Milling tool, use thereof and milling process

Abstract

A milling tool includes a cutting insert, a holder, a fastener and a shim. The fastener forms a first channel cooperatively with the cutting insert. The first channel is configured to direct coolant towards a top side of the insert. In order to better prevent thermal fatigue of the cutting insert under milling conditions, the shim includes a second channel configured to direct coolant towards a clearance side of the cutting insert. A method of using a milling tool and a milling process are also provided.

Claims

1. A milling tool, comprising: a cutting insert, a holder, a fastener and a shim; said cutting insert including a cutting edge, a clearance side and an insert top side; said holder having a base channel; said fastener having a head portion supporting said fastener against said cutting insert and said fastener having an axial portion securing said fastener to said holder, said axial portion extending through said cutting insert, and said axial portion extending at least partly through said shim; said fastener forming a first channel cooperatively with said cutting insert, said first channel configured to direct coolant towards said insert top side, and said first channel being in fluid communication with said base channel of said holder; and said shim being disposed between said cutting insert and said holder, said shim including a second channel configured to direct coolant toward said clearance side, and said second channel being in fluid communication with said base channel.

2. The milling tool according to claim 1, wherein said second channel has an outlet opening covered partly by said cutting insert on parts of said clearance side, permitting coolant to still exit from said second channel but be obstructed by said cutting insert.

3. The milling tool according to claim 1, wherein said shim includes a plurality of shim channels, said second channel is a shim channel of said plurality of shim channels, each shim channel is configured to direct coolant towards said clearance side, each shim channel is in fluid communication with said base channel, and each shim channel has an outlet opening covered partly by said cutting insert on parts of said clearance side, permitting coolant to still exit from each of said shim channels but be obstructed by said cutting insert.

4. The milling tool according to claim 3, wherein at least two outlet openings of said shim channels emit coolant jets and are positioned to follow at least a section of said cutting edge, permitting said cutting edge to obstruct each of the coolant jets from each of said shim channels belonging to each of said at least two outlet openings.

5. The milling tool according to claim 1, wherein an outlet opening of said second channel is shaped to follow at least a section of said cutting edge, permitting said cutting edge to obstruct a coolant jet from said second channel.

6. The milling tool according to claim 1, wherein said shim is configured and positioned to permit coolant to flow through said shim into said first channel and said second channel.

7. The milling tool according to claim 6, wherein a distribution channel is formed cooperatively by said shim and said holder, permitting coolant to flow from said base channel through said distribution channel into said first channel, and said axial portion extends at least partly through said distribution channel, permitting coolant to flow around said axial portion.

8. The milling tool according to claim 7, wherein said distribution channel is formed on parts of said shim by an open channel structure facing toward said holder.

9. The milling tool according to claim 1, wherein said holder includes a holder channel formed by said holder alone, and said holder channel is configured to direct coolant towards said insert top side from an outlet opening of said holder channel positioned above said insert top side.

10. The milling tool according to claim 1, wherein said axial portion includes a threaded part engaged with said holder beneath said shim.

11. The milling tool according to claim 1, wherein said second channel is configured to direct coolant towards said cutting edge, said cutting edge is formed at a top of a protrusion, and said protrusion protrudes at least as far out from said insert top side as said head portion.

12. A method of using a milling tool, the method comprising using the milling tool according to claim 1 for milling a workpiece.

13. The method according to claim 12, which further comprises using the milling tool for milling a workpiece made from a titanium-based alloy or stainless steel.

14. A milling process, comprising: providing a milling tool according to claim 1; providing a workpiece; and milling the workpiece with the milling tool.

15. The milling process according to claim 14, which further comprises providing a workpiece made from a titanium-based alloy or stainless steel as the workpiece.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic top view of a first embodiment of a milling tool according to the present disclosure;

(2) FIG. 2 is a schematic cross-sectional view along the line II-II of the milling tool embodiment depicted in FIG. 1;

(3) FIG. 3 is a schematic cross-sectional view along the line III-III of the milling tool embodiment depicted in FIG. 1;

(4) FIG. 4 is a schematic perspective detail top view of a holder comprised by the milling tool embodiment depicted in FIG. 1;

(5) FIG. 5a is a schematic perspective top view of a shim comprised by the milling tool embodiment depicted in FIG. 1;

(6) FIG. 5b is a schematic perspective bottom view of a shim comprised by the milling tool embodiment depicted in FIG. 1;

(7) FIG. 6a is an exploded perspective top view of a cutting insert, a fastener, a bushing and a shim comprised by the milling tool embodiment depicted in FIG. 1;

(8) FIG. 6b is an exploded perspective bottom view of a cutting insert, a fastener, a bushing and a shim comprised by the milling tool embodiment depicted in FIG. 1;

(9) FIG. 7a is an exploded perspective top view of a cutting insert, a fastener, a bushing and a shim comprised by a second embodiment of a milling tool according to the present disclosure; and

(10) FIG. 7b is an exploded perspective bottom view of the cutting insert, the fastener, the bushing and the shim comprised by the second embodiment of the milling tool.

DETAILED DESCRIPTION OF THE INVENTION

(11) Identical reference symbols in the figures denote identical or functionally identical components.

(12) Referring to FIGS. 1 to 3 there is shown a first embodiment of a milling tool 1 which comprises a cutting insert 2, a holder 3, a fastener 4 and a shim 5.

(13) The shim 5 is positioned between the cutting insert 2 and the holder 3. The fastener 4 extends through a through hole 20 of the cutting insert 2 and a through hole 50 of the shim 5 into the holder 3 beneath the shim 5.

(14) The fastener 4 has a fastening function and a coolant supply function.

(15) The fastening function of the fastener 4 is to secure the cutting insert 2 to the holder 3. The coolant supply function of the fastener 4 is to guide coolant cooperatively with the cutting insert 2 on parts of its through hole 20 onto an insert top side 21 of the cutting insert 2. Coolant flows along the insert top side 21 towards a cutting edge 22 of the cutting insert 2; the cutting edge 22 is formed on top of a protrusion of the insert top side 21, such that the cutting edge 22 can be described as a ridge.

(16) The shim 5 cooperates with the fastener 4 as the cutting insert 2 is pressed against the shim 5 when the fastener 4 is engaged with the holder 3 as depicted in FIG. 2, i.e. the shim 5 serves as a support for the cutting insert 2.

(17) At the same time the shim 5 has a coolant supply function.

(18) The coolant supply function of the shim 5 is to direct coolant towards a clearance side 27 of the cutting insert 2; the cutting edge 22 joins the clearance side 27 to the insert top side 21 and vice versa. The coolant supply to the clearance side 27 is realized by a channel 200 formed by the shim 5 alone and positioned such that the cutting insert 2 obstructs a coolant jet emerging from an opening 201 of the channel 200. The obstruction is especially revealed in FIG. 2 where it is shown that the cutting insert 2 partly overlaps the opening 201. Thereby a stream of coolant can flood the clearance side 27 from below.

(19) Referring to the fastening function of the fastener 4 a conical head portion 40 of the fastener 4 is disposed within the through hole 20 and abuts three insert abutment protrusions 23 of the cutting insert 2. The insert abutment protrusions 23 are spaced equally apart from each other in a peripheral direction around a central axis 24 of the through hole 20; the central axis 24 is also a central axis of the through hole 50.

(20) A cross-section of one of the three insert abutment protrusions 23 is depicted in FIG. 2. It is shown exemplarily in FIG. 2 for each of the insert abutment protrusions 23 that the insert abutment protrusions 23 are convex in a cross-section containing the axis 24.

(21) An axial portion 41 of the fastener 40 extends from the head portion 40 through the through hole 20 towards the holder 3.

(22) The axial portion 41 extends with regard to the cutting insert 2 contact-free through the cutting insert 2, unlike the head portion 40 which abuts the cutting insert 2 on the insert abutment protrusions 23.

(23) The axial portion 41 exits the through hole 20 at an insert bottom side 25 of the cutting insert 2. The insert bottom side 25 is shaped identically to the insert top side 21 rendering the cutting insert 2 thereby indexable.

(24) The axial portion 41 extends from the insert bottom side 25 into a bushing 6. The axial portion 41 has a not depicted threaded section extending along its axial extension. The axial portion 41 is engaged by its threaded section with a not depicted threaded section formed inside of the bushing 6. The bushing 6 extends into a hole 30 of the holder 3 where a threaded section formed on the outside of the bushing 6 is engaged with a threaded section of the holder 3 formed within the hole 30.

(25) The hole 30 is sealed against an environment of the milling tool 1 by a plug 70.

(26) The bushing 6 has a bushing abutment protrusion 61 extending entirely in a peripheral direction around the axis 24 which is a central axis for each of the bushing 6 and the hole 30. The bushing abutment protrusion 61 abuts a shim abutment protrusion 51 of the shim 5. The peripheral extension of the shim abutment protrusion 51 around the axis 24 is interrupted by a shim axial recess 52.

(27) When the bushing 6 is screwed into the hole 30 as depicted in FIG. 2, the shim 5 is pressed against the holder 3 by the engagement of the bushing abutment protrusion 61 with the shim abutment protrusion 51. Thereby a shim bottom side 53 of the shim 5 is pressed against a base side 31 of the holder 3.

(28) When the fastener 4 is screwed by its axial portion 41 into the bushing 6 as depicted in FIG. 2 the head portion 40 abuts each of the insert abutment protrusions 23 such that the cutting insert 2 is pressed against the shim 5. Thereby the insert bottom side 25 is pressed against a shim top side 54 of the shim 5.

(29) It will be appreciated that the fastening function of the fastener 4 can be realized without the bushing 6 as well by e.g. selecting a larger diameter of the axial portion 41 such that the axial portion 41 can be screwed directly into the hole 30.

(30) Referring to the coolant supply function of the fastener 4, the head portion 40 and the axial portion 41 form cooperatively with the cutting insert 2 a channel 100 within the through hole 20.

(31) The channel 100 is formed on parts of the cutting insert 2 by one of three insert recesses 26 (one of the recesses 26 is depicted in a cross-section in FIG. 2) and by the remainder of the through hole 20 below to the insert recesses 26 and where the axial portion 41 and the cutting insert 2 are contact-free with respect to each other within the through hole 20.

(32) The insert recesses 26 are spaced in a peripheral direction equally apart from each other about the axis 24. Thereby the insert abutment protrusions 23 are separated in a peripheral direction and equally from each other by the insert recesses 26.

(33) When viewed in a three-dimensional projection it is revealed that each insert recess 26 is shaped as a part of a funnel-type surface which slopes downwards from the insert top side 21.

(34) It will be appreciated that the entire cutting insert 2 and thereby the through hole 20 are mirror-symmetrical with respect to a mirror-plane oriented perpendicular to the axis 24 and intersecting the cutting insert 2 at a position where the diameter of the through hole 20 is smallest, i.e. at a distance halfway from the insert top side 21 to the insert bottom side 25 measured parallel to the axis 24.

(35) The channel 100 is in fluid communication with the shim axial recess 52.

(36) The shim axial recess 52 is in fluid communication with a distribution channel 55 formed cooperatively by the shim bottom side 53 and the base side 31. Thereby coolant can flow from the distribution channel 55 through the shim axial recess 52 into the channel 100 and out of an opening 101 of the channel 100 formed cooperatively by the insert top side 21 and a rim section 42 of the head portion 40.

(37) The rim section 42 is terminated by a plane top surface 43 of the fastener 4.

(38) Being plane and positioned below the cutting edge 22 in a cross section containing the axis 24 (FIG. 2) the top surface 43 and thereby the extension of the head portion 40 are reduced to a minor obstacle for the machined chips conducted along the insert 21 top side.

(39) Since the top surface 43 is positioned below the cutting edge 22 in a cross section containing the axis 24, the milling tool 1 has in its corresponding axial dimension along the axis 24 a compact design.

(40) The channel 200 is also in fluid communication with the distribution channel 55 as the channel 200 branches off the distribution channel 55 in a direction parallel to the axis 24.

(41) In FIG. 1 it is especially revealed that when viewed parallel along the axis 24 the cutting edge 22 crosses the opening 201. Thereby coolant emerging from the opening 201 can reach the part of the clearance side 27 directly adjacent to the cutting edge 22.

(42) FIG. 1 and FIG. 2 reveal together that the insert top side 21 has a depression 210, such that coolant emerging from the opening 101 can flow along a plane bottom surface 211 of the depression 210 and therefrom upwards along a facetted protrusion 212 of the insert top side 21 towards the cutting edge 22.

(43) As depicted in FIG. 1 the facetted protrusion 212 surrounds the top surface 43 completely along a peripheral direction about the axis 24.

(44) A major facet 213 of the facetted protrusion 212 is directly adjacent to the cutting edge 22 and serves as a primary rake surface for chip conduction.

(45) The cutting edge 22 is a major cutting edge of the cutting insert 2 and positioned in an active cutting position as apparent from FIG. 1.

(46) The cutting edge 22 is joined by a cutting corner 221 to a shorter minor cutting edge 22a which serves as an active wiper cutting edge during milling with the cutting edge 22. The cutting corner 221 becomes thereby active as well.

(47) The cutting edge 22 inclines from a cutting corner 220 downwards to the cutting corner 221.

(48) It will be appreciated that the cutting insert 2 has two further cutting edges 22 and 22 which are each designed analogously to the cutting edge 22, i.e. when being positioned each actively like the cutting edge 22 they cross the opening 201 to be cooled by coolant emerging from the opening 201.

(49) The cutting edge 22 has a minor cutting edge 22a, the cutting edge 22a a minor cutting edge 22a.

(50) When the fastener 4 is loosened or removed from the holder 3 the cutting insert 2 can be rotated around the axis 24 in steps of 120 such that the cutting edges 22 and 22a or 22 and 22a become cooperatively active. Each of the cutting edges 22 and 22 join the insert top side 21 to a clearance side designed analogously to the clearance side 27, i.e. the other clearance sides can be supplied each with coolant once the corresponding cutting edges 22 and 22 are positioned actively.

(51) It will further be appreciated that the cutting insert 2 has cutting edges identical to the cutting edges 22, 22a, 22, 22a, 22 and 22a, revealed by a view onto the insert bottom side 25 in a viewing direction parallel to the axis 24. Thus, when the insert bottom side 25 is turned upside the cutting edges associated with the insert bottom side 25 can be used similarly to the cutting edges 22, 22a, 22, 22a, 22 and 22a.

(52) Since the cutting edges 22, 22 and 22 and thereby the corresponding cutting edges of the insert bottom side 25 are each inclined, the surface area of the insert bottom side 25 available to be pressed against the base side 31 is reduced in comparison to a plane design of the insert bottom side 25. The shim 5, however, has its shim top side 54 configured for a plane matching with the insert bottom side 25; the same holds when the insert top side 21 is turned downside to face the shim 5. The shim 5 thereby enhances the mechanical stability of how the cutting insert 2 is secured by the fastener 4 to the holder 3.

(53) Referring to FIG. 3 (depicting in a cross-section containing the axis 24 the shim 5, the bushing 6 and the holder 3 without the cutting insert 2) the holder 3 has a base channel 32 which intersects the hole 30, such that the distribution channel 55 is in fluid communication with the base channel 32, i.e. coolant can flow from the base channel 32 into the distribution channel 55 an therefrom into each of the channel 100 and the channel 200.

(54) Referring to FIG. 4 (depicting the holder 3 in a perspective top view) an opening 32a of the base channel 32 intersects the hole 31 beneath the base side 31, such that the base channel 32 and the distribution channel 55 are in fluid communication.

(55) FIG. 4 reveals further that the base side 31 is essentially triangular and plane thereby matching the geometry of the shim 5 when viewed in a top view in a direction along the axis 24.

(56) FIG. 4 reveals also that the holder 3 comprises a holder channel 300 for coolant supply towards the insert top side 21 from an outlet opening 301 (which is positioned above the insert top side 21) of the holder channel 300, as apparent from FIG. 2 and FIG. 4 together. The coolant supply from the holder channel 300 flushes machined chips away from the cutting insert 2. The holder channel 300 is in fluid communication with the base channel 32.

(57) Referring to FIG. 5a (depicting the shim 5 in a perspective top view) the shim top side 54 has a central facet 56 intersected by the through hole 50 and the shim axial recess 52. The through hole 50 and the shim axial recess 52 form a cavity when the fastener 4 is engaged with the holder 3 as depicted in FIG. 2.

(58) The central facet 56 is a plane support surface for the cutting insert 2 when the fastener 4 is engaged with the holder 3 as depicted in FIG. 2. The central 56 facet is essentially triangular to fit into the depression 210 and the analogously shaped depression of the insert bottom side 25, depending on which of these sides faces the shim 5.

(59) The shim top side 54 has three outer facets 57, 58a and 58b, each directly adjacent to the central facet 56 and each inclined downwards from the central facet 56 towards the shim bottom side 53.

(60) The outer facets 57, 58a and 58b are each inclined to accommodate the inclined cutting edges of the cutting insert 2, i.e. when the insert top side 21 is turned downside, the cutting edges 22, 22 and 22 will be accommodated together with their associated minor cutting edges 22a, 22a and 22a by the shim 5.

(61) Where the outer facet 57 is intersected by the opening 201, the inclination of the opening 201 follows the inclination of the outer facet 57 and the opening 201 follows a straight outer edge 500 of the outer facet 57.

(62) FIG. 5a reveals further that the shim abutment protrusion 51 has a circular shape being interrupted by the shim axial recess 52 extending radially farther outwards.

(63) Referring to FIG. 5b (depicting the shim 5 in a perspective bottom view) the shim bottom side 53 is intersected by the through hole 50, a shim bottom recess 59 and the channel 200.

(64) Taking FIG. 5b and FIG. 2 together is it revealed that the shim bottom recess 59 and the base side 31 form cooperatively the distribution channel 55.

(65) The shim bottom recess 59 has an annular shape interrupted by the shim axial recess 52 and the channel 200. The annular shape of the shim bottom recess 59 allows for coolant to be spread out radially to create an excess of coolant to flow into each of the shim axial recess 52 and the channel 200.

(66) FIG. 6a shows in a perspective view partly two of the three insert recesses 26 which allow each for coolant flow within the through hole 20 between the fastener 4 and the cutting insert 2. FIG. 6a reveals especially the funnel-like shape of each of the insert recesses 26 exemplarily.

(67) FIG. 6a shows further partly two of the three insert abutment protrusions 23 against each of which the fastener 4 abuts, such that a sealing is obtained against coolant flow in the through hole 20 where the fastener 4 abuts the insert abutment protrusions 23.

(68) FIG. 6a and FIG. 6b show jointly the top-bottom symmetry of the cutting insert 2.

(69) FIGS. 1 to 6b depict together a milling tool 1 where the cutting insert 2 is supplied with coolant towards its insert top side 21 and, simultaneously, towards its clearance side 27. The former by the channel 100 and the latter by the channel 200 which are both internally supplied with coolant from the base channel 32 through the distribution channel 55; the channel 100 can also be referred to as a first channel 100 and the channel 200 as a second channel 200.

(70) Additionally, a chip evacuating coolant supply from the holder channel 300 is by the milling tool 1 realized.

(71) FIG. 7a and FIG. 7b show a second embodiment of a milling tool 1.

(72) The milling tool 1 differs from the milling tool 1 only to the extent that a shim 5 is used instead of the shim 5 and a cutting insert 2 is used instead of the cutting insert 2, i.e. especially the same type of double coolant supply and screw fastening is realized in each of the milling tools 1 and 1.

(73) The cutting insert 2 is essentially round with a circular cutting edge 22, an insert top side 21, an insert bottom side 25, a through hole 20, a clearance side 27 and gripping facets 27a. The gripping facets 27a allow for a precise rotation of the cutting insert 2, such that different parts of the cutting edge 22 can be used for cutting.

(74) Since the cutting edge 22 is round, i.e. void of corners, it has an increased stability against mechanical shock under milling.

(75) The insert recesses 26 described for the cutting insert 2 are also used for the cutting insert 2 to form a coolant channel analogously to the channel 100 for coolant supply to the cutting edge 22.

(76) The insert abutment 23 protrusions of the cutting insert 2 are used as abutments for the fastener 4, i.e. analogously to the insert abutment protrusions 23 of the cutting insert 2.

(77) The shim 5 is a circular plate with a plane shim top side 54 against which the plane insert bottom side 25 is pressed by the engagement of the fastener 4 with the cutting insert 2 and the not depicted holder 3.

(78) The bushing 6, being engaged with the fastener 4 as described for the milling tool 1, abuts the shim 5 analogously to abutting the shim 5.

(79) The shim 5 has bottom side 53 which is intersected by a through hole 50 and a shim bottom recess 59. The shim bottom recess 59 and the not depicted base side 31 form cooperatively a distribution channel analogously to the distribution channel 55.

(80) The shim bottom recess 59 has an annular shape interrupted by a shim axial recess 52. The annular shape of the shim bottom recess 59 allows for coolant to be spread out radially to create an excess of coolant to flow into the shim axial recess 52 and each of the channels 200; each of the channels 200 branches off the bottom recess 59 parallel to the axial extension of the fastener 4 and intersects the shim top side 54.

(81) Each of the channels 200 can supply coolant to the clearances side 27 out from circular outlet openings 201 (each outlet opening 201 belongs to one of the channels 200). Thereby the clearance side 22 can be cooled, especially where the clearance side 22 is joined to the insert top side 21 by the cutting edge 22, i.e. the cutting edge 22 can be cooled from below.

(82) The outlet openings 201 are spaced apart and positioned to follow the circular shape of the cutting edge 22 to provide the cutting edge 22 with coolant on parts of the clearance side 27, i.e. the outlet openings 201 follow a circle arc.

(83) FIGS. 7a and 7b depict together a milling tool 1 where the cutting insert 2 is supplied with coolant towards its insert top side 21 and, simultaneously, towards its clearance side 27. The former by a channel formed analogously to the channel 100 between the cutting insert 2 and the fastener 4, the latter by the plurality of channels 200 which are internally supplied with coolant from the base channel 32 through a distribution channel formed analogously to the distribution channel 55.