66 rpm, with the tool feed rate of 0.010
inch/rev in direction B from left to right. The depth of cut was adjusted to get full
depth. E~min~tion of the workpiece showed burring and deformation in the first
plurality of grooves.
3) The wheel was removed from the second position and reinstalled in the first
o position. A third cleaning pass was made down the first plurality of grooves at the
same depth as the initial cut. The wheel tracked well. Inspection showed that the
burring and deformation was removed from the first plurality of grooves leaving sharp-
edged, well defined pyramids. Only slight periodic burring was evident in the second
plurality of grooves.
The resulting workpiece had an array of 50 square-based pyramids/inch
measured in the direction parallel to en edge of the base of the pyramid, having an
average height of 0.0094 inches. The peaks had a 1.1~ helix angle with respect to a
plane perpendicular to the longitudinal axis of the workpiece. The workpiece wascoated with a protective layer of electroless nickel to prevent corrosion and improve
polymer release characteristics before use.
Production Tool
The workpiece was used to make a production tool by the process shown in
Figure 23. First the workpiece was installed at 30. The workpiece, or master tool was
held at 60~C (140~F) and roll 102 at 21~C (70~F). Escorene Polypropylene 3445 at214~C (417~F) was extruded on to the master tool. A 0.022 inch thick seamless film
was collected at 3.6 meters/minute (11.8 fpm). The surface ofthe film had pyramidal
pockets on its surface which were the inverse of those on the knurled workpiece.
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Abrasive Article
An abrasive article was p,til)a,ed using the process shown in Figure 26. An
endless belt of the production tooling was prepared by ultrasonically welding. This
belt was installed as component 82 with the pockets on side 86. The substrate 142
s was a J weight rayon. It had a latex/phenolic resin treatment (85 parts/15 parts based
upon cured resin) on side 143. An abrasive article was produced as described in
Example 1, except that the abrasive slurry was made using P-320 F7TX mineral from
H. C. Stark, Inc., Newton, M~cs~chllsettc
lo The abrasive slurry was coated into the pockets of the production tool using a
knife coater, 146, with a 76 micrometer (3 mils) gap. The radiation source was one
visible lamp operating at 600 watts/inch. The process was run at 15 meters/minute (50
feet/minute). The abrasive article was removed from the apparatus of Figure 26 and
heated for 12 hours at 115~C (240~F) to fully cure the latex/phenolic backing
15 treatment.
The coated abrasive was converted to a 7.6 cm (3 inch) b~ 335 cm (13'' inch)
endless belt and tested on a 304 stainless steel test piece on a bacl;stand grinder A
ripple or scribe pattern with 0.020 inch spacin~ ~ as imparted on the surface of the test
20 piece. The helix angle of this sample was not sufficient to prevent scribing of the test
piece by the tips of the pyramids on the structured abrasive.
~XAMPLE 3
Knurlin~ Process
An eight inch tli~met~r, 28 inch long, 1026 mild steel roll was mounted in a
four jaw chuck and the other end supported with a center in the tail stock of a Lodge
and Shipley engine lathe equipped with a low pressure pump and water-based coolant.
~ A Zeus Cut-Knurling Tool Model N0. 209 was provided with a HSS first knurling
30 wheel 12'. The first wheel 12' had a tooth incline angle of 30~ left, 25 TPI, and a 90~
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in~ ded angle at the tooth ridge. The HSS second knurling wheel 14 had a tooth
incline angle of 0~, 25 TPI, and a 90~ tooth ridge in~ ded angle. The wheel mounting
posts were adjusted to 200 mm (7.9 inch) ~o,h~,;cce O.D. After mounting the Cut-Knurling tool and adjusting it for height, the first cutting wheel 12' was removed.
5 Coolant flow was directed at the wheel to wash away chips as they formed.
1) The lathe was run in direction A' at 77 rpm, with a tool feed rate of 0.010
inch/revolution from right to left. The depth of cut of the second wheel 14 was
adjusted to give about 75% of a full knurl.
lo 2) The second wheel 14 was then removed and the first wheel 12' was
reinstalled. The lathe was run in direction A at the same conditions as step one, with
the same tool advance as step one.
3) The first wheel 12' was removed and second wheel 14 was reinstalled. This
third step repeated the first step, except the knurling wheel was adjusted to full knurl
15 depth.
4) The second wheel 14 was removed and the first wheel 12' was reinstalled.
This fourth step repeated the second step except the knurling wheel was adjusted to
full knurl depth.
5) The first wheel 12' was removed and the second wheel 14 was reinstalled
20 This fifth step repeated the third step at full knurl depth.
The resulting knurled workpiece surface had sharp, well-formed square-based
pyramids with an average height of 0.0141 inches. The pyramid peaks had an 11.5~helix angle with respect to a plane perpendicular to the lonf~it~l-lin~l axis of the
2s workpiece. The workpiece was coated with a protective layer of electroless nickel to
prevent corrosion and improve polymer release characteristics before use.
Production Tool and Abrasive Article
The knurled workpiece was used to produce 0.024 inch thick production tool
30 by the process described in Example l. This production tool was used to make a
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coated abrasive using the process illustrated in Figure 25. The substrate 1 ' 2 was an X
weight poly cotton with the same latexlphenolic resin tre~tm~ont as Example 1. The
abrasive slurry was forrn~ ted from 40.20% radiation curable precursor and 59.80%
grade 150 BT-R available from U.S. Electrofused Minerals, Inc., Baltimore Maryland.
The slurry was coated into the pockets of the production tool using a knife
coater 1 18 with a 51 micrometer (2 mil) gap. The radiation source was two visible
lamps operating at 600 watts/inch each. The process was run at 30 meters/minute
( 100 feet/minute). The abrasive article was removed from the apparatus of Figure 25
and heated for 12 hours at l 1 5~C (240~F) to fully cure the latex/phenolic backing
treatment.
The coated abrasive was converted to a 7.6 cm (3 inch) by 335 cm (132 inch)
endless belt. The abrasive article was tested on a 304 stainless steel test piece on a
15 backstand grinder. No groove or scribe pattern was observed in the abraded surface of
the test piece.
The present invention has now been described with reference to several
embodiments thereof. The foregoing detailed description and examples have been
20 given for clarity of understanding only. No unnecessary limitations are to beunderstood therefrom. It will be apparent to those skilled in the art that many changes
can be made in the embodiments described without departing from the scope of theinvention. Thus, the scope of the present invention should not be limited to the exact
details and structures described herein, but rather by the structures described by the
25 l~n~l~ge of the claims, and the equivalents of those structures.
