Milling cutter

Abstract

A milling tool has a shank and a milling portion arranged along a longitudinal axis of the milling tool. The milling portion has at least one peripheral blade and a flute that adjoins a cutting edge of the peripheral blade. A radial spacing between the cutting edge and the longitudinal axis is selected on the basis of a specified compensation rotational speed such that a shell surface formed by the rotating cutting edge is circular cylindrical in the case of a rotation of the milling tool at the compensation rotational speed. The radial spacing of the cutting edge increases continuously or decreases continuously as the distance from the shank increases.

Claims

1.-6. (canceled)

7. A milling tool, comprising a shank and a milling portion which are arranged along a longitudinal axis of the milling tool, wherein the milling portion comprises at least one peripheral blade that extends over the milling portion, in the direction of the longitudinal axis, at least in portions with a flute that adjoins a cutting edge of the peripheral blade, wherein a radial spacing between the cutting edge and the longitudinal axis is selected on the basis of a specified compensation rotational speed at which a radial deflection of the cutting edge of the rotating milling tool occurs, such that a shell surface formed by the rotating cutting edge is circular cylindrical when the milling tool rotates at the compensation rotational speed.

8. The milling tool according to claim 7, wherein the radial spacing of the cutting edge increases or decreases continuously as a distance from the shank increases.

9. The milling tool according to claim 8, wherein the radial spacing of the cutting edge increases or decreases proportionally, in the direction of an end face of the milling tool, with the distance from the shank.

10. The milling tool according to claim 7, wherein the milling tool comprises a single peripheral blade that extends over the milling portion, in the direction of the longitudinal axis, at least in portions.

11. A method for producing a wall surface of a workpiece that is convexly or concavely curved in the direction of a longitudinal axis of a milling tool, wherein the milling tool according to claim 8, which tool rotates at a specified rotational speed, is displaced relative to the workpiece such that the rotating peripheral blade of the milling tool creates the wall surface, and wherein, in order to produce a wall surface that is convexly curved relative to the workpiece, the rotational speed of the rotating milling tool is selected so as to be lower than the compensation rotational speed of the milling tool, and wherein, in order to produce a wall surface that is concavely curved relative to the workpiece, the rotational speed of the rotating milling tool is selected so as to be greater than the compensation rotational speed.

12. A method for producing a wall surface of a workpiece that extends in a straight line in the direction of a longitudinal axis of a milling tool, wherein the milling tool according to any of claim 8, which tool rotates at a specified rotational speed, is displaced relative to the workpiece such that the rotating peripheral blade of the milling tool creates the wall surface, wherein, in order to produce a straight wall surface the rotational speed of the rotating milling tool is selected so as to be lower than the compensation rotational speed, and wherein the milling tool is displaced in the direction of the longitudinal axis, relative to the wall surface to be machined, such that in each case just a sub-portion of the peripheral blade that adjoins an end face of the milling tool comes into engagement with the workpiece during the milling process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a schematic and perspective view of a milling tool comprising a peripheral blade.

[0024] FIG. 2 is a view of the milling tool shown in FIG. 1, at an end face of the milling tool.

[0025] FIG. 3 is a schematic view of the radial spacing of the cutting edge of a conventional milling tool (right-hand side of a dotted longitudinal axis), and of the radial spacing of a peripheral region of the milling tool opposite the cutting edge (left-hand side), wherein the milling tool does not rotate.

[0026] FIG. 4 is a schematic view of the radial spacing of the cutting edge from the longitudinal axis (right-hand side), and of the radial spacing of the opposite peripheral region (left-hand side) in the conventional milling tool during a rotational movement, wherein the respective contours of the cutting edge and of the opposite peripheral region when the milling tool is stationary are indicated in dashed lines for the purpose of clarification.

[0027] FIG. 5 shows the radial spacing of the cutting edge of a milling tool designed according to the invention (right-hand side), and the radial spacing of an opposite peripheral region (left-hand side), when the milling tool is stationary.

[0028] FIG. 6 shows the radial spacing of the cutting edge relative to the longitudinal axis (right-hand side), and the radial spacing of the opposite peripheral region (left-hand side), during a rotational movement of the milling tool according to the invention, wherein the respective contours of the cutting edge and of the opposite peripheral region when the milling tool is stationary are indicated in dashed lines for the purpose of clarification.

[0029] FIG. 7 is a schematic view of a milling tool according to the invention, in which the radial spacing of the cutting edge is specified, in the case of a compensation rotational speed that is set in advance, such that the blade that protrudes radially to an increasing extent in the case of a stationary milling tool (solid line), is at a constant radial spacing from the longitudinal axis in the case of a rotational movement at the compensation rotational speed (dashed line).

[0030] FIG. 8 is a schematic illustration of a milling process, during which the milling tool shown in FIG. 7 rotates at the compensation rotational speed and in the process creates a wall surface of a workpiece that extends in a straight line in parallel with the longitudinal axis of the milling tool.

[0031] FIG. 9 is a schematic illustration of a milling process using the milling tool shown in FIG. 7, wherein the milling tool rotates at a rotational speed that is lower than the compensation rotational speed, and as a result a wall surface that is convexly curved towards the longitudinal axis of the milling tool is created in the workpiece.

[0032] FIG. 10 is a schematic illustration of a milling process using the milling tool shown in FIG. 7 that rotates at a rotational speed that is greater than the compensation rotational speed, and as a result creates a wall surface in the workpiece that is concavely curved towards the longitudinal axis of the milling tool.

DETAILED DESCRIPTION

[0033] A milling tool 1 shown schematically in FIGS. 1 and 2 comprises a single peripheral blade 2 which extends, proceeding from an end face 3 of the milling tool, along a longitudinal axis 4 over a milling portion 5 to an adjoining shank 6 of the milling tool. The shank 6 of the milling tool 1 is designed such that the milling tool 1 can be received and fixed in a spindle (not shown) of a milling machine. The milling tool 1 can be rotated by the spindle and can be displaced both along the longitudinal axis 4 and transversely to the longitudinal axis 4 during a rotation about the longitudinal axis 4 at a high rotational speed.

[0034] The peripheral blade 2 comprises a cutting edge 7 that starts at the end face and extends helically to the shank 6. A flute 8 extends, so as to follow the helical course of the cutting edge 7, adjacently to the cutting edge 7, which flute is formed by a recess in the milling portion 5 that is approximately semi-circular and extends in the radial direction until close to the longitudinal axis 4. The flute 8 also extends along the longitudinal axis 4, to the shank 6. Milling tools 1 are also conceivable in which the cutting edge 7 has a course deviating herefrom, for example a course of the cutting edge 7 along the longitudinal axis 4 that is uniform in the peripheral direction and constant. The milling tool 1 could also comprise a plurality of peripheral blades 2 which are for example arranged non-symmetrically with respect to one another or extend in a non-symmetrical manner, such that an imbalance is also created in the case of two or more than two peripheral blades 2.

[0035] The flute 8 that extends beside the cutting edge 7 makes the distribution of mass, specified in the radial direction perpendicularly to the longitudinal axis 4, in the shank 6, noticeably asymmetrical, such that an imbalance is created. In the case of a rotational movement of the milling tool 1 about the longitudinal axis 4 thereof, the outwardly oriented centrifugal force acts more strongly on the relevant portion of the milling tool 1 in a peripheral region 9 opposite the flute 8, owing to the greater mass, than in the region of the flute 8, in which only a smaller centrifugal force acts owing to the mass of the milling tool 1 that is reduced by the recess of the flute 8. This leads to a resultant centrifugal force, indicated schematically by an arrow 10 in FIG. 2, which bends and deflects the milling tool 1 in said portion, as a result of which the cutting edge 7 is displaced towards the opposite peripheral region and the radial spacing between the cutting edge 7 and the longitudinal axis 4 decreases.

[0036] The influence of the centrifugal force on a conventional milling tool 1 is shown schematically in FIGS. 3 and 4. In this case, just like in the following figures, a projection of the radial outer course of a cutting edge 7 is shown along the longitudinal axis 4 in each case, on a right-hand side of the longitudinal axis 4. A projection of the radial outer course of an outer face of a peripheral region 9 opposite the cutting edge 7 is shown on a left-hand side of the longitudinal axis 4. The course, shown in each case, of the cutting edge 7 along the longitudinal axis 4 corresponds, in the case of a rotating milling tool 1, to the resulting cutting contour or milling contour. In the case of the conventional milling tool 1 shown in FIGS. 3 and 4, during production or in a stationary milling tool 1 a radial spacing of the cutting edge 7 extends in parallel with the longitudinal axis 4 because the influence of the centrifugal force on the rotating milling tool 1 is negligible. In the case of a rotational movement of the milling tool 1 about the longitudinal axis 4, as shown in FIG. 4, a centrifugal force is generated that acts unevenly on the milling tool 1 and that causes a deflection of the cutting edge 7 to a smaller radial spacing from the longitudinal axis 4. This effect or the deflection of the milling tool 7 increases as the distance from the shank 6 increases, such that a curved course of the cutting contour of the cutting edge 7 along the longitudinal axis 4 is established and the deflection of the cutting edge 7 is greatest in the region of the end face 3 of the milling tool 1.

[0037] The undesired effects of the deflection of the cutting edge 7 caused by the centrifugal force can be counteracted in that the cutting edge 7 is not at a constant radial spacing from the longitudinal axis 4 when the milling tool 1 is stationary, as is shown schematically in FIGS. 5 and 6. In this embodiment, shown by way of example, the radial spacing of the cutting edge 7 continuously increases, in a gradual manner, starting at the shank 6 and towards the end face 3 of the milling tool 1. The radial spacing of the cutting edge 7 from the longitudinal axis 4 is greatest in the region of the end face 3 of the milling tool 1. If the milling tool 1 is rotated, the centrifugal force causes a resultant deflection of the cutting edge 7 due to the distribution of mass which is non-uniform in the peripheral direction owing to the flute 8, such that the radial spacing of the cutting edge 7 from the longitudinal axis 4, initially specified as large, decreases, and a course of the cutting edge 7 that is at least approximately straight and extends in parallel with the longitudinal axis 4, and thus a straight cutting contour or milling contour, results again, during the rotational movement of the milling tool 1, i.e. during the use thereof in a milling process.

[0038] In the case of a stationary milling tool 1, the course of the cutting edge 7 or the course of the radial spacing of the cutting edge 7 can be specified such that, for a compensation rotational speed that is specified in advance, the deflection of the cutting edge 7 caused by the centrifugal force results in a straight cutting contour.

[0039] It is also possible, by means of tests and measurements carried out in advance, to determine a course of the cutting edge 7 of the milling tool 1, for a compensation rotational speed specified in advance and for a material of a workpiece specified in advance, which course compensates not only for the resulting centrifugal force but instead also other influences such as the cutting force or the chip removal, etc., during a milling process at the compensation rotational speed in the relevant material, in order to create, as a result, a cutting contour or corresponding wall surface of a workpiece that extends in a straight line in the direction of the longitudinal axis.

[0040] The process of influencing the course of the cutting edge 7 by means of the rotational speed of a rotational movement of the milling tool 1 can also be used, according to the invention, in order to also purposefully create a convexly or concavely curved course of the wall surface, in addition to a course of a wall surface of a workpiece that is as straight as possible. When stationary, the course (shown in a solid line) of the cutting edge 7 of a milling tool 1 according to the invention shown in FIG. 7 increases continuously as the distance from the shank 6 increases, wherein the increasing radial spacing of the cutting edge 7 from the longitudinal axis 4 has been determined and specified for a compensation rotational speed specified in advance, in such a way that the deflection of the cutting edge caused during a rotational movement at the compensation rotational speed is completely compensated and a straight cutting contour is established which is shown in dashed lines.

[0041] In the case of a milling process shown in FIG. 8, during which the milling tool 1 rotates at the compensation rotational speed, a wall surface 12 that has a straight course in the direction of the longitudinal axis 4 of the rotating milling tool 1 is created on a workpiece 11 machined by the milling process. If the milling tool 1 is moved transversely to the longitudinal axis 4, a completely planar wall surface 12 can thereby be created on the workpiece 11.

[0042] If the milling tool 1 rotates at a lower rotational speed during a milling process, as shown schematically in FIG. 9, the deflection of the cutting edge 7 caused by the centrifugal force is less than the radius increase, specified in advance, in the cutting edge course, with the result that the curved cutting contour, as is shown in FIG. 7, is not completely compensated and a wall surface 12 that is accordingly convexly curved in the direction of the longitudinal axis 4 is created on the workpiece 11. An undercut of this kind can be used advantageously for a plurality of applications.

[0043] In an analogous manner, the milling tool 1 can rotate, during a milling process, at a rotational speed that is higher than the compensation rotational speed, such that the influence of the centrifugal force is greater and the initially curved course of the cutting edge 7 is over-compensated. This results in a curved course, already known in conventional milling tools 1, of the cutting edge 7 or of the cutting contour towards the longitudinal axis 4, or a wall surface 12 of the workpiece 11 that is correspondingly convexly curved towards the longitudinal axis 4.

[0044] The milling tool 1 according to the invention can accordingly be used to create both straight wall surfaces 12 and convexly or concavely curved wall surfaces 12 of a workpiece 11 in a purposeful and controlled manner, in accordance with the respective rotational speeds, during a milling process, without it being necessary to change the tool or for example to tilt the rotating milling tool.