DE10325600A1 - Router bit, comprising outer cutting areas arranged in slightly asymmetrical shape for reduction of oscillatory motion - Google Patents

Abstract

The bit (1) is made of hard metal suitable for use on a particularly firm material like chilled cast iron. It is provided with four cutting areas arranged across the tip and four lateral cutting areas (4a, 4b, 4c, 4d) guided in spirals along the outer surface (10) of the shaft. The lateral cutting areas (4a, 4b, 4c, 4d) are distributed around the shaft in a slightly asymmetrical way. If an oscillation is created by individual cutting edges (4a, 4b, 4c, 4d), it is compensated by the position of the remaining cutting areas (4a, 4b, 4c, 4d) .

Description

The invention relates to an end mill, in particular a carbide end mill, with at least two front cutters arranged on one end face and peripheral cutters adjoining each end face. Such an end mill is for example from the DE 101 53 005 A1 known.

One End mills is usually both for slot milling as well as for side surface processing usable. Especially when drilling and / or slot milling vibrations can occur which the achievable tool life and / or affect the machining tolerances. Such effects occur especially with hard materials to be machined.

Of the Invention is based on the object, in particular for processing hard materials suitable end mill specify which characterized by a particularly low sensitivity to vibration.

These The object is achieved by an end mill with the features of claim 1. The end mill has at least two end cutting edges and a corresponding number of peripheral cutting, which in each case arranged offset by a pitch angle to each other on the tool circumference are. The pitch angle formed between adjacent peripheral cutters deviates from the mean given by the number of peripheral cutting edges Angle component, for example, a 90 ° angle in the case of a four-bladed Tool, off. The unequal angular distribution causes the total number The peripheral cutting no reinforcing resonances in the Can generate processing. If through the individual peripheral cutting edges caused vibrations occur, they have different, mutually weakening Vibration characteristics on. Particularly suitable here Pitch angle between adjacent peripheral cutting, which by minde least 1 ° and at most 10 °, preferably at most 5 °, from deviate in average angular proportion. The pitch angle between the Circumferential cutting thus varies in a four-bladed end mill preferably at least in the range between 89 ° and 91 ° and maximum in the range between 80 ° and 100 °, in particular between 85 ° and 95 °. A extensive symmetry of the end mill is according to preferred embodiments achieved with an even number of peripheral cutting. Show here preferably in each case opposite Division angle equal amounts on. Due to the given, at least extensive symmetry of the mass distribution The end mill is also suitable for high speeds around the tool axis.

Of the formed at each peripheral edge, through the angle relation between the chip surface and a rake at the tool circumference given rake angle is negative, preferably in the range between -5 ° and -20 °, in particular between -5 ° and -15 °. By the Negative rake angle is the workpiece to be machined in the range of the chip strongly deformed and thus strongly heated. typically, Temperatures of approx. 600 to 800 ° C occur during machining. Of the End mills is so special for the Machining hard materials suitable. Likewise, an end mill with same geometric features, however, in a special way for editing soft materials. The rake angle is preferably on all peripheral cutting edges, at least in a cross-sectional plane arranged perpendicular to the tool axis, identical. The cutting forces are typical of a tool with a negative rake angle greater than for a tool with a positive rake angle. Therefore, in the former Case the problem in the machining of occurring vibrations more pronounced. This problem is due to the vibration-damping unequal angular distribution of Circumferential cutting effectively countered.

Of the Core diameter, i. by the depth of the between the peripheral cutting edges arranged flutes of certain diameter of the end mill should on the one hand in relation to the tool outside diameter big enough be a high stability in particular for to ensure the machining of hard materials of the intended tool On the other hand, however, allow a slight chip removal. These competing requirements become particularly advantageous Further education takes into account that the core diameter reduced towards the front of the tool. The core diameter This may be the tool tip continuously and / or gradually reduce. In a section spaced from the front side of the tool has the end mill preferably a maximum core diameter of at least 70% and at most 90%, in particular about 80% of the tool outer diameter. To the tool tip, i.e. towards the front side, is preferably each flute with a provided the groove diameter reducing groove recess. That too referred to as the end core diameter reduced core diameter is in this range preferably between 50% and 70%, in particular approximately 60%, of the tool outside diameter. This is the reduced core diameter about 65% to 85%, especially about 75%, of the unreduced core diameter outside the groove recesses.

The transition between the flutes outside the groove recesses and arranged in the area of the tool tip Groove recesses is preferably designed such that a chip breaker is formed, whose width is at least approximately the depth of the flutes in the distance from the front side, well-free area of the Circumferential cutting corresponds. The chip breaker is to the tool axis limited by an approximately parallel to the associated peripheral edge extending leading edge, at least approximately on the surface of a imaginary cylinder runs, its diameter is the maximum core diameter, i. the core diameter outside the groove recesses, corresponds. The small width of the chip breaker Compared to the entire flute including grooved recess provides sure that formed chips be bent away from the end mill with a tight bend radius. On This way, both a slight chip removal is possible as also a low heat transfer from the chip to the tool. The transfer of a high proportion The heat generated during machining on the chip is also favored by the negative rake angle. The axial length of the groove recesses is preferably at least half and at most twice the diameter of the end mill. After a preferred embodiment corresponds to the axial length the groove recesses about the diameter of the end mill.

A favorable Cutting geometry at the peripheral cutting edges while at the same time more stable Design of the end mill is preferably given by a bordering on the peripheral edge Extensive open space forms a shell clearance angle of at least 6 ° and at most 10 °. The open space is preferably in the form of a concavely curved radial rear grinding educated. Alternatively, for example, a two-bevel relief with a primary bevel and a relative to this radially inwardly kinking Sekundärfase feasible.

Provided the peripheral blades have a helical shape is their helix angle dependent on mainly selectable from the material to be processed. Preferred is the twist angle at least 45 ° and maximum 60 °, in particular about 50 °. By this relatively large Twist angle is a particularly easy chip removal, in particular for larger processing depths in relation to the tool diameter.

One Selbstzentrierungseffekt the end mill is according to a preferred Training given by a hollow grinding on the front page. Here, the end cutting preferably form a hollow ground angle of at least 1 ° and at the most 5 °. At the Attaching the end mill to the surface of the to be machined workpiece thus creates a negative cone, which is the self-centering causes.

At every front cutting edge closes preferably a Planfase, which lies in a plane which is approximately parallel to the tool axis. The Planfase also borders to the end cutting associated peripheral edge. A corner radius in the transition area between the end cutting edge and the peripheral cutting edge should be such be measured that given both a high wear resistance of the tool is good as well as the cutting forces remain manageable. Before preferably the corner radius is smaller dimensioned as the Planfase in the axial direction of the end mill, i. the rounding between the cutting edge and peripheral edge extends just over a part of the width of the plane bevel.

Of the Advantage of the invention is in particular that by the unequal Angle division between the individual peripheral cutting an end mill and the negative rake angle of the peripheral cutting one at high Cutting performance virtually vibration-free operation of the tool allows is, with a very high stability of the tool at the same time Good chip removal through a magnifying away from the front Core diameter is given.

following is an embodiment of Invention explained in more detail with reference to a drawing. Herein show:

1a to 1c each in a cross-sectional view of an end mill,

2 the end mill in a fragmentary side view,

3 partially a front and peripheral edge of the end mill, and

4 a plan view of the Strinseite the end mill.

each other corresponding parts are in all figures with the same reference numerals Mistake.

All figures show an end mill made of solid carbide 1 , which is particularly suitable for machining hard materials, such as chilled cast iron. The end mill 1 is a four-bladed tool with four at its front 2 arranged end cutting 3 of which two extend over the entire tool radius and two extend only over an outer portion of the tool radius, and four helical Um fang cut 4 educated. The 1a to 1c each show a section perpendicular to the tool axis A, wherein the cutting plane 2 mm ( 1a ), 5 mm ( 1b ) or 7 mm ( 1c ) from the front 2 is spaced. The individual peripheral cutting edges 4 are by the reference numerals 4a to 4d characterized in that the peripheral cutting edges 4a and 4c as well as the peripheral cutting edges 4b and 4d each opposite. The angles between each two adjacent peripheral cutting edges 4a to 4d are designated as pitch angle t ₁ to t ₄ . The pitch angle t ₁ between the peripheral cutting edges 4a and 4b and the pitch angle t ₃ between the peripheral cutting edges 4c and 4d is 93 °, while the pitch angle t ₂ between the peripheral cutting edges 4b and 4c and the pitch angle t ₄ between the peripheral cutting edges 4d and 4a each 87 °. Each pitch angle t ₁ to t ₄ thus deviates from the number of peripheral cutting edges 4 given mean angle of 90 ° by 3 °. In this case, the respective opposite circumferential cutting edges close 4a and 4c such as 4b and 4d each a 180 ° angle between them. Due to the unequal division of the peripheral cutting edges 4 on the circumference of the end mill 1 its oscillation tendency is drastically reduced compared to a milling tool with symmetrical blade pitch. At the same time is the end mill 1 by the symmtric number of peripheral cutting edges 4 with exactly opposite arrangement of two peripheral cutting edges 4 fully balanced, so that operation is possible even at high speeds. The end mill 1 is made with or without coating, such as titanium-aluminum nitride, and mainly intended for dry machining.

Each peripheral cutting edge 4 forms on the tool circumference a negative rake angle γ _M of about -10 °. The chip angle γ _{M, which} is also referred to as the mantle chip angle, is exactly determined by the tool geometry and not dependent on the type of machining, as in the case of a turning tool. Due to the negative rake angle γ _M , the risk of breakage at the peripheral cutting edge or cutting edge is also at dry machining of hard and brittle materials with high processing speeds 4 minimized. The wedge angle at the cutting edge 4 is greater than 90 °.

Between every two adjacent peripheral cutting edges 4a to 4d extends a flute 5 whose depth, as from a comparison of 1a to 1c can be seen varies. Every flute 5 points in the front side 2 facing area a groove recess 6 on, which extends along the tool axis A over a length L which exceeds the tool diameter D something. While on average 1a the groove recess 6 is fully formed, and on average 1 c is missing, shows 1b a transition region with partially formed Nutvertiefung 6 , In the rear area of the end mill 1 without Spannutvertiefung have the flutes 5 a largely constant depth.

The directly to the peripheral cutting edge 4 adjacent area of the chip surface forms in the front side 2 adjacent, the groove depressions 6 having area of the end mill 1 a chip breaker 7 , between this and the Nutvertiefung 6 a leading edge 8th is trained. The course of the leading edge 8th at least approximately corresponds to the course of a groove bottom 9 in that area of the flutes 5 in which they have no groove recess. In the latter area is the core diameter of the end mill 1 denoted by K ( 1c ). The reduced or minimum core diameter, also referred to as the end core diameter, in the region of the full extent of the groove depression 6 is denoted by K _S ( 1a ). The reduced core diameter K _S is 63% of the tool diameter, while the unreduced maximum core diameter K is 80% of the tool diameter D. Thus, the minimum core diameter K _{S is} about 77% of the maximum core diameter K. The reduction of the core diameter in the region of the front side 2 promotes easier chip removal, while the relatively large core diameter K in the clamping end of the end mill, not shown 1 facing area of the flutes 5 for a particularly high stability of the end mill 1 contributes. The shape of the chip breaker 7 is along the entire peripheral edge 4 practically unchanged.

Likewise, one points to the peripheral edge 4 bordering peripheral free surface 10 over virtually the entire extent of the peripheral edge 4 a constant, slightly concave shape with a shell clearance angle α _M of about 8 °. To the peripheral free surface 10 closes in comparison to this by a multiple wider flute 5 at.

A two-stage trained Stirnfreiwinkel α _S1 , α _S2 at the front cutting edge 3 is 6 ° or 15 °. The designated γ _{S end} rake angle is 0 ° to 1 °, so that at the front cutting edge 3 a wedge angle of less than 90 ° between a plane bevel 11 as rake surface and a frontal free surface 12 results. The frontal cutting 3 form on the front side 2 a hollow grinding with a hollow grinding angle δ of about 1 ° to 5 °.

The helical peripheral cutting edges 4 have a helix angle λ of 50 °. This relatively large helix angle λ favors a slight chip removal in the direction of the tool axis A. Furthermore, this reduces the milling resistance and the pressure resistance of the end mill 1 elevated.

In the transition area between the front cutting edge 3 and the peripheral cutting edge 4 is how particular out 2 can be seen, a rounding with a corner radius R provided. The corner radius R is smaller than a maximum width B of the end cutting edge 3 adjoining, approximately parallel to the tool axis A arranged Planfase 11 , The corner radius R depends on the diameter D of the end mill 1 about 0.5 to 1 mm.

1

End mills

2

front

3

end cutting edge

4a-4d

peripheral cutting edge

5

flute

6

notch groove

7

chip breaker

8th

leading edge

9

groove bottom

10

Extensive open space

11

parallel land

12

Forehead open space

A

tool axis

B

width

D

Tool diameter

K

core diameter

K _S

Forehead core diameter

L

length

R

corner radius

δ

Hollow-ground angle

γ _S

Front rake angle

α _M

Coat clearance angle

γ _M

rake angle

t ₁ -t ₄

pitch angle

λ

angle of twist

α _S1

End clearance angle

α _S2

End clearance angle

Claims (24)

End mill with at least two on one end face ( 2 ) arranged end cutting ( 3 ) and in each case adjacent to these peripheral cutting edges ( 4a . 4b . 4c . 4d ), which are each offset by a pitch angle (t ₁ , t ₂ , t ₃ , t ₄ ) to each other on the tool circumference, each peripheral cutting edge ( 4a . 4b . 4c . 4d ) forms a rake angle (γ _M ) and between the peripheral cutting edges ( 4a . 4b . 4c . 4d ) each a flute ( 5 ), characterized in that between the peripheral cutting edges ( 4a . 4b . 4c . 4d ) different pitch angles (t ₁ , t ₂ , t ₃ , t ₄ ) are formed and the rake angle (γ _M ) is negative. End mill according to claim 1, characterized in that the pitch angle (t ₁ , t ₂ , t ₃ , t ₄ ) from the by the number of peripheral cutting edges ( 4a . 4b . 4c . 4d ) given mean angular component by at least 1 °. End mill according to claim 1 or 2, characterized in that the pitch angle (t ₁ , t ₂ , t ₃ , t ₄ ) by the number of peripheral cutting edges ( 4a . 4b . 4c . 4d ) given average angle by at most 5 °. End mill according to one of claims 1 to 3, characterized by an even number of peripheral cutting edges ( 4a . 4b . 4c . 4d ). End mill according to one of claims 1 to 4, characterized in that the rake angle (γ _M ) is at least minus 5 °. End mill according to one of claims 1 to 5, characterized in that the rake angle (γ _M ) is at most minus 15 °. End mills according to one of the claims 1 to 6, characterized in that a core diameter (K) at least 70% of the tool diameter (D) is. End mills according to one of the claims 1 to 7, characterized in that the core diameter (K) at most 90% of the tool diameter (D) is. End mill according to one of claims 1 to 8, characterized in that each flute ( 5 ) in the front side ( 2 ) facing a groove depression ( 6 ) having. End mill according to claim 9, characterized in that a front core diameter (K _S ) in the region of the groove recess ( 6 ) is at least 50% of the tool diameter (D). End mill according to claim 9 or 10, characterized in that the end core diameter (K _S ) in the region of the groove recess ( 6 ) is at most 70% of the tool diameter (D). End mill according to one of claims 9 to 11, characterized in that the end core diameter (K _S ) at least 65% of the core diameter (K) in the region outside the groove recesses ( 6 ) is. End mill according to one of claims 9 to 12, characterized in that the end core diameter (K _S ) at most 85% of the core diameter (K) in the region outside the groove recesses ( 6 ) is. End milling according to one of claims 9 to 13, characterized in that in the region of Groove recesses ( 6 ) a chip breaker ( 7 ) with a leading edge ( 8th ) whose positioning is at least approximately by the maximum core diameter (K) in the area outside the groove recesses ( 6 ) is formed. End mill according to one of claims 1 to 14, characterized in that a to a peripheral cutting edge ( 4a . 4b . 4c . 4d ) bordering peripheral surface ( 10 ) forms a shell clearance angle (α _M ) of at least 6 °. Sheep cutter according to one of claims 1 to 15, characterized in that the to a peripheral cutting edge ( 4a . 4b . 4c . 4d ) bordering peripheral surface ( 10 ) forms a shell clearance angle (α _M ) of at most 10 °. End mill according to one of claims 1 to 16, characterized in that on a peripheral cutting edge ( 4a . 4b . 4c . 4d ) bordering peripheral surface ( 10 ) is concave. End mill according to one of claims 1 to 17, characterized in that the peripheral cutting edges ( 4a . 4b . 4c . 4d ) form a helix angle (λ) of at least 45 °. End mill according to one of claims 1 to 18, characterized in that the peripheral cutting edges ( 4a . 4b . 4c . 4d ) form a helix angle (λ) of at most 60 °. End mill according to one of claims 1 to 19, characterized by a hollow grinding on the end face ( 2 ). End mill according to claim 20, characterized in that the end cutting edges ( 3 ) form a hollow grinding angle (δ) of at least 1 °. End mill according to claim 20 or 21, characterized in that the end cutting edges ( 3 ) form a hollow grinding angle (δ) of at most 5 °. End mill according to one of claims 1 to 22, characterized by a to the end cutting edge ( 3 ) bordering plane bevel ( 11 ). End mill according to claim 23, characterized in that between the end cutting edge ( 3 ) and the adjacent peripheral cutting edge ( 4a . 4b . 4c . 4d ) a corner radius (R) is formed, which is less than the maximum width (B) of the Planfase ( 11 ).