Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a milling head; more particularly,
this invention relates to a milling head for pro~ile and CNC
milling machines having a plurality of cutting bits on its
frontal side.
Milling heads of this type are also Xnown as "end-milling
cutters" or "shank-type slotting" end mills. While milling
heads, if their cutting bits protrude suf~iciently at their
frontal side, may be used to a limited extent also with milling
advance in the axial direction, drilling, i.e~ unrestrict2d
milling in the axial direction, is not possible, as the material
of the milling head located between the cutting bits limits any
such drilling advance.
It is the feature of one aspect of this invention to create
a milling head capable of carrying out both milling and also
unlimited drilling work, particularly when the drilling head is
used as a profile cutter. :
In accordance with this invention, a milling head of this
general type is characterized in that at least two cutting bits
are provided in a manner such that their frontal sides are
located essentially~in an:extent of ths milling axis (limited by
2~ th~ revolving cutting edge) and are located in a diameter plane,
with the cutting edges on the one hand being at least in contact
with or overlapping each other, and on the other hand, projecting
past the cylindrical surface:of the miliing head.
By locating the cutting bits in a plane in the rotating axis
o~ the milling head, during the course of drilling, the working
pressure caused by the cutting of the chips acts uniformly and
symmetrically on the drilling head. Due to th~ contact or
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overlap of the cutting bits in the area of the rotating axis of
the milling head, there is also obtained ~during drilling) a
self-centering action which takes place. Upon starting the
milling head in a drilling ad~ance action, initially a center
cone remains in the hole drilled, having at the most a height of
one-half of the diameter o~ the cutting bits if they are in
contact with each other with their cutting edges in khe rotating
axis of the milling head. As the milling head is subsequently
reoriented from drilling advance position to a laterally directed
milling advance pQsition, the remaining center cone is rapidly
decomposed. This moda of operation is particularly advantageous
in profile milling and in the preparation of molding tools for
plastic injection molding, since such tools are machined out of
solid blocks.
Therefore, with the milling head according to the present
invention a deep hollow may initially ~e produced in the block
by a drilling advance action and immediat~ly thereafter, milling
may be ef~ected with a lateral advance action, without a change
of tools. It is no longer nacessary to initially work with a
drill milling machine and then change the tool or remov~ material
essentially by lateral milling, layer by layer, until the desired
depth is obtained.
25According to a further aspect of this in~ntion, the cutting
bits are centered relative to the milling head. This permits the
contact or overlap wîth ea~h other with the point of contact
being located in the axis of rotation of the milling head or the
overlap which is aligned symmetrically relative to said axis.
30Advantageously, the overlap is such that it begins directly
within the contact or overlapping location of the cutting bits
and covers at least about a one eighth sector of the cutting
bits. This overlapping area (and also the overlap location of
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the cutting bits if they are arranged in this manner) is located
diagonally and opposite the area of the cutting bits upon which,
in the case of a lateral milling advance, i.e. with an
asymmetrical loading of the milling machine, the working pres~ure
is acting. Thus the cutting bits are not only held by their
holding screws, but are also secured particularly well against
tilting relative to this center fastening. Accordingly, the
tilting of the cutting bits is safely prevented even in the case
of a strong asymmetrical action of the working pressure during
cutting with lateral advance~.
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The rear sides of the cutting bits rest with their entire
surface on the material of the milling head, which is shaped in
a appropriate manner. This full surface abutting arrangement
thus ensures that both in drilling and in milling the working
pressure produced by the cutting is transferred and removed ~rom
the cuttin~ bits to the milling head reliably and uniformly.
The cutting bits may have a round or a rectangular
configuration. If, on the cutting bits, straight cutting edges
oriented against each other are present~ the mounting is
advantageously carried out so that they are inclined and located
closer to the cutting area. In this manner, a moxe favourable
cutting performance is obtained, particularly as the cutting bits
25; are supported against each other within a range, so that any
stress may be transmitted over a ~hort path into the cutter or
with the alternating forces directed against each other, to
thereby cancel each other.
The recesses forming the seat of the cutting bits in the
milling head are conveniently continued as chip removing grooves
in the direction of th~ chuckin~ sha~t. These ~rooves are
preferably helical in form. This ensures that the chips are
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safely removed, particularly by means of h~lical grooves duriny
drilling, since these act as the grooves in a drill.
According to the present invention a milling head is
provided which, in the ~orm of a smaller tool, as end-milling
cutters or shank type slotting end mills, is significantly more
stable in drilling and produces a symmetrical acceptance and
removal of the forces applied, without breakage due to unilateral
stressing. In this manner, the present invention results in
lo point cutting tools with optimal stability, which may be used not
only as milling tools, but also for full drilling.
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The invention will become more apparent from;the following
description with reference to the drawings, wherein:
Figure 1 shows a lateral elevation of a milling head of an
end-milling cutter;
; ~ ~ Figure:2 shows a cross-sec~ion of Figure 1;:
; ~Figure:3 shows a front view of the~head part of-the milling
head, partially cut away;
: ~ ~ Figure 4 shows:a cross section of another embodiment of the
milling.head; ~
Figur~ 5 shows a~front view of Figure 4, partially cut away;
Figure 6 shows a cross-section of yet another embodiment;
and
Figure 7 shows a front view of Figure 6j partially cut away.
A milling head or end-milling cutter according to the
invention is shown in Figure 1, generally in elevation~ It
illustrates of the chucking area 1, th~ shaft 2 and the head area
3 proper, at which the sarbide cutting bits 4 are clamped in a
manner such that they~may project in the direction of the axis
of rotation 5, i.e. in the radial axial direction, with their
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c~tting edges capable of pro~ecting laterally. Conveniently,
within the milling head or end-mill cutter, a feeder channel 6
is provided axially ~or cooling water, openings 7 for the latter
being located appropriately above the cutting bits 4. From the
cutting bits, in the direction o~ the shaft, recessed grooves 8
extend which permit the removal of chips, with the grooves
optionally being in a helical fo~m, comparable to a drill bit~ :
According to the embodiment illustrated in Figures 2 and 3,
on the front side o~ the milling head or end-mill cutter two
round cutting bits 4 are clamped in place by means of central
fastening screws 9. The chuck is configured so that the circular
surfaces 11, which are enclosed by the cutting edges, (i.e. in
milling the frontal sides of the cutting bits) are located in a
diameter plane. This is sh~wn in Figure 2 which is a cross-
sectional view o~ the milling cutter. The two frontal surfaces
ll are thus located in a plane substantially corresponding to the
diameter of the circularly milling shaft or head.
20Furthermore, the clamping o~ the cutting bits 4 is such that
they are in mutual contact wi~h their respective cutting edges
since they are located in the diameter plane of the milling head,
exactly in the center, i.e~ in the axis of rotation 5 of the
milling head end-milling cutter. On the outside the cutting ~-
25edges lO of the two cutting bits project past the outer contour
of the milling cutter.
It may be seen that thi~ partisular layout of the cutting
bits and the milling head or end-mill cutter is suitable both for
30drilling and milling procedures. In the drilling advance action
in the direction of the axis of rotation 5, the material of the
workpiece is cut by the cutting edg s 10 of the cutting bits in
front of the milling cutter, whereby initially between the two
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cutting bits 4, (in the center of khe bore hole), a concave cone
remains and extends to the center point of contact of the two
cutting bits. Thi~ cone is cut during the drilling advance on
its outer surface, with th~ chip removal or cutting work steadily
decreasing as the center and the axis of rotation 5 are
approached respectively, so that practically no cutting takes
place in the axis of rotation and ~ery little in the-vicinity of
said axis, wherein the latter specifically also absorbs the
advance component and is therefore inclined. :~
The conditions are thu~ di~ferent from those in general
drilling work with a conventional drill, where the material in
th~ axis o~ rotation and its immediate vicinity cannot be cut,
but must be pressured aside laterally. Conditions in drilling
with the milling head,~according to the invention, are therefore
significantly more favorable and it i~ possible to work with
considerably higher drilling advances. In addition, due to the
configuration of the r~und cutting bits, an outstanding breaking
and comminution of the chips is obtained; this is in-contrast to :~
convenkional drilling where long helical chips are produced,
which cause considerable problems and even malfunctions in the
course of their removal. By means of the layout of the two
cutting bits 4 and their point of contact in the axis of rotation
5, self-centering is providedj in the diameter plane where the
cutting edges 10 are located; all forces that appear are applied
entirely symmtrically relative to the axis of rotation 5, and
oppose each other to mutually cancel.
In order to improve the uptake force and clamping of the
cutting bits 4, the latter are positively embeddedl according to
the invention, as far as possible in the material of the milling
head or end-mill cutter, io e. the cutting bits in locations in
which their cutting edges are not used, are inserted in positive
locking grooves, with the material of the milling head contacting
the rear sides 12 of the cutting bits.
This feature enables the bits to bP well supported
particularly in lateral milling, and the forces applied in
particular to the sides and the lateral proiections o~ the
cutting edges 10 (Fig. 2~ to be uniformly and well transmitted.
The milling head i5 further designed so that directly within
the center contact location 13 of the tw~ cutting bits, the
material of the milling cutter ~verlaps the ~rontal surface 11
of the cutting bits 4. This overlap 14 grips the cutting bit
with particular e~fect in the~area where the tilting moment
becomes appreciable due to the working pressure applied to the
opposite side; this moment attempts to tilt the cutting bit 4
around a tilting axi passing:through the holding screw 9 against
the support on its rear side 12.~ This overlap 14 is limited only
by the chip removal groove 8,~but it may b~ substantially broader
than that illustrated in Fig. 3, if for example, by a
corresponding layout of the cooling wa~er conduit~, the complete
removal of the ~hips is assuredO This "embedding" of the cutting
bits, whereky any tilting o~ the bits relative to their clamping
is substantially prevented, makes it po~sible, in addition to the
aforementioned other measures, to achieve an increase in the
advance velocities ~nd thus improves the economics of the
processO: The life of~the Gutting bits is also extended, as any
"rattling" cf the cutt:ing bits due to inadequate clamping is
substantially prevented .
The embodiment illustrated in Figures 4 and ~, represents
a further development of the embodiment illustrated in Figures
2 and 3. In this example, the two cutting bits 4 are mounted so
that the frontal sur~aces 11 mutually overlap in the area of the
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axis of rotation; this overlap 15 is shown as an extreme case in
this example. During the coursP of drilling in the axial
direction, a relativ~ly low and very flat cone remains in the
center o~ the bore hole, so that with this configuration drilling
work may also be carried out.
The overlap 15 of the two cutting bits 4 in this form also
corresponds to an extended configuration o~ the overlap 14 of the
supporting cutter material, so that the cutting bits in the area
lo of the rotating axis 5 of the cutter are doubly supported, i.é~
once a~inst each other and secondly against the material of the
milling cutter. Due to this support against each other, the
working forces acting on the outside of the cutting bits are
acting directly against each other and effectively cancel each
other. In the case of a la~eral milling ad~ance, wherein the
"rear side" of the milling head is not in ~lamping contact and
thus the cuttiny bits are running ~reely, the for~es acting on
the frontal side in the advance direction are tran~mitted to the
material of the milling head directly at the overlap-location 14
or with the interaction o~ the overlapping opposite cutting bit.
It will be appreciated from the description of the foregoing
embodiments, that in place o~ the circular cutting bits shown
here, cutting bits with a flat oval configuration may also be
used, wherein the straight line cutting edges o~ the two cutting
bits oppose each other and on the outside are oriented away from
each other, i~e. the straight cutting edges are the edges
segments of the cutting bits which contact or overlap each other
in the area of the axis o~ rotation.
When using flat oval cutting bits, it is advantageous to
mount them in a manner such that they are obli~uely inclined
relative to the rotating axis with their opposing straight line
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segments~ with the frontal sides directly contacting or
overlapping each other, so that an image corresponding to Figures
3 or 5 is created, while the segment facing away from the ~rontal
side also moving away from each other, so that their opposing
areas gPnerate a cone. This layout provides an improved free
cutting of the milling head.
ln the example illustrated in Figures 6 and 7, the
conditions described herein previously for straight cutting edges
~0 are applied to some extent to the use of square or rectangular
cutting bits. These cutting bits lla ar~ inserted and supported,
as illustrated in Figures 6 and 7 in a manner such that their
diagonals, i.e. the lines connecting their corners and thus their
cutting edges 10, are inclined relative to the rotating axis 5.
The innermost corners form a mutual overlap, so that the two
cutting bits 4a, which have a square configuration, support each
other at their inner corners. :Additionally, in this area there
is another overlap 15 by the material of the milling head,
whereby the cutting bits 4a~with a ~traight line configuration
are positively embedded, so that the bits do not tilt under load,
and thus transmit the compressive forces acking on the area of
the overlap directly to each other, to thereby cancel and
transmit the other forces acting in the area of the overlap 15
to the milling head.
The inclination of the~ cutting edges 10 in the vicinity of
the axis of rotation 5 results in drilling to the formation o~
a relatively acute cone so that cutting is facilitated in the
boring advance, to permit higher advance velocities. Further,
this results in a flat angle setting o-f the outwardly pointing
cutting edges, so that in a lateral milling advance a slight chip
depth is taken off. The chip cutting work is therefore
relatively low in the case of thick milling layers and
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accordingly, the stress on the milling tool and thus its life is
appreciable more favorable.
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Although embadiment~ of the invention have been
5 described above, it i5 not limited thereto and it will be
apparent t~ those skilled in the art that numerous modifications
form part of the present invention insofar as they do not depart
from the spirit, nature and sc:ope of the claims and described
invention.
