DE102010026947B3 - Drilling tool, use of this drilling tool and drilling method performed with the drilling tool - Google Patents

Abstract

The invention relates to a drilling tool, a cutting edge bevel (18) being provided according to the invention.

Description

The invention relates to a drilling tool for machining metals with at least one chamfer. According to a second aspect, the invention relates to the use of this drilling tool and, according to a third aspect, to a drilling method carried out with the drilling tool.

Drilling tools are known in various forms, such as drills, as indexable inserts for drilling tools or as a drill bit.

A drilling tool is, for example, a from the DE 103 32 930 A1 Known tap for cutting internal threads. This known tap is optimized in particular with regard to a high cutting speed and should ensure sufficient process reliability despite the very high cutting speeds. For this purpose, at least two cutting lugs of the tap are equipped with cutting edges, wherein the cutting at least in the lead have a cutting edge bevel with a negative angle, which reduces the effective rake angle of the cutting.

Another drilling tool is one of the EP 0 661 122 A1 known indexable insert. This has several major cutting edges and minor cutting edges on an approximately equiangular triangle, which coincide with the sides of this triangle or dull the main cutting edges. In order to further improve the stability in the cutting corners, in particular for milling operations, cutting edge chamfers are provided in the corner regions, wherein the cutting edge chamfer is broader in the corner area than along the substantially straight cutting edges.

Another, from the DE 695 02 106 T2 Known insert has between a cutting edge and a sinking surface area each have a rising Schneidkantenfase.

In a cutting element for machining in the DD 145 070 A a continuous or interrupted Schneidkantenfase is provided in which the cutting geometry is designed so that a stable main cutting relieves a minor cutting edge and a high wear resistance of both cutting is guaranteed.

One from the DE 29 46 022 C2 The known polygonal cutting insert also has a cutting edge with an associated cutting edge land and an inclined rake surface extending inwardly from the cutting edge land.

From the DE 10 2005 003 496 A1 a drilling tool is known which has a main cutting edge which is broken by grinding a Schutzfase. This is intended to increase the service life of the drilling tool. This protective bevel is varied over the length of the cutting edge as a function of the distance from the drill axis. This is intended to ensure that the protective bevel of the cutting edge at the respective point has the optimum geometric properties with respect to cutting speed and cutting direction. The protective chamfer is arranged in each case on the chip surface side.

In addition to the problems mentioned in these documents, there is just another problem when drilling.

When drilling, especially when drilling in metal, it can come to the so-called rattle. In this case, a vibration of the drilling tool used in the longitudinal direction leads to a waviness in the bottom of the hole, which causes the force acting in the longitudinal direction of the drilling tool feed force fluctuates and amplifies the vibration. Rattling lowers tool life and leads to unwanted noise.

In the prior art it is known to absorb vibrations by a built-in tool shank damper. The disadvantage of this is the high design complexity and associated with the installation of the damper material weakening.

Another from the DE 10 2008 045 326 A1 Known proposal for twist drill also tries to reduce the loads occurring in non-round holes and rattle. For this purpose, guide bevels are arranged on the peripheral surface of a drill.

A similar proposal will be made in the WO 88/03849 A1 described in which the angular pitch of several main cutting edges is made uneven, which should also eliminate the tendency of the drill to rattle.

Also the DE 10 2006 025 294 A1 deals with a drilling tool in which a Stützfase is provided.

Nevertheless, the fundamental problem of a Ratterneigung of drilling tools remains.

The invention has for its object to reduce the Ratterneigung.

The invention solves the problem in a generic drilling tool characterized in that an end face of the drilling tool ( 10 ) at least one cutting edge land ( 18 ) is provided.

folgt, wobei α_oe ∊ [0, ... 10°] und ε ∊ [–1°, ... 1°] gilt, in einem Bohrverfahren mit dem Zahnvorschub f_z. Der Spitzenwinkel σ kann, muss aber nicht konstant sein, sondern kann auch eine Funktion des Radius R sein. In diesem Fall ist dann der jeweilige Wert des Spitzenwinkels an der radialen Position σ(R) für σ einzusetzen. Die hier benutzten Bezeichnungen für die Winkel und Ebenen an Bohrwerkzeugen richten sich nach der DIN 6581 „Bezugssysteme und Winkel am Schneidteil des Werkzeuges”.According to a second aspect, the invention solves the problem by the use of such a drilling tool having a number of teeth, a radius, a point angle and a clearance angle of the Schneidkantenfase, at least beyond a core of the drilling tool and at least partially the relationship

follows, where α _oe ε [0, ... 10 °] and ε ε [-1 °, ... 1 °], in a drilling process with the tooth feed f _z . The apex angle σ may, but need not be constant, but may also be a function of the radius R. In this case, then insert the respective value of the point angle at the radial position σ (R) for σ. The designations used here for the angles and planes on drilling tools are based on DIN 6581 "Reference systems and angles on the cutting part of the tool".

According to a further aspect, the invention solves the problem by a drilling method with such a drilling tool and with the steps of (a) providing a drilling tool with a cutting edge land having a clearance angle, and (b) drilling with the drilling tool at a speed and a feed rate in a workpiece, so that a Wirk-Orthogonalfreiwinkel results in the region of the Schneidkantenfase that is at least partially at least temporarily at least temporarily not more than 5 ° at least outside of a core of the drilling tool, in particular at most 1 °.

An advantage of the invention is that the chattering can be reduced by simple means.

Another advantage is that an increased component quality can be achieved with a constant or higher removal rate. It is another advantage that tool wear can be reduced. Even a noise caused by rattling is avoided. If modular drilling tools with core bits are used, process vibrations and chatter can promote wear on the interfaces between the drill bit and the tool body. The invention reduces this interface wear. Due to these advantages, an increase in the length-to-diameter ratio of the drilling tool is possible.

The invention is based on the finding that during drilling, when there is process vibration and / or chattering, there is a periodic longitudinal movement of the drilling tool along its longitudinal axis. Since the effective orthogonal free angle depends on the movement in the longitudinal direction, rattling also varies the effective orthogonal free angle. If a cutting edge chamfer is now provided, the effective orthogonal clearance angle during chattering falls below 0 °, at least at some points of the cutting edge chamfer. In other words, the free surface contacts the material at the bottom of the bore, which effectively dampens the process vibration or rattle. If there is no chattering, the effective orthogonal clearance angle is generally greater than 0 °, so that no additional undesired friction effects occur compared to a conventional drilling tool.

It follows from the known kinematics of the drilling process that a chamfer on the drill cutting edge must lead to increased friction of the drill on its end face with the workpiece. The term drill cutting edge refers to drilling tools in general, it was chosen only because of the conciseness. This results in an undesirable heat development. Furthermore, an undesirable smearing of the material is to be feared. Furthermore, increasing process forces or an increasing cutting torque and thus an increasing cutting performance due to the chamfer are to be assumed. However, it has been shown that the disadvantages mentioned are overcompensated by the advantage of the smaller Ratterneigung.

In the context of the present description, the drill is understood in particular as a helical drill. It is particularly favorable if the drill is a metal drill. The drill can for example be made of high-speed steel, carbide, ceramic or cermet. The drill may be coated with a layer of hard material, such as TiC or TiN.

The cutting edge bevel is a chamfer on the cutting edge on the end face of the drilling tool, in particular the drill. This is preferably produced by a material-removing method, in particular a cutting method. For example, the cutting edge bevel is made by grinding. In particular, the cutting edge land is a bipartition of the free surface.

As a rule, the drilling tool, in particular the drill, has a core in the vicinity of which the material to be drilled, in particular the metal, is not cut during the drilling process, but is squeezed. In this case, the cutting edge land is preferably mounted outside the core. Whenever a drill is mentioned below, it always means a drilling tool.

According to a preferred embodiment, the cutting edge land extends to at least a part of the cutting edge length of the cutting edge. The cutting edge length measures the distance over which the cutting edge extends, that is, the distance between the core of the drill and its outer edge. The greater the proportion of the cutting edge length over which also extends the Schneidkantenfase, the more effective is the damping during chattering. It is favorable if the cutting edge phase extends over more than 1/3 of the cutting edge, but this is not necessary.

Preferably, the first tool-orthogonal free angle of the Schneidkantenfase, which can also be called bevel angle and is generally referred to as α _{o, 1} , monotonically decreases at least beyond the core with increasing distance from the longitudinal axis. In particular, the first tool orthogonal clearance angle of the cutting edge land is strictly monotone. A monotonous drop is understood to mean that the first tool orthogonal clearance angle of the cutting edge land is at least not greater at a greater distance. For a strictly monotonic decay, the first tool orthogonal clearance angle of the cutting edge land is smaller at a greater distance. This concept of monotony corresponds to that used in mathematics. The farther outward a predetermined point on the cutting edge land is, the greater the distance from the longitudinal axis, the higher the cutting speed at this point during drilling. A vectorial consideration of the velocity components, as discussed below, shows that the effective orthogonal free angle α _oe remains constant with the highest possible approximation.

beschreibbar ist, wobei für alle Abstände R ε(R) ∊ [–1°, ... 1°] gilt. Der erste Werkzeug-Orthogonalfreiwinkel der Schneidkantenfase α_o,1 der Schneidkantenfase und der Ziel-Wirk-Orthogonalfreiwinkel α_oe der Schneidkantenfase werden in der Werkzeug-Orthogonalebene P_o gemessen.A particularly effective damping results in the case of chatter, when the clearance angle as a function of a distance to the longitudinal axis at least partially follows a course, which by the formula

is writable, wherein for all distances R ε (R) ε [-1 °, ... 1 °] holds. The first tool orthogonal clearance angle of the cutting edge land α _{o, 1 of} the cutting edge land and the target effective orthogonal clearance angle α _{oe of} the cutting edge land are measured in the tool orthogonal plane P _o .

In this formula, α _{oe is} a target effective orthogonal free angle, which is in particular greater than or equal to 0 °. It has been found that it is advantageous if this angle is at most 2 °. Values of at most 1 ° are particularly favorable. The target effective orthogonal clearance angle α _oe depends on the kinematics of the drilling process in which the drill is to be used. However, since most drills are designed for a particular type of process, for example in terms of the ratio between rotational speed and thus peripheral speed at the outermost point, and feed rate, can be determined from these design variables, the angle α _oe .

The size R _char is a characteristic length, which also depends on the kinematics of the later drilling process. In particular, the characteristic length is at most 1 mm, in particular at most 0.5 mm. For the realization of the above feature, the exact knowledge of the effective orthogonal free angle α _oe and the characteristic length R _char irrelevant, it is only relevant that constants in the form of α _oe and R _char exist for the first tool orthogonal free angle α _{o , 1} follows the given course. The size ε (R) is a tolerable deviation. It is particularly favorable if ε = 0 ° for all R applies. Small deviations are possible, however, so that ε (R) ε [-1 °, ... 1 °] can apply.

According to a preferred embodiment, the cutting edge land has a width of at least 10 μm. Bel smaller chamfer results only a weak attenuation. Smaller widths of the Schneidkantenfase are therefore possible, but not very advantageous. Particularly advantageous are widths of cutting edge bevels of at least 125 microns.

It is favorable if the cutting edge bevel has a width of at most 300 μm. With wider cutting edge chamfers otherwise results in high friction when drilling in metal. This can lead to increased wear and increased temperature stress on the workpiece and the drill, which is undesirable. Nevertheless, wider cutting edge chamfers are at least conceivable.

The width b of the cutting edge bevel can be constant along the cutting edge, but this is not necessary.

Also with respect to the use according to the invention, the effective orthogonal clearance angle α _{oe is} preferably greater than 0 °. It is particularly favorable if the active orthogonal clearance angle is at most 2 °. The tolerable deviation ε is preferably greater than minus 0.5 and or less than 0.5 °.

The formula given indicates the first tool orthogonal clearance angle of the cutting edge land as a function of the distance R from the longitudinal axis for each point of the cutting edge land. As described above, the tooth feed f _z depends on the speed of the drill and the feed rate. The number of teeth z, however, is at Drill specified. If the drill is used with the specified parameters in a drilling process, so that the tooth feed f _z results, this leads to a particularly low vibration and low-noise drilling process.

In a drilling method according to the invention, the rotational speed and the feed rate are selected such that the effective orthogonal clearance angle is at least temporarily smaller than 5 °. In particular, the speed and the feed rate are chosen so that the effective orthogonal free angle is less than 3 °, in particular less than 2 °. It is particularly favorable if the effective orthogonal clearance angle is at least temporarily smaller than 1 °, in particular smaller than 0.5 °. Such a choice of speed and feed rate allows high Zeitspanvolumina while low Ratterneigung. The feature that the effective orthogonal clearance angle is at least temporarily smaller than the indicated angle is understood in particular to mean that this effective orthogonal clearance angle is at least occasionally achieved. In particular, the speed and the feed rate can be selected so that no rattling occurs in the majority of processing cases. If it comes to rattling, the feed rate can be increased so that the effective orthogonal free angle decreases, for example, to a value of less than 0.5 °, sometimes even to a value of 0 ° and smaller, so that the chattering is suppressed. It follows from the nature of a machining process that this condition only lasts for a short time, namely until rattling is stopped. As a rule, the feed rate is then reduced in order to save the tool.

According to a preferred embodiment, the drilling method comprises the steps of detecting whether chattering exists and, if so, changing the feed rate and / or the rotational speed so that at least at one point along the cutting edge land the effective orthogonal clearance angle is at most 1 °. In particular, the feed rate is increased so that the effective clearance angle is at most 0.5 °, more preferably at most 0 °. As a result, as described above, the chatter is effectively suppressed.

Particularly preferably, the method comprises the steps that after increasing the feed rate due to chattering again continuously detects whether chattering is present and the feed rate and / or the speed are changed, so that at least at one point outside the core of Wirk-Orthogonalfreiwinkel increased.

More preferably, the drill has a length to diameter ratio greater than 10, more preferably greater than 15.

In the following the invention will be explained in more detail by means of embodiments with reference to the accompanying drawings. The designations used here for the angles and planes on drilling tools are based on DIN 6581 "Reference systems and angles on the cutting part of the tool". It shows

1 with the subfigures 1a . 1b . 1c schematically a drill with the relevant sizes,

2 with the subfigures 2a . 2 B a drill according to the invention with the relevant sizes,

3 with the subfigures 3a . 3b and 3c various cuts at different radial positions of the drill according to the invention.

4 the course of the first tool orthogonal free angle (chamfer angle) α _{o, 1} in a drill according to the invention for different tooth feeds f _z and

5 a schematic view of a drill according to the invention.

1a shows a drill known from the prior art 10 In the form of a helical drill, the z = 2 teeth and thus a first helix 12.1 and a second coil 12.2 having. The drill 10 has a first cutting edge 14.1 and a second cutting edge 14.2 which, according to another nomenclature, may also be regarded as parts of a common cutting edge.

It can be seen that a distance R from the longitudinal axis L, which could also be referred to as a local radius, extends to an outer edge, where this distance assumes the value of a maximum distance R _max . The drill moves with the feed rate v _f in the workpiece. The feed rate results from the product of the tooth feed f _z , the number of teeth z and the speed n: v _f = f _z z n. The projection of the feed rate v _f on the tool orthogonal plane P _o gives the speed v _fo .

1b shows a view according to the level AA in 1a , The drill 10 is designed to be rotated at a speed n (in revolutions per second). In this case results in a cutting speed v _c (R), which depends on the distance R from the longitudinal axis. This is indicated by the three different velocity vectors. In the immediate vicinity of a longitudinal axis L has the drill 10 a core 16 ,

1c shows the kinematic conditions at the sharp cutting edge in the cutting plane BB. This plane is the tool orthogonal plane P _o . This plane is a plane through the selected cutting point parallel to the cutting direction. It can be seen that the cutting speed v _c (R) adds up vectorially to the feed rate v _f (both in length per unit of time). The result is an effective speed v _e (R), which depends on the distance R of the relevant point from the longitudinal axis. v _oe is the effective speed projected on the tool orthogonal plane P _o . The greater the distance R, the greater the cutting speed v _c , the feed rate v _f , however, remains constant. On the right side of the image it is shown that the effective orthogonal free angle α _oe for this reason also depends on the distance R and can be calculated therefrom and from the tool orthogonal free angle α _o . In 1c In addition, the tool cutting plane P _s , the effective cutting plane P _se and the main flank A _{α are} plotted.

2a shows an inventive drilling tool in the form of a drill according to the invention 10 with a cutting edge bevel 18.1 at the cutting edge 14.1 , The cutting edge bevel 18 has a width b of 150 microns in the present case, ie 0.15 mm. The second cutting edge 14.2 also has a Schneidkantenfase, but due to the perspective in 2a not visible.

2 B shows a view of the drill 10 from below, leaving the two cutting edge chamfers 18.1 and 18.2 are recognizable. The cutting edges 14.1 . 14.2 are curved. But there are also straight cutting edges possible. Also marked is a cutting edge length S2 of the cutting edge 14.2 ,

2a also shows three positions on the cutting edge 14.2 with the distances R ₁ , R ₂ and R ₃ , which are each different from each other. 2 B shows the associated tool orthogonal planes P _{o, 1} , P _{o, 2} and P _{o, 3} , in the respective distances R ₁ , R ₂ and R _3, the cutting edge 14.2 cut and perpendicular to the cutting edge at these points 14.2 and parallel to the cutting direction. With regard to the given planes P _o, l, as described below, the respective first tool orthogonal clearance angles (chamfer angles) α _{o, 1} (R ₁ ) are determined at the location with the distance R ₁ .

3a shows a section through the cutting edge 14.1 at a distance R ₁ (ie with respect to the plane P _{o, 1} , cf. 2a . 2 B ). The first main free surface A _{α, 1} (cutting edge bevel) 18 forms with the tool cutting plane P _s in the tool orthogonal plane P _{o, 1,} the first tool orthogonal free angle α _{o, 1} (R ₁ ), which could also be referred to as chamfer angle. The cutting edge bevel 18 has the width b, which is measured in the cutting direction. Behind the cutting edge bevel 18 begins the second main free surface A _{α, 2} 20 , The second main free surface A _{α, 2} 20 forms with the tool-Schneldenebene P _s in the tool orthogonal plane P _{o, 1,} the second tool orthogonal free angle α _{o, 2} .

3b shows a section with respect to the plane P _{o, 2} , whose intersection with the cutting edge has the distance R ₂ from the longitudinal axis L. It can be seen that the first tool orthogonal clearance angle α _{o, 1} (R ₂ ) is smaller than at the smaller distance R ₁ . The second tool orthogonal free angle α _{o, 2} is the same. This is not absolutely necessary.

3c shows a section with respect to the plane P _{o, 3} at a distance R ₃ .

wobei der Wirk-Orthogonalfreiwinkel α_oe als 1° gesetzt wurde, der Zahnvorschub f_z wurde als f_z = 0,1 mm, f_z = 0,2 mm und f_z = 0,3 mm gesetzt, die Zähnezahl als z = 2 und der Spitzenwinkel als σ = 120°. 4 shows the dependence of the first tool orthogonal free angle α _{o, 1 of} the radius R for three different tooth feeds f _z . This follows the equation

where the effective orthogonal free angle α _{oe was set} as 1 °, the tooth feed f _z was set as f _z = 0.1 mm, f _z = 0.2 mm and f _z = 0.3 mm, the number of teeth as z = 2 and the apex angle as σ = 120 °.

5 schematically shows a drilling machine according to the invention 22 with a drill according to the invention 10 that is attached to a spindle 24 attached and rotatable by this motor. The spindle is powered by an electric controller 26 controlled. The control 26 is set up to control the spindle 24 so that it rotates at a speed n and at a feed rate vf to a workpiece 28 too moved.

The drill 22 also includes a sensor 30 , for example, an armature current of the spindle 24 , a force or a microphone 32 having. If it comes to rattling, it will be through the sensor 30 and or 32 detected and, for example via a radio interface 34 to the controller 26 directed. Other interfaces are conceivable, the only relevant factor is that the controller 26 can recognize the rattle.

If a rattle is detected, the controller increases 26 the feed rate v _f . Alternatively or additionally, the speed n can be reduced, which happens until the effective orthogonal free angle α _oe , the above in connection with 1 has become so small that the rattle is effectively damped. Captures the electrical control 26 this, it can be provided that this again increases the speed and / or reduces the Vorschubgeschwundigkeit v _f .

An effective orthogonal clearance angle α _oe of 0 to 3 ° has proven to be suitable for drilling in aluminum.

The point angle σ is in 1a located. Missing to determine the tip angle of the reference to the opposite edge, z. B. drilling tools with only one cutting edge or drilling tools with imbalance or drilling tools with broken or asymmetric cutting, the point angle is determined by twice the angle between the tangent to the cutting edge and the longitudinal axis of the drilling tool.

LIST OF REFERENCE NUMBERS

10

drill

12

spiral

14

cutting edge

16

core

18

first main free surface (cutting edge bevel)

20

second main open space

22

drilling machine

24

spindle

26

control

28

workpiece

30

sensor

32

sensor

34

Radio interface

z

number of teeth

R

radial distance from the longitudinal axis L

n

rotation speed

α _oe

Active-Orthogonalfreiwinkel

α _o

Tool Orthogonalfreiwinkel

α _{o, 1}

first tool orthogonal clearance angle

α _{o, 2}

second tool orthogonal free angle

A _α

Primary flank

A _{α, 1}

first main open space

A _{α, 2}

second main open space

L

longitudinal axis

V _c (R)

cutting speed

V _f

feed rate

V _fo

Feedrate projected to the tool orthogonal plane

V _e

Casting speed

V _oe

Actual speed projected on the tool orthogonal plane

b

chamfer width

S

Cutting edge length

σ

Point angle

Claims (10)

Drilling tool ( 10 ) for machining metals with at least one bevel, characterized in that on an end face of the drilling tool ( 10 ) at least one cutting edge land ( 18 ) is provided. Drilling tool according to claim 1, characterized in that it is an indexable insert for a drill, a drill bit or a drill. Drilling tool according to one of the preceding claims, characterized in that the cutting edge chamfer ( 18 ) on at least a part of the cutting edge length (S) of the cutting edge ( 14 ). Drilling tool according to one of the preceding claims, characterized in that the first tool orthogonal clearance angle (α _{o, 1} ) of the cutting edge land ( 18 ) at least beyond a core ( 16 ) decreases monotonically with increasing distance (R) from the longitudinal axis (L). Drilling tool according to one of the preceding claims, characterized in that the first tool orthogonal free angle (α _{o, 1} ) as a function of a distance (R) to the longitudinal axis (L) at least partially follows a course, which by the relationship

is writable, wherein for all distances R ε (R) ε [-1 °, ... 1 °] holds. Drilling tool according to one of the preceding claims, characterized in that the cutting edge chamfer ( 18 ) has a width of at most 300 microns. Use of a drilling tool ( 10 ) according to one of claims 1 to 6, having a number of teeth (z), a radius (R _max ) and a first tool orthogonal clearance angle (a _{o, 1} ) of the cutting edge land ( 18 ), which is at least beyond a core ( 16 ) of the drilling tool ( 10 ) and at least partially the relationship

follows, where α _oe ε [0, ... 5 °] and ε ε [-1 °, ... 1 °], in a drilling process with the tooth feed f _z . Drilling method using a drilling tool ( 10 ) according to claims 1 to 6, with the steps: (a) providing a drilling tool ( 10 ) with a cutting edge bevel ( 18 ), which has a first tool orthogonal clearance angle (α _{o, 1} ), and (b) boring with the drilling tool at a rotational speed (n) and a feed rate (v _f ) into a workpiece ( 28 ), so that an effective orthogonal free angle (α _oe ) of the cutting edge bevel ( 18 ), which is outside a kernel ( 16 ) of the drilling tool ( 10 ) at least in sections, at least temporarily smaller than 7 °. Drilling method according to claim 8, characterized by the steps: - detecting whether chattering is present, and - if so changing the feed rate (v _f ) and / or the rotational speed (n), so that at least at a point outside the core ( 16 ) of the drilling tool ( 10 ) the effective orthogonal free angle (α _oe ) decreases. Drilling method according to claim 9, characterized by the steps: - detecting whether chattering is present, and - if there is no chattering, changing the feed rate (v _f ) and / or the rotational speed (n), so that at least at one point outside the core ( 16 ) the effective orthogonal free angle (α _oe ) increases.

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