CUTTING TOOL FOR MACHINING FIBER COMPOSITE MATERIALS

Abstract

A cutting tool for machining fiber composite materials has clamping section and a cutting section which extend along a longitudinal axis. The cutting section has a basic cylindrical shape. First chipping flutes form left-hand spirals and second chipping flutes form right-hand spirals. Intersecting first and second chipping flutes form a plurality of discrete cutting elements on the cutting section. The cutting elements have a first circumferential cutting edge running along a left-hand spiral and a second circumferential cutting edge running along a right-hand spiral. The cutting edges run along a common enveloping cylinder surface that defines the outer circumference of the cutting section. The first and second circumferential cutting edges open into a common tip. Primary free surfaces adjoin the circumferential cutting edges in the circumferential direction and they adjoin one another along a first free surface edge.

Claims

1-14. (canceled)

15. A milling tool for machining fiber composite materials, the milling tool comprising: a clamping section and a cutting edge section extending along a longitudinal axis; said cutting edge section having a basic cylindrical shape; said cutting edge section having formed thereon a plurality of first chip flutes, formed as left-facing spirals, and a plurality of second chip flutes, formed as right-facing spirals, and wherein a plurality of discrete cutting elements are formed on said cutting edge section by way of intersecting said first and second chip flutes; said cutting elements having a first circumferential cutting edge running along a left-facing spiral and a second circumferential cutting edge running along a right-facing spiral, each extending along a common enveloping cylindrical surface that defines an outer circumference of said cutting edge section, and wherein said first and second circumferential cutting edges terminate in a common tip; at least a partial quantity of said plurality of cutting elements having a first primary clearance surface adjoining said first circumferential cutting edge in a circumferential direction and a second primary clearance surface adjoining said second circumferential cutting edge in the circumferential direction; said first primary clearance surface extending at a first primary clearance angle and said second primary clearance surface extending at a second primary clearance angle, and said first and second primary clearance surfaces adjoining one another along a first clearance surface edge.

16. The milling tool according to claim 15, wherein the partial quantity of the plurality of said cutting elements amounts to at least 80% of all of said cutting elements.

17. The milling tool according to claim 15, wherein said first and second primary clearance angles of said first and second primary clearance surfaces are equal and lie between 4 and 12.

18. The milling tool according to claim 15, wherein said primary clearance surfaces are adjoined by secondary clearance surfaces.

19. The milling tool according to claim 18, wherein said secondary clearance surfaces extend at secondary clearance angles and said secondary clearance angles are greater in amount than said primary clearance angles.

20. The milling tool according to claim 15, wherein a width of said primary clearance surfaces is between 0.040 times and 0.110 times a tool diameter of the milling tool.

21. The milling tool according to claim 15, wherein a number of said first chip flutes running along the left-facing spiral is different from a number of said second chip flutes running along the right-facing spiral.

22. The milling tool according to claim 15, wherein a spiral angle of said second chip flutes running along the right-facing spiral is different in amount from the spiral angle of said first chip flutes running along the left-facing spiral.

23. The milling tool according to claim 15, wherein at least one of said chip flutes running along a right-facing spiral is formed deeper and/or wider than at least one of said chip flutes running along the left-facing spiral.

24. The milling tool according to claim 15, wherein a ratio between a number of said chip flutes running along the right-facing spiral and a number of said chip flutes running along the left-facing spiral is 4:5.

25. The milling tool according to claim 15, wherein a ratio between a number of said chip flutes running along the right-facing spiral and a number of said chip flutes running along the left-facing spiral is 4:6.

26. The milling tool according to claim 15, wherein a ratio between a number of said chip flutes running along the right-facing spiral and a number of said chip flutes running along the left-facing spiral is 6:8.

27. The milling tool according to claim 15, wherein a width b.sub.LR of a first peripheral cutting edge LR is greater than a width b.sub.RR of a second peripheral cutting edge RR and a ratio between the width b.sub.LR and the width b.sub.RR lies between 1.1 and 1.5.

28. The milling tool according to claim 15, wherein a first internal angle of a cutting element facing in the longitudinal direction is smaller than a second internal angle of a cutting element facing in the circumferential direction.

29. The milling tool according to claim 15, wherein said cutting section has a hard material coating, at least in part thereof.

30. The milling tool according to claim 15, wherein a width of said left-facing first chip flutes is smaller than a width of said right-facing second chip flutes and a ratio between the widths of said chip flutes lies between 1.2 and 3.0.

Description

[0062] Further advantages and usefulness of the invention are disclosed with the aid of the following description of exemplary embodiments with reference to the accompanying figures.

[0063] In the figures:

[0064] FIG. 1: shows a perspective view of a milling tool according to the invention,

[0065] FIG. 2: shows a detail of the milling tool,

[0066] FIG. 3: shows a single cutting element,

[0067] FIGS. 4a and 4b show schematic sections through a cutting element,

[0068] FIG. 5: shows a section of the milling tool with marked section planes

[0069] FIGS. 6a and 6b show cross sections to the sectional planes drawn in FIG. 5

[0070] FIG. 7 shows a schematic and sectional view of the cutting edge area.

[0071] FIG. 1 shows a milling tool 100 according to the invention in an embodiment. The milling tool 100 has a basic cylindrical shape and comprises a shank section 1, used to clamp the milling tool, and a cutting edge section 2 which extend along a longitudinal axis Z. The milling tool 100 discussed here is intended for clockwise-rotating use, as illustrated by the rotation arrow of the direction of rotation R. Of course, milling tools intended for anti-clockwise-rotating use are also encompassed by the invention.

[0072] In the exemplary embodiment, the clamping section 1 is realized as cylindrical. Deviating therefrom or supplementary thereto, other shapes such as flattenings, polygons or threads are also possible.

[0073] A plurality of first chip flutes LS in the form of left-facing spirals and a plurality of second chip flutes RS in the form of right-facing spirals are formed on the cutting edge section 2 and by way of said intersecting first chip flutes LS and second chip flutes RS a plurality of discrete cutting elements 3 is formed on the cutting edge section 2.

[0074] The first chip flutes LS which are formed as left-facing spirals (facing to the left) run at a spiral angle with respect to the longitudinal axis Z. The spiral angle of the left-facing spiral chip flutes LS typically has an amount between 20 and 50, further preferred between 32 and 38, in particular 352, further preferred 351.

[0075] The (right-facing) chip flutes RS, which are formed as right-facing spirals, run at a spiral angle to the longitudinal axis Z.

[0076] In particular, the spiral angle of the right-facing spiral is between 20 and 50, especially 302, further preferred 301.

[0077] It is preferred that the amount of the spiral angle of the left-facing spiral is greater than that of the right-facing spiral.

[0078] In the present exemplary embodiment, the spiral angles are advantageously 35 for the spiral angle of the left-facing spirals and advantageously 30 for the spiral angle of the right-facing spiral.

[0079] In the exemplary embodiment, there is an advantageous number of four chip flutes along the right-facing spiral and an advantageous number of five chip flutes along the left-facing spiral.

[0080] The spiral angle is determined between a tangent to the relevant chip flute and the longitudinal axis Z in a true-angle view.

[0081] According to convention, the spiral angle (also: angle of twist) of right-facing spiral chip flutes is given as positive.

[0082] A plurality of discrete cutting elements 3 are formed by way of the intersecting left-facing and right-facing chip flutes. The cutting elements 3 havein geometrically simplified termsthe shape of truncated pyramids or studs and comprise a top surface that is square in a plan view. The shape of the top surface can, for example, be square or also have the shape of a parallelogram.

[0083] The shape is created by the spiral angle of the chip flutes and the respective chip flute profile.

[0084] In particular, the cutting elements 3, or more precisely their top surfaces, have the shape of a parallelogram in a plan view. In particular, the shape extends along the longitudinal axis Z.

[0085] Side flanks are formed on the cutting elements 3. Viewed in cross section, the shape of the side flanks in general corresponds to the shape of the respective chip flute. What is meant by this is that when the respective chip flute is introducedwhich is typically done by grinding with a grinding wheelthe contour thus introduced is present on the side flanks of the cutting elements 3. In general, the side flanks therefore have a curved course and a smooth transition to a base of the respective chip flute. This is favorable from a mechanical point of view.

[0086] For a clockwise-rotating use, as shown in the discussed exemplary embodiment, the right-facing chip flutes RS can be deeper and/or wider than the left-facing chip flutes LS. However, the right-facing chip flutes RS and left-facing chip flutes LS are both important for chip evacuation.

[0087] It is possible to provide that the spiral angle of the second chip flutes RS running along a right-facing spiral has a different amount than the spiral angle of the first chip flutes LS running along a left-facing spiral.

[0088] The milling tool 100 is in particular formed as a shank cutter. The clamping section 1 and the cutting edge section 2 are formed in one piece, in other words monolithically from a hard material, which can be, for example, a hard metal (cemented carbide), a cermet or a cutting ceramic. In particular, the milling tool 100 is preferably made entirely of hard metal, and is thus to be referred to as a so-called solid hard metal tool.

[0089] By hard metal is meant a composite material consisting predominantly of hard material particles which are surrounded and held by a ductile metallic binder. Most commonly, hard metal is one in which the hard material particles are formed at least predominantly of tungsten carbide and the metallic binder is a cobalt-based alloy or a nickel-based alloy.

[0090] In particular, the milling tool 100 is coated, preferably diamond coated.

[0091] Typically and preferably, the geometry of the cutting edge section 2 is produced by grinding a cylindrical hard metal rod (a blank).

[0092] FIG. 2 shows a section of the cutting edge area section 2 of a milling tool 100 according to the invention, again with the intended direction of rotation R indicated.

[0093] A cutting element 3 has a first circumferential cutting edge LR running along a left-facing chip flute LS and a second circumferential cutting edge RR running along a right-facing flute RS.

[0094] When engaging a workpiece during use in the intended direction of rotation R, the first circumferential cutting edge LR running along a left-facing spiral performs a pressing cut. Pressing cut means that the respective circumferential cutting edge LR exerts an axial force component on a workpiece to be machined in the direction of a face (tip) of the milling tool 100. Axial in this context means as facing parallel to the longitudinal axis Z.

[0095] In contrast, a circumferential cutting edge RR running along a right-facing chip flute RS acts with a pulling cut, which means that the circumferential cutting edge RS in question exerts an axial force component on a workpiece to be machined in the direction of the clamping section 1, in other words in the direction of the shank of the milling tool 100.

[0096] By forming both a circumferential cutting edge with a pulling cut and also a circumferential cutting edge with a pressing cut on a cutting element 3, the cutting element 3 has a neutral effect with regard to exerting an axial force on a workpiece. A workpiece is thus subjected to neither compressive nor tensile stress, which effectively prevents delamination.

[0097] It is preferred that all cutting elements 3 in the cutting edge area 2 are formed in this manner. Only in an end region and in a run-out region in the direction of the clamping section 1 are cutting elements 3 of a different design typically present.

[0098] It is preferred that the first circumferential cutting edges LR running along a left-facing spiral and the second circumferential cutting edges RR running along a right-facing spiral are of unequal length.

[0099] Overall, the plough-shaped arrangement of the circumferential cutting edges produces a particularly clean cut. Fibers of a fiber composite material are cleanly sheared and cut through by the design according to the invention. The low fiber protrusion after machining with a milling tool according to the invention is particularly advantageous.

[0100] Also indicated in FIG. 2 is a cylindrical surface ZM, which determines an outer circumference of the cutting edge section 2 and the tool diameterd. Both the first circumferential cutting edge LR and the second circumferential cutting edge RR extend along the common enveloping cylindrical surface ZM. In other words, the circumferential cutting edges LR, RR lie on an outer circumference of the milling tool 100.

[0101] Since the circumferential cutting edges extend along the common enveloping cylindrical surface ZM, the cutting conditions at the circumferential cutting edges are more favorable and smoother than, for example, with straight cutting edges. Furthermore, a large cutting edge length is available.

[0102] The first circumferential cutting edge LR and the second circumferential cutting edge RR terminate in a common tip 7.

[0103] FIG. 2 also illustrates the course of the chip flutes. The first chip flutes LS, which run along a left-facing spiral, run at a spiral angle to the longitudinal axis Z.

[0104] The second chip flutes RS running along a right-facing spiral run at a spiral angle to the longitudinal axis Z.

[0105] It can be seen from the contours of the chip flutes of the exemplary embodiment in FIG. 2 that the left-facing first chip flutes LS are formed to a lesser depth than the right-facing chip flutes RS.

[0106] This can be the case in a clockwise-rotating operation according to the exemplary embodiment. In this manner, more chip space is available, which has a chip-removing effect in the direction of the shank section 1.

[0107] It is preferred that the left-facing and right-facing chip flutes are of the same depth, because a chip flute that is too shallow represents a limitation in terms of chip removal.

[0108] The amounts of the spiral angles of the left-facing first chip flutes LS and the right-facing second chip flutes RS can be the same or different. It is preferred that the spiral angles are different.

[0109] FIG. 3 schematically shows a single cutting element 3 in detail. The direction of observation is opposite to the direction of rotation R. The first circumferential cutting edge LR and the second circumferential cutting edge RR terminate in a common tip 7.

[0110] A first primary clearance surface 5 is formed on the first circumferential cutting edge LR, and a second primary clearance surface 6 is formed on the second circumferential cutting edge, wherein the first primary clearance surface 5 and the second primary clearance surface 6 are adjacent to each other along a first clearance surface edge 8. The first primary clearance surface 5 runs at a first primary clearance angle .sub.1.

[0111] The second primary clearance surface 6, which is associated with the second circumferential cutting edge RR, runs at a second primary clearance angle .sub.1.

[0112] It is preferred that the primary clearance angles .sub.1, .sub.1 are equal.

[0113] As illustrated in the exemplary embodiment, it is preferably provided that further, secondary clearance surfaces adjoin the primary clearance surfaces. Thus, it is preferably provided that a first secondary clearance surface 9 adjoins the first primary clearance surface 5 and said secondary clearance surface 9 extends at a first secondary clearance angle .sub.2.

[0114] Adjacent to the second primary clearance surface 6 is the second secondary clearance surface 10, which runs at a second secondary clearance angle .sub.2.

[0115] The amounts of the secondary clearance angles .sub.2, .sub.2 are preferably greater than those of the primary clearance angles .sub.1, .sub.1, in order to further clear the secondary clearance surfaces.

[0116] The cutting element 3 has a width b.sub.LR along the first circumferential cutting edge LR and said width corresponds to the length of the first circumferential cutting edge LR.

[0117] The cutting element 3 has a width b.sub.RR along the second peripheral cutting edge RR, which corresponds to the length of the second peripheral cutting edge RR.

[0118] It is preferred that the first peripheral cutting edge LR and the second peripheral cutting edge RR are of unequal length.

[0119] In particular, the width b.sub.LR of the peripheral cutting edge LR is greater than the width b.sub.RR of the peripheral cutting edge RR.

[0120] The relationships are even clearer from FIGS. 4a and 4b, which show schematic cross sections through a cutting element 3. The sections are arranged in such a manner that a section plane runs normal to the longitudinal axis Z. The angular amounts are overdrawn.

[0121] Optionally, a circular grinding chamfer RSF is formed on the first peripheral cutting edge LR and/or on the second peripheral cutting edge RR. This is illustrated as an example in FIG. 4a.

[0122] Circular grinding chamfer means that the chamfer adjacent to the respective circumferential cutting edge runs at least in sections along the tool diameter d, in other words on the enveloping cylinder surface ZM of the tool, as indicated by a radius r.sub.ZM of the cylinder surface ZM. A circular grinding chamfer RSF is, as already explained, favorable for smooth running and a robust cutting wedge as well as for a possible coating. A width of the circular grinding chamfer RSF is in particular between 0.01 mm and 0.20 mm, further preferred between 0.05 mm and 0.15 mm.

[0123] In general, the amounts of the primary clearance angles .sub.1, .sub.1 are between 4 and 12, particularly preferably around 82, especially 81.

[0124] The amounts of the secondary clearance angles .sub.2, .sub.2 are chosen to be larger, typically between 10 and 30, preferably around 162, further preferred around 161.

[0125] Furthermore, the primary clearance surfaces 5, 6 and the secondary clearance surfaces 9, 10 each have a width and the width b.sub.1 of the primary clearance surface 6 and the width b.sub.2 of the secondary clearance surface 10 are illustrated in FIG. 4a.

[0126] FIG. 4b shows the widths b.sub.3 and b.sub.4 of the primary clearance surface 5 and the secondary clearance surface 9 respectively.

[0127] In general, the widths of the primary clearance surfaces 5, 6 are equal, and the widths of the secondary clearance surfaces 9, 10 are also equal.

[0128] The widths b.sub.1, b.sub.3 of the primary clearance surfaces are preferably relatively narrow. It is preferably provided that a width b.sub.1, b.sub.3 of the primary clearance surface is between 0.040 times and 0.110 times the tool diameter d. In other words, this development means that the width of a primary clearance surface b.sub.1, b.sub.3 is preferably between 4% and 11% of the tool diameter d.

[0129] It is quite particularly preferred that the width of the primary clearance surfaces b.sub.1, b.sub.3 is about 0.074 times the tool diameter d. This specification includes values 10%, in other words a range from 0.067 to 0.081.

[0130] The secondary clearance surfaces 9, 10 are preferably adjoined by third clearance surfaces which run at tertiary clearance angles .sub.3, .sub.3. The tertiary clearance angles .sub.3, .sub.3 are preferably significantly larger than the secondary clearance angles. Clearance angles of the tertiary clearance surfaces are in particular 20, further preferred 25. The tertiary clearance surfaces are thus located on the back side of the cutting element 3 and finally adjoin the chip flutes.

[0131] FIG. 5 shows a section of the cutting edge of a milling tool 100 according to the invention. The section planes A-A and B-B are shown and mark sections through cutting elements 3. The sections are each made in planes with the longitudinal direction Z as the normal vector, in other words as if the milling tool 100 were being sectioned normal to the longitudinal direction.

[0132] The section is oriented so that a sense of rotation in the direction of rotation R faces downwards in the illustration. A clamping section 1, in other words the shank, is indicated on the left in the illustration. The milling tool 100 is therefore illustrated rotating in a clockwise direction.

[0133] FIGS. 6a and 6b show sections A-A and B-B through cutting elements 3 according to FIG. 5.

[0134] FIG. 6a shows the section A-A. The primary clearance angle .sub.1, the secondary clearance angle .sub.2 and the tertiary clearance angle pare shown with the corresponding clearance surfaces, which adjoin the circumferential cutting edge LR, which runs along the chip flute LS with a left-facing spiral.

[0135] FIG. 6 b shows the section B-B. The primary, secondary and tertiary clearance angles .sub.1, .sub.2, .sub.3, are shown in the same manner, as are the clearance surfaces which adjoin the circumferential cutting edge RR which runs along the right-facing spiral flute RS.

[0136] FIG. 7 schematically shows a section of a development of the cutting edge area 2 of a milling tool 100 according to the invention, wherein the intended direction of rotation R is again indicated. The basic shape of the cutting elements 3, or more precisely their top surfaces, can be seen in the development. The contour of the cutting elements 3 is formed by the first and second circumferential cutting edges RR, LR andopposite each otherby the transition of the clearance surfaces on the back into the respective chip flute.

[0137] For the sake of clarity, only the primary clearance surfaces 5, 6 are shown on a cutting element 3. Also, not all reference signs are assigned to each cutting element 3.

[0138] The chip flute RS runs in a right-facing spiral at a spiral angle .

[0139] The chip flute LS runs in a left-facing spiral at a spiral angle .

[0140] In the exemplary embodiment shown, the spiral angle of the right-facing chip flute RS is preferably 30, the spiral angle of the left-facing flute LS is preferably 35.

[0141] A width b.sub.LS of the left-facing chip flute LS is smaller than a width b.sub.RS of the right-facing chip flute RS. In particular, the ratio of the widths of the chip flutes (b.sub.RS/b.sub.LS) is 1.2 to 3.0.

[0142] The respective widths of the chip flutes are considered to be the distances between the respective circumferential cutting edges and the opposite-lying transition of the clearance surface to the chip flute.

[0143] A first internal angle .sub.1 of a cutting element 3 facing in the longitudinal direction Z of the milling tool 100 is preferably smaller than a second internal angle .sub.2 of a cutting element 3 facing in the circumferential direction.

[0144] In particular, the first internal angle (pi is around 6515%, further preferred 6510%, still further preferred 655%.

[0145] Internal angles of the longitudinal corners of less than 65 tend to be unstable and sensitive.

[0146] In a complementary manner thereto, the second internal angles .sub.2 associated with corners facing in the circumferential direction are obtuse. It is apparent that the second internal angle, .sub.2, is spanned by the adjacent circumferential cutting edges LR and RR. In this manner, more cutting edge length is advantageously offered in the circumferential direction.

[0147] In one variant, the first circumferential cutting edge LR and the second circumferential cutting edge RR are of unequal length. In particular, the width b.sub.LR of the peripheral cutting edge LR is greater than the width b.sub.RR of the peripheral cutting edge RR.

[0148] In particular, a length ratio of (b.sub.LR/b.sub.RR) is between 1.0 and 2.0, preferably between 1.1 and 1.5, particularly preferably around 1.10.1. This can be advantageous for a moderate predominance of a pressing effect.