Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROU~D OF ~HE I~VENTION
;
The inYention relates to a method and apparatus for
the preparatlon o~ multiple gauge metal strip by a shaving
operation whereln the strlp ls drawn through t~e shaving
apparatus over an arced surface.
It ls necessary to provide a multlple gauge thlckness
in a metal strlp ln many applicatlons such as the production
of copper strlp ~or the formatlon o~ electrical conductors
and the like. Con~entional procedures such as continuous
mllllng have been employed to ~roduce the desired variations
in gauge, however, such processes suffer ~rom the
disadvantages of being both time consuming as well as
generating an un~avorable ~orm of scrap.
An addItlonal procedure which has been known in the
art to produce multiple gauge metal strip comprises the
reduction to gauge by a rolling operation. However, the
rolling operatlon in the production of multiple gauge
strip has been ~ound to suffer from the dlsadvantages of
being restrlcted to certain shapes, and furthermore tend
to involve complex and costly tooling. Addltionally~ it
has been found that the product produced by the a~oresaid
rolling process ~ails to meet commercial tolerances as
well as belng free from other structural defects.
A further method of produclng multiple gauge metal
strip ls by a drawing process, Xowe~er, certain
complications resulted from this process, In the normal
dra~ing process reduction o~ the thickness in a section
results in an lncrease in section length so that if the
thlckness of a giYen shape varies across its wid'h, ~he
drawing process will result in variable changes In length
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causlng non-unlform metal floN and stresses leadln~ to
buckllng, t~istlng, tearing and fracture of thè workplece.
Though a wide variety of drawing technlques are known,
lncluding the employment of the hydrodynamlc prlnc~ple,
none have been suggested or would appear to allevlate the
aforenoted deflciencies associated with the drawlng of
complex multlple gauge conflguratlons.
The technlque of shavlng as a form of metal reductlon
has been known in the art for some time~ However, lts
application has been generally limlted to the ~lnishing
of materials of uniform cross sectlon by the reduction of
the cross sectional area of the workpiece, with the
reduction being conducted along the entire surface thereo~.
Thls technique is illustrated ln U.S. Patent 3,055,102 to
Shaw et al, wherein a shavlng tool is applled agalnst a
rod or bar which reduces the cross ~ectional area along the
entire surface thereof.
Certaln problems would appear to arise if this shaving
technlque exemplified by Shaw et al; were to be directly ~
applied to the productlon of multlple gauge strlp products ~ -
~rom rectangular stock. Speclfically, the application of
shaving force against only a portion of the total surface
o~ the strlp tends to magnlfy the problems set ~orth in
the aforenoted patent, particularly, the inability to hold
the workpiece properly centered wlth respect to the tool
Nlth the result that the workpiece wanders and a wavy or
broken surrace may re~ult. A further dlfflculty which
would arlse and be magnified ~y the removal o~ stock from
only a portion of the workpiece surface would be the
e~cessive c~atterlng that takes place as the strip would
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-pass through the tool which would appear on the flnished
product as a torn or galled surface.
One known method of producing multipl~ gauge strip
by draw shaving is illustrated in U. s. Patent 3,992,977,
issued November 23, 1976, to Winter et al and assigned to the
assignee of the present invention. The method and apparatus
for producing multiple gauge metal strip in the aforesaid
U. S. Patent while found to be superior to previously known
methods still wa~ found to suffer from deficiencies. More
particularly, the rake angle at which the tool was disposed
was found to be limited to a range of 2-1/2 to about 25
and was preferably about 5 to 18. Any increase in rake
angle above those critical values would cau~e the workpiece
to ride up the tool resulting in excessive strip material
being removed, Thus, as a result of the limit on rake angle,
the amount of volume removed per pass was also limited.
Furthermor~, the manner in which the tool was held in
position with respect to the anvil and strip was found to
produce chatter marks on the shaved portion of the multiple
strip product not unlike those chatter marks encountered in
the aforesaid machining operations. The chatter marks are
undesirable for functional reasons as well as cosmetic reasons.
Chatter marks on the metal ~trip impedes the bonding of semi-
conductor chip~ to the strip as well as inhibiting the metal
plating of the ~trip which may be necessary in the production
o~ electrical conductors and the like. The shaved gauge vari-
ation of the qtrip was found to be 1 0.002" while variations
in the transverse positioning of the cut groove were 0.005".
Finally, the finished multiple gauge strip product was
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observed to have signi~icant scratching on the backside
thereof as a result of being drawn over the flat anvil du~ing
the shavlng process. Furthermore, the shape of the ~inal
product exhlbited an lncrease in cross-wise dish with a
corresponding increase in cut depth and/or width. ~his
cross-wise dlsh can be attributed to the insufficient
hold-down forces of the strip against the flat anvil.
SUMMARY OF THE INVENTION
In accordance with the present invention, it has been
found that a shaving operation for the productlon of
multiple gauge strip products may be conducted wherein
the strip is drawn through the shaving apparatus over an
arced surface thereby allowing an increase in rake angle
while at the same time minimizlng cross-wlse dish in the
final product. The improved apparatus of the present
invention includes an improved support structure for
rigidly fixing the cutting tool's position with respect
to the arced surface and strip thereby improving shaved
gauge tolerances while reducing chatter marks.
The features of the present invention ccmprise the provision of
an arced surface of polished carbide which el~nates backside scratches
and thereby not only improves the cosmetic ~lities of the multiple
gauge strip product but also reduces the shaving stresses. The
employment of an arced sur~ace allows the tool's rake angle to be
increased to a range of from 20 to about 45 thereby resulting in a
corresponding decrease in relative shaving stress. Since the shaving
stress is directly re~ted to the volume of material which can be
removed per pass withDut exceeding the yleld strength of the mater~
the increase in rake angle allows greater volume removal per pass.
Fhrthermore, with an arced surface~ the strip can be caused to wrap
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around the surface thereby providing ef~ective hold-down
of the strip against the surface, this ability to wrap
around the surface results in a reduction in cross-wlse
dis~. By providing strip guides on the arced surface, the width
variations of the shaved surface are improved.
A further feature of this invention contemplates an
improved support component for rigidly fixing the tool's
pos$tion with respect to the arced surface and strip thereby
eliminating ~hatter marks while improving gauge depth tolerances.
~he method of this invention possesses certain
advantages over conventional milling procedures in that
scrap retrieval is made easier as the removed stock is
usually obtalned in the form of a long continuous coil whereas
the ~crap generated by conventional milling is in discontinuous chips of
random ~hapes and sizes. The method of the present lnvention
also exhibits advantages over previously known draw shaving
processes for multiple gauge strip in that the tolerances
of the shaved surface are lmproved, cross-wise dish is
minlmized, backside scratching i5 greatly eliminated, and
by the increase in allowable rake angle o~ the tool the
volume of material capable of being removed per pass is greatly
increaqed.
It is, accordingly, a principal obJect of the present
invention to produce an improved method for the manufacture
o~ multiple gauge metal strip products which employs an improved
shaving operation~
It is another ob~ect of the present invention to provide a
method and apparatus as aforesaid which will increase the volume of
metal reval pe~ pass.
It Is a ~urther obJect of the present inven~ion to provide an
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apparatus for the performance of the shaving method as afore- -
said which improveA the tolerances obtained in the ~haved
surface of the multiple gauge metal strip.
Still another object of the present invention i~
to produce a multiple gauge metal ~trip in which chatter marks
are greatly reduced.
In accordance with a specific embodiment, a method
for the production of a multiple gauge metal strip having at
least two longitudinal region~ of different thicknes~es form-
ing a generally stepped surface includes the steps of provid-
ing shaving means having an elongated cutting edge and anvil
means having an arced surface, adjusting and maintaining said
shaving mean~ at a position opposed to and ~paced from said
anvil means to form a shaving gap, said adjusting and maintain-
ing step including fastening said shaving mean~ to an assembly
comprising a horizontal member and vertical legs attached
thereto, ~eating said assembly on gauge blocks of selected
heiqht, maintaining the assembly at the desired shaving gap
by the application of downward pressure on said a~sem~ly and
drawing a metal strip through said gap in contact with said
shaving means and said arced surface, thereby ~having said
~trip to form a multiple gauge metal strip product.
An apparatu~ for the production of such multigauge
strip material in accordance wlth the invention comprises a
tool holder a~embly, said tool holder assembly including a
horizontal member having spaced vertical legs depending there-
from, a shav~ng tool having an elongated cutting edge, said
shavlng t~ol being located between ~aid legs and being supported
by said tool holder assembly, a base, an anvil having an arced
surface supported on said base, said tool holder assembly
being aupported on said base and ~aid shaving tool being located
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opposed to and adjacent the arced surface of ~aid anvil, means
for vertically adjusting and maintaining ~aid tool holder
assembly at a predetermined height to provide a desired shaving
gap between the cutting edge of said shaving tool and the
arced metal strip can be shaved from a thicker strip drawn
between the anvil and the shaving tool.
Other objects and advantage~ will become apparent by
those ~killed in the art from a consideration of the description
which proceeds with reference to the following drawing3.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1-3 are various views of the shaving apparatu~
employed in accordance with the present invention.
DETAILED D~SCRIPTION
In accordance with the present invention, the fore-
going objecta and advantages are readily obtained.
Shaving i8 a metal removal process akin to machining
or broaching, and utilizeq a stationary cutting tool and a
moving workpiece. As in any cutting operation, such variables
as speed, tool geometry, stock removal and lubrication are
important, however, unlike most metal cutting, the amount of
stock removal achieved in a ~having operation is co4trolled
by the maximum force which can be exerted on the strip before
yielding occur~. Essentially, this i~ the same kind of re-
straint impoaed on a wire drawing operation. The limiting
force iq, therefore, equal to the yield strength of the strip
multiplied by tho strip cross aectional area after shaving.
~hla may be expressed as follows:
FmaX = Y.S. (AF)
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Where,
FmaX is the l~mited ~orce;
Y.S. is the yield streng~h; and
AF Is the strlp cross sectional area after shaving.
Another relationship observed is that the ~orce required
to remove a given cross sectional area of strip by a shaving
operation is equal to the cross sectional area of the
shavlng cut multiplied by a machinlng or shaving constant,
C. Thls relationship may be expressed as an equation which,
when solved for C, is as follows:
C - F
Where,
F ls the drawing force;
Ar is the cross sectional area removed by shaving; and
C is the shaving constant.
It has been found in accordance with this invention
that the successful preparation o~ multiple gauge strip
may be accomplis~ed by a shaving operation if the maximum
amount of metal removal per shaving pass is determined in
relation to the yield strength of the strip and the shaving
constant, C, determined above. This relationship is
inferred from the observation that, as the drawing force
is increased, a maximum force is ultimatel~ reached which
corresponds to the yield strength of the strip. Thus, at
this point F ~ Fma2, and, by su~stitution the following
e~pression is derived;
Maximum Stock Remo~al G~l: Ar _``
Ao i ~ C/Y.S.
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~ere,
Ao i~ the initial cross;sectional area of the strip;
Ar is the cross sectlonal area removed by shavIng;
C is the s~aving constant; and
Y.S. is the yleld strength of the strip.
Thus, by the a~ove equation the maximum stock removal
per pass by shaving may be calculated by determining the
shaving constant and the yield strength of the strip. The
shaving constant can be calculated from experimental
measurements of drawlng force which may then be substituted
lnto the expression C 5 F/Ar, set forth earlier. The yield
strength of the strip is determlned by normal tensile
testing methods such as the 0.2% of~set yleld strength
method which was used hereln.
Upon determlning the maximum stock removal in accordance
wlth the procedure~ set forth above, the shaving apparatus
can then be ad~usted so as not to exceed the maximum value.
Such an ad~ustment wlll, o~ course, vary wlth the nature of
the apparatu~ employed. For example, in the present invention,~
the apparatus for ad~usting tool depth comprises an upside
down U-shaped housing whlch is posltioned on readily
replaceable gauge blocks. Ad~ustment of tool depth is made
by employing various size gauge blocks.
Another conventlonal parameter which influences the
successful practlce of the shavlng met~od of this invention
ls t~e determination o~ the shaving tool rake angle. The
rake angle is defined as the angle which the plane of the
vertlcal leading surface o~ the tool defines with respect to the
imaginary vertical plane perpendicular to the direction of strip traveL
3Q In cuttlng operations such as the method of this invention, it
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is usually ~ound that a certain critical rake angle exists
which, if exceeded, results in a loss o~ control of the
thickness of the finished workpiece. Usually, a rake angle
in excess o~ the critical value causes the workpiece to
ride up the tool, with the result that excessive stock is
removed.
The shaving apparatus employed in accordance with the
present inventlon comprises an adJustable shavlng tool
provided ~ith a cutting edge de~ining a pattern corresponding
to the multiple gauge surface desired in the final strip
product. The shaving tool is horizontally and vertically
ad~ustable to ena~le shaving to ~e conducted to successfully
achieve maximum possi~le strip reductions measured
primaril~ in terms of volume removal. As noted above,
maxlmum volume removal per shaving pass may be generally
determined in relation to the yleld strength o~ the strip
and then coordinated with the cross sectional con~iguration
o~ the desired end product. Thls ~eing done, the apparatus
ls then appropriately ad~usted to achieve the extent o~
volume removal desired. The various embodiments o~ the
apparatus employed in the present invention will be
descrl~ed in greater detail herein~elow.
Re~erring to Figure 1, a shaving apparatus used in
accordance with the present invention is illustrated in
perspective. The apparatus lQ comprises a shaving tool 12
located ad~acent and on a metal strip 14 which is ~eing
drawn across arced anvil 16. The cutting edge 18 o~ the
shaving tool 12 de~ines a cutting pattern whose con~igur-
atlon serves as the template for the final configuration o~
the multiple gauge strip product. Attached to the arced
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anvil 16 for guiding the metal strip 14 are a pair o~ strip
guides 22 which are symmetrically positioned about the
center line of the polygauge strip and spaced apart from
each other the width of strip 14. The guides 22 are
securely fixed to the anvil 16 by means of bolts 24 or
other suitable means. The strip guides should be manufactured of a
wear resistant material such as high speed tool steel so as to limit
wear which may occur because of the relatlve motion between
the strip 14 and the guldes 22. The arced anvll 16 may be
provided with a polished carbide insert 26 under the contact area of
the tool which is secured by bolts 28 as well as by strip guides 22.
The carbide insert may be secured to the anvll by other
means such as brazing, adhesives or the like. Alternately,
the arced anvil itselfcculd be made of polished carbide. The
radius of curvature of the arced anvil is limited on the high side by
the ability to get the desired downward tensile force while
minimizing total contact length and on the low side by the tendency
to plastlcally deform the strip as it is drawn in tension over the
anvil. It has been found that a radius of curvature
from about 1 to about 12" is satisfactory, preferably from about
2 to 8".
As shown In Figure 1, the shaving tool 12 ls supported by and
secured to an ad~ustable tool holder 30 comprising tool support
structure 32 which is secured to vertically ad~ustable housing 34.
Housing 34 is an upside down U-shaped structure comprising vertical
legs 36 which are integral with connecting horizontal member
38. Shaving tool 12 is secured in the manner shown by support struc-
ture 32 which in turn is integral with the ~-shaped housing 34 so
as to allow the entire ad~ustable tool holder assembly 30
to move vertically as a whole. The adjusta~le tool holder
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as~embly 3~ is adapted for horizontal and vertical movement
on tracks 40 and 41 in any convenient manner kncwn in the prior
art for example, a screw tra~el slide connection, a slldlng
Jack arrangement, by manual means, or any other suitable
means. The ~ u-stable too~ ho-l&er assembly ~
30 rests on gauge blocks 42 which are readily capable of
belng replaced ~y gauge blocks of varying thic~nesses.
The tool holder assembly 30 is held in lts approprlate
vertlcal posltlon against the gauge blocks 42 by providing
an approprlate vertical load on the horizontal member 38.
This vertical load may be in the form of simple weights or
alternately hydraulic, pneumatic, or other suitable means ~or
insuring that the assembly remains rigidly fixed with respect -
to the anvil and strip. As is clear, flne ad~u~tments of
the vertical position can be made by replacing the
gauge ~locks with other gauge blocks of suitable dimensions.
As stated above, maximum stock removal is determined
with respect to the yield strength of the strip and the
particular configuration desired. In addition to the
aforenoted ad~ustments of the vertical position of the
shaving tool, a ~urther critical ad~ustment is made which
relates to the rake angle of the tool edge. The rake angle
is defined a~ the angle which the plane of the vertical
leading surface of the tool defines with respect to the
imaginary vertical plane perpendicular to the directlon of
strip travel. In accordance ~ith the present invention, it
has been found that the critical rake angle at ~hich the
cutting tool may be dispo~ed is greatly increased o~er that
of U.S. Patent 3,292,977. Thè rake angle foùnd to be useful
in the aforesaid U.S. Patent was from about 2-1/2 to about
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25 and pre~erabl~ from about 5 to about 18, In t~e
present lnventlon, it has been found that as a result of
the employment of an arced anvil, a rake angle as high as
45 may be employed without causing t~e strip to ride up
the cutting tool. T~ls increase in rake angle is attributed
to an increase ~n effective hold-down of the strip against
the anvil as a result of the anvll being arced which causes
the strip to wrap around said anvil. In addition, the
employment of h~l~dle rolls ~not shown) ahead of and behind
the arced anvil sur~ace may also be ~u~d to thereby
provide additional hold-down forces of the strip against the
anvil. Lncreasing thetool's rake angle from the previously
defined range, as indicated in U.S. Patent 3,992,977, to
that range which i~ capable o~ being attained in the present
invention results in a reduced shaving stress and improved
strip cosmetics. The improvement in the shaved surface
finlsh results from the fact that an increase in rake angle
results in a correspondlng decrease of the bullt-up material
ad~acent to thetool's face. Increasing the rake angle also
results in substantial reductions in shaving stress and
consequently, a greater amount of materlal can be removed
per pass than was previously ~ossible.
The improved ad~ustable tool holder assembly results in
improved shaved gauge tolerances over those realized in
aforesaid U,S. Patent 3,922,277, as a re~lt of t~ use o~
a Yertica'ly loaded tool holder against precision machined
gauge blocks and rigidly fixing the position of t~e anvil,
strip and tool with respect to each ot~er by applying said
vertlcal load T~e shaYed gauge variation ~as reduced from
+ 0.002t', as stated in the aforesaid patent, to + 0.0005". In
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addltion, t.he.'employment. of strip guides on the anvil has ~.
allowed rariations ln the transverse positioning of the '
cut groove to 6e reduced from'0.005" to 0.001". In addition,
providing a polished car~ide anvil or insert therefor, . .
backslde scratches of the polygauge strip were substantially
reduced ~rom that of the previously known.method while .
correspondingly effecting a reductlon in shaving stress.
The totality of the modifications of the present :
invention, i.e., increasing tool rigidity, providing an .
arced anvil? strip guides, and polished carbide lnserts,
results in lmproved surface finish of the shaved portion,
reduced ~ackside scratching, elimination o~ chatter marks
on the shaved portion, and improved shaving efficiencies
by allowing a greater removal of material per pass.
While the above shaving apparatus ha~ been employed
with an arced anvll, it should be appreciated that a ~reely
rotating wheel may be su~stituted for the arced anvil and
stlll effect the improvements of the present invention. In
addltlon, the employment of a freely rotating wheel would
tend to reduce frictional contact between the metal strip
and the corresponding arced surface. Again,bridle rolls
ahead o~ and traili~.g the rotating wheel will allow the
strip to more ef~ectlvely wrap around the wheel and thereby
provide better hold-do~n of the strip thereon.
The follo~ing e~ample is pre.sented in order to gain a
fuller understanding of the method and apparatus of this
Invention and to illustrate the advantages obtained there- ~
~rom. The. e~'ample is presented for the purpose of illustra- :.
tion onl~ and should not be construed as a limitation on
the invent.lon. :.
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Flve samples o~ 1/8 hard CDA Alloy 128 where prepared
for draw shaving. An apparatus was employed for the draw
shaving which comprised a shaving tool in accordance with
t~e present invention. The alloy samples comprised flat
riabons of strip measuring 0.906" by 0.080". The 0.2%
yield strength of the material was 22 ksi while the ultimate
tensile strength was 36 ksi. The cutting tool width was
.a62" and the tool was set to cut a shaving depth of
0.007". Five samples were shaved in accordance with the
present invention with the cutting tool set at a rake angle
varying from 8 to 44, The radius of the arced anvil
was 3". The drawing force, F, was measured for each
test and the relative shaving stress was calculated using
the aforenoted formula. The results of the experiment are
set forth ~elo~ in Table I.
TAEL~ I
Rake Angle (Degrees~ Relatlve Shaving Stress ~ksl)
8 1200
850
28 650
36 450
44 400
Based on the data in Table I, and the mathematical
relations~ip bet~een percent stock removed and shaving
stress, it can be seen t~at a product fabricated with
three passes using an 8 ~ake angle tool would only
require one pass i~ the rake angle of the tool was set at
44. As noted previously, t~Is effective increase in
allowable rake angle is directly attributed to the excellent
3o hold-down ~orce on the strip w~ich occurs as the result of
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the employment of an arced surface over which the strip
passes
It is to be understood that the invention is not
limited to the illustrations described and shown herein, :
which are deemed to be merely illustrative of the best
modes of carrying out the invention, and which are suscep-
tible of modification of form, size, arrangement of parts
and details of operation. ~he invention rather is intended
to encompass all such modifications which are within its
splrlt and scope as deflned by the clalms.
