IL181562A - High-performance end mill - Google Patents

Description

111111 lllllill ill 562 p'Ti I 453572 IMPROVED END MILL The present invention relates to tools for the machining of materials by milling.

More particularly, the invention provides an improved form for a rotary cutting tool such as an end-mill, configured to reduce vibrations, allow higher rates of metal removal while yet extending tool life.

Even more particularly the invention relates to an end mill cutter which comprises a body having multi cutting edges, and a shank part. Each cutting part has an end face cutting part and a peripheral cutting part. The end face cutting edge comprises axial (peripheral), corner and radial (forehead) cutting edges.

In the present application the terms end-mill, cutter and tool are used interchangeably.

End-mills are widely used in milling operations due to their versatile range of application and due to the moderate first cost of the tool. End-mills are often of cylindrical shape, and are available up to about 80 mm diameter. Many end mills have flat ends; however other shapes such as conical and rounded ends are also used. An end-mill typically has 2 to 10 teeth, depending on diameter size and whether the tool is intended for rough cutting or finishing. Side teeth are usually of spiral shape, but can be straight parallel to the axis. Material of construction is high speed steel, solid carbide, cermet or ceramic, or combinations thereof.

End mills, as the name implies have a set of cutting teeth at the end face, the number of end teeth being equal to the number of side teeth. In order to form teeth at the cutter end face the cutter during manufacture is subjected to what are known as gash cuts. The gash cut is a shaped form which extends from near the center of the cutter to the outer diameter of the end mill. The gash cuts are disposed about 30 - 80 degrees relative the tool axis, and form the rake angle of the end cutting teeth. An appropriate relief angle is ground to complete the form of the end teeth.

The form of a prior-art gash cut typically has a flat bottom, curved lower corners and spreads outwards to form the rake angle of a first end tooth and the lower portion of the relief face of a second adjacent tooth. The maximum depth of the gash cut, when 181562/2 3 measured from the end face of the tool in an axial direction is usually about 0.3D, where D is the outer diameter of the cutter.

While large numbers of the US Patents deal with other aspects of end mills, surprisingly no document was found which relates to the form of the end teeth of the cutter.

JP 2006-000985 discloses an endmill that has a plurality of helicoidal chip removal grooves formed on the outer periphery on the tip end side of a tool body. Gashes forming the rake surfaces of the respective end cutting edges are arranged so as to be connected with the tip end portions of the chip removal grooves arranged in the axial direction of the tool body. The gashes are formed, in side view, such that the groove widths gradually increase with depth in the axial direction of the tool body.

It is therefore one of the objects of the present invention to provide an improved end tooth form which will allow higher rates of metal removal, provide longer tool life and reduce vibrations and generated noise.

A further object of the present invention is to provide an improved end tooth having a positive or negative radial angle.

The present invention achieves the above objects by providing a high-performance end mill comprising a shank portion and at least one cutting portion divided into a plurality of teeth by flutes disposed between said teeth, the radial teeth at the cutter extremity each having a cutting edge extending outwardly from the center of the tool's extremity and a gash cut profile wherein the maximum axial depth of said gash cut measured in the direction parallel to the cutter axis is less than 0.15D where D is the outer diameter of the cutter. 181562/1 3a In a preferred embodiment of the present invention there is provided a high-performance end mill wherein the maximum axial depth of said gash cuts measured in the direction parallel to the cutter axis is 0.1 D.

The tool designer is always in a quandary attempting to balance the conflicting demands of improved tool strength and rigidity and the need for chip clearance. The cutting process is complex and is a function of many variables such as machine power and rigidity, coolant fluid, rigidity of work support, material being machined, speed, feed and of course the tool geometry. Thus it is probable that computer modeling if carried out would not provide a reliable result. Accordingly, a prototype cutter was manufactured and tested, and the expected improvements in machining were indeed realized.

It may well be thought that the reduction in the depth of the gash slots as disclosed in the present invention will lead to problems regarding chip clearance. However, this view fails to consider the large flutes between the teeth at the side of the cutter. These flutes extend to the cutter extremity and provide adequate chip clearance also for the teeth disposed at the cutter end face.

The radial cutting edges on the forehead part are lying on geometric lines which do not intersect with the tool's center so that the cutting edges are located with a certain radial angle relative to the tool's radius axis. The radial angle could have positive, negative or zero value.

The tool's end face comprises the cutting edges and relief surfaces. The cutting edges are formed by certain grooves when depth, angles and width of the groove depend on the end face relief surfaces clearance angles.

The end face grooves - gash slots, form the forehead cutting edges also forms a corner and part of the peripheral cutting edges. The axial angle of the end face cutting edges on the corner and the peripheral part corresponds to the spiral angle of the tool's peripheral cutting edges; so that the tool and the work piece shape distortion is minimal.

The end face cutting edge is optionally of a geometric shape and can include radius or chamfer on the comer parts. In this case, the axial height of the radius or chamfer should be smaller than axial height of the end face cutting edges on the comer and peripheral parts so that the intersection of spiral peripheral cutting edges and end face cutting edges forms only one refraction point. In the case of having similar peripheral cutting edges spiral angle and end face cutting edges axial angle the cutting edges intersection will not form the refraction point at all.

It will thus be realized mat the novel end mill of the present invention achieves significantly improved machining when the end face of the cutter is in use. The improved support at the back of the tooth makes possible higher loads and greatly reduces tooth vibration and noise.

The invention will now be described further with reference to the accompanying drawings, which represent by example preferred embodiments of the invention. Structural details are shown only as far as necessary for a fundamental understanding thereof. The described examples, together with the drawings, will make apparent to those skilled in the art how further forms of the invention may be realized.

In the drawings: FIG. 1 is an enlarged elevational view an extremity of a cutter showing a gash cut as known in the prior art; FIG. 2 is an enlarged plan view of the extremity of the same cutter showing the end teeth as known in the prior art; FIG. 3 is an enlarged elevational view of an extremity of a cutter showing a gash cut according to the invention; FIG. 4 is an enlarged plan view of an extremity of a cutter showing the end teeth of the cutter illustrated in FIG. 3, having a positive radial angle; and FIG. 5 is an enlarged plan view of an extremity of a cutter showing the end teeth of the cutter seen in FIG. 3, having a negative radial angle.

There is seen in FIG. 1 an enlarged extremity 10 of a prior-art spiral 5-tooth end mill. The form of a prior-art gash cut 12 seen has a flat bottom 14, curved lower corners 16 and spreads outwards on a first side 18 to form the rake angle of a first end tooth 20. The remaining side 19 of the gash cut 12 forms the lower portion of the relief face of a second adjacent tooth 22. The depth of the gash cut 12, when measured from the end face 24 of the tool in a direction parallel to the central axis of the tool is 0.3D. Obviously, such a deep cut weakens the tooth 20. The figure also shows a small rake angle A resulting from the gash cut 12.

With reference to the rest of the figures, similar reference numerals have been used to identify similar parts.

Referring now to FIG. 2, there is seen the same extremity 10 prior-art end mill showing the formation of the end teeth 20, 22. All five teeth are of the same length, and appear on the illustration differently due to the each tooth facing a different angle. 181562/2 6 It is to be noted that the cutting edge 1 1 of all five of the teeth meet at the center 13 of the tool.

FIG. 3 illustrates a high-performance end mill 26 according to the present invention wherein the gash cut profile 28 is a substantially large diameter curve extending to less than half the depth of that seen in the prior-art cutter 10.

Seen in FIG. 4 is a further view of the same embodiment of the tool 26 according to the invention, having a positive radial angle.

As can be seen the end cutting edge 34 extends outwards from the center 13 of the tool having a positive radial angle P. Unless the cutter 26 is only used axially, (as a drill) which is rare, in normal use the cutter advances at right angles to its axis, the lack of teeth in the center portion 36 caused by the shallower gash profile.

Seen in FIG. 5 is a further view of an embodiment of tool 26, wherein the radial angle of the cutting edge is negative N.

The scope of the described invention is intended to include all embodiments coming within the meaning of the following claims. The foregoing examples illustrate useful forms of the invention, but are not to be considered as limiting its scope, as those skilled in the art will be aware that additional variants and modifications of the invention can readily be formulated without departing from the meaning of the following claims.

Material which is outside the scope of the claims does not constitute part of the claimed invention.

Claims (8)

7 181562/2 WE CLAIM:

1. A high-performance end mill comprising a shank portion and at least one cutting portion divided into a plurality of teeth by flutes disposed between said teeth, the radial teeth at the cutter extremity each having a cutting edge extending outwardly form the centre of the tool's extremity and a gash cut profile wherein the maximum axial depth of said gash cut measured in the direction parallel to the cutter axis is less than 0.15D where D is the outer diameter of the cutter.

2. The high-performance end mill as claimed in claim 1, wherein the radial teeth at the cutter extremity each having a cutting edge extending outwardly from the center of the tool's extremity in positive direction.

3. The high-performance end mill as claimed in claim 1, wherein the radial teeth at the cutter extremity each having a cutting edge extending outwardly from the center of the tool's extremity in negative direction.

4. The high-performance enc mill as claimed in claim 1, wherein the maximum axial depth of said gash cuts measured in the direction parallel to the cutter axis is 0.1D.

5. The high-performance end mill as claimed in claim 1, wherein the geometric shape can include radius or chamfer on the corner parts the axial height of the radius or chamfer should be smaller than axial height of the end face cutting edges on the corner and peripheral parts so that the intersection of spiral peripheral cutting edges and end face cutting edges form only one refraction point.

6. The high-performance end mill as claimed in claim 1, wherein the intersection of spiral peripheral cutting edges and end face cutting edges forms being without refraction point.

7. The high-performance end mill as claimed in claim 1, wherein each cutting part has an end face cutting part and a peripheral cutting part, said end face cutting edge comprises corner cutting edge - radial, chamfered or others and radial cutting edge. 181562/3 8

8. A high-performance end mill according to any one of claims 1-7 as illustrated in any of the drawings.