U.S. patent application number 13/550184 was filed with the patent office on 2013-01-10 for chatter-resistant end mill and method of making.
Invention is credited to SERGEI BOULAKHOV, VLADIMIR GALIPKO, LEONID SHARIVKER, VLADIMIR VOLOKH, SHAY ZEIDNER.
Application Number | 20130008004 13/550184 |
Document ID | / |
Family ID | 39033375 |
Filed Date | 2013-01-10 |
United States Patent
Application |
20130008004 |
Kind Code |
A1 |
VOLOKH; VLADIMIR ; et
al. |
January 10, 2013 |
CHATTER-RESISTANT END MILL AND METHOD OF MAKING
Abstract
A method of making chatter-resistant end mills includes: (a)
forming an end mill having unequal angular spacing between adjacent
teeth, (b) cutting a test work piece with the end mill and
measuring vibrations and resonance; (c) upon detecting undesired
levels of vibration and resonance, adjusting the angular spacing
between adjacent teeth to reduce vibration and resonance and
forming another end mill having the adjusted angular spacing; (d)
cutting a test work piece with the adjusted end mill and measuring
vibrations and resonance; (e) repeating steps (c) and (d) until an
end mill is formed in which vibration produced by the angular
spacing between at least one pair of adjacent teeth cancels out at
least a portion of the vibration produced by the angular spacing
between at least one other pair of adjacent teeth; and (f) making
at least one production end mill conforming to step (e).
Inventors: |
VOLOKH; VLADIMIR; (Ma'alot,
IL) ; BOULAKHOV; SERGEI; (Nahariya, IL) ;
SHARIVKER; LEONID; (Nahariya, IL) ; ZEIDNER;
SHAY; (Cabri, IL) ; GALIPKO; VLADIMIR;
(Nahariya, IL) |
Family ID: |
39033375 |
Appl. No.: |
13/550184 |
Filed: |
July 16, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12376590 |
Jul 21, 2009 |
8221036 |
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PCT/IL2007/000978 |
Aug 6, 2007 |
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13550184 |
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Current U.S.
Class: |
29/407.07 |
Current CPC
Class: |
B23P 15/34 20130101;
B23C 5/003 20130101; B23C 2210/0492 20130101; Y10T 407/1948
20150115; Y10T 407/1962 20150115; B23C 2210/282 20130101; B23C
2210/205 20130101; Y10T 29/49774 20150115; B23C 2210/207 20130101;
B23C 5/10 20130101; B23C 2210/204 20130101; Y10T 407/1966
20150115 |
Class at
Publication: |
29/407.07 |
International
Class: |
B23P 15/34 20060101
B23P015/34 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2006 |
IL |
177336 |
Claims
1-11. (canceled)
12. A method of making chatter-resistant end mills comprising the
steps of: (a) forming an end mill having unequal angular spacing
between adjacent teeth, wherein vibrations produced by the angular
spacing between at least one pair of adjacent teeth is configured
to cancel out at least a portion of the vibration produced by the
angular spacing between at least one other pair of adjacent teeth;
(b) cutting a test work piece with the end mill and measuring
vibrations and resonance caused by the angular spacing between
adjacent teeth; (c) upon detecting undesired levels of vibration
and resonance, adjusting the angular spacing between adjacent teeth
to reduce vibration and resonance and forming another end mill
having the adjusted angular spacing; (d) cutting a test work piece
with the adjusted end mill and measuring vibrations and resonance
caused by the adjusted angular spacing between adjacent teeth; (e)
repeating steps (c) and (d) until an end mill is formed in which
vibration produced by the angular spacing between at least one pair
of adjacent teeth cancels out at least a portion of the vibration
produced by the angular spacing between at least one other pair of
adjacent teeth; and (f) making at least one production end mill
conforming to the end mill produced according to step (e).
13. The method as claimed in claim 12, wherein the difference
between said first and said second angles is in the range of 0.2-60
degrees.
14. The method as claimed in claim 12, wherein the difference
between said first and said second angles is in the range of 0.2-30
degrees.
15. The method as claimed in claim 12, wherein the width and depth
of all flutes in said cutting portion is equal.
16. The method as claimed in claim 12, wherein a flute is disposed
between two adjacent teeth, said adjacent teeth being spaced apart
at an angle exceeding the angle which would result from equal
angular spacing, said flute being wider and deeper than a second
flute appropriate to an equally-spaced pair of adjacent teeth.
17. The method as claimed in claim 12, wherein a flute is disposed
between two adjacent teeth, said adjacent teeth being spaced apart
at an angle less the angle which would result from equal angular
spacing, said flute being narrower and shallower than a second
flute appropriate to an equally-spaced pair of adjacent teeth.
18. The method as claimed in claim 12, wherein the tool has a
constant flute helix angle in each tooth and a constant flute helix
angle from tooth to tooth.
19. The method as claimed in claim 12, wherein the tool has a
variable flute helix angle from low to high in each tooth and the
same variability of flute helix angle from tooth to tooth.
20. The method as claimed in claim 12, wherein the tool has a
variable flute helix angle from high to low in each tooth and the
same variability of flute helix angle from tooth to tooth.
21. The method as claimed in claim 12, wherein at least one group
of said cutting edges is displaced from the equally-spaced position
and at least one further group has cutting edges positioned in an
equally-spaced configuration.
22. A method of making chatter-resistant end mills, said method
comprising the steps of: (a) forming an end mill having unequal
angular spacing between adjacent teeth, wherein vibration produced
by the angular spacing between at least one pair of adjacent teeth
is configured to cancel out at least a portion of the vibration
produced by the angular spacing between at least one other pair of
adjacent teeth; (b) cutting a test work piece with the end mill and
measuring vibrations and resonance caused by the angular spacing
between adjacent teeth; (c) upon detecting undesired levels of
vibration and resonance, adjusting the angular spacing between
adjacent teeth to reduce vibration and resonance and forming
another end mill having the adjusted angular spacing; (d) cutting a
test work piece with the adjusted end mill and measuring vibrations
and resonance caused by the adjusted angular spacing between
adjacent teeth; (e) repeating steps (c) and (d) until an end mill
is formed in which vibration produced by the angular spacing
between at least one pair of adjacent teeth cancels out at least a
portion of the vibration produced by the angular spacing between at
least one other pair of adjacent teeth; and (f) making at least one
production end mill conforming to the end mill produced according
to step (e).
23. The method as claimed in claim 22, wherein said method further
comprises forming an end mill in which the difference between the
angular spacing of at least two pairs of adjacent teeth is in the
range of 0.2-60 degrees.
24. The method as claimed in claim 22, wherein said method further
comprises forming an end mill in which the difference between the
angular spacing of at least two pairs of adjacent teeth is in the
range of 0.2-30 degrees.
25. The method as claimed in claim 22, wherein said method further
comprises forming an end mill in which the width and depth of all
flutes in a cutting portion of the end mill is equal.
26. The method as claimed in claim 22, wherein said method further
comprises forming an end mill in which a flute is disposed between
two adjacent teeth, said adjacent teeth being spaced apart at an
angle exceeding the angle which would result from equal angular
spacing, said flute being wider and deeper than a second flute
appropriate to an equally-spaced pair of adjacent teeth.
27. The method as claimed in claim 22, wherein said method further
comprises forming an end mill in which a flute is disposed between
two adjacent teeth, said adjacent teeth being spaced apart at an
angle less the angle which would result from equal angular spacing,
said flute being narrow and shallow than a second flute appropriate
to an equally-spaced pair of adjacent teeth.
28. The method as claimed in claim 22, wherein said method further
comprises forming an end mill which has a constant flute helix
angle in each tooth and a constant flute helix angle from tooth to
tooth.
29. The method as claimed in claim 22, wherein said method further
comprises forming an end mill which has a variable flute helix
angle from low to high in each tooth and the same variability of
flute helix angle from tooth to tooth.
30. The method as claimed in claim 22, wherein said method further
comprises forming an end mill which has a variable flute helix
angle from high to low in each tooth and same variability of flute
helix angle from tooth to tooth.
31. The method as claimed in claim 22, wherein at least one group
of said cutting edges is displaced from the equally-spaced position
and at least one further group has cutting edges positioned in an
equally-spaced configuration.
Description
BACKGROUND
[0001] The present application relates to milling cutters. More
particularly, there is provided an end mill configured to
substantially reduce or eliminate vibrations of the cutter itself
and of the work piece.
[0002] The milling process is by its very nature a non-continuous
form of machining. A wide range of cutters are available "off the
shelf," and it is up to the user to select the type required. The
cutter used may have up to about 20-30 teeth, depending primarily
upon the diameter of the cutter and its type, and on further
factors, such as the material of which the cutter is constructed,
the material of the work piece, whether the cutting operation is
for finishing or roughing, the required or desired cutter life, and
the like.
[0003] As can be expected from any non-continuous type of
machining, vibrations are generated by milling, and such vibrations
may range in amplitude from negligible to severe. During machining
with an end mill, the tool is generally subject to both bending and
torsional forces, these being of an intermittent nature due to a
tooth contacting or ceasing to contact the face being machined. As
those visiting a working machine shop are aware, these vibrations
generate sounds which are in frequencies and amplitudes to which
the human ear is sensitive.
[0004] The work piece being machined is also set into vibration,
the nature of which will be significant for a large hollow item and
will be of no consequence for a solid well-supported and securely
clamped work piece.
[0005] Noticeable vibration, sometimes referred to as chattering,
is detrimental to machining not only because of the generated
noise. Such vibrations are directly responsible for a poor surface
finish on the work piece, as well as for a shortening of the life
of the cutter and reduced accuracy in machining.
[0006] Undesired vibrations may be present in the cutting tool, or
in the work piece, and can be present in both.
[0007] A severe problem arises when the frequency of vibration of
the cutter corresponds or is proximate to the natural frequency of
the work piece, causing resonance. The resulting greatly increased
amplitude makes it impossible to produce acceptable work and the
generated sound can be most disturbing. Breakage of a cutter such
as an end mill or spoilage of the work piece is also likely. The
use of a more rigid cutter and the application of additional work
piece supports would increase vibration frequency to a safe and
non-audible level and greatly reduce amplitude, but these desirable
steps are not always possible.
[0008] Increasing the cutter speed is also often impractical
because tool life will be substantially shortened in practice.
[0009] The use of helical-tooth end mills, similarly to helical
gearing, is helpful in abating but not solving these problems.
[0010] The state of the prior art can be assessed from a review of
relevant U.S. Patents.
[0011] In U.S. Pat. No. 4,285,618, Stanley, Jr. claims a milling
cutter shown as an end mill provided with serrations on the cutting
edges. The serrations are axially off-set in relation to a
neighboring tooth. Whether or not such a cutter will reduce
vibrations would need to be proved by tests.
[0012] In U.S. Pat. No. 4,963,059, Hiyama proposes an end mill
wherein the flute helix angle is not the same for each flute.
However, as the peripheral cutting edges are equally spaced around
the cutter periphery in at least one position, the proposed design
would provide only a partial solution. Also, a problem would arise
during manufacture of said end mill as the metal available for
formation of the tooth would vary significantly along the length of
the cutter.
[0013] In U.S. Pat. No. 6,168,355, Wardell describes an end mill
having a main body and ears extending outward from the point of the
tool. Means for reducing vibration are not provided.
[0014] In U.S. Pat. No 6,164,877, Kamata et al. disclose a formed
shape cutter intended for cutting specially-shaped grooves. The
relief angle of the tooth remains constant along the axial length
of the tool. No anti-chatter means are seen.
[0015] Wardell, in a further U.S. Patent, discloses an end mill
having a primary helical flute defining a low-angle cutting surface
and a secondary flute for a high angle cutting surface. This
arrangement will not solve the problems relating to tool
vibrations.
[0016] A further end mill having a variable helix flute is seen in
published U.S. Patent Application 2005/0105973 by MacArthur. The
teeth of the cutter are equally spaced around the tool
periphery.
[0017] From the prior art it is evident that no satisfactory
solution is yet known.
OBJECT
[0018] It is therefore one of the objects of at least one
embodiment to obviate the disadvantages of prior art cutters and to
provide an end mill which will eliminate or substantially reduce
periodic vibrations which are detrimental to both the tool and the
work piece.
[0019] It is a further object of at least one embodiment to
disclose a tool design which can be easily programmed for
manufacture, and can be manufactured at a cost only slightly higher
than a conventional end mill.
SUMMARY
[0020] The above objects may be achieved in at least one embodiment
of a chatter-resistant end mill, shell mills and burs comprising a
shank portion and at least one cutting portion divided into a
plurality of teeth by flutes disposed between said teeth, each
tooth having at least one cutting edge, and wherein a first angle
separating said cutting edge of a first tooth from the cutting edge
of a tooth nearest the first tooth in a clockwise direction is
different from a second angle separating said cutting edge of said
first tooth from the cutting edge of a tooth nearest the first
tooth in an anti-clockwise or counterclockwise direction. For
example, in an embodiment having only two teeth, the first angle
separating the cutting edge of the first tooth from the cutting
edge of the second tooth (which is nearest the first tooth since
the second tooth is the only other tooth) in a clockwise direction
is different from a second angle separating the cutting edge of the
first tooth from the cutting edge of the second tooth in a
counterclockwise direction. In an embodiment having three or more
teeth, the first angle separating the cutting edge of a first tooth
from the cutting edge of a second tooth nearest the first tooth in
a clockwise direction is different from a second angle separating
the cutting edge of the first tooth from the cutting edge of a
third tooth nearest the first tooth in a counterclockwise
direction.
[0021] In one embodiment there is provided an end mill wherein the
difference between said first and said second angles is in the
range of 0.2-60 degrees.
[0022] In another embodiment there is provided an end mill wherein
the difference between said first and said second angles is in the
range of 0.2-30 degrees.
[0023] In another embodiment there is provided an end mill wherein
the width and depth of all flutes in said cutting portion is
equal.
[0024] In a further embodiment there is provided an end mill or
burs wherein a flute is disposed between two adjacent teeth, said
adjacent teeth being spaced apart at an angle exceeding the angle
which would result from equal angular spacing, said flute being
wider and deeper than a second flute appropriate to an
equally-spaced pair of adjacent teeth.
[0025] In yet another embodiment there is provided an end mill or
burs wherein a flute is disposed between two adjacent teeth, said
adjacent teeth being spaced apart at an angle less the angle which
would result from equal angular spacing, said flute being narrower
and shallower than a second flute appropriate to an equally-spaced
pair of adjacent teeth.
[0026] In a further embodiment there is provided an end mill, shell
mills and burs wherein the flute helix angle is constant along each
tooth and constant from tooth to tooth in the cutting part of the
end mills, shell mills and burs.
[0027] In a further embodiment there is provided an end mill, shell
mills and burs wherein the flute helix angle is variable along each
tooth and same from tooth to tooth in the cutting part of end
mills, shell mills and burs.
[0028] In yet a further embodiment there is provided an end mill
wherein at least one group of said cutting edges is displaced from
the equally-spaced position and at least one further group has
cutting edges positioned in an equally-spaced configuration.
[0029] It will thus be realized that the cutter of at least one
embodiment serves to break the regularity of the input force
causing the undesired vibration both in the end mill and in the
work piece. Resonance occurs when the natural frequency of the
cutter or of the work piece corresponds or is proximate to the
frequency of the induced vibration. The end mill of at least one
embodiment having irregularly spaced cutting surfaces will apply
the cutting force in an irregularly timed cycle, the result of
which is the inhibition of resonance, and greatly reduced vibration
at any frequency. Vibration control provides the desired benefits
of a better surface finish, longer tool life and, of course, less
noise.
[0030] Theoretical calculations of vibration frequencies for
cutters and work pieces are difficult, because of the complex form
of the tool and often also of the work piece and because the end
mill is stressed both torsionally and by bending forces.
Measurement of vibration while machining a test piece is however a
simple task. Furthermore, vibration input is easily calculated on
the basis of number of teeth and the speed (RPM) of the machine
spindle. Thus a simple test will indicate which tool diameter and
the benefits of uneven peripheral spacing of the teeth in at least
one embodiment are not limited to conditions of resonance. Whatever
the natural frequency, unwanted vibration is subdued by the uneven
peripheral positioning of the cutting edges. The reduction of
vibrations to minimum amplitude is a prerequisite for correct and
economic machining by any machine tool.
[0031] A prototype of a cutter made according to at least one
embodiment was tested with the following results:
[0032] Tools:
[0033] Solid Carbide End Mill Diameter 12 mm:
[0034] #1-5 flutes with unequal cutting edges space dividing
according to an embodiment.
[0035] #2-5 flutes with equal cutting edges space dividing.
[0036] Material: St. Steel 316 L,
[0037] Cutting Conditions:
[0038] Slotting Application: depth of cut-12 mm (1D)
TABLE-US-00001 Feed Speed m/min mm/t # of tools 50 60 70 80 90 0.05
#1 - Vibrations No No No No No 0.05 #2 - Vibrations Slow Medium
High High, High, Chipping Broken Speed Feed, mm/t m/min # of tools
0.03 0.04 0.05 0.06 0.07 80 #1 - Vibrations No No No No No 80 #2 -
Vibrations Slow High High, High, High, Chip- Broken Broken ping
[0039] Thus it was seen that the end mill according to at least one
embodiment achieved the stated objects:
[0040] 5 flutes Solid Carbide End Mills diameter 12 mm with unequal
cutting edges space dividing according to one embodiment prevent
vibration in wide range of the speeds: 50-90 m/min and feeds:
0.03-0.07 mm/teeth.
[0041] According to at least one possible embodiment, the spacing
between two teeth of a cutter or end mill is adjusted by experiment
to substantially or at least partially cancel out the vibration
which is caused by the spacing between other teeth. To further
explain by way of example, in an end mill with five cutting teeth,
each pair of adjacent teeth defines an angular measurement there
between. As discussed above, the angular measurements are not equal
for all five pairs of cutting teeth in order to substantially
reduce or eliminate resonance caused by vibrations. In order to
achieve such a substantial reduction or elimination of vibrations,
the spacing of the cutting teeth, and thus the angular measurement
there between, can be selected during design of the end mill for
each pair of teeth. If, for example, an angular spacing of at least
one pair of teeth is believed to have or actually has a canceling
effect on vibrations caused by a different angular spacing of
another pair of teeth for an end mill for a particular type of
machining, then the end mill could be designed accordingly. The end
mill could then be tested on a test work piece, wherein the
vibrations and/or resonance could be measured and observed to
determine the degree of the canceling effect. If the canceling
effect is not as desired, then the angular spacing could be
adjusted until the desired canceling effect is obtained. In this
manner, an end mill or cutter could be designed that does not just
vary the vibrations from cutting tooth to cutting tooth to avoid
resonance, but rather utilizes the vibrations caused by the spacing
of one or more pairs of teeth to at least partially cancel out, and
thus substantially reduce or eliminate, the vibrations caused by
the spacing of one or more other pairs of teeth. According to at
least one embodiment, the optimum or desired spacing which most
effectively cancels out vibrations could possibly be determined by
theoretical calculations, measurement of the frequencies, or a
combination thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] The embodiments will now be described further with reference
to the accompanying drawings, which represent exemplary
embodiments. Structural details are shown only as far as necessary
for a fundamental understanding thereof. The described examples,
together with the drawings, will make apparent to those skilled in
the art how further forms of the embodiments may be realized.
[0043] In the drawings:
[0044] FIG. 1 is an elevational view of an end mill according to at
least one embodiment;
[0045] FIG. 2 is an end view of a two-tooth end mill according to
at least one embodiment;
[0046] FIG. 3 is an end view of a five-tooth end mill according to
at least one embodiment;
[0047] FIG. 4 is an elevational view of an end mill according to at
least one embodiment, showing flute variation;
[0048] FIG. 4a is a diagram of 3-flute end mill with a constant
flute helix angle in each tooth and a constant flute helix angle
from tooth to tooth;
[0049] FIG. 4b is a diagram of 3-flute end mill with a variable
flute helix angle from low to high in each tooth and the same
variability of flute helix angle from tooth to tooth;
[0050] FIG. 4c is a diagram of 3-flute end mill with a variable
flute helix angle from high to low in each tooth and the same
variability of flute helix angle from tooth to tooth;
[0051] FIG. 5 is an end view of a six-tooth end mill according to
at least one embodiment; and
[0052] FIG. 6 is an end view of an eight-tooth end mill according
to at least one embodiment having two separate teeth off-set from
the equally-divided location and two groups of equally-spaced
teeth.
DETAILED DESCRIPTION OF THE DRAWINGS
[0053] There is seen in FIG. 1 a chatter-resistant end mill 10,
comprising a shank portion 12 for gripping by a machine tool.
Cutting portions 14, 16 are seen both on the side and the end face.
The cutting portion 14 is divided into four teeth 18 by four flutes
20 disposed between the teeth 18.
[0054] FIG. 2 shows a two-tooth end mill 22, and there is seen the
end cutting edge 24 of each tooth 18 at the cutting portion 16. A
first angle B and a second angle C separate the two cutting edges
24a of a first tooth 18a from the cutting edge 24b of the second
tooth. The difference between the angles A and B is about 30E in
the diagram but can be as high as 60E for end mills if desired. It
should be noted that A+B=360E.
[0055] With reference to the rest of the figures, similar reference
numerals have been used to identify similar parts.
[0056] FIG. 3 illustrates a five tooth end mill 26 wherein the
difference between the first and the second angles B, C is in the
range of 0.2-30 degrees. The smaller differential is suitable for
cutters having 5 teeth (or more) as seen in the figure. There are
two pairs B C of cutting edge irregular spacing and a single span A
which is the angle resulting from equal spacing, i.e. 72E in the
example seen. The same flute profile 28 is used for all teeth for
simplicity of manufacture.
[0057] Turning now to FIG. 4, there is depicted an end mill 30
showing different flutes 32, 34 disposed between cutting edges 36
of adjacent teeth 38. Adjacent teeth 38 are spaced apart at an
angle B exceeding the angle A which would result from equal angular
spacing, as seen in FIG. 3.
[0058] The flute 32 relating to angle B is wider and deeper than
the flute 34 relating to angle A, so as to improve coolant feed and
facilitate chip clearance and removal when teeth work with higher
feed per teeth compared to equal tooth space dividing (by angle
A).
[0059] FIG. 4a is a diagram of a 3-flute end mill with a constant
flute helix angle in each tooth and a constant flute helix angle
from tooth to tooth.
[0060] FIG. 4b is a diagram of a 3-flute end mill with a variable
flute helix angle from low to high in each tooth and the same
variability of flute helix angle from tooth to tooth.
[0061] FIG. 4c is a diagram of a 3-flute end mill with a variable
flute helix angle from high to low in each tooth and the same
variability of flute helix angle from tooth to tooth.
[0062] FIG. 5 shows a six-tooth end mill 40 wherein four of the
cutting edge spans A are equally spaced (A=60E) while the remaining
two spans B and C are irregular and in combination cover the
remaining 120E.
[0063] FIG. 6 illustrates an eight-tooth end mill 42. Two groups of
regular spans A alternate with two groups of irregular spaced teeth
B and C.
[0064] Other cutting tools and components thereof are disclosed in
the following U.S. Patents and published U.S. Patent Applications:
U.S. Pat. No. 6,991,409 to Noland; U.S. Pat. No. 4,497,600 to
Kishimoto; U.S. Pat. No. 4,963,059 to Hiyama; US 2005/0105973 to
MacArthur; US 2005/0084341 to Long, II et al.; and US 2005/0117982
to Dov et al. Another cutting tool is shown in a 2003 Kennametal
Inc. brochure no. HANO3040B. The preceding publications, as well as
all other publications mentioned herein, are hereby incorporated by
reference as if set forth in their entirety herein.
[0065] The scope of the described embodiments is intended to
include all embodiments coming within the meaning of the following
claims. The foregoing examples illustrate useful forms of an
embodiment or embodiments, but are not to be considered as limiting
the scope thereof, as those skilled in the art will be aware that
additional variants and modifications can readily be formulated
without departing from the meaning of the following claims.
* * * * *