Laser ablation method for engraving a workpiece having a texture

Abstract

A laser ablation method for engraving a workpiece having a texture by a laser beam emitted by a laser head integrated in a machine tool, comprising: a. generating a plurality of machining layers based on the workpiece geometry to be successively machined; b. generating a plurality of facets for each machining layer, wherein each defines an area to be machined from a single position of the laser head, wherein a first facet and a second facet are positioned adjacent with a common boundary defined as a facet junction, wherein at least one of the facets comprises a non-ablation area and an ablation area based on the texture to be engraved, and the ablation area comprises a plurality of laser vectors with two ends defining a path of the laser beam to remove material of the ablation area, wherein at least one laser vector of the first facet and at least one laser vector of the second facet having a common end at the facet junction are defined as intersecting laser vectors, and the common end position is defined as an intersection position; and c. reducing the number of intersecting laser vectors by eliminating at least one intersection position.

Description

TECHNICAL FIELD

[0001] The invention relates to a laser ablation method for engraving a workpiece having a texture by means of a laser beam emitted by a laser head integrated in a machine tool. Furthermore, the invention relates to a machine tool for engraving a workpiece having a texture. BACKGROUND

[0002] Laser ablation methods and machine tools for laser texturing machined parts are generally known. The patent application EP 2301706 describes an example of a laser texturing machine. However, conventional ablation methods generally generate defects such as visible traces on the machined parts, which have a negative impact on the quality of the produced parts.

[0003] Various methods have been proposed for reducing such defects. The document EP 3047932 discloses a method which makes it possible to reduce visible traces while reducing machine time. The method describes defining the laser path in a special way to avoid such visible traces. But it is not always possible to define the laser path in this way. It depends on the texture and shape of the workpiece. For example, the proposed method is not suitable for ablating large continuous areas.

[0004] US 6518544 discloses a laser ablation method to improve the quality of engraved parts. In this method, the laser beam is guided in a trajectory on a section of the surface to be machined, then the surface is moved so as to bring an adjacent section into the machining area of the laser, then the laser beam is guided again in a trajectory on this machining area. An overlap area is formed at the border of the adjacent sections, the machining of which is allocated to one or the other section, so that the trajectories in which the laser beam is guided on the respective sections are interlaced with each other in the overlap area. This method can improve the engraving quality, but still generates visible traces at the border of adjacent sections. SUMMARY

[0005] The object of the invention is to provide a laser ablation method to overcome the drawbacks of known methods. The object of the invention is to further improve the quality of engraved parts. In particular, the object of the invention is to provide a laser ablation method to minimize visible traces on the produced parts.

[0006] According to the invention, these objects are achieved by the features of the independent claims. Further advantageous embodiments result from the dependent claims and the description.

[0007] In the present invention, a laser ablation method for engraving a workpiece having a texture by a laser beam emitted by a laser head integrated in a machine tool comprises: generating a plurality of machining layers based on the geometry of the workpiece to be machined continuously; generating for each machining layer a plurality of patches, each of the plurality of patches defining an area machined from a single position of the laser head, wherein a first patch and an adjacent patch are positioned adjacently with a common boundary defining a patch interface, wherein at least one of the patches comprises a non-ablation area and an ablation area based on the texture to be engraved, and the ablation area comprises a plurality of laser vectors having two ends defining a path of the laser beam removing material of the ablation area, wherein at least one laser vector in the first patch and at least one laser vector in the adjacent patch having a common end at the patch interface define an intersecting laser vector, and the position of the common end defines an intersection position; and reducing the number of intersecting laser vectors by eliminating at least one intersection position.

[0008] The machining layers are generated based on the geometry of the workpiece and the texture to be machined continuously. For each machining layer, a plurality of patches is generated, in particular taking into account the texture to be ablated. Each of the patches is machined from a single position of the laser head. Furthermore, a first patch and an adjacent patch having a common boundary portion define a patch interface. At least one of the patches comprises a non-ablation area and an ablation area comprising a plurality of laser vectors defining a path of the laser beam removing material. Each laser vector has two ends. At least one laser vector in the first patch and another laser vector in the adjacent patch have a common end at the patch interface, and these two laser vectors define an intersecting laser vector, and the position of the common end at the patch interface defines an intersection position.

[0009] The machining layers prescribe a defined thickness of material, and the patches prescribe an area of one layer to be ablated by one laser head position.

[0010] The laser ablation technique performs a texturing machining by sublimation of the material, generally a metal, on the surface of the workpiece. The machining is performed in several steps, each step corresponding to the machining of a layer of the part. Indeed, at each passage of the laser beam, the material can only sublimate to a depth of about 1 to 5 microns. Thus, the number of machining layers of the surface to be textured is generally between 20 and 100.

[0011] The part can be numerically modeled by a mesh, generally triangular, to generate a 3-D modeling file, for example a mesh file. The principle implemented to apply a texture to a three-dimensional surface is well known. The texture pattern that must be applied by laser ablation to the surface of the workpiece is typically defined by a gray-scale image called a texture file. The image displays a set of sublimation points, where the gray level of each point defines the ablation depth that must be obtained at that particular point: the lighter the point, the less ablation there will be, and the darker the ablation will be. The number of different gray levels can possibly equal the number of machining layers, but not necessarily. In fact, the texture image is defined by gray levels coded on 8 bits or even 16 bits, whereas the number of machining layers, as already indicated, most often lies between 20 and 100. A set of machining layers is thus generally calculated from the 3D modeling file and the gray-level texture file. Each machining layer has a corresponding black-and-white image: if the point is white, there is no ablation, and if the point is black, there will be ablation by sublimation.

[0012] For each machining layer, it is necessary to calculate a set of positions of the laser head, making it possible to machine the area of that layer. Generally, the optical system for laser ablation, with a focal length of, for example, 430 mm, makes it possible to machine a flat surface measuring, for example, 300 x 300 mm (called a trace domain) from a given position of the laser head. The size of the trace domain is limited due to the optical system of the machine tool. It means that the area being machined at a given position of the laser head is limited, so each machining layer must be divided into a plurality of facets, and each of the facets can be machined from a given position of the laser head. In order to machine another facet, the machine head must be repositioned. Each facet can comprise a large number of 3D modeling mesh triangles. A set of 3D modeling mesh triangles that can be machined from a given position of the laser head, in particular from one single position, is called a facet. Generally, each facet has a boundary line for defining the area of that facet. Since each facet comprises a set of mesh triangles, the boundary line of the facet extends along the edges of the triangles.

[0013] The complete texture machining of the surface of the workpiece thus consists in ablating a plurality of machining layers, for each of which the machining head must reach a set of positions in order to machine a facet for each position of the layer in question. Naturally, the calculation of the laser head positions and the machined facets requires a large number of computer resources: several hours or even several days, depending on the complexity and the size of the part, the type of algorithm used, the number of machining layers, etc. This calculation is thus generally performed on a specific workstation or computer, only the result of the calculation then being transmitted to the machine tool for laser ablation. The result of the calculation essentially comprises: a machining tool path, comprising a series of positions that the laser machining head must occupy relative to the part; and, for each position, a series of ablation operations corresponding to the scans that the laser beam must perform from that position. This result directly influences the machining time and the quality of the finish of the texturing.

[0014] However, the conventional ablation method generally generates defects in the form of visible border lines at the border of adjacent facets.

[0015] To process the surface of the workpiece, the laser beam is always moved along predefined parallel laser vectors. To generate respectively a texture and a relief on the surface, the laser pulses are switched off whenever no sublimation of the material is required. This is a known and commonly used method for laser texturing predefined facets on a workpiece, the so-called vector-like working process. Thus, the area to be ablated within a facet is defined by a plurality of laser vectors, and each laser vector has two ends to define a start position of the laser vector and an end position of the laser vector.

[0016] If possible, the facets are defined such that the border lines of the facets pass through areas which must not be ablated. However, it is not always possible to define the facets in this way. Thus, in most facets at least a part of the border line passes through an area of the facet which must be ablated, which means that one or more laser vectors start or end at the border line of the facet. Two adjacent facets have a facet junction which is the common part of the border lines of these two facets. If two laser vectors in these two adjacent facets have a common end at the facet junction which is defined as an intersection position, a visible trace can be seen at the intersection position. Thus, to reduce the visible trace to improve the quality of the machined part, the number of intersecting laser vectors is reduced by eliminating at least one intersection position. In particular, if most of the intersection positions can be removed, a significant improvement of the surface quality can be achieved. The intersection positions can be eliminated by redefining the position of the ends of the intersecting laser vectors.

[0017] In a preferred variant, the common end of the intersecting laser vectors at the intersection position is extended along one of the intersecting laser vectors to reach an adjusted end position in a non-ablated area of the facet. Since the adjusted end position is in a non-ablated area, the visible trace can be significantly reduced.

[0018] In a variant, a first laser vector in a first facet and another laser vector in an adjacent facet are intersecting laser vectors which have a common end at an intersection position. To eliminate the intersection position, the end of the first laser vector at the intersection position is extended along the other laser vector to reach a first adjusted end position which is in a non-ablated area of the second facet. When the first adjusted end position is chosen, the other laser vector disappears because the first laser vector with the first adjusted end position covers the length of the other laser vector. Even if one end of the first laser vector, i.e. the first adjusted end position, is arranged in the adjacent facet, the first laser vector belongs to the first facet. This means that the entire first laser vector including the part in the adjacent facet is machined by the same laser head position which is used for all laser vectors of the first facet.

[0019] In another variant, the end of the other laser vector at the intersection position is extended along the first laser vector to reach a second adjusted end position, which is in the non-ablation area of the first patch. In this case, the first laser vector disappears because its length is replaced by the other laser vector. Even if one end of the other laser vector, i.e. the second adjusted end position, is arranged in the first patch, the other laser vector belongs to the adjacent patch. This means that the whole other laser vector, including the part in the first patch, is machined by the same laser head position, which is valid for all laser vectors of the second patch.

[0020] After adjusting the end position of a laser vector from the intersection position to the first adjusted end position or the second adjusted end position, ablation at the intersection position occurs only once instead of twice, thus reducing the visible trace at this position. Moreover, since the first adjusted end position or the second adjusted end position is in the non-ablation area, the surface quality can also be improved.

[0021] Depending on the texture, both mentioned variants are possible. In order to improve the machinability, the distance from the intersection position to the first adjusted end position and the distance from the intersection position to the second adjusted end position are compared and the adjusted end position with the smaller distance is chosen. If the distance from the intersection position to the first adjusted end position is smaller than the distance from the intersection position to the second adjusted end position, then the intersection position is moved to the first adjusted position by extending the other laser vector into the first patch. If the distance from the intersection position to the second adjusted end position is smaller than the distance from the intersection position to the first adjusted end position, then the intersection position is moved to the second adjusted position by extending the first laser vector into the adjacent patch.

[0022] In a preferred variant, to ensure that the ablation area in each patch can be machined from one single position of the laser head without reducing the ablation quality, at least one limit on each side of the patch interface is predetermined to define a patch interface area in which the adjusted end position can be positioned. As outlined above, the trace field is limited, and therefore, the maximum area that can be machined by the laser head at one single position is limited. Therefore, the extension of the intersecting laser vectors into the adjacent patch must be limited in a defined range to ensure that it can still be machined by the laser head without changing its position. For example, if a first laser vector extends to a second adjusted end position in an adjacent patch, the second adjusted end position must be within the defined patch interface area. If the second adjusted end position is outside this area, a part of the first laser vector extending in the adjacent patch cannot be ablated by the machine head staying at the position where the first patch is ablated. Therefore, the first adjusted position and the second adjusted end position are positioned in the patch interface area. In one variant, a first limit is provided for the first patch and a second limit is provided for the adjacent patch. It is also possible to provide multiple limits in each patch.

[0023] As disclosed in EP 3421168, a verification can be applied to further improve the quality of the machined part.

[0024] In a preferred variant, the first limit and the second limit are equal.

[0025] If two adjacent laser vectors in one patch intersect with two adjacent laser vectors in an adjacent patch, there are two adjacent intersection positions, it is preferred to extend the laser vectors in the same direction so that the two adjusted end positions are located in the same patch. Therefore, in one variant, the two adjacent intersection positions are moved to two adjusted end positions positioned in the same patch. For example, a third laser vector and a fourth laser vector belong to a first patch and an adjacent patch, respectively. The third laser vector is adjacent to a first laser vector in the first patch, and the fourth laser vector is adjacent to another laser vector in the adjacent patch. The first laser vector and the another laser vector intersect at a first intersection position at a patch interface of the first patch and the adjacent patch, while the third laser vector and the fourth laser vector intersect at a second intersection position at the same patch interface. Obviously, the first intersection position and the second intersection position are adjacent. If the first intersection position and the second intersection position are moved to different patches, a visible trace caused by the overlapping of the heat effect and the focus of the laser beam can be seen. To avoid this trace, the first intersection position and the second intersection position are preferably moved to the same patch, or to the first patch, or to the adjacent patch.

[0026] It is also possible to change a laser vector adjacent to one intersecting laser vector in the first patch to the adjacent patch.

[0027] In the present invention, the control unit for controlling the laser beam emitted by the laser head integrated in the machine tool for engraving a workpiece with a texture is configured to receive control data generated based on an ablation method, in particular the control data is generated in an external device.

[0028] In the present invention, the machine tool for engraving a workpiece with a texture by means of a laser beam emitted by a laser head integrated in the machine tool comprises a control unit. BRIEF DESCRIPTION OF DRAWINGS

[0029] In the following a more particular description of the principles briefly described above will be presented by referring to specific embodiments thereof illustrated in the drawings. These drawings show exemplary embodiments of the present disclosure and therefore should not be considered limiting its scope. The principles of the present disclosure are described and explained in detail by using the drawings in which:

[0030] Figure 1 , Figure 2 : shows a machine tool for laser ablation;

[0031] Figure 3 : shows one example of a 3-D modeling file;

[0032] Figure 4 : shows a texture image file;

[0033] Figure 5 , Figure 7 : shows a facet;

[0034] Figure 6 : shows laser vectors within one facet;

[0035] Figure 8 : shows one example of the prior art; and

[0036] Figure 9-1 4: shows an embodiment of the present invention. DETAILED DESCRIPTION

[0037] Figure 1An example of the configuration of a machine for laser texturing is schematically shown. The laser head 1 of the machine and the piece are positioned relative to each other according to 5 mechanical axes, which make it possible to orient the direction of the emitted laser beam and to position the focal point of the laser on the surface of the machined piece, not shown, placed in the machine. The laser head 1 is displaceable in three dimensions X, Y and Z of a Cartesian reference frame. Advantageously, the laser head is also movable in rotation around non- shown axes of rotation, to obtain greater precision and greater flexibility. In the remainder of the disclosure, it will be considered that, for all the examples given, the laser head is moved according to five axes, i.e. three translation axes and two rotation axes. The laser head comprises a laser source for emitting a laser beam, optical means and a galvanometer.

[0038] Figure 2 The operation of the galvanometer is schematically shown. The laser head 1 emits a laser beam 2, or more particularly, a pulsed laser beam. The laser beam 2 is reflected by mirrors 4 and 5, which respectively make it possible to define the position of the point of projection of the laser beam on the surface of the piece 7 according to the axes X and Y of a Cartesian reference frame. Actuators 8 make it possible to control the angular position of the mirrors 4 and 5. The laser beam also passes through a lens 6 with dynamic focusing correction, commonly called F-theta lens. This device thus makes it possible to define the point of impact of the laser beam with the surface of the piece 7 in a plane located in the range of focal points considered.

[0039] Generally, the system used, with a focal length of for example 430 mm, makes it possible to machine a flat surface of 300 x 300 mm (called a trace field) from a given position of the laser head 1 using the galvanometer. On the other hand, when the surface of the piece 7 to be machined is not flat, the focusing power of the lens limits the trace field in the X and Y directions. If the curvature of the piece is significant, it is then necessary to reduce the size in X and Y of the trace field for each variation in Z. Naturally, this thus increases the number of different positions occupied by the laser head to carry out a texturing job, i.e. the number of tiles generated must be increased. This is the reason for the development of optical means for zooming on the axis Z, which make it possible to vary the focusing along the axis Z and allow the machining of a trace field with a trace depth of + or - 80 mm. The use of a focal point variation device does not eliminate the relative repositioning of the laser head 1 and the piece, but it does considerably limit the number thereof.

[0040] Figure 3One example of numerical modeling of the three-dimensional shape of a part by a mesh of generally triangular form 11.1, 11.2 and patches 10, 10a, 10b is shown. The thick black lines represent the boundary lines of the different patches. Each patch comprises a plurality of mesh triangles, represented by the thinner black lines. The boundary lines of the patches extend along the edges of the mesh triangles. Some mesh triangles are positioned at the patch junctions, such as the mesh triangle labeled 11.2, some mesh triangles are not at the patch junctions, such as the mesh triangle labeled 11.1. It is also possible that a patch comprises only mesh triangles positioned at the patch junctions, such as the patch labeled 10b.

[0041] Figure 4 One example of the textures that must be applied by laser ablation to the surface of a part is shown, these textures being typically defined by a gray scale image. The image shows a set of sublimation points, where the gray level of each point defines the ablation depth that must be obtained at that particular point: the lighter the point, the less ablation will be, and the darker the point, the deeper the ablation will be.

[0042] As Figure 5 It is common, as shown schematically in Fig. 1, to define patches 10 that do not overlap for two successive layers 9.1 and 9.2.

[0043] In order to treat the surface of a workpiece, the laser beam is always moved along Figure 6 The pre-defined parallel laser vectors on the patches 10 shown are moved, jumping to the next position at the boundary of the patch 10. Figure 6 An example of the entire area of a patch that must be ablated is shown.

[0044] The patches shown in the figures, having a rectangular shape, are simplified illustrations. The patches can have different shapes. The shape of the patches and the number of patches are not limited to the particular shapes and numbers shown in the figures. Figure 7 Four patches, a first patch 20, a second patch 30, a third patch 40 and a fourth patch 50 are shown. The boundary between the first patch and the third patch forms a first patch junction 21, the boundary between the first patch and the second patch forms a second patch junction 31, the boundary between the third patch and the fourth patch forms a third patch junction 41, and the boundary between the second patch and the fourth patch forms a fourth patch junction 51. The vertical lines with different thicknesses represent the laser vectors of the first patch 22, the laser vectors of the second patch 32, the laser vectors of the third patch 42 and the laser vectors of the fourth patch 52. All the areas covered by the laser vectors are ablation areas, i.e. the material of these areas must be ablated. The white areas are non-ablation areas 23, 33, 43 and 53 in the different patches, i.e. no material must be ablated in these areas. In the example shown, the laser vectors of the first patch 22 and the laser vectors of the second patch 32 are parallel to each other, the laser vectors of the second patch 32 and the laser vectors of the third patch 42 are parallel to each other, and the laser vectors of the third patch 42 and the laser vectors of the fourth patch 52 are parallel to each other. Figures 7 to 12In the figures, the laser vectors are shown in vertical direction and the facet junctions are shown as straight line boundaries, either vertical or parallel to the laser vectors. These illustrations are only simplified representations. In the present invention, the facet junctions are not limited to the representations in the figures.

[0045] Visible traces can be generated at the facet junctions. When the facet junctions are parallel to the laser vectors, the traces are weak. However, when two laser vectors in two adjacent facets have the same start or end position at the facet junction of these two facets, for example, the laser vector 22 of the first facet 20 intersects the laser vector 42 of the third facet 40 at a point A on the first facet junction 21. Such laser vectors are defined as intersecting laser vectors and the common position at the facet junction is defined as an intersection position, for example, point A.

[0046] To reduce the visible traces at the junctions, a so-called random facet method is applied, as shown in Figure 8 The intersection position of the intersecting laser vectors is moved randomly to a new position not at the facet junction. For example, the intersection position at point A is moved to point Al, which is not on the first facet junction 21 but in the first facet 20. However, the laser vector 42 still belongs to the third facet, which means that the laser vector 42, represented by the thick line, is machined to have the laser head position for the third facet, even the part arranged in the first facet. To guarantee ablation after moving the intersection position, at least one limit is defined to limit the range of the repositioning. In this example, two limits are shown as two straight lines 15 and 16 parallel to the facet junction to define a facet junction area 14. However, this illustration is simplified and the limits are not limited to straight lines and parallel to the facet junction.

[0047] One embodiment of the present invention is shown in Figure 9 The intersection position of the intersecting laser vectors is moved away from the facet junction and a non-ablation area, represented by the white area, is searched in order to move the intersection position from the facet junction to the boundary of the non-ablation area, if possible. For example, the laser vectors 24 and 44 are intersecting laser vectors. In the standard random method shown in Figure 8 In the standard random method shown in Figure 8 In the standard random method shown in

[0048] Figures 10 and Figures 11A further embodiment of the application is shown. The first, second and third laser vectors 26, 27 and 28 of the first patch are adjacent laser vectors and end at the first patch junction 21 and the fourth, fifth and sixth laser vectors 46, 47 and 48 in the third patch 40 are also adjacent laser vectors and end at the same first patch junction 21 at the intersection points C, D and E because the first and third patch are adjacent patches. In the case shown in Fig. 10 several options are available to change the position of the intersection position. One variant is based on the minimum distance, i.e. moving the laser vectors to the minimum distance. For example, the fourth laser vector 46 of the third patch is extended into the first patch to point C1 instead of extending the first laser vector 26 into the third patch to point C1a. The second laser vector 27 is extended into the third patch to point D1 instead of extending the fifth laser vector 47 into the first patch to point D1a. The sixth laser vector 48 of the third patch is extended into the first patch to point E1 instead of extending the third laser vector 28 into the third patch to point E1a. However, this causes a so-called cross-over effect which means that the trace is caused by the overlap of the thermal effect and the laser beam focus. Since the fourth and fifth laser vectors 46 and 47 still belong to the third patch and the second laser vector 27 belongs to the first patch, the ablation of the first patch is performed before the ablation of the third patch, so the order of the three adjacent laser vectors 46, 47 and 48 is not ablated in this order. This causes additional traces on the produced part.

[0049] To further improve the quality of the produced part, so-called priority directions are determined and applied. As Figure 12 shown in Fig. 10, the fourth, fifth and sixth laser vectors in the third patch are extended into the first patch. This means that the direction of the extended laser vectors is the same. The new intersection positions are at the C2, D2 and E2 points of the three laser vectors and in the first patch. By this way, the cross-over between the laser vectors of different patches can be avoided.

[0050] Figure 13 An example is shown where the laser vectors are not perpendicular to the laser vectors.

[0051] Fig. 14a shows a further optimization to reduce the cross-over effect. The laser vector 116 is not an intersection laser vector and belongs to the first patch, but this laser vector will be changed to the third patch as Figure 14b shown in Fig. 14b. The laser vector 117 is an intersection laser vector and will be optimized by changing it to the third patch as well to reduce the cross-over effect.

[0052] List of signs

[0053] 1 laser head

[0054] 2 laser beam

[0055] 4, 5 mirror

[0056] 6 lens

[0057] 7 part

[0058] 8 actuator

[0059] 9.1, 9.2 machined layer

[0060] 10, 10a, 10b panel

[0061] 11.1, 11.2 mesh triangle

[0062] 20 first panel

[0063] 21 first panel interface

[0064] 22 laser vector of first panel

[0065] 30 second panel

[0066] 31 second panel interface

[0067] 32 laser vector of second panel

[0068] 40 third panel

[0069] 41 third panel interface

[0070] 42 laser vector of third panel

[0071] 50 fourth panel

[0072] 51 fourth panel interface

[0073] 52 laser vector of fourth panel

Claims

1. A laser ablation method for engraving a workpiece having a texture by a laser beam emitted from a laser head integrated in a machine tool, the laser ablation method comprising: generating, using the machine tool, a plurality of machining layers based on a geometry of the workpiece to be continuously machined; generating, using the machine tool, for each machining layer a plurality of patches, each of the plurality of patches defining an area to be machined from a single position of the laser head, wherein a first patch and its adjacent patch are adjacently positioned with a common boundary defining a patch interface, wherein at least one of the patches comprises a non-ablation area and an ablation area based on the texture to be engraved, and the ablation area comprises a plurality of laser vectors having two ends defining a path of the laser beam removing material of the ablation area, wherein at least one laser vector in the first patch and at least one laser vector in the adjacent patch having a common end at the patch interface define an intersecting laser vector, and the position of the common end defines an intersection position, wherein the common end of the intersecting laser vectors at the intersection position extends along one of the intersecting laser vectors to reach an adjusted end position in the non-ablation area of the patch; and reducing, using the machine tool, the number of intersecting laser vectors by eliminating at least one intersection position.

2. The laser ablation method according to claim 1, wherein, a first laser vector in the first patch and another laser vector in the adjacent patch are intersecting laser vectors, and an end of the first laser vector at the intersection position can extend along the other laser vector to reach a first adjusted end position in the non-ablation area of the adjacent patch, or an end of the other laser vector at the intersection position can extend along the first laser vector to reach a second adjusted end position in the non-ablation area of the first patch.

3. The laser ablation method of claim 2, wherein, comparing a distance between the first adjusted end position to the intersection position with a distance to the second adjusted end position, and selecting the adjusted end position with the smaller distance.

4. The laser ablation method according to claim 2 or 3, wherein, when the first adjusted end position is selected, the other laser vector is eliminated, and when the second adjusted end position is selected, the first laser vector is eliminated.

5. The laser ablation method according to claim 2 or 3, wherein, the first laser vector with the first adjusted end position belongs to the first patch, and the other laser vector with the second adjusted end position belongs to the adjacent patch.

6. The laser ablation method according to any one of claims 1 to 3, wherein, predetermining at least one limit for each side of the patch interface to set a patch interface area in which the adjusted end position can be positioned, setting a first limit for the first patch and a second limit for the adjacent patch.

7. The laser ablation method according to any one of claims 1 to 3, wherein, two adjacent intersection positions move to two adjusted end positions positioned in the same patch.

8. The laser ablation method according to any one of claims 1 to 3, wherein, a laser vector in the first patch adjacent to one intersecting laser vector changes to the adjacent patch.

9. A control unit for controlling a laser beam emitted by a laser head integrated in a machine tool for engraving a workpiece having a texture, wherein the control unit is configured to receive control data generated by the laser ablation method according to any one of claims 1 to 8.

10. A machine tool for engraving a workpiece having a texture by means of a laser beam emitted by a laser head integrated in the machine tool, the machine tool comprising a control unit according to claim 9.

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