DE20304580U1 - drill - Google Patents

Abstract

Drills, in particular twist drills and in particular for drilling to a solid in workpieces made of composite material with at least one fiber-reinforced and one metallic layer, with webs separated by main clamping grooves (10; 110), each of which is inserted into a lead bar (8 ; 108) and at least one trailing web (9; 109) are subdivided, which are limited on the circumference by circular bevels (7, 17; 107, 117), the chip chamber volume (Vz1; Vz1) of the additional grooves (12; 112) smaller than that Chip chamber volume (Vh1; Vh2) of the main clamping grooves (10; 110), characterized in that free areas (11, 11ü, 13; 111, 113) of the webs run in such a way that the trailing web (9; 109) meets its leading web (8; 108) axially lagging, the lag (N1; N2) from an outermost point (S1; S101) on a main runner edge (3, 3ü; 103) to an outermost point (S2; S102) on the main runner edge (21; 121 ) less than 2/10 of the drill Nominal diameter (D), preferably less than or equal to 1/10 of the nominal drill diameter (D), in particular less than or equal to 1/10 ...

Description

The invention relates to a drill for precisely fitting Bores, especially in composite materials, according to the preamble of claim 1.

Especially in aircraft construction today reinforced Composite or sandwich materials application. For the outer skin of modern aircraft for example, flat components made of composite materials are used, for example a layer of carbon fiber reinforced plastic, have a layer of titanium and a further layer of aluminum, wherein the layers can be arranged differently, or consist of a composite of an aluminum and a CFRP layer. Such materials have a despite their light weight high stability on. However, difficulties arise when assembling such components.

The individual parts of aircraft outer skins are mostly riveted together. Some riveting robots come here used based on data obtained by sampling the Skin contour, for example by means of laser markings in the individual flat components Drill out and rivet pre-drilled rivet holes. Combined drilling / riveting robots, which only drill the rivet holes at the defined points and then set the appropriate rivets are known. On the other hand however, the holes are also common into the aircraft components by hand and with appropriate hand drills brought in.

After no special attention in the past on the tolerances of the holes intended to accommodate the rivets had to be recognized after serious material demolitions that a tight tolerance of the rivet holes is required is. The targets are within the tolerance range IT8 - IT11.

To keep such tight tolerances to be able become conventional performed several work steps in succession, for example pre-drilling, Drilling and subsequent Ream out the hole created.

Based on this, it is the task the invention to provide a drilling tool with the good service life and accuracy of the holes even when processing Composite materials the tool change times can be reduced.

This task is due to the characteristics of claim 1 solved.

This was the cutting process investigated in composite materials in in-depth tests.

In general, components with a sandwich structure, which contain layers of CFRP (carbon fiber reinforced plastics), particularly difficult to handle in machining, because there is often delamination, i.e. tearing out individuals Fibers and thus fraying the borehole.

On the other hand, such sandwich materials have at least one metallic layer around the corresponding component the necessary To give resilience. For example, titanium, VA steel or aluminum layers used, which must also be machined without it becoming a There is a break on the drilling tool.

There are also other problem cases. This is how a titanium layer is created due to the huge Hardness and thus high friction a strong heat development. In particular common in aircraft construction In addition, the hand drills used are often not integrated into the tool Coolant supply provided so that only a direct supply of the coolant possible in the hole is. Because the coolant supply limited in this way there is often the effect that the lubricant used during the Piercing the titanium layer evaporates, leaving subsequent layers processed dry.

Other materials, such as Aluminum, on the other hand, tend to weld onto the tool. This is particularly problematic if a layer consists of a such material after a very hard layer, such as the titanium layer mentioned above must be processed. Because at one following the machining of a titanium layer to form a machined aluminum layer due to the development of heat, the tendency to weld on of the aluminum still increases strengthened.

The drill according to the invention has proven itself especially under these difficult operating conditions. He points to that according to claim 1 webs, which by additional grooves in a leading and one trailing web section (in the further leading and trailing web) be subdivided, the trailing web being axially the leading web lags, i.e. the main cutting edge on the trailing edge of the main cutting edge on the walkway. The lag measured from the extreme Point of the leading edge of the leading edge and the trailing edge of the main cutting edge - is less than 2/10 of the Nominal drill diameter, preferably at or below 1/10 of the nominal drill diameter, especially at or below 1/10 mm and the radial coordinate of the Round bevel essentially corresponds to that of the round bevel on the walkway.

It has been shown that when cutting CFRP material, individual fibers from the main cutting edge are not grasped as far as the outer circumference of the bore, but are cut through in an area lying further inwards, and the fiber stubs protruding from the bore wall from the lead web in the circumferential direction to the bore wall be pressed. These fiber stubs only straighten up after the cylindrical bevel has passed and can then be caught on the trailing web become. The axial trailing of the trailing land prevents the main trailing edge from being cut. The fact that the trailing edge of the main cutting edge does not cut has the effect that no machined material gets into the additional groove and can scratch the circumference of the hole there.

It is essentially done a separation of functions into the "cutting" function on the leading bar and "wiping" on the trailing bar. With the drill according to the invention is it possible also when used in composite material with at least one CFRP layer and a metallic layer with one operation per hole get along.

For centered support of the Drilling tools on the circumference of the holes are both on the trailing and also provided on the lead bridge round bevels, which essentially lie on the same radial coordinate. The rounded bevels on and footbridge support the drill while the one on the leading edge of the leading edge machining in the bore, causing bracing the drilling and thus centering the drilling tool succeeds.

The centered support of the Drilling tool on the circumference of the hole is an important one Part on the footbridge. While to be so great the lag must do that at desired It is ensured that the feed values on the main runner cutting edge on the other hand, it has been shown that the centering accuracy when entering the material, in particular in the CFRP material, depends heavily on the guidance the footbridge if possible sets in quickly after the machining process.

Through the values provided according to the invention for the Follow-up and the radial coordinates on the leading and trailing walkways both the separation of functions and timely onset the leadership ensured on the round bevel on the trailing web at the material entry. It has also been shown that with lag values in the range according to the invention the delamination when entering a CFRP material is kept low can be. Overall, can with the tool according to the invention CFRP materials with low delamination as well as metallic ones and hard layers can be cut with sufficient tool life.

In the advantageous embodiment according to claim 2 the drill is designed as a double cutter, i.e. with two walkways each and footbridges. In the context of the invention, however, there is also one Design as a three- or multi-cutter. Even with single-lip drills can an inventive design make sense.

In particular, the advantageous embodiment of the Drilling tool according to claim 3 with a positive rake angle on the trailing edge allows an effective combination of the drilling and finishing operations with just one tool. Because of the positive rake angle In particular, protruding parts on the trailing web secondary cutting edges Fiber residues, but also other surface roughness due to Post-processing in the sense of re-grinding on the circumference of the hole reliably removed become. Those with a positive (radial) rake angle Trailing bridge-side cutting scrape the circumference of the hole precisely. In doing so Fibers cut through when cutting in CFRP material Cutting process on the main cutting edge torn out of the fibrous material were. Thus, it also succeeds when cutting in the fibrous CFRP material, a smooth surface structure to create the circumference of the hole. The actual cutting work on material to be machined in front of the drill tip at the leading edge Huap cutting edge done.

Particularly suitable for the radial rake angle the trailing-edge minor cutting edge have values of 6 ° to 10 °, in particular 8 ° exposed.

The leading edge minor cutting edge can be one have positive, neutral or negative radial rake angles. If the leading edge minor cutting edge is neutral or negative radial rake angle is achieved, however, that post-processing on the circumference of the hole only at the trailing edge and can essentially slide through the leading edge minor cutting edge, without being cut into the material around the circumference of the hole to become.

This way the separation of the functions in machining on the leading edge skin edge and support as well as rubbing on the trailing edge of the secondary cutting edge and relieves the heavy-duty cutting corner on the leading web.

It has also been shown that the effects described above with different point grinding can be achieved. This makes it possible to use point grindings that are easy to produce to bring, such as a surface grinding, which can usually be produced by CNC machines. With an as The two-cutter drill is a 4-face bevel advantageous with which it succeeds in trailing the main cutting edge Stegs axially defined to move backwards, so that at the wished feeds does not intervene in the machining area and on the other hand immediately Entry of the drill into a workpiece has the stiffening effect of the wake.

In particular with a 4-surface grinding, it is advantageous if the first free surfaces adjoining the leading edge of the leading edge run at a reduced cutting angle compared to conventional drills, in particular below a clearance angle of 6 ° to 8 °. In this way, extremely hard materials (e.g. titanium) can also be machined without the risk of the leading edge cutting edge cutting off or breaking off prematurely.

According to claim 4 can also by a thinning achieves an advantageous shortening of the cross-cutting edge so that the centering properties of the drilling tool according to the invention can be further improved. It has also been shown that the shortening of the cross cutting Reduction of delamination when entering the CFRP material is achieved.

Further advantageous embodiments of the invention are the subject of further subclaims and relate to special problem cases which occur depending on the position of the individual layers in the sandwich material to be drilled and depending on the direction in which the hole is made in the material. As an explanation, reference is already made here to the 10 and 11 taken to clarify some of these specific problem cases.

10 shows a sectional view of a hole through a three-layer sandwich material, the upper layer of carbon fiber reinforced plastic (CFRP), the middle layer of titanium (TI) and the lower layer of aluminum. The desired drilling direction (B) runs downwards in the leaf plane. Problems were found in three places (P1, P2, P3).

To P1: As soon as you enter the CFRP material is delaminated, i.e. to tear out individuals Fibers made of plastic, so that at the entry into the CFRP material (at P1) forms a delamination funnel. In addition, the delamination leads to a Course of the tool and thus a centering error of the Tool. The one defined according to the invention Latency reduces this effect. Even the one above Crosscutting shortening this effect counteracts this effect: because on the cross cutting edge the drill is not cut, but only pressed when entering the CFRP material, do not cut it initially, but only fibers torn out of the material.

The shorter the chisel edge, the more the delamination caused by the chisel edge is smaller.

To P2: After cutting the CFRP material occurs the drill into the titanium layer. This leads to a so-called Wash-out at the edge of the CFRP layer (P2). It turned out that the hard titanium shavings, that occur when machining starts in the titanium layer, be pushed outwards and wash out material from the CFRP layer, or rub out.

P3: When machining the titanium layer the drill is extremely stressed and therefore extremely hot. It comes it often leads to evaporation of the coolant during the machining of the titanium layer and thus to dry running, especially on the cylindrical bevels. As a result, the drill is in the aluminum layer during the subsequent machining still extremely hot during that coolant evaporates before reaching the aluminum layer. It comes there to a reinforced one Tendency to weld material on the drill so that the hole diameter to exit from the Al layer increases (P3). In addition, there is a burr at the exit from the Al-hicht. the welded material to lead also that the drill becomes unusable after a relatively short idle time can be.

11 shows a sectional view of a hole through a two-layer sandwich material, wherein the upper layer consists of titanium (TI) or aluminum (AL) and the lower layer of CFRP and is drilled from top to bottom (B). It must be taken into account that the processing of sandwich material in important areas of application, such as in aircraft construction, is usually carried out with hand drills. Speed and feed control depending on the drilling depth is only possible to a limited extent.

In contrast to the approach to an exposed CFRP layer described above under P1, in which work is initially carried out under low contact pressure and with low feed rates until the CFRP layer is drilled through, the hidden CFRP layer becomes the 11 with the high speed and contact pressure values used to machine the upper layer made of A1 into the CFRP material. The CFRP layer is then drilled through without the cutting speed and feed being able to be adjusted before the drill emerges from the CFRP layer into the open.

The effect described above the oppressive Chisel edge that does not cut therefore occurs when the Reinforced drill on. This leads to an explosion-like, increased delamination (P4) because first is not cut, but only fibers from the material be torn out. Made like a Dum-Dum bullet in this way an exit crater at point P4.

The editing examples mentioned show that on sandwich material drilling tools depending on the sandwich structure and drilling direction have to meet different requirements. Construction measures, who are for one of the problem cases shown Cheap can impact on the other hand disadvantageous in another problem case impact so that for different sandwich arrangements and drilling directions different tools be proposed, but all as advantageous embodiments Are part of the invention.

According to claim 7, therefore, a drill is proposed which has a tip angle of less than 100 °, preferably 90 °. The drill tip has almost no chisel edge in this case; instead, the main cutting edges merge into one another in a pyramid shape, so that an actual centering point is present, which ensures that the drill penetrates the material exactly at the desired point and does not run. The "delamination explosion" among those referred to above 11 (P4) conditions described for the hand-guided exit from a CFRP layer into the open can thus be largely avoided.

As the pressing chisel edge largely is eliminated, the effect of the "delamination explosion" occurs at the outlet the CFRP location, so that an exit crater like a Dum-Dum projectile can be avoided. Due to the strong inclination of the main cutting edges expanded the hole is also reluctant to exit the CFRP layer, so that the drill does not break through in one fell swoop, but instead just peu à peu machined the end section of the CFRP material.

The advantageous embodiment of the drill according to claim 8, however, is particularly suitable for in the 10 shown application. The leading edge of the leading edge - and thus the actual main cutting edge of the drill - runs at a tip angle of 140 ° to 170 °, with a value of 150 ° having proven to be particularly suitable. However, the leading edge of the main cutting edge does not connect directly to the leading edge of the leading edge of the leading edge, but rather via a transition area in which the main cutting edge falls more steeply. The main cutting edge is longer in the inner area than in the outer transition area. The leading edge of the leading edge thus divides into a longer inner area or section in which it slopes gently and a shorter transition area or section in which it slopes steeply.

The divided main cutting edge leads here also for a split machining process. It comes to the following Effect: relatively long chips, resulting from machining on the inner area of the main cutting edge, be outward distracted and meet there at the transition area relatively short chips. Due to the steepness of the transition area become the short chips twisted towards the interior of the chip chamber. This will make them flat sloping inner section of the main cutting edge resulting long chips back inside the Chip chamber pushed away.

When exiting a CFRP layer and simultaneously entering a hard material layer, in particular a titanium layer, in which it is often related to the above 10 (P2) leaching, it is possible to prevent the hard material chips from rubbing against the CFRP material on the circumference of the drill and causing the unwanted leaching. The wall of the hole made in the CFRP material, which may have already been "cleanly" rubbed with the trailing-edge cutting edge, is no longer ripped through hard chips when entering the hard titanium.

Another advantage of the embodiment according to claim 8 relates to the loading of the cutting corners. There are no defined cutting conditions at the cutting edges, since they belong to the main cutting edge on the one hand and to the secondary cutting edge on the other. There is therefore no cutting at the cutting corner, only pressing. At the same time, the highest cutting speeds and the highest loads work there. The load on the cutting edge is alleviated by the transition area, since the transition from the main cutting edge to the secondary cutting edge no longer occurs suddenly at one cutting edge, but gradually over the transition area. The drill equipped with the transition area thus offers a longer service life when drilling sandwich material, especially in the 10 shown processing case.

Also regarding the above with reference to 10 addressed aluminum welds (P3), this embodiment offers advantages. Such welds occur regularly in the area of the cutting corners. On the one hand, this is due to the fact that due to the pressing, a high level of friction and therefore heat is generated on the cutting corner, so that there is often local melting of the aluminum. On the other hand, material that becomes fluid due to the heat at the tip of the drill flows in front of the drill along the main cutting edge towards the opposite end of the drill and tends to stick to the cutting edge, since the cutting edge acts as an edge in the flow of the flowable aluminum , This effect is also mitigated by the transition area.

Overall, according to this aspect of the invention, when drilling in sandwich material, in particular in 10 Machining shown, improved tool life and manufacturing tolerances, especially at the transition from CFRP to titanium and when emerging from the aluminum layer achieved. In tests, values of less than 1: 4 for the ratio of the length of the transition area to the length of the remaining leading edge of the leading edge have proven to be favorable.

Another advantageous embodiment have improvements in the design of the transition area to the content.

In a simple way the transition area through a bevel on the leading edge according to claim 8 realize. In experiments, there is a bevel angle to the axial direction from 10 ° to 20 ° and proven particularly favorable of 15 °.

With the chamfer curved according to claim 9 it is achieved that the cutting corner between chamfer and minor cutting edge is relieved, since the radial forces on the cutting corner are minimized in accordance with the almost radial transition area.

Regarding the outflow of flowable material it is advantageous if the transition area according to claim 10 is formed by a rounding. This way, at the same time the strain at the transition the main cutting edge to the minor cutting edge.

The transition area can also as a combination of a rounding with one above called curved Chamfer, i.e. roughly S-shaped be designed.

When designing the main cutting edge with a transition area becomes aware of a certain ridge formation when leaving the Aluminum put up with the above improvements in terms of tool life and hole tolerance. In particular in terms of welds when (dry) drilling through the aluminum layer have also the wide round bevels of the embodiment according to claim 11 proven to be advantageous since the larger support surface compared to conventional drills lower surface pressure on the rounded bevels.

By designing the drill with the wide circular chamfer, the overall dimensional accuracy and roundness of the holes can be further increased. This applies in particular to the processing of aluminum which is inevitably carried out dry due to the dry processing of the titanium layer, as in the 10 shown processing case is required.

The chamfer chamfer width vary along the axial direction of the drill, it is preferred however constant.

To continue the wear on the cutting edges decrease while too big Rounding and blurring is avoided, the drill advantageously has at least in the area of the sharp cutting edges, preferably on a coating a hard layer. In the field of sharp cutting edges means at least in the area of the leading edge and the trailing edge. For reasons of wear protection such a coating on the cylindrical bevels, the open areas, the Chip and additional grooves and in the area of the non-cutting edges also make sense where these are not directly related to the sharp ones and cutting edges, especially at the leading edge minor cutting edge and the trailing edge of the main cutting edge. In addition, a coating on a surface area can be completely vapor-deposited in a technically simple manner without that special covers are needed would, preferably in the CVD (chemical vapor deposition) process, that can be carried out with systems from Cemecon AG, for example can and with a layer thickness between 8 microns and 16 microns.

Diamond has proven to be particularly suitable, since it adheres particularly well to hard metal as the drill base material. In addition, diamond has a low affinity for aluminum, so that its tendency to weld (see 10 , P3) is reduced. As a material for the drill, however, all other common materials of modern high-performance drills can also be used, such as high-speed steel such as HSS or HSSE, HSSEBM, ceramics, cermet or other sintered metal materials.

The hard material layer is preferably present made of nanocrystalline diamond.

With the first prototypes of drills according to the invention in the configuration with wide circular bevels according to claim 11, diamond coating according to claim 13 and circumferential chamfering according to claim 8, the machining of the 10 Achieve a service life of 50 bores with tolerance deviations of 30 to 40 μm and with layer thicknesses of 5 mm CFRP, 4 mm titanium and 6 mm aluminum, whereby the machining of the titanium and aluminum layers was carried out dry.

In contrast, with drills according to the invention in the configuration with wide circular bevels according to claim 11, diamond coating according to claim 13 and a 90 ° tip angle according to claim 5, 11 achieve a service life of over 150 holes in the IT8 tolerance range with layer thicknesses of 5 mm CFRP and 6 mm aluminum.

For in addition to diamond, for example, the hard material layer also comes Titanium nitride or titanium aluminum nitride in question. Are particularly suitable et al a titanium aluminum nitride layer and a so-called multi-layer layer, which are called "Fire I "from the company Gühring oHG is marketed. This is a TiN - / (Ti, Al) N multilayer layer.

A wear protection layer can also be used with particular preference, which essentially consists of nitrides with the metal components Cr, Ti and Al and preferably a small proportion of elements for grain refinement, the Cr proportion being 30 to 65%, preferably 30 to 60% , particularly preferably 40 to 60%, the Al content is 15 to 35%, preferably 17 to 25%, and the Ti content is 16 to 40%, preferably 16 to 35%, particularly preferably 24 to 35%, in each case based on all metal atoms in the entire layer. The layer structure can be single-layer with a homogeneous mixing phase or it can consist of several layers which are homogeneous in themselves and which alternately consist of (Ti _x Al _y Y _z ) N with x = 0.38 to 0.5 and y = 0.48 to 0.6 and z = 0 to 0.04 and on the other hand consist of CrN, the top layer of the wear protection layer preferably being formed by the CrN layer.

On the other hand, chip evacuation in the To improve chip-guiding grooves (main clamping grooves on the pre-drilling area and grooves in front of the leading webs on the finishing area), the drill has a soft material coating, preferably made of MoS ₂ .

One according to claim 19 over the usual with drills drill rejuvenation reduced rejuvenation of the drilling tool according to the invention, preferably 0.02 to 0.4 mmm per 100 mm length and very particularly preferably exactly 0.04 mm per 100 mm length contributes to one Bracing of the drill section removed from the drill tip across from the closer at the tip of the drill section, so that the wedge side cutting edges open cut to a greater length.

Advantageous further developments of Invention are the subject of the rest Dependent claims.

The individual features of the embodiments according to the claims can be combined as desired, as far as it makes sense.

Below are schematic drawings preferred embodiments the invention closer explained. Show it:

1 a side view of a drill according to an embodiment of the invention;

2 a sectional view taken along the line II - II in 1 ;

3 a side view of a drill according to a further embodiment of the invention;

4 a sectional view taken along the line III - III in 3 ;

5 a schematic view of the drill of 1 and 2 to explain the lag of the leading edge of the leading edge compared to the leading edge of the leading edge;

6 one of the 5 corresponding schematic view of the drill of the 3 and 4 ;

7 to 9 Sectional views showing details of the lead bar of drills in section according to further embodiments of the invention;

10 a hole in a sandwich material in a first processing case; and

11 a hole in a sandwich material in a second machining case.

First, reference is made to those in the 1 . 2 and 5 illustrated embodiment of the drill. This embodiment is specifically for use in the already explained above and in the 10 designed processing case designed. The twist drill shown has two main main grooves 10 separate webs, which in turn by an additional groove 12 into a walkway 8th ( 2 ) and a footbridge 9 ( 2 ) are divided.

Inner main cutting edge sections run here 3 on the two walkways 8th at a tip angle WT1, which has a value of preferably 150 °, that is to say very flat, in order to steer the smallest possible force components in the radial direction during drilling. It is a sharpened point 4 to recognize, by which a shortening of the drill cross-section is achieved, in order to enable a precise drilling into the solid. The shortened cross cutting edge ensures that the tool is well centered when drilling, regardless of which material of the sandwich component is drilled. The main cutting edges 3 . 3Ü However, they do not fall flat to the cutting edge S1, but only run from the drill cutting edge to a transition corner S1ü at the flat tip angle WT. A transition area closes there 3Ü on which in turn on the cutting edge S1 a leading edge minor cutting edge 5 borders. The transition section 3Ü is thereby from a comprehensive chamfering of the leading bridge 8th formed, the chamfer angle WF is 15 °. The minor cutting edges 5 run from the cutting edge S1 on the leading edge of the leading web 8th helical on a cylinder with diameter D towards the opposite end of the drill.

The drill tip is in the form of a 4 -Surface grinding, with a first free surface 11 . 11ü roughly the walkway 8th corresponds and runs at a relatively flat clearance angle, while a second clearance area 13 in about the wake 9 corresponds and falls at a steeper clearance angle to such an extent that the cutting edge S2 between the trailing edge of the main cutting edge 21 and trailing edge cutting edge 23 opposite the cutting corner S1 between the transition area 3Ü the leading edge of the leading edge 3 . 3Ü and leading edge minor cutting edge 5 is axially offset to the rear.

To explain the axial lag N1 of the trailing-edge cutting corner S2 with respect to the leading-edge cutting corner S1, reference is now made to the 5 referred to schematically in the main cutting edge 3 . 3Ü on the lead bar and the main cutting edge 21 are marked on the trailing land at the same circumferential coordinate, ie first the leading edge of the leading edge 3 . 3Ü and then, after turning the drill by the appropriate angle to the same circumferential coordinate (with axial fixation), the trailing edge of the main cutting edge 21 , It can be seen that the trailing edge of the main cutting edge 21 at its outermost point (the cutting edge S2) the leading edge of the leading edge 3 . 3Ü lagging at its extreme point (the leading-edge cutting corner S1) by the value N1, which is drawn in the figure in an exaggerated manner for purposes of illustration.

The drill has the in 1 cross-section taken along the line II-II, which in 2 will be shown. In addition to the two main clamping slots 10 that before the two main minor cutting edges 5 form a channel for chip evacuation are the additional grooves 12 to recognize the two webs of the drill each in a lead bar 8th and a footbridge 9 subdivide and are at least essentially non-cutting, but each as one Type "reaming tooth" trained trailing land 9 are upstream.

The lead dock 8th is from the rake face to the leading edge minor cutting edge 5 , on the circumference by round ledge bevel 7 , as well as on the back through the additional groove 12 limited. After the additional groove on the back 12 the footbridge closes 9 which essentially has the cross section of a reaming tooth. The rake face on the trailing web 9 runs in such a way that the trailing edge of the secondary cutting edge 23 has a positive radial rake angle WSR of 14 °, so that the trailing flank minor cutting edge 23 scrape the inner circumference of the hole while on the leading edge of the 3 . 3Ü the actual cutting work is done during drilling. The rake angle WSR can be made as large as possible, with the stability of the cutting wedge forming the limit. To the trailing edge of the secondary cutting edge 23 closes another round bevel on the circumference 17 on which the trailing web is supported on the inner circumference of the bore.

Out 2 it becomes clear that the additional grooves are molded into the drill much less deeply than the main clamping grooves 10 , With a short-long-dashed line, a circle with the diameter d _{i is} drawn on which the two innermost points of the two additional grooves 12 lie. In contrast, the two innermost points of the two main chip slots are 10 on the much narrower circle with the diameter d _g , which is drawn with a simple dashed line. The core with the diameter d _g is therefore only from the main flutes 10 touched so that through the additional grooves 12 no significant weakening of the drill is caused.

The major part of the machining runs on the leading edge of the web 3 . 3Ü from. The machined material is over the main chip grooves 10 dissipated, on the one hand on the inner main cutting edge section 3 Chips with the width of the section 3 arise and on the other hand at the transition section 3Ü Chips with the width of the section 3Ü , The one at the transition section 3Ü resulting chips roll the on the section 3 resulting chips in the chip chamber of the main chip groove 10 back. In this way, it is possible to avoid scratching the bore wall that is cleanly rubbed off by the trailing secondary cutting edge, in particular when changing from a CFRP layer to a hard material layer, where there is a risk that the hard chips wash out the relatively soft, already rubbed bore.

The round bevels 7 . 17 support the drilling tool against the hole wall during drilling. The round bevels 7 . 17 each have a large width compared to conventional drills B7, B17 (B7: 12 mm, B17: 10 mm, D: 6.8 mm), so that the contact pressure is distributed over a large area and in addition to an effective support on Drill circumference there is less tendency to weld when machining aluminum.

The cut to the ordinary cutting on the main web 3 Subsequent fine machining on the circumference of the hole is mainly carried out with the trailing edge cutters 23 , the support of the drill in the borehole with the leading bridge round chamfer 7 and the trailing land round bevel 17 ,

The effect of CFRP material, in particular, is that individual fibers or fiber stubs protruding from the bore wall from the leading edge of the leading edge 3 not be recorded and when the leading bridge round bevel passes 7 be pressed against the bore wall. Only after the leading bridge round bevel 7 has run past, these fibers straighten up again and can then with the trailing edge cutting edge 23 be severed so that there is a smooth surface. Since the lag N1 ( 5 ) the trailing edge of the main cutting edge 21 opposite the leading edge of the leading edge 3 . 3Ü According to the invention is very small - in the embodiment shown 1/10 mm - the support effect on the trailing land circular chamfer begins immediately after entry into the material to be drilled through, so that good concentricity results.

Variations in the shape of the transition section are the 7 . 8th and 9 refer to. In 7 the transition section is designed as a curved curve K, the increase in the angle of curvature increasing from the inside to the outside in relation to the axial direction.

In the in 8th Modification shown, the transition section is formed by a rounding R.

9 time a transition section with an approximately S-shaped contour KR.

Referring to the 3 . 4 and 6 A further advantageous embodiment of the drilling tool will now be discussed. Functionally identical or similar features are provided with similar reference symbols. This embodiment is specifically for use in the already explained above and in the 11 designed processing case designed. The views shown correspond to those of 1 . 2 and 5 ,

How 4 shows the cross section of the drill corresponds to that of the previously explained embodiment. However, the drill has a tip angle WT2 of 90 °. The small tip angle results in a short chisel edge, with a point 104 is shortened even further. The main cutting edge 103 on the walkway 111 falls over its entire length to the runway cutting corner 5101 with the tip angle WT2. At the cutting corner 5101 closes the leading edge minor cutting edge 105 and the leading bridge round bevel 107 which, like the trailing land circular bevel 1127 with a constant width B107 or B117 from the drill tip to the opposite end of the drill. Like especially the 6 can be seen, the trailing edge cutting corner S102 lags the leading trailing edge by the value N2, which is also in the 6 is drawn in excessively large for clarification purposes and is approximately 1/10 mm.

Of course there are deviations from the embodiments shown possible without to leave the scope of the invention.

For example, it is conceivable to process a drill made as an Al-CFRP-RL composite using a drill with the one in the 1 shown geometry, but without the chamfer, respectively. to build the transition area. Because in this case, the occurs in the processing case 10 washout on the CFRP layer caused by the hard titanium layer. The burr formation caused by the chamfering at the exit from the Al layer does not have to be accepted in this case.

Furthermore, embodiments of the drilling tool according to the invention conceivable for an internal cooling are prepared as they will be in the future in certain circumstances is also supported with the hand drills used in aircraft construction, all the more so that occurs during the machining of titanium To be able to control heat development better.

There are various configurations of the drill integrated coolant supply conceivable.

With the centrally drilled cooling channel each free surface preferably has one with the cooling channel via connecting channels with the Internal cooling duct in Connected outlet opening on. With such a Y-shaped Channel systems do not occur even with minor lubrication (MQL) undesirable separation processes because, in contrast to spiral cooling channels, no centrifugal forces act.

In addition to a centrally drilled Cooling channel, that would be easy to manufacture one or more cooling channels coiled with the drill helix angle are also conceivable, which has the advantage of a more even Cooling, bring within the drill.

The coolant supplied in this way strikes directly the one to be cooled Area of the next to cutting material and can therefore both the main cutting cool during the cutting process as well as lubricate the flutes sufficiently to ensure adequate To ensure chip evacuation.

In addition, there can be additional outlet openings be provided in the flutes to additionally remove the chips by the chip grooves introduced coolant continue to improve.

In summary, those features are summarized in which the invention is embodied individually and in any combination with one another:
A drill, in particular a twist drill and in particular for drilling to a solid in workpieces made of composite material with at least one fiber-reinforced and one hard layer, has main clamping grooves 10 ; 110 separate webs;
the webs are each by at least one additional groove 12 ; 112 into a walkway 8th ; 108 and at least one footbridge 9 ; 109 divided;
forward web 8th ; 108 and footbridge 9 ; 109 are on the circumference of round bevels 7 . 17 ; 107 . 117 limited;
the chip chamber volume is Vz1; Vz1 of the additional grooves 12 ; 112 smaller than the chip chamber volume Vh1; Vh2 of the main span 10 ; 110 ;
areas 11 . 11ü . 13 ; 111 . 113 the webs run in such a way that the trailing web 9 ; 109 his lead dock 8th ; 108 axially lagging;
the lag N1; N2 from an extreme point S1; S101 on a main runway cutting edge 3 . 3Ü ; 103 to an extreme point S2; S102 on the trailing edge of the main cutting edge 21 ; 121 is less than 2/10 of the nominal drill diameter D, preferably less than or equal to 1/10 of the nominal drill diameter D, in particular less than or equal to 1/10 mm;
the circular bevel on the trailing web has essentially the same radial coordinate as the circular bevel on the leading web;
the drill has two lead bars ( 8th ; 108 ) and footbridges ( 9 ; 109 );
the footbridge 9 ; 109 has a trailing edge 23 ; 123 with a positive rake angle WSR1; WSR2, which is in particular in the range between 6 ° and 10 °, preferably around 8 °;
the drill has a point 4 ; 104 , by which a shortening of the cross cutting edge is brought about;
the point grinding is designed as a 4-surface grinding;
the free area adjoining the leading edge of the leading edge has a clearance angle between 6 ° and 8 °;
the drill has a tip angle WT2 of less than or equal to 100 °, preferably 90 °;
the drill has a tip angle WT1 of 140 ° to 170 °, in particular 150 °;
the leading edge of the leading edge 3 closes via a transition area that drops steeply towards it 3Ü on the leading edge minor cutting edge 5 on;
where is the length of the transition area 3Ü less than the length of the remaining leading edge of the leading edge 3 ;
a ratio of the length of the transition area 3Ü the length of the remaining leading edge of the leading edge 3 has a value of less than 1: 4;
the transition area 3Ü is from a circumferential chamfering of the open area 11 . 11ü formed, preferably with a bevel angle WF of 10 ° to 20 °, in particular 15 ° to the axial direction B;
the peripheral free bevel is continuously curved;
the curvature K is concave to the drill, the curvature angle to the axial direction preferably increasing from the inside to the outside;
the transition area is formed by a rounding R on the open area;
the round bevels 7 . 17 ; 107 . 117 on the leading and trailing bridges 8th . 9 ; 108 ; 109 have a width B7, B17; B107, B117 from 10% to 25% of the nominal drill diameter D, in particular 0.3 to 0.8 mm;
the drill has at least in the area of the sharp cutting edges 3 . 3Ü . 23 ; 103 . 123 a coating, preferably in the form of a hard material layer;
the thickness of the layer is preferably in the range between 8 and 16 μm, in particular 12 μm;
the layer is deposited using the CVD process;
the hard material layer consists of diamond, preferably nanocrystalline diamond;
the hard material layer consists of TiN or (Ti, Al) N, a multi-layer layer or a layer consisting of nitrides with the metal components Cr, Ti and A1 and preferably a small proportion of elements for grain refinement, the Cr content being 30 to 65%, preferably 30 to 60%, particularly preferably 40 to 60%, the Al content at 15 to 35%, preferably 17 to 25%, and the Ti content at 16 to 40%, preferably 16 to 35%, particularly preferably 24 to 35%, based in each case on all metal atoms in the entire layer;
the structure of the entire layer consists of a homogeneous mixed phase;
The structure of the entire layer consists of several homogeneous individual layers, which alternately consist of (Ti _x Al _y Y _z ) N with x = 0.38 to 0.5 and y = 0.48 to 0.6 and z = 0 to 0.04 and on the other hand consist of CrN, the uppermost layer of the wear protection layer preferably being formed by the CrN layer;
a soft material coating, preferably made of MoS2, is provided at least in the region of the grooves;
the nominal diameter D of the drill is in the range of 3 - 30 mm;
a taper of the drill from the drill tip in the axial direction along the drill is 25% -80% of the usual drill taper, which is preferably in the range of 0.02-0.4 mm, so that the taper is particularly preferably around 0.04 mm per 100 mm length;
the spiral angle of the drill is in the range of 20 ° - 40 °.

Claims (22)

Drills, in particular twist drills and in particular for drilling into solid workpieces made of composite material with at least one fiber-reinforced and one metallic layer, with through main clamping grooves ( 10 ; 110 ) separate webs, each with at least one additional groove ( 12 ; 112 ) in a walkway ( 8th ; 108 ) and at least one footbridge ( 9 ; 109 ) are subdivided, each of which is rounded by round bevels ( 7 . 17 ; 107 . 117 ) are limited, the chip chamber volume (Vz1; Vz1) of the additional grooves ( 12 ; 112 ) smaller than the chip chamber volume (Vh1; Vh2) of the main chip grooves ( 10 ; 110 ), characterized in that open spaces ( 11 . 11ü . 13 ; 111 . 113 ) the webs run in such a way that the trailing web ( 9 ; 109 ) his lead dock ( 8th ; 108 ) axially lagging, the lag (N1; N2) from an outermost point (S1; S101) on a leading edge of the leading edge ( 3 . 3Ü ; 103 ) to an extreme point (S2; S102) on the trailing edge of the main cutting edge ( 21 ; 121 ) is less than 2/10 of the nominal drill diameter (D), preferably less than or equal to 1/10 of the nominal drill diameter (D), in particular less than or equal to 1/10 mm and the cylindrical bevel ( 17 . 107 ) on the footbridge ( 9 ; 109 ) has essentially the same radial coordinate as the cylindrical bevel ( 7 . 107 ) on the walkway ( 8th ; 108 ). Drill according to claim 1, characterized by two leading webs ( 8th ; 108 ) and footbridges ( 9 ; 109 ). Drill according to claim 1 or 2, characterized in that the trailing web ( 9 ; 109 ) a secondary cutting edge ( 23 ; 123 ) with a positive rake angle (WSR1; WSR2), which is in particular in the range between 6 ° and 10 °, preferably around 8 °. Drill according to one of the preceding claims, characterized by a taper ( 4 ; 104 ), which leads to a shortening of the cross-cutting edge. Drill according to one of the preceding claims, characterized through a point grinding in the form of a 4-surface grinding. Drill according to one of claims 1 to 4, characterized through a free space adjoining the leading edge of the leading edge a clearance angle between 6 ° and 8 °. Drill according to one of the preceding claims, characterized by a tip angle (WT2) of less than or equal to 100 °, preferably 90 °. Drill according to one of claims 1 to 6, characterized in that the drill has a tip angle (WT1) of 140 ° to 170 °, in particular 150 °, and the leading web main cutting edge ( 3 ) over a transition area that drops steeply towards it ( 3Ü ) on the leading edge minor edge ( 5 ), the length of the transition area ( 3Ü ) less than the length of the remaining leading edge of the leading edge ( 3 ) is. Drill according to claim 8, characterized by a ratio of the length of the transition region ( 3Ü ) to the length of the remaining leading edge of the leading edge ( 3 ) of less than 1. 4th Drill according to claim 8 or 9, characterized in that the transition region ( 3Ü ) from a circumferential chamfering of the open area ( 11 . 11ü ) is formed, preferably with a bevel angle (WF) of 10 ° to 20 °, in particular 15 ° to the axial direction (B). Drill according to claim 10, characterized in that the peripheral free bevel steadily curved is, the curvature (K) is concave to the drill and the increase in the curvature angle to the axial direction preferably increases from the inside to the outside. Drill according to claim 8 or 9, characterized in that the transition area formed by a rounding (R) on the free surface is. Drill according to one of the preceding claims, characterized by circular bevels ( 7 . 17 ; 107 . 117 ) on the leading and trailing bridges ( 8th . 9 ; 108 ; 109 ) with a width (B7, B17; B107, B117) of 10% to 25% of the nominal drill diameter (D), in particular 0.3 to 0.8 mm. Drill according to one of the preceding claims, characterized in that at least in the area of the sharp cutting edges ( 3 . 3Ü . 23 ; 103 . 123 ) a coating is provided, preferably in the form of a hard material layer, the coating preferably being deposited using the CVD process, and the thickness of the layer preferably being in the range between 8 μm and 16 μm, in particular 12 μm. Drill according to claim 14, characterized in that the hard material layer consists of diamond, preferably nanocrystalline Diamond. Drill according to claim 14, characterized in that the hard material layer made of TiN or (Ti, Al) N, a multi-layer layer or a layer consisting of nitrides with the metal components Cr, Ti and A1 and preferably a small proportion of elements Grain refinement exists, the Cr content being 30 to 65%, preferably 30 to 60%, particularly preferably 40 to 60%, of the Al content 15 to 35%, preferably 17 to 25%, and the Ti content at 16 up to 40%, preferably 16 to 35%, particularly preferably 24 to 35 %, is based on all metal atoms in the entire layer. Drill according to claim 14, characterized in that the construction of the entire layer from a homogeneous mixed phase consists. Drill according to claim 15 or 17, characterized in that the structure of the entire layer consists of a plurality of individual layers which are homogeneous and which alternately consist of (Ti _x Al _y Y _z ) N with x = 0.38 to 0.5 and y = 0.48 to 0.6 and z = 0 to 0.04 and on the other hand consist of CrN, the top layer of the wear protection layer preferably being formed by the CrN layer. Drill according to one of the preceding claims, characterized characterized in that at least in the area of the grooves, a soft material coating, preferably from MoS2 is provided. Drill according to one of the preceding claims, characterized characterized that the nominal diameter (D) of the drill in the range from 3 - 30 mm lies. Drill according to one of the preceding claims, characterized through a rejuvenation the drill from the drill tip in the axial direction along the Drill that 25% - 80 % of the usual drill taper that is is preferably in the range of 0.02-0.4 mm, so that the Rejuvenation especially is preferably about 0.04 mm per 100 mm length. Drill according to one of the preceding claims, characterized by a spiral angle that is in the range of 20 ° - 40 °.