U.S. patent application number 16/771990 was filed with the patent office on 2021-03-18 for milling tool and workpiece machining method.
This patent application is currently assigned to MAKINO MILLING MACHINE CO., LTD.. The applicant listed for this patent is MAKINO MILLING MACHINE CO., LTD.. Invention is credited to Ryoichi MIYAMOTO, Fukuhito NAGATA, Hiroshi UENO.
Application Number | 20210078086 16/771990 |
Document ID | / |
Family ID | 1000005299307 |
Filed Date | 2021-03-18 |
![](/patent/app/20210078086/US20210078086A1-20210318-D00000.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00001.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00002.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00003.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00004.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00005.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00006.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00007.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00008.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00009.png)
![](/patent/app/20210078086/US20210078086A1-20210318-D00010.png)
View All Diagrams
United States Patent
Application |
20210078086 |
Kind Code |
A1 |
UENO; Hiroshi ; et
al. |
March 18, 2021 |
MILLING TOOL AND WORKPIECE MACHINING METHOD
Abstract
A milling tool is configured from a shank part and a head with a
cutting edge that is provided on the leading end of the shank part.
The head comprises an expanding diameter section, the diameter of
which expands gradually from the base end that contacts the shank
part in the direction of the leading end, and a decreasing diameter
section, the diameter of which gradually decreases from the maximum
diameter section in the direction of the leading end. At least one
cutting edge is provided on each of the expanding diameter section
and the decreasing diameter section.
Inventors: |
UENO; Hiroshi;
(Fujiyoshida-shi, JP) ; MIYAMOTO; Ryoichi;
(Fujiyoshida-shi, JP) ; NAGATA; Fukuhito;
(Fujiyoshida-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAKINO MILLING MACHINE CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
MAKINO MILLING MACHINE CO.,
LTD.
Tokyo
JP
|
Family ID: |
1000005299307 |
Appl. No.: |
16/771990 |
Filed: |
December 13, 2017 |
PCT Filed: |
December 13, 2017 |
PCT NO: |
PCT/JP2017/044791 |
371 Date: |
June 11, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23C 3/13 20130101; B23C
5/10 20130101 |
International
Class: |
B23C 3/13 20060101
B23C003/13; B23C 5/10 20060101 B23C005/10 |
Claims
1. A milling tool composed of a shank part, and a head which is
provided on a distal end of the shank part and which has a cutting
edge, wherein the head has an expanding diameter section, the
diameter of which gradually increases along a direction from a
proximal end contiguous with the shank part toward a distal end,
and a decreasing diameter section, the diameter of which gradually
decreases along a direction from a maximum diameter section toward
the distal end, and cutting edges are provided on the expanding
diameter section and the decreasing diameter section.
2. The milling tool of claim 1, wherein at least one upper groove
is formed in the expanding diameter section, at least one lower
groove is formed in the decreasing diameter section, and a seat for
attachment of an insert forming the cutting edge is formed in each
of the at least one upper groove and the at least one lower
groove.
3. The milling tool of claim 2, wherein an upper seat is formed in
the upper groove, a lower seat is formed in the lower groove, an
upper insert is attached to the upper seat, and a lower insert is
attached to the lower seat.
4. The milling tool of claim 3, wherein the upper insert and the
lower insert each have a main cutting edge which linearly extends
from one end thereof and a convexly bent sub cutting edge which is
connected to the main cutting edge and which is arranged on the
other end of the upper inert or the lower insert, and the sub
cutting edges of the upper insert and the lower insert are arranged
so as to be adjacent to a joint of the expanding diameter section
and the decreasing diameter section.
5. The milling tool of claim 4, wherein a bottom cutting edge and
an inner cutting edge are formed on an edge of the lower insert on
the side opposite the sub cutting edge.
6. The milling tool of claim 2, wherein a seat extending from the
upper groove toward the lower groove is formed, and a V-shaped
insert is attached to the seat.
7. A workpiece machining method for undercutting interior portions
of a rib of a workpiece attached to a table of a machine tool and a
return flange formed contiguous with the rib, the method comprising
the steps of: attaching the milling tool of claim 1 to a spindle of
the machine tool and rotating the milling tool, and machining an
interior of the return flange with a cutting edge of the expanding
diameter section of the milling tool and machining a side surface
of the rib with a cutting edge of the decreasing diameter section
of the milling tool.
8. The workpiece machining method of claim 7, wherein the machine
tool is a five-axis machine tool having at least two rotary feed
axes, and a posture and position of the milling tool are controlled
relative to the workpiece to perform undercutting of a corner
portion at which ribs having return flanges intersect.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. national stage application under
35 USC 371 of International Patent Application No.
PCT/JP2017/044791, filed Dec. 13, 2017, the entire contents of
which are incorporated herein by reference.
FIELD OF THE DISCLOSURE
[0002] The present invention relates to a milling tool and
workpiece machining method which are capable of machining an
undercut part such as a rib having a return flange with high
efficiency and high accuracy.
BACKGROUND OF THE DISCLOSURE
[0003] Patent Literature 1 describes a T-shaped cutter for forming
an undercut in a side surface of a workpiece. The T-shaped cutter
has a head which is connected to one end of a shank, wherein a
plurality of bottom blades having cutting edges on a distal end
side of the head and a plurality of upper blades having cutting
edges on a base edge side are alternately arranged in the
peripheral direction, and the cutting edges of the bottom blades
and the upper blades are integrally formed with the shank and the
head.
PATENT LITERATURE
[0004] PTL 1 WO 2014068710
BRIEF SUMMARY OF THE DISCLOSURE
[0005] Since the bottom blades, upper blades, shank, and head of
the T-shaped cutter of Patent Literature 1 are integrally formed,
undercut machining can be performed with high rigidity and high
efficiency. However, when the rib height becomes greater, the shank
must be lengthened accordingly, and a large lateral force (bending
stress) acts on the shank, causing deformation of the shank,
whereby there is a problem in that machining speed and machining
accuracy are reduced. Furthermore, in the T-shaped cutter of Patent
Literature 1, there is a problem in that only an inner peripheral
surface having a radius of curvature greater than or equal to the
radius of the head of the T-shaped cutter can be machined when the
curved inner peripheral surface at the corner where the ribs of the
workpiece intersect is machined.
[0006] The present invention aims to solve such problems of the
prior art and aims to provide a milling tool and workpiece
machining method which are capable of machining an undercut part
such as a rib having a return flange with high efficiency and high
accuracy.
[0007] In order to achieve the above object, according to the
present invention, there is provided a milling tool composed of a
shank part, and a head which is provided on a distal end of the
shank part and which has a cutting edge, wherein the head has an
expanding diameter section, the diameter of which gradually
increases along a direction from a proximal end contiguous with the
shank part toward a distal end, and a decreasing diameter section,
the diameter of which gradually decreases along a direction from a
maximum diameter section toward the distal end, and cutting edges
are provided on the expanding diameter section and the decreasing
diameter section.
[0008] Furthermore, according to the present invention, there is
provided a workpiece machining method for undercutting interior
portions of a rib of a workpiece attached to a table of a machine
tool and a return flange formed contiguous with the rib, the method
comprising the steps of attaching the milling tool according to
claim 1 to a spindle of the machine tool and rotating the milling
tool, and machining an interior of the return flange with a cutting
edge of the expanding diameter section of the milling tool and
machining a side surface of the rib with a cutting edge of the
decreasing diameter section of the milling tool.
[0009] According to the present invention, since the head of the
milling tool has an expanding diameter section, the diameter of
which gradually increases along the direction from a proximal end
toward the distal end, and a decreasing diameter section, the
diameter of which gradually decreases along the direction from a
maximum diameter section toward the distal end, and cutting edges
are provided on the expanding diameter section and the decreasing
diameter section, the milling tool can diagonally approach the
undercut part of the workpiece and machining of the workpiece can
be performed without interference with the return flange, whereby
the protruding length of the shank can be shortened. The undercut
part can be machined efficiently and with high quality under high
machine conditions.
BRIEF DESCRIPTION OF THE FIGURES
[0010] FIG. 1 is a front view of a milling tool according to a
first embodiment of the present invention.
[0011] FIG. 2 is a side view of the milling tool viewed from a
direction differing by 90.degree. from FIG. 1.
[0012] FIG. 3 is a front view of the milling tool of FIG. 1 in
which the cutting edge is removed.
[0013] FIG. 4 is a side view of the milling tool of FIG. 2 in which
the cutting edge is removed.
[0014] FIG. 5 is a bottom view of the milling tool of FIG. 1 view
from the head side.
[0015] FIG. 6 is a plan view of the milling too of FIG. 1 viewed
from the shank side.
[0016] FIG. 7 is a front view of an upper insert used in the
milling tool of FIG. 1.
[0017] FIG. 8 is a perspective view of the upper insert of FIG.
7.
[0018] FIG. 9 is a perspective view of the upper insert of FIG. 7
as viewed from a different direction.
[0019] FIG. 10 is a front view of a lower insert used in the
milling tool of FIG. 1.
[0020] FIG. 11 is a perspective view of the lower insert of FIG.
10.
[0021] FIG. 12 is a perspective view of the lower insert of FIG. 10
as viewed from a different direction.
[0022] FIG. 13A is a schematic view detailing a method for
machining a rib having a return flange.
[0023] FIG. 13B is a schematic view detailing a method for
machining a rib having a return flange.
[0024] FIG. 14A is a schematic view detailing a method for
machining a rib having a return flange.
[0025] FIG. 14B is a schematic view detailing a method for
machining a rib having a return flange.
[0026] FIG. 15A is a schematic view detailing a method for
machining a rib having a return flange.
[0027] FIG. 15B is a schematic view detailing a method for
machining a rib having a return flange.
[0028] FIG. 16 is a schematic view detailing the machining of an
undercut part when a T-shaped cutter is used.
[0029] FIG. 17 is a schematic view detailing the machining of an
undercut part when the milling tool of the present invention is
used.
[0030] FIG. 18 is a schematic view detailing the machining of an
undercut part at a corner part, and in FIG. 18, the milling tool
reaches the inlet of the corner part.
[0031] FIG. 19 is a perspective view as viewed in the direction of
arrow XIX of FIG. 18.
[0032] FIG. 20 is a side view as viewed in the direction of arrow
XX of FIG. 18.
[0033] FIG. 21 is a side view as viewed in the direction of arrow
XXI of FIG. 18.
[0034] FIG. 22 is a schematic view detailing the machining of an
undercut part at a corner part, and in FIG. 22, the milling tool
machines approximately the central part of the corner part.
[0035] FIG. 23 is a perspective view as viewed in the direction of
arrow XXIII of FIG. 22.
[0036] FIG. 24 is a side view as viewed in the direction of arrow
XXIV of FIG. 22.
[0037] FIG. 25 is a side view as viewed in the direction of arrow
XXV of FIG. 22.
[0038] FIG. 26 is a schematic view detailing the machining of an
undercut part at a corner part, and in FIG. 26, the milling tool
reaches the outlet of the corner part.
[0039] FIG. 27 is a perspective view as viewed in the direction of
arrow XXVII of FIG. 26.
[0040] FIG. 28 is a side view as viewed in the direction of arrow
XXVIII of FIG. 26.
[0041] FIG. 29 is a side view as viewed in the direction of arrow
XXIX of FIG. 26.
[0042] FIG. 30 is a front view of a milling tool according to a
second embodiment of the present invention.
[0043] FIG. 31 is a perspective view of the milling tool of FIG.
30.
[0044] FIG. 32 is a bottom view of the milling tool of FIG. 30 as
viewed from the head side.
[0045] FIG. 33 is a plan view of the milling tool of FIG. 30 as
viewed from the shank side.
[0046] FIG. 34 is a front view of the milling tool of FIG. 30 in
which the cutting edge is removed.
[0047] FIG. 35 is a perspective view of the milling tool of FIG. 30
in which the cutting edge is removed.
[0048] FIG. 36 is a bottom view of the milling tool of FIG. 30 as
viewed from the head side, in which the cutting edge is
removed.
[0049] FIG. 37 is a plan view of the milling tool of FIG. 30 as
viewed form the shank side, in which the cutting edge is
removed.
[0050] FIG. 38 is a front view of an insert used in the milling
tool of FIG. 30.
[0051] FIG. 39 is a perspective view of the insert of FIG. 30.
[0052] FIG. 40 is a perspective view of the insert of FIG. 30 as
viewed from a different direction.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0053] Preferred embodiments of the present invention will be
described below with reference to the attached drawings.
[0054] First, referring to FIGS. 1 to 12, a first embodiment of the
milling tool of the present invention will be described.
[0055] A milling tool 10 comprises a cylindrical shank 12 and a
head 14 which is integrally formed with the tip of the shank 12.
The head 14 has an approximately frustoconical expanding diameter
section 14a, the diameter of which increases along the direction
from the proximal end which contacts the shank 12 toward the distal
end, and an approximately frustoconical decreasing diameter section
14b, the diameter of which decreases along the direction from the
expanding diameter section 14a toward the distal end, and the head
is formed into substantially a double conical shape. A transition
part 14c as a maximum diameter part, at which the diameter is
maximum, is formed between the expanding diameter section 14a and
the decreasing diameter section 14b. The head 14 has upper grooves
16 formed in the expanding diameter section 14a and lower grooves
18 formed in the decreasing diameter section 14b. The upper grooves
16 and lower grooves 18 are alternatingly arranged at equal angular
intervals about the central axis O of the head 14. In the
illustrated embodiment, the head 14 has three upper grooves 16 and
three lower grooves 18. Note that though the upper grooves 16 and
the lower grooves 18 are arranged at equal angular intervals in the
present embodiment, they may be irregular angular intervals in
order to prevent chatter.
[0056] An upper seat 16a is formed in each upper groove 16, and a
lower seat (FIGS. 3 and 4) is formed in each lower groove 18. An
upper insert 20 is attached to each upper seat 16a, and a lower
insert 22 is attached to each lower seat 18a. Though three upper
inserts 20 are arranged in the expanding diameter section 14a and
three lower inserts 22 are arranged in the decreasing diameter
section 14b in the illustrated embodiment, the number of upper
inserts 20 and lower inserts 22 is not limited to three in the
present invention, and at least one upper insert 20 and at least
one lower insert 22 may be arranged. Thus, the expanding diameter
section 14a and the decreasing diameter section 14b may comprise at
least one upper groove 16 and at least one lower groove 18,
respectively.
[0057] The upper seat 16a is formed such that a linear main cutting
edge 20c (FIGS. 7 to 9) of the upper insert 20 attached to the
upper seat 16a obliquely extends in a direction in which the main
cutting edge gradually approaches the transition part 14c in the
direction of the rotation of the milling tool 10. The lower seat
18a is formed such that a linear main cutting edge 22c (FIGS. 10 to
12) of the lower insert 22 attached to the lower seat 18a obliquely
extends in a direction in which the main cutting edge gradually
approaches the transition part 14c in the direction of rotation of
the milling tool 10.
[0058] Further, a coolant passage for providing coolant to the
machining area can be formed in the milling tool 10. The coolant
passage can include an inlet passage 24 which passes through the
shank 12 along the central axis O of the milling tool 10, an upper
radial passage 26a which passes through the head 14 from the inlet
passage 24 in the radial direction and which opens into a side wall
16b which faces the upper seat 16a of each upper groove 16, and a
lower radial passage 26b which opens into a side wall 18b which
faces the lower seat 18a of each lower groove 18.
[0059] Referring to FIGS. 7 to 9, the upper insert 20 has an upper
edge 20a and a lower edge 20b. The upper insert 20 is attached to
the upper seat 16a so that the lower edge 20b is arranged near the
transition part 14c. The upper insert 20, when attached to the
upper seat 16a, has a rake face 20e which is arranged on the side
opposite the upper seat 16a and which faces the side wall 16b of
the upper groove 16 and a flank face 20g which is oriented toward
the radially outer side. A main cutting edge 20c which extends
substantially linearly from the upper edge 20a and an arc-shaped
sub cutting edge 20d which is provided adjacent the lower edge 20b
and which is connected to the main cutting edge 20c are formed by
the rake face 20e and the flank face 20g.
[0060] Referring to FIGS. 10 to 12, the lower insert 22 has an
upper edge 22a and a lower edge 22b. The lower insert 22 is
attached to the lower seat 18a so that the upper edge 22a is
arranged near the transition part 14c. The lower insert 22, when
attached to the lower seat 18a, has a rake face 22e which is
arranged on the side opposite the lower seat 18a and which faces
the side wall 18b of the lower groove 18, and a flank face 20f
which is oriented toward the radially outer side. A main cutting
edge 22c which extends substantially linearly from the lower edge
22b and an arc-shaped sub cutting edge 22d which is provided
adjacent the upper edge 22a and which is connected to the main
cutting edge 22c are formed by the rake face 22e and the flank face
22f. A bottom cutting edge 22g which is connected to the main
cutting edge 22c and an inner cutting edge 22h which is connected
to the bottom cutting edge 22g are formed on the lower edge 22b of
the lower insert 22.
[0061] The upper insert 20 and the lower insert 22 are attached to
the upper seat 16a and the lower seat 18a, respectively, so that
the respective sub cutting edges 20d, 22d are arranged in a forward
twisted manner with respect to the main cutting edges 20c, 22c in
the direction of rotation of the milling tool 10. Specifically, the
upper insert 20 and the lower insert 22 are attached while being
alternatingly inclined. Further, the upper inserts 20 are attached
to the upper seats 16a so that all of the main cutting edges 20c of
the upper inserts 20 rotate along a single conical surface when the
milling tool 10 rotates about the central axis O. Likewise, the
lower inserts 22 are attached to the lower seats 18a so that all of
the main cutting edges 22c of the lower inserts 22 rotate along a
single conical surface when the milling tool 10 rotates about the
central axis O. Note that the sub cutting edges 20d, 22d are
arranged in a rearward twisted manner with respect to the main
cutting edges 20c, 22c in the direction of rotation of the milling
tool 10, or may be arranged in a non-twisted state.
[0062] Though the two conical surfaces drawn by the main cutting
edges 20c, 22c of the upper insert 20 and the lower insert 20 when
the milling tool 10 rotates are symmetrical with respect to the
plane defined by the line of intersection between the two conical
surfaces in the illustrated embodiment, they may be asymmetrical
depending on the target machining process or workpiece shape.
Furthermore, the lines of intersection (the generatrix of each
conical surface) between the plane including the central axis O and
the two conical surfaces described above intersect at a
predetermined angle. This angle can be set to various values in
accordance with the target machining process. The angle that the
two lines of intersection form can be equal to, for example, the
angle between the rib, which is described later, and the return
flange protruding from the upper end of the rib, and can be
preferably 90.degree.. Furthermore, the main cutting edge 20c of
the upper insert 20 is formed so as to be longer than the
protruding dimension (width) of the return flange.
[0063] Further, the upper insert 20 and the lower insert 22 are
attached to the upper seat 16a and the lower seat 18a,
respectively, so that the sub cutting edges 20d, 22d move, when the
milling tool 10 rotates about the central axis O, along the shape
of the rotating body, which is the locus when one circular arc that
bulges in the radial direction of the head 14 rotates about the
central axis O of the milling tool 10. The shape of the rotating
body may be a shape which is inscribed in both of the two conical
surfaces drawn by the main cutting edges 20c, 22c of the upper
insert 20 and the lower insert 22 when the milling tool 10
rotates.
[0064] Furthermore, the shank 12 and head 14 may be integrally
formed using tool steel, and the upper insert 20 and the lower
insert 22 can be attached to the upper seat 16a and the lower seat
18a of the head 14 using an appropriate bonding technology such as
brazing. Further, after the upper insert 20 and lower insert 22
have been attached to the upper seat 16a and the lower seat 18a,
the upper insert 20 and the lower insert 22 may be ground so that
the generatrix of each of the two conical surfaces drawn by the
main cutting edges 20c, 22c achieves an angle matching the angle
between the rib of the workpiece and the return flange protruding
from the upper end of the rib and the shape of the rotating body
drawn by the sub cutting edges 20d, 22d is inscribed on both of the
two conical surfaces.
[0065] A rib machining method using the milling tool 10 will be
described below with reference to FIGS. 13A to 15B. In FIGS. 13A to
15B, a product 100, which is a workpiece, has a bottom wall 102, a
rib 104 formed in a thin wall extending perpendicularly from the
bottom wall 102, and first and second return flanges 106, 108 which
protrude in opposite directions from the upper end of the rib 104
substantially in parallel to the bottom wall 102. In the examples
of FIGS. 13A to 15B, on a machine tool (not illustrated) such as a
four-axis machining center having at least three orthogonal linear
feed axes and at least one rotary feed shat, and preferably a
five-axis machining center having three orthogonal linear feed axes
and two rotary feed axes, an end mill 70, the milling tool 10
according to the present embodiment, and a T-shaped cutter 72 are
sequentially attached to the tip of a spindle 80 of the machine
tool, and the product 100 is cut out from a thick plate made of a
metal material such as an aluminum alloy. Note that each of the end
mill 70, the milling tool 10, and the T-shaped cutter 72 are
attached to the spindle 80 via a tool holder 74. Furthermore, the
workpiece is affixed to a table (not illustrated) of the machine
tool.
[0066] Machining is performed from one of the first and second
return flanges 106, 108, and in the present example, from the first
return flange 106 side. First, in accordance with the width
dimension of the first return flange 106, material is removed from
the thick plate (FIG. 13B) in areas other than the bottom wall 102,
the first and second return flanges 106, 108, and portions 110, 112
between the first and second return flanges 106, 108 and the bottom
wall 102 using a rotary tool which is capable of cutting with the
side surface of the tool, such as the end mill 70 (FIG. 13A).
[0067] Next, the end mill 70 is exchanged with the milling tool 10
(FIG. 14A), and material is removed (undercut) from portion 110
between the first return flange 106 and the bottom wall 102. At
this time, as shown in FIG. 14A, the rotary feed axis of the
machine tool is set so that the side surface of the rib 104 can be
machined by the lower inserts 22. In FIG. 14A, the milling tool 10
is fed in the direction perpendicular to the sheet of the drawing
with respect to the workpiece, is fed by only a predetermined
distance (pick feed pitch) in the direction from the return flange
106 to the bottom wall 102, as illustrated by arrow Z, and is fed
again in the direction perpendicular to the sheet of the drawing,
and material of the portion 110 is sequentially removed from the
first return flange 106 side to the bottom wall 102 side in strips
having a width corresponding to the pick feed pitch. Until the
lower insert 22 comes into contact with the surface of the bottom
wall 102, when material is removed from portion 110 by feeding the
milling tool 10 in the direction perpendicular to the surface of
the drawing while repeating the pick feed in the direction
indicated by arrow Z, finally, as shown in FIG. 14B, a triangular
columnar portion 110a extending in the direction perpendicular to
the surface of the drawing remains between the rib 104 and the
bottom wall 102. Portion 110a can be removed (FIG. 15B) using the
T-shaped cutter 72 (FIG. 15A). While undercutting is performed by
the milling tool 10, not only the main cutting edges 20c, 22c and
the sub cutting edges 20d, 22d but also the bottom cutting edge 22g
and the inner cutting edge 22h contribute to the machine process,
whereby machining can be performed without the occurrence of
gouging.
[0068] Portion 112 between the second return flange 108 and the
bottom wall 102 can be removed by the same method as the method
described above. In this manner, the product 100 having the bottom
wall 102, the rib 104 extending perpendicularly from the bottom
wall 102, and the first and second return flanges 106, 108 which
protrude parallel to each other in opposite directions from the
upper end of the rib 104 toward the bottom wall 102 can be cut out
from a metal thick plate material such as an aluminum alloy. The
product 100 can be, for example, an aircraft wing part.
[0069] Portion 110a can be removed using the T-shaped cutter 72, as
shown in FIG. 16. In this case, the T-shaped cutter 72 is oriented
so that the axis of rotation thereof is parallel to the rib 104.
Thus, the protruding length of the T-shaped cutter 72, i.e., the
distance L.sub.TC from the bottom surface of the tool holder 74 to
the tip of the T-shaped cutter 72, must be greater than the height
of the rib 104. In contrast thereto, the milling tool 10 according
to the present embodiment is obliquely oriented so that the conical
surface drawn by the lower inserts 22 comes into contact with the
rib 104. Thus, the protruding length L.sub.TP of the milling tool
10 can be set to a length such that the return flange 106 or 108 do
not interfere with the tool holder 74. Since the overhang lengths
of the return flanges 106, 108 are normally much shorter than the
height of the rib 104, the protrusion length L.sub.TP of the
milling tool 10 can be shorter than the protrusion length L.sub.TC
of the T-shaped cutter 72. By shortening the protrusion length, the
tool normally has higher static rigidity against bending and
inclination and higher dynamic rigidity against vibration, whereby
the rotation speed of the tool and the feed rate of the tool can be
increased. Thus, by using the milling tool 10 according to the
present embodiment, the product 100 can be more efficiently
machined as compared to the case in which the T-shaped cutter 72 of
the prior art is used. Furthermore, chatter is less likely to
occur, whereby the quality of the machined surface is improved.
[0070] Further, the milling tool 10 can be used to machine not only
a linear rib, as shown in FIGS. 13A to 15B, but also a rib which is
bent by a predetermined angle, 90.degree. in the illustrated
example, as shown in FIGS. 18 to 29. In FIGS. 18 to 29, a workpiece
200 has a flat plate-like bottom wall 202, first and second ribs
204, 206 which protrude perpendicularly from the bottom wall 202, a
return flange 208 which protrudes perpendicularly from the upper
end of the first rib 204, and a corner part 210 at which the first
and second ribs 204, 206 intersect. The first and second ribs 204,
206 connected to each other by the corner part 210 extend along the
bottom wall 202 at an angle of 90.degree.. Note that the workpiece
200 is affixed to a table (not illustrated) of a machine tool.
[0071] First, the milling tool 10 machines the upper edge of the
first rib 204 and the lower surface of the return flange 208, as
detailed in FIGS. 14A, 14B. In more detail, the milling tool 10 is
linearly fed along the side surface of the upper edge of the first
rib 204 from one end of the first rib 204 (the lower edge in FIG.
18) toward the corner part 201 (upwardly in FIG. 18) so that the
lower surface of the return flange 208 and the side surface of the
first rib 204 are simultaneously machined by the main cutting edge
20c of the upper insert 20 and the main cutting edge 22c of the
lower insert 22, respectively. During machining (undercutting) of
the side surface of the upper edge of the first rib 204 and the
lower surface of the return flange 208, the corner R part 208a
between the first rib 204 and the return flange 208 is
simultaneously machined by the sub cutting edges 20d, 22d of the
upper insert 20 and the lower insert 22.
[0072] As shown in FIGS. 18 to 21, when the milling tool 10 arrives
at the inlet of the corner part 210, the milling tool 10 is
continuously fed along a substantially arcuate tool path along the
inner peripheral surface 210a of the upper edge of the corner part
210 without interruption (FIGS. 22 to 25). As described above, in
the milling tool 10, since the lower insert 22 has the bottom
cutting edge 22g and the inner cutting edge 22h, cutting can be
performed while freely changing the cutting direction (the
direction of the axis of rotation O of the milling tool 10) by
simultaneous five-axis control, whereby machining marks such as
steps on the machined surface are not formed, and a corner part 210
having a return flange as illustrated can be machined.
[0073] As shown in FIGS. 26 to 29, when the milling tool 10 arrives
at the outlet of the corner part 210, the milling tool 10 is
continuously linearly fed toward the front end of the second rib
206 (rightward in FIGS. 22 and 24) along the side surface of the
second rib 206 without interruption. During this movement, the side
surface of the upper edge of the second rib 206 is machined by the
main cutting edge 22c of the lower insert 22. When the milling tool
10 arrives at the front end of the second rib 206 (the right part
in FIGS. 22 and 24) and machining of the upper edge of the second
rib 206 is complete, a pick feed is imparted to the milling tool 10
in the direction (downward) approaching the bottom wall 202. Next,
the milling tool 10 is linearly fed along the side surface of the
second rob 206 toward the corner part 210, and the lower side of
the machined surface completed in the previous machine process is
machined on the side surface of the second rib 206.
[0074] Note that though straight lines are shown between the first
rib 204 and the corner part 204 and between the corner part 210 and
the second rib 206 in FIGS. 18 to 29, these straight lines are
merely shown in the drawings for the purpose of making the first
rib 204, the corner part 210, and the second rib 206 easy to
understand. Machining marks such as linear steps and grooves are
not actually formed on the machined surface.
[0075] When the side surface of the upper edge of the first rib 204
is machined along with the lower surface of the return flange 208,
the corner part 210 and the side surface of the upper edge of the
second rib 206 are machined, and the first rib 204, the corner part
210, and the side surface of the second rib 206 are machined in
this manner, finally, an uncut portion (not illustrated) similar to
the portion 110a having a triangular cross section shown in FIG.
14B is formed between the first rib 204, the corner part 210 and
the second rib 206, and the bottom wall 202. This uncut portion can
be removed by the T-shaped cutter, as shown in FIG. 15A. At this
time, the corner R parts 204a, 210b, 206a between the first rib
204, the corner part 210 and the second rib 206, and the bottom
wall 202 can be formed in accordance with the shape of the T-shaped
cutter.
[0076] Note that in the embodiment shown in FIGS. 18 to 29, the
return flange 208 extends substantially parallel to the bottom wall
202 along the upper end of the first rib 204 and has a constant
width. The width of the return flange 208 at the corner part 210
gradually reduces towards the second rib 206, and the return flange
is substantially not provided on the second rib 206. However, the
workpiece 200 may have a return flange similar to the return flange
208 along the upper end of the second rib 206.
[0077] Next, a second embodiment of the milling tool of the present
invention will be described with reference to FIGS. 30 to 40.
[0078] Though the inserts were divided into upper inserts 20 and
lower inserts 22 in the first embodiment, in the second embodiment,
both inserts 20, 22 are integral so as to form a single V-shaped
insert, and this insert is attached from the expanding diameter
section of the head to the decreasing diameter section.
[0079] A milling tool 50 comprises a cylindrical shank 52 and a
head 54 which is integrally formed with the tip of the shank 52.
The head 54 has an approximately frustoconical expanding diameter
section 54a, the diameter of which increases from the proximal end
which contacts the shank 52 in the direction toward the proximal
end, and an approximately frustoconical decreasing diameter section
54b, the diameter of which decreases along the direction from the
expanding diameter section 54a toward the distal end, and the head
54 has substantially a double conical shape. A transition part 54c
as a maximum diameter part, at which the diameter is maximum, is
formed between the expanding diameter section 54a and the
decreasing diameter section 54b. In the present embodiment, the
transition part 54c presents a shape of a rotating body obtained by
rotating an arc which bulges in the radial direction of the head 54
about the central axis O of the milling tool 50.
[0080] The head 54 has upper grooves 56 formed in the expanding
dimeter section 54a and lower grooves 58 formed in the decreasing
diameter section 54b. Four pairs of upper grooves 56 and lower
grooves 58 arranged at equal angular intervals around the central
axis O of the head 54 are formed in the head 54. Each pair of upper
grooves 56 and lower grooves 58 are continuous and form one groove
portion formed over the expanding diameter section 54a, the
transition part 54c, and the decreasing diameter section 54b.
Though the number of the grooves is not an indispensable
requirement of the present invention, at least one groove can be
provided.
[0081] A seat 62 for attachment of the insert 60 is formed in each
groove 56, 58. The seat 62 is defined by a flat surface for
receiving the insert 60 formed in a V-shape. In the present
embodiment, the flat surface forming the seta 62 is parallel to the
central axis O of the milling tool 50.
[0082] Further, a coolant passage for providing coolant to the
machining area can be formed in the milling tool 50. The cooling
passage can include an inlet passage 64 which passes through the
shank 52 along the central axis O of the milling tool 50, upper
radial passages 66a which pass through the head 54 from the inlet
passage 64 in the radial directions and which open into a side wall
56a which faces the seat 62 of each upper groove 56, and lower
radial passages 66b which open into a side wall 58a which faces the
seat 62 of each lower groove 58.
[0083] Referring to FIGS. 38 to 40, the insert 60 has first and
second arms 60a, 60b and a bent part 61 for connecting the first
and second arms 60a, 60b, and the insert 60 is substantially
V-shaped. The insert 60, when attached to the seat 62, has a rake
face 60f is arranged on the side opposite the seat 62 and which
faces the side wall 56a of the upper groove 56 which and a flank
face 60g which is oriented toward the radially outer side. A first
main cutting edge 60c which extends substantially linearly on the
arm 60a, a second main cutting edge 60d which extends substantially
linearly on the second arm 60b, and an arc-shaped sub cutting edge
60e which is provided on bent part 61 and which is connected to the
first and second main cutting edges 60c, 60d are formed by the rake
face 60f and the flank face 60g.
[0084] The insert 60 is attached to the seat 62 so that the first
main cutting edges 60c rotate along the same conical surface and
the second main cutting edges 60d rotate along the same conical
surface when the milling tool 50 rotates about the central axis O.
When the milling tool 50 rotates, the two lines of intersection
(the generatrix of each conical surface) between the conical
surfaces drawn by the first and second main cutting edges 60c, 60d
and the plane including the central axis O intersect at a
predetermined angle. This angle can be set to various values
depending on the target machining process. The angle formed by the
two lines of intersection described above can be equal to, for
example, the angle between the rib, which is described later, and
the return flange protruding from the upper end of the rib, and can
be preferably 90.degree..
[0085] Furthermore, when the insert 60 is attached to the seat 62,
as shown in FIGS. 32 and 33, the first and second main cutting
edges 60c, 60d, the sub cutting edge 60e, the bottom cutting edge
60h, and the inner cutting edge 60j are preferably arranged in a
single plane including the central axis O of the milling tool 50.
Further, the first and second main cutting edges 60c, 60d, the sub
cutting edge 60e, the bottom cutting edge 60h, and the inner
cutting edge 60j are arranged in the same plane in which the first
and second main cutting edges 60c, 60d, the sub cutting edge 60e,
the bottom cutting edge 60h, and the inner cutting edge 60j of the
insert 60 on the diametrically opposite side.
[0086] Further, the insert 60 is attached to the seat 62 so that,
when the milling tool 50 rotates about the central axis O, the sub
cutting edge 60e draws a locus of one rotary body shape obtained by
rotating the circular arc that bulges in the radial direction of
the head 14 about the central axis O of the milling tool 50. The
shape of the rotating body may be a shape which is inscribed in
both of the two conical surfaces drawn by the first and second main
cutting edges 60c, 60d of the insert 60 when the milling tool 50
rotates.
[0087] Furthermore, the insert 60 can be attached to the seat 62
using an appropriate bonding technology such as brazing. Further,
after the insert 60 has been attached to the seat 62, the insert 60
may be ground so that the generatrix of each of the two conical
surfaces drawn by the first and second main cutting edges 60c, 60d
achieves an angle matching the angle between the rib and the return
flange protruding from the upper end of the rib and the shape of
the rotating body drawn by the sub cutting edge 60e is inscribed on
both of the two conical surfaces.
REFERENCE SIGNS LIST
[0088] 10 Milling Tool [0089] 12 Shank [0090] 14 Head [0091] 14a
Expanding Diameter Section [0092] 14b Decreasing Diameter Section
[0093] 20 Upper Insert [0094] 22 Lower Insert [0095] 104 Rib [0096]
106 First Return Flange [0097] 108 Second Return Flange [0098] 204
First Rib [0099] 206 Second Rib [0100] 208 Return Flange [0101] 210
Corner Part
* * * * *