Ceramic face mill with circular arc profile for machining Inconel

Abstract

A face mill includes a circular arc profile and is configured for machining Inconel. In particular the cutting portion is made of a ceramic material, and has an axial sub-edge with a positive axial rake angle to increase tool life.

Claims

1. A ceramic face mill for machining an Inconel work piece, the face mill configured for rotating about a central rotation axis A.sub.R defining opposite axially forward and rearward directions D.sub.F, D.sub.R, and opposite rotational cutting and succeeding directions D.sub.P, D.sub.S, the face mill comprising: a shank portion; and a cutting portion extending forward from the shank portion to a cutting end face; the cutting portion comprising: an effective cutting length L.sub.E; a diameter D.sub.E located at the cutting end face; a plurality of teeth; and a gash located between each pair of adjacent teeth of the plurality of teeth; a tooth of the plurality of teeth comprising: a rake surface; a relief surface; and a cutting edge formed at an intersection of the rake and relief surfaces; the cutting edge comprising: an axial sub-edge located at the cutting end face; a radial sub-edge located along a periphery of the cutting portion; and a corner sub-edge extending from the axial sub-edge to the radial sub-edge and defining a corner radius R.sub.C; wherein the entire face mill: is made of a ceramic material; and has a unitary monolithic construction; and wherein the entire axial sub-edge has a positive axial rake angle .

2. The ceramic face mill according to claim 1, wherein a maximum axial rake angle 1 of the axial sub-edge has a value which fulfills the condition: 115.

3. The ceramic face mill according to claim 1, wherein at least a portion of the corner sub-edge, adjacent to the one axial sub-edge, has a positive corner rake angle .

4. The ceramic face mill according to claim 3, wherein the entire corner sub-edge has a positive corner rake angle .

5. The ceramic face mill according to claim 3, wherein a minimum positive corner rake angle 1 of the corner sub-edge and a maximum axial rake angle 1 of the axial sub-edge fulfill the condition: 1<1.

6. The ceramic face mill according to claim 3, wherein the corner rake angle gradually reduces with increasing proximity to the radial sub-edge.

7. The ceramic face mill according to claim 1, wherein each gash between each pair of adjacent teeth is the only gash between said pair of teeth.

8. The ceramic face mill according to claim 1, wherein each gash between each pair of adjacent teeth extends rearwardly to a gash end, the gash end exiting to a peripheral surface of the cutting portion.

9. The ceramic face mill according to claim 8, wherein an axial length L.sub.A of at least one of said gashes can be measurable from the cutting end face to the gash end thereof, the axial length L.sub.A fulfilling the condition: L.sub.A<D.sub.E.

10. The ceramic face mill according to claim 9, wherein the axial length L.sub.A fulfills the condition: L.sub.A<2R.sub.C.

11. The ceramic face mill according to claim 1, wherein the plurality of teeth is equal to or greater than five teeth.

12. The ceramic face mill according to claim 11, wherein the plurality of teeth is equal to or less than 11 teeth.

13. The ceramic face mill according to claim 12, wherein the plurality of teeth is equal to 5, 7 or 9 teeth.

14. The ceramic face mill according to claim 1, wherein at least one tooth of the plurality of teeth is positioned front-of-center.

15. The ceramic face mill according to claim 1, further being devoid of a coolant channel.

16. The ceramic face mill according to claim 1, wherein, in an end view of the cutting end face, the ceramic face mill is rotationally symmetric by 360 divided by the number of teeth.

17. The ceramic face mill according to claim 1, being made of a SiAlON composite.

18. The ceramic face mill according to claim 1, wherein at least one rake surface is curved.

19. The ceramic face mill according to claim 1, wherein at least one entire cutting edge is curved in an end view of the cutting end face.

20. A method of machining an Inconel work piece, comprising: providing the ceramic face mill according to claim 1, and face milling the Inconel work piece at a speed greater than 300 m/min and for a length of time sufficient to transform the initially positive axial rake angle, by wear, to a negative axial rake angle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a better understanding of the subject matter of the present application, and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which:

(2) FIG. 1 is a perspective view of an example face mill according to the subject matter of the present application;

(3) FIG. 2 is a side view of the face mill in FIG. 1;

(4) FIG. 3 is an enlarged side view of a cutting portion of the face mill in FIGS. 1 and 2;

(5) FIG. 4 is an end view of a cutting end face of the cutting portion in FIG. 3;

(6) FIG. 5 is a cross-section view taken along line V in FIG. 3;

(7) FIG. 6 is a cross-section view taken along line VI in FIG. 3; and

(8) FIG. 7 is a cross-section view taken along line VII in FIG. 4.

DETAILED DESCRIPTION

(9) FIGS. 1 and 2 illustrate a face mill 10 configured for rotating about a central rotation axis A.sub.R which extends longitudinally through the center thereof.

(10) The central rotation axis A.sub.R defines opposite axially forward and rearward directions D.sub.F, D.sub.R, and opposite rotational preceding and succeeding directions D.sub.P, D.sub.S, the preceding direction D.sub.P being the cutting direction.

(11) The face mill 10 comprises a shank portion 12 and a cutting portion 14 extending forward (i.e., in the forward direction D.sub.F) therefrom.

(12) The shank portion can have a shank portion length L.sub.S.

(13) The shank portion 12 can have a basic cylindrical shape. The entire shank portion 12 can be cylindrical (i.e. without grooves or recesses).

(14) The cutting portion 14 extends in the rearward direction D.sub.R from a cutting end face 16 to a neck portion 18. More precisely, the cutting portion 14 can be considered to extend to a neck intersection 20 with the shank portion 12, the neck intersection 20 being defined as the axial location where the neck portion 18 starts to reduce in diameter in the forward direction D.sub.F from the shank portion 12.

(15) It will be understood that the neck portion 14 is optional and that cutting portion 14 should be considered the portion of the face mill 10 which extends forward of the shank portion 12, the shank portion 12 being identifiable as the portion which is configured to be gripped by a collet or chuck, as is known in the art per see.

(16) The cutting portion 14 can have an overall cutting portion length L.sub.C. The cutting portion length L.sub.C in this example extends from the cutting end face 16 to the end of a neck portion 18, or more precisely to the neck intersection 20 thereof.

(17) The cutting portion 14 is made of a ceramic material. Specifically, it can be made of a SiAlON composite. More specifically it can be the SiAlON composite marketed under the trade name TC3030.

(18) The cutting portion 14 and the shank portion 12 are, preferably, integrally formed, or stated differently the entire face mill 10 has a unitary monolithic construction. Accordingly, the entire face mill 10 in this example, including the shank portion 12, is made of the same ceramic material.

(19) The cutting portion 14 is integrally formed with a plurality of teeth 20. For example, the plurality of teeth 20 can comprise first, second, third, fourth, fifth, sixth and seventh teeth 20A, 20B, 20C, 20D, 20E, 20F, 20G. As shown from their unbroken appearance, the teeth 20 are non-serrated.

(20) A diameter D.sub.E of the face mill 10 is shown at the cutting end face 16. It will be understood that the diameter D.sub.E at the cutting end face 16 is the widest point between the teeth 20 which is, more precisely stated, slightly rearward of the forward most edge of the face mill 10, yet which is known to constitute the diameter D.sub.E as measured in the art per see.

(21) The plurality of teeth 20 are alternated with a plurality of gashes 22. For example, the plurality of gashes 22 are formed as blended gashes and can comprise first, second, third, fourth, fifth, sixth and seventh gashes 22A, 22B, 22C, 22D, 22E, 22F, 22G.

(22) Referring to FIG. 2, each gash 22 differs from a helical flute in that it does not need to extend helically. It can be a straight gash (i.e. it can extend along an axis), and can extend at a gash angle formed with the central rotation axis A.sub.R. The gash angle can preferably be 425, such slanted angle assisting with production of the teeth while not requiring a further flute manufacturing step.

(23) While it is indeed feasible to continue the gash in a rearward direction (i.e. generally towards the shank portion 12) in a straight or helical path, it is preferred to minimize the length of the gashes 22 due to the relatively high cost of grinding ceramic.

(24) Each gash 22 becomes more shallow until it reaches a peripheral surface 24 of the cutting portion 14 at a gash end 26. An axial length L.sub.A is measurable from the cutting end face 16 to the gash end 26.

(25) Each tooth 20 in the present example is identical, and equally circumferentially spaced, accordingly the following description of each element is applicable to each of the teeth 20, and characters or arrows directed to different teeth for different elements is merely due to those elements being better shown on a particular tooth in a given view.

(26) Drawing attention also to FIG. 3, each tooth 20 can comprise a rake surface 28, a relief surface 30, and a cutting edge 32 formed at an intersection of the rake and relief surfaces 28, 30.

(27) While in the two-dimensional line-drawings provided, it is difficult to see the curvature of the rake surfaces 28, it will be understood that the rake surfaces are indeed curved or, stated differently, concavely-shaped. Indeed, while the rake surface 28 of the fifth tooth 20E (i.e. at the left side of FIG. 3) appears planar and parallel with the central rotation axis A.sub.R, it is understood from viewing the other teeth 20, in particular the sixth tooth 20F, that the teeth 20 are not parallel with the central rotation axis A.sub.R but are forwardly slanted and the rake surfaces thereof are curved.

(28) For the purposes of explanation, the rake surface 28 of the fifth tooth 20E in the view shown in FIG. 3 should be considered to be shown in a profile view.

(29) The cutting edge 32 comprises an axial sub-edge 32A located at the cutting end face 16, a radial sub-edge 32B located along a periphery of the cutting portion 14 and a corner sub-edge 32C extending from the axial sub-edge 32A to the radial sub-edge 32B and defining a corner radius R.sub.C.

(30) The corner sub-edge 32C provides a circular arc profile, which during rotation is used to define an imaginary circle I.sub.C.

(31) The imaginary circle I.sub.C defines a circle center point C.sub.P, axial and radial tangent lines L.sub.AT, L.sub.RT, axial and radial tangent points P.sub.AT, P.sub.RT and a radius magnitude corresponding to the corner radius R.sub.C.

(32) The axial tangent line L.sub.AT extends forwardly from the circle center point C.sub.P and in a direction parallel with the central rotation axis A.sub.R.

(33) The axial tangent point P.sub.AT is located at an intersection of the circle I.sub.C and the axial tangent line L.sub.AT.

(34) The radial tangent line L.sub.RT extends from the circle center point C.sub.P in a radially outward direction which is perpendicular with the central rotation axis A.sub.R.

(35) The radial tangent point P.sub.RT is located at an intersection of the circle I.sub.C and the radial tangent line L.sub.RT.

(36) As shown in FIG. 2, the axial length L.sub.A is smaller than the diameter D.sub.E.

(37) By contrast, in FIG. 3, it is shown that the axial length L.sub.A is larger than an effective cutting length L.sub.E. The effective cutting length L.sub.E can be measurable from the cutting end face 16 to a point 36 which is a rearmost portion of the cutting edge 32.

(38) The effective cutting length L.sub.E is larger than a recommended machining depth L.sub.D. The recommended machining depth L.sub.D of the face mill 10 can be measurable from the cutting end face 16 to a point 38 along the corner sub-edge 32C (i.e. closer to the cutting end face 16 than the radial tangent point P.sub.RT. It will be understood that machining with a portion of the cutting edge 32 located at the radial tangent point P.sub.RT, or further from the cutting end face 16 than the radial tangent point P.sub.RT, will produce radial forces, which are comparatively detrimental for a relatively brittle ceramic face mill 10 operating at extremely high speeds and is thus preferably avoided.

(39) Referring to FIG. 4, the teeth 20 are each positioned front-of-center as shown. To elaborate what is meant by front-of-center, a first radial line L.sub.R1 can be drawn from the central rotation axis A.sub.R to intersect a start point 34 of an axial sub-edge 32A, in this example of the fourth tooth 20D. Since every point of the entire cutting edge 32 is located behind the radial line L.sub.R1 (i.e. in the succeeding direction D.sub.S), when the material being machined (not shown) contacts any portion of the cutting edge 32, there is always some force component in an outward radial direction D.sub.O assisting to eject the material being machined (or chip outwardly, i.e. away from the face mill 10.

(40) Additionally, since the entire cutting edge 32 is formed with a single gash, and is entirely curved in the end view shown in FIG. 4, a more smooth cutting operation is believed to be achieved.

(41) As shown in FIG. 3, a random cross section has been selected which extends through the radial sub-edge 32B, and in FIG. 5 is used to exemplify what is meant by a negative radial rake angle . To elaborate, the cross section is perpendicular to the central rotation axis A.sub.R.

(42) The radial rake angle is measurable between a second radial line L.sub.R2 extending radially from the central rotation axis A.sub.R to intersect the radial sub-edge 32B of the first tooth 20A, and a first tangent line L.sub.T1 extending tangentially from the associated rake surface 28, or more precisely an intersection of the associated rake surface 28 and the radial sub-edge 32B. The radial rake angle formed can be understood to be a negative angle if the first tangent line L.sub.T1 extends behind second radial line L.sub.R2 in an outward direction (i.e. with increasing distance from the central rotation axis A.sub.R). Stated differently, a negative radial rake angle is formed when the first tangent line L.sub.T1 is located further in the succeeding direction D.sub.S than the second radial line L.sub.R2.

(43) As shown on the right side of FIG. 3, a random cross section (in this example, along a bisector line L.sub.B which is at a 45 angle with the central rotation axis A.sub.R in this non-limiting example) has been selected which extends through the corner sub-edge 32C of the first tooth 20A, and in FIG. 6 is used to exemplify what is meant by a positive corner rake angle .

(44) The corner rake angle is measurable between the bisector line L.sub.B extending from the central rotation axis A.sub.R to intersect the corner sub-edge 32C and a second tangent line L.sub.T2 extending tangentially from the associated rake surface 28, or more precisely an intersection of the associated rake surface 28 and the corner sub-edge 32C. The corner rake angle formed can be understood to be a positive angle if the second tangent line L.sub.T2 extends forward of the bisector line L.sub.B. Stated differently, a positive angle is formed when the second tangent line L.sub.T2 (in an outward direction) is located further in the preceding direction D.sub.P than the bisector line L.sub.B.

(45) As shown on the right side of FIG. 4, a random cross section has been selected which extends through the axial sub-edge 32C of the first tooth 20A, and in FIG. 7 is used to exemplify what is meant by a positive axial rake angle . To elaborate, the cross section is in a plane parallel to the central rotation axis A.sub.R.

(46) The axial rake angle is measurable between an axial line L.sub.X extending parallel to the central rotation axis A.sub.R and a third tangent line L.sub.T3 extending tangentially from the associated rake surface 28, or more precisely an intersection of the associated rake surface 28 and the axial sub-edge 32C. The axial rake angle formed can be understood to be a positive angle if the third tangent line L.sub.T3 extends forward of the axial line L.sub.X. Stated differently, a positive angle is formed when the third tangent line L.sub.T3 (in an outward direction) is located further in the preceding direction D.sub.P than the axial line L.sub.X.