Cutting insert and cutting tool

CUTTING INSERT AND CUTTING TOOL

TOLD OF THE INVENTION

This invention relates to a cutting insert and a cutting tool 1 a־ metal cutting operations in general and for cutting small radius internal a meis in particular and also for ramp down cutting operations.

In these

BACKGROUND OF THE INVENTION

Such cutting tools, generally in the fbm of end mills and shell: □ills, are used in metal working applications in the manufacture of dies and molds i nd other structures having complex geometrical surfaces and extended shoulders, applications it is often required to produce internal comers of smal. radius, sometimes smaller than 0.5 mm. Generally, complex geometrical sur aces are produced in metal workpieces using ball nose end mills, or end mills w th round cutting inserts. There are no ball nose end mills having replaceable cuttii g inserts that can produce internal coiners having a radius as small as 0.5 ran. A so, there are no round cutting inserts having radii as small as 0.5mm.

When working a large surface of a workpiece, the most cc momical aptfsosfa, & to w ½0½ ksv&g large radii cutting inserts in order tc produce the main large scale features of the surface and then to use toeie hav! 3g sman radius cutting capability for producing small scale features and for red! icing the

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Cutting inserts having small radius cutting capability are usually rhomboidal in shape, having a cutting nose (or comer) with the required small radius. An example of such a cutting insert and associated cutting tool is c isclosed in EP 1 157 768 Al. ׳The cutting insert has a positive geometry and there! are only two cutting comers.

DE 28 11 086 Al discloses an indexable cutting insert for rotar ׳ ;milling machines, consisting of a parallelepiped-shaped body with a parallelogran !-shaped cross-section with two faces lying opposite each other, with two edge &Λ es lying between said faces and two front faces lying opposite each other, whereby the faces and the front faces intersect each other and form principal cutting edges, wherein the faces (11,12) and the edge faces intersect at an angle of less tom 90° 1 nd farm edges (17, 18), a part whereof forms an ancillary cutting edge, whr remaining part is provided in the form of a recess (21, 22), which is de: hold a clamping element, whereby each recess is made by means of smo!

(23,24), the extension whereof is limited by edges running parallel to the ancillary cutting edge.

It is an object of the present invention to provide a cutting insei t having four cutting comers capable of cutting small radii internal comers in a wc rkpiece. It is also an object of the present invention to provide a cutting tool such a s an end mill capable of seating such a cutting insert

It is a further object of the present invention to provide a cutti 1g insert and a cutting tool, of the aforementioned kind, that is also capable of can ying out ramp down cutting operations.

ignedto !th faces

SUMMARY OF THE INVENTION

Th$ insert 8754 ©f present invention are lesigned for cutting metals and composites. Typically, the cutting insert is manufai toed by form-pressing and sintering carbide powders. However, injection־ molding

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2004־24-11 teehniques can also be used.

In accordance with the present invention there is provided an indexable cutting insert, for use in a cutting tool for mflling operations, comprising:

two identical generally rhomboidal opposing end surfaces;

a peripheral side surface extending between the two opposing end surfaces, the peripheral side surface being perpendicular to a median plane of the cutting insert and comprising six component side surfaces, four of the component side surfaces being generally flat major side surfaces and two of the component side surfaces being diametrically opposing radiused comer side surfaces, each comer

ן side surface being located between and merging with the two major side surfaces;

two first cutting edges and two second cutting edges associated with each end surface, each first cutting edge forming a non-zero first angle with regpelt to the median plane and each second cutting edge forming a non-zero second atigle with respect to the median plane, the two first cutting edges associated with a given end surface being skew to each other and being located in associated major side surfaces that are parallel to each other, and the two second cutting edges associated with a given end surface being skew to each other and being located in associated major side surfaces that are parallel to each other;

two comer cutting edges associated with each end surface, each comer cutting edge merging with one first cutting edge and with one second cutting edge and forming therewith a continuous cutting edge section;

two opposing flat end regions, one flat end region associated with each end surface, the median plane being parallel to each flat end region;

a through bore extending between the flat end regions, the through bore having an axis defining an axial direction of the cutting insert, the flat end regions fanning axially outermost protruding regions of the cutting insert.

If desired, the is di Went from the second angle.

Further if desired, the first angle is equal to the second angle.

If desired, the peripheral side surface further comprises two

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Quite generally, the cutting insert has 180° rotational symmetry about each of first, second and third axes of rotational symmetry, the first axis being perpendicular to fixe flat end regions and coinciding with the axis of the through bore, the second axis passing through the minor side surfaces and the third axis passing through the comer side surfaces.

Preferably, each end surface comprises a rake surface associated with eash cutting edge section, the rake surface extending from the cutting edge section inwards towards the median plane.

Further preferably, the rake surface merges along a join with a rise that slopes upwardly ftom flte join away from, the median plane.

Yet further preferably, the rise associated with a given end surface extends from the join to the flat end region of the given end surface.

Also in accordance with the present invention there is provided a cutting tool for milling operations, the cutting tool having an axis of rotation A and comprising:

a plurality of indexable cutting inserts in accordance with the present invention, each cutting insert being seated in an insert pocket with an operative first cutting edge positioned at a given axial rake angle (γ).

Typically, the axial rake angle (γ) lies in the range of 0° to 5°.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding the invention will now be described, by way of example only, with reference to die accompanying drawings in which.

Fig1 ־ is a perspective view of a cutting insert in accordance with the present invKOtioE;

Fig. 2 is an end view of the cutting insert shown in Fig. 1;

Fig3 ־ is a side view of the cutting insert shown in Fig. 1;

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Fig. 4 is another side view of the cutting insert shown in Fig. 1;

Fig. 5A is a partial cross-sectional view of the cutting insert gb™!™ jn Fig. 2 taken along the line VA-VA;

Fig. SB is a partial cross-sectional view of the cutting insert shown in Fig. 2 5 taken along the line VB-VB;

¾. 5C is a partial cross-sectional view of the cutting insert shown in Fig. 2 taken along the line VC-VC;

Fig. 5D is a partial cross-sectional view of the cutting insert shown in Fig. 2 taken along the line VD-VD; and

Figo 6 is a side view of a cutting tool in accordance with the present invention

DETAILED DESCRIPTION OF THE INVENTION

Attention is first drawn to Figs. 1 to 4 showing an indexable «rfting insert 10 in accordance with the present invention. The cutting insert 10 has two 15 identical generally rhomboidal opposing end surfaces 12 with a peripheral side surface 14 extending therebetween. Each end surface 12 is bounded by a peripheral edge 16 at which the end surface 12 and the peripheral side surface 14 merge. Each peripheral edge 16 comprises two continuous cutting edge sections 18 separated by two non-cutting edge sections 20- Adjacent each cutting edge section 20 18 is a groove 22 which borders a generally flat end region 24 of the end surface

12. Therefore, the cutting insert 10 has two opposing flat end regions 24. The two opposing flat end regions 24 are parallel to each other and to a median plane M of the cutting insert 10 which is located midway between the flat end regions 24.

The peripheral side surface 14 is perpendicular to the median plane M 25 and comprises eight component side surfaces, namely, four generally flat major side surfaces 26, two diametrically opposing radiused comer side surfeces 28 and two diametrical surfece 30 is located between and merges with the two major side surfaces 26. Similarly, each comer side surflice 28 is located between and merges with the two

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Each cutting edge section 18 comprises a first cutting edge 32, a second cutting edge 34 and a comer cutting edge 36 at which the first and second cutting edges 32, 34 merge. Each first cutting edge 32 extends away from the comer 5 cutting edge 36 with which it merges to an adjacent non-cutting edge section 20 and towards the median plane M. The first cutting edge 32 is preferably straight and is inclined at a non-zero first angle 01 with respect to the median plane M. Similarly, each second cutting edge 34 extends away from the comer cutting *dg* 36 with which it merges to an adjacent nan-cutting edge section 20 and towards the 10 median plane M. The second cutting edge 34 is preferably straight and is inclined at a non-zero second angle 02 with respect to the median plane M. The first and second angles 81, Θ2 can be equal or non-equal to each other.[The two first edges 32 associated with a given end surface 12 being skew to each other and being located in associated major side surfaces 26 that are parallel to each other, and the 15 two second cutting edges 34 associated with a given end surface 12 being skew to each other and being located in associated major side surfaces 26 that are parallel to each otherj The flat minor side surfaces 30 form a pair of diametrically opposed flat comers of the cutting insert 10.

Each end surface 12 comprises a rake surface 38 adjacent each cutting 20 edge section 18. The rake surface 38 extends from the cutting edge section 18 inwards towards the median plane M to a join 40 where it merges with a rise 42 that slopes from the join 40 away from the median plane M to the flat end region

24. As can be seen in Figs. 2 and 5A to 5D, the rake surface 38 adjacent the first cutting edge 32 has a variable length (measured peipendicular to the first cutting 25 edge 32) along the cutting edge. It has a first length LI (at cross-section VA-VA) near to an adjacent non-cutting edge 20 and a second length L2 (at cross-section VB-VB) near to an adjacent comer ־tMngMg,«,^ ie greater than the first length Ll and continuously varies between these two values along the cutting edge. On the other hand, the rake surface 38 adjacent with the

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2004־11־24 second cutting edge 34 has a third length L3 which is approximately constant along die length of the second cutting edge 34. For the sake of clarity it is pointed out that the line shown as the join 40 in Figs. 1 and 2 is only illustrative. It will be apparent from Figs. 5A to 5D that the join 40 is actually a curved region of finite width forming part of the groove 22.

The cutting insert 10 has 180° rotational symmetry about first «econd and third axes of rotational symmetry Rl, R2, R3. The first axis Rl is perpendicular to the flat end regions 24, the second axis R2 passes through the minor side surfaces 30 and the third axis R3 passes through the coiner side arfaces 28. The second and third axes R2, R3 lie in the median plane M and the first axis Rl is perpendicular to the second and third axes R2, R3. The ending insert 10 is provided with a through bore 44 having as axis lhe first axis of rotational gymnwhy Rl. The through bore 44 extends between the flat end regions 24 and defines an axial direction of the cutting insert It should be noted from the side views of the cutting insert 10 in Figs. 3 and 4 that the cutting insert 10 is widest in the ayiat direction of the cutting insert 10 at regions where the flat end regions 24 are directly opposite each other. In other words, die flat end regions 24 fann axially outermost protruding regions of the cutting insert 10. Typically, the rading r of the comer catting edges 36 is in the range 0.2 to 635 mm.

Attention is now drawn to Fig. 6 showing a cutting tool 46 in accordance with the present invention. The cutting tool 46 is an end mill capable of cutting small radii internal comers in a workpiece 48 in accordance with the value of the radius R of the comer cutting edges 36. The cutting tool 46 is also capable performing ramp down cutting operations by means of the cutting edge 34. The cutting tool 46 has an axis of rotation A and coinprises a cutter body 50 with the indexable cutting inserts 10 in accordance with the present invention seated in insert pockets 52 of the cutter bMy so, BM)i MsSng insert M) has t»0 effective operative cutting edges, one operative first cutting edge 32’ and one operative second cutting edge 34’, and one operative comer cutting edge 36’. The

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1ns« pockets 52 etc 50 designed that ftecperadv־ ft״ posiBoned with ־nd axial rake angle γ of cJqs־ to fl־ larger that 5». Since the eperative ftst cutting edge 32’ makes a an£t. M respect to the median plane M of the cutting insert 10 an inherent back clearance a 5 typically dose to 01 but generally no less ftan β1.5־ » obtained between the cuttmg msert 10 and portions of the surface of ft־ workpiece 48 adjacent ft־ operative second cutting edge 34*.

!^ס׳מומס?0־ first cutting edge 32'can be divided into a leading portion adjacent the operate־ cutting comer 3«', a trailing portion distal the operative 10 cuttmg comer 36׳ and an intermedia:־ portion therebetween, ft cutting operations ™,0^111®*'1®!®0^11®tio'iofintemal small radius comers in a workpiece, such as in 111®1111^®11®5311®*^0®׳fiarolfis» it is mainly fte operative cutting comer 36׳ that is involved m the cutting operation. It win be appreciated that even if ft־־! ־ding pornon Of the oporative ftst cutting edge 32׳ also participates j, ΦΜ»», th־ groove 22 should extend adjacent ftc whole !־ngft tfae first cuttmg edge 32׳ font ft־ leading portion to trailing portion, in order to provide clearance between the end sura12 ־־ adjacent the trailing portion of the operative first cuttmg edge 32׳ and the workpiece 48. It win ־!so be appreciated that if instead of the flat mmor side surfaces 30 the ettrting ־user: were t־ hav־ cotnns beyond the flat minor side surfaces 30, then that part of the cutting insert ’’”’1™^“®*’Fyoud the flat minor side surfaces 30 associated with the operative first edge 32׳ would drsadvmtageously enter the cutting circle defined by ftc operative first cutting edge 32*. This ט esoeciaHv t

4־ is especially important when woxkme in 16®“η of ®tended shoulders and alsoinrampi^i cutting operations.

the present invention has been described to a certain degree of “ t““ '^!000 *“ dteraiMS - modifications ־־m Claimed. ®ה«׳זי׳ו Bhareesfler