Finishing tool, in particular end milling cutter

Abstract

A finishing tool of an end milling cutter can comprise: a chip-removing milling edge, which extends continuously with respect to the tool axis (A) over an axial length (L) on a circumferential surface (U), which is rotationally symmetrical about the tool axis, and removes workpiece chips from the workpiece surface at a radial chip-removing engagement depth (T to Tmax), and at least one non-cutting pressing ridge, which extends continuously axially with respect to the tool axis (A) over an axial length (L) on a circumferential surface which is rotationally symmetrical about the tool axis, is arranged following an associated milling edge by a pitch angle, and presses over its entire axial length (L), during the milling movement, at a radial non-cutting engagement depth (T or R.sub.SR.sub.D) with respect to the tool axis into the workpiece surface machined by the associated milling edge, and smooths said workpiece surface.

Claims

1. A finishing tool, in particular end milling cutter, the tool a) being suitable and intended for removing material over the area of a workpiece surface and for smoothing and/or compressing the workpiece surface in a milling movement by rotation about a tool axis (A) in a predetermined direction of rotation (D) with simultaneous advancing relative to the workpiece surface, the finishing tool comprising: b) at least one chip-removing milling edge, wherein the chip-removing milling edge: b1) extends continuously and without interruptions axially with respect to the tool axis (A) over an axial length (L) on a cylindrical, circumferential surface (U), which is rotationally symmetrical about the tool axis, and at a constant radial distance (R.sub.S) from the tool axis (A); and b2) is designed in such a manner that, over its entire axial length (L), during the milling movement, it removes workpiece chips from the workpiece surface at a radial chip-removing engagement depth (T to Tmax) with respect to the tool axis; and b3) wherein the chip-removing engagement depth (T to Tmax) of the milling edge (30) lies in an interval of 6% to 30% of its radial distance (R.sub.S) from the tool axis (A); and c) at least one non-cutting pressing ridge, wherein the non-cutting pressing ridge: c1) extends continuously and without interruptions axially with respect to the tool axis (A) over an axial length (L) on an, in particular cylindrical, circumferential surface which is rotationally symmetrical about the tool axis, c2) is arranged following an associated milling edge by a pitch angle (), as seen in the direction of rotation (D), and c3) is designed in such a manner that it presses over its entire axial length (L), during the milling movement, at a radial non-cutting engagement depth (T or R.sub.SR.sub.D) with respect to the tool axis into the workpiece surface machined by the associated milling edge, and smooths and/or compresses said workpiece surface; and c4) the pressing ridge has a pressing surface which increases in its radial distance (r.sub.D, R.sub.D) from the tool axis (A) in the opposite direction to the direction of rotation (D) up to a maximum radial distance (R.sub.D); d) wherein the chip-removing engagement depth (T to Tmax) is smaller by at least a factor of 5 than the axial length, and wherein the non-cutting engagement depth (T or R.sub.SR.sub.D) is smaller by at least a factor of 10 than the axial length (L).

2. The finishing tool as claimed in claim 1, wherein: each pressing ridge is separated from a milling ridge with the associated milling edge leading in the direction of rotation by a first separating groove which is provided in particular as a cooling and/or lubricating groove for supplying coolant and/or lubricant to the pressing ridge and/or to the pressing surface; each milling ridge is separated from a pressing ridge following in the direction of rotation by a second separating groove which is provided in particular as a chip groove for removing chips from the milling edge; and the first separating groove, in particular cooling and/or lubricating groove, preferably has a radial groove depth (R.sub.Dr.sub.a) which is smaller by 10% to 35%, than the radial groove depth (R.sub.Sr.sub.i) of the second separating groove, in particular chip groove.

3. The finishing tool as claimed in claim 1, wherein: the pressing surface increases in its radial distance (r.sub.D, R.sub.D) from the tool axis (A) in the opposite direction to the direction of rotation (D) as far as a pressing spine (44) in a rear region of the pressing surface, as seen in the direction of rotation (D), and increases substantially linearly, wherein the difference of maximum radial distance (R.sub.D) and minimum radial distance (r.sub.D) defines a maximum non-cutting engagement depth; as seen in the opposite direction to the direction of rotation (D), the pressing surface or the pressing spine is adjoined by a free surface and/or by a back surface of the pressing ridge, which back surface is adjacent to a separating groove, in particular chip groove; a radially inwardly running front surface of the pressing ridge is arranged upstream of the pressing surface, as seen in the direction of rotation (D), said front surface being adjacent to a cooling and/or lubricating groove; and/or the pressing spine has a round bevel, typically with a width of 0.01 to 0.50 mm.

4. The finishing tool as claimed in claim 1, wherein: a shaping angle (1) of the pressing surface of between 5 and 50 is selected; a free angle (2) of the free surface of the pressing ridge of between 5 and 60 is selected; and/or an angle of inclination (3) of the front surface of the pressing ridge of between 15 and 85 is selected.

5. The finishing tool as claimed in claim 1, wherein: each milling edge is formed on a milling ridge, or as seen in the opposite direction to the direction of rotation (D), the milling edge is adjoined by a free surface and/or by a back surface, in particular of the milling ridge, which back surface is adjacent to a separating groove, in particular cooling and/or lubricating groove, and/or wherein a rake surface which is adjacent to a chip groove is arranged upstream of the milling edge, as seen in the direction of rotation (D); and wherein preferably a rake angle () of the rake surface is selected from a range of 0 to 20, for example 5 to 10, and/or wherein preferably a free angle () of the free surface of the milling ridge of between 4 and 45 is selected.

6. The finishing tool as claimed in claim 1, wherein the pitch angle () between a milling edge and directly following the pressing surface, as seen in the direction of rotation (D), is smaller by 5% to 30%, than the pitch angle () between the pressing surface, and the milling edge directly following the latter, as seen in the direction of rotation (D).

7. The finishing tool as claimed in claim 1, wherein: in each case the same axial position along the tool axis (A), over the entire axial length (L), the maximum radial distance (R.sub.D) of the pressing ridge, of the pressing surface or a pressing spine, in the rear region of a pressing surface of the pressing ridge, as seen in the direction of rotation (D), from the tool axis (A) is greater by 0.01% to 5%, preferably by 0.1% to 2%, than the radial distance (R.sub.S) of the associated preceding milling edge from the tool axis (A), such that a radial excess length of the pressing ridge in relation to the milling edge is preferably defined; and the radial excess length axially with respect to the tool axis A is constant at least in sections, preferably over the entire axial length (L).

8. The finishing tool as claimed in claim 1, wherein: each pressing ridge and the associated milling edge in each case extends twisted by a helix angle (), in particular along a helix, wherein the helix angle () is constant in the axial direction or else varies at least in sections and/or is selected in particular between 10 and 80, in particular between 30 and 50, the maximum radial distance (R.sub.D) of the pressing ridge, in particular the pressing surface (40) and/or the pressing spine, in the rear region of the pressing surface of the pressing ridge, as seen in the direction of rotation (D), from the tool axis (A), and the radial distance (R.sub.S) of the associated preceding milling edge from the tool axis (A) is in each case constant preferably over the entire axial length (L), and/or the milling edge and pressing ridge run parallel to each other, or the pitch angle is constant over the entire axial length (L).

9. The finishing tool as claimed in claim 1, wherein: the non-cutting engagement depth (R.sub.Dr.sub.D) is smaller than the chip-removing engagement depth (T to Tmax) by at least a factor of 3 to 12; the chip-removing engagement depth (T to Tmax) lies in an interval between the non-cutting engagement depth (R.sub.Dr.sub.D) and the groove depth (R.sub.Dr.sub.a) of the first separating groove, in particular cooling and/or lubricating groove; and/or in an interval of 6% to 30% of the radial distance (R.sub.S) of the milling edge and/or corresponds at least to the difference of the maximum radial distance (R.sub.D) of the pressing ridge, in particular the pressing surface thereof, and the radial distance (R.sub.S) of the milling edge.

Description

(1) The invention is also illustrated below in respect of further features and advantages with reference to the description of an exemplary embodiment of the invention and in the attached schematic drawings, in which:

(2) FIG. 1 shows a side view of a finishing tool in an embodiment with two milling edges and two pressing ridges,

(3) FIG. 2 shows a side view of a finishing tool in an embodiment with three milling edges and three pressing ridges,

(4) FIG. 3 shows a front view of the finishing tool according to FIG. 2,

(5) FIG. 4 shows the finishing tool according to FIG. 2 or FIG. 3 in a cross section,

(6) FIG. 5 shows an enlarged illustration of a pressing ridge of the finishing tool according to FIGS. 2 to 4 in a cross section, and

(7) FIG. 6 shows an enlarged illustration of a milling edge of the finishing tool according to FIGS. 2 to 4 in a cross section.

(8) The finishing tool 1 in the embodiments according to FIG. 1 or FIG. 2 has a shaft 2 with a head part 5 at its end. The shaft 2 is rotatable together with the head part 5 about a tool axis A running through the shaft 2 centrally and longitudinally. The shaft 2 is as a rule shaped substantially cylindrically, i.e. substantially in circular form in cross section, but, in addition to the circular form, can also have other, even increasing or decreasing and/or shape-changing cross-sectional forms. During operation, the finishing tool 1 is held or clamped at an end of the shaft 2 remote from the head part 5 in a machine-tool clamping device (not illustrated) or a tool holder or a tool chuck, which is coupled to at least one drive for driving or moving the tool 1 in a rotational movement about the tool axis A in the direction of rotation D and in an advancing movement relative to the workpiece surface, typically parallel to the workpiece surface.

(9) The head part 5 has one or more material milling regions 3 and one or more material shaping regions 4, wherein the number of material shaping regions 4 preferably corresponds to the number of material milling regions 3. In the embodiment according to FIG. 1, this number is in each case 2, and, in the embodiment according to FIGS. 2 to 4, this number is in each case 3. In the circumferential direction or direction of rotation D, each material milling region 3 is followed by an associated material shaping region 4.

(10) Each material milling region 3 has a continuous milling ridge 7 with a milling edge 30 which is continuous in an axial direction with respect to the tool axis A.

(11) Each material shaping region 4 has a pressing ridge 8 which is continuous in the axial direction and has a pressing surface 40, which is continuous in the axial direction, and a pressing spine 44.

(12) A separating groove 9 is formed between each milling ridge 7 and the associated following pressing ridge 8, said separating groove preferably being provided as a cooling and/or lubricating groove for cooling and/or lubricating the working regions, in particular the pressing surface 40, by coolant and/or lubricant, for example an oil, being supplied via the groove 9.

(13) A separating groove 6 is likewise formed between each pressing ridge 8 and the following milling ridge 7, said separating groove also being provided as a chip groove for receiving and removing the milling chips of the associated milling edge 30.

(14) As illustrated, for example, in FIG. 4, each chip groove 9 extends to a depth which lies in an inner radius or core radius r.sub.i, while, by contrast, each separating groove, in particular cooling and/or lubricating groove, 6 preferably only extends to a depth which corresponds to an outer radius r.sub.a, wherein as a rule r.sub.a>r.sub.i.

(15) In the exemplary embodiment illustrated, the material milling regions 3 and their milling ridges 7 and milling edges 30 and also the material shaping regions 4 and their pressing ridges 8 and pressing surfaces 40 encircle the central tool axis A in a helix profile or along a helix, i.e. are inclined or twisted by a helix angle with respect to the tool axis A toward a cross-sectional plane (or: normal plane). The helix angle () can be selected, for example, to be between 10 and 80, in particular between 30 and 50.

(16) The milling edges 30 of the material milling region 3 in each case as outermost lines or regions of the respective material milling region 3 run at a constant radius (or: radial distance) R.sub.S with respect to the tool axis A, i.e. on a cylindrical circumferential surface U with said radius R.sub.S.

(17) The pressing spines 44 as outermost points of the respective material shaping regions 4 likewise run with the constant radius R.sub.D on a cylindrical circumferential surface U having this radius R.sub.D. The pressing surfaces 40 of the pressing ridges 8 of the material shaping regions 4 increase from a front innermost point or region with the radius r.sub.D, as seen in the direction of rotation D, radially outward as far as the outermost point or region on the pressing spine 44 with the radius R.sub.D, for example in a linear or flat profile, which can be simply produced by means of a ground section, in particular at a shaping angle 1 to a tangential plane TE on the pressing spine 44, as shown in FIG. 4, or with a certain, preferably convex, curvature.

(18) The shaping angle 1 can be selected, for example, to be between 5 and 50. The pressing spine 44 can have a round bevel, typically with a width of 0.01 to 0.50 mm, which prevents the material shaping region 4 from cutting into the material to be machined, and assists the smoothing of the material on the workpiece surface. A front surface 46 is mounted upstream of the pressing surface 40 in the direction of rotation D, said front surface being able to have an angle of inclination 3 with respect to the tangential plane TE (FIG. 4) that can be selected, for example, to be between 15 and 85.

(19) Behind the pressing spine 44, as seen in the direction of rotation D, as also illustrated in FIG. 4, each material pressing region 4 and its pressing ridge 8 has a free surface 45 with the free angle 2 with respect to the tangential plane TE, which free surface is then adjoined by a back surface 47 which, in turn, is adjacent to a following separating groove 6 which separates the material pressing region 4 from the following material milling region 3 and preferably serves as a chip groove for removing chips. The free angle 2 of the free surface 45 can be selected, for example, to be between 5 and 60.

(20) Each material milling region 3 has its milling edge 30 on its front region in the direction of rotation D. A rake surface 36, which leads into the milling edge 30, on the front side of the milling ridge 7 is inclined at a rake angle to the normal of the tangential plane TE, which rake angle is preferably a positive rake angle of 0 to 20, for example approx. 5 to 10.

(21) The milling edge 30 is rearwardly adjoined in the direction of rotation D by a free surface 35 with the free angle of between 4 and 45 with respect to the tangential plane TE (cf. FIG. 6), which free surface merges in turn into a back surface 37 of the milling ridge 7. The back surface 37 is adjacent to a separating groove 9, in particular a lubricating groove 9, when lubricant is supplied, which separating groove separates the material milling region 3 from a material shaping region 4 following in the direction of rotation D.

(22) Each milling edge 30 and 31 to 33 is formed continuously without interruptions and preferably runs as a smooth finishing milling edge without chip dividers along a circumferential surface U which is rotationally symmetrical about the tool axis A and, in the exemplary embodiment illustrated, is a cylinder surface.

(23) According to one embodiment, the volume of the chip groove 6 decreases axially with respect to the tool axis A away from the end side 10, but may also remain constant or increase.

(24) The pitch angle between a milling edge 31 or 32 or 33 and a pressing spine 44 of a pressing surface 41 or 42 or 43, which is downstream, as seen in the direction of rotation D, is smaller, preferably smaller by 5% to 30%, than the pitch angle between the pressing spine 44 of said pressing surface 41 or 42 or 43 and the milling edge 32 or 33 or 31 following the latter, as seen in the direction of rotation D. It is thereby assisted that the partial surface just milled by one of the milling edges 31 or 32 or 33 is immediately smoothed by the downstream pressing surface 41 or 42 or 43, as seen in the direction of rotation D. In a preferred, but not absolutely required, uniform pitch, +=360/n, wherein n is the number of milling edges 31 to 33 and of the pressing surfaces 41 to 43, here, for example, where n=3, i.e. +=120. In the exemplary embodiment illustrated, the pitch angle is, for example, =55 and the pitch angel =65.

(25) In all of the cases mentioned, the arrangement and design of the milling edges and pressing ridges and of the separating grooves located in between permit continuous surface machining of the workpiece, wherein the workpiece 1 is generally moved at a feed rate in which its tool axis A is directed parallel to the workpiece surface, with simultaneous rapid rotation about its tool axis A, i.e. during a typical milling movement, in particular of an end milling cutter.

(26) The milling ridges 7 and pressing ridges 8 and the separating groves 6 and 9 located in between are preferably all formed integrally and/or of one material and/or are produced in a material-removing manner, for example by grinding.

(27) In the exemplary embodiment illustrated, the direction of rotation D of the finishing tool 1 about the tool axis A is in the clockwise direction, i.e. the tool 1 is designed to rotate clockwise, but, of course, may also be designed to rotate counterclockwise.

(28) A protective bevel 11 can be provided on the outer region on the end side 10 of the finishing tool 1 and the head part 5 thereof. Furthermore, various free surfaces and/or spiral face inclinations can be provided for the milling edges 30 and pressing surfaces 40 which peter out on the end side 10.

(29) In a particularly advantageous embodiment, the radius R.sub.D of the material shaping region 4, in particular of the pressing spine 44, is selected to be somewhat larger than the radius R.sub.S of the milling edge 30, typically by 0.01% to 5%, preferably by 0.5% to 1%, i.e. R.sub.D lies within a range of 1.001 R.sub.S to 1.05 R.sub.S and preferably by 1.005 R.sub.S to 1.01 R.sub.S. It is therefore ensured that the material shaping region 4 slightly presses, or engages in a slightly shaping or smoothing manner, with its pressing surface 40 as far as the pressing spine 44 into that partial surface of the workpiece which has already been machined by the preceding material milling region 3 with its milling edge 30, and further smooths said partial surface.

(30) A maximum smoothing depth or maximum radial engagement depth T of the material shaping region 4 and of its pressing ridge 8 corresponds to the difference R.sub.Dr.sub.D and therefore to the radial extent of the pressing surface 4. The actual smoothing depth or radial non-cutting engagement depth of the material shaping region 4 and of its pressing ridge 8 customarily corresponds to the difference R.sub.DR.sub.S from the radii of pressing spine 44 and milling edge 30 and is customarily lower by at least a factor of 3, preferably a factor of 12, than the chip-removing engagement depth.

(31) The milling edge 30 at the front end of the milling ridge 7 therefore removes a chip from the workpiece surface (not illustrated) and, immediately subsequently, the pressing surface 40 of the pressing ridge 8 engages in said region in a smoothing manner in order to achieve an even better surface quality than has already been achieved with the milling edge 30, which is designed as a finishing edge. The chip here is dependent in respect of its length on the number of milling edges 31 to 33 and the pitch angle and in respect of its thickness on the radial chip-removing engagement depth of the milling edge 30 or 31 to 33 which typically lies in an interval of between T=R.sub.Dr.sub.D and the theoretically maximum value Tmax=R.sub.Sr.sub.a and/or in an interval of 6% to 30% of the radius R.sub.S.

(32) The axial length L of the milling edges 30 or 31 to 33 corresponds to the length projected onto the cylinder axis (Z axis) of the cylindrical circumferential surface, on which or along which the milling edges 30 or 31 to 33 run. The arc length or actual length of the milling edges 31 to 33 and of the pressing ridges 40 or 41 to 43 is greater than the axial length L and is dependent on the radius and the revolving angle or polar angle, about which the milling edge winds or revolves from its start to the end about the central axis A.

(33) The arc length or actual length of the milling edges 30 and 31 to 33 is greater than the axial length L projected onto the tool axis A and, in the case of a helical shape, corresponds to
{square root over (R.sub.S.sup.2.sup.2+L.sub.2)}

(34) The arc length or actual length of the pressing ridges 40 or 41 to 43 is greater than the axial length L projected onto the tool axis A and, in the case of a helix, is
{square root over (R.sub.D.sup.2.sup.2+L.sup.2)}.

(35) The milling edges 30 and 31 to 33 and the pressing ridges 40 and 41 to 43 normally have the same axial lengths L and the same helix angles and therefore also the same revolving angles or polar angles = and therefore also the same arc lengths.

(36) The finishing tool 1 or the shaft 2 can be formed from different materials, inter alia, in addition to a tool steel, in particular a high speed steel (HSS steel) or a cobalt-alloyed high speed steel (HSS-E steel), and preferably also, at least in the head part 5 or at the pressing ridges 8 and milling ridges 7, from a carbide, in particular solid carbide, or from a carbide alloy, in particular P steel or K steel or Cermet, or from sintered carbide, in particular from tungsten carbide or titanium nitride or titanium carbide or titanium carbon nitride or aluminum oxide, or from cutting ceramics, in particular polycrystalline boron nitride (PKB), or from polycrystalline diamond (PKD). The surface of the finishing tool 1, in particular the head part 5, is preferably provided with a coating in order to further to improve the finishing properties and also to permit adaptation to different work-piece materials.

(37) The previous exemplary embodiments describe the use of the finishing tool 1 in circumferential milling. However, it is also possible to use a finishing tool 1 according to the invention in end milling, i.e. during machining of the workpiece, in which the tool axis A is perpendicular instead of parallel to the workpiece surface and the milling tool is thereby advanced perpendicularly to the workpiece. In such an exemplary embodiment of a finishing tool 1, the pressing ridges 8 or milling edges 7 with the material shaping regions 4 or material cutting regions 3 are arranged on the end side 10 of said finishing tool.

(38) The finishing tool 1 is depicted here with two or three milling ridges 7 and milling edges 31 to 33 and two or three pressing ridges 8 and pressing surfaces 41 to 43, but may also be formed with one, four, five, six or even more milling ridges and pressing ridges.

(39) Instead of a helical profile, as illustrated, in particular also a rectilinear profile in a direction parallel to the tool axis A on a cylinder surface as the circumferential surface U or else in a direction inclined with respect to the tool axis A, for example on a conical surface as circumferential surface U or else on a spherical circumferential surface U or in general a circumferential surface U which is rotationally symmetrical to the tool axis A is also possible.

(40) Even though the invention has been explained in the exemplary embodiments and in the figures primarily with reference to an end milling cutter, it is likewise also applicable to other types of milling cutter, in which a continuous removal of material over an area of the workpiece takes place with continuous milling edges, for example in the case of slitting milling cutters, angle milling cutters, groove milling cutters, roll milling cutters, disk milling cutters, profile milling cutters, ball milling cutters, prism milling cutters, but with the exception of thread milling cutters, in which a removal of material takes place only in a small partial region of the surface in order to produce the thread and an entirely specific helical movement of the milling cutter is required.

(41) In the case of these milling cutters, the milling edges and the pressing ridges likewise lie on rotationally symmetrical circumferential surfaces, but the latter are not, in all of the types of milling cutter mentioned, cylindrical circumferential surfaces with a constant radial distance or radius in the axial direction with respect to the tool axis A, but may also differ therefrom, for example in the case of the angle milling cutter in the form of a cone or in the case of ball milling cutters in the form of a partially spherical surface which lies in a hemisphere, and, in the case of profile milling cutters, for example in the form of concave, curved, rotationally symmetrical surfaces, for example similarly to a quarter circle, or, in the case of a prism milling cutter, in the form of a triangle pointing with the point outward, in longitudinal section. A common feature of all these circumferential surfaces of these types of milling cutters is that they increase monotonously in an axial direction at a radial distance or radius from the tool axis A, generally as seen in the axial direction from the end surface of the milling cutter (or: from the front to the rear). By contrast, in the case of a thread milling cutter, the radial distance or radius of the thread milling tooth cutting edge in the axial direction with respect to the tool axis A initially increases, according to the thread profile (on the first thread flank), and then decreases again after the maximum of the milling tooth (tooth head) is exceeded (on the second thread flank).

LIST OF REFERENCE SIGNS

(42) 1 Finishing tool 2 Shaft 3 Material cutting region 4 Material shaping region 5 Head part 6 Chip groove 7 Milling ridge 9 Pressing ridge 9 Lubricating groove 10 End side 11 Protective bevel 30 Milling edge 31, 32, 33 Milling edge 35 Free surface 36 Rake surface 37 Back surface 40 Pressing surface 41, 42, 43 Pressing surface 44 Pressing spine 45 Free surface 46 Front surface 47 Back surface D Direction of rotation A Tool axis U Circumferential surface R.sub.D, r.sub.D Pressing ridge radius R.sub.S Cutting edge radius r.sub.i Inner radius r.sub.a Outer radius TE Tangential plane 1 Shaping angle 2 Free angle 3 Angle of inclination Free angle Rake angle , Pitch angle L Axial length T Engagement depth Tmax Maximum engagement depth