WO2006079317A1

WO2006079317A1 - Variable cutting edge removal for drilling tools

Info

Publication number: WO2006079317A1
Application number: PCT/DE2006/000090
Authority: WO
Inventors: Roland Alber
Original assignee: Firma Gühring Ohg
Priority date: 2005-01-25
Filing date: 2006-01-20
Publication date: 2006-08-03
Also published as: DE102005003496A1

Abstract

The invention relates to a drilling tool (2) with at least one main cutting edge (4), which is broken by grinding a protective chamfer (8), and to a method for making a protective chamfer (8) on the main cutting edge (4). According to the invention, the size and/or the position and/or the geometry of the protective chamfer (8) varies over the length of the cutting edge (14).

Description

description

Variable cutting edge trigger for drilling tools

The invention relates to a drilling tool with at least one main cutting edge, which is broken by grinding a Schutzfase, according to the preamble of claim 1. Furthermore, the invention relates to a method for attaching a protective chamfer on the main cutting edge according to the preamble of claim 13.

An essential goal in the production of cutting tools is to increase the service life of the

Tools in their application. As a lifetime, the

Period of time during which a tool for a given life criterion under given

Spanungsbedingungen Span doing, d. h is the time between two cuts. The economic

The use of a drill is strongly dependent on the service life, which in turn is influenced by the following factors: cutting speed, feed rate,

Coolant, cutting angle, cutting size, cutting material, shape, depth of holes and materials.

One way to reduce the wear on the cutting edge is to provide it with a Schnagfase, so as to increase the service life. By grinding or brushing, a rounding or small chamfer is applied to the sharp edge and, as it were, microscopically "defused" the cutting edge.

Such protective chamfers are used in particular for inserts, but also for drilling tools application. Since a cutting edge can not be made arbitrarily sharp microscopically, one obtains a defined geometry of the cutting edge through the protective chamfer. This is particularly important because the geometry of the cutting edge is ideally matched to the cutting speed, feed rate and material of the workpiece tool and tool.

For indexable inserts, cutting edges with protective chamfers of different widths and chamfer angles are therefore used, depending on feed rate and material.

In drilling tools with ground main cutting one has gone over to the life of the tool by better and better cutting materials such. B. Hatartmetall with ever finer grain size, increase. Nevertheless, it turns out that even with extremely careful attachment of the protective chamfer uncontrolled cutting wear occurs.

The present invention is therefore based on the object to provide a tool with at least one main cutting edge, which achieves a much longer service life without device-technical and economic effort.

This object is achieved in terms of the tool by the features of claim 1, with respect to the method by the method steps of claim 13.

The invention is based on the idea that in drilling tools, the cutting speed directly from the

Peripheral speed and thus of the local situation of the considered cutting point, d. H . from the distance to the drill axis. Thus, the cutting edge has over its length very different cutting speeds and directions, which is why in a uniform bevel geometry, as z. B. from EP 0 690 758 is known, the cutting edge can be optimally designed only for one point. According to the invention, however, the at least one main cutting edge is provided with a protective chamfer whose size and / or position and / or geometry varies over the length of the cutting edge.

By varying the above-mentioned properties of the protective bevel, a tool is obtained having a cutting edge that is varied depending on the distance from the drill axis and optimized at each point. This ensures that the protective bevel of the cutting edge at the respective point has the optimum geometric properties in terms of cutting speed and - direction.

In addition to increasing the service life, the feed force can be further reduced due to the inventive design of the cutting edge.

Advantageously, the protective chamfer is designed such that the cutting wedge formed by the free surface and the cutting surface over a significant length of the main cutting becomes dull with increasing distance from the drill axis.

Towards the drill axis takes the

Cutting rate from increasing until it is finally zero in the drill axis. To ensure sufficient cutting performance, the cutting edge must be sharper at lower cutting speeds than at higher cutting speeds. That's why it does - A -

Sense to make the main cutting edge dull with increasing distance from the drill axis in order to keep the wear on the cutting edge as low as possible, while ensuring a sufficient cutting performance.

In this case, another effect is added: since the rake angle increases in the direction of the drill axis due to the helical shape of the rake surface, the wedge angle increases at about the same rake angle. h .. the cutting edge is blunt towards the drill center axis, which is counterproductive for the cutting behavior. Due to a variable design of Schutzfase this fact can be counteracted.

The protective bevel can be designed in different ways. In terms of manufacturing technology, it is very easy to realize a chamfer in the form of a flat fold of the cutting edge. Such a flat surface substantially increases the cutting edge thickness and protects it against breakouts.

In an advantageous embodiment, the protective bevel is designed such that its width B increases over a significant length of the main cutting edge with increasing distance from the drill axis. As a result, the sharpness or the dullness of the cutting edge can be adjusted in a very simple manner.

Another possibility is to regulate the sharpness or dullness of the cutting edge by changing the angle which the protective bevel encloses with the axial plane of the tool.

It has been found that this angle in the outer region of the cutting edge is preferably in the range of 0 ° up to 40 ° and in the vicinity of the core diameter in the range of -30 ° to -10 ° or 60 ° to 90 ° of. Of course, the bevel angle depending on the application, depending on feed, materials, etc. also outside these angular ranges. However, it should be ensured that the cutting edge becomes dull with increasing distance from the drill axis.

The width of the protective chamfers are advantageously at the outer end of the cutting edge and depending on the application in a range of approx. 15 to 20 μm. Despite these microscopically small dimensions, these protective chamfers considerably contribute to increasing the service life of tools.

In addition to planning folds of the cutting edge, the

Protective chamfers also have a convex surface. This is advantageous, among other things, if the material of the

Workpiece is softer or the cutting depths are lower.

With convex round protective bevels, the sharpness of the

Cutting edge are set over the radius of the rounding, wherein the radius increases over a significant length of the main cutting edge with increasing distance from the drill axis.

To attach the protective chamfer on the cutting edge, all known abrasive methods, but especially loops are suitable.

The abrasive body can be brought either from the side of the free surface or from the side of the rake face to the cutting edge. Advantageously, the grinding process is carried out for each main cutting edge in a single uniform movement of the grinding wheel and / or the drilling tool, ie. Either the grinding body is brought to a fixed tool accordingly, the tool guided by means of a corresponding device to the grinding wheel or both guided in a coordinated Bewegunsablauf each other.

According to the invention, the abrasive body follows the course of the main cutting edge and thereby increases its delivery and / or its grinding angle with respect to the chip surface or the free surface with increasing distance from the drill axis, so that the cutting edge is provided with a protective chamfer, the vin over a significant length inside outside becomes duller. In this case, a translational and a rotational movement of the grinding wheel or of the tool can overlap, so that both the angle and the width of the protective bevel changes depending on the radial distance from the drill axis after machining the edge.

Hereinafter, preferred embodiments of the invention will be explained in more detail with reference to schematic drawings. Show it :

Fig. 1 is a plan view of a tool according to the invention according to a first embodiment;

Fig. FIG. 2 shows the schematic side view II from FIG. 1 of the tool according to the invention according to the first embodiment; - T -

Fig. FIG. 3 is a cross-sectional view of a protective chamfer cutting edge according to the first embodiment of the present invention during the cutting operation; FIG.

Fig. 4 is an enlarged cross-sectional view of a cutting edge according to the first embodiment;

Fig. FIG. 5A shows a schematic cross-sectional view of a cutting edge-like cutting edge according to the invention with protective bevel according to the first embodiment; FIG.

Fig. FIG. 5B shows a schematic cross-sectional view of a protective bevel cutting edge according to the invention which is remote from the cutting edge according to the first embodiment; FIG.

Fig. 6A is a schematic cross-sectional view of a cutting edge near cutting edge according to the invention with protective bevel according to the second embodiment;

Fig. 6B is a schematic cross-sectional view of a cutting edge remote inventive cutting edge with protective chamfer according to the second embodiment;

Fig. 7A is a schematic cross-sectional view of a cutting edge near cutting edge according to the invention with protective bevel according to the third embodiment;

Fig. FIG. 7B shows a schematic cross-sectional view of a protective bevel cutting edge according to the invention which is remote from the cutting edge and away from the cutting edge;

Fig. 8A is a schematic cross-sectional view of a cutting edge near cutting edge according to the invention with protective bevel according to the fourth embodiment; Fig. 8B is a schematic cross-sectional view of a cutting edge remote protective edge of the invention according to the fourth embodiment;

Fig. FIG. 9A is a schematic cross-sectional view of a cutting edge near protective edge according to the fifth embodiment of the invention; FIG.

Fig. FIG. 9B is a schematic cross-sectional view of a cutting edge remote protective cutting edge according to the fifth embodiment of the present invention; FIG.

Fig. 10A is a schematic cross-sectional view of a cutting edge near cutting edge according to the invention with protective bevel according to the sixth embodiment;

Fig. 1OB is a schematic cross-sectional view of a cutting edge remote inventive cutting edge with protective chamfer according to the sixth embodiment;

Fig. 11 shows a schematic cross-sectional view of a cutting edge according to the invention and an abrasive body before the grinding process according to the invention;

Fig. 12A shows a schematic cross-sectional view during the grinding process according to the invention of a cutting edge near the cutting edge and an abrasive body according to a first and second embodiment;

Fig. 12B shows a schematic cross-sectional view during the grinding process according to the invention of a cutting edge remote cutting edge and an abrasive body according to the first embodiment;

Fig. 12C is a schematic cross-sectional view during the grinding process according to the invention Schneideckfernen cutting edge and a grinding wheel according to the second Auführungsform;

13A shows a schematic cross-sectional view during the grinding process according to the invention of a cutting edge near the cutting edge and a grinding body according to a third and fourth Auführungsform;

Fig. 13B shows a schematic cross-sectional view during the grinding process according to the invention of a cutting edge remote cutting edge and an abrasive body according to the third embodiment; and

Fig. 13C shows a schematic cross-sectional view during the grinding process according to the invention of a cutting edge remote cutting edge and an abrasive body according to the fourth embodiment;

1 shows an inventive tool 2 with main cutting edges 4 and a transverse cutting edge 6, in which the main cutting edges 4 are provided with a protective chamfer 8. In this case, the protective chamfer 8 extends from the radially outermost point of the main cutting edge 4, the cutting edge 10, in the direction of the core diameter 12.

FIG. 2 shows the side view II from FIG. 1, in which a Schutzfase invention 8 at a cutting edge 14 exaggerated size - for illustrative purposes not to scale - is shown. Furthermore, a free surface 16 and a rake surface 18 are shown. The rake faces 18 are in this case the end sections of two helically milled flutes 20. The main cutting edges 4 on the drill 2 are formed by conically grinding the drill end section. Depending on the application, d. H . the material of the material and the drill, the feed rate, the depth of the hole, etc. , find the most different types of twist drills with different geometries and cuts application. The inventive design of the cutting edges 14 with a protective chamfer 8 is applicable to each of these jigs.

In Fig. 3 is a very greatly enlarged cross-section of the cutting edge 14 of the invention is shown, ^' which is arranged in the transition of clamping surface 18 and free surface 16. In this case, the rake surface 18 and the free surface 16 forms a cutting wedge 22 which separates a chip 24 from a workpiece 26. Depending on various parameters, such as cutting speed and material of the workpiece 26, it comes that the chip 24 cut less than rather is torn off over a initiated by the cutting wedge 22 tensile or bending force from the workpiece 26. This creates a so-called leading crack 28, so that the actual cutting edge 14 is not in direct contact with the chip 24. The size of the leading crack 28 depends in particular on the cutting speed and the material of the workpiece 26. Depending on this, the protective chamfer 8 can be made larger or smaller.

The size of the cutting edge 14 also depends in particular on the grain size of the drill material used. The finer the carbide, the sharper the cutting edge can be made and the lower the resulting temperature development.

In the following, with reference to FIG. 4 shows the geometry of a cutting edge 14 according to the invention.

For orientation, the feed direction with an arrow V and the circumferential direction with an arrow U indicated. The clamping surface 18 includes the free surface 16 a wedge angle ß. A clearance angle α defines the inclination of the free surfaces 16 to the workpiece 26. The angle between rake face 18 and an axial plane 30 is defined as the rake angle γ. If the cutting edge 14 or the cutting wedge 22 is provided with a phase 8 at an angle ε with respect to the axial plane 30, the cutting edge 14 is "defused". This results in a cutting edge angle (p] _, which encloses the protective chamfer 8 with the rake face 18, and the cutting edge angle φ 2, the protective chamfer 8 with the flank 16 includes.

Various embodiments of the cutting edge 14 according to the invention with the protective chamfer 8 on the tool 2 are shown below.

Since the cutting edge 14 is exposed with increasing distance from the drill axis A higher peripheral speeds and thus higher cutting speeds, occur on derselbigen also increasingly wear. According to the invention it was recognized that these wear phenomena can be better controlled by a variable design of the protective chamfer 8. According to one of FIGS. 3a and 3b, this realization is implemented in such a way that the width B is varied over a significant length of the main cutting edge 4. Fig. 5a shows the section AA from FIG. 1, ie. a section through a further outward portion of the cutting edge 14. Compared to FIG. 5b, which shows the section BB through a further inner portion of the cutting edge 14 of FIG. 1, it can clearly be seen that the width B of the protective chamfer 8 becomes larger towards the outside and thus duller. As a result, on the one hand in the vicinity of the drill center axis A, where the cutting speeds are lower, ensuring sufficient cutting performance and on the other hand near the cutting corner 10, where very high peripheral speeds and cutting speeds, minimizes wear. Due to this inventive design of the protective chamfers 8 at the cutting edges 14, it is possible to find an optimal design with regard to cutting behavior and wear for each point of the main cutting edge.

According to a second and a third embodiment of the invention - see FIG. 6a, 6b or 7a, 7b - a similar effect according to the invention is achieved if the chamfer angle ε of the protective chamfer 8 at the cutting edge 14 varies depending on the local position of the considered cutting point. Also in these figures, the index "a" for the section A-A of FIG. 1 and the index "b" for the section B-B of FIG. 1 used. At the outer portion of the cutting edge 14 (FIGS. 6 a, 7 a,), the chamfer angle ε is preferably selected such that the cutting edge angles (p) and q> 2 are each greater than 90 °, so that a relatively blunt cutting edge 14 is formed As the cutting edge 14 is to become sharper as the distance to the drill axis A decreases, the chamfer angle ε can either be increased towards the drill central axis A as shown in Fig. 6b or reduced in size as shown in Fig. 7b > i and (p2 substantially smaller than the other and the cutting edge 14 overall sharper.) These variants of the protective chamfers therefore also solve the object underlying the invention and increase the service life of the tool.

Of course, it is also possible depending on the distance from the drill axis A to change both the width B and the angle ε of Schutzfase 8. there the cutting edge 14 at the outer portion should have a greater width B and rather blunt cutting edge angles φ 1 and φ 2, and decrease in width B and the chamfer angle ε either much larger (see Fig. 8b) or smaller (see Fig. 9b ) become .

In the embodiments shown above, the protective chamfer 8 has a planar surface. However, it is also possible, for example, to provide the cutting edge 14 with a convex or round protective chamfer 8 with softer workpiece materials or with lower feeds. In this case, the sharpness or dullness of the cutting edge 14 over the radius of curvature R of Schutzfase 8 can be adjusted. In other words, with increasing distance from the drill center axis A according to the invention, the radius R of the protective chamfer 8 increases.

It has been found that the width B of the protective chamfer 8 at the radially outer end are approximately in a range of 15 to 20 μm. The chamfer angle ε should be set so that this at the radially outer end approximately in a range of 0 to 40 ° and in the inner region, ie in the vicinity of the core diameter, either in a range of -30 ° to -10 ° or 60 ° should be up to 90 °. Of course, it can be used here in special applications, eg. B. with a negative rake angle γ, deviations from this occur. The protective chamfer 8 should at least be designed so that it becomes larger or blunter with increasing distance from the drill central axis A.

In the following, the method for producing a tool according to the invention will now be discussed in greater detail.

The cutting edge 14 on the tool 2 is by means of an abrasive method, for. B. by grinding, brushing, Honing etc., provided with the protective chamfer 8. The protective bevel 8 is controlled by a machine in a single movement of the grinding body 32 or. of the drilling tool 2 along the main cutting edge 4. When using a multi-axis controlled grinding system can follow the course of the main cutting edge 4 in a single step, the feed S and its grinding angle ε with respect to the clamping surface 18 or the free surface 16 depending on the distance from the drill axis A change such that the width B of Schutzfase 8 decreases from outside to inside and one of the two cutting edge angle φi and φ2 is sharpened from the outside inwards. It is incumbent on the respective application of the decision of the expert, whether the protective chamfer 8 more of the free surface 16 or more of the rake face 18 is attached to the cutting edge 14, ie. whether the grinding body 32 is brought from the side of the free surface 16 or from the side of the clamping surface 18 to the cutting edge 14. Likewise, it is to be decided on a case by case basis how large the feed value of the grinding wheel 32 is, since it essentially depends on the material of the drilling tool 2 used and the wedge angle β of the main cutting edge 4.

When attaching the protective chamfer 8, it is possible, as mentioned above, to bring the grinding body 32 by means of a multi-axis controlled device position-dependent to the cutting edge 14. However, it is also conceivable to clamp the drilling tool 2 in a multi-axis-controlled device and to bring it into contact with a positionally fixed grinding body 32. Of course, it is also possible today with the help of computer-aided devices, a movement of the grinding wheel 32 and a movement of the tool 2 to match so that even complicated Bohrwerkzeuggeometrien in a superimposed Movement of the grinding wheel 32 and drilling tool 2 can be edited.

Of course, deviations from the various embodiments described above are possible without departing from the spirit of the invention.

Thus, it is conceivable, the inventive idea, namely to make a protective chamfer 8 depending on the cutting speed, even with other machining methods such. B. milling or turning, if there are different cutting speeds on the cutting edges.

Claims

claims

Drilling tool (2) with at least one main cutting edge (4), which is broken by grinding a Schutzfase (8), characterized in that the size and / or the position and / or the geometry of the protective chamfer (8) over the length of Cutting edge (14) varies.

2. Drilling tool (2) according to claim 1, characterized in that the protective chamfer (8) is designed such that the of the free surface (16) and the clamping surface (18) formed cutting wedge (22) over a significant length of the main cutting edge (4 ) becomes blunter as the distance from the drill axis (A) increases.

3. drilling tool (2) according to claim 1 or 2, characterized in that the protective chamfer (8) has a substantially planar surface.

4. drilling tool (2) according to claim 3, characterized in that the width B of the protective chamfer (8) over a significant length of the main cutting edge (4) with increasing distance from the drill axis (A) increases.

5. Drilling tool (2) according to claim 3 or 4, characterized in that the angle (ε), the protective chamfer (8) with the axial plane of the tool (2) includes, with increasing distance from the drill axis (A) so changes in that the main cutting edge (4) becomes duller.

6. drilling tool (2) according to one of claims 1 to 5, characterized in that the width of the protective chamfer (8) at the radially outer end of the cutting edge (14) is preferably in the range of 15 to 20 microns.

7 »drilling tool (2) according to one of claims 3 to, characterized in that the chamfer angle (ε), the protective bevel (8) encloses with the axial plane, at the radially outer end of the cutting edge (14) preferably in the range of 0 ° to 40 ° and at the core diameter (12) in the range of - 30 ° to -10 ° or 60 ° to 90 ° of.

8. Drilling tool (2) according to one of claims 1 to 7, characterized in that the protective chamfer (8) and the rake face a first cutting edge angle φ] _ and the protective chamfer (8) and the flank face a second cutting edge angle q> 2, wherein the protective bevel (8) is designed such that at the outer end of the cutting edge (14) the angles φ ± and q> 2 are in each case greater than 90 ° and with decreasing distance to the drill axis (A) one of them substantially smaller than the other becomes.

9. drilling tool (2) according to one of claims 1 to 8, characterized by a positive rake angle (γ).

10. Drilling tool (2) according to claim 1 or 2, characterized in that the protective chamfer (8) has a convex

Has surface.

11. Drilling tool (2) according to claim 10, characterized in that the radius (R) of the convex surface changes over the length of the cutting edge (14).

12. Drilling tool (2) according to claim 10 or 11, characterized in that the radius (R) of the protective chamfer (8) over a significant length of the main cutting edge (4) with increasing distance from the drill axis (A) increases.

13. A method for attaching a protective chamfer (8) to the main cutting edge (4) of a tool (2) according to one of claims 1 to 11, characterized in that the protective chamfer (8) is ground.

14. The method according to claim 13, characterized in that the protective bevel (8) along the main cutting edge (4) in a uniform movement of the grinding wheel (32) and / or the drilling tool (2) is mounted.

15. The method according to claim 13 or 14, characterized in that the grinding body (32) follows the course of the main cutting edge (4) and its delivery (S) and / or its grinding angle (ε) with respect to the rake surface (18) or the free surface (16) increases with increasing distance from the drill axis (A).

16. The method according to any one of claims 13 to 15, characterized in that the cutting edge (14) from the side of the free surface (16) or from the side of the clamping surface (18) with a protective chamfer (8) is provided.

17. The method according to any one of claims 13 to 16, characterized in that the delivery (S) is in a range of 10 to 40 microns.