Method for generating a weakening line

Abstract

Method for producing a weakening line in a workpiece by material removal with a laser beam, comprising Providing the workpiece with a viewable side and a reverse side facing away from the viewable side, Applying the laser beam to the reverse side, Controlling the energy input of the laser beam into the workpiece in a pulsed operating mode using a control unit, Performing a relative movement between the workpiece and the laser beam along the attenuation line, Crossing the weakening line in a cycle of relative motion, at least a simple repetition of the cycle of relative motion, Control of the energy input depending on the respective point of impact of the laser beam along the attenuation line by means of the control unit.

Description

[0001] The invention relates to a method for generating a weakening line in the surface of a workpiece. State of the art

[0002] The use of airbag systems is standard in vehicles and vehicles in general today. The airbags are positioned as inconspicuously as possible behind parts of the vehicle's interior trim. This trim typically consists of robust, flat molded panels made of plastic or composite materials. Since the airbags are ejected through the interior trim when deployed, airbag flaps must be incorporated. These flaps are often formed by specially designed sections of the interior trim, featuring predetermined breaking points along the edges of the flaps to ensure a safe and controlled opening of the trim.

[0003] The rigid parts of the interior trim are often covered with additional, decorative materials, which enhance the appearance and feel of the surfaces. These covering materials are typically flexible and thin, such as plastic films, synthetic leather, knitted textiles, microfiber fleeces, or natural leather. For the airbag to deploy safely, the covering materials in the area of ​​the airbag flaps must also be designed with predetermined breaking points. Just as with the interior trim components, weakening lines are incorporated for this purpose. For aesthetic reasons, these lines are usually applied from the non-visible reverse side of the covering material. In addition to precisely adjustable remaining tear resistance of the weakening line, the highest quality standards for the surfaces are only met if the weakening line is neither visually nor tactilely perceptible on the passenger-facing side of the covering material.

[0004] Creating the weakening line by ablation with a laser beam is preferable to mechanical creation, for example with a blade, because the weakening line can be created more cleanly and with greater definition.

[0005] The material is to be removed along the weakening line down to a desired residual wall thickness. Maintaining this desired residual wall thickness is important because the weakening line should not be visible to the naked eye from the side of the component facing away from the laser beam. The weakening line can, for example, be designed as a perforated line with a series of slots, each with the desired residual wall thickness and separated from each other by ribs.

[0006] Patent DE102013104138 B3 discloses a method for generating a weakening line in the surface of a component, in which the weakening line is created with a scanned laser beam that is guided along the weakening line. The material is removed along the weakening line by the energy input of the laser beam into the material. The aim is to remove the material down to the desired residual wall thickness. On the side of the component facing away from the incident laser beam, there is at least one sensor that detects the laser light penetrating the component. When the laser light penetrating the component reaches a certain value at a specific position, the laser beam is no longer activated at that position during the subsequent scanning process, and therefore no further material is removed.

[0007] Patent DE102020131069 B4 discloses another method for generating a weakening line using a scanned laser beam. The weakening line to be generated is divided into segments. The desired residual wall thickness can vary in the individual segments. On the side of the component facing away from the incident laser beam, there is at least one sensor that detects the laser light penetrating the component. The laser beam is repeatedly passed over the weakening line to be generated in several cycles. If the sensor detects that the desired residual wall thickness has been reached in a segment, this segment is skipped in subsequent cycles and not weakened further. The remaining segments are weakened until their respective residual wall thicknesses are also reached.

[0008] When creating the weakening line, it is important to ensure that the energy input does not exceed the workpiece's damage threshold. If the energy input exceeds this threshold, damage will be visible, particularly on the visible side of the workpiece. This would render the workpiece unusable. Disadvantages of the state of the art

[0009] The material to be weakened can be inhomogeneous. This applies, for example, to leather, which has a natural variation in thickness and / or strength. This also applies to textiles that contain alternating stitches and holes.

[0010] Experience in material weakening shows that there is a threshold energy input for the laser beam. Only energy input above this threshold leads to material weakening. This threshold can be inhomogeneous across the material. In an inhomogeneous material, there can be at least one location along the weakening line with a higher threshold. If energy below this higher threshold is applied in a cycle, no material weakening occurs at this at least one location. Therefore, the material cannot be weakened further at this location in subsequent cycles, and the desired residual wall thickness is not achieved.

[0011] In the methods known from the prior art, the energy input of the laser beam remains the same as the processing of the workpiece progresses or is even reduced in order to approximate the desired residual wall thickness.

[0012] Therefore, when weakening a component made of inhomogeneous material using a prior art process, it is possible that segments along the weakening line will not achieve the desired residual wall thickness. Such a component would not meet the specification and would be unsuitable for use. Object of the invention

[0013] The object of the invention is therefore to provide a method that reliably creates a weakening line in the surface of a component. Inhomogeneities in the component's material are to be taken into account and compensated for, thus achieving the desired residual wall thickness at every position on the component. Damage to the workpiece visible on the viewing side is to be avoided. Inventive solution

[0014] The problem is solved by a method according to claim 1.

[0015] The invention may be particularly suitable if the workpiece in which the weakening line is to be created is inhomogeneous. This applies, for example, to leather, which has a natural variation in thickness and / or strength. This also applies to textiles that contain both fibrous mesh and holes. The material to be weakened can also be a fiber-reinforced plastic material. The fibers used to reinforce the plastic matrix, for example, glass fibers, carbon fibers, metal fibers, aramid fibers, in particular poly(azanediyl-1,4-phenyleneazanediyl terephthaloyl) fibers, or asbestos fibers, may exhibit a different ablation rate and / or ablation threshold with respect to the laser radiation than the plastic matrix. Description

[0016] The inventive method for producing a weakening line in a workpiece by material removal with a laser beam comprises: • Provide the workpiece with a viewing side and a reverse side facing away from the viewing side. • Applying the laser beam to the back side • Controlling the energy input of the laser beam into the workpiece in a pulsed operating mode using a control unit • Performing a relative movement between the workpiece and the laser beam along the attenuation line • Crossing the weakening line in one cycle of relative motion • at least one repetition of the cycle of relative motion • Controlling the energy input depending on the respective point of impact of the laser beam along the attenuation line by means of the control unit • Increasing the energy input at at least one of the respective points of impact of the laser beam along the attenuation line in one of the cycles following the respective cycle of relative motion by the control unit.

[0017] The energy input of the laser beam at the respective point of impact of the laser beam along the attenuation line can be increased several times in further repetitions of the cycle of relative motion up to an upper limit of the energy input.

[0018] The upper limit of the energy input can be higher than an ablation threshold, whereby material ablation occurs when the energy input is higher than the ablation threshold, and in particular the ablation threshold depends on the respective point of impact of the laser beam along the attenuation line.

[0019] The upper limit of the energy input is preferably not higher than a damage threshold of the workpiece, whereby if the energy input is higher than the damage threshold of the workpiece, damage to the workpiece that is visible on the viewing side will occur in particular.

[0020] Material removal is preferably achieved by ablation with ultrashort laser pulses with a pulse duration of less than 1000 fs or by vaporization with short laser pulses with a pulse duration of 1 µs to 1000 µs. The pulse duration can also be in the ps or ns range.

[0021] The weakening line preferably comprises an alternating series of slots and ribs, wherein the slots typically have a length of 0.5 mm to 5 mm and a width of 0.05 mm to 1 mm, and the ribs have a length of up to half the slot length. In the slots, the workpiece material is removed down to a residual wall thickness. This residual wall thickness is typically 0.1 mm to 0.2 mm. In the ribs, no or less material is removed than in the slots.

[0022] The material in the slots can also be completely removed all the way to the visible side of the workpiece, meaning the remaining wall thickness can be zero. In this case, it is advantageous if the slots have such a small cross-section that they are not visible from the visible side.

[0023] The method preferably comprises detecting the portion of the laser beam penetrating the workpiece in a sensor unit and calculating a residual wall thickness of the workpiece at the respective point of impact of the laser beam along the attenuation line from the detected portion of the laser beam penetrating the workpiece in the control unit.

[0024] The sensor unit can contain photoelectric and / or pyroelectric sensors, the preferred configuration depending on the wavelength of the laser beam. Examples include photodiodes, photoresistors, and sensors containing a pyroelectric material.

[0025] The energy input at the respective point of impact of the laser beam along the attenuation line is preferably reduced to essentially zero when a desired residual wall thickness is reached at the respective point of impact of the laser beam along the attenuation line.

[0026] Further repetitions of the relative motion cycle can be omitted and the creation of the weakening line can be stopped once the desired residual wall thickness has been achieved at all points of impact of the laser beam along the weakening line. This results in a reduction of the workpiece processing time.

[0027] In one variant of the method according to the invention, the energy input of the laser beam in one of the cycles following the respective cycle of relative motion can be increased depending on how many of the laser beam's point of impact along the attenuation line have already reached the desired residual wall thickness in that cycle. The energy input can be substantially increased if the residual wall thickness has not yet been reached at any point of impact or at only a few points of impact in that cycle. The energy input can be slightly increased if the residual wall thickness has already been reached at most points of impact in that cycle. A substantial increase could, for example, be an increase of 20%. A slight increase is smaller than a substantial increase and could, for example, be an increase of 10%.Increasing the energy input depending on how many impact points the desired residual wall thickness has already been achieved in the respective cycle leads to a reduction in the machining time of the workpiece.

[0028] The method according to the invention can be described in a flowchart, wherein the flowchart comprises a performance loop and a cycle loop nested in the performance loop: • Start of the schedule • Start of the power loop • Start of the cycle loop, wherein in one cycle of the cycle loop the weakening line is swept over once with the laser beam and wherein the energy input of the laser beam into the workpiece has a current upper limit. • The cycle loop can be repeated at least once. • The performance loop can be repeated at least once with a new upper limit, where the new upper limit is greater than the current upper limit, and where, in the cycle loop nested within the performance loop, the current upper limit is set to the new upper limit. • End of the schedule

[0029] The inventive method for producing the weakening line in the workpiece by material removal with the laser beam can preferably be used when the workpiece comprises leather or textile.

[0030] A device for producing the weakening line in the workpiece by material removal with the laser beam is preferably designed in such a way that the method according to the invention can be carried out. Drawings

[0031] The invention is explained in more detail below using exemplary embodiments. The drawings show: Fig. 1 a device in which the inventive method for producing the weakening line in the workpiece by material removal with the laser beam can be carried out; Fig. 2a - 2d Cross-sections through the workpiece with the weakening line in different states of the weakening line production; Fig. 3a - 3e the back of the workpiece with the attenuation line in different cycles of relative movement between the workpiece and the laser beam along the attenuation line; Fig. 4 a flow chart of the inventive method for producing the weakening line in the workpiece by material removal with the laser beam; and Fig. 5a - 5f the energy input of the laser as a function of time in different cycles of relative motion between the workpiece and the laser beam along the attenuation line. Examples of implementation

[0032] Fig. Figure 1 shows a device 10 on which the method according to the invention can be carried out. A laser unit 2 emits a laser beam 3. The laser unit 2 contains optical elements that shape the laser beam 3 into a desired form, for example, setting a desired diameter of the laser beam 3 or generating a focal point at a desired distance from the laser unit 2. These optical elements can be, for example, lenses, curved mirrors, or diffractive optical elements.

[0033] The laser beam 3 strikes a workpiece 1. The workpiece 1 has a visible side 7 and a reverse side 8 facing away from the visible side 7. There are several options for performing a relative movement between the workpiece 1 and the laser beam 3. In one of these options, Fig. In the embodiment shown in Figure 1, a scanner mirror 4 is located between the laser unit 2 and the workpiece 1. The scanner mirror 4 is controlled by a control unit 6 and deflects the laser beam 3 striking the scanner mirror 4. In this way, the laser beam 3 is guided over an attenuation line 9 on the back side 8 of the workpiece 1, and a relative movement is carried out between the workpiece 1 and the laser beam 3.

[0034] The weakening line 9 is crossed in one cycle of relative motion. In subsequent cycles, the weakening line is crossed repeatedly.

[0035] There are further embodiments for performing a relative movement between the workpiece 1 and the laser beam 3. In an alternative embodiment (not shown), the workpiece 1 is moved, for example, by a robot arm, while the laser beam 3 remains stationary, and the device does not need to include a scanner mirror 4. In another embodiment (not shown), the laser unit 2 is moved, for example, by a robot arm. In yet another embodiment (also not shown), the movements of the scanner mirror 4 and / or the workpiece 1 and / or the laser unit 2 can be combined to perform a relative movement between the workpiece 1 and the laser beam 3.

[0036] A sensor unit 5, positioned along the rear side 8 in the direction of the laser beam 3, detects the portion of the laser beam 3 penetrating the workpiece 1 and outputs a measurement signal. The control unit 6 evaluates the measurement signal and, depending on the signal, controls the laser unit 2 in a pulsed operating mode with a sequence of pulses. The energy input of the laser beam 3 into the material 1 is controlled by the respective duration and / or amplitude of the pulses.

[0037] Fig. Figure 2a shows a cross-section through workpiece 1 with an exemplary section of the weakening line 9. The exemplary section of the weakening line 9 contains three slots 22, 23, 24 in which the material of workpiece 1 has been removed by the laser beam down to a residual wall thickness 25. Between the slots 22, 23, 24 are webs 20, 21 in which no or less material has been removed than in the slots 22, 23, 24. A slot has a typical length of 0.5 mm to 5 mm and a typical width of 0.05 mm to 1 mm. A web has a typical length of ¼ to ½ the length of a slot.

[0038] The remaining wall thickness 25 is calculated from the portion of the laser beam 3 that penetrates the workpiece 1 and is detected in the sensor unit 5. When the remaining wall thickness 25 reaches a target value at a position of the laser beam 3, the laser beam 3 is switched off at that position and no further material is removed. The target value for the remaining wall thickness 25 is typically 0.1 mm to 0.2 mm. The in Fig. The exemplary section shown in 2a from the weakening line 9 fulfills a specification of workpiece 1 with which the workpiece 1 could be used.

[0039] Fig. Figure 2b shows a cross-section through workpiece 1 with another exemplary section. This section contains an inhomogeneity 26 as an inclusion. The inhomogeneity 26 is located in Fig. 2b is located approximately in the center of workpiece 1, but could also be, for example, on or near the visible side 7 or the reverse side 8. The inhomogeneity 26 can, for example, exhibit higher strength, such as in natural leather. As another example, the inhomogeneity 26 could also be a loop in a textile whose strength differs from that of the surrounding holes.

[0040] The laser beam 3 is guided along the weakening line and removes material at the points where the remaining wall thickness 25 has not yet reached the target value.

[0041] In Fig. Figure 2c shows workpiece 1 in a machining state where the remaining wall thickness 25 in slots 22 and 24 has already reached the target value. Inhomogeneity 26 is located in the area of ​​slot 23. In a prior art process where the energy input is not increased in cycle repetitions, the material in slot 23 cannot be removed further. Therefore, the target value of the remaining wall thickness 25 cannot be reached in slot 23. Workpiece 1 would thus be unusable or only usable to a limited extent.

[0042] Fig. Figure 2d shows the workpiece 1 after application of the inventive method explained below. The material in slot 23 was also removed at the inhomogeneity 26.

[0043] The target value of the remaining wall thickness 25 was also achieved in slot 23. Workpiece 1 is therefore usable.

[0044] In Fig. 3a - Fig. 3e describes the method according to the invention in an exemplary embodiment.

[0045] Fig. Figure 3a shows the back side 8 of workpiece 1 with a weakening line 9, which is not yet complete in this illustration. The weakening line 9 is swept over by the laser beam 3 (not shown), for example, in the direction indicated by arrow 31. In one cycle of relative movement between workpiece 1 and laser beam 3, the weakening line 9 is swept over once.

[0046] Fig. Figure 3b shows an initial processing state after a first number of repetitions of the relative motion cycle. For these cycle repetitions, the laser was operated with an initial upper limit on the energy input into the workpiece 1. The energy input is higher than an initial ablation threshold. Material removal begins at this initial ablation threshold. Therefore, material removal has already occurred along the weakening line 9 in segments 32, 33, 34, and 35. However, the target value of the remaining wall thickness 25 in segments 32, 33, 34, and 35 has not yet been reached, as indicated by the thin dotted lines.

[0047] Fig. Figure 3c shows a subsequent processing state after further repetitions of the relative movement. In segments 32 and 33, material removal has already reached the target value of the remaining wall thickness 25. This is indicated by the thick dotted lines. The achievement of the target value of the remaining wall thickness 25 is detected by the sensor unit 5 and the control unit 6. Therefore, in the following cycles of the relative movement, the laser energy input into the workpiece 1 in segments 32 and 33 is reduced to essentially zero by the control unit 6, and no further material removal occurs. In segments 34 and 35, there is at least one inhomogeneity 26, which has a second ablation threshold that is higher than the first ablation threshold. The laser energy input is below the second ablation threshold. Thus, no material removal occurs in segments 34 and 35.Even after further repetitions of the cycle, no material removal occurs in segments 34 and 35 with the same energy input.

[0048] Fig. Figure 3D shows a further processing state after the inventive method has been applied. The laser energy input was increased to a value above the second ablation threshold. After at least one further repetition of the cycle, the material in segment 35 has been ablated down to the target value of the remaining wall thickness 25.

[0049] This is illustrated by the thick dotted line. In segment 34, the target value of the remaining wall thickness 25 has not yet been reached. In segment 34, there is at least one inhomogeneity 26 that has a third wear threshold higher than the first and second wear thresholds.

[0050] Fig. Figure 3e shows a further processing state after the inventive method has been applied again. The laser energy input was increased to a value above the third ablation threshold. After at least one further repetition of the cycle, the material in segment 34 has been ablated down to the target value of the remaining wall thickness 25. This is illustrated by the thick dotted line.

[0051] By applying the method according to the invention in this embodiment, the target value of the residual wall thickness 25 was achieved in all segments 32, 33, 34, 35 along the weakening line 9.

[0052] Fig. Figure 4 shows a further embodiment of the method according to the invention in a flowchart. It comprises a performance loop 111 with steps 103-110 and a cycle loop 108 with steps 105-107, which is nested within the performance loop 111.

[0053] The method according to the invention comprises the following steps. • 101: Start of the schedule • 102: Initializing the power loop 111 with m := 1. • 103: Start of the power loop 111. The current upper limit E of the energy input is set to a value E m set. The following value E m+1 is greater than the current value E m The energy input E increases with the number of repetitions of the power loop. • 104: Initializing the cycle loop 108 with n := 1. • 105: In one cycle C, the weakening line 9 is swept once with the laser beam 3, whereby the energy input of the laser beam 3 exceeds the upper limit E m exhibits. • 106: Incrementing the numerator n by 1. • 107: If the numerator n is not greater than the number N m the repetitions of cycle C with the upper limit E mIf the energy input is within the specified range, cycle loop 108 is repeated. Otherwise, cycle loop 108 is terminated. • 109: Increment the numerator m by 1. • 110: If the counter m is not greater than the number M of repetitions of the performance loop 111, the performance loop 111 is repeated. Otherwise, the performance loop 111 is terminated. • 112: End of the schedule

[0054] In an advantageous embodiment of model 4, the power loop 111 can be terminated before reaching the number M of repetitions of the power loop 111 if the target value of the remaining wall thickness 25 is reached in all segments of the weakening line 9. This advantageous embodiment allows for a shorter machining time of the workpiece 1.

[0055] In another advantageous embodiment of example 4, the cycle loop 108 can be terminated before reaching the number N. mThe repetitions of cycle loop 108 are aborted when the target value of the remaining wall thickness 25 is reached in all segments of the weakening line 9. This advantageous variant allows for a shorter machining time of workpiece 1.

[0056] An exemplary variant of embodiment 4, not shown, uses the following parameters. The maximum energy input is the energy input that the laser beam 3 can input into the material of the workpiece 1 at maximum power. • M = 3. • N1 = 20%, E1 = 30% of the maximum energy input. • N2 = 4, E2 = 35% of the maximum energy input. • N3 = 4, E3 = 40% of the maximum energy input.

[0057] Using these parameters, the weakening line 9 of workpiece 1 is produced as follows: • The performance loop 111 is executed 3 times. • In the first iteration of the power loop 111, the cycle loop 108 is traversed 20 times with an upper limit E of the energy input of 30% of the maximum energy input. • In the second iteration of the power loop 111, the cycle loop 108 is traversed 4 times with an upper limit E of the energy input of 35% of the maximum energy input. • In the third iteration of the power loop 111, the cycle loop 108 is traversed 4 times with an upper limit E of the energy input of 40% of the maximum energy input.

[0058] In another variant of embodiment 4, the energy input of the laser beam 3 can be increased depending on how many points of impact of the laser beam 3 along the attenuation line 9 have already reached the desired residual wall thickness 25. Two cases can be distinguished as examples of this dependency. • First case: The energy input is significantly increased in one of the cycles following the respective cycle of relative motion if the residual wall thickness 25 has not yet been reached at any impact point or at only a few impact points in the respective cycle. • Second case: The energy input is only slightly increased in one of the cycles following the respective cycle of relative motion if the residual wall thickness has already been reached at most of the impact points in the respective cycle.

[0059] A significant increase could be, for example, an increase of 20%. A minor increase could be, for example, an increase of 10%.

[0060] The next variant of the exemplary embodiment uses the following exemplary parameters: • M = 3. • N1 = 20%, E1 = 30% of the maximum energy input. • N2 = 4, E2 = 36% of the maximum energy input if the desired residual wall thickness 25 is already achieved at less than 50% of the points of impact of the laser beam 3 along the attenuation line 9, E2 = 33% of the maximum energy input otherwise. • N3 = 4, E3 = 45% of the maximum energy input if the desired residual wall thickness 25 is already achieved at less than 50% of the points of impact of the laser beam 3 along the attenuation line 9, E3 = 40% of the maximum energy input otherwise.

[0061] The flexible increase of the energy input depending on how many impact points the desired residual wall thickness 25 has already been reached in the respective cycle leads to a reduction in the processing time of the workpiece 1.

[0062] Fig. 5a to Fig. Figures 5f show, as a further embodiment, the energy input E of the laser as a function of time t in different cycles of the relative motion between the workpiece 1 and the laser beam 3 along the attenuation line 9. The energy input E shown corresponds to that in Fig. 3 weakening line 9 shown with segments 32, 33, 34, 35.

[0063] Fig. Figure 5a shows the energy input E in the first cycle of the relative motion. The upper limit of the energy loss is set at E1. Over a time interval t 32 The laser beam introduces 3 energy into segment 32 of the attenuation line 9 and creates a sequence of slits and ridges. The same applies to the time intervals t. 33 , t 34 , t 35 for segments 33, 34, 35 of weakening line 9.

[0064] Fig. Figure 5b shows the energy input E after one or more repetitions of the relative motion cycle. In segments 32 and 33, the target value for the remaining wall thickness has already been reached. Therefore, in the time intervals t 32 , t 33 No further energy input E occurs. In segments 34 and 35, the wear threshold is higher than the upper limit E1 of the energy input E. Therefore, the target value of the remaining wall thickness is not reached in segments 34 and 35, even with further repetitions of the cycle with the upper limit E1 of the energy input E.

[0065] Fig. Figure 5c shows a repetition of the cycle with an upper limit E2 of the energy input E. E2 is greater than E1. In the time intervals t 34 , t 35 A further energy input E takes place with the upper limit E2.

[0066] Fig. Figure 5d shows the energy input E after one or more repetitions of the cycle with an upper limit E2. In segment 34, the target value for the remaining wall thickness has already been reached. Therefore, in the time interval t 34 No further energy input E occurs. In segment 35, the wear threshold is higher than the upper limit E2 of the energy input E. Therefore, the target value of the remaining wall thickness is not reached in segment 35, even with further repetitions of the cycle with the upper limit E2 of the energy input E.

[0067] Fig. Figure 5e shows a repetition of the cycle with an upper limit E3 of the energy input E. E3 is greater than E2. In the time interval t 35 A further energy input E with the upper limit E3 takes place.

[0068] Fig.Figure 5f shows the energy input E after one or more repetitions of the cycle with an upper limit E3. The target value for the remaining wall thickness has now also been reached in segment 35. Therefore, the process takes place during the time interval t. 35 No further energy input E takes place. The creation of the weakening line 9 in workpiece 1 is complete.

[0069] The solution according to the invention is not limited to the described embodiments. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102013104138 B3

[0006] DE 102020131069 B4

[0007]

Claims

[1] Method for producing a weakening line (9) in a workpiece (1) by material removal with a laser beam (3), comprising Providing the workpiece (1) with a viewing side (7) and a reverse side (8) facing away from the viewing side, Impact of the laser beam (3) on the back (8), Controlling the energy input of the laser beam (3) into the workpiece (1) in a pulsed operating mode by means of a control unit (6), Performing a relative movement between the workpiece (1) and the laser beam (3) along the attenuation line (9), Crossing the weakening line (9) in one cycle of relative motion, at least a simple repetition of the cycle of relative motion, Control of the energy input depending on the respective point of impact of the laser beam (3) along the attenuation line (9) by means of the control unit (6), characterized by , that in one of the cycles following the respective cycle of relative motion, the control unit (6) increases the energy input at at least one of the respective points of impact of the laser beam (3) along the attenuation line (9). [2] Method according to claim 1, further comprising repeatedly increasing the energy input of the laser beam (3) at the respective point of impact of the laser beam (3) along the attenuation line (9) in further repetitions of the cycle of relative motion up to an upper limit of the energy input. [3] Method according to claim 2, characterized by , that the upper limit of the energy input is higher than a removal threshold, wherein material removal occurs when the energy input is higher than the removal threshold and in particular the removal threshold depends on the respective point of impact of the laser beam (3) along the attenuation line (9). [4] Method according to claim 2 or 3, characterized by, that the upper limit of the energy input is not higher than a damage threshold of the workpiece (1), whereby, in the case of an energy input higher than the damage threshold of the workpiece (1), in particular damage to the workpiece (1) that is visible on the viewing side (7) will occur. [5] Method according to any of the preceding claims, characterized by , that the material removal is carried out by ablation with ultrashort pulses of the laser beam (3) with a duration of a single pulse shorter than 1000 fs or by vaporization with short pulses of the laser beam (3) with a duration of a single pulse of 1 µs - 1000 µs. [6] Method according to any of the preceding claims, characterized by , that the weakening line (9) comprises an alternating series of slots (22, 23, 24) and ribs (20, 21), wherein the slots (22, 23, 24) have a slot length of 0.5 mm - 5 mm and the ribs (20, 21) have a rib length of up to ½ the slot length. [7] Method according to one of the preceding claims, further comprising detecting the portion of the laser beam (3) passing through the workpiece (1) in a sensor unit (5) and calculating a residual wall thickness of the workpiece (1) at the respective point of impact of the laser beam (3) along the attenuation line (9) from the detected portion of the laser beam (3) passing through the workpiece (1) in the control unit (6). [8] Method according to claim 7, further comprising reducing the energy input at the respective point of impact of the laser beam (3) along the attenuation line (9) to substantially zero when a desired residual wall thickness (25) is reached at the respective point of impact of the laser beam (3) along the attenuation line (9). [9] Use of a method according to any of the preceding claims, wherein the workpiece (1) comprises leather or textile. [10] Device (10) in which the method according to one of the preceding claims can be carried out.

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