Milling tool

Abstract

A face milling tool includes a tool body having a central rotation axis around which the tool is rotatable, and at least one insert seat formed in a transition between a front end and an envelope surface of the tool. The tool further includes at least one cutting insert mounted in the insert seat, the cutting insert having an upper side defining an upper extension plane, a cutting edge extending around the circumference of the upper side, and a lower side defining a lower extension plane directed towards the bottom support surface of the insert seat. A center axis extends perpendicularly through the upper and the lower extension planes. The tool is configured such that a main cutting edge portion is at an entering angle κ smaller than 80° and such that the upper extension plane is at a radial tipping-in angle −60°≦γ.sub.f≦−25° and at an axial tipping-in angle −20°≦γ.sub.m≦0°, such that an angle of inclination λ of the main cutting edge portion is within the range 15°≦λ≦50°.

Claims

1. A face milling tool configured for chip-removing machining comprising: a tool body including a front end and a rear end, between which a central rotation axis extends around which the tool is rotatable in a direction of rotation, and at least one insert seat formed in a transition between the front end and an envelope surface extending between the front end and the rear end of the tool body, the at least one insert seat having a bottom support surface, wherein a chip pocket is provided in front of the at least one insert seat in the direction of rotation of the tool; and at least one cutting insert securely mounted in the at least one insert seat, the at least one cutting insert including an upper side defining an upper extension plane, a cutting edge extending around a circumference of the upper side, a lower side defining a lower extension plane parallel to the upper extension plane, the lower side having a support face directed towards the bottom support surface of the insert seat, wherein a center axis extends perpendicularly through the upper extension plane and the lower extension plane, wherein a main cutting edge portion is at an entering angle κ smaller than 80°, the upper extension plane is at a radial tipping-in angle γ.sub.f and at an axial tipping-in angle γ.sub.m, the main cutting edge portion is at an angle of inclination λ, the axial tipping-in angle γ.sub.m being within the range −20°≦γ.sub.m≦0°, the radial tipping-in angle γ.sub.f being within the range −60°≦γ.sub.f≦−25°, and the angle of inclination λ being within the range 15°≦λ≦50°, the upper side and the lower side of the cutting insert being connected by at least one side surface including a clearance surface, the main cutting edge portion being formed in the transition between the clearance surface and the upper side, wherein the clearance surface is formed at an obtuse inner angle with respect to the upper extension plane as seen in a side elevation view.

2. The milling tool according to claim 1, wherein the cutting insert has a circumference which is the same or essentially the same in the upper extension plane and in the lower extension plane.

3. The milling tool according to claim 2, wherein the cutting insert is double-sided with a cutting edge-extending also around the circumference of the lower side.

4. The milling tool according to claim 1, wherein the cutting insert is indexable with a plurality of index positions, each index position including a main cutting edge portion.

5. The milling tool according to claim 4, wherein the cutting insert on its upper side includes at least five main cutting edge portions.

6. The milling tool according to claim 1, wherein the angle of inclination λ is within the range 20°≦λ≦50°.

7. The milling tool according to claim 1, wherein the axial tipping-in angle γ.sub.m is within the range −20°≦γ.sub.m≦−2°.

8. The milling tool according to claim 1, wherein the radial tipping-in angle γ.sub.f is within the range −50°≦γ.sub.f≦−30°.

9. The milling tool according to claim 1, wherein the radial tipping-in angle γ.sub.f is within the range −50°≦γ.sub.f≦−35°.

10. The milling tool according to claim 1, wherein the entering angle κ is within the range 10°≦κ≦65°.

11. The milling tool according to claim 1, wherein the entering angle κ is within the range 20°≦κ≦50°.

12. The milling tool according to claim 1, wherein the bottom support surface of the insert seat extends in a plane parallel to the upper extension plane of the cutting insert.

13. The milling tool according to claim 1, wherein the upper side of the cutting insert includes an upper base surface extending in parallel with the upper extension plane, the upper base surface being recessed with respect to the main cutting edge portion.

14. The milling tool according to claim 4, wherein the cutting insert on its upper side includes at least seven main cutting edge portions.

15. The milling tool according to claim 1, wherein the axial tipping-in angle γ.sub.n, is within the range −18°≦γ.sub.m≦−4°.

16. The milling tool according to claim 4, wherein the cutting insert on its upper side includes at least seven main cutting edge portions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a milling tool according to the disclosure.

(2) FIG. 2 is an end view of the milling tool in FIG. 1.

(3) FIG. 3 is a side view of the milling tool in FIG. 1.

(4) FIG. 4 is an exploded perspective view of the milling tool in FIG. 1.

(5) FIG. 5 shows the axial tipping-in angle in a partial side view of the milling tool in FIG. 1.

(6) FIG. 6 shows the radial tipping-in angle in a partial planar view of the milling tool in FIG. 1.

(7) FIG. 7 shows the entering angle in a partial side view of the milling tool in FIG. 1.

(8) FIG. 8 shows the angle of inclination in a partial perspective view of the milling tool in FIG. 1.

(9) FIG. 9 is a perspective view of a cutting insert for use in a milling tool according to the disclosure.

(10) FIG. 10 is a side view of the cutting insert in FIG. 8.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(11) A face milling tool 101 according to an embodiment of the disclosure is shown in FIGS. 1-4. The milling tool 101 includes a tool body 102 and six cutting inserts 1. The tool body 102 includes a front end 104 and a rear end 105, between which a central rotation axis C1 extends. The tool is rotatable in a direction of rotation R around the central rotation axis C1 and an envelope surface 106 is concentric with the axis C1.

(12) Six insert seats 107 are formed in a transition between the front end 104 and the envelope surface 106. Each insert seat 107 includes a bottom support surface 108, a side support 109 comprising two side support surfaces, and a chip pocket 110 provided in front of the insert seat in the direction of rotation R of the tool 101. The cutting inserts 1 are securely and detachably mounted in the insert seats 107 by means of a screw 111.

(13) A cutting insert 1 suitable for use in the milling tool according to the disclosure is shown in further detail in FIGS. 9-10. The cutting insert 1 is indexable and double-sided and has an upper side 2 defining an upper extension plane P.sub.U and a lower side 3 defining a lower extension plane P.sub.L parallel to the upper extension plane P.sub.U. An upper cutting edge 7 extends around the circumference of the upper side 2 and a lower cutting edge 17 extends around the lower side 3. The upper side 2 includes a recessed upper base surface 11. An inclined chip surface 12 extends between the recessed base surface 11 and the cutting edge 7. Since the cutting insert is double-sided, the lower side 3 also has a recessed base surface, which functions as a support face directed towards and resting against the bottom support surface 108 of the insert seat 107. A center axis C2 extends perpendicularly through the upper extension plane P.sub.U and the lower extension plane P.sub.L.

(14) The upper side 2 and the lower side 3 of the cutting insert 1 are connected by a side surface 4, which includes several main clearance surfaces 5, 15 and secondary clearance surfaces 6a, 6b, 16a, 16b. The cutting edge 7 has seven essentially rectilinear chip removing main cutting edge portions 8 and, for each main cutting edge portion 8, a first and a second secondary cutting edge portion 9, 10, formed as surface-wiping edges configured for different entering angles κ. Each main cutting edge portion 8 is formed in a transition between the upper side 2 and one of the upper main clearance surfaces 5.

(15) The first secondary cutting edge portion 9 is formed in a transition between the upper side 2 and a first upper secondary clearance surface 6a in a region between two main cutting edge portions 8, that is, in a corner region of the cutting insert 1. The second secondary cutting edge portion 10 is formed in a transition between the upper side 2 and a second upper secondary clearance surface 6b. The cutting insert 1 in this embodiment also comprises, in its side surface 4, several recessed support surfaces 14 forming a “waist” around the cutting insert, serving to stabilise the cutting insert 1 in the insert seat 107 by elongating the contact area of the support surface 14 and the side support 109 of the cutting insert. Thereby, rotation of the cutting insert 1 around its center axis C2 is prevented.

(16) As can be seen in FIGS. 9-10, the main clearance surface 5 is formed at an obtuse inner angle with respect to the upper extension plane P.sub.U as seen in side elevation view. In this embodiment, the inner angle is 107°. The secondary clearance surfaces 6a, 6b are formed at less obtuse inner angles with respect to the upper extension plane P.sub.U as seen in side elevation view.

(17) The tool shown in FIGS. 1-4 is configured such that a main cutting edge portion 8 is at an entering angle κ of approximately 42°. The entering angle varies along the edge, even though the edge is straight. The entering angle κ is the angle that the main cutting edge portion 8 makes with the direction of feed of the milling tool as seen in side elevation view, see FIG. 7. The entering angle κ is more specifically defined as the angle between a plane P.sub.tan and a plane P.sub.f measured in a reference plane P.sub.ref2, which planes P.sub.tan, P.sub.f and P.sub.ref2 will be defined below. At this entering angle, the second secondary cutting edge portion 10 acts as a surface-wiping secondary edge, while the first secondary cutting edge portion 9 acts as a corner edge.

(18) The cutting insert 3 is tipped in so that the upper extension plane P.sub.U is at a negative radial tipping-in angle γ.sub.f of −35°. The radial tipping-in angle γ.sub.f, shown in FIG. 6, is the angle between the upper extension plane P.sub.U and a line along a radial vector r of the tool as seen in planar view. More specifically, the radial tipping-in angle γ.sub.f is obtained by taking a plane P.sub.f normal to the central rotation axis C1 and passing through a point p.sub.k, and in the plane P.sub.f measure the angle between a reference plane P.sub.ref and the upper extension plane P.sub.U as shown in FIG. 6, which is a view in the plane P.sub.f. The reference plane P.sub.ref is a plane spanned by the central rotation axis C1 and a radial vector r perpendicular to the central rotation axis C1 and passing through the point p.sub.k. The radius of the tool is measured between the central rotation axis C1 and the point p.sub.k, which for this cutting insert is located in the transition between the main cutting edge portion 8 and the surface wiping edge 10 of the cutting insert 1. With a negative radial tipping-in angle γ.sub.f, the upper extension plane P.sub.U is directed outwards with regard to the central rotation axis C1 of the tool.

(19) The cutting insert 3 is further tipped in so that the upper extension plane P.sub.U is at a negative axial tipping-in angle γ.sub.m of −10°. The axial tipping-in angle γ.sub.m, shown in FIG. 5, is the angle between the upper extension plane P.sub.U and the central rotation axis C1 of the tool. More specifically, the axial tipping-in angle γ.sub.m is obtained by measuring the angle between the upper extension plane P.sub.U and the reference plane P.sub.ref in a plane P.sub.m (not shown), which plane P.sub.m is perpendicular to the upper extension plane P.sub.U, parallel to the central rotation axis C1 and passes through the point p.sub.k. With a negative axial tipping-in angle γ.sub.m, the upper extension plane P.sub.U is inclined towards the front end 104 of the milling tool. With an entering angle κ of approximately 42°, a radial tipping-in angle γ.sub.f of −35° and an axial tipping-in angle γ.sub.m of −10°, the main cutting edge portion 8 is at an angle of inclination λ of approximately 20°. The angle of inclination λ, shown in FIG. 8, is the angle that the main cutting edge portion 8 in a point p.sub.a, or a tangent t to the main cutting edge portion 8 in that point, makes with a second reference plane P.sub.ref2. The second reference plane P.sub.ref2 is parallel with and includes the central rotation axis C1 and includes the point p.sub.a on the main cutting edge portion 8. The angle of inclination λ is measured in a tangential plane P.sub.tan. The tangential plane P.sub.tan is tangential to the main cutting edge portion 8 in the point p.sub.a and is perpendicular to the second reference plane P.sub.ref2. In FIG. 8, the angle of inclination λ is shown by looking at the main cutting edge portion 8 from below the front end 104 of the tool 101, along a line which is normal to the tangential plane P.sub.tan.

(20) For the cutting insert 1 according to the first embodiment, the angle of inclination λ is approximately constant along the main cutting edge portion 8, since the main cutting edge portion 8 is essentially rectilinear. For a curved main cutting edge portion, the angle of inclination will vary along the edge. The tangential plane P.sub.tan should in that case be taken as a tangential plane to the main cutting edge portion in the point on the main cutting edge where the angle of inclination λ needs to be determined.

(21) As can be seen in FIGS. 9-10, the main clearance surface 5 is formed at an obtuse inner angle with respect to the upper extension plane P.sub.U as seen in side elevation view. In this embodiment, the inner angle is 107°. The secondary clearance surfaces 6a, 6b are formed at less obtuse inner angles with respect to the upper extension plane P.sub.U as seen in side elevation view. In the shown embodiment, the clearance behind the main cutting edge portion 8 in the direction of rotation R of the tool is optimised with regards to the obtuse inner angle between the upper extension plane P.sub.U and the upper main clearance surface 5, so that the cutting insert 1 has high strength, while still providing sufficient clearance. The clearance behind the surface-wiping secondary cutting edge 10 is sufficient thanks to the negative axial tipping-in angle γ.sub.m. With the chosen values for the inner angles between the upper extension plane P.sub.U and the clearance surfaces 5, 6a, 6b, the clearance behind the main cutting edge portion 8 and the secondary cutting edge portions 9, 10 is in the shown embodiment in a suitable range. The recessed upper base surface 11 ensures that a positive rake angle is achieved despite the large negative radial tipping-in angle γ.sub.f, thus ensuring good chip evacuation properties.

(22) In a second embodiment of the milling tool (not shown), the same cutting insert 1 as described above is used, but the tool is configured for an entering angle κ of 25°, in which case the first secondary cutting edge portion 9 acts as a surface-wiping secondary edge. The second secondary cutting edge portion 10 is for moderate cutting depths not active as a cutting edge. However, the second secondary cutting edge portion 10 adjacent the active main cutting edge portion 8 may be used as a prolongation of the main cutting edge portion 8 if the cutting depth is large. For an entering angle κ of 25°, the axial tipping-in angle γ.sub.m is in this embodiment set to −17° and the radial tipping-in angle γ.sub.f to −45°, in which case the angle of inclination λ of the main cutting edge portion 8 is approximately 33°. The inner angle between the upper extension plane P.sub.U and the secondary clearance surface 6a, located behind the surface-wiping secondary edge 9, is slightly obtuse in order to achieve a suitable clearance behind the surface-wiping secondary edge 9 with the relatively large negative axial tipping-in angle γ.sub.m. The tool with an entering angle of 25° is suitable for milling with high feed rates and relatively small cutting depths.

(23) The radial and the axial tipping-in angles of the tool according to the disclosure should be adjusted so that the angle of inclination λ is within the range 15°≦λ≦50°, preferably within the range 20°≦λ≦50°.

(24) The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims. For instance, the cutting insert used may be a cutting insert of a different shape, such as square, rhombic, or round, or polygonal with a different number of main cutting edge portions than described above. In particular, the cutting insert does not need to be configured as a combination cutting insert usable for more than one entering angle. It is also possible to configure the tool for other entering angles than those exemplified above. Moreover, the cutting insert used may be one which gives rise to a clearance which varies along the main cutting edge portion. The cutting insert may also, instead of being screw mounted, be secured by for example clamps. The tool may of course be designed for either left hand rotation or right hand rotation.

(25) Although the present embodiment(s) has been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims.