Abstract
A method for producing a tool for machining a workpiece. A metal tool blank is provided in a laser machining device which structures the tool blank on a tool surface via interference from at least two laser beams. The at least two laser beams have at least temporary pulse durations of at most 15 ps, and via the structuring on the tool surface a tool profile is generated having at least one indentation. A tool structured in this manner, a method for machining a workpiece via the tool, and a workpiece machined in this way, are also provided.
Claims
1. A method for producing a tool to machine a workpiece, in particular a punching or forming tool, the method comprising: providing a metal tool blank in a laser machining device; and structuring, via the laser machining device, a tool surface of the tool blank via interference of at least two laser beams, the at least two laser beams having at least temporary pulse durations of at most 15 ps, wherein a tool profile having at least one indentation is produced on the tool surface by the structuring.
2. The method according to claim 1, wherein the at least one indentation is produced with a dimension or with a depth with respect to an unstructured region of the tool surface of between 10 nm and 50 m or between 100 nm and 15 m.
3. The method according to claim 1, wherein at least two indentations having substantially identical dimensions or having substantially identical depths are produced.
4. The method according to claim 1, wherein at least one group of indentations is produced in a periodic pattern on the tool surface.
5. The method according to claim 4, wherein the group of indentations in the periodic pattern on the tool surface is produced having a lateral period between 10 nm and 50 m, or between 100 nm and 15 m in at least one direction along the tool surface.
6. The method according to claim 1, wherein at least one group of indentations is produced on the tool surface having a linear course and/or a rectangular, square, basic shape and/or a circular basic shape.
7. The method according to claim 1, wherein at least two first indentations or a first group of indentations are produced having a first lateral period between 10 nm and 50 m or between 100 nm and 15 m, wherein at least two second indentations or a second group of indentations are produced having a second lateral period, and wherein the second lateral period is smaller than the first lateral period.
8. The method according to claim 7, wherein the region of the second indentations or the second group of indentations at least partially overlaps the region of the first indentations or the first group of indentations.
9. The method according to claim 7, wherein the first indentations or the first group of indentations and the second indentations or the second group of indentations are created in a single work step or in separate work steps.
10. The method according to claim 9, wherein the first indentations or the first group of indentations are produced via interference of the at least two laser beams, and wherein the second indentations or the second group of indentations are created via interference of at least two laser beams and/or via a single laser beam.
11. The method according to claim 1, wherein the tool blank is coated before being structured and/or wherein the tool is coated after being structured.
12. A tool, in particular a punching or forming tool, structured in accordance with the method according to claim 1.
13. The tool according to claim 12, wherein the tool has at least one component made of a hard metal which has a plurality of hard material particles and a binder matrix, and/or at least one component made of a thermally treated tool steel.
14. The tool according to claim 12, wherein the tool has a hard material layer, or a carbon layer, or a tetrahedral, hydrogen-free carbon layer, at least in some regions of the tool surface.
15. A method for machining a workpiece via a tool according to claim 12, the method comprising: plastically deforming the workpiece at least in some regions via the tool; and providing the tool with a workpiece profile which corresponds to the tool profile, at least in some regions.
16. The method according to claim 15, wherein the workpiece is plastically deformed via the tool in at least two machining steps, the tool plastically deforming the workpiece along a machining axis with a first machining depth in a first machining step and, in a second machining step, the tool plastically deforming the workpiece along the machining axis with a second machining depth, and wherein the first machining depth differs from the second machining depth.
17. The method according to claim 16, wherein the first machining step is carried out using a first tool and the second machining step is carried out using a second tool.
18. The method according to claim 17, wherein the second tool has a periodic structure having a lateral period which is smaller than the lateral period of the periodic structure of the first tool.
19. The method according to claim 16, wherein the press-in pressure in one machining step differs from the press-in pressure in another machining step.
20. The method according to claim 15, wherein the workpiece is plastically deformed via a vibrational movement of the tool along the machining axis, or wherein the workpiece is machined via the tool at a temperature of at most 1200 C., without any heat being externally input.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
[0045] FIG. 1 shows a schematically illustrated example of the method according to the invention for producing a tool and a tool according to the invention,
[0046] FIG. 2 shows a schematically illustrated example of the method according to the invention for machining a workpiece and a workpiece according to the invention,
[0047] FIG. 3 shows an example of the method according to the invention for producing a tool and a tool according to the invention,
[0048] FIG. 4 shows an example of the method according to the invention for machining a workpiece and a workpiece according to the invention,
[0049] FIG. 5 shows an example of the method according to the invention for producing a tool and a tool according to the invention,
[0050] FIG. 6 shows an example of the method according to the invention for machining a workpiece and a workpiece according to the invention,
[0051] FIG. 7 shows an example of the method according to the invention for producing a tool and a tool according to the invention,
[0052] FIG. 8 shows an example of the method according to the invention for machining a workpiece and a workpiece according to the invention,
[0053] FIG. 9 shows an example of the method according to the invention for producing a tool and a tool according to the invention,
[0054] FIG. 10 shows an example of the method according to the invention for machining a workpiece and a workpiece according to the invention,
[0055] FIGS. 11 to 14 show examples of the method according to the invention for producing a tool, of the tool according to the invention, as well as a further example of the method according to the invention for machining a workpiece and of the workpiece according to the invention,
[0056] FIGS. 15 and 16 show an example of the method according to the invention for machining a workpiece and of the workpiece according to the invention, and
[0057] FIGS. 17 and 18 show an example of the method according to the invention for machining a workpiece and of the workpiece according to the invention.
DETAILED DESCRIPTION
[0058] FIG. 1 shows an example of the method according to the invention for producing a tool 10 using three images of the tool 10. In the left-hand illustration in FIG. 1, the tool 10 is arranged in an unmachined state as a tool blank 11, which, in the example shown, is substantially a cylinder made of a tungsten carbide-cobalt hard metal (WCCo) and was manufactured via spark erosion. The workpiece 12 is to be subsequently machined by the top surface 13 of the tool 10 so that the top surface 13 of the tool blank 11 is provided with a coating made of an amorphous carbon, which is also referred to as diamond-like carbon (DLC).
[0059] For the production of the tool 10 according to the invention, the tool blank 11 is provided in a laser machining device 14, which is shown only schematically in the central illustration of FIG. 1 for reasons of clarity. The laser machining device 14 has an optics module 15 which, in the example shown in FIG. 1, splits an incident laser beam into two partial beams 17, 18 and directs them in the direction of the top surface 13 of the tool blank 11 to be structured as the tool surface 13. Depending on the application, up to nine laser beams can be used as partial beams. In the example shown, pulsed laser radiation with temporal pulse durations of 1 ps, i.e. ultrashort pulses, and with a pulse energy of 100 J is used. The two partial beams 17, 18 directed in the direction of the tool blank 11 are oriented at a finite angle to one another such that the partial beams 17, 18 interfere with one another in an interference region 19. The tool blank 11 is arranged in the laser machining device 14 such that the interference region 19 is arranged substantially on the top surface 13 of the tool blank 11 as a working surface. The interference pattern formed by the interfering partial beams 17, 18 depends substantially on the angle formed by the partial beams 17, 18, their polarization and the wavelength of the laser radiation used, so that by changing these parameters the interference pattern can be adapted as required. The top surface 13 of the tool blank 11 is structured by the incident partial beams 17, 18 that interfere with one another, wherein the structuring substantially corresponds to the intensity maxima of the interference pattern. By using ultrashort pulsed laser radiation, the tool 10 is substantially structured, and thus produced, purely ablatively, i.e. without heat being introduced into the top surface 13 of the tool blank 11, since the pulse duration of the laser radiation is so short that no thermal interaction between the laser radiation and the material of the tool blank 11 occurs. In this respect, this type of machining is also called cold ablation. This allows comparatively fine structural patterns to be realized in the micro- and/or nanoscale range while simultaneously avoiding thermal damage to the tool. Due to the partial beams 17, 18 that interfere with one another, topographical structures are formed in the interference region 19 so as to structure the top surface 13 of the tool blank 11. In the example shown, 50 pulses are superimposed for structuring purposes.
[0060] If structuring of the tool blank 11 beyond the interference region 19 of the partial beams 17, 18 is desired, the tool blank 11 can be moved relative to the interference region 19, which includes movements in a translational and/or rotational manner and is illustrated by the arrows shown in gray in FIG. 1. For this purpose, the laser machining device 14 is designed such that the interference region 19 of the partial beams 17, 18, which in this respect corresponds to a region of focus, is movable relative to the top surface 13 of the tool blank 11 to be structured. For example, this is done by deflecting the two partial beams 17, 18 via mirrors actuated by servo motors in the sense of an F-Theta lens. Alternatively or additionally, the tool blank 11 can be moved in a translational manner, for example by linear guides. Via a corresponding guide, rotation of the tool blank 11 relative to the laser machining device is also possible in this way, in particular about its axis of extension. By moving the interference region 19 relative to the top surface 13 of the tool blank 11, structuring of the top surface 13 beyond the interference region 19 is possible by successively machining the top surface 13 via the interfering partial beams 17, 18, in particular by scanning part or all of the surface thereof.
[0061] In the example in FIG. 1, the structuring leads to a tool profile 20 of the tool 10, thus to a surface topography, with linear structural elements 21, which are shown greatly enlarged in the right-hand illustration in FIG. 1 for reasons of clarity. The tool profile 20 of the top surface 13 of the tool 10 perpendicular to the direction of extension of the structural elements 21 approximately corresponds to a sinusoidal course, in which indentations 22 and elevations 23 of equal size are arranged one behind the other at a fixed distance d, which is referred to as the lateral period in the sense of the invention, and wherein there is a continuous transition between each of the indentations 22 and elevations 23; this is illustrated in FIG. 1 by solid lines. The lateral period d between an indentation 22 and an indentation 22 adjacent thereto is 10 m in the example shown. The elevations 23 are arranged in the same lateral period d. The tool 10 shown on the right in FIG. 1 is provided with linear structural elements 21 over its entire top surface 13 and is thus finished.
[0062] The finished tool 10 shown on the right in FIG. 1 is then used as a stamping tool or die in a stamping device and is placed opposite the workpiece 12 to be machined so that the top surface 13 of the tool 10 faces the workpiece 12. In the example in FIG. 2, the workpiece 12 is a sheet of brass (CuZn30). By pressing the tool 10 having the above-mentioned tool profile 20 onto the workpiece 12 with a contact pressure of 1,500 MPa, thus along a machining axis 24 arranged perpendicularly to the workpiece surface 13, the tool profile 20 is at least partially molded onto the workpiece 12 as a plastic deformation, wherein the workpiece 12 is provided with a workpiece profile 25 which corresponds, at least in some regions, to the tool profile 20, in particular is at least partially complementary thereto. In the left-hand illustration in FIG. 2, the machining axis 24 is indicated by a large gray arrow. In the example shown, full-surface structuring of the workpiece 12 is desired, wherein the structured top surface 13 of the tool 10 is significantly smaller than the surface of the workpiece 12 to be structured. Therefore, after this machining step, the tool 10 is moved relative to the workpiece 12, after which stamping is carried out again with the aforementioned contact pressure. This process is then repeated until the entire surface of the workpiece 12 is structured. This process is also called stitching and is illustrated in the left-hand illustration by the small gray arrows. The finished structured workpiece 12 is shown on the right in FIG. 2, from which it can be seen that the workpiece profile 25 is at least partially complementary to the tool profile 20 by the workpiece profile 25 having indentations 22 which are arranged in the same lateral period d as the indentations 22 of the tool profile 20.
[0063] FIG. 3 shows a further possibility for producing a tool 10 having a tool profile 20 which differs from that in the example in FIG. 1. For this purpose, similarly to the example in FIG. 1, the entire top surface 13 of the tool 10 in the form of a tool blank 11 is first provided with a tool profile 20 having linear structural elements 21 as first indentations 22 via the laser machining device 14, and therefore reference is made to the above statements in this regard to avoid repetition. In contrast to the example in FIG. 1, the pulse energy of the laser radiation is 80 J and 20 individual pulses are superimposed for structuring purposes. The resulting first tool profile 20 in the third illustration in FIG. 3 is qualitatively similar to the tool profile 20 according to FIG. 1, but has, in contrast thereto, a smaller lateral period d of 6 m. After this first structuring process, the tool 10 is rotated by 90 about its axis of extension A when transitioning from the third representation to the fourth representation in FIG. 3 and is again provided in the laser machining device 14 so that further structuring of the entire top surface 13 is subsequently carried out with the same parameters as the first structuring process.
[0064] As a result, the tool 10 shown on the right in FIG. 3 has a tool profile 20 with columnar structuring comprising elevations 23 which are arranged one behind the other in a first direction R.sub.1 with a first lateral period d of 6 m and which are also arranged one behind the other in a second direction R.sub.2, which is perpendicular to the first direction R.sub.1, with a second lateral period d also of 6 m. Since each two adjacent elevations 23 of the tool profile 20 are separated by an indentation 22, the tool profile 20 has first indentations 22 in the first direction R.sub.1 arranged in the first lateral period d, and second indentations 22 in the second direction R.sub.2, which are arranged in the second lateral period d, wherein only one lateral period d is shown in FIG. 3. The region of the second indentations 22 overlaps the region of the first indentations 22 and the first indentations and the second indentations 22 are created in separate work steps.
[0065] According to FIG. 4, the tool 10 shown on the right in FIG. 3 is placed opposite the workpiece 12 to be machined as a die, wherein the top surface 13 faces the workpiece 12. The workpiece 12 is machined by the tool 10 at a contact pressure of 1,200 MPa along the machining axis 24 so that the columnar tool profile 20 is molded onto the workpiece 12 so as to partially complement it, with the result that the workpiece 12 has a workpiece profile 25 having indentations 22, which, similarly to the elevations 23 of the tool 10, are each arranged one behind the other in two directions R.sub.1, R.sub.2 that are perpendicular to one another in a lateral period d of 6 m. The entire surface of the workpiece 12 is machined as already described in connection with FIG. 2 in the sense of stitching, which is illustrated by the gray arrows in the left-hand illustration in FIG. 4. The right-hand illustration in FIG. 4 shows the workpiece 12 machined over its entire surface by the tool 10, which workpiece has the workpiece profile 25 already mentioned.
[0066] In the example in FIG. 5, the structuring of the tool 10 as a tool blank 11 takes place in two machining steps, similarly to the example in FIG. 3. First, the cylindrical tool blank 11 made of a tungsten carbide-cobalt hard metal (WCCo) is provided in the laser machining device 14, which structures the top surface 13 of the tool blank 11 with a first group of indentations 22 in a first machining step. This first machining step is carried out by laser radiation with a pulse duration of 100 fs and a pulse energy of 20 J, wherein three partial beams 17, 18, 26 interfere with one another and ten individual pulses are superimposed. Thereafter, the laser machining device 14 is moved relative to the tool blank 11 in such a way that structuring takes place again until the entire top surface 13 of the tool blank 11 is structured and the tool profile 20 shown in the central illustration in FIG. 5 is formed. Due to the structuring parameters mentioned, the tool profile 20 has, after structuring of the tool 10, a periodic arrangement of indentations 22, which are also called sinks, wherein the tool profile 20 has three axes along the top surface 13 of the tool 10, along which the indentations 22 are arranged in the same lateral period d each time, wherein the lateral periods d of the indentations 22 are each 1 m. Within the sense of the invention, this arrangement of indentations 22 is also referred to as a hexagonal arrangement. The tool 10 structured over its entire surface after the first work step is shown in the central illustration in FIG. 5, wherein the dimensions of the indentations 22 are not shown to scale but greatly enlarged for reasons of clarity.
[0067] In a subsequent work step, the tool profile 20 is provided with further structuring, the region of which overlaps the region of the first structuring. For this purpose, the parameters of the laser machining device 14 are changed so that the second structuring is formed via laser radiation with a pulse duration of 100 fs, a pulse energy of 30 J and by two laser beams 17, 18 that interfere with one another, wherein the structuring is formed by superimposing ten pulses before the laser machining device 14 is moved relative to the tool 10 in the manner already mentioned in order to structure the entire surface of the tool 10. The second tool structuring results in the formation of linear structural elements 21 in the form of indentations 22, which are arranged one behind the other in a lateral period d of 2 m. By superimposing the first structuring with the hexagonally arranged indentations 22 in afirstlateral period d of 1 m with the second structuring comprising linear structural elements 21 in asecondlateral period of 2 m, the tool profile 20 comprises periodic, but at the same time also hierarchical structuring, which is shown in the right-hand illustration in FIG. 5, and which has the linear indentations 22 according to the second structuring as the dominant element, wherein, in the regions not machined during the second structuring process, the hexagonal arrangement of the indentations 22 according to the first structuring is formed having a smaller lateral period d compared to the second structuring.
[0068] After the tool profile 20 has been provided with the hierarchical structuring according to the right-hand illustration in FIG. 5, the tool 10 is placed opposite a sheet of brass (CuZn30) to be stamped as the workpiece 12. The tool 10 then applies a contact pressure of 3,500 MPa along the machining axis 24 to the workpiece 12, wherein the tool 10 is vibrated as a die at a frequency in the ultrasonic range in order to optimize the molding process. This results in the tool profile 20 being completely molded onto the workpiece 12, which thus has a workpiece profile 25 that is complementary to the tool profile 20. Due to the smaller surface of the tool 10 compared to the surface of the workpiece 12, full-surface structuring of the workpiece 12 is carried out by successively moving the tool 10 relative to the workpiece 12 in the sense of the stitching process already mentioned, which is shown in the left-hand illustration in FIG. 6 by the gray arrows. The finished workpiece 12 structured over the entire surface thereof is shown on the right in FIG. 6, wherein the workpiece profile 25 is designed to be complementary to the tool profile 20, as already mentioned.
[0069] FIG. 7 shows an example of the method for producing the tool 10 by structuring a cylindrical tool blank 11 made of a tungsten carbide-cobalt hard metal (WCCo), in which the latter is provided in the laser machining device 14 in a similar manner to in the previous examples. Structuring is carried out using linearly polarized laser radiation with a pulse duration of 5 ps and a pulse energy of 50 J, wherein 200 pulses are superimposed for structuring purposes. According to the left-hand illustration in FIG. 7, it can be seen that the structuring is carried out via two partial beams 17, 18 which interfere with one another, wherein the linear polarization P of the partial beams 17, 18 is selected in each case such that the polarization plane is parallel to the top surface 13 of the tool blank 11 to be structured. Due to the structuring of the tool blank 11, the tool profile 20 has sinusoidal, linear structural elements 21 as a group of indentations 22, which are arranged one behind the other in a lateral period d of 6 m, similarly to in the example in FIG. 1.
[0070] In the example in FIG. 7, thisprimarystructuring is superimposed by a furthersecondarystructuring, which is formed due to the polarization of the partial beams 17, 18 interfering with one another. This secondary structuring is formed due to the linear polarization of the partial beams 17, 18 described above and causes the additional generation of structural elements 21, which are also linear, as a further group of indentations 22, which have structural sizes, in particular a lateral period d, which approximately corresponds at most to the wavelength of the laser radiation used. The indentations 22 of the secondary structuring are arranged substantially at an angle of 0 to the linear polarization of the partial beams 17, 18 and at an angle of 90 to the indentations 22 of the primary structuring. The directions of extension of the linear structural elements 21 of the secondary structuring are therefore substantially perpendicular to the polarization of the partial beams 17, 18. The generation of the first group of indentations 22 as primary structuring and the second group of indentations 22 takes place in a single work step by the above-mentioned superposition of 200 pulses and due to the polarization of the partial beams 17, 18. The entire surface of the tool 10 is structured in the manner already mentioned; the tool 10 with structuring over the entire surface thereof is shown in the right-hand illustration in FIG. 7.
[0071] Using the tool 10 produced according to FIG. 7, a sheet of brass (CuZn30) is then machined as a workpiece 12 according to the left-hand illustration in FIG. 8 by pressing the tool 10, as a die, onto the workpiece 12 with a contact pressure of 2,000 MPa along the machining axis 24, wherein at the same time the tool 10 is vibrated along the machining axis 24 at frequencies in the ultrasonic range in order to optimize the molding process. The entire height of the tool profile 20 is thus not molded; rather, said profile is only partially molded as a complementary structure onto the workpiece profile 25, wherein the workpiece profile 25 has the primary structuring comprising the linear structural elements 21 arranged one behind the other in a lateral period d of 6 m and also the secondary structuring superimposed therewith having the linear structural elements 21 arranged perpendicularly to the first structuring having dimensions that are substantially smaller than the wavelength of the laser radiation. To the applicant's knowledge, the creation of thissuperimposedstructuring as the workpiece profile 25 on brass (CuZn30) is not possible with direct machining using laser radiation, but only with the molding process described above, since in the latter case no melting dynamics occur when creating the structuring on the workpiece profile. The machining of the workpiece 12, thus the creation of the superimposed structuring on the workpiece profile 25, takes place in a single pressing or stamping step. The entire surface of the workpiece 12 is then structured in the sense of stitching, as already described. The workpiece 12 is shown on the right in FIG. 8 with structuring over the entire surface thereof.
[0072] FIG. 9 shows an example of the invention, in which the tool blank 11 is structured analogously to the example in FIG. 7, in particular also by laser radiation with a pulse duration of 5 ps and a pulse energy of 50 J. Structuring is carried out via two partial beams 17, 18 that interfere with one another, wherein the linear polarization P of the partial beams 17, 18 is selected each time such that the polarization axes of the partial beams 17, 18 again each form an angle of 0 to the top surface 13 of the tool blank 11 to be structured; in the example in FIG. 7, the polarization axes of the partial beams 17, 18 are therefore each parallel to the top surface 13 of the tool blank 11 and also perpendicular to the polarization axes of the partial beams 17, 18. Analogous to the example in FIG. 7, the tool blank 11 is structured by the superposition of 200 laser pulses. The tool 10 is shown on the right in FIG. 9 with structuring over the entire surface thereof, wherein its tool profile 20 has a primary structuring with a first group of sinusoidal, linear structural elements 21 as indentations 22, which are arranged in a lateral period d of 6 m, and in this respect corresponds to the primary structuring in the example according to FIG. 7. Due to the linear polarization P of the partial beams 17, 18, the tool profile 20 has a secondary structuring with linear structural elements 21 which are superimposed on the primary structure and which are of an order of magnitude that does not exceed the wavelength used. Due to the orientation of the linear polarization vectors P of the partial beams 17, 18, the secondary structuring comprising the linear structural elements 21 as indentations 22 is parallel to the direction of extension of the primary structuring and thus perpendicular to the secondary structuring in the example according to FIG. 7. The tool blank 11 is structured, including the primary and secondary structuring, in a single work step. FIG. 9 shows the tool 10 with structuring over the entire surface thereof on the right.
[0073] With the tool 10 produced according to FIG. 9, according to FIG. 10, the workpiece 12, here, for example, a sheet of brass (CuZn30), is machined and structured, wherein the structuring is carried out by a contact pressure between the tool 10 and the workpiece of 2,000 MPa along the machining axis 24 and simultaneous vibration of the tool 10 along the machining axis 24 with a vibration frequency in the ultrasonic range. This results in the tool profile 20 being partially molded onto the workpiece profile 25, wherein the workpiece profile 25 has a structure that is complementary to the tool profile 20 so that reference is made in this regard to the above description of the tool profile 20 according to FIG. 9. The entire surface of the workpiece 12 is machined via the stitching process already described, which is shown by the gray arrows in the right-hand illustration in FIG. 10. The workpiece 12 is shown on the right in FIG. 10 with structuring over the entire surface thereof.
[0074] FIGS. 11 to 14 show further examples of the invention. According to FIG. 11, a tool blank 11 made of a tungsten carbide-cobalt hard metal (WCCo) is provided, analogously to the example in FIG. 1, with a tool profile 20 having linear structural elements 21 as indentations 22 with a lateral period d of 10 m. With the tool 10 thus produced, a sheet of brass (CuZn30) as the workpiece 12 is then machined over the entire surface thereof in a first machining step, as already described in connection with FIG. 2, wherein, unlike in the example in FIG. 2, a contact pressure of 1,000 MPa is now used along the machining axis 24. The workpiece 12 is shown on the right in FIG. 12 with structuring over the entire surface thereof.
[0075] After the entire surface of the workpiece 12 has been structured, the tool 10 is rotated by 90 about its axis of extension A according to FIG. 13 such that the linear structural elements 21 are now perpendicular to the structural elements 21 of the workpiece 12. This is shown in the right-hand illustration in FIG. 13. In this orientation, the tool 10 applies a contact pressure of 1,000 MPa along the axis of extension 24 to the workpiece 12 in a second machining step so that superimposed structuring of the workpiece 12 is formed as a workpiece profile 25, which can be seen as a checkerboard pattern in the example shown. The left-hand side of FIG. 14 shows the workpiece 12, the surface of which has not yet been completely structured in the second machining step. The full-surface structuring of the workpiece 12 is achieved by the stitching process already explained; the workpiece 12 is shown on the right in FIG. 14 with structuring over the entire surface thereof. Thesuperimposedstructuring of the workpiece profile 25 is therefore obtained by a single tool 10 having a single, primary structuring in two successive machining steps, wherein the tool 10 is rotated by 90 about its axis of extension A between the machining steps.
[0076] FIGS. 15 and 16 show a further example of the invention, which is based on a tool 10 according to FIG. 1 with a fully structured surface and which is shown in the left-hand illustration in FIG. 15. In this respect, the tool profile 20 has linear structural elements 21 as indentations 22 with a depth of 10 m with respect to the unstructured region of the top surface 13, wherein the indentations 22 are arranged one behind the other in a lateral period d of 10 m. A sheet of brass (CuZn30) as the workpiece 12 is subjected to a first contact pressure of 1,500 MPa along the machining axis 24 by the tool 10 produced in this way, which is shown in the central illustration in FIG. 15. As a result, the tool profile 20 is not completely molded onto the workpiece profile 25, with only half of the structural depth of the tool profile 20, which is referred to as the machining depth within the sense of the invention, being molded. The machining depth therefore does not correspond to the complete depth of the indentations 22 of the tool profile 20. As a result, the workpiece profile 25 has comparatively sharp-edged plateaus with a width of 5 m each, which are separated from one another by grooves in the form of indentations having a width of 5 m and a depth of 5 m. To the applicant's knowledge, such a workpiece profile 25 cannot be produced by direct structuring using laser radiation, since the melting dynamics that occur in this case lead to rounding of the workpiece profile and impair it. The full-surface structuring of the workpiece 12 is carried out by stitching; the workpiece 12 is shown on the right in FIG. 15 with structuring over the entire surface thereof.
[0077] FIG. 16 illustrates a further example of the process of machining a sheet of brass (CuZn30) as the workpiece 12 using the workpiece 12 shown on the left in FIG. 15, wherein the workpiece 12 is structured at a contact pressure of 3,500 MPa along the machining axis 24, which contact pressure is greater than in the method in FIG. 15, and with simultaneous vibration of the tool 10 as a die with frequencies in the ultrasonic range along the machining axis 24. This results in the tool profile 20 being completely molded onto the workpiece profile 25 so that the complete structural depth of 10 m of the tool profile 20 is molded. The machining depth in the method according to FIG. 16 is therefore greater than the machining depth in the method according to FIG. 15 due to the greater contact pressure. As a result, the workpiece profile 25 has a structure having sinusoidal, linear structural elements 21 which have a depth of 10 m and a lateral period d of 10 m. In this respect, the workpiece profile 25 corresponds to, in particular complements, the tool profile 20. The full-surface structuring of the workpiece 12 is carried out by stitching and is ultimately shown on the right in FIG. 16.
[0078] FIGS. 17 and 18 illustrate a further example of the method according to the invention for machining a workpiece 12, which is, for example, a sheet of brass (CuZn30). The tool 10 used for this purpose is arranged on the left in FIG. 17 and has a tool profile 20 having full-surface structuring with columnar elevations 23, wherein an indentation 22 is formed as a structural element 21 between two adjacent elevations 23. The indentations 22 themselves are arranged periodically one behind the other in two directions perpendicular to one another. In this respect, the tool profile corresponds to that in the example according to FIG. 3. Quantitatively and in contrast to the example in FIG. 3, the indentations 23 each have a depth of 10 m with respect to the unstructured region of the workpiece 10 and are arranged one behind the other in lateral periods d of 10 m each.
[0079] According to the central illustration in FIG. 17, the tool 10 is pressed onto the workpiece 12 as a die with acomparatively lowcontact pressure of 1,200 MPa along the machining axis 24 so that, as already described, the tool profile 20 is only partially molded onto the workpiece profile 25. In the present example, the tool profile 20 is only molded as far as half of the structural geometry of 10 m, which corresponds to the machining depth. This results in the workpiece profile 25 having sharp-edged indentations 22 with a diameter of 5 m, wherein the indentations 22 are arranged in a cubic periodic pattern. To the applicant's knowledge, such workpiece profiles 22, in particular their sharp-edged indentations 22, cannot be produced by direct laser structuring. The full-surface machining of the workpiece 12 is carried out by stitching, as already described. The workpiece 12 is shown on the right in FIG. 17 with structuring over the entire surface thereof.
[0080] In FIG. 18, another sheet of brass (CuZn30) is machined and structured as the workpiece 12 using the die as the tool 10 according to FIG. 17, wherein, in contrast to FIG. 17, a comparatively high contact pressure of 3,500 MPa along the machining axis 24 is used with an additional vibration of the tool 10 during the stamping process with frequencies in the ultrasonic range in order to mold the tool profile 20 onto the workpiece profile 25 as completely as possible. In the present example, the tool profile 20 is molded to the complete structural depth of 10 m so that the tool profile 25 ultimately has a columnar topography whose indentations 22 have a depth of 10 m and are arranged one behind the other in two lateral periods d of 10 m each, which are arranged perpendicularly to one another. The workpiece profile 25 is thus designed to complement the tool profile 20. The workpiece 12 is machined over its entire surface via stitching, as already described and indicated in the left-hand illustration in FIG. 18 by the gray arrows. The workpiece 12 that has been machined over the entire surface thereof is shown on the right in FIG. 18.
[0081] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.
