CA2079037A1

CA2079037A1 - Milling head

Info

Publication number: CA2079037A1
Application number: CA002079037A
Authority: CA
Inventors: Franz-Josef Pokolm
Original assignee: Individual
Current assignee: POKOLM FANZ JOSEF
Priority date: 1991-09-30
Filing date: 1992-09-24
Publication date: 1993-03-31
Also published as: KR930005707A; ATE125479T1; ES2076639T3; DE59203025D1; JPH06170632A; EP0537476B1; KR100262970B1; DE9112169U1; EP0537476A1

Abstract

ABSTRACT OF THE DISCLOSURE

There is disclosed a milling head device which includes a plurality of cutting bits mounted therein. The cutting bits are positioned within the milling head such that the cutting surfaces thereof contact each other in one embodiment and overlap in a further embodiment of the invention. The disposition of the cutting bits according to the invention permits a longer lifetime for the bits while at the same time improving cutting efficiency at higher velocities than encountered in conventional drilling and milling apparatus.

Description

g ~a~
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 , - . , .

~ 7 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 ; ~ ; :: . . . .

. .,~ . , : . : .. :

~t'f`~JJ~

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~.
,' 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 :- : . - -:, :, ~ ' 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.
~:
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 .' .~

2~

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 :

2~

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 ~ ;f `~ t~

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 ,- , ,; . . " , - . : : , 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 2P.~

~o ~:
accordingly, the stress on the milling tool and thus its life is appreciable more favorable.
',:
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.

Claims

1. In a milling head device having a front side and in which there are a plurality of cutting bits each having cutting edges and said cutting bits are located at said front side, the improvement wherein said head includes at least two cutting bits having frontal sides, said frontal sides being located essentially in the extent of a milling axis of rotation and positioned in a diameter plane of said milling head, whereby said cutting edges of each of said cutting bits are in contact with each other, and project beyond an outer surface of said milling head.

2. A milling head according to claim 1, wherein said cutting bits contact each other centrally relative to said milling head, said contact being located in said axis of rotation of said milling head.

3. A milling head according to claim 1, wherein said cutting bits overlap centrally relative to said milling head, whereby said overlap is symmetrically located relative to said axis of rotation of said milling head.

4. A milling head according to claim 1, wherein said frontal surfaces are delimited by said cutting edges of said cutting bits in an area where said bits are embedded in material forming said milling head and are overlapped by said material.

5. A milling head according to claim 4, wherein said area overlapping the cutting bits by the material of the milling head begins directly within said contact or overlap location of the cutting bits and covers at least about one-eighth of the cutting bits.

6. A milling head according to claim 1, 2 or 3, wherein said bits have rear sides resting with their full surface on the material of the milling head, the latter having a cooperating shape relative to said rear sides.

7. A milling head according to claim 1, wherein said cutting bits are round.

8. A milling head according to claim y, wherein said cutting bits are circular.

9. A milling head according to claim 7, wherein said cutting bits have a flat oval outline.

10. A milling head according to claim 6, wherein said cutting bits are square.

11. A milling head according to claim 9 or 10, wherein said cutting bits are mounted in an inclined configuration relative to a rotating axis with the straight edges of said cutting bits opposing each other, whereby said cutting bits are located closer to each other toward a cutting area thereof.

12. A milling head according to claim 12, wherein said cutting head has recesses forming a seat for said cutting bits and wherein the recesses are continued as chip removing grooves in a direction of a chucking shaft.

13. A milling head according to claim 1, wherein said chip removing grooves are helical.

14. A milling head according to claim l, 2 or 3, wherein said milling head has an axial channel for the supply of cooling water therein, said channel having at least one outlet located immediately above said seat of said cutting bits.

15. A milling head according to claim 14, wherein said outlet is in a parallel extension axis of the location of the clamping screws.