Milling insert and three-edge milling cutter

Abstract

The invention relates to a milling insert and a three-edge milling cutter. A milling insert for a three-edge milling cutter includes an upper side defining an upper extension plane, a lower side defining a lower extension plane, a central axis extending perpendicularly through the upper and lower extension planes, a side surface extending between the upper and lower sides about an outer periphery of the milling insert, the present invention relates to a cutting tool comprising an upper side having a side surface comprising a main radial clearance surface, two opposing axial clearance surfaces and two corner clearance surfaces, at least one cutting edge formed in a transition between the upper side and the side surface, each cutting edge comprising a main cutting edge extending above the main radial clearance surface and two corner cutting edges extending below the main radial clearance surface, two corner cutting edges extend over the corner clearance surface on opposite sides of the main cutting edge, where the main cutting edge is inclined downwardly toward a midpoint of the main cutting edge as seen in a side view, and the main cutting edge and the main radial clearance surface are inclined outwardly from the corner cutting edge toward the midpoint as seen in a top view.

Description

[0001] This application is a divisional application of Chinese application No. 201880037103.1, filed on June 11, 2018, entitled "Milling Inserts and Three-Sided End Mills". Technical Field

[0002] This invention relates to a milling insert for a side and face milling tool according to the preamble of claim 1. The invention also relates to a side and face milling tool according to claim 15. Background Technology

[0003] (Multi-purpose) Three-sided milling cutters can be used for a variety of different applications, including grooving, parting, shoulder milling, face milling, and gang milling. A three-sided milling cutter consists of a milling disc equipped with milling inserts that provide cutting edges along the outer perimeter of the disc and on one or both sides. Milling discs with cutting edges along the outer perimeter and both sides are commonly used for grooving (or parting) and gang milling applications. This allows grooves with two planes (parallel side surfaces and a bottom surface) to be machined into a workpiece. The bottom surface of the groove is machined by the main cutting edge of the milling inserts extending along the outer perimeter of the disc, while the side surfaces are machined by auxiliary finishing cutting edges perpendicular to the main cutting edge and extending along the side of the disc. The corner between the bottom and side surfaces of the groove is machined by a corner cutting edge extending between the main and auxiliary finishing cutting edges on the milling inserts. Therefore, multiple milling discs can be mounted on a spindle (shaft) for simultaneously gang milling multiple grooves. A single milling disc can also be set at the free (front) end of the spindle (shaft) for milling a single groove. For shoulder milling and face milling (front or back milling) applications, this three-sided milling cutter may only require milling inserts with an auxiliary finishing cutting edge along one side of the milling disc.

[0004] US5454671 discloses a milling insert for a three-sided end mill. The milling insert has a basic rectangular shape, with its upper and lower sides connected by side surfaces. A cutting edge is formed in the transition between the upper and side surfaces, wherein a straight primary cutting edge extends above a primary radial clearance surface. Corner cutting edges and auxiliary cutting edges extend on each side of the primary cutting edge. The milling insert is symmetrical about the midplane, and therefore can be used on either side of the milling disc.

[0005] The performance of the milling inserts disclosed in US5454671 can be improved in terms of tool life, particularly in milling of stainless steel, titanium and heat-resistant superalloy materials. Summary of the Invention

[0006] The primary objective of this invention is to provide a milling insert for a three-sided end mill, particularly suitable for milling stainless steel, titanium, and heat-resistant superalloy materials, exhibiting improved tool life and toughness compared to prior art inserts in such workpiece materials. Specifically, the objective is to achieve such a milling insert that ensures high-quality machined surfaces while simultaneously achieving improved tool life and toughness. Another objective is to enable the cost-effective manufacture of such a milling insert.

[0007] At least the primary objective is achieved by a milling cutter having the features defined in the characterizing portion of claim 1. According to another aspect of the invention, at least the primary objective is achieved by a three-sided milling cutter having the features defined in claim 15.

[0008] The milling inserts according to the present invention include: - Upper side, which includes the front blade surface and defines an upper extending plane. - The lower side, opposite to the upper side, defines a lower extending plane, wherein the central axis extends vertically through the upper extending plane and the lower extending plane. - A side surface extending between an upper and lower side around the outer periphery of the milling insert, wherein the side surface includes a primary radial clearance surface, two opposing auxiliary axial clearance surfaces, and two corner clearance surfaces extending between the primary radial clearance surface and the auxiliary axial clearance surfaces. - At least one cutting edge, the at least one cutting edge being formed in a transition between an upper side and a side surface, wherein each cutting edge includes a main cutting edge and two corner cutting edges, the main cutting edge being formed in a transition between a rake surface and a main radial clearance surface, and the two corner cutting edges being formed in a transition between a rake surface and a corner clearance surface.

[0009] The milling insert is characterized in that, as seen in the side view of the milling insert, the main cutting edge slopes downward from the corner cutting edge toward the midpoint of the main cutting edge, and as seen in the top view of the milling insert, the main cutting edge and the main radial clearance surface slope outward from the corner cutting edge toward the midpoint of the main cutting edge.

[0010] The three-sided milling cutter according to the invention includes a milling disc and at least one milling insert, wherein each of the at least one milling insert is removably mounted in an insert holder of the milling disc. Preferably, at least one milling insert is mounted in an insert holder located on the right-hand side of the milling disc, and at least one milling insert is mounted in an insert holder located on the left-hand side of the milling disc.

[0011] As seen in the side view, the main cutting edge has an overall concave shape with a midpoint that is recessed compared to the endpoints of the main cutting edge near the adjacent corners. The downward slope of the main cutting edge helps reduce cutting forces during machining, particularly in stainless steel, titanium, and heat-resistant superalloy materials, thus contributing to increased tool life. Furthermore, this milling insert exhibits improved toughness compared to inserts with a straight (linear) and non-sloping main cutting edge, at least in part because the sloped main cutting edge gradually penetrates the workpiece during machining. Simultaneously, a flat (bottom) surface (in the groove) can be provided by means of the outward slope of the main cutting edge (as seen in the top view), i.e., the midpoint of the main cutting edge lies outside the straight line drawn between the two endpoints of the main cutting edge relative to the central axis. Preferably, the main cutting edge is thus convex and continuously curved with at least one radius of curvature. The shape of the cutting edge, as seen in the top view, compensates for the concave shape seen in the side view, which would otherwise provide a convex (bottom) surface in the workpiece.

[0012] As seen in the top view, the outward tilt of the primary cutting edge (and in some embodiments, a convex shape) also serves to reduce the impact of potential angular errors that may occur when installing the milling insert due to manufacturing tolerances. Such angular errors could otherwise cause steps in the sidewall surface of the workpiece when the milling insert is used for face milling. The shape of the primary cutting edge thus allows for a smoother sidewall surface during shoulder milling and prevents steps from forming on the workpiece wall surface. During slot milling, this also prevents steps from forming in the bottom surface of the groove.

[0013] Furthermore, since the main radial clearance surface also has an outward inclination, and is preferably convex and continuously curved with at least one radius of curvature, the number of grinding operations required in the production of milling inserts can be reduced, and the main radial clearance surface, including the main cutting edge, can be ground on the periphery in a single grinding operation. Therefore, milling inserts can be produced cost-effectively through improved control of their shape and manufacturing tolerances. This grinding of milling inserts also enables the machining of high-quality surfaces and geometric tolerances in the workpiece.

[0014] The primary radial clearance surface can preferably be formed as a surface that extends continuously between the primary cutting edge and the lower side. This allows for improvement in the shape and tolerance of the entire surface below the primary cutting edge through a cost-effective single grinding operation. This is particularly advantageous for improving the accuracy / tolerance of indexable milling inserts, where a portion (the lower part) of the primary radial clearance surface also forms a radial support surface for the indexable milling insert. Alternatively, however, the milling insert can comprise two or more radial clearance surface portions formed at different clearance angles, i.e., an upper primary radial clearance surface portion and a lower radial clearance surface portion. This allows for a single grinding operation on the upper primary radial clearance surface portion, while the lower primary radial clearance surface portion can be left unground or subjected to different grinding operations. For example, sufficient accuracy of the milling insert can be achieved by using the lower portion as a reference to grind only the upper primary radial clearance surface portion during a grinding operation. It is also preferable to use different grinding operations on the lower portion of the indexable milling insert, which is intended for radial support when the milling insert is mounted in the milling disc body.

[0015] The milling insert can also have an upper portion with a main radial clearance surface that extends partially between the main cutting edge and the lower side, wherein the upper portion protrudes relative to the lower portion of the main radial clearance surface. This simplifies the grinding of the upper portion, in which case the lower portion may not need to be ground or may be ground into a different shape.

[0016] According to one embodiment, the shape of the main cutting edge, as seen in the top view, and at least the upper portion of the main radial clearance surface, as seen in an arbitrary section perpendicular to the central axis, are the same or substantially the same. Therefore, the main radial clearance surface and the main cutting edge can be ground in a single grinding operation. "Substantially the same" is intended herein to mean as similar as possible, taking into account manufacturing tolerances. "Arbitrary section" refers to a section taken along the central axis at an arbitrarily selected point on the upper portion of the main radial clearance surface.

[0017] Preferably, the shape of the primary radial clearance surface, as seen in any cross-section perpendicular to the central axis, is independent of the position of that cross-section along the central axis. In this way, a grinding wheel can be used to generate the primary radial clearance surface in a single pass. Furthermore, by using the ground primary radial clearance surface (below the non-active primary cutting edge on the indexable milling insert) as a radial support surface, improved control / precision of the contact point between the milling disc body and the milling insert is achieved due to this ground surface. Therefore, the support of the milling insert in the milling cutter becomes more stable and precise.

[0018] According to one embodiment, as seen in a top view of the milling insert, the main cutting edge is convex. In this embodiment, the main cutting edge is continuously curved and has no sharp corners.

[0019] According to one embodiment, the at least one cutting edge further includes two opposing auxiliary cutting edges adjacent to the corner cutting edge, wherein each auxiliary cutting edge is formed in a transition portion between the rake surface and the auxiliary axial clearance surface portion. The auxiliary cutting edges are configured to machine parallel side surfaces in a groove created by a three-sided end mill comprising at least two milling inserts located on opposite sides of the milling disc. During face milling or shoulder milling, one of the auxiliary cutting edges is used to create a surface on the workpiece. The auxiliary cutting edge may be linear, or preferably curved with a large radius of curvature, making it appear slightly convex in a top view, for surface finishing operations on the workpiece surface.

[0020] According to one embodiment, each auxiliary cutting edge is inclined downward from the adjacent corner cutting edge. Preferably, each auxiliary cutting edge is inclined downward at an interior angle γ of 5° to 25° relative to the upper extending plane. During milling at an angle of 90° between the surface produced by the main cutting edge and the surface produced by the auxiliary cutting edge, the downward inclination of the auxiliary cutting edges helps to create sufficient clearance between the axial side surface of the (indexable) milling insert and the machined workpiece surface.

[0021] According to one embodiment, at least one recess is formed in the primary radial clearance surface. This recess is preferably defined by a boundary edge having two opposing side edges connected by an upper edge. The size of the recess is set such that when a milling insert is mounted in the milling disc body, two-point radial support can be achieved on the primary radial clearance surface at the opposing side edges of the recess, thus contributing to stable support in the milling disc body even if the primary radial clearance surface is rounded or tilted outwards from the corner clearance surface. In particular, this is useful for indexable milling inserts with two opposing cutting edges extending along the upper side, where radial support is provided below the currently non-active primary cutting edge. In this case, two recesses are formed, one in each primary radial clearance surface. The recesses can be formed during pressing and sintering operations prior to grinding, thereby ensuring stable support without having to grind the recesses. The portion of the side surface adjacent to the recess forms part of the primary radial clearance surface and can therefore also be bent with the same curvature as the upper portion of the primary radial clearance surface above the upper edge of the recess. Therefore, a recess is formed in the lower part of the main radial clearance surface. Preferably, the distance between the upper end of the recess and the midpoint of the main cutting edge should be at least 1 mm.

[0022] According to one embodiment, the central portion of the rake surface is recessed relative to the primary cutting edge. Therefore, the central portion of the rake surface is also recessed relative to the corner cutting edge and the auxiliary cutting edge adjacent to the corner cutting edge. Consequently, the recessed central portion of the rake surface generates a positive rake angle at the cutting edge, thereby facilitating chip formation with reduced cutting forces and lowering the risk of vibration (chatter) during milling.

[0023] According to one embodiment, the milling insert is symmetrical about a vertical plane including the midpoint of the main cutting edge and the central axis. Therefore, the corner cutting edges and optional auxiliary cutting edges are identical to each other, and the main cutting edge is divided into identical left-hand and right-hand portions. This means that the milling insert can be used on either side of the milling disc.

[0024] According to one embodiment, each axial clearance surface forms an obtuse interior angle η with the lower extending plane. Therefore, the milling insert has a so-called positive shape because the axial clearance surfaces are inclined inward toward the central axis. In other words, the axial clearance surfaces form a positive axial clearance angle on the milling insert. The milling insert can also be made as a double-sided milling insert with identical upper and lower sides, i.e., the cutting edge also extends around the lower side. In this case, the milling insert can have a waist to maintain a positive shape along the axial clearance surfaces, but the milling insert can also have a negative shape, where the side surfaces are parallel to the central axis. In both cases, the primary radial clearance surfaces can preferably form a right-angled interior angle with the lower extending plane, but can also form an acute-angled interior angle, such that a negative radial clearance angle is obtained at least in the upper portion of the primary radial clearance surface adjacent to the primary cutting edge. A negative clearance angle or a zero-degree clearance angle on the primary radial clearance surface below the primary cutting edge increases the toughness / strength of the primary cutting edge, which is particularly advantageous when the recess is provided in the lower portion of the primary radial clearance surface.

[0025] According to one embodiment, as seen in any section perpendicular to the central axis, at least the upper portion of the primary radial clearance surface is continuously curved along its entire extension with at least one radius of curvature. In other words, in this embodiment, the upper portion of the primary radial clearance surface can be described by a smoothly curved surface. As seen in a top view or in any section perpendicular to the central axis, the primary radial clearance surface and the primary cutting edge can be formed to have multiple radii of curvature. If a portion (lower portion) of the primary radial clearance surface is provided with the recess to improve the stability of the radial support of the milling insert, the recess will obviously form an edge in the lower portion of the primary radial clearance surface. However, the lower primary radial clearance surface on either side of the recess is thus preferably continuously curved in the same manner as the upper portion of the primary radial clearance surface. In this way, the entire primary radial clearance surface (except for the recess) can be subjected to a single grinding operation, which includes a continuously curved grinding path with at least one radius of curvature. This curvature may also include multiple radii of curvature. For example, the left and right portions of the main cutting edge and at least the upper portion of the main radial clearance surface can be formed to have the same radius of curvature, while the middle portion is formed to have a smaller radius of curvature. In this case, transition portions are formed between the portions, so that the main cutting edge and the main radial clearance surface are continuously curved or smooth.

[0026] According to one embodiment, as seen in the side view, the main cutting edge has an inclination relative to the upper extending plane at an interior angle β, where 3° ≤ β ≤ 10°. Preferably, 4° ≤ β ≤ 8°. Here, the angle β is measured in the side view between a line parallel to the upper extending plane and a line along the main extension of the right or left hand portion of the main cutting edge. This range is sufficient to provide a reduction in cutting force and an improvement in toughness on the main cutting edge without increasing the risk of, for example, tool breakage at the corner of the milling insert.

[0027] According to one embodiment, as seen in the top view, a first line is defined between the midpoint of the main cutting edge and either the first or second endpoint of the main cutting edge, and a second line is defined between the first and second endpoints of the main cutting edge, wherein the first line extends relative to the second line at an angle α, where 0.3° ≤ α ≤ 3°. Preferably, 0.7° ≤ α ≤ 2°. This angle affects the protrusion of the midpoint relative to the endpoint of the main cutting edge. Within the mentioned range, as seen in the side view, sufficient compensation for the concave shape of the main cutting edge can be achieved to obtain a flat bottom surface in the milled groove. Angles α and β can be set dependently on each other to ensure sufficient compensation. If overcompensation is required, or if the milling insert is mounted in the milling disc body with a larger negative radial angle (radial mounting angle), then angle α can be set, for example, in the upper part of the range.

[0028] According to one embodiment, the milling insert has a basic rectangular shape. In this embodiment, the milling insert may be square, or preferably elongated and have two main cutting edges extending along the two short sides of the elongated rectangular milling insert. The main cutting edges may also be arranged along the long side of the elongated rectangular milling insert.

[0029] Therefore, the milling insert is indexable and has two identical, alternately usable cutting edges formed in the transition between the upper and side surfaces. In this case, the milling insert is rectangular and has cutting edges extending on two opposite short sides along the central axis. This doubles the tool life of the milling insert compared to a milling insert with a single cutting edge. If the cutting insert is still symmetrical as described above, the cutting insert can be used on both the left and right sides of the milling machine.

[0030] The milling insert can be directly mounted in the insert holder of a three-sided milling cutter using screws, clamps, or similar fastening components. Alternatively, the milling insert can be mounted in a tool holder, which is then mounted in the milling disc body, providing support for the milling insert. The milling insert can also be mounted on a base plate that forms a bottom support for the milling insert, which is in turn supported by the milling disc body.

[0031] Other advantageous features and benefits of the invention will become apparent from the following detailed description. Attached Figure Description

[0032] Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0033] Figure 1 A perspective view of a milling insert according to a first embodiment of the present invention is shown.

[0034] Figure 2 It shows Figure 1 Another perspective view of the milling cutter insert.

[0035] Figure 3 It shows Figure 1 Side view of the milling cutter insert.

[0036] Figure 4 It shows Figure 1 Another side view of the milling cutter insert.

[0037] Figure 5 It shows Figure 1 Top view of the milling cutter insert.

[0038] Figure 6 It shows along Figure 3 The cross section of line VI–VI in the middle.

[0039] Figure 7A perspective view of a milling insert according to a second embodiment of the present invention is shown.

[0040] Figure 8 A perspective view of a milling cutter according to the present invention is shown.

[0041] Figure 9 It shows Figure 8 End view of the milling cutter in the image.

[0042] Figure 10 It shows Figure 8 Side view of the milling cutter in the image.

[0043] Figure 11 It shows Figure 8 Details of the milling cutter, and

[0044] Figure 12 It shows along Figure 10 The cross section of line XII-XII in the middle. Detailed Implementation

[0045] exist Figures 1 to 6 The image shows a milling insert 1 suitable for side milling and face milling according to a first embodiment of the present invention. The milling insert 1 has a basic rectangular shape, with its upper side 2 and lower side 3 connected by an outer peripheral surface 4. This outer peripheral surface 4 has two opposing long side surface portions forming an axial clearance surface 5 and two opposing short side surface portions forming a main radial clearance surface 6. The upper side 2 defines an upper extending plane P. U Furthermore, the lower side 3 defines the upper extending plane P. U Parallel lower extension plane P L The central axis C1 extends vertically through the upper extension plane P. U and the lower extension plane P L Furthermore, a central threaded hole is provided for securing the milling insert 1 to the milling cutter's disc.

[0046] In the illustrated embodiment, the milling insert 1 is single-sided and rotationally symmetrical about the central axis C1. A rake surface 7 is disposed on its upper side 2, and its lower side 3 includes a lower extending plane P. L An inwardly extending planar bottom surface 8 is designed to be positioned on a support surface within the milling cutter. Two opposing and identical cutting edges 9 are provided in the transition between the upper side 2 and the side surface 4 of the milling insert 1. The milling insert 1 is thus indexable and has two indexable positions. For ease of understanding, only one indexable position and one cutting edge 9 will be described in detail herein.

[0047] Each cutting edge 9 includes a main cutting edge 10, two corner cutting edges 11a and 11b, and two auxiliary cutting edges 12a and 12b. The main cutting edge 10 is raised relative to the central portion of the rake surface 7 and extends in the transition between the main radial clearance surface 6 and the rake surface 7. The two auxiliary cutting edges 12a and 12b extend in the transition between the associated axial clearance surfaces 13a and 13b and the rake surface 7. Each corner cutting edge 11a and 11b connects one of the auxiliary cutting edges 12a and 12b to the main cutting edge 10. The corner clearance surfaces 14a and 14b extend directly below the corner cutting edges 11a and 11b and connect the main radial clearance surface 6 to each of the axial clearance surfaces 13a and 13b.

[0048] Milling insert 1 about the midpoint p of the main cutting edge 10 mid The cutting edge 9 is mirror-symmetrical to the vertical plane of the central axis C1, thus dividing it into a left-hand portion and a right-hand portion, which includes the left-hand portion 15a and the right-hand portion 15b of the main cutting edge 10. When used in a three-sided end mill, the milling insert 1 can be mounted as either the right-hand or left-hand portion to form the cutting edge, as will be referred to below. Figures 8 to 12 As further described, Figures 8 to 12 A multi-purpose three-sided end mill is shown.

[0049] Main radial clearance surface 6 relative to lower extension plane P L Extending at right angles, while the axial clearance surface 5 is relative to the lower extending plane P. L Inclined at an obtuse interior angle η, which should typically be in the range of 95° to 110°. For example, in Figure 3 and Figure 6 As seen, the axial clearance surfaces 13a and 13b are slightly inclined further relative to the main part of the axial clearance surface 5.

[0050] exist Figure 3 A side view shows the milling insert, which illustrates the main radial clearance surface 6 and the main cutting edge 10. As seen in this view, the main cutting edge 10 has a concave shape. Therefore, the left-hand portion 15a and the right-hand portion 15b of the main cutting edge 10 extend from the adjacent corner cutting edges 11a, 11b toward the midpoint p. mid Inclined downwards, thus relative to the upper extension plane P U An acute interior angle β is formed. Preferably, angle β is in the range of 3° to 10°, or more preferably in the range of 4° to 8°. In the illustrated embodiment, angle β is 5°. Here, angle β is formed in relation to the upper extending plane P. U The parallel line and the midpoint p of the main cutting edge 10 mid and the endpoint p of the main cutting edge 10 end2The measurements are taken between the lines. In this embodiment, as seen in the side view, the left-hand portion 15a and the right-hand portion 15b of the main cutting edge 10 are generally straight, with the curved middle portion 15c connecting the left-hand portion 15a and the right-hand portion 15b.

[0051] exist Figure 5 In the top view shown, the main cutting edge 10 is convex, with the midpoint p mid Located at the end point p of the main cutting edge 10 end1 p end2 Beyond the imaginary line L between them, that is, the main cutting edge 10 moves from the corner cutting edges 11a and 11b toward the midpoint p. mid Tilt outwards, as seen in the top view. At the midpoint p... mid and the endpoint p of the main cutting edge end1 The angle α measured between the line connecting one of the endpoints and the imaginary line L should preferably be in the range of 0.3° to 3°, or more preferably in the range of 0.7° to 2°. In the illustrated embodiment, α = 1.7°.

[0052] As seen in the top view, the main cutting edge 10 is continuously curved, with the left-hand portion 15a and the right-hand portion 15b having the same radius of curvature (approximately 100 mm), while the middle portion 15c has a smaller radius of curvature of approximately 25 mm. A transition portion is formed between portions 15a, 15b, and 15c, causing the main cutting edge 10 to bend continuously (smoothly).

[0053] Such as Figure 6 As shown, as seen in any section perpendicular to the central axis C1, the main radial clearance surface 6 is also convex. In other words, the main radial clearance surface extends from the corner clearance surfaces 14a, 14b toward the midpoint p of the main cutting edge 10, parallel to the central axis C1. mid The imaginary line (not shown) slopes outward. As seen in the arbitrary cross-section, at least the upper portion of the main radial clearance surface 6 has the same shape and curvature as the main cutting edge 10 in the top view. Therefore, the main radial clearance surface 6 has a left-hand portion 6a, a right-hand portion 6b, and a middle portion 6c, the left-hand portion 6a and the right-hand portion 6b sharing a common radius of curvature of approximately 100 mm, and the middle portion 6c having a radius of curvature of approximately 25 mm. Alternatively, the main radial clearance surface 6 and the main cutting edge 10 can be formed with a single radius of curvature or with multiple radii of curvature forming convex portions with different bends.

[0054] A recess 16 is formed in each of the main radial clearance surfaces 6, extending from the lower side and more than halfway toward the main cutting edge 10. The recess 16 is configured to provide stable radial support when the milling insert 1 is mounted in the milling cutter, as will be further described below. The recess 16 is defined by a boundary edge 17 having two opposing side edges 18a, 18b and an upper edge 18c connecting the side edges 18a, 18b (see...). Figure 3 ).

[0055] like Figure 4 As shown in the side view, each corner cutting edge 11a, 11b and auxiliary cutting edges 12a, 12b extend relative to the upper plane P. U The common interior angle γ of 15° slopes downward from the bisectors of the corner cutting edges 11a and 11b.

[0056] Figure 7 A second embodiment of the milling insert 1 according to the present invention is shown. This milling insert 1 is... Figures 1 to 6 The only difference in the milling insert 1 according to the first embodiment shown is that this milling insert 1 has no auxiliary cutting edges. Instead, each cutting edge 9 includes only a main cutting edge 10 and two corner cutting edges 11a, 11b. Therefore, the axial clearance surface 5 is in the form of a flat surface extending between the opposing corner clearance surfaces 14a, 14b.

[0057] exist Figures 8 to 12 A multi-purpose three-sided end mill 20 (hereinafter referred to as a milling cutter) according to an embodiment of the present invention is shown. The milling cutter 20 includes a cutter body 21 having a shaft 22 extending along a longitudinal axis C2, the cutter body 21 being rotatable about the longitudinal axis C2 in a rotational direction R. The rear end 23 of the cutter body 21 is configured for mounting to a cutter spindle or the like, and a milling disc 24 is disposed at the front end 25 of the cutter body 21. Figures 1 to 6 In the embodiment shown, multiple milling inserts 1 are detachably mounted in the insert holder 26 of the milling disk 24 around its outer periphery. The milling inserts 1 are mounted alternately, wherein the left-hand portion 15a and the right-hand portion 15b of the main cutting edge 10 are configured to function during milling operations. A chip groove 27 is provided in front of the milling insert 1 in the rotational direction R.

[0058] Figure 11This diagram illustrates how a milling insert 1 is mounted in a milling disc 24 using screws 28. The bottom surface 8 of the milling insert 1 is configured to abut against a tangential support surface 29 disposed in the insert holder 26, thereby providing support for the milling insert 1 in the tangential direction of the milling cutter 1 (i.e., in the rotational direction R). The tangential support surface 29 is inclined relative to the longitudinal axis C2 of the milling cutter 20 and also inclined relative to the radial direction of the milling cutter 20. The radial mounting angle θ... r (That is, the upper extension plane P of the milling insert 1) U The angle between the radial direction line r of the milling cutter 20 and the radial direction line r is negative, thus providing sufficient radial clearance behind the main cutting edge 10. In the illustrated embodiment, the radial mounting angle θ r It is -15°, but the radial mounting angle θ r It can vary, for example, between -5° and -20°, preferably between -7° and -15°. Axial mounting angle θ a (That is, the upper extension plane P of the milling insert 1) U The angle between the milling cutter 20 and its central axis of rotation C2 is alternately arranged for the working left-hand cutting edge and the working right-hand cutting edge, wherein the axial clearance surface 5 of the milling insert 1 is relative to the lower extension plane P. L Inclined. In the illustrated embodiment, the axial mounting angle θ a It has a positive value of 5°, but the axial mounting angle θ a It can vary between 0° and 20°, preferably between 4° and 10°.

[0059] exist Figure 11 In the milling cutter 20, the insert holder 26 is configured to mount milling inserts, wherein the left-hand portion 15a, the left-corner cutting edge 11a, and the left-hand auxiliary cutting edge 12a of the main cutting edge 10 function during milling operations. An axial support surface 30 is provided in the milling disc 24 for supporting the non-functional side of the milling insert 1, wherein the non-functional axial clearance surface 5 of the milling insert 1 is positioned against the axial support surface 30. A radial support surface 31 is provided for supporting the milling insert 1 in the radial direction of the milling cutter 20. In the illustrated embodiment, as... Figure 12 As shown in the cross-section, the radial support surface 31 is configured to support the non-functional radial clearance surface 6 of the milling insert 1 at the horizontal height of the recess 16. Figure 12The cross-section shows the milling insert 1 and insert holder 26 with the screws removed. When the milling insert 1 is mounted using screw 28 and the central axis C1 of the milling insert 1 is aligned with the axis C3 of the screw hole provided in the milling disc 24, the contact point between the milling insert 1 and the radial support surface 31 will change slightly. The actual contact point will be located at the side edges 18a, 18b of the boundary edge 17 of the recess 16. Since the non-functional radial clearance surface 6 is curved, the recess 16 ensures stable radial support. Of course, the same effect can be achieved by alternatively providing a recess on the radial support surface of the milling disc.

[0060] When milling a groove in a workpiece using the milling cutter 20 shown, the main cutting edge 10 creates the bottom surface of the groove, and the auxiliary cutting edges 12a and 12b create the side surfaces within the groove. As seen in the side view, the downward inclination of the main cutting edge 10 reduces the cutting force because at the endpoint p of the main cutting edge 10... end1 p end2 When the corner cutting edges 11a and 11b closest to the workpiece first enter the workpiece, the main cutting edge 10 gradually enters the workpiece. As seen in the top view, the convex shape of the main cutting edge 10 compensates for the inclined main cutting edge 10 by removing material from the middle part of the groove, so that the machined bottom surface becomes flat.

[0061] The milling insert 1 according to the invention can be obtained from an insert blank produced by pressing and sintering in a powder metallurgy process. The milling insert blank is then subjected to peripheral grinding to form a cutting edge 9 and a side surface 4, which includes a curved radial clearance surface 6. An advantage of the milling insert according to the invention is that the cutting edge 9 and the side surface 4 can be ground in a single grinding operation to simultaneously produce a rounded main cutting edge 10 and a rounded radial clearance surface 6.

[0062] Of course, the present invention is not limited to the disclosed embodiments, but modifications and variations can be made within the scope of the appended claims. For example, the milling insert can be configured to have a main cutting edge extending above the long side surface portion of the milling insert, depending on the size of the milling insert. Tool holders and / or backing plates can also be used to support the milling insert in the milling disc.

Claims

1. A milling insert (1) for a three-flank milling cutter (20), the milling insert (1) comprising: - an upper side (2) comprising a rake surface (7), and the upper side (2) defining an upper extension plane (P U ), - a lower side (3) opposite the upper side (2), the lower side (3) defining a lower extension plane (P L ), wherein a central axis (C1) extends perpendicularly through the upper and lower extension planes (P U , P L ), - a side surface (4) extending between the upper side (2) and the lower side (3) around the outer periphery of the milling insert (1), wherein the side surface (4) comprises a main radial clearance surface (6), two opposite secondary axial clearance surfaces (5) and two corner clearance surfaces (14a, 14b) extending between the main radial clearance surface (6) and the secondary axial clearance surfaces (5), - at least one cutting edge (9) formed in the transition between the upper side (2) and the side surface (4), wherein each cutting edge (9) comprises a main cutting edge (10) formed in the transition between the rake surface (7) and the main radial clearance surface (6) and two corner cutting edges (11a, 11b) formed in the transition between the rake surface (7) and the corner clearance surfaces (14a, 14b), characterized in that: As seen in a side view of the milling insert (1), the main cutting edge (10) is inclined downwardly from the corner cutting edges (11a, 11b) towards a midpoint (p mid ) of the main cutting edge (10), and as seen in a top view of the milling insert, the main cutting edge (10) and the main radial clearance surface (6) are inclined outwardly from the corner cutting edges (11a, 11b) towards the midpoint (p mid ) of the main cutting edge (10), and the at least one cutting edge (9) further comprises two opposite secondary cutting edges (12a, 12b) adjacent to the corner cutting edges (11a, 11b), wherein each secondary cutting edge (12a, 12b) is formed in the transition between the rake surface (7) and a secondary axial clearance surface portion (13a, 13b), The shape of the main cutting edge (10) seen in the top view is the same as or substantially the same as the shape of at least the upper part of the main radial clearance surface (6) seen in any cross section perpendicular to the central axis (C1), and the main radial clearance surface extends at right angles relative to the lower extension plane (P L ) and the secondary axial clearance surface portions (13a, 13b) are inclined relative to the main portion of the secondary axial clearance surfaces (5).

2. The milling insert according to claim 1, wherein the main cutting edge (10) is convex as seen in a top view of the milling insert (1).

3. The milling insert according to claim 1, wherein each secondary cutting edge (12a, 12b) is inclined downwardly from the adjacent corner cutting edge (11a, 11b).

4. The milling insert according to any one of the preceding claims, wherein at least one recess (16) is formed in the main radial clearance surface (6).

5. The milling insert according to any one of the preceding claims, wherein a central portion of the rake surface (7) is recessed relative to the main cutting edge (10).

6. The milling insert according to any one of the preceding claims, wherein the milling insert (1 ) is symmetrical about a vertical plane comprising the midpoint (p mid ) of the main cutting edge (10) and the central axis (C1 ).

7. A milling insert according to any of the preceding claims, wherein each axial clearance surface (5) forms an obtuse internal angle η with the lower extension plane (P L ).

8. The milling insert according to any one of the preceding claims, wherein at least an upper portion of the main radial clearance surface (6) is continuously curved with at least one radius of curvature along its entire extension as seen in any cross section perpendicular to the central axis (C1).

9. The milling insert according to any one of the preceding claims, wherein the main cutting edge (10) has a inclination formed with an inner angle β in relation to the upper extension plane (P U ) seen in a side view of the milling insert, wherein 3° ≤ β ≤ 10°.

10. The milling insert according to any one of the preceding claims, wherein a first line is defined between the midpoint (p mid ) of the main cutting edge (10) and a first end point (p end1 ) or a second end point (p end2 ) of the main cutting edge (10) as seen in a top view of the milling insert, and a second line is defined between the first end point (p end1 ) and the second end point (p end2 ), wherein the first line extends at an angle a relative to the second line (L), wherein 0.3° < a < 3°.​​​​​​​​​​ 11. The milling insert according to any one of the preceding claims, wherein the milling insert (1) has a rectangular basic shape.

12. The milling insert according to claim 11, wherein the milling insert (1) is indexable by two identical, alternately usable cutting edges (9) formed in the transition between the upper side (2) and the side surface (4).

13. A triple wiper milling cutter (20) comprising a milling disc (24) and at least one milling insert (1) according to any one of the preceding claims, wherein each of the at least one milling insert (1) is removably mounted in an insert seat (26) of the milling disc (24).

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