Machining tool comprising a hard material layer, and method for manufacturing same

Abstract

The present invention relates to a machining tool (1) for machining extremely hard materials, and to a method for manufacturing same. Such a machining tool comprises a cemented carbide main body which is rotationally symmetrical with respect to a rotational axis (z) and which has a front end (20) and a shank (10) designed to be clamped into a tool holder of a machine tool. The front end is formed as a rotationally symmetrical tool tip (20). This tool tip (20) is thus formed integrally with the shank (20) of the cemented carbide main body. At least one hard material layer (24), such as a diamond layer, is applied over the entire surface of the tool tip (20). A plurality of flutes (25) having cutting edges (30) extend within the hard material layer (24), said flutes being introduced into the hard material layer (24) exclusively by means of laser machining.

Description

[0001] ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0002] August 2025

[0003] -1-

[0004] Description

[0005] Machining tool with hard material coating and method for its manufacture

[0006] Technical field

[0007]

[0001] The present invention relates to a cutting tool for machining extremely hard materials such as, for example, cemented carbide or ceramics. Ceramics include, for example, SiC, Al₂O₃, or ZrO₂. Other extremely hard materials that can be machined with tools according to the invention are non-carbon materials such as, for example, copper and brass or alloys thereof.

[0008]

[0002] Furthermore, the present invention relates to a method for manufacturing cutting tools of the aforementioned type.

[0009]

[0003] It should be noted at the outset that cutting tools according to the present invention are designed in particular as milling tools.

[0010] background

[0011]

[0004] Nowadays, cutting tools such as shank,

[0012] Torus, ball-head, circular segment, or barrel end mills are manufactured from carbide round bars by grinding. Grinding creates the outer contour of the tool tip suitable for the tool's machining type and also produces the necessary flutes and cutting edges in the tool tip.

[0013] Tools ground in this way are then coated in the area of ​​the tool tip with the flutes and cutting edges with a hard material layer, e.g. diamond, using known coating processes.

[0014] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0015] August 2025

[0016] -2-

[0017]

[0005] This method of manufacturing cutting tools is affected by the problem that, due to the thermal process during coating and the heat distribution within the carbide, uneven layer growth occurs. As a result, the layer thickness can unintentionally decrease along the cutting edge towards the shank.

[0018]

[0006] Furthermore, the application of the hard material layer increases the

[0019] Cutting edges become rounded, and the machining properties can change significantly, especially with small tool diameters such as less than 1 mm. Tools that are resharpened after coating using laser technology or other methods are expensive and time-consuming; see, for example, US 2004 / 0142644 Al.

[0020]

[0007] Furthermore, the original ground chip groove and

[0021] The cutting edge geometry is not accurately reproduced. This problem is particularly pronounced when combined with changes in layer thickness.

[0022]

[0008] Furthermore, the known hard material layers exhibit, due to the

[0023] Pretreatments often cause problems with coating adhesion. Dissolving the binder during pretreatment can weaken the surface layer, increasing the risk of coating shearing off under higher forces during tool use. In particular, changes in coating growth along the cutting edge often lead to complete coating removal and exposure of the carbide substrate when the cutting edge is sharpened. This renders the tools unusable, and they must be destroyed.

[0024]

[0009] Finally, a certain material removal volume must be taken into account in order to produce the desired chip groove and cutting edge geometry by grinding. However, the rotating grinding wheels used do not allow for the precise creation of smaller chip grooves.

[0025] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0026] August 2025

[0027] -3-

[0028]

[0010] EP 2 314 412 B2 discloses a method for producing cutting edges from a blank. However, this known method is only proposed for machining cutting inserts or tools with brazed diamond inserts. The blank used here consists, for example, of PCD or CVD, which is brazed onto a substrate layer or applied directly thereto as a layer.

[0029]

[0011] The technical problem underlying the invention is to remedy or at least reduce one or more of the aforementioned defects.

[0030] Summary of Revelation

[0031]

[0012] According to a first aspect, the aforementioned technical problem is solved by a cutting tool designed for machining very hard materials. Such a cutting tool comprises a rotationally symmetrical carbide body, which has a front end and a shank intended for clamping in a tool holder of a machine tool. A rotationally symmetrical carbide tool tip is formed integrally with the front end of the carbide body. In other words, the tool tip and the carbide body are formed from a single carbide blank. For example, a round carbide bar is ground such that the tool tip has an outer contour suitable for forming an end mill, torus cutter, ball nose cutter, or circular segment or barrel cutter. This outer contour, however, does not have any flutes or cutting edges, but is flat, i.e.,The tool tip is ground according to the desired contour. Furthermore, according to the present invention, at least one hard material layer is applied over the entire surface of the pre-formed tool tip and forms a

[0032] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0033] August 2025

[0034] -4-

[0035] Machining section. The thickness of the at least one hard material layer can be, for example, a uniform 3–30 µm. This machining section comprises a multitude of chip flutes with cutting edges, extending into the hard material layer and created by laser machining. Depending on the tool, the chip flutes can also extend into the carbide body.

[0036]

[0013] According to a second aspect, the aforementioned technical problem is also solved by a method according to the invention for manufacturing a cutting tool for machining very hard materials. Such a method comprises providing a one-piece rotationally symmetrical carbide base body, which has a front end and a shank designed for clamping in a tool holder of a machine tool. A rotationally symmetrical carbide tool tip is formed at the front end of the carbide base body by machining the carbide base body, e.g., by grinding. However, the outer surface of the ground tool tip does not yet have any ground-in flutes or cutting edges. At least one hard material layer is applied over the entire surface of the tool tip formed in this way and forms a machining section.The at least one hard material layer of this intermediate product, manufactured from a single-piece carbide blank, is then processed using a laser to form a multitude of chip flutes with cutting edges. These chip flutes extend either only within the at least one hard material layer or also into the carbide base. The cutting edges are always formed within the hard material layer using the laser.

[0037]

[0014] The cutting edges are thus produced solely by selectively removing one or, depending on the application, several layers of hard material.

[0038] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0039] August 2025

[0040] -5-

[0041] Chip flutes can either be formed only in the hard material or also extend into the carbide base body. Cutting tools according to the invention therefore have geometrically defined, sharp cutting edges. And the adhesion of the hard material coating is at least less impaired than in the prior art.

[0042]

[0015] An advantageous further embodiment of the present invention provides that a carbide round bar is provided, which is preferably formed by grinding or turning to create a tool tip having an outer contour suitable for forming a milling cutter, e.g., an end mill, torus cutter, ball nose cutter, or circular segment or barrel cutter. Alternatively to grinding or turning, known EDM or milling processes can also be used to form the desired tool tip contour or outer contour.

[0043]

[0016] After producing the desired outer contour of the tool tip, the contour of the tool tip produced by grinding is then coated with at least one hard material layer. For this purpose, reference is made, for example, to EP 2 230 327 Al.

[0044]

[0017] If expedient, an intermediate step can also be carried out beforehand in which one or more adhesion promoter layers are applied before the hard material layer is applied to the adhesion promoter. The adhesion promoter may improve the adhesion of the hard material layer to the tool tip if the adhesion and thus the

[0045] The peel strength of the hard coating on the tool syringe must be increased to withstand the forces occurring during the use of the tool.

[0046]

[0018] A cutting tool according to the present invention is thus characterized in that it is a one-piece or one-part

[0047] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0048] August 2025

[0049] -6-

[0050] The carbide blank is shaped to reflect the desired cutter shape or tool tip surface. Then, the entire surface of the tool tip intended for milling is coated with a hard coating. This hard coating can be, for example, a diamond layer applied using CVD or PVD processes. Of course, any other known material suitable for hard coatings can also be used as the hard coating.

[0051]

[0019] The applied hard material layer is then processed using a laser to create the desired geometry of the flutes and cutting edges suitable for the respective milling operation. No further post-processing is then necessary. The laser processing of the hard material layer is carried out, for example, using laser processing machines from Rollomatic. Thus, the laser processing of the hard material layer selectively removes material from the hard material layer. The laser processing allows the flutes to extend continuously to the shank in the desired three-dimensional shape – as with known milling cutters or finishing tools. The flutes produced with the aid of the laser therefore also have the desired sharp cutting edges. If necessary, undercuts can also be produced in the same operation.The core of the present invention also consists in the fact that chip grooves and cutting edges are created directly in the hard material layer by means of laser ablation, which have the desired shape and sharpness without the need for post-processing.

[0052]

[0020] In an exemplary embodiment of the present invention, cutting grooves and the associated cutting edges extend radially from the tool tip towards the shank. The cutting edges preferably extend at a helix angle of 2°–60°, preferably 20°–40°, to the axis of rotation of the cutting tool.

[0053] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0054] August 2025

[0055] -7-

[0056] A helix angle of at least 2° may be necessary to guide the laser beam out of the material with the focus point, without accidentally machining the shaft with the laser beam. A helix angle of more than 60° is likely no longer practical for milling, as the wedge angle of the produced tooth becomes too small in the extremely hard materials and the tool may begin to break.

[0057]

[0021] In an exemplary embodiment of the present invention, the flutes have a width along the arc length of 60–500 pm, depending on the number of cutting edges and the diameter of the machining tool, i.e., the tool tip with the flutes and cutting edges. The arc length (e) determines the strength of the cutting edge. If it is too short, the coating will be detached from the cutting edge due to the shear forces that occur. If the arc length is too long, not enough teeth can be incorporated into the tool. With a ratio between the tooth width c and the arc length e of 0.15 <c / e < 0,28 kann das Werkzeug einen duktilen Schnitt ausführen ohne zu drücken. Dadurch werden z.B. Kantenausbrüche bei der Bearbeitung von Keramiken vermieden. Zusätzlich weist die Beschichtung am Punkt c eine Schichtstärke b auf, die geringer ist als die Schichtstärke a an der Schneidkante.

[0058]

[0022] In an exemplary embodiment of the present invention, the flutes have a flute depth between 10-1000 pm.

[0059]

[0023] In another exemplary embodiment of the present invention, a radius of 20–100 pm is incorporated within each groove. Sharp-edged contours are not feasible due to manufacturing constraints and would also act as a predetermined breaking point. However, a radius in the range of 20–100 pm provides the best profile for shaping the groove. A preferred ratio of arc length d to groove radius r is 0.07. <r / d<0,35.

[0060] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0061] August 2025

[0062] -8-

[0063]

[0024] In another exemplary embodiment of the present invention, the included angle between two cutting edges is 2°–120°, preferably for a tool with a diameter of 6 mm. A tool with a diameter of 6 mm and 42 cutting edges has an included angle of 8.57°. The more teeth are incorporated around the circumference, the smaller the angle becomes, and the shallower the chip groove. At the same time, there are more cutting edges available for material removal, which improves wear distribution and enables better chip formation in ductile hard machining.

[0064]

[0025] In a further exemplary embodiment of the present invention, the thickness of the fully applied hard material layer is between 3 and 40 pm, and in particular between 10 and 30 pm. Preferably, the hard material layer is a diamond layer deposited by a known CVD process. The individual diamond layer can be in any coating form, i.e., nanocrystalline, in a multilayer variant, or as is otherwise known in the prior art.

[0065]

[0026] In a further exemplary embodiment of the present invention, the tool tip with the hard material layer applied thereto has an outer surface shape that is suitable and intended for the formation of an end mill, torus cutter, ball nose cutter, or circular segment or barrel cutter. These are fundamentally tool shapes that engage primarily in the area of ​​the diameter cutting edge or in the radius area.

[0066]

[0027]

[0067] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0068] August 2025

[0069] -9-

[0070] Brief description of the drawings

[0071]

[0028] Exemplary embodiments of the present invention are described and explained in more detail with reference to the following figures. They show:

[0072]

[0029] Fig. 1 shows a side view of a first embodiment of a cutting tool according to the invention, which is shaped like a circular segment or torus milling tool,

[0073]

[0030] Fig. 2 shows a perspective view of the machining tool according to the invention according to Fig. 1 with cutting grooves and cutting edges introduced into the hard coating by means of a laser,

[0074]

[0031] Fig. 3a shows a top view of the tool tip of the cutting tool shown in Figs. 1 and 2,

[0075]

[0032] Fig. 3b shows a detailed view of the cutting plan view of the tool tip of the cutting tool shown in Figs. 1 and 2,

[0076]

[0033] Fig. 4 shows a perspective side view of a second embodiment of a cutting tool according to the invention, which is designed as a circular segment cutter,

[0077]

[0034] Fig. 5 shows a perspective view of a third embodiment of a cutting tool according to the invention, which is designed as a ball end mill.

[0078] Detailed description

[0079]

[0035] A first exemplary cutting tool according to the present invention is described in more detail below with reference to Figs. 1 to 3.

[0080]

[0036] The cutting tool 1 shown in Figures 1 to 3 consists of a round bar 5 which is rotationally symmetric about an axis of rotation z. In the front region of the round bar 5, it has an original radius n

[0081] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0082] August 2025

[0083] -10- reduced to a radius r2 and forms a tool tip 20. The reduction of the round bar 5 in the area of ​​the tool tip 20 to the radius n was achieved by grinding.

[0084]

[0037] As can be seen directly in Fig. 1, the tool tip 20 is formed with a shank 10 of the cutting tool 1 by means of a conical transition area 15. The transition area 15 was also formed by grinding the round bar 5. It should be emphasized that in this embodiment, the entire round bar is formed in one piece and made of a hard metal such as EMT100 from Extramet. This is a fine-grained hard metal with a grain size of approximately 0.8 pm and a co-binder content of approximately 6%.

[0085]

[0038] The tool tip 20 is given a desired rotationally symmetrical outer surface 22 with the corresponding contour for the desired milling cutter type by grinding and possible finishing. Depending on the milling tool 1 to be manufactured, the outer surface 22 of the tool tip 20 is thus, for example, conical, cylindrical, barrel-shaped, or shaped as for ball end mills or torus end mills.

[0086]

[0039] In Fig. 1, the original shape of the hard metal round bar is shown with dashed lines and has radius n. The outer contour produced after grinding is shown in solid form in Fig. 1.

[0087]

[0040] After grinding the round bar 5 into the outer contour shown in Fig. 1, the tool tip 20, or rather its outer surface 22, is completely coated with a diamond layer 24 using a known CVD coating process. This hard coating 24 is clearly visible, for example, in Fig. 3 and is shown with its original outer contour 20' as a dashed line. In the embodiment shown here, the tool tip 22 has radius n. The hard coating 24 therefore has a thickness that is determined by the difference between the outer radius G and the thickness of the tool tip 22.

[0088] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0089] August 2025

[0090] -11- after coating and the radius r2, which results after grinding the round bar 5.

[0091]

[0041] As an intermediate product, a one-piece round bar 5 with shaft 10, transition area 15 and a tool tip 20 coated with hard material 24 is now available.

[0092]

[0042] This intermediate product is then processed in a laser processing machine with three-dimensional positioning capability of the intermediate product using a laser. Machines from the manufacturer Rollomatic, for example, are used here.

[0093]

[0043] In such a laser processing machine, the hard material layer 24 is now removed three-dimensionally at desired locations using the laser in order to produce the chip grooves 25 and cutting edges 30 suitable for the respective milling cutter type.

[0094]

[0044] By selectively removing the hard material layer 24 in specific areas, a multitude of flutes 25 and cutting edges 30 can be formed distributed across the entire tool tip 20. Post-processing of the flutes 25 or cutting edges 30 is not strictly necessary, since for the first time the desired three-dimensional cutting edges 30 with the necessary sharpness are generated directly in the hard material 24. The lines and patterns of the flutes 25 and cutting edges 30 can be the same as those of known cutting tools, i.e., milling cutters or finishing tools.

[0095]

[0045] Figure 3b shows a detailed view of the flutes according to Figure 3a. The arc length e determines the strength of the cutting edge. If it is too short, the coating will be detached from the cutting edge due to the shear forces that occur. If the arc length e is too long, not enough teeth can be incorporated into the tool. With a ratio between the tooth width c and the arc length e of 0.15 <c / e < 0,28 kann das Werkzeug einen duktilen Schnitt ausführen ohne zu drücken. Dadurch werden z.B.

[0096] UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW

[0097] August 2025

[0098] -12-

[0099] Edge chipping during the processing of ceramics is avoided. Additionally, the coating at point c has a layer thickness b that is less than the layer thickness a at the cutting edge.

[0100]

[0046] When machining technical ceramics or hard metals with this type of tool, a shallow groove depth is sufficient due to the ductile cutting behavior and the associated small chip thicknesses. The advantage here is that the coating remains intact over the entire circumference, see, for example, Figures 3a and 3b. When machining long-chipping materials such as copper, a groove depth of 10 µm is insufficient. For better chip management, the coating and material must be removed from the base material. Here, the previous point regarding the arc length must be taken into account. The ratio of the groove depth e to the arc length d is then preferably 0.03 <e / d < 0,2.

[0101]

[0047] A flute radius r in the range of 20–100 pm shows the preferred profile for shaping the flute profile. A preferred ratio of arc length d to the flute radius r is 0.07. <r / d<0,35.

[0102]

[0048] Figures 4 and 5 show alternative shapes or contours of a cutting tool 1 according to the invention after grinding and coating, but before laser processing. Figure 4 shows a circular segment milling cutter h with shank IO2, transition area 152, and tool tip 2O2 in perspective. As mentioned, the tool tip 2O2 is already coated with hard material 24, but has not yet been laser-machined to produce the flutes 25 and cutting edges 30. Accordingly, the tool tip 2O2 only has the outer contour desired for a circular segment milling cutter.

[0103]

[0049] In Fig. 5, a ball end mill I3 with shank 103, transition area 153 and tool tip 2O3 is shown in perspective. As previously described for Fig. 4, the tool tip 2O3 is also already equipped with

[0104] UP / UP / ae ZECEIA Eiartmetall- Werkzeugfabrikation GmbEi ZEC050-38885DE-NW

[0105] August 2025

[0106] -13-

[0107] The hard material 24 is coated, but not yet laser-machined to produce the flutes 25 and cutting edges 30. Accordingly, the tool tip 20s only has the outer contour required for a ball end mill.

[0108] UP / UP / ae

Claims

ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW August 2025 -14- Patent claims 1. Cutting tool (1) for machining high-hard materials, comprising: a carbide base body rotationally symmetrical about an axis of rotation (z), which has a front end (20) and a shank (10) designed for clamping in a tool holder of a machine tool; wherein the front end is formed as a rotationally symmetrical tool tip (20) and this carbide tool tip (20) is thus formed in one piece with the shank (20) of the carbide base body, at least one hard material layer (24) which is applied over the entire surface of the tool tip (20) and forms a machining section, and a plurality of cutting edge flutes (25) which extend in the at least one hard material layer (24) and are introduced into the hard material layer (24) solely by means of laser processing.

2. Cutting tool (1) according to claim 1, wherein the cutting edges (30) extend radially from the tool tip (20) in the direction of the shank (20).

3. Cutting tool (1) according to claim 1 or 2, wherein the cutting edges (30) extend at a helix angle of 2°-60° to the axis of rotation (z) of the cutting tool (1).

4. Cutting tool (1) according to one of the preceding claims, wherein the flutes (25) are selected according to the number of cutting edges and UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW August 2025 -15- with a tool diameter of 0.3 to 12 mm, have a width along the arc length of 60-500 pm.

5. Cutting tool (1) according to one of the preceding claims, wherein the flutes (25) have a flute depth between 10-1000 pm.

6. Cutting tool (1) according to one of the preceding claims, wherein a radius of 20 - 100 pm is formed within the flutes (25).

7. Cutting tool (1) according to one of the preceding claims, wherein the enclosed angle between two cutting edges is 2°- 90°.

8. Cutting tool (1) according to one of the preceding claims, wherein the thickness of the hard material layer (24) is between 3 - 40 pm and in particular between 10 - 30 pm and the hard material layer (24) is preferably a diamond layer deposited by CVD process.

9. Cutting tool (1) according to one of the preceding claims, wherein the tool tip (20) and thus also the hard material layer (24) applied thereto has an outer surface shape (22) which is intended to form an end mill, torus cutter, ball nose cutter or circular segment or barrel cutter.

10. Cutting tool (1) according to one of the preceding claims, wherein the hard metal body is formed by grinding or turning a hard metal round bar with the desired outer contour. UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW August 2025 -16- 11. Method for manufacturing a cutting tool (1) for machining high-hard materials, comprising: Providing a rotationally symmetrical carbide base body (5) which has a shank (10) designed for clamping in a tool holder of a machine tool and a rotationally symmetrical carbide tool tip (20) adjoining it, on which at least one hard material layer (24) is applied over the entire surface and forms a machining section, and Machining the at least one hard material layer (24) on the tool tip (20) using a laser such that a plurality of cutting edges (30) are formed chip grooves (25).

12. Method according to claim 11, wherein the machining of the hard material layer (24) and thus the production of the chip grooves (25) is carried out in the direction of the axis of rotation (z) starting from the tool tip (20).

13. Method according to claim 11 or 12, comprising the further process steps: Providing a hard metal round bar, Removal of material by, for example, grinding or turning the carbide round bar in such a way that a tool tip (20) is formed with the outer contour suitable for forming an end mill, torus cutter, ball nose cutter or circular segment or barrel cutter, and full-surface coating of the outer contour of the tool tip (20) produced by grinding with the hard material layer (24). UP / UP / ae ZECHA Hartmetall- Werkzeugfabrikation GmbH ZEC050-38885DE-NW August 2025 -17- 14. Method according to one of claims 11-13, wherein the hard metal base body with the shank (10) and the tool tip (20) with hard material layer (24) applied thereto is positioned in the laser processing machine such that the chip flutes (25) and the cutting edges (30) can be produced with the desired helix angle.

15. Method according to one of claims 11-14, wherein one or more adhesion promoter layers are applied to the contoured tool tip before the application of the at least one hard material layer (24). UP / UP / ae

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