Controllable flow device for a laser machining head

Abstract

Laser machining head (1) with a flow device (6) for generating at least one cross flow (7) that penetrates a region between the laser machining head (1) and a workpiece (5), wherein the cross flow (7) can be controlled by a control unit depending on emissions from the welding process.

Description

[0001] Controllable flow device for a laser processing head

[0002] Field of invention

[0003] The invention relates to a laser processing head for processing a workpiece, in particular for cutting or welding, and to a method for processing a workpiece.

[0004] Background of the invention

[0005] German patent DE 102014203576 discloses a laser processing head with a nozzle for generating a flow. According to the patent, this is intended to reduce the interaction between emissions emerging from the workpiece and the components to be protected.

[0006] Summary of the invention

[0007] It has been shown that generating such a flow is very energy-intensive. This results in very high operating costs. Furthermore, energy-intensive applications tend to have a poor CO2 balance.

[0008] The present invention is based on the objective of developing a laser processing head that has reduced energy consumption and reduces the interaction between emissions from the workpiece and the components to be protected. The invention also aims to provide a method using the laser processing head according to the invention.

[0009] With regard to the laser processing head, the problem is solved by a laser processing head having the features of claim 1. With regard to the method, the problem is solved by a method having the features of claim 10.

[0010] The laser processing head includes a flow device for generating at least one transverse flow. This transverse flow penetrates a region between the laser processing head and the workpiece. The laser processing head is designed so that the transverse flow can be controlled by a control unit based on emissions from the welding process. The control unit can reduce, and in particular, shut off, the volume flow of the transverse flow. This reduces the energy consumption of the laser processing head compared to a transverse flow with a constant volume flow.

[0011] In another aspect, the control unit reduces the crossflow volume flow by pulsating the crossflow on and off. Compared to continuous adjustment, especially with analog control, the power loss of the control unit is comparatively low with pulsed on / off switching. On average, the crossflow volume flow is reduced compared to a crossflow with a constant volume flow.

[0012] The laser processing head is designed for use in cutting or welding. In such applications, the workpiece is processed with high beam intensities. These high beam intensities generate emissions from the welding process, particularly metal spatter or vapor. The crossflow is intended to keep these emissions from the welding process as far away as possible from sensitive components, especially optical components used to prepare the laser beam.

[0013] The laser processing head is specifically designed for use in deep penetration welding. Deep penetration welding involves processing the material with very high beam intensities. Unlike heat conduction welding, this process generates metal vapor in addition to the molten metal. This vapor partially displaces the molten metal, leading to the formation of a vapor capillary, also known as a keyhole. Laser deep penetration welding is characterized by high process speeds. The heat-affected zone is always narrowly defined, resulting in correspondingly low material distortion. The result is a narrow, uniformly structured weld seam, whose depth is typically significantly greater than its width. The formation of metal vapor further promotes the formation of metal spatter. Crossflow is intended to keep emissions from the welding process, particularly the metal vapor, away from sensitive components.

[0014] In particular, the crossflow during the welding process is controllable. This requires a fast reaction time so that emissions from the welding process can be detected quickly and the crossflow can be generated rapidly. If there are no emissions from the welding process, the crossflow is deactivated. Specifically, the crossflow exhibits a reduced flow velocity when there are no emissions from the welding process. Thus, the crossflow is not continuously active, and energy consumption is reduced. This is especially advantageous in welding processes with low emissions.

[0015] Advantageously, the laser beam has a direction of propagation. The laser's direction of propagation runs from the laser to the workpiece. The direction of propagation of the crossflow runs perpendicular to the laser's direction of propagation. In particular, the direction of propagation of the crossflow runs perpendicular, or even more advantageously, approximately perpendicular, to the laser's direction of propagation.

[0016] The term "perpendicular" refers to the generally accepted mathematical definition that the scalar product is zero when two vectors of an n-dimensional space are "perpendicular" to each other, where n is greater than zero and is an element of the natural numbers.

[0017] "Approximately perpendicular" means that two vectors are perpendicular to each other, although they may deviate from this perpendicular angle to such an extent that the technically desired effect is still achieved. In particular, the technically desired effect is achieved with angular deviations of ± 20°.

[0018] In one aspect, a laser processing head is provided for generating at least two crossflows. These at least two crossflows are individually controllable. In particular, one of the at least two crossflows can be in an activated state, while the other of the at least two crossflows is in a deactivated state.

[0019] In one aspect, a laser processing head is provided for generating three to five cross flows.

[0020] In one aspect, the at least two crossflows overlap in such a way that continuous protection is provided. In particular, the overlap of the at least two crossflows is such that in a region between the at least two crossflows, the flow velocity is high enough to protect sensitive components.

[0021] In one aspect, the at least two crossflows are arranged side by side. "Side by side" here means that the at least two crossflows are arranged in a horizontal line. However, it is also possible for the at least two crossflows to be arranged one above the other. "Arranged one above the other" here means that they extend vertically away from the workpiece.

[0022] In one aspect, the crossflow spreads a spreading medium. This spreading medium contains a gas, in particular a protective gas or atmospheric air. Advantageously, a protective gas is used to reduce oxidation. However, atmospheric air can also be used to reduce costs. In an application according to the invention, protective gases such as argon, helium, and nitrogen are typically used.

[0023] In one aspect, the focused laser beam propagates in a single direction. In this configuration, the workpiece is positioned so that it lies downstream of the laser beam. The flow device is located laterally to the side of the focused laser beam. In such an arrangement, the crossflow can carry the working fluid located between the flow device and the workpiece in a transverse direction at least far enough that the working fluid flows over a processing zone. This deflects the emissions from the welding process in such a way that they cannot damage sensitive components.

[0024] In other words, arranging the workpiece in the direction of the laser beam means that the laser emits a laser beam. The laser beam passes through an optical unit. Specifically, the optical unit focuses the laser beam. After passing through the optical unit, the focused laser beam strikes the workpiece to be processed.

[0025] In one aspect, a focusing optic focuses the laser beam. Thus, the focusing optic forms the focused laser beam. In another aspect, the crossflow is designed in such a way that it protects sensitive components of the laser, especially the surrounding components of the laser such as the laser's focusing unit.

[0026] In one aspect, the flow unit comprises at least one nozzle. A single nozzle forms a single crossflow. In an activated state, the spreading medium flows from the at least one nozzle. In a deactivated state, the spreading medium can flow from the at least one nozzle at a reduced flow velocity. It is also possible that the spreading medium does not flow from the at least one nozzle in a deactivated state.

[0027] In one aspect, at least one nozzle of the flow unit is designed in a linear shape.

[0028] In one aspect, the flow unit has a width of 30 mm to 300 mm.

[0029] In one aspect, the spreading medium flows through the at least one nozzle at a pressure of at least 1 bar.

[0030] In one aspect, the workpiece and at least one nozzle are spaced apart. The distance is less than 740 mm and more than 30 mm.

[0031] In another aspect of the invention, a method for laser processing of a workpiece with the laser processing head is provided, wherein the cross-flow is controlled during the processing of the workpiece.

[0032] In one aspect, the emissions from the welding process move in a specific direction. The crossflow deflects the direction of these emissions away from the sensitive components of the laser. Specifically, the emissions are redirected away from surrounding sensitive components.

[0033] In one aspect, the crossflow is controlled by at least one valve. This valve has switching times of less than 5 ms. In another aspect, the control unit comprises sensors and an evaluation unit. The sensors detect emissions from the welding process and deliver corresponding data to the evaluation unit. Based on this data, the evaluation unit calculates the emission trajectory and, depending on this, controls the activation or deactivation of the crossflow. The calculation of the emission trajectory can be implemented in various ways to meet the requirements of the respective application.

[0034] In one aspect, control is achieved through a simple, sensor-driven circuit. A sensor, such as a photodiode or photodiode array, detects the emissions, and the evaluation unit activates or deactivates the crossflow directly or with a time delay. This option is particularly advantageous in applications where high precision is not required and the simple circuit allows for cost-effective and rapid implementation.

[0035] In one aspect, the evaluation unit calculates the trajectory of emissions, particularly weld spatter or metal spatter, based on data from a camera or similar sensor. This calculation can be performed, for example, using image processing or other algorithms. This option offers maximum precision and enables targeted and needs-based control of the crossflow.

[0036] In one aspect, the control system operates without sensors. Here, the evaluation unit calculates the trajectory of emissions, particularly weld spatter or metal spatter, based on the data and parameters of the welding process. This data and these parameters are acquired and calculated during machine setup. In other words, the data is acquired and calculated before the welding process begins. Therefore, the state of the crossflow remains constant throughout the welding process. This means that the crossflow is either activated or deactivated during the welding process.

[0037] In one aspect, at least one crossflow is deactivated during the welding process. Specifically, the remaining crossflows are controlled as described above. In another aspect, the sensors of the control unit, particularly the camera, can be used to assess process quality. Specifically, the sensors are a diode array. A photodiode array is a semiconductor device on which several photodiodes are arranged in a row. A diode array comprises at least two photodiode arrays.

[0038] In one aspect, a workpiece is processed using the method described above. In particular, the workpiece is manufactured using the method described above.

[0039] The individual features can of course also be combined with each other, which can sometimes result in advantageous effects that go beyond the sum of the individual effects.

[0040] List of characters

[0041] Further details and advantages of the invention will become clear with reference to the exemplary embodiments illustrated in the drawings. These schematically show:

[0042] Fig. 1 shows a cross-section through a laser setup,

[0043] Fig. 2 shows a flow device in a perspective view.

[0044] Detailed description of exemplary embodiments. Fig. 1 shows an exemplary embodiment of a laser processing head 1 with a flow device 6 and a laser setup 8. The laser setup 8 comprises a laser 9 for generating a laser beam, a focusing optic 10 for generating a focused laser beam 2, a flow device 6, and a processing table 11. A workpiece 5 is arranged on the processing table 11. The flow optic includes sensors 12. Advantageously, the workpiece 5 is made of metal. Due to the high intensity of the focused laser beam 2, the workpiece 5 liquefies at the processing zone 4. This can result in emissions from the welding process. Among other things, the emissions from the welding process can be metal spatter. Fig. 1 shows a trajectory 14 of a weld spatter. The laser 9 emits an unfocused laser beam.The unfocused laser beam is focused in the focusing optics 10. A focused laser beam 2 emerges from the focusing optics 10. The focused laser beam 2 propagates in a single direction. This direction runs from the laser 9 to the workpiece 5. In other words, the workpiece is positioned downstream of the laser in the direction of the focused laser beam 2. The focused laser beam 2 strikes the surface of the workpiece 5 at approximately a right angle. The flow device 6 is positioned laterally next to the focused laser beam. The transverse flow 7 generated by the flow device 6 flows over a processing zone 4. A working medium is located between the workpiece 5 and the flow device 6. The transverse flow 6 carries the working medium with it. In particular, the working medium is integrated into the transverse flow 6.

[0045] It can also be provided that the crossflow 7, in particular the propagation medium of the crossflow 7, comes into contact with the processing zone 4. In other words, it can be provided that the crossflow 7, in particular the propagation medium of the crossflow 7, reaches the processing zone and interacts with it.

[0046] According to the invention, the flow device 6 generates at least one transverse flow 7. The transverse flow 7 penetrates an area between the laser processing head 1 and the workpiece 5. The direction of the transverse flow 7 is approximately parallel to the processing table 11. The transverse flow 7 can be controlled by a control unit (not shown here) depending on emissions from the welding process. The trajectory 14 of a weld spatter clearly shows that the transverse flow 7 deflects the direction of movement of the weld spatter. This prevents the weld spatter from striking sensitive components such as the focusing optics 10. Thus, the flow device 6, and in particular the transverse flow 7, protects the focusing optics 10. At a first time t1, the weld spatter exits the workpiece 5. The sensor 12 detects the metal spatter at a second time t2.At a third time point t3, the control unit (not shown here) activates the crossflow 7 such that the direction of movement of the weld spatter changes. At a fourth time point t4, the control unit (not shown here) deactivates the crossflow 7. The first time point t1 is followed by the second time point t2. The second time point t2 is followed by the third time point t3. The third time point t3 is followed by the fourth time point t4. Figure 2 schematically shows a flow device 6 and the sensor system 12. The flow device 6 generates four crossflows 7, a to 7, d. The flow device 6 comprises four nozzles 15, a to 15, d. Each of the four crossflows 7, a to 7, d flows from its own nozzle 15, a to 15, d. The spreading medium flows from the individual nozzles 15, a to 15, d at a pressure of at least 1 bar. The flow unit 6 has a width B.The individual nozzles 15, a to 15, d are spaced apart by a distance D. The sensor 12 is located below the flow device 6. Adjacent to the flow device 6 is a metal splash 16 with trajectory 14. The metal splash 16 moves with the time-varying velocity vector 17. Trajectory 14 shows the path along which the metal splash 16 moves.

[0047] According to the invention, the sensor 12 detects the metal splash 16. Depending on the overall laser setup 8 and the trajectory 14, one or more of the cross-flows 7, a to 7, d are activated. This allows the direction of movement of the metal splash 16 to be changed. As a result, the metal splash 16 can be redirected away from sensitive components such as the focusing optics 10 (not shown here). This reduces or prevents contamination of the sensitive components.

[0048] The crossflow 7 spreads a spreading medium. The spreading medium contains a gas, in particular a protective gas. The protective gas reduces oxidation on the workpiece 5. Argon, helium, or nitrogen are preferably used as the protective gas.

[0049] The method according to the invention provides that the crossflow 7 is controlled during the machining of the workpiece. Advantageously, the at least one crossflow 7 is controlled such that it is activated and deactivated. An activated state represents a state at full operating pressure, thus enabling the crossflow 7 to deflect the emissions of the welding process. In a deactivated state of the crossflow 7, this is switched off, so that the flow velocity is zero after a certain recovery time. The recovery time is the time required for the crossflow 7 to come to a complete stop from the moment it is switched off. In an alternative embodiment, it can also be provided that a deactivated state of the crossflow 7 only represents a state with a reduced flow velocity.In general, however, the flow velocity of the crossflow 7 in the active state is greater than the flow velocity in the deactivated state.

[0050] Advantageously, the method according to the invention redirects the direction of propagation of the emissions from the welding process to a different direction of propagation, such that the other direction of propagation points away from the sensitive components of the laser. This enables the crossflow 7.

[0051] According to the invention, the cross-flow 7 is controlled by at least one valve. The at least one valve has switching times of less than 5 ms. Such short switching times make it possible to control the cross-flow 7 during the process, in particular to activate and deactivate it during the process.

[0052] The method according to the invention provides that the control unit comprises an evaluation unit and sensors. The evaluation unit calculates the path of the emissions from the welding process. To calculate the path, the evaluation unit uses data from the sensors. Alternatively, the sensors can be a camera.

[0053] The reference symbols used serve only to increase clarity and should in no way be considered restrictive, the scope of protection of the invention being defined by the claims.

Claims

Patent claims Claim 1 Laser processing head (1) with a flow device (6) for generating at least one transverse flow (7) which penetrates an area between laser processing head (1) and workpiece (5), characterized by the fact that the crossflow (7) can be controlled by a control unit depending on emissions from the welding process. Claim 2 Laser processing head (1) according to claim 1, characterized in that at least two transverse flows (7) are provided, wherein the at least two transverse flows (7) are individually controllable. Claim 3 Laser processing head (1) according to one of the preceding claims, characterized in that the crossflow (7) spreads a propagation medium, wherein the propagation medium contains a gas, in particular a protective gas or atmospheric air. Claim 4 Laser processing head (1) according to one of the preceding claims, characterized in that the focused laser beam (2) propagates in a beam direction, wherein the workpiece (5) is arranged in the beam direction after the laser, and that the flow device (6) is arranged laterally next to the focused laser beam (2) in order to carry the propagation medium located between the flow device (6) and the workpiece (5) along by the transverse flow (7) in a transverse direction (13) at least so far that it flows over a processing zone (4). Claim 5 Laser processing head (1) according to one of the preceding claims, characterized in that the crossflow (7) is designed in such a way as to protect sensitive components of the laser, in particular the focusing optics of the laser. Claim 6 Laser processing head (1) according to one of the preceding claims, characterized in that the flow device (6) comprises at least one nozzle, wherein in an activated state the propagation medium flows out of the at least one nozzle. Claim 7 Laser processing head (1) according to one of the preceding claims, characterized in that the flow unit (6) has a width (B) of 30 mm to 300 mm. Claim 8 Laser processing head (1) according to one of claims 3 to 7, characterized in that the propagation medium flows through the at least one nozzle at a pressure of at least 1 bar. Claim 9 Laser processing head (1) according to one of claims 6 to 8, characterized in that the workpiece (5) and the at least one nozzle are spaced apart by a distance (D), wherein the distance (D) is less than 740 mm and more than 30 mm. Claim 10 Method for laser processing of a workpiece (5) with a laser processing head according to one of the preceding claims, characterized in that the cross-flow (7) is controlled during the processing of the workpiece. Claim 11 Method according to claim 10, characterized in that the emissions of the welding process move in a direction of movement, wherein the crossflow (7) deflects the direction of movement of the emissions of the welding process into a direction of movement of the emissions of the welding process away from the sensitive components of the laser. Claim 12 The method according to claim 10 or 11, characterized in that the cross-flow (7) is controlled by at least one valve, wherein the at least one valve has switching times of less than 5 ms. Claim 13 Method according to one of claims 10 to 12, characterized in that the control unit comprises an evaluation unit and a sensor system (12), wherein the evaluation unit calculates the trajectory of the emissions from the welding process, in particular weld spatter or metal spatter, from the data of the sensor system (12).

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