Milling tool and cutting insert

Abstract

Milling tool with a disc- or strip-shaped base body (10) that can be driven about a rotary axis (R), and several tangential cutting inserts (12; 112) arranged along the outer circumference of the base body (10) on opposite sides, wherein the tangential cutting inserts (12; 112) overlap each other when viewed in the axial direction, wherein the tangential cutting inserts (12; 112) have two side surfaces (50) through which a mounting opening (20) extends, and two end faces (52; 152), wherein cutting edges (S) are formed at the transition of the end faces to the side surfaces, wherein a width of the tangential cutting insert (12; 112) extends between the cutting edges (S), characterized in that the mounting opening (20) is eccentrically arranged along the width of the tangential cutting insert (12; 112) to form a The middle plane (M) of the cutting insert (12; 112) is arranged.

Description

[0001] The invention relates to a milling tool with a disc- or strip-shaped base body that can be driven about a rotational axis, and a plurality of tangential cutting inserts arranged along the outer circumference of the base body on opposite sides. The invention further relates to a tangential cutting insert, in particular for such a milling tool, with two side surfaces through which a fastening opening extends, and two end faces, wherein cutting edges are formed at the transition between the end faces and the side faces.

[0002] The milling tool can in particular be a turning broaching tool or a turning-turning broaching tool, such as those used as crankshaft milling cutters or camshaft milling cutters, i.e. a milling tool with which surfaces on crankshafts or camshafts for internal combustion engines can be machined.

[0003] A milling tool of the type mentioned above is known from DE 102 38 451 A1. It is briefly described below with reference to Fig. 1 and Fig. 2 explained.

[0004] The milling tool has a base body 5, which is mounted in a machine tool so as to be rotatable about a rotational axis R. Several holders 7 are attached to the carrier 5, which together form a disc-shaped structure. Several base bodies 10 are attached along the outer circumference of the holders 7, which together form the outer circumference of the milling tool.

[0005] At the Fig. In the embodiment shown in Figure 1, each base body is strip-shaped, thus extending over a certain portion of the circumference of the milling tool and having a thickness measured in the radial direction that represents a fraction of the diameter of the milling tool. Alternatively, it is also possible to omit the carrier and holders, thus using a larger, disc-shaped base body.

[0006] On the base body 10 (see Fig. 2) several cutting inserts 12 are attached here. These are tangential cutting inserts that are mounted using a fastening screw 14.

[0007] In the Fig. In the embodiment shown in Figure 2, each cutting insert 12 is mounted in a carrier or cassette 16, which in turn is attached to the base body 10 by means of screws 18. It would also be possible, in principle, to attach each cutting insert 12 directly to the base body 10.

[0008] As in Fig. As can be seen in Figure 2, the cutting inserts 12 are arranged along the outer circumference of the base body 10, alternating on opposite sides. This is because this is the only way to attach the cartridges 16 to the base body.

[0009] In Fig. Figure 3 shows schematically how the axial components of the cutting forces acting on the cutting inserts 12 during milling are arranged on the base body 10. Due to the alternating arrangement of the cutting inserts 12, the axial forces F a alternately in opposite directions. The arrangement of the axial forces F a potentially leads to bending loads on the base body 10.

[0010] The opposing forces naturally act on the workpiece during milling. Thus, 12 different axial forces act on the workpiece with each pass of a cutting insert.

[0011] Both the bending loads on the base body 10 and the changing axial forces acting on the workpiece potentially lead to tolerances during milling.

[0012] Furthermore, milling cutters with cutting inserts are known from WO 2013 / 144 030 A1, DE 10 2005 050 210 A1, US2011 / 0164932A1, DE10333621A1 and DE 10 2008 039 135 A1.

[0013] Furthermore, US 5 004 378 A shows a cutting tool with a cutting insert.

[0014] The object of the invention is to create a milling tool and a cutting insert with which tighter tolerances can be maintained during milling.

[0015] The object is achieved by a milling tool according to claim 1 and by a tangential cutting insert according to claim 8.

[0016] To achieve this object, in a milling tool of the type mentioned at the outset, the cutting inserts are provided to overlap one another when viewed in the axial direction. To achieve this object, in a cutting insert of the type mentioned at the outset, the fastening opening is further provided to be arranged eccentrically. The invention is based on the fundamental idea of ​​arranging the cutting inserts so that they act as simultaneously as possible and thus in pairs. In this way, the axially aligned components of the cutting forces balance one another out, so that (assuming that the cutting inserts are exactly opposite one another) no bending forces act on the base body or (assuming a slight offset in the circumferential direction) the effective lever arm between the components of the cutting forces acting in the axial direction is significantly lower than in the prior art.The paired positioning of the cutting inserts is made possible by the eccentric arrangement of their fastening holes. This means that, in a pair of opposing cutting inserts, the fastening screw screwed in from one side is at the "front" (relative to the direction of rotation), while the fastening screw screwed in from the other side is at the "back." This ensures that there is sufficient material in the base body between the two fastening screws to accommodate the fastening screws. The eccentric arrangement of the fastening hole on the cutting insert is in direct contrast to the previous approach, according to which the fastening hole was centrally located to allow for indexing of the cutting insert.

[0017] The cutting edges are tangential cutting inserts. Such cutting inserts are well-known and well-suited for use in crankshaft milling cutters.

[0018] According to a preferred embodiment of the invention, the overlap is at least 50% of the circumferential width of a cutting insert. While even an overlap generally leads to a reduction in the tolerances that occur during machining with the milling tool according to the invention, the degree of overlap increases the machining accuracy and reduces the alternating load on the workpiece and the bending load on the base body.

[0019] It is particularly preferred that the overlap be at least 80% of the circumferential width of a cutting insert. This further reduces the tolerances that occur.

[0020] Even more preferred is when the overlap is at least 90% of the circumferential width of a cutting insert. The resulting bending loads on the base body due to the offset axial components of the cutting forces are negligible, since the effective lever arm is negligible compared to the stiffness of the base body.

[0021] According to one embodiment of the invention, the cutting inserts on the side surfaces of the base body are of different types. This allows the cutting behavior of the milling tool to be optimally adjusted to the respective requirements. For example, the cutting inserts on the side surfaces of the base body can be roughing cutting inserts and finishing cutting inserts.

[0022] According to a preferred embodiment, cutting inserts of a third type are arranged on the peripheral surface of the base body. These can be used to machine additional surfaces in the same operation, for example, the cylindrical surface of a crankpin.

[0023] Preferably, the mounting opening does not intersect a center plane of the cutting insert, or does so by no more than 20% of the diameter of the mounting opening. This ensures that the distance, measured in the circumferential direction, between the two mounting screws of a pair of laterally arranged cutting inserts is sufficiently large.

[0024] In particular, the center plane of the cutting insert extends parallel to the end faces.

[0025] The end faces of the cutting inserts, which are arranged on the side surfaces of the base body, can be designed in a way that is optimal for the surfaces to be milled. For example, the end faces can be shaped like a parallelogram or rectangular with an attached bead.

[0026] The invention is described below with reference to two embodiments illustrated in the accompanying drawings, in which: - Fig. 1 schematically shows a milling tool from the prior art; - Fig. 2 one at the milling tool of Fig. 1 used base body with cutting inserts attached to it; - Fig. 3 schematically shows the axial forces acting on the base body 10 during milling; - Fig. 4 schematically shows a base body according to the invention; - Fig. 5 shows a plan view of a base body according to a first embodiment of the invention; - Fig. 6 the basic body of Fig. 5 in a perspective view; - Fig. 7 the basic body of Fig. 5 in a side view; - Fig. 8 shows a cutting insert used in the first embodiment in a perspective view; - Fig. 9 the cutting insert of Fig. 8 in a side view, - Fig. 10 is a plan view of a base body according to a second embodiment; - Fig. 11 is a plan view of a cutting insert according to a first variant; and - Fig. 12 a plan view of a cutting insert according to a second variant.

[0027] In Fig. Figure 4 schematically shows a base body 10 for a milling tool according to the invention. The essential difference from the prior art milling tool is that the cutting inserts 12, which are arranged on opposite sides of the base body 10, overlap one another, viewed in the axial direction along the rotation axis R. In other words: the cutting inserts 12 are arranged in pairs such that the offset, measured in the circumferential direction, between the two cutting edges of the cutting inserts 12 of a pair is smaller than the length of the cutting inserts, measured in the circumferential direction.

[0028] In the Fig. In the basic principle of the base body 10 according to the invention shown in Figure 4, the cutting edges S located at the front in the direction of rotation D are on the same line, indicated here by L.

[0029] The consequence of the paired arrangement of the cutting inserts 12 on opposite sides of the base body 10 is that the axial components F a the cutting forces are not offset from each other, as is the case in Fig. 3, but are opposite each other. Thus, there is no lever arm between the acting axial components of the cutting forces, and no bending loads occur on the base body 10.

[0030] Although the Fig. 4, the cutting inserts 12 completely overlap one another, it is fundamentally possible to arrange the cutting inserts 12 slightly offset from one another. It is obvious that the greater the overlap, the lower the bending forces acting on the base body 10. Therefore, it is preferred that the overlap be at least 50% of the width of a cutting insert measured in the circumferential direction. Particularly preferably, the overlap is at least 80%, and it is particularly advantageous if the overlap is at least 90% of the width of a cutting insert measured in the circumferential direction.

[0031] The cutting inserts 12 can be arranged in pairs overlapping each other, as they are provided with an eccentrically arranged fastening opening 20. This results in the fastening screws 14 also being arranged eccentrically and thus offset from each other. Fig. 4 shows that the cutting inserts that are mounted on the Fig. 4 upper side surface of the base body 10, are each attached to the base body with a fastening screw 14A, which, viewed in the circumferential direction or direction of rotation D, are located "in front" of the fastening screws 14B, with which the cutting inserts 12 are attached to the base body 10, which are on the in Fig. 4 lower side surface of the base body 10.

[0032] Based on the Fig. 5 to 9, a first embodiment of the invention will now be described.

[0033] In the base body 10 according to the first embodiment, the cutting inserts 12 are mounted in pairs so that they completely overlap each other (see the Fig. 5 drawn line L).

[0034] As in the Fig. 6 and Fig. As can be seen in Figure 7, some cutting inserts 12 are assigned an adjusting device 30 with which these cutting inserts can be aligned.

[0035] In principle, it is also possible to mount the cutting inserts 12 in separate cassettes, which are then attached to the base body 10 with eccentrically arranged fastening screws.

[0036] In the Fig. 5 to 7 it can also be seen that further cutting inserts 40 are alternately mounted on the peripheral surface of the base body 10.

[0037] The cutting inserts 12 arranged on the side surfaces are tangential cutting inserts, each with two side surfaces 50 through which the mounting opening 20 extends. Furthermore, each cutting insert 12 has two end faces 52, which, in the embodiment shown here, have the broadest possible shape of a parallelogram. The cutting edges S are formed at the transition between the end faces 52 and the side surfaces 50.

[0038] As particularly in Fig. As can be seen in Figure 9, the fastening opening 20 is arranged eccentrically. In the embodiment shown, it is arranged such that it is just tangent to a center plane M of the cutting insert.

[0039] Depending on the respective design constraints, it may also be provided that the fastening opening 20 slightly intersects the center plane M. "Slightly" is defined here as an overlap that does not exceed 20% of the diameter of the fastening opening 20.

[0040] In Fig. 10 shows a base body for a milling tool according to a second embodiment. The same reference numerals are used for the components known from the first embodiment, and reference is made to the above explanations in this regard.

[0041] The essential difference between the first and the second embodiment is that in the second embodiment two types of cutting inserts 12 are used on the side surfaces of the base body 10, namely the cutting inserts with a parallelogram-like end face 52 known from the first embodiment (see also Fig. 11) and cutting inserts 112, whose end faces 152 (see Fig. 12) have a generally rectangular shape with an attached bulge at diagonally opposite corners.

[0042] The cutting inserts 112 can be roughing cutting inserts and the cutting inserts 12 can be finishing cutting inserts.

[0043] As in Fig. As can be seen in Figure 10, the roughing cutting inserts 112 are offset from each other in the circumferential or rotational direction D (see offset o). However, they overlap in the axial direction.

Claims

[1] Milling tool with a disc-shaped or strip-shaped base body (10) which can be driven about a rotational axis (R), and a plurality of tangential cutting inserts (12; 112) which are arranged along the outer circumference of the base body (10) on opposite sides, wherein the tangential cutting inserts (12; 112) overlap one another when viewed in the axial direction, wherein the tangential cutting inserts (12; 112) have two side surfaces (50) through which a fastening opening (20) extends, and two end faces (52; 152), wherein cutting edges (S) are formed at the transition of the end faces to the side surfaces, wherein a width of the tangential cutting insert (12; 112) extends between the cutting edges (S), characterized by that the fastening opening (20) is arranged eccentrically along the width of the tangential cutting insert (12; 112) to a center plane (M) of the cutting insert (12; 112). [2] Milling tool according to claim 1, characterized by that the overlap is at least 50% of the width of a cutting insert (12; 112) measured in the circumferential direction. [3] Milling tool according to claim 2, characterized by that the overlap is at least 80% of the width of a cutting insert (12; 112) measured in the circumferential direction. [4] Milling tool according to claim 3, characterized by that the overlap is at least 90% of the width of a cutting insert (12; 112) measured in the circumferential direction. [5] Milling tool according to one of the preceding claims, characterized by that the cutting inserts (12; 112) on the side surfaces of the base body are of different types. [6] Milling tool according to claim 5, characterized by that the cutting inserts on the side surfaces of the base body are roughing cutting inserts (112) and finishing cutting inserts (12). [7] Milling tool according to one of the preceding claims, characterized bythat cutting inserts (40) of a third type are arranged on the peripheral surface of the base body. [8] Tangential cutting insert (12; 112) with two side surfaces (50) through which a fastening opening (20) extends, and two end faces (52; 152), wherein cutting edges (S) are formed at the transition of the end faces to the side surfaces, wherein a width of the tangential cutting insert (12; 112) extends between the cutting edges (S), characterized by that the fastening opening (20) is arranged eccentrically along the width of the tangential cutting insert (12; 112) to a center plane (M) of the cutting insert (12; 112). [9] Cutting insert according to claim 8, characterized by that the fastening opening (20) does not intersect a center plane (M) of the cutting insert (12; 112) or does not intersect by more than 20% of a diameter of the fastening opening (20). [10] Cutting insert according to claim 8 or 9, characterized bythat the end faces (52) have the shape of a parallelogram. [11] Cutting insert according to claim 8 or 9, characterized by that the end faces (152) have a rectangular shape with an attached bead. [12] Cutting insert according to one of claims 8 to 11, characterized by that the center plane (M) of the cutting insert (12; 112) extends parallel to the end faces (52; 152).

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