U.S. patent application number 09/821611 was filed with the patent office on 2001-10-18 for method and apparatus for knurling a workpiece, method of molding an article with such workpiece, and such molded article.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Hoopman, Timothy L..
Application Number | 20010029770 09/821611 |
Document ID | / |
Family ID | 25449379 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029770 |
Kind Code |
A1 |
Hoopman, Timothy L. |
October 18, 2001 |
Method and apparatus for knurling a workpiece, method of molding an
article with such workpiece, and such molded article
Abstract
A method and apparatus for knurling a workpiece in which the
knurl pattern includes grooves of at least two different
configurations. The apparatus includes a knurl wheel holder that
allows angular rotation of the knurl wheel about the holder
longitudinal axis while maintaining the knurl wheel point of
contact on the longitudinal axis. The apparatus also includes a
knurling wheel that includes teeth of at least two different
configurations. Also disclosed is a method of molding a molded
article with the knurled workpiece to impart the inverse of the
knurl pattern onto the molded article, such a molded article, a
method of forming a structured abrasive article with the molded
article, and such an abrasive article.
Inventors: |
Hoopman, Timothy L.; (River
Falls, WI) |
Correspondence
Address: |
Office of Intellectual Property Counsel
3M Innovative Properties Company
PO Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
25449379 |
Appl. No.: |
09/821611 |
Filed: |
March 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09821611 |
Mar 29, 2001 |
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09385785 |
Aug 30, 1999 |
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6238611 |
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09385785 |
Aug 30, 1999 |
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08923862 |
Sep 3, 1997 |
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5946991 |
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Current U.S.
Class: |
72/703 ; 407/120;
82/1.11; 82/101 |
Current CPC
Class: |
B24D 11/008 20130101;
Y10T 82/16 20150115; Y10T 82/16967 20150115; Y10T 82/2585 20150115;
Y10T 407/28 20150115; Y10T 82/16114 20150115; Y10T 82/2591
20150115; Y10S 29/023 20130101; Y10T 82/10 20150115; Y10S 72/703
20130101 |
Class at
Publication: |
72/703 ; 82/1.11;
82/101; 407/120 |
International
Class: |
B21C 001/00 |
Claims
What is claimed is:
1. A method of knurling a cylindrical surface of a workpiece, the
workpiece having a longitudinal axis, the method comprising the
steps of: a) imparting a first plurality of grooves to a workpiece,
wherein the first plurality of grooves has a first helix angle with
respect to the longitudinal axis of the workpiece; wherein the
first plurality of grooves includes a first groove and a second
groove, the second groove being of substantially different
configuration from the first groove; and b) imparting a second
plurality of grooves to the workpiece, wherein the second plurality
of grooves has a second helix angle with respect to the
longitudinal axis, the second plurality of grooves intersecting the
first plurality of grooves, thereby imparting a knurl pattern to
the outer surface of the workpiece.
2. The method of claim 1, wherein the second plurality of grooves
includes a third groove and a fourth groove, the fourth groove
being of substantially different configuration from the third
groove.
3. The method of claim 1, wherein the first and second grooves each
comprise a first groove surface, a second groove surface, and a
groove base, wherein the first and second groove surfaces each
extend from an outer surface of the workpiece to the groove base,
and wherein the groove surfaces of the first groove are at a first
included angle to one another, wherein the surfaces of the second
groove are at a second included angle to one another, and wherein
the second included angle is substantially different from the first
included angle.
4. The method of claim 3, wherein the first and second included
angles differ by at least 3 degrees.
5. The method of claim 4, wherein the first and second included
angles differ by at least 10 degrees.
6. The method of claim 2, wherein the third and fourth grooves each
comprise a first groove surface, a second groove surface, and a
groove base, wherein the first and second groove surfaces each
extend from an outer surface of the workpiece to the groove base,
and wherein groove surfaces of the third groove are at a third
included angle to one another, wherein the surfaces of the fourth
groove are at a fourth included angle to one another, and wherein
the fourth included angle is substantially different from the third
included angle.
7. The method of claim 6, wherein the third and fourth included
angles differ by at least 3 degrees.
8. The method of claim 7, wherein the third and fourth included
angles differ by at least 10 degrees.
9. The method of claim 3, wherein the groove base is a line formed
at the juncture of the first and second groove surfaces.
10. The method of claim 1, wherein the intersection of the first
plurality of grooves and second plurality of grooves thereby forms
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, and wherein the plurality of pyramids includes a
first pyramid and a second pyramid, the second pyramid being of
substantially different configuration from the first pyramid.
11. The method of claim 10, wherein the opposed first sides of the
first pyramid form a first angle therebetween, and wherein the
opposed first surfaces of the second pyramid form a second angle
therebetween, and wherein the second angle is at least 3 degrees
different from the first angle.
12. The method of claim 11, wherein the second angle is at least 10
degrees different from the first angle.
13. The method of claim 10, wherein the pyramids are truncated
pyramids.
14. The method of claim 1, wherein the pattern is continuous and
uninterrupted around the circumference of the workpiece.
15. The method of claim 1, wherein the first and second groove
helix angles are of substantially unequal magnitude.
16. A knurled workpiece made according to the method of claim
1.
17. A method of molding a molded article with a knurled workpiece
according to claim 16, comprising 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
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 from the workpiece.
18. A molded article made in accordance with the method of claim
17.
19. A knurled workpiece having a knurled, cylindrical outer
surface, the knurled workpiece comprising: a cylindrical body
having a longitudinal 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 a first helix angle with respect to
said longitudinal axis of said workpiece; said first plurality of
grooves including a first groove and a second groove, said second
groove being of a substantially different configuration from said
first groove; and a second plurality of grooves, said second
plurality of grooves having a second helix angle with respect to
said longitudinal axis, said second plurality of grooves
intersecting said first plurality of grooves.
20. The knurled workpiece of claim 19, wherein said second
plurality of grooves includes a third groove and a fourth groove,
said fourth groove being of a substantially different configuration
from said third groove.
21. The knurled workpiece of claim 19, wherein said first and
second grooves each comprise a first groove surface, a second
groove surface, and a groove base, wherein said first and second
groove surfaces each extend from said workpiece outer surface to
said groove base, and wherein said groove surfaces of said first
groove are at a first included angle to one another and wherein
said groove surfaces of said second groove are at a second included
angle to one another, said second included angle being
substantially different from said first included angle.
22. The knurled workpiece of claim 21, wherein said first and
second included angles differ by at least 3 degrees.
23. The knurled workpiece of claim 21, wherein said first and
second included angles differ by at least 10 degrees.
24. The knurled workpiece of claim 20, wherein said third and
fourth grooves each comprise a first groove surface, a second
groove surface, and a groove base, wherein said first and second
groove surfaces each extend from said workpiece outer surface to
said groove base, wherein said groove surfaces of said third groove
are at a third included angle to one another and wherein said
groove surfaces of said fourth groove are at a fourth included
angle to one another, said fourth included angle being
substantially different from said third included angle.
25. The knurled workpiece of claim 24, wherein said third and
fourth included angles differ by at least 3 degrees.
26. The knurled workpiece of claim 24, wherein said third and
fourth included angles differ by at least 10 degrees.
27. The knurled workpiece of claim 21, wherein said groove base is
a line formed at the juncture of said first and second groove
surfaces.
28. The knurled workpiece of claim 21, wherein the intersection of
said first plurality of grooves and said second plurality of
grooves thereby forms a plurality of pyramids on said workpiece
outer surface, each of said pyramids including first opposed side
surfaces formed by said first grooves and second opposed side
surfaces formed by said second grooves, and wherein said plurality
of pyramids includes a first pyramid and a second pyramid, said
second pyramid being of substantially different configuration from
said first pyramid.
29. The knurled workpiece of claim 28, wherein said opposed first
sides of said first pyramid form a first angle therebetween, and
wherein said opposed first surfaces of said second pyramid form a
second angle therebetween, and wherein said second angle is at
least 3 degrees different from the first angle.
30. The knurled workpiece of claim 29, wherein said second angle is
at least 10 degrees different from said first angle.
31. The knurled workpiece of claim 29, wherein the pyramids are
truncated pyramids.
32. The knurled workpiece of claim 19, wherein said knurl pattern
is continuous and uninterrupted around the circumference of said
workpiece.
33. A method of molding a molded article with the knurled workpiece
of claim 19, comprising 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,
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 moldable material in contact
with the knurled workpiece; and c) removing the moldable material
from the knurled workpiece.
34. A molded article made in accordance with the method of claim
33.
35. An apparatus for holding a cutting knurl wheel, comprising: a
main support body; a shaft including a first end, a second end, and
a longitudinal axis, wherein said shaft is rotatably mounted in
said main body so as to rotate about said longitudinal axis; a
knurl wheel mount on the second end of said shaft; a knurl wheel
rotatably mounted on said knurl wheel mount so as to rotate about
an knurl wheel axis, said knurl wheel including a plurality of
teeth on an outer periphery thereof; wherein said knurl wheel axis
intersects said shaft longitudinal axis at an oblique angle;
whereby rotation of said knurl wheel about said knurl wheel axis
defines a distal point that is the location furthest in the
direction from said first end of said shaft to said second end of
said shaft through which said knurl teeth pass, said distal point
being on said shaft longitudinal axis; and wherein said knurl wheel
mount and knurl wheel are configured such that said distal point
remains located on said shaft longitudinal axis during rotation of
said shaft about said longitudinal axis.
36. An apparatus as in claim 35, wherein said shaft longitudinal
axis and said knurl wheel axis intersect at an angle of from 80 to
87 degrees.
37. A knurl wheel, comprising a body including first and second
major opposed surfaces and an outer peripheral surface between said
first and second major surfaces; and a plurality of teeth on said
outer peripheral surface, said plurality of teeth including a first
tooth and a second tooth, said second tooth being of substantially
different configuration from said first tooth.
38. The knurl wheel of claim 37, wherein said first tooth includes
first and second sides extending from said outer peripheral
surface, said first and second sides forming a first included angle
therebetween, and wherein said second tooth includes third and
fourth sides extending from said outer peripheral surface and
defining a second included angle therebetween, said second angle
being substantially different from said first angle.
39. The knurl wheel of claim 38, wherein said second angle differs
from said first angle by at least 3 degrees.
40. The knurl wheel of claim 39, wherein said second angle differs
from said first angle by at least 10 degrees.
41. The knurl wheel of claim 37, wherein each of said plurality of
teeth have a substantially different configuration.
42. The knurl wheel of claim 37, wherein each of said teeth
includes a first side and a second side extending from said outer
peripheral surface; wherein a respective first edge of one of said
teeth and a respective second edge of an adjacent one of said teeth
form an included angle therebetween, thereby forming a plurality of
included angles between each adjacent pair of teeth; and wherein a
first one of said included angles is substantially different from a
second one of said included angles.
43. The knurl wheel of claim 42, wherein said first included angle
differs from said second included angle by at least 3 degrees.
44. The knurl wheel of claim 42, wherein said first included angle
differs from said second included angle by at least 10 degrees.
45. The knurl wheel of claim 42, wherein each of said included
angles is substantially different.
Description
[0001] This is a divisional of application Ser. No. 08/923,862,
filed Sep. 3, 1997.
TECHNICAL FIELD
[0002] The present invention relates to a method and apparatus for
knurling a pattern having two or more different configurations of
grooves in a workpiece, and an article molded with the knurled
workpiece. Such a molded article is useful for making an abrasive
article in which a structured abrasive coating is provided on a
substrate, among many other uses.
BACKGROUND OF THE INVENTION
[0003] 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 knurling is done by pressing a
knurling wheel against a workpiece with sufficient force to
plastically deform the outer surface of the workpiece. The 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. Cutting knurl holders and cutting knurl wheels are available
from Dorian Tool International, Houston, Tex. Zeus brand cutting
knurl tools are available from Eagle Rock Technologies Into Corp.
of Bath, Pa.
[0004] In form knurling, the rotational axis of the knurl wheel is
parallel to the rotational axis of the cylindrical workpiece.
Therefore, the helix angle of the grooves formed on the roll is
defined by the helix angle of the teeth on the knurl wheel. For cut
knurling, the rotational axis of the cutting knurl wheel is tilted
with respect to the rotational axis of the cylindrical workpiece
("the tilt angle") to define the helix angle and to produce the
cutting action. Because the edge of the knurl wheel is being used
as a cutting tool, it is necessary to provide a clearance angle.
This is achieved by positioning the knurl wheel so that at the
point of contact of the knurl wheel and workpiece surface, the
toothed cylindrical surface of the knurl wheel and the workpiece
surface form an angle of 3 to 10 degrees.
[0005] In both of the above types of knurling processes, the
structure generated in the workpiece is a plurality of continuous
grooves having a cross-section similar to the shape of the teeth on
the knurl wheel. Both conventional knurling processes typically
impart a diamond-based pattern which is the result of the
intersection of two sets of continuous grooves, the two sets having
opposite and equal helix angles (one having a left hand ("LH")
helix and one having a right hand ("RH") helix) relative to a
cylindrical workpiece. The intersection of the two sets of grooves
creates a diamond pattern in the outer surface of the workpiece.
The diamonds are aligned in the direction perpendicular to the
longitudinal axis of the cylindrical workpiece, and are all
substantially identical to one another. Conventional knurling
processes have also been used to impart a square-based pattern, in
which the squares are oriented to have their sides at 45.degree. 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 longitudinal axis of the cylindrical
workpiece, and all of the square-based pyramids are identical.
These processes are typically used to impart a non-slip pattern on
a tool handle, machine control knob, or the like.
[0006] In common commercially available cut knurling holders, the
knurl wheel tilt angle is fixed at .+-.30.degree. relative to the
rotational axis of the cylindrical workpiece. Holders providing a
.+-.45.degree. knurl wheel tilt angles are also available. Knurl
wheels with teeth having helix angles relative to the rotational
axis of the wheel of 0.degree., 15.degree. RH, 30.degree. RH,
15.degree. LH and 30.degree. LH are readily available. The sum of
the tilt angle and the tooth helix angle defines the groove helix
angle in the workpiece. The permutations of arithmetic sums of
these wheel axis tilt angles and knurl teeth helix angles can
produce groove helix angles on the cylindrical workpiece surface at
0.degree., 15.degree., 30.degree., 45.degree., 60.degree. and
75.degree. RH or LH to the workpiece rotational axis. If a groove
helix angle on the workpiece surface other than these angles is
desired, a special knurl wheel and/or knurl holder must be
fabricated.
[0007] WIPO International Patent Application Publication Number WO
97/12727, published on Apr. 10, 1997, "Method and Apparatus for
Knurling a Workpiece, Method of Molding an Article With Such
Workpiece, and Such Molded Article," Hoopman et al., discloses a
method and apparatus for knurling a workpiece in which the two sets
of intersecting grooves each have a helix angle of unequal
magnitude and opposite direction. The resulting knurl pattern is
therefore not aligned in the cylindrical direction of the
workpiece. Hoopman et al. also discloses a method of molding a
molded article with the knurled workpiece to impart the inverse of
the knurl pattern onto the molded article, and a method of forming
a structured abrasive article with the molded article. The
structured abrasive coating comprises abrasive particles and a
binder in the form of a precise, three dimensional abrasive
composites molded onto the substrate.
[0008] Other structured abrasives, and methods and apparatuses for
making such structured abrasives, are described in U.S. Pat. No.
5,152,917, "Structured Abrasive Article," (Pieper et al.), issued
Oct. 6, 1992, the entire disclosure of which is incorporated herein
by reference.
[0009] WIPO International Patent Application Publication Number WO
95/07797, "Abrasive Article, Method of Manufacture of Same, Method
of Using Same for Finishing, And a Production Tool," (Hoopman et
al.), published Mar. 23, 1995, discloses a structured abrasive
article in which the abrasive composites are not all identical.
Hoopman et al. provides differing dimensioned shapes, among other
things, in the array of abrasive composites. A copy of a desired
pattern of variably dimensioned shapes of abrasive composites can
be formed in the surface of a so-called metal master, e.g.,
aluminum, copper, bronze, or a plastic master such as acrylic
plastic, either of which can be nickel-plated after grooving, as by
diamond turning grooves to leave upraised portions corresponding to
the desired predetermined shapes of the abrasive composites. Then,
flexible plastic production tooling can be formed, in general, from
the master by a method explained in U.S. Pat. No. 5,152,917 (Pieper
et al.).
[0010] Other examples of structured abrasives and methods and
apparatuses for their manufacture are disclosed in U.S. Pat. No.
5,435,816, "Method of Making an Abrasive Article," (Spurgeon et
al.), issued Jul. 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. Spurgeon et al. teaches that, in addition to other
procedures, a thermoplastic production tool can be made according
to the following 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 machining, etc. The master tool should have the inverse of
the pattern for the production tool on the surface thereof. The
thermoplastic material can be embossed with the master tool to form
the pattern. While Spurgeon et al. 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.
[0011] Thus it is seen that there is a need for a knurling
apparatus and method that allows the knurl wheel to be held at any
desired angle relative to the rotational axis of a cylindrical
workpiece. There is also a need to provide a knurling apparatus and
method in which the knurling pattern in the workpiece comprises
groove structures of at least two different configurations.
SUMMARY OF THE INVENTION
[0012] One aspect of the present invention provides a method of
knurling a cylindrical surface of a workpiece, the workpiece having
a longitudinal axis. The method comprises the steps of: a)
imparting a first plurality of grooves to a workpiece, wherein the
first plurality of grooves has a first helix angle with respect to
the longitudinal axis of the workpiece; wherein the first plurality
of grooves includes a first groove and a second groove, the second
groove being of substantially different configuration from the
first groove; and b) imparting a second plurality of grooves to the
workpiece, wherein the second plurality of grooves has a second
helix angle with respect to the longitudinal axis. The second
plurality of grooves intersects the first plurality of grooves,
thereby imparting a knurl pattern to the outer surface of the
workpiece.
[0013] In one preferred embodiment of the above method, the second
plurality of grooves includes a third groove and a fourth groove,
the fourth groove being of substantially different configuration
from the third groove. In one preferred version of this embodiment,
the third and fourth grooves each comprise a first groove surface,
a second groove surface, and a groove base. The first and second
groove surfaces each extend from an outer surface of the workpiece
to the groove base. The groove surfaces of the third groove are at
a third included angle to one another, the surfaces of the fourth
groove are at a fourth included angle to one another, and the
fourth included angle is substantially different from the third
included angle. In one preferred embodiment, the third and fourth
included angles differ by at least 3 degrees. In another preferred
embodiment, the third and fourth included angles differ by at least
10 degrees.
[0014] In another preferred embodiment of the above method, the
first and second grooves each comprise a first groove surface, a
second groove surface, and a groove base. The first and second
groove surfaces each extend from an outer surface of the workpiece
to the groove base. The groove surfaces of the first groove are at
a first included angle to one another, and the surfaces of the
second groove are at a second included angle to one another. The
second included angle is substantially different from the first
included angle. In one preferred version of this embodiment, the
first and second included angles differ by at least 3 degrees. In
another preferred version of this embodiment, the first and second
included angles differ by at least 10 degrees. In another preferred
version of this embodiment, the groove base is a line formed at the
juncture of the first and second groove surfaces.
[0015] In yet another preferred embodiment of the above method, the
intersection of the first plurality of grooves and second plurality
of grooves forms a plurality of pyramids on the outer surface of
the workpiece. Each of said pyramids includes first opposed side
surfaces formed by the first grooves and second opposed side
surfaces formed by the second grooves. The plurality of pyramids
includes a first pyramid and a second pyramid, the second pyramid
being of substantially different configuration from the first
pyramid. In one preferred embodiment, the opposed first sides of
the first pyramid form a first angle therebetween, the opposed
first surfaces of the second pyramid form a second angle
therebetween, and the second angle is at least 3 degrees different
from the first angle. In another preferred embodiment, the second
angle is at least 10 degrees different from the first angle. In
another preferred embodiment, the pyramids are truncated
pyramids.
[0016] In still another preferred embodiment of the above method,
the pattern is continuous and uninterrupted around the
circumference of the workpiece.
[0017] In still another preferred embodiment of the above method,
the first and second groove helix angles are of substantially
unequal magnitude.
[0018] Another aspect of the present invention provides a knurled
workpiece made according to the above method.
[0019] Yet another aspect of the present invention provides a
method of molding a molded article with the just-described knurled
workpiece. This method 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
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 from the workpiece.
[0020] In yet another aspect, the present invention provides a
molded article made in accordance with the just-described
method.
[0021] The present invention also provides a knurled workpiece
having a knurled, cylindrical outer surface. The knurled workpiece
comprises: a cylindrical body having a longitudinal axis and an
outer cylindrical surface, the outer surface having a knurl pattern
thereon. The knurl pattern comprises a first plurality of grooves
having a first helix angle with respect to the longitudinal axis of
said workpiece. The first plurality of grooves includes a first
groove and a second groove, the second groove being of a
substantially different configuration from said first groove. The
knurl pattern also comprises a second plurality of grooves. The
second plurality of grooves has a second helix angle with respect
to the longitudinal axis. The second plurality of grooves
intersects the first plurality of grooves.
[0022] In one preferred embodiment of the above knurled workpiece,
the second plurality of grooves includes a third groove and a
fourth groove, the fourth groove being of a substantially different
configuration from the third groove.
[0023] In another preferred embodiment of the above knurled
workpiece, the first and second grooves each comprise a first
groove surface, a second groove surface, and a groove base. The
first and second groove surfaces each extend from the workpiece
outer surface to the groove base. The groove surfaces of the first
groove are at a first included angle to one another and the groove
surfaces of the second groove are at a second included angle to one
another, the second included angle being substantially different
from the first included angle. In one preferred embodiment, the
first and second included angles differ by at least 3 degrees. In
another preferred embodiment, the first and second included angles
differ by at least 10 degrees.
[0024] In another preferred embodiment of the above knurled
workpiece, the third and fourth grooves each comprise a first
groove surface, a second groove surface, and a groove base. The
first and second groove surfaces each extend from the workpiece
outer surface to the groove base. The groove surfaces of the third
groove are at a third included angle to one another and the groove
surfaces of the fourth groove are at a fourth included angle to one
another, the fourth included angle being substantially different
from the third included angle. In one preferred embodiment, the
third and fourth included angles differ by at least 3 degrees. In
another preferred embodiment, the third and fourth included angles
differ by at least 10 degrees.
[0025] In another preferred embodiment of the above knurled
workpiece, the groove base is a line formed at the juncture of the
first and second groove surfaces.
[0026] In another preferred embodiment of the above knurled
workpiece, the intersection of the first plurality of grooves and
the second plurality of grooves forms a plurality of pyramids on
the workpiece outer surface. Each of the pyramids includes first
opposed side surfaces formed by the first grooves and second
opposed side surfaces formed by the second grooves. The plurality
of pyramids includes a first pyramid and a second pyramid, the
second pyramid being of substantially different configuration from
the first pyramid. In one version of this embodiment, the opposed
first sides of the first pyramid form a first angle therebetween,
and the opposed first surfaces of the second pyramid form a second
angle therebetween, and the second angle is at least 3 degrees
different from the first angle. In one embodiment, the second angle
is at least 10 degrees different from the first angle.
[0027] In another preferred embodiment of the above knurled
workpiece, the pyramids are truncated pyramids.
[0028] In another preferred embodiment of the above knurled
workpiece, the knurl pattern is continuous and uninterrupted around
the circumference of the workpiece.
[0029] In another aspect, the present invention provides a method
of molding a molded article with the above knurled workpiece. The
method comprises the steps of:
[0030] a) applying a moldable material to the outer surface of the
knurled workpiece;
[0031] b) while the moldable material is in contact with the
knurled workpiece, 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 moldable
material in contact with the knurled workpiece; and c) removing the
moldable material from the knurled workpiece.
[0032] In another aspect, the present invention provides a molded
article made in accordance with the just-described method.
[0033] In yet another aspect, the present invention provides an
apparatus for holding a cutting knurl wheel. The apparatus
comprises a main support body; a shaft including a first end, a
second end, and a longitudinal axis, wherein the shaft is rotatably
mounted in the main body so as to rotate about the longitudinal
axis; a knurl wheel mount on the second end of the shaft; a knurl
wheel rotatably mounted on the knurl wheel mount so as to rotate
about a knurl wheel axis, the knurl wheel including a plurality of
teeth on an outer periphery thereof. The knurl wheel axis
intersects the shaft longitudinal axis at an oblique angle.
Rotation of the knurl wheel about the knurl wheel axis defines a
distal point that is the location furthest in the direction from
the first end of the shaft to the second end of the shaft through
which the knurl teeth pass. The distal point is on the shaft
longitudinal axis. The knurl wheel mount and knurl wheel are
configured such that the distal point remains located on the shaft
longitudinal axis during rotation of the shaft about the
longitudinal axis. In one preferred embodiment, the shaft
longitudinal axis and the knurl wheel axis intersect at an angle of
from 80 to 87 degrees.
[0034] In still another aspect, the present invention provides a
knurl wheel. The knurl wheel comprises: a body including first and
second major opposed surfaces and an outer peripheral surface
between the first and second major surfaces; and a plurality of
teeth on the outer peripheral surface. The plurality of teeth
include a first tooth and a second tooth, the second tooth being of
substantially different configuration from the first tooth.
[0035] In one preferred embodiment of the above knurl wheel, the
first tooth includes first and second sides extending from the
outer peripheral surface, the first and second sides forming a
first included angle therebetween. The second tooth includes third
and fourth sides extending from the outer peripheral surface and
defining a second included angle therebetween, the second angle
being substantially different from the first angle. In one
preferred embodiment, the second angle differs from the first angle
by at least 3 degrees. In another preferred embodiment, the second
angle differs from the first angle by at least 10 degrees.
[0036] In another preferred embodiment of the above knurl wheel,
each of the plurality of teeth have a substantially different
configuration.
[0037] In another preferred embodiment of the above knurl wheel,
each of the teeth includes a first side and a second side extending
from the outer peripheral surface. A respective first edge of one
of the teeth and a respective second edge of an adjacent one of the
teeth form an included angle therebetween, thereby forming a
plurality of included angles between each adjacent pair of teeth. A
first one of the included angles is substantially different from a
second one of the included angles. In one preferred embodiment, the
first included angle differs from the second included angle by at
least 3 degrees. In another preferred embodiment, the first
included angle differs from the second included angle by at least
10 degrees. In another preferred embodiment, each of the included
angles is substantially different.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] 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:
[0039] FIG. 1 is an elevational view of a preferred embodiment of a
knurl tool holder of the present invention;
[0040] FIG. 2 is a side elevational view of a knurl mount according
to the present invention, removed from the knurl tool holder of
FIG. 1;
[0041] FIG. 3 is a front elevational view taken in direction 3-3 of
the knurl mount of FIG. 2;
[0042] FIG. 4 is a top plan view taken in direction 4-4 of the
knurl mount of FIG. 2;
[0043] FIG. 5 is a cross-sectional view taken along line 5-5 of the
knurl mount of FIG. 2;
[0044] FIG. 6 is a view like FIG. 5 of the knurl mount having a
knurling wheel 12 mounted thereon, shown in engagement with a
cylindrical workpiece;
[0045] FIG. 7 is a view taken in direction 7-7 of the knurl wheel
and workpiece of FIG. 6, with the knurl mount removed for clarity;
5 FIG. 8 is a view like FIG. 6 of the knurl wheel engaged at an
alternative orientation with the workpiece, with the knurl holder
removed for clarity;
[0046] FIG. 9 is a view taken in direction 9-9 of the knurl wheel
and workpiece of FIG. 8;
[0047] FIG. 10 is a view like FIG. 8 of the knurl wheel engaged at
yet another orientation with the workpiece;
[0048] FIG. 11 is a view taken in direction 11-11 of the knurl
wheel and workpiece of FIG. 10;
[0049] FIG. 12 is a rear elevational view taken in direction 12-12
of the rotational drive assembly portion of the tool holder of FIG.
1;
[0050] FIG. 13 is a side elevational view taken in direction 13-13
of the rotational drive assembly of FIG. 12;
[0051] FIG. 14 is a partial elevational view of one embodiment of a
knurling wheel according to the present invention;
[0052] FIG. 14A is a partial elevational view of an alternate
embodiment of a knurling wheel according to the present
invention;
[0053] FIG. 15 is a partial sectional view taken along line 15-15
of the knurling wheel of FIG. 14;
[0054] FIG. 16 is a partially schematic top view illustrating one
step of a method for knurling a workpiece according to the present
invention;
[0055] FIG. 17 is a view like FIG. 15, showing a second step of the
method according to the present invention;
[0056] FIG. 18 is a plan view of the pattern imparted on the
workpiece by the apparatus and method of the present invention;
[0057] FIG. 19A is a partial cross-sectional view taken along line
19A-19A of the workpiece of FIG. 18;
[0058] FIG. 19B is a partial cross-sectional view taken along line
19B-19B of the workpiece of FIG. 18;
[0059] FIG. 20 is a partially schematic view of an apparatus and
method for making a production tool according to the present
invention;
[0060] FIG. 21 is a plan view of the production tool of FIG.
20;
[0061] FIG. 22 is a partially schematic view of an apparatus and
method for making an abrasive article with the production tool of
the present invention;
[0062] FIG. 23 is a view like FIG. 22 of an alternate embodiment of
an apparatus and method;
[0063] FIG. 24 is a plan view of an abrasive article made in
accordance with the present invention; and
[0064] FIG. 25 is a cross-sectional view taken along line 25-25 of
the abrasive article of FIG. 24.
DETAILED DESCRIPTION OF THE INVENTION
[0065] The present invention provides a knurling tool holder which
holds a knurl wheel at a prescribed clearance angle and allows
infinite adjustment of the angular orientation of the knurl wheel
by rotating the knurl wheel about a holder axis "A" that: 1)
intersects the point of contact of the knurl wheel and the
cylindrical workpiece surface; 2) intersects the longitudinal axis
of the cylindrical workpiece; and 3) is perpendicular to the
longitudinal axis of the workpiece. The clearance angle .beta. is
equal to the compliment of the angle .alpha. between the knurl
wheel rotational axis C and the holder axis A (i.e.,
.beta.=90-.alpha.). As the tool holder rotates the knurl wheel
about tool holder axis, there is virtually no change in clearance
angle, depth of cut or axial position on the workpiece. Only the
helical angle of the generated groove structure is changed. This
allows cutting groove structure helical angles from 15.degree. to
165.degree. (where 0.degree. is parallel to the axis 36 of the
cylindrical workpiece, and where 90.degree. is perpendicular to the
axis of the workpiece thereby providing parallel circumferential
groove structures) using a straight tooth cutter (i.e., the teeth
are parallel to the rotational axis of the knurl wheel). At angles
below 15.degree. approaching 0.degree., the relative cutting
velocities of the workpiece and knurl wheel approaches a pure
rolling, or forming, engagement, and may not provide adequate
cutting results. Therefore, for groove structure helical angles
from 15.degree. to 0.degree., it is preferable to use a knurl wheel
which has negative 30.degree. helical teeth and positioning the
holder at angles which are at 45.degree. to 30.degree. to the roll
axis. The generated structure helical angle is the arithmetic sum
of the holder angle and the knurl wheel tooth angle (i.e.
45.degree.-30.degree.=15.degree.,
37.8.degree.-30.degree.=7.8.degree.,
30.degree.-30.degree.=0.degree. and so on). A similar arrangement
is used for helical angles from 165.degree. to 180.degree.
[0066] Knurl Tool Holder
[0067] A preferred embodiment of a knurl tool holder 10 having a
knurling wheel 12 mounted thereon is illustrated in FIG. 1. Tool
holder 10 includes knurl tool mount 14, spindle 40, and rotational
drive assembly 50. As discussed below in greater detail, operation
of the drive assembly 50 causes the shaft 41 extending through
spindle 40 to rotate, thereby rotating the knurl mount 14 to the
desired angular orientation. The spindle 40, tool mount 14, and
knurl wheel 12 are all sized and configured such that the knurl
wheel rotates about axis A such that the forward-most point "X" on
the knurl wheel 12 rotates about the axis A while remaining on axis
A. Point X on the knurling wheel also extends beyond the front face
19 of knurl mount 14. Furthermore, the tool holder 10 is held in
position relative to the workpiece 30 such that the tool holder
axis A intersects and is perpendicular to the longitudinal axis 36
of the workpiece.
[0068] One suitable embodiment of the spindle 40 is a Gilman Model
40008-X3M-30 spindle, commercially available from Russell T.
Gilman, Inc., of Grafton, Wis. It is understood that any spindle
with sufficient strength and accuracy and that can be fitted with a
knurl mounting fixture would suitable. Spindle 40 includes a shaft
41 rotationally mounted therein. The rotational axis of the shaft
41 defines axis A of the tool holder 10. The drive assembly 50 is
operatively connected to the first end 42 of shaft 41, and knurl
mount 14 is mounted to the second end 43 of the shaft.
[0069] FIGS. 2-5 illustrate knurl mount 14 removed from the holder
10, with knurl wheel 12 removed from the mount 14. One preferred
embodiment of knurl mount 14 is fabricated from a NMTB taper shank
adapter, standard blank number 73, available from Valenite Co., of
Troy, Mich. Knurl mount 14 includes rear portion 15, central
tapered portion 16, and forward portion 17. Tapered portion 16 fits
into a like-shaped cavity on the second end 43 of shaft 41 to help
center the knurl mount 14 relative to the shaft 41. In this manner,
longitudinal axis 20 of the knurl mount 14 is coinident with
rotational axis A of the tool holder 10. A keyway 21 is included on
the rear face 18 of the forward portion 17 of the knurl mount, and
mates with a key 44 mounted on the second end 43 of the shaft 41 to
define the rotational or angular orientation of the knurl mount 14
relative to the shaft 41. As best seen in FIG. 5, threaded shaft
mounting hole 29 extends into the rear portion 15 of the tool
mount, for attachment to a corresponding bolt 45 extending through
shaft 41. As illustrated in FIGS. 1 and 13, bolt 45 can be engaged
with the knurl mount 14. Locking nut 47 is then tightened to pull
the mount 14 into engagement with the second end 43 of shaft
41.
[0070] As best seen in FIGS. 3 and 4, forward portion 17 of knurl
mount 14 includes knurl wheel receiving cavity 23. Cavity 23 is
bounded by rear wall 24, first and second side walls 25, 26, and by
mounting surface 27. Forward portion 17 can optionally include
holes 22 in side walls 25, 26 for observing the wheel 12 mounted in
the cavity 23, and for injecting coolant during knurling for chip
removal.
[0071] As seen FIG. 4, mounting surface 27 is oriented such that
the normal axis C to the mounting surface is not perpendicular to
axis 20 of the knurl mount 14. Mounting surface 27 has therein
threaded knurl mounting hole 28 surrounded by cylindrical shoulder
27a. Knurl wheel axle 74 is inserted in shoulder 27a. Axle 74
includes first portion 78 which closely fits within shoulder 27a
and second portion 76 which rests on mount surface 27. Axle also
includes shaft 77 on which knurl wheel 12 is mounted. Mounting hole
28, cylindrical shoulder 27a, and shaft 77 are oriented along
normal axis C of the mounting surface 27. Normal axis C intersects
longitudinal axis 20 of the knurl mount 14. Normal axis C defines
the rotational axis of the knurl wheel 12 when mounted in the knurl
mount 14. Normal axis C is oriented at angle a relative to the
longitudinal axis 20 of the knurl holder 14. Angle .alpha. can be
selected in light of the knurl wheel 12 to be used so as to provide
the desired clearance angle .beta., where .beta.=90-.alpha.. Values
for angle .alpha. of from 80.degree. to 87.degree. have been found
suitable, with 85.degree. preferred for some knurl patterns.
[0072] FIG. 6 illustrates the knurl mount 14 of FIG. 5 with knurl
wheel 12 mounted on shaft 77. Cap 70 fits on top of knurl wheel 12,
and screw 72 fits through the cap 70 and shaft 77 and engages in
mounting hole 28 in the mount surface 27 of the knurl mount 14.
Knurl wheel 12 thus rotates about axis C. Mount surface 27 is
located relative to longitudinal axis 20 of the knurl mount such
that the forward most portion X of the knurl wheel 12 is on
longitudinal axis 20 and extends beyond the front face 18 of mount
14. It is thus seen that the diameter of wheel 12, the thickness of
the wheel 12 along axis C, the thickness of first and second
portions 76, 78 of axle 74, the position of mount surface 27
relative to the axis 20, and the magnitude of angle .alpha. all
must be considered in selecting a configuration that places
forward-most portion X of the knurl wheel 12 on axis 20.
[0073] FIGS. 4-7 all illustrate the knurl mount 14 oriented such
that the knurl wheel rotational axis C and mount longitudinal axis
20 lie in a plane that is perpendicular to longitudinal axis 36 of
workpiece 30. Angle 0 between the workpiece axis 36 and the plane
of axis C and axis 20 is defined as 90.degree. at such an
orientation. When cylindrical workpiece 30 is oriented to have its
longitudinal axis 36 horizontal, the-just described orientation of
the knurl wheel puts wheel axis C and longitudinal axis 20 in a
vertical plane. FIGS. 7-11 illustrate the orientation of the knurl
wheel 12 relative to the workpiece 30, with the knurl mount 14
removed from the illustration for clarity. In FIGS. 8 and 9, the
tool holder 10 has been adjusted to orient wheel 12 such that the
plane defined by wheel axis C and mount longitudinal axis 20 is at
an obtuse angle .theta. relative to workpiece axis 36. In FIGS. 10
and 11, tool holder 10 has been adjusted to orient the wheel 12
such that axis C and axis 20 lie in a plane that forms an acute
angle .theta. relative to the axis 36 of the workpiece.
[0074] FIGS. 1, 12 and 13 illustrate the rotary drive assembly 50.
Mounting plate 51 is bolted to the rear surface of the spindle 40
by bolts 62 and washers 64. The first end 42 of the shaft 41 has
mounted thereon sleeve 46. Sleeve 46 includes a ring portion 46a
affixed to the first end 42 of shaft 41, and a hollow cylindrical
portion 46b extending rearwardly therefrom. Between ring portion
46a of the sleeve and the plate 51 is a clock spring 48 to bias the
shaft 41 in one direction to help eliminate backlash.
[0075] Gear wheel 52 fits over the cylindrical portion 46b of
sleeve 46 and adjacent to ring portion 46a of the sleeve 46, and is
secured to the ring portion 46a such that rotation of the gear
wheel causes the sleeve 46 and shaft 41 to rotate. Gear wheel 52
has a plurality of outwardly extending teeth. Mount 54 is attached
to the top of mounting plate 51, such as by welding, and supports
worm gear 53. On one end of worm gear 53, unthreaded shaft portion
53a is affixed to handle 55 to manually rotate the worm gear.
Unthreaded portions 53a of the worm gear 53 are rotatably secured
in holes through the rearward extending portions 54a of the mount
54. Worm gear 53 is engaged with the teeth on the gear wheel 52,
such that rotation of the handle 55 causes the gear wheel to
rotate, thereby rotating the shaft 41, knurl mount 14, and knurl
wheel 12.
[0076] Secured to the rearward facing surface of the gear wheel 52
is a rotating calibrated scale 59. Secured to the mount plate 51 is
a matching fixed position calibrated scale 60 (removed from FIG. 1
for clarity) that is adjacent to the rotating calibrated scale 59.
Preferably, this arrangement has a 360.degree. scale readable with
a vernier scale to 6 minutes of arc.
[0077] A stopper mount 56 is attached to a side of the mounting
plate 51, such as by welding. Plate portion 56a of the stopper
mount extends rearward to the forward facing surface of the gear
wheel 52. First arm portion 56b of the stopper mount extends
rearward beyond the gear wheel 52. Second arm portion 56 of the
stopper mount extends in front of and overlaps the rearward facing
surface of the gear wheel 52. Set screw 58 is mounted in a threaded
hole in the end of the second arm 56c of the stopper mount. A
stopper member 57 is attached to the stopper mount 56, such as with
bolts 66 and washers 68. Stopper member includes first portion 57a
extending rearward beyond the gear wheel, and cantilevered arm
portion 57b extending from the portion 57a adjacent to and
overlapping the rear facing surface of the gear wheel 52. The
cantilevered arm 57b is positioned such that its free end is
between the set screw 58 and the face of the gear wheel 52. When
the set screw is loosened and disengaged from the cantilevered arm,
rotation of handle 55 and worm gear 53 causes the gear wheel 52 to
rotate, thereby rotating shaft 41. When the shaft is at the desired
rotational orientation, the set screw 58 can be tightened to press
the cantilevered arm 57b against the face of the gear wheel,
thereby minimizing the chance of unintended rotation of the shaft
41.
[0078] Bolt 45 extends through the shaft 41 for engagement with the
threaded hole 29 in the knurl mount 14. After bolt 41 has been
tightened into the knurl mount, locking nut 47 is tightened to pull
the bolt and knurl mount rearward, to thereby securely seat the
knurl mount 14 in the second end 43 of shaft 41.
[0079] The just-described preferred embodiment of the manual
rotational drive assembly 50 can instead be any suitable manual or
automatic positioning arrangement. For example, rotational drive
assembly 50 could be a motor driven, high accuracy, computer
controlled positioning system. Also, commercially available rotary
indexing heads may be suitable for the knurl tool holder.
[0080] Knurling Tool
[0081] The above-described knurl tool holder may be advantageously
used with any suitable knurl wheel 12, including conventional,
commercially available cutting knurl wheels.
[0082] One embodiment of a cut knurling wheel tool 12 is
illustrated in FIGS. 14 and 15. Knurling wheel 12 has along its
outer working surface a plurality of teeth 44. Each tooth 44
includes a tooth ridge 48 and first and second side surfaces 52. A
valley 50 bounded by one side surface 52 from each adjacent tooth
44 is located between each pair of adjacent teeth 44. Each wheel 12
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. For cut knurling, it is preferred that
the major surface 42 of the knurling wheel has an undercut 54.
Undercut 54 is illustrated as an arcuate surface extending around
the full circumference of wheel 12. The undercut provides an
improved rake angle when the knurling wheel is engaged with the
outer surface of the workpiece. Alternatively, undercut 54 can 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,
preferably at least as far as tooth valley 50. A positive rake
angle provides more efficient cutting than a zero or negative rake
angle, and also reduces the amount of burring of the workpiece.
[0083] The inventive knurl tool holder 10 described herein is
particularly well suited for use with knurl wheels having teeth of
different configuration within a single knurl wheel. Knurl tool
holder 10 can orient the knurling wheel 12 at infinitely variable
angular orientations, while maintaining the forward most point of
the knurl wheel located at the same position. This allows use of
knurl wheels 12 that have a plurality of tooth configurations on a
single knurl wheel. The variation of tooth configuration can be in
tooth height, tooth width, tooth shape, spacing between adjacent
teeth, use of non-symmetrical teeth, or any other desired
parameter.
[0084] The tooth configuration may vary completely around the
circumference of the wheel, that is no two teeth being identical.
Alternatively, a "sequence" of a number of teeth having different
configurations within the sequence may repeat an integer number of
times "N" around the knurl wheel circumference. If the tooth at the
beginning of each such repetitive sequence is designated as "tooth
1" and the groove in the workpiece cut by that tooth is designated
as "groove 1," it can be seen that a clean pattern of grooves in
various configurations corresponding to the tooth configurations
will be generated if during knurling a "tooth 1" always enters a
"groove 1."
[0085] One preferred knurling wheel illustrated in FIG. 14A, has
its tooth configuration varied by cutting different angles
.gamma..sub.1, .gamma..sub.2, .gamma..sub.3, . . . .gamma..sub.N of
the valley 50 between teeth 44 on the knurl wheel 12. At least some
of the teeth 44 are preferably asymmetric. For example, a wheel
tooth formed between adjacent 90.degree. and 70.degree. valleys
would be asymmetric. The peak angles of the ridges formed on the
workpiece between grooves are nearly equal to the "valley" angles
.gamma. between the teeth on the knurling wheel.
[0086] While the knurling teeth 44 are illustrated herein as
forming a ridge at 48 and a 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 with
cut knurling rather than form knurling, although certain
configurations may be used under some conditions with form
knurling.
[0087] The knurling wheel should be a material that is strong
enough to resist chipping and breaking during use, and that
maintains a sufficiently sharp cutting edge during use. Suitable
knurling wheels have been made of tool steel and tungsten carbide,
with tungsten carbide having improved wear resistance. Wear
resistant coating such as TiN, TiCN, and CrN may be useful.
EXAMPLE 1
[0088] One example of a knurling wheel 12 was made as follows. A
plurality of triangular teeth were cut into a round wheel having an
initial diameter of 3.2334 cm (1.273 inches) using conventional
wire EDM procedures. The diameter of the wire used to cut the teeth
was 30 micrometers (0.0012 inch). The teeth were in a pseudo-random
sequence of varying teeth sizes. The sequence repeated each quarter
(90.degree.) of the wheel, i.e., the pattern repeated 4 times
around the wheel. The knurling wheel was made of tungsten carbide
type CD-636.
[0089] The table below summarizes the details for the pseudo-random
pattern of teeth. The pattern consisted of forty-four teeth, each
0.0356 cm (0.014 inch) high measured radially from the base of the
tooth to the tip. The configuration of the teeth is defined with
reference to the angle and width of the "valleys" cut in the
knurling wheel. The "Angle" reported in the table is the angle of
the valley cut into the wheel by the wire EDM. The "Width" reported
in the table is the circumferential tip-to-tip distance between
adjacent teeth, measured at the respective center of each
tooth.
1TABLE 1 Width Valley Angle micrometers Number degrees (inches) 1
90 71.628 (0.0282) 2 70 51.054 (0.0201) 3 80 60.706 (0.0239) 4 70
51.054 (0.0201) 5 90 71.628 (0.0282) 6 70 51.054 (0.0201) 7 80
60.706 (0.0239) 8 90 71.628 (0.0282) 9 70 51.054 (0.0201) 10 90
71.628 (0.0282) 11 70 51.054 (0.0201) 12 80 60.706 (0.0239) 13 60
42.672 (0.0168) 14 80 60.706 (0.0239) 15 60 42.672 (0.0168) 16 70
51.054 (0.0201) 17 60 42.672 (0.0168) 18 80 60.706 (0.0239) 19 70
51.054 (0.0201) 20 60 42.672 (0.0168) 21 70 51.054 (0.0201) 22 80
60.706 (0.0239) 23 70 51.054 (0.0201) 24 60 42.672 (0.0168) 25 70
51.054 (0.0201) 26 80 60.706 (0.0239) 27 60 42.672 (0.0168) 28 70
51.054 (0.0201) 29 60 42.672 (0.0168) 30 80 60.706 (0.0239) 31 60
42.672 (0.0168) 32 80 60.706 (0.0239) 33 70 51.054 (0.0201) 34 90
71.628 (0.0282) 35 70 51.054 (0.0201) 36 90 71.628 (0.0282) 37 80
60.706 (0.0239) 38 70 51.054 (0.0201) 39 90 71.628 (0.0282) 40 70
51.054 (0.0201) 41 80 60.706 (0.0239) 42 70 51.054 (0.0201) 43 90
71.628 (0.0282) 44 90 71.628 (0.0282)
[0090] The knurl wheel teeth of Example 1 are frequently
asymmetrical. For example, the wheel tooth formed between adjacent
90.degree. and 70.degree. valleys would have a half angle on the
90.degree. groove side of 43.73.degree. and a half angle on the
70.degree. groove side of 34.10.degree. (these half angles are not
simply 45.degree. and 35.degree., respectively, because of the
curvature of the wheel). The peak angles of the ridges formed on
the workpiece between grooves are nearly equal to the "valley"
angles between the teeth on the knurling wheel.
[0091] Method of Knurling
[0092] A preferred method of knurling a workpiece is illustrated in
FIGS. 16 and 17, in which the tool holder 10 has been removed to
more clearly illustrate the position of knurl wheel 12 with respect
to the workpiece 30. FIGS. 16 and 17 are both top plan views of the
workpiece 36 and knurl wheel 12. A first plurality of grooves 38
having peaks 39 are initially cut. The tool holder 10 is set to
orient the plane defined by knurl wheel axis C and knurl mount axis
20 at an obtuse angle .theta.. The tool holder is positioned such
that axis A intersects and is perpendicular to the longitudinal
axis 36 of the workpiece. The cutting knurl wheel 12 is engaged to
a desired depth of cut into the workpiece surface 34 as the
workpiece is rotated in the direction shown, and the knurl wheel is
traversed in the direction shown. This first plurality of grooves
38 will have a first helix angle .theta..sub.1, and the respective
groove cross-sections will generally correspond to the shape of the
valley 50 between teeth 44 on the knurl wheel.
[0093] The lathe is then stopped, and the tool holder is set to
orient the plane defined by axis C and axis 20 to an acute angle
.theta. relative to the workpiece axis 36. The cutting knurl wheel
12 is engaged to a desired depth of cut into the workpiece surface
34 as the workpiece is rotated in the direction shown, and the
knurl wheel is traversed in the direction shown. This second
plurality of grooves 38' having peaks 39' will have a second helix
angle .theta..sub.2, opposite to .theta..sub.1. The respective
groove cross-sections will generally correspond to the shape of the
valley 50 between teeth 44 on the knurl wheel. A plurality of
pyramids will be formed by the intersection of the first and second
pluralities of grooves.
[0094] Helix angles .theta..sub.1 and .theta..sub.2 may be equal
and opposite, in which case the pyramidal pattern will be aligned
along the circumferential direction of the workpiece. Alternatively
the helix angles .theta..sub.1 and .theta..sub.2 may be unequal
magnitude and opposite sign, in which case the pyramidal patter
will not be aligned in the circumferential direction of the
workpiece. Further details on selecting .theta..sub.1 and
.theta..sub.2 so as to provide a desired orientation of the
pyramidal pattern are found in WIPO International Patent
Application Publication Number WO 97/12727, published on Apr. 10,
1997, "Method and Apparatus for Knurling a Workpiece, Method of
Molding an Article With Such Workpiece, and Such Molded Article,"
Hoopman et al., the entire disclosure of which is incorporated
herein.
[0095] If desired, optional clean up cuts may be repeated in the
existing grooves to provide additional depth of cut, or to clean up
the profile of the grooves.
[0096] With the knurl tool holder 10 disclosed herein, the
synchronization of the knurl tooth sequence with the generated
structure on the workpiece is achieved by helical angle
adjustments. For example, it may be desired to knurl a workpiece 30
of diameter "D" with a knurl wheel 12 of diameter "d" having a
varying tooth form sequence that repeats "N" times around the
circumference of the knurling wheel 12. If the knurl wheel 12 is
positioned by the holder 10 such that the knurl wheel rotational
axis C is at 90.degree. to the longitudinal axis 36 of the
workpiece, the workpiece imparts no rotational motion to the knurl
wheel. As the holder 10 is moved axially along the surface of the
workpiece, a pattern of circumferential grooves will be generated
with the sequence of teeth repeating at an axial distance of:
(.pi..times.d)N.
[0097] When the axis C of the knurl wheel 12 is positioned parallel
or 0.degree. to the workpiece axis 36, the knurl wheel 12 is driven
by the roll in pure rotation at a rotational speed that is D/d
times the workpiece rotational speed. Between the 0.degree. and
90.degree. knurl axis positions there are various angular positions
.theta. at which the value of:
(D.times.N.times.Cosine(.theta.))d
[0098] is an integer. Near these theoretical positions the knurl
wheel sequence will properly align with an integer number of
repeats such that a tooth 1 of one of the sequences of teeth will
align in a groove 1 in the sequence of grooves being generated in
the surface of the workpiece.
[0099] Table 2 presents the value of .theta. to provide the desired
amount of repeats of the sequence of teeth. This is calculated for
a workpiece having a diameter of 8.0545 inches, and knurl wheel
having a diameter of 1.272 inches, and for knurl wheels having one,
two, and four repeats of teeth sequences.
2 TABLE 2 Repeats Angle .theta. Wheel A One Sequence 6 18.51 5
37.79 4 50.79 3 61.70 2 71.57 1 80.91 Wheel B Two Sequences 12
18.51 11 29.63 10 37.79 9 44.67 8 50.79 7 56.42 6 61.70 5 66.73 4
71.57 3 76.29 2 80.91 1 85.47 Wheel C Four Sequences 25 8.96 24
18.51 23 24.66 22 29.63 21 33.93 20 37.79 19 41.35 18 44.67 17
47.80 16 50.79 15 53.65 14 56.42 13 59.09 12 61.70 11 64.24 10
66.73 9 69.17 8 71.57 7 73.94 6 76.29 5 76.81 4 80.91 3 83.19 2
85.47 1 87.74
[0100] The knurl pattern formed by the just-described method and
apparatus is illustrated in FIG. 18. The knurl pattern comprises a
plurality of pyramids 60 projecting from the workpiece 30. The
pyramids each comprise peak 62, side edges 64 extending from the
peak, base edges 68, and sides surfaces 66 bounded by the side
edges and base edges. A cross section of the pyramids 60 is
illustrated in FIGS. 19A and 19B. As seen in FIGS. 18 and 19A, the
first plurality of grooves 38 have groove sides 66a. As seen in
FIGS. 18 and 19B, second plurality of grooves 38' have groove sides
66b. The intersection of the two sets of grooves thus forms the
pyramids 60. Each pyramid has a pair of opposed sides 66a formed by
adjacent first grooves and a pair of opposed sides 66b formed by
adjacent second grooves. It is seen that the pyramids remaining
between the intersecting grooves cut by the knurling teeth 41 have
an angle .gamma..sub.N that will be substantially equal to the
valley angle .gamma..sub.N between the knurling teeth for a small
value of clearance angle .beta..
[0101] The knurl pattern is illustrated herein as having pyramidal
peaks which come to a point at 62 formed by the intersection of
peaks 39 and 39'. This occurs when the cutting wheel teeth 44 are
engaged to their full depth into the workpiece, engaging 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 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 pyramids 60. It is also possible to use teeth
44 configured to have flat or curved spaces between the teeth 44 at
valley 50, or a flat or other configuration at 48 rather than an
edge ridge.
[0102] One preferred method of knurling a workpiece according to
the present invention will be described with respect to the
following example.
EXAMPLE 2
[0103] The workpiece, a steel roll with a 20.32 cm (8 inch)
diameter and a 91.4 cm (36 inch) length, was plated with 0.127 cm
(0.050 inches) of copper having a hardness of 210 to 230 Vickers.
The roll was mounted in a Lodge & Shipley lathe and faced off
to a diameter of 20.562.+-.0.0005 cm (8.0952.+-.0.0002 inches).
Shoulders, 0.2794 mm (0.0110 in) deep, 3.81 cm (1.5 inch) wide were
then cut into the workpiece surface at each end, with a 1:10 taper
ramp up to the outer diameter of the roll.
[0104] A knurl tool holder 10 as described with respect to the
preferred embodiment above, was installed on the cross slide of the
lathe. Axis A of the tool holder 10 intersected with and was
perpendicular to the longitudinal axis 36 of the workpiece. A knurl
mount 14 having the axis C for the mounting wheel at an angle
.alpha. of 85.degree. was mounted on the second side 43 of the
shaft 41. A dial indicator was used to set the plane defined by
knurl wheel axis C and knurl mount axis 20 to vertical. The angle
on vernier scale 59, 60 at this orientation read 280.degree. 36'.
In the remaining description, this orientation will be deemed to be
an angle .theta. of 90 degrees. If the tool holder 10 were adjusted
to rotate the knurl mount 14 clockwise (as viewed from the rear
side of the tool holder 10 facing the workpiece) by 90 degrees such
that the plane defined by axis C and axis 20 is horizontal, the
vernier would read 190.degree. 36'. In the remaining discussion,
such an orientation will be deemed to be and angle .theta. of zero
degrees. Positive angles are counterclockwise as viewed from the
rear of the tool holder 10 looking toward the workpiece.
[0105] The knurling wheel 12 of Example 1 was mounted in the knurl
mount 14. Three adjacent 90.degree. valleys at the end of each of
the four sequences of teeth provided a way to index the rotation of
the knurl wheel. The location of the sequence was further
facilitated by applying a small ink dots to the knurl wheel to mark
the location of the center one of the three 90.degree. valleys in
each of the four sequences around the circumference.
[0106] It was necessary to adjust the angular orientation of the
tool mount 10, and thereby adjust the angle of the knurl wheel axis
of rotation C, to provide an integer number of repeats of the
one-quarter circumference, 44 tooth sequence, in the knurling wheel
12 around the circumference of the roll. The angle .theta. required
to obtain exact pattern match between "tooth 1" on the wheel and
"groove 1" on the surface of the roll was determined in an
iterative process as follows. Because the circumference of knurl
wheel 12 was 10.16 cm (4.0 inches), the circumferential length of
one sequence was 2.54 cm (1.0 inch).
[0107] The first direction of cut was intended to produce 21
repeats of the 44 tooth sequence around the circumference of the
roll with teeth having a height of 0.036 cm (0.014 inch). The
intended depth of cut of the teeth was 0.033 cm (0.013 in). The
tips of the teeth would therefore be at a roll diameter D of:
20.562-(2.times.0.033)=20.492 cm
[0108] (8.095-(2.times.0.013)=8.069 inch).
[0109] The length of the repeating sequence as measured along the
circumferential direction of the roll face, at the desired cutting
depth, to provide 21 repeats along the circumference was 1 8.069 21
= 1.207 inches
[0110] The length of the repeat was adjusted by changing the angle
of the knurl wheel relative to the axis of the roll face being cut.
If the knurl wheel were left at .theta. of zero (axis C parallel to
the axis of the roll), the knurl wheel would emboss a pattern in
the roll face identical to that of the knurl wheel. The repeat
would be 1.0 inch, the circumferential length of one sequence on
the knurl wheel 12. If the axis C of the knurl wheel was set to
.theta. of 90.degree., the knurl wheel would not rotate, so the
repeat distance would be infinite. For a knurl wheel traveling
parallel to the longitudinal axis of the roll from the tailstock
toward the headstock of the lathe, the knurl wheel angle, .theta.
required to produce intermediate repeat distances can be estimated
by 2 = sin - 1 ( K R ) + 90 .degree.
[0111] Where K is the repeat distance of the knurl wheel and R is
the repeat distance of the circumference of the roll face. Here,
where K=1.0 inch and R=1.207 inches, then .theta.=145.degree. 56'.
Thus, the tool holder was be adjusted so that axis C of the cutting
wheel is at .theta.=145.degree. 56'.
[0112] The knurl wheel 12 was then moved to about 0.3175 cm (1/8")
from the outer edge of the shoulder previously cut on the tailstock
end of the roll face. The lathe carriage was set to feed 0.0635
cm/revolution (0.0025 inch/revolution) and engaged the feed. The
workpiece was rotated by hand until the carriage actually began to
feed toward the headstock. With the lathe stopped, the cross slide
was slowly hand fed until the knurl wheel touched the work piece
surface and then was fed in an additional 0.0051 cm (0.002
inch).
[0113] The workpiece was rotated just short of one revolution to
cut a single row of grooves 0.0051 cm (0.002 inch) deep in the
surface of the workpiece. The pattern of the grooves was visually
examined with a hand held 4X magnifying glass. To determine the
start and end of the 44 tooth sequence, the three adjacent equally
spaced grooves in the workpiece (created by the three adjacent
teeth corresponding to the three 90.degree. valleys in the knurling
wheel) where located, and the center of these three grooves was
marked with a pencil. This was repeated for three successive tooth
sequences. Next, a broad tipped marker was used to blacken the row
of grooves in the area where the groove sequences were marked.
Then, the workpiece was rotated by hand an additional 360.degree.
so that a second row of grooves was cut circumferentialy
superimposed, but 0.0064 cm (0.0025") to the left of the first row
of grooves. The pattern created by the three 90.degree. valleys on
the second row was located and marked with a pencil. This second
set of grooves was easy to pick out because it was freshly cut and
not blackened. Comparison to the location of the marks on the first
and second rows of grooves showed that the sequence of grooves was
about 2 grooves too long to give a pattern match.
[0114] The knurling wheel was backed out from the workpiece and the
carriage moved about 0.3175 cm (1/8") past the previously cut area
to a virgin area of the workpiece. The tool angle .theta. was
increased by 0.degree. 12' and the above procedure repeated. The
groove pattern was observed to be about 1 groove too long. The tool
holder angle .theta. was increased an additional 0.degree. 12', and
the above procedure was repeated. The groove pattern was observed
to be about 3/4 of a groove too short for pattern match.
[0115] The lathe speed was set to 100 rpm and power was applied.
The lathe was stopped after feeding about 0.6350 cm (1/4") without
disengaging the carriage feed. Examination of the cut area showed
cleanly cut grooves with exactly 21 repeats of the 44 tooth,
one-quarter knurling wheel sequence. The lathe was restarted and
cutting continued until it had fed about 0.6350 cm (1/4") past the
ramp of the shoulder area. After stopping the lathe, examination of
the groove structure with a roll microscope showed that the cut was
at full depth as indicated by the lack of a flat on the top of the
ridges between the grooves. Cutting was continued for about another
2.54 cm (one inch) across the face of the roll before stopping
again.
[0116] The groove structure continued to look good in spite of two
missing tooth faces which had chipped away. The odd number of
repeats (21) meant that the corresponding teeth in each of the four
repeating sequences in the knurling wheel combined to cut a single
groove. That is, each particular "groove 1" in the workpiece
surface was engaged sequentially by a "tooth 1" from each of the
four repeating knurl wheel sequences. This helps overcome any
defect that might have resulted from a missing or broken tooth.
[0117] The lathe was restarted and the cut continued until it was
about 1.27 cm (1/2") short of reaching the shoulder on the
headstock end of the roll. The groove structure on the roll still
appeared acceptable. At this point, the knurl wheel had 22 damaged
teeth, but only the two teeth that were observed to be severely
chipped earlier were missing completely. Average groove depth at
the tailstock end was 0.0318 cm (0.0126 inch). The average groove
depth at the middle and headstock end of the roll was 0.0315 cm
(0.0124 inch) indicating only minor knurl wheel wear. The workpiece
surface now had a first plurality of parallel grooves 38 with
ridges 39 oriented at a first helix angle .theta..sub.1 as
illustrated in FIG. 16.
[0118] The knurl mount 14 was removed, the knurl wheel 12 was
removed and reinserted with the opposite major surface facing up to
expose a fresh cutting surface, and then the knurl mount was
reinstalled. When the plane defined by knurl wheel axis C and knurl
mount axis 20 was vertical, the vernier angle now read 280.degree.
48', indicating that the defined zero tool angle had shifted to a
vernier reading of 190.degree. 48'. This vernier reading will now
be deemed to be .theta. of 0.degree.
[0119] A second plurality of grooves 38' having ridges 39' oriented
at a second helix angle of .theta..sub.2 in opposite direction to
.theta..sub.1 was formed by cutting a pattern of 15 repeats of the
44 tooth sequence in the roll face starting at the headstock end.
The repeat distance of 15 sequences in the circumferential
direction of the workpiece was 3 8.069 15 = 1.690 inches
[0120] For a knurl wheel moving from the headstock to the tailstock
the knurl wheel axis angle .theta. is given by 4 = cos - 1 ( K R
)
[0121] For K=1.0 inches and R=1.69 inches, .theta.=53.degree.
43'.
[0122] Because the previous estimate was too low, a similar error
would be expected to make this estimate to be too high. The tool
holder 10 was set to .theta. of 53.degree. 12' and the carriage was
set to feed 0.0064 cm/revolution (0.0025 inch/revolution) from the
headstock to the tailstock and the same groove pattern match
procedure described earlier was used. The groove pattern was 41/2
teeth short. The procedure was repeated with the tool angle .theta.
increased by 0.degree. 30'. The pattern was observed to be about
21/2 teeth too long. Tool angle was reduced by 0.degree. 12' which
resulted in a pattern match about 1 tooth short. The lathe was run
at 100 rpm for about 1/4" of cutting, but the knurl wheel tooth
sequence did not align into the workpiece surface groove sequence.
Rather it left a gnarly, chewed up surface. The tool was again
moved to fresh surface and the tool angle increased by 0.degree.
06'. The sequence match was observed to be about 1 tooth long. The
lathe was started and again cut about 1/4" of pattern, but the
sequence would not align. Again, the knurl wheel holder was moved
to a new area on the workpiece and reduced by 0.degree. 03'. The
pattern match was observed to be about 1 tooth too long. After a
short powered run, the sequence did not align. The depth of cut was
decreased about 0.0005 under the theory that the slightly larger
roll diameter for the knurl teeth (and thus increased pattern
length) would allow the sequence to align. However, sequence
alignment was not achieved. At this point, there was no remaining
uncut surface on the shoulder on which to attempt more starts.
[0123] The knurling wheel was backed out and moved to a fresh start
area on the full diameter area of the roll. The vernier reading was
left at its current setting. The lathe was started and the knurling
wheel slowly fed into the surface of the roll as the carriage fed
toward the tailstock. A short time after target depth was achieved,
it was apparent that the sequence aligned. A check of the depth of
the grooves showed that they were 0.0005 too deep to match the
grooves cut in the first pass. Depth of cut was decreased by 0.0005
and cutting continued until about 3/4" of cross-cut pattern had
been cut. Depth match was within 0.0001. There was some burring on
the pyramids formed by the intersecting grooves as the knurl teeth
broke into the first plurality of grooves, but the pyramid edges
were burr-free on the opposite edges formed when the knurl wheel
entered a ridge to cut the next pyramid. The knurl wheel was
examined for damage. Only two teeth were chipped.
[0124] Cutting of the second plurality of grooves was continued
until the cross-cut pattern was about 0.127 cm (1/2") short of the
shoulder area of the tailstock end. Examination of the roll showed
that the second cut was 0.0005 cm (0.0002 inch) deeper than the
first cut at the tailstock end. Second plurality of grooves 38'
having peaks 39' intersected the first plurality of grooves.
Pyramids covered the roll surface in the cross-cut area.
[0125] Next, light cuts with the same knurling wheel were made in
the first set plurality of grooves to reduce the burrs on the edges
of the pyramids. This second pass on the first plurality of grooves
began at the tailstock end in the 1/2" band of single direction
grooves that were cut in the first pass. The carriage feed was
engaged to feed from the tailstock to the headstock and the
workpiece rotated by hand until the carriage started to move in
that direction. The three 90.degree. teeth were lined up with the
set of grooves they had cut in the first pass direction and the
knurl wheel was fed in to the same depth as used for the first
pass. A 4X magnifying glass was used to check that the knurl wheel
was indexed properly as the workpiece was slowly rotated by hand.
The lathe was started and about 0.9525 cm (3/8") of pattern was
re-cut. Two depth checks were made 90.degree. apart on the roll
face. One showed the depth of cut was 0.0025 cm (0.0010 inch) too
deep and the second 0.0038 cm (0.0015 inch) too deep. There was now
significant burring in the second plurality of grooves. Depth of
cut was reduced by 0.0025 cm (0.0010 inch). After cutting another
0.6350 cm (1/4" inch), burring was significantly reduced but depth
of cut still measured 0.0025 cm (0.0010 inch) too deep. The knurl
wheel was backed out another 0.0019 cm (0.00075 inch) and now the
cut measured 0.0020 cm (0.0008 inch) too deep. The knurl wheel was
backed out an additional 0.0019 cm (0.00075 inch), but this depth
of cut was too shallow and burrs remained in the first pass
grooves. Depth of cut was increased 0.0013 cm (0.0005 inch) and
after a short run, burrs were observed to be in the second
plurality of grooves, but a previous slightly deeper cut had less
overall burring. The depth of cut was again increased by 0.0013 cm
(0.0005 inch). After a short run, some of the grooves were burr
free in both directions and other areas showed only light burrs in
the second plurality of grooves.
[0126] The lathe was restarted and the remaining cross-cut face was
re-cut at that depth. After the re-cut was completed, the roll was
examined with a rollscope at 100X. Some peaks had no burrs whereas
others had burrs on one edge only. The depth match looked
excellent.
[0127] The tool angle was re-set for a cleanup pass in the second
plurality of grooves. The same procedure that was used for the
cleanup in the first plurality of grooves was used to index the
knurling wheel to the existing second plurality of grooves. Depth
of cut was again adjusted by observing the size and location of
burrs left by the knurl wheel. After adjustment for optimum depth,
the second plurality of grooves were re-cut. The resulting roll
showed depth match of better than 0.0005 cm (0.0002 inch) and
bright rounded tips on the pyramids.
[0128] Next, the roll surface was brushed with kerosene to remove
remaining loose burrs. The kerosene was manually applied with a
soft brass brush to the surface of the slowly spinning roll. The
kerosene was then removed from the roll with a towel, and
initially, numerous metal chips were collected on the towel.
Brushing was continued until very few metal chips appeared on the
towel.
[0129] The surface of the roll was then plated with a 3 to 5
micrometer thick layer of electroless nickel. The electroless
nickel provided corrosion protection and improved release of
polymeric material from the roll surface.
[0130] After being plated, the roll was used for embossing
polypropylene film for use in structured abrasive manufacture.
[0131] Molded Article
[0132] One preferred method of using workpiece, or master tool, 30
to fabricate a molded article such as a production tool, is
illustrated in FIG. 20. The production tool 82 is fabricated by
extruding at station 100 a moldable material, preferably a
thermoplastic material, onto the knurled outer surface 34 of master
tool 30. The thermoplastic material is forced against surface 34 at
nip 102. Production tool 82 is then peeled away from the master
tool 30 and wound onto mandrel 106. In this manner, a production
tool 82 of any desired length may be obtained. The molding surface
86 will have the inverse of the pattern on the knurled outer
surface 34 of master tool 30. When the pattern imparted on outer
surface 34 of master tool 30 is a positive of the pattern of the
ultimate fabricated structured abrasive article (or other article
as desired), the pattern on mold surface 86 will be the inverse of
the pattern of the ultimate article. As seen in FIG. 21, 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. Back surface 84 is relatively flat
and smooth. It may be desired that production tool 82 is 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 ultimate pattern on production tool 82.
[0133] Thermoplastic materials that can be used to construct the
production tool 82 include polyesters, polycarbonates, poly(ether
sulfone), polyethylene, polypropylene, poly(methyl methacrylate),
polyurethanes, polyamides, polyvinylchloride, polyolefins,
polystyrene, or combinations thereof. Thermoplastic materials can
include additives 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.
[0134] 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 delaminate than other structured abrasive
articles which have a seam or interruption in the pattern due to
seams in the production tool.
[0135] The production tool 82 can also be formed by embossing a
moldable material 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 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.
[0136] 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 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 or polymerized 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 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.
[0137] While the inventive methods and apparatuses described herein
are particularly well suited for use in manufacturing structured
abrasives, the present invention is not thereby limited. For
example, the inventive knurling methods and apparatuses described
herein may be used on a workpiece 30 that is the ultimate
manufactured 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 making a
production tool for use in subsequent processes. That is, the
molded article which is molded with the knurled workpiece may be
the ultimate manufactured article having its own use. Furthermore,
the knurled workpiece 30 can be used as a rotogravure coater for
making abrasive or other articles.
[0138] Method of Making a Structured Abrasive Article
[0139] 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
techniques include low shear and high shear mixing, with high shear
mixing being preferred. 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 minimized by pulling a vacuum during the
mixing step. In some instances it is 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.degree. C. to
70.degree. C. However, the temperature of the slurry should be
selected so as not to deleteriously affect the substrate to which
it is applied. It is important that the abrasive slurry have a
rheology that coats well and in which the abrasive particles and
other fillers do not settle.
[0140] 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 method generally results in an abrasive
composite that has a non-precise shape. In the second method, the
abrasive slurry is coated into the 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 while
in the cavities of the production tool this results in the abrasive
slurry flowing and distorting the abrasive composite shape.
[0141] For both methods, if a thermosetting binder precursor is
employed, the energy source can be thermal energy or radiation
energy depending upon the binder precursor chemistry. For both
methods, if a thermoplastic binder precursor is employed the
thermoplastic is cooled such that it becomes solidified and the
abrasive composite is formed.
[0142] FIG. 22 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 substrate 112 having a first
major surface 113 and a second major surface 114 leaves an unwind
station 115. At the same time, the production tool 82 leaves an
unwind station 116. The mold or contacting surface 86 of production
tool 82 is coated with a mixture of abrasive particles and binder
precursor at coating station 118. The mixture can be heated to
lower the viscosity thereof prior to the coating step. The coating
station 118 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 86 of production
tool 82 is coated, the substrate 112 and the production tool 82 are
brought together such that the mixture wets the first major surface
113 of the substrate 112. In FIG. 22, 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/backing construction
against a support drum 122. It has been found useful to apply a
force of 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 82 is then separated
from the shaped, handleable structure 126. Separation of the
production 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 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 sufficient 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 production tool. Examples of such release coatings
include silicones and fluorochemicals. The angle a 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.degree., 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 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.
[0143] 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.
[0144] FIG. 23 illustrates an apparatus 140 for an alternative
method of preparing an abrasive 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
major surface 143 and a second major surface 144 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 of the substrate 142 by a contact nip roll 148, which
also forces the production tool/mixture/backing construction
against a support drum 150, such that the mixture wets the first
major surface 143 of the substrate 142. The production tool 82 is
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 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. After the binder precursor is at least
partially cured, the shaped, handleable structure 162 is 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 a between the shaped,
handleable structure 162 and the production tool 82 immediately
after passing over roller 165 is preferably steep, e.g., in excess
of 30.degree., in order to bring about clean separation of the
shaped, handleable structure 162 from the production tool 82. 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. 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 source to form the coated abrasive
article.
[0145] 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.
[0146] In either embodiment, it is often desired to completely fill
the space between the contacting 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 production tool rather than coating the slurry into
the production tool and contacting the slurry with the
substrate.
[0147] In a preferred method of this embodiment, the radiation
energy is transmitted through the production tool 82 and directly
into the mixture. It is preferred that the 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 preferred 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 sufficient ultraviolet or visible radiation, respectively,
to bring about the desired level of cure. Alternatively, the
substrate 112 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.
[0148] 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 the source of radiation can be
operated at relatively higher velocities. In short, the appropriate
velocity for the production tool depends on the material from which
the production tool is made. The substrate to which the composite
abrasive is bonded should 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
deleteriously affect the substrate or the production tool.
Substrate speeds of from 15 to 76 meters/min. (50 to 250 feet/min.)
have been found advantageous, however other speeds are also within
the scope of the invention.
[0149] A preferred embodiment of an abrasive article 200 provided
in accordance with the above-described method is illustrated in
FIGS. 24 and 25. 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 illustrated in FIG. 25,
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.
[0150] Further details on making structured abrasives are found in
WIPO International Patent Application Publication Number WO
97/12727, published on Apr. 10, 1997, "Method and Apparatus for
Knurling a Workpiece, Method of Molding an Article With Such
Workpiece, and Such Molded Article," Hoopman et al., the entire
disclosure of which is incorporated herein.
[0151] 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 form abrasive
composites; c) removing the abrasive composites from the production
tool; and d) converting the abrasive composites into composite
particles. These abrasive composite particles can be used in bonded
abrasives, coated abrasives, and nonwoven abrasives. This method is
described in greater detail in U.S. Pat. No. 5,549,962, "Precisely
Shaped Particles and Method of Making the Same," Holmes et al., the
entire disclosure of which is incorporated herein by reference.
[0152] The present invention has now been described with reference
to several embodiments thereof. The foregoing detailed description
and examples have been given for clarity of understanding only. No
unnecessary limitations are to be understood 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
the invention. 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 language of the
claims, and the equivalents of those structures.
* * * * *