EP2097200A1

EP2097200A1 - End milling cutter with different cutting edges

Info

Publication number: EP2097200A1
Application number: EP07847382A
Authority: EP
Inventors: Josef Giessler
Original assignee: Sandvik Intellectual Property AB
Current assignee: Sandvik Intellectual Property AB
Priority date: 2006-12-08
Filing date: 2007-11-27
Publication date: 2009-09-09
Also published as: DE102006058258A1; JP2010511522A; US20100098504A1; WO2008068158A1

Abstract

The present invention relates to an end milling cutter with a number of end-cutting edges (10, 20), at least a first one (10) of which reaches up to the axis (30) of the milling cutter. To provide an end milling cutter that allows much greater axial feed movements and nevertheless leaves behind relatively smooth surfaces at its end face under the normal feed movement of the milling cutter taking place laterally (perpendicularly to the axis), it is proposed according to the invention that the milling cutter has at least one further, second end-cutting edge (20) that is different from the first end-cutting edge (10), wherein the axial position and formation of the first cutting edge (10) and the second cutting edge (20) are provided in such a way that, when the rotating milling cutter axially enters a workpiece, a radially inner region (a) cuts only by the first cutting edge (10) from the axis (30) of the milling cutter to a first radius (ri) that is less than the nominal radius and greater than a radially inner radius of the second cutting edge, and that, in a second region (b), which lies between the radius ri and a greater radius ra, which can at most assume the value of the nominal radius (R) of the milling cutter, only the second cutting edge (20) cuts.

Description

End mill with different cutting edges

The present invention relates to an end mill with a plurality of end cutting edges, of which at least one first extends to the axis of the milling cutter, according to the preamble of claim 1.

Corresponding end mills, which are also referred to as face milling, have long been known. In this case, the end cutting serve to produce a more or less smooth surface in the normal feed movement of the end mill during operation, which is perpendicular to the axis, on the front side of the cutter facing side of the workpiece. End millers or face milling cutters in which at least one cutting edge extends into the center or to the axis of the milling cutter can, within certain limits, also be moved into a workpiece with an axial feed or a combined axial and lateral feed. However, the axial feed movement is usually reserved to drills having specially designed for this axial feed movement cutting, whereas the end cutting an end mill serve primarily to smooth the remaining under the frontal cutting surfaces during the normal horizontal feed movement of the milling cutter.

This requirement brings with it restrictions that do not allow the end face of an end mill or end mill similar to a drill to design, so as to allow axial feed movements better. Rather, the requirement to produce at least approximately smooth surfaces along the end faces of an end mill results in a configuration of the end-side cutting which is far from optimal in terms of axial feed movements.

Compared to this prior art, the present invention has the object to provide an end mill, which allows significantly higher axial feed movements and yet leaves in the normal lateral (perpendicular to the axis) advancing movement of the milling cutter on its face relatively smooth surfaces.

This object is achieved in that the cutter has at least one further, different from the first end cutting second cutting edge, wherein the axial position and shape of the first cutting edge and also the second cutting edge is provided such that in a axial dipping of the rotary cutter into a workpiece within a radially inner region from the axis of the cutter to a first radius η intersects only the first cutting edge, wherein the radius r, is smaller than the nominal radius of the end mill, and that in a second, radially adjoining area only the second cutting intersects, between the radially inner radius r, and a larger radius r _a, the maximum may take the value of the nominal radius R of the milling cutter.

This division of work areas for the first cutting edge and the second cutting edge makes it possible to design the first cutting edge primarily for an effective axial feed movement, while the second cutting edge should not obstruct an axial feed movement as far as possible, but at the same time a lateral feed motion as possible should produce smooth surface on the workpiece, this operation is again not hindered or impaired by the first cutting edge and even supported according to preferred embodiments.

According to a first embodiment of the invention, the outer radius r _a to which the second cutting edge alone cuts in the radial direction is smaller than the nominal radius R of the milling cutter, the range between the radius r _a and the nominal radius R during axial dipping of the milling cutter is machined into a workpiece substantially equally by both cutting edges.

It is understood that, as far as radially inner and subsequent radial regions or a radial outer region is mentioned, this refers to the reference system of the milling cutter, and, as far as the machining in these areas is mentioned, a solely axial Movement of the milling cutter is considered. Otherwise, in the case of an exclusively lateral feed movement, the radially outer regions of the cutting edges also chop the material in the same region over which the radially inner regions of the cutting edges are guided after the corresponding feed.

According to an embodiment of the present invention, the radially outer portions of the first and second cutting edges are at the same time the axially most projecting cutting portions and are nearly perpendicular to the axis or at an angle slightly different from the 90 ° angle to the axis. These cutting sections can also have a slight curvature whose radius corresponds at least approximately to the nominal radius of the milling cutter. The radially inner cutting portions may have a greater inclination relative to a plane perpendicular to the cutter axis and in particular also with be projecting tips which are in the axial direction either just as far as the radially outer edge portions or against these radially outer regions only slightly, ie, typically less than 1 mm, axially set back.

According to another embodiment of the present invention, at least one further first cutting edge is arranged symmetrically with respect to the cutter axis relative to the first cutting edge. The first cutting edges are identical to one another and offset from one another only in the circumferential direction, the angular distances resulting from a full circle divided by the number of first cutting edges.

Yet another embodiment of the invention provides for a plurality of second cutters, which in turn are symmetrical, i. are arranged at mutually equal angular intervals to the cutter axis.

Conveniently, the number of first cutting edges and second cutting edges are the same, in which case, according to a further embodiment, the first cutting edges and the second cutting edges are arranged alternately in the circumferential direction of the milling cutter. However, the angular distances between the immediately consecutive cutting edges may vary, i. H. the alternating first and second cutting edges have different angular distances from adjacent cutting edges, respectively, wherein, viewed in the direction of rotation, the angle from one first cutting edge to the next second cutting edge is greater than the angle from this second cutting edge to the next following first cutting edge.

When the first cutting edges reach the center of the milling cutter, the second cutting edges in the center of the milling cutter are sharpened within an inner radius r ₄ , so that in the sharpened region of the second cutting edges, only the first cutting edges can cut material in the case of an axial feed.

The first cutting edges may, according to one embodiment of the invention, be composed of a plurality of sections which include different positive or negative angles with a perpendicular to the cutter axis. In particular, the first cutting edge, starting from the axis of the milling cutter, has the following course:

A first section is angled forwards, correspondingly encloses a negative angle αi with a plane perpendicular to the axis and extends in the radial direction up to a radius rv. A second section adjoining this first section is in axial direction - -

Direction back angled and thus includes a positive angle α ₂ with the plane perpendicular to the axis. The second section extends between the radii ri and r ₂ . A third section, which adjoins the second section in the radial direction, again encloses a negative angle 0 ₃ with the plane perpendicular to the axis, this section extending from a radius r ₂ to a radius r ₃ which is at most equal to Nominal radius R of the cutter is, however, according to one embodiment, the radius r _{3 is} smaller than the nominal radius R, so that the first cutting edge according to this embodiment has an optional fourth outer portion extending from the radius r ₃ to the nominal radius R and at most a small angle between + 2 ° and -2 ° with the plane perpendicular to the axis.

The second cutting edge is, as already mentioned, according to an embodiment of the invention, pointed up to an inner radius r ₄ and thus begins at the radius η, from where it extends to an outer radius r ₅ which corresponds at most to the nominal radius R, Here, too, the option exists that when the outer radius r _{5 is} smaller than the nominal radius R, and the second cutting edge has a further outer portion which extends from the outer radius r ₅ to the nominal radius R, said outer portion with the plane perpendicular to the axis forms an angle α ₅ between + 2 ° and -2 °. Conveniently, each optionally provided outer portions of the first cutting edge and the second cutting edge are at the same axial height, and they are also the axially most projecting portions of the first and second cutting edges. Also, the radial length and any curvature of the radially outer portions of the first and second cutting edges are suitably identical. Also, any inclination relative to a plane perpendicular to the cutter axis could be identical for the outer portions of the first and second blades, respectively, and the respective angles or radii of curvature of the radially outer portions of the first and second blades may also be slightly different. The latter outer sections of the first and second cutting edges, which also project furthest axially, generate the smooth workpiece surface facing the front side of the milling cutter during the lateral advancing movement of the milling cutter, and are thus effectively plane cutting. Of course, the maximum lateral feed of the cutter per cutting edge should at most correspond to the radial length of these outer cutting edge sections.

With respect to the angles of the various sections of the blades, according to an embodiment of the invention, the angle α _{4 should be} smaller than the angle α _{3 in} absolute terms, with the optional radially outer portion of the first blade being at the same axial height - -

is like the radially outer portion of the second cutting edge and wherein the cutting portions having the angles 0 ₃ and cu, respectively, connect to the radially inner ends of the radially outer portions. This effectively acts so that the inner portion of the second cutting edge, which includes the positive angle cu with a plane perpendicular to the axis, extends axially beyond the approximately in the same radial region cutting edge portion of the first cutting, which at a negative angle 0 ₃ with respect to a Perpendicular to the axis of the cutter is inclined.

Radially inner cutting portions, which have a relatively greater inclination with respect to a plane perpendicular to the cutter axis, according to one embodiment are set back in the axial direction relative to radially outer cutting portions or at most reach the axial position of the outer portions, without protruding therefrom. This ensures that these inclined cutting portions have no adverse influence on the production of a smooth workpiece surface on the front side of the milling cutter.

Preferably, such radially inner cutting portions, which are inclined with respect to a plane perpendicular to the cutter axis compared to the outer portions, an inclination of a maximum of 30 °, preferably a maximum of 20 ° and a minimum of 5 °, optionally also at least a portion of the inner Cutting sections without appreciable inclination, d. H. parallel or less than 2 ° to this plane.

Radially inner cutting portions which have a relatively greater inclination with respect to a plane perpendicular to the cutter axis may optionally define at least one tip, which may optionally be rounded.

The tip formed by inner cutting portions which have a relatively greater inclination with respect to a plane perpendicular to the cutter axis is, according to one embodiment, less than 2 mm, preferably less than 1 mm and in particular between 0.1 and 0, in the axial direction compared to radially outer portions , 5 mm set back.

According to one embodiment, the optionally rounded tip is formed solely by cutting portions of the first cutting edge.

Other advantages, features and applications of the present invention will become apparent from the following description of a preferred embodiment and the accompanying drawings in which: Figure 1: a perspective view of an end mill according to the invention

FIG. 2 shows a detail enlargement from FIG. 1 and FIG

Figure 3: the cutting edge profile of the first and the second cutting, which are shown axially offset from each other in the figure.

It can be seen in Figure 1, a generally designated 100 end mill, which consists of a clamping end or shaft 60 and a cutting part 50. The cutting part is shown enlarged again in FIG. 2, so that details of this cutting part can be better recognized. It can be seen in the present case, a cutting part 50 with a total of four cutting edges, two of which are first cutting edges 10 and two cutting second cutting 20, wherein the first cutting 10 are diametrically opposite each other in pairs and also the second cutting edges 20 in pairs diametrically opposite lie. For better identification of the cutting edge course, the adjacent to the cutting edges open spaces 1 1 and 21 are shown hatched, while lying in front of the cutting edges clamping surfaces 12 and 22 are not hatched, in this perspective view, only two of the clamping surfaces are visible and the cutting edges themselves each as a section lines of the open spaces 11 and 21 with the respective rake surfaces 12 and 22, respectively.

3 shows the profile of the cutting edges 10 and 20 in a side view and sectional view, wherein the upper part of Figure 3 corresponds to an axial section through the cutter, which lies in the plane of the first cutting edge 10, while the lower part of Figure 3 shows a relation to the sectional plane of the upper part about 90 ° twisted axial section showing the two diametrically opposed second cutting edges 20. In order to make the different cutting edges more visible, the two sections are shown axially offset. For a better comparison, the position of a second cutting edge 20 in the projection on the first cutting edge 10 is also shown in broken lines in the upper part on the left side, so that it becomes clear that the two outer cutting edge portions 5 of the first cutting edge 10 and 15 of the second Cutting edge 20 coincide.

As used herein, the terms "first cutting edge" and "second cutting edge" each refer to one half of the cutting edges discernible at the top and bottom respectively, ie the first cutting edge begins at the center of an axis 30 of the milling cutter with a first cutting edge section 1, the definition chosen here is a negative angle αi with one to the axis 30 of the milling cutter vertical plane 40 includes. At this first radially inner portion 1 of the first blade 10 is followed by a second portion 2 of the first blade 10, which extends at a positive angle α ₂ to the plane 40 inclined. Both cutting edge sections 1 and 2 together form a flat roof shape with a tip 7, which may optionally be rounded with a small radius. At the radially outer end of the second section 2, in turn, a third section 3 of the first cutting edge 10 connects, which again inclined at a negative angle α ₃ to the plane 40 and to the radially outer end of this section 3 still includes the radially outer portion 5 at which is inclined approximately parallel to the plane 40 or at a slight angle of less than ± 2 ° relative to the plane 40 and which may also have a curvature, the corresponding radius of curvature being at least equal to the nominal radius R of the mill.

Mirroring the first cutting edge 10 just described, one recognizes another first cutting edge 10 on the other side of the axis 30.

The second cutting edges 20 can be seen in the lower part of Figure 3, where these cutting axially offset from the first cutting edge are shown, but in fact are axially also in the first cutting, in such a way that the respective outer portions 5 or 15 are at the same axial height.

The second cutting edges 20 are in the center, ie in the vicinity of the axis 30 of the milling cutter, pointed. These Ausspitzungen 8 ensure that a sufficient chip space is available in front of the radially inner cutting edge portions 1 of the first cutting. Starting from the axis 30 of the milling cutter, the second cutting edge 20 only begins at a radius r "which corresponds approximately to the radial length ri of the first section 1 of the first cutting edge, but which may also be larger or slightly smaller. The radially outwardly extending first portion 14 of the second cutting edge 20 extends therefrom at a negative angle α ₄ relative to the plane 40, which represents a plane perpendicular to the cutter axis 30. Outwardly adjoins thereto the already mentioned section 15, which coincides in this embodiment in length, slope and axial position with the outer portion 5 of the inner blade 10. This can be seen in particular in the upper left part of Figure 3, where the cutting edge portion 14 of the second cutting in the axially correct position and in the plane of the first blade 10 projected is shown in dashed lines and where the sections 5 and 15 coincide. However, as can be seen from the curve of the dotted portion 14 as compared to the section 3 in the upper part image of Figure 3, the portion 14 of the second cutting edge at an angle α ₄ to the axis 40 is inclined, which is smaller than the angle α ₃ around which the portion 3 of the first cutting edge 10 is inclined relative to this plane 40. This means that the section 14 extends axially in front of the section 3 and thus cuts or processes regions of the workpiece which can no longer be grasped by the section 3 of the first cutting edge 10, which recess is correspondingly axially offset. As can be further seen in the upper left partial image of Figure 3, the dashed line 14, which represents the second cutting edge 20, in this projection intersects the second section 2 of the second cutting edge at a radius ri, measured from the axis 30 of the milling cutter. As a result, three different regions, namely a radially inner region a, corresponding to the radius r, in which the dashed line portion 14 of the second cutting edge 20 intersects the second portion 2 of the first cutting edge 10, a second, the region a annular surrounding region b which is between this radius n and another radius r _a and which simultaneously marks the radially outer end of the cutting edge portion 14 of the second cutting edge and the cutting edge portion 3 of the first cutting edge, and a region c which annularly surrounds the region b with a radial dimension which corresponds to the length of the outer portions 5 and 15 of the blades 10 and 20, respectively.

In the case of an axial feed of the milling cutter, the area a is machined exclusively by the cutting edges 1 and 2 approximately up to the radius η. In the area b between η and r _a , the cutting work is performed almost exclusively by the section 14 of the second cutting edge 20 and in the section 10, the cutting is effected equally by the outer cutting portions 5 of the first blade 10 and 15 of the second blade 20, respectively.

In this case, the axial positions and angles of inclination of the cutting edge sections 1 and 2 are dimensioned such that the tip 7 formed between these cutting sections, which may possibly be flattened or rounded, is set back slightly axially relative to the radially outer sections 5 and 15, typically by about a distance of not more than 2 mm, preferably less than 1 mm. This distance may be reduced to the value 0, but the tip 7 should not protrude axially from the outer portions 5, 15 as far as possible.

As can be seen from this cutting geometry, cause the symmetrically arranged, roof-shaped tips 7 of the two blades 10 centering at an axial feed, since the adjacent cutting edge portions with respect to the axis of the cutter vertical plane inclined and are formed symmetrically, so that any reaction forces exerted by the engagement of the respective cutting edge sections 1, 2 with the workpiece on the cutter, compensate each other, the angles αi and 0 ₂ and the respective radial lengths Sections 1 and 2 are preferably selected so that the radial forces, which are generated by the engagement of the cutting edge sections 1 and 2 with the workpiece, compensate for each of the blades 10 and, as far as such compensation is not already reached on one side This is achieved in any case because of the symmetrical design and arrangement of the two blades 10 and optionally further cutting 10.

The two cutting edge portions 14 of the second cutting edges 20 are also arranged mirror-inverted or symmetrical to each other, so that also compensate for the engagement of these cutting edge portions with the workpiece in the radial direction acting on these blades reaction forces.

As a result, a good centering effect and guidance is achieved even with an axial feed movement of such an end mill, so that the cutter does not deviate laterally in any direction. At the same time, at least the first cutting edges have a cutting edge course, which in principle is modeled on the cutting edge profile of some drills, even if drill cutting edges with corresponding roof-shaped cutting edge progressions are generally not arranged symmetrically with respect to the axis of a drill. By the Ausspitzungen 8 of the second cutting, which do not reach to the center and by bringing the first cutting to the center, on the one hand sufficient chip space is available and on the other hand, the cutting is also down to the center of the milling machine, which is the axial Feed movement considerably easier.

For purposes of the original disclosure, it is to be understood that all such features as will become apparent to those skilled in the art from the present description, drawings, and claims, even though they have been specifically described only in connection with certain further features, both individually and separately any combination with other of the features or feature groups disclosed herein are combinable, unless this has been expressly excluded or technical conditions make such combinations impossible or pointless. On the comprehensive, explicit representation of all conceivable combinations of features is omitted here only for the sake of brevity and readability of the description.

Claims

Patent claims

1. End mill with a plurality of end cutting edges (10, 20), of which at least one first (10) extends to the axis (30) of the milling cutter, characterized in that the cutter at least one further, from the first end cutting edge (10) different second end cutting edge (20), wherein the axial position and formation of the first cutting edge (10) and the second cutting edge (20) are provided such that upon axial immersion of the rotating milling cutter into a workpiece, a radially inner region (a) only through the first Cutting edge (10) from the axis (30) of the cutter to a first radius (η) which is smaller than the nominal radius and greater than a radially inner radius of the second cutting edge, and that in a second region (b), the between the radius η and a larger radius r _a , which can assume the maximum value of the nominal radius (R) of the milling cutter, only the second cutting edge (20) intersects.

An end mill according to claim 1, characterized in that the outer radius (r _a ) to which the second cutting edge (20) intersects is smaller than the nominal radius (R) of the milling cutter, the range (c) being between the radius (2). r _a ) and the nominal radius (R) in the axial immersion of the milling cutter in a workpiece substantially equally by both cutting edges (10, 20) is machined.

3. end mill according to claim 1 or 2, characterized in that a plurality of first cutting edges (10) are arranged symmetrically to the cutter axis.

4. end mill according to one of claims 1 to 3, characterized in that a plurality of second cutting edges (20) are arranged symmetrically to the cutter axis.

5. End mill according to one of claims 1 to 4, characterized in that the first (10) and second cutting edges (20) are arranged alternately in the circumferential direction of the milling cutter.

6. end mill according to one of claims 1 to 5, characterized in that the second cutting edges (20) in the center of the milling cutter within an inner radius (r,) are sharpened.

7. Cutting insert according to one of claims 1 to 6, characterized in that the alternating first and second cutting to each adjacent cutting edges have different angular distances, wherein, viewed in the direction of rotation, the angle of a first cutting edge (10) to the second cutting edge (20 ) is greater than the angle, viewed in the direction of rotation, from a second (20) to a first cutting edge (10).

8. end mill according to one of claims 1 to 7, characterized in that the first cutting edge of a plurality of relative to the axis inclined cutting edge portions (1, 2, 3, 5), said portions, starting from the axis (30) of the milling cutter following Have a course:

A first portion is angled forwardly and accordingly includes a negative angle (α-i) with a plane perpendicular to the axis, a second portion (2) adjacent the first portion (1), angled back in the axial direction, and in order to include a positive angle (α ₂ ) with a plane perpendicular to the axis, a third section (3) adjoining the second section (2) adjoins a negative angle (α ₃ ) with the plane perpendicular to the axis and is extends to a radius (r ₂ ) at most equal to the nominal radius (R) of the mill, and optionally, when the radius (r ₂ ) is less than (R), a fourth outer portion (5) extending to to the nominal radius (R) extends, and which encloses with the plane perpendicular to the axis an angle between + 2 ° and -2 °.

9. End mill according to one of claims 1 to 8, characterized in that the second cutting edge (20) has an inner portion (1 1) extending from an inner radius (η) to an outer radius (r _a ), the is at most equal to the nominal radius, and if the outer radius (r _a ) is less than the nominal radius (R) has a second outer portion (6) extending from the outer radius (r _a ) to the nominal radius (R) extends and with the plane perpendicular to the axis forms an angle α ₅ between + 2 ° and -2 °.

10. End mill according to one of claims 8 and 9, characterized in that the angle α _{4 is} smaller in magnitude than the angle α ₃ and that the optionally present radially outer portion (4) of the first cutting edge (10) is at the same axial height such as the radially outer portion (12) of the second blade (20), the radially outer portions (4, 12) being at substantially the same axial height.

1 1. End mill according to one of claims 1 to 10, characterized in that the optionally present radially outer portions (5, 15) in a projection of the second cutting edge (20) on the first cutting edge (10) at the same axial height are superimposed, wherein the radius (r ₂ ) is equal to the outer radius (r _a ), the radially inner portion (11) of the second blade (20) lies axially in front of the third portion (3) of the inner blade and the inner portion (11) of the inner blade second cutting edge (20) intersects the second portion (2) at a distance from the ends thereof.

12. End mill according to one of claims 1 to 11, characterized in that radially inner cutting portions (1, 2, 3, 14) which have a relative greater inclination with respect to a cutter axis (30) vertical plane (40), relative to radially outer cutting portions (5, 15) are set back in the axial direction or at most reach the axial position of the outer sections, without protruding over this.

13. end mill according to one of claims 1 to 12, characterized in that radially inner cutting portions (1, 2, 3, 14) with respect to a plane perpendicular to the cutter axis plane (40) has an inclination of a maximum of 30 °, preferably a maximum of 20 ° and minimal Have 5 °,

14. end mill according to one of claims 1 to 13, characterized in that radially inner cutting portions (1, 2, 3, 14) which have a relative greater inclination relative to a plane perpendicular to the cutter axis (40), at least one optionally rounded tip (7 ) define.

15. End mill according to claim 14, characterized in that one of inner cutting portions (1, 2, 3, 14), which have a relative greater inclination with respect to a plane perpendicular to the cutter axis, formed tip in the axial direction relative to radially outer portions (5, 15) is set back by less than 2 mm, preferably less than 1 mm and in particular between 0.1 and 0.5 mm.

16. end mill according to one of claims 14 or 15, characterized in that radially inner cutting portions (1, 2, 3) which have a relative greater inclination with respect to a cutter axis (30) vertical plane, and at least one optionally rounded tip (7) define, are only cutting portions (1, 2, 3) of the first cutting edge (10).