Method for operating a laser machine tool, and laser machine tool

Abstract

The invention relates to a method for operating a laser machine tool (10) for working a workpiece (12) by means of a laser beam (14), wherein, during the working of the workpiece (12), the laser beam (14) and a process gas (30, 32, 34) exit a nozzle unit (16) and are directed onto the workpiece (12) by means of the nozzle unit (16), wherein the process gas (30, 32, 34) can be selected from a plurality of process gases (30, 32, 34) by means of a gas control unit (24) and the selected process gas (30, 32, 34) is guided to the nozzle unit (16) via a pressure-control valve (58) of the gas control unit (24) in order to adjust a target pressure, wherein the method comprises: carrying out a test sequence, comprising: - selecting a process gas (30, 32, 34) from the plurality of process gases (30, 32, 34) by means of the gas control unit (24), - setting a target pressure curve for the selected process gas (30, 32, 34) by means of the pressure control valve (58), wherein the target pressure curve has a first target pressure value (74) for a first time period (72) and a second target pressure value (78) for a second time period (76), - measuring an actual pressure curve (82) at an outlet (62) of the pressure-control valve (58), - creating test data, wherein the test data contains information relating to the selected process gas (30, 32, 34), the target pressure curve (66) and the actual pressure curve (82); analysing the test data for the presence of an error.

Description

[0001] Title: Method for operating a laser processing machine and laser processing machine

[0002] Description

[0003] The invention relates to a method for operating a laser processing machine and a laser processing machine.

[0004] Process gases are frequently used during the processing of a workpiece with a laser processing machine. For example, the processing of the workpiece might involve cutting it with a laser beam from the laser processing machine, where the process gas is used as a cutting gas to expel any molten material. Alternatively, the processing of the workpiece might involve creating a weld using the laser beam, where the process gas is used as a shielding gas, for example, to prevent oxidation of the workpiece during the weld process.

[0005] In US 2018 / 0015583 A1, a narrowing of an exit tube is diagnosed based on a pressure drop.

[0006] The invention is based on the objective of providing a method for operating a laser processing machine and providing a laser processing machine, each of which has improved properties, in particular enabling a reliable determination of whether a fault is present or not.

[0007] The invention solves this problem by providing a method with the features of claim 1 and a laser processing machine with the features of claim 10. Advantageous embodiments and further developments of the invention are set forth in the dependent claims.

[0008] A method according to the invention is designed for operating a laser processing machine for processing a workpiece using a laser beam. During processing, the laser beam and a process gas exit a nozzle unit and are directed onto the workpiece by means of the nozzle unit. The process gas can be selected from a plurality, in particular 3 or 4, of process gases by means of a gas control unit of the laser processing machine. The selected process gas is fed to the nozzle unit via a pressure regulating valve of the gas control unit for setting a target pressure.The procedure comprises: a) performing a test sequence, including: selecting a process gas from the plurality of process gases using the gas control unit, setting a target pressure profile for the selected process gas using the pressure control valve, wherein the target pressure profile has a first target pressure value for a first period and a second target pressure value for a second period, measuring an actual pressure profile at an outlet of the pressure control valve, generating test data, wherein the test data contains information about the selected process gas, the target pressure profile and the actual pressure profile; and b) analyzing the test data for the presence of a fault.

[0009] Advantageously, by setting a target pressure profile and measuring the actual pressure profile, various errors can be precisely detected. In particular, by selectively choosing a target pressure profile, errors that only occur under specific operating conditions can be identified. The target pressure profile can be designed in such a way that errors occurring only under certain operating conditions become apparent. This method thus enables a reliable determination of whether or not errors are present.

[0010] The laser processing machine can be a laser cutting machine or a laser welding machine. The processing of the workpiece can involve cutting or welding. The laser cutting machine can be designed to generate the laser beam.

[0011] The majority of process gases can contain compressed air, nitrogen, and oxygen.

[0012] The pressure control valve can have a single inlet. The inlet of the pressure control valve can be supplied with the selected process gas. The pressure control valve can have a single outlet. The outlet of the pressure control valve can be connected to the nozzle unit via a gas line, so that the selected process gas exiting the pressure control valve outlet is directed to the nozzle unit.

[0013] Selecting the process gas can involve pressurizing the inlet of the pressure control valve with the selected process gas. Measuring the actual pressure profile can be performed while the inlet of the pressure control valve is being pressurized with the selected process gas.

[0014] The test procedure can be performed during the productive operation of the laser processing machine using a target pressure profile for machining a workpiece. Through continuous generation and analysis of the test data, errors can be detected early.

[0015] Creating test data can include: creating a file, especially a compressed one, particularly in ZIP file format, containing information about the selected process gas, the target pressure profile, and the actual pressure profile.

[0016] The laser processing machine can have a process gas inlet. This inlet can be connected to a pressure source for supplying the majority of the process gases. Preferably, the pressure source can supply compressed air, nitrogen, and oxygen.

[0017] The gas control unit can consist of a plurality of valves and lines.

[0018] The laser processing machine may have a control unit for controlling the gas control unit. The control unit is designed to control the gas control unit in such a way that a process gas is selected and the inlet of the pressure regulating valve is supplied with the selected process gas.

[0019] The target pressure profile can exhibit a typical profile of the selected process gas for machining the workpiece. For example, when cutting the workpiece, lower cutting gas pressures can be used initially, followed by higher cutting gas pressures.

[0020] The target pressure profile can be a predefined profile. The target pressure profile can depend on the selected process gas.

[0021] The procedure may include: transmitting the test data to an analysis unit for analysis. The analysis unit may comprise an electronic processing unit, in particular a computer and / or a microcontroller. The analysis unit may be integrated as part of the laser processing machine or as a separate unit. The transmission of the test data may be as a file or as a data stream.

[0022] The test data can be transmitted via the internet. This allows for online and / or remote diagnosis, which is advantageous.

[0023] The procedure can include: displaying the recorded measurement data as well as any detected deviations in the measurement data. The procedure can also include: indicating whether or not an error has been identified based on the analysis of the test data. Advantageously, this allows a user of the laser processing machine to determine whether or not an error exists. The display can be provided via a screen on the laser processing machine.

[0024] The procedure can include issuing instructions for correcting the fault if one is identified based on the analyzed test data. These instructions could, for example, involve replacing a valve.

[0025] Analyzing the test data can include determining whether the error is present or not.

[0026] The first and second time periods can depend on the test procedure. The first and second time periods can be the same. The first and / or second time periods can each have a duration of, for example, 15 seconds.

[0027] Another aspect of the process may be that cutting problems can be reduced and the occurrence of processing errors, such as spatter of material during laser processing, due to undetected defects can be reduced or completely avoided.

[0028] Another benefit of this method is the identification of faults, allowing service calls to be directed specifically towards their rectification. In particular, it can prevent the unnecessary replacement of functional components of the laser processing machine, especially the gas control unit, thus avoiding unnecessary costs.

[0029] Another aspect of the procedure is that it can be performed as a complete run together with one or more other diagnostic functions, in particular axle diagnostics.

[0030] In a further development of the procedure, the process is repeated at a predetermined time interval and / or initiated manually and / or triggered by a predetermined event. Advantageously, repeating the procedure at predetermined intervals allows the condition of the laser processing machine to be documented throughout its lifecycle. The predetermined time interval could be, for example, daily, monthly, semi-annually, or annually. Advantageously, the test sequence can be initiated manually as needed, for example, in the event of a fault. This allows the cause of the fault to be identified more quickly. A predetermined event could be, for example, a valve replacement, a nozzle replacement, or an error message. Advantageously, the predetermined event can be detected automatically, and the test sequence initiated automatically.A test run in new condition can be used to determine reference values.

[0031] In a further development of the procedure, the test sequence is performed for each process gas. Advantageously, this allows it to be determined whether each process gas can be directed accurately onto the workpiece for machining. In other words, the test sequence can be repeated until it has been completed for each process gas.

[0032] In a further development of the procedure, the first and second target pressure values ​​differ. This advantageously allows for the detection of errors that only occur under specific operating conditions. For example, the difference between the first and second target pressure values ​​can be at least 3 bar. Additionally or alternatively, the target pressure profile includes a third target pressure value with a predetermined value, particularly 0 bar, for a third period located between the first and second periods. This third target pressure value can be referred to as the residence time. During this third period, the process gas can be switched off and then on again. This allows the test sequence to be advantageously designed similarly to a machining process.

[0033] In a further development of the procedure, if the selected process gas is oxygen, the target pressure curve has a maximum target pressure value of 12 bar. Additionally or alternatively, if the selected process gas is nitrogen, the target pressure curve has a maximum target pressure value of 25 bar. Additionally or alternatively, if the selected process gas is compressed air, the target pressure curve has a maximum target pressure value of 5 bar. Advantageously, these maximum target pressure values ​​allow for the detection of numerous different errors when using compressed air, nitrogen, or oxygen as the process gas.

[0034] In a further development of the procedure, the analysis of the test data includes identifying an insufficient cross-section in the supply line to the gas control unit as a fault if the first target pressure value is not 0 bar and the actual pressure curve drops during the first period, and / or if the second target pressure value is not 0 bar and the actual pressure curve drops during the second period. Advantageously, this allows determination of whether the selected process gas is being supplied to the gas control unit in a sufficient quantity. For example, a kink in the supply line and / or the use of a supply line with an insufficient cross-section can lead to the detection of such a fault.

[0035] In a further development of the procedure, the analysis of the test data includes identifying wear of the gas control unit as a fault if the actual pressure profile in the first period shows an overshoot above the first target pressure value by an amount greater than a predefined overshoot limit, and / or if the actual pressure profile in the second period shows an overshoot above the second target pressure value by an amount greater than the predefined overshoot limit. Advantageously, this allows for the reliable identification of wear of the gas control unit. The overshoot limit can be, for example, 0.5 bar. The overshoot can occur, for example, due to a stuck valve in the gas control unit.

[0036] In a further development of the procedure, the analysis of the test data includes identifying wear of the gas control unit as a fault if the actual pressure profile in the first period exhibits a periodic oscillation around the first setpoint pressure value with an amplitude greater than a predefined amplitude limit, and / or if the actual pressure profile in the second period exhibits a periodic oscillation around the second setpoint pressure value with an amplitude greater than the predefined amplitude limit. Advantageously, this allows for the reliable identification of wear of the gas control unit. The amplitude limit can be, for example, 0.2 bar. The periodic oscillation can occur, for example, due to excessive regulation of the process gas pressure by the gas control unit.

[0037] In a further development of the procedure, the analysis of the test data includes identifying insufficient inlet pressure at an inlet of the pressure control valve as a fault if the pressure difference between an average value of the actual pressure profile in the first period and the first setpoint pressure exceeds a pressure limit value, and / or if the pressure difference between an average value of the actual pressure profile in the second period and the second setpoint pressure exceeds the pressure limit value. Advantageously, this allows for the reliable identification of insufficient inlet pressure. The pressure limit value could, for example, be 0.2 bar.

[0038] A laser processing machine according to the invention is designed for processing a workpiece using a laser beam. The laser processing machine is configured to perform a previously described method. The laser processing machine comprises a nozzle unit for directing the laser beam and the process gas onto the workpiece, a gas control unit for selecting the process gas from a plurality of process gases with a pressure control valve for setting a target pressure of the selected process gas, and a control unit. The selected process gas is fed to the nozzle unit via the pressure control valve. The pressure control valve has a pressure sensor for measuring the actual pressure profile at the outlet of the pressure control valve. The control unit is configured to generate the test data and analyze the test data for the presence of a fault.

[0039] Further advantages and advantageous embodiments of the invention can be seen from the figures, their description, and the claims. All features disclosed in the figures, their description, and the claims can be essential to the invention, both individually and in any combination. The figures show:

[0040] Fig. 1 shows a schematic representation of a laser processing machine,

[0041] Fig. 2 shows a graph of a pressure profile at an output of a pressure control valve of the laser processing machine from Fig. 1 over time,

[0042] Fig. 3 shows a graph of a pressure profile with a pressure drop at the outlet of the pressure control valve of the laser processing machine from Fig. 1 over time,

[0043] Fig. 4 shows a graph of a pressure profile with an overshoot at the output of the pressure control valve of the laser processing machine from Fig. 1 over time,

[0044] Fig. 5 shows a graph of a pressure profile with periodic oscillations at the output of the pressure control valve of the laser processing machine of Fig. 1 over time, and

[0045] Fig. 6 shows a graph of a pressure profile with an insufficient actual pressure profile at the output of the pressure control valve of the laser processing machine of Fig. 1 over time.

[0046] Fig. 1 shows a laser processing machine 10. The laser processing machine 10 is designed for processing a workpiece 12 using a laser beam 14 of the laser processing machine 10.

[0047] The laser processing machine 10 is a laser cutting machine, and processing the workpiece 12 is cutting the workpiece 12. The laser processing machine 10 has a nozzle unit 16, to which the laser beam 14 and a process gas 18 are supplied for cutting the workpiece 12. The laser beam 14 and the process gas 18 exit from a nozzle opening 20 of the nozzle unit 16.

[0048] The laser beam 14 and the process gas 18 are directed onto the workpiece 12 by means of the nozzle unit 16. The laser beam 14 locally melts the workpiece 12, and the process gas 18 expels the molten material. Simultaneously, the nozzle unit 16 is moved along a direction of movement 22, so that the laser beam 14 and the process gas 18 are guided over the workpiece 12. This creates a cut edge in the workpiece 12.

[0049] The laser processing machine 10 has a gas control unit 24 for supplying the process gas 18 to the nozzle unit 16. The gas control unit 24 is formed from a plurality of valves and lines.

[0050] The gas control unit 24 has a process gas inlet 26 for connection to a pressure source 28.

[0051] The pressure source 28 is configured to supply the laser processing machine 10 with a first process gas 30 in the form of compressed air, a second process gas 32 in the form of nitrogen, and a third process gas 34 in the form of oxygen. The first, second, and third process gases 30, 32, 34 are fed from the pressure source 28 to the process gas inlet 26 via separate supply lines 36. The supply lines 36 are connected to the process gas inlet 26 and the pressure source 28. The supply lines 36 extend from the pressure source 28 to the process gas inlet 26.

[0052] The laser processing machine 10 has a control unit 38 for controlling the gas control unit 24. The control unit 38 can select the process gas 30, 32, 34 which is supplied to the nozzle unit 16 by controlling the gas control unit 24.

[0053] The gas control unit 24 has a compressed air line 40 for conveying compressed air 30, a nitrogen line 42 for conveying nitrogen 32 and an oxygen line 44 for conveying oxygen 34.

[0054] The compressed air line 40 carries the compressed air 30 via a compressed air valve module 46 of the gas control unit 24. The nitrogen line 42 carries the nitrogen 32 via a nitrogen valve module 48 of the gas control unit 24. The oxygen line 44 carries the oxygen 34 via an oxygen valve module 50 of the gas control unit 24.

[0055] The compressed air valve module 46, the nitrogen valve module 48, and the oxygen valve module 50 each have a directional control valve (not shown) and a check valve (not shown). Each directional control valve can be controlled by the control unit 38 to introduce or shut off the respective process gas 30, 32, 34. Each check valve prevents process gas from being introduced from the laser processing machine 10 into the pressure source 28.

[0056] The compressed air line 40 leads from the compressed air valve module 46 into the nitrogen line 42, which in turn leads into a control valve module 52 of the gas control unit 24. The oxygen line 42 also leads into the control valve module 52.

[0057] The control valve module 52 has a compressed air / nitrogen directional control valve 54 and an oxygen directional control valve 56. The compressed air / nitrogen directional control valve 54 and the oxygen directional control valve 56 can be controlled by means of the control device 38 to introduce or shut off the respective process gas 30, 32, 34.

[0058] The control valve module 52 has a pressure regulating valve 58. The pressure regulating valve 58 has a single inlet 60, which is connected to the compressed air / nitrogen directional control valve 54 and the oxygen directional control valve 56. The pressure regulating valve 58 has a single outlet 62, which is connected to the nozzle unit 16. The pressure regulating valve 58 has a pressure sensor 64 for measuring the actual pressure at the outlet 62.

[0059] The control unit 38 is configured to specify a target pressure to the pressure regulating valve 58. The pressure regulating valve 58 opens until the specified target pressure is present at its output 62. This allows the control unit 38, together with the pressure regulating valve 58, to control the pressure applied to the nozzle unit 16. The control unit 38 is configured to detect the actual pressure using the pressure sensor 64 and to record a pressure curve at the output 62.

[0060] The control device 38 is configured to select one of the process gases 30, 32, 34 by means of the gas control unit 24. By selecting the process gas 30, 32, 34, the inlet 60 of the pressure regulating valve 58 is supplied with the selected process gas 30, 32, 34.

[0061] The control unit 38 specifies a target pressure profile for the selected process gas 30, 32, 34. The target pressure profile describes the change in the target pressure over time. Fig. 2 shows a graph of the target pressure profile 66, with time 68 on the x-axis and pressure 70 on the y-axis. The target pressure profile 66 is represented by a thin line in Fig. 2.

[0062] The target pressure curve 66 has a first target pressure value 74 for a first period 72 and a second target pressure value 78 for a second period 76. The first target pressure value 74 is constant over the first period 76, and the second target pressure value 78 is constant over the second period 76. The duration of the first period 72 and the duration of the second period 76 are equal. The first period 72 and the second period 76 can each have a duration of, for example, 15 seconds.

[0063] The first target pressure value, 74, differs from the second target pressure value, 78. The second target pressure value, 78, is twice the first target pressure value, 74. The second target pressure value, 78, is the maximum target pressure value of the target pressure curve, 66.

[0064] If the selected process gas is compressed air (30), the maximum target pressure value of the target pressure curve is 5 bar. If the selected process gas is nitrogen (32), the maximum target pressure value of the target pressure curve is 25 bar. If the selected process gas is oxygen (34), the maximum target pressure value of the target pressure curve is 12 bar.

[0065] The target pressure curve 66 has a third target pressure value of 0 bar for a third period 80, which lies between the first period 72 and the second period 76. Thus, the third period 80 separates the first period 72 from the second period 76.

[0066] The control unit 38 is designed to adjust the target pressure profile 66 by means of the pressure control valve 58. Simultaneously, while adjusting the target pressure profile, the control unit 38 measures the actual pressure profile 82 by means of the pressure sensor 64. The measured actual pressure profile 82 is shown with a thick line in Fig. 2.

[0067] Fig. 2 shows that the measured actual pressure curve 82 follows the target pressure curve 66.

[0068] The control unit 38 is designed to generate test data containing information about the selected process gas, the target pressure profile, and the actual pressure profile. The test data is stored by the control unit 38 in a compressed file, specifically in ZIP file format.

[0069] The control unit 38 is configured to select each of the process gases 30, 32, 34 sequentially in order to generate the test data for each of the process gases 30, 32, 34. The control unit 38 is configured to analyze the test data, in particular the actual pressure profile of each process gas 30, 32, 34, for the presence of errors. After analyzing the actual pressure profile 82 shown in Fig. 2, the control unit 38 detects no errors.

[0070] The control unit 38 is designed to repeat the selection of the process gases 30, 32, 34, the generation of the test data, and its analysis at a predefined time interval, for example, daily, monthly, semi-annually, or annually. Additionally, the selection of the process gases 30, 32, 34, the generation of the test data, and its analysis can be initiated manually. For example, a service technician can manually initiate the selection of the process gases 30, 32, 34, the generation of the test data, and its analysis during maintenance of the laser processing machine 10.

[0071] Figures 3 to 6 each show a further embodiment of the graph of Figure 2, whereby identical and functionally equivalent elements use the same reference numerals and in this respect reference can be made to the above explanations of the embodiment of Figure 2, so that essentially only the existing differences are discussed.

[0072] Fig. 3 shows a graph of the target pressure profile 66 and the actual pressure profile 82. The actual pressure profile 82 exhibits a pressure drop 84 in both the first period 72 and the second period 76. Specifically, the actual pressure profile 82 rises to the first target pressure value 74 in the first period 72 and then falls. The pressure drop 84 of the actual pressure profile 82 in the first period 72 occurs even though the pressure control valve 58 is controlled with a higher target pressure value 74. The pressure drop 84 can be expressed using an exponential function. A correspondingly identical profile is shown for the second period 76.

[0073] The control unit 38 is designed to analyze the actual pressure profile 82 and, based on this profile, to identify the pressure drop 84 in the first period 72 and in the second period 76. Due to the pressure drop 84, the control unit 38 detects an insufficient cross-section in the supply line 36 of the selected process gas 30, 32, 34 to the gas control unit 24 as a fault. In the illustrated embodiment, the supply line 36 has a kink that causes the pressure drop 84 shown in Fig. 3.

[0074] Fig. 4 shows a graph of the target pressure curve 66 and the actual pressure curve 82. The actual pressure curve 82 has an overshoot 86 in both the first period 72 and the second period 76. In detail, the actual pressure curve 82 rises in the first period 72 to a value greater than the first target pressure value 74 and then falls back to the value of the first target pressure value 74. For example, the actual pressure curve 82 can rise in the first period 72 to a value 1 bar greater than the first target pressure value 74. In other words, the overshoot 86 can have a value of 1 bar. The overshoot 86 of the actual pressure curve 82 in the first period 72 occurs even though the pressure control valve 58 is controlled with a lower target pressure value 74. A correspondingly similar pattern is shown for the second period, 76.

[0075] The control unit 38 is configured to analyze the actual pressure profile 82 and, based on this profile, to identify the overshoot 86 in the first period 72. The control unit 38 is configured to determine the magnitude of the overshoot 86. An overshoot limit of, for example, 0.5 bar is specified for the control unit 38. Therefore, the magnitude of the overshoot 86, which is 1 bar in the first period 72, is greater than the specified overshoot limit of 0.5 bar. The control unit 38 determines that the magnitude of the overshoot 86 is greater than the overshoot limit. The same applies to the second period 76.

[0076] The control unit 38 is designed to detect wear of the gas control unit 24 as a fault due to the overshoot limit being exceeded by the overshoot 86 in the first period 72 and / or due to the overshoot limit being exceeded by the overshoot 86 in the second period 76. In the illustrated embodiment, the selected process gas is compressed air 30 and the compressed air / nitrogen directional control valve 54 is worn, which is why the compressed air / nitrogen valve 54 is sticking and causing the overshoots 86.

[0077] Fig. 5 shows a graph of the target pressure curve 66 and the actual pressure curve 82. The actual pressure curve 82 exhibits a periodic oscillation 88 around the first target pressure value 74 during the first period 72 and a periodic oscillation 88 around the second target pressure value 78 during the second period 76. Specifically, the actual pressure curve 82 rises in the first period 72 to a value greater than the first target pressure value 74, then falls below the first target pressure value 74, before rising again above the first target pressure value 74. Thus, the actual pressure curve 82 oscillates around the first target pressure value 74 with the periodic oscillation 88. The periodic oscillation 88 has a decreasing amplitude. For example, the periodic oscillation 88 has a maximum amplitude of 1 bar. A correspondingly similar pattern is shown for the second period, 76.

[0078] The control unit 38 is configured to analyze the actual pressure profile 82 and, based on this profile, to identify the periodic oscillation 88 in the first period 72. The control unit 38 is configured to determine the amplitude of the periodic oscillation 88. An amplitude limit of, for example, 0.5 bar is specified for the control unit 38. Thus, the amplitude of the oscillation 88, with a value of 1 bar, is greater than the specified amplitude limit of 0.5 bar in both the first period 72 and the second period 76. The control unit 38 determines that the amplitude is greater than the amplitude limit. The same applies to the second period 76.

[0079] The control device 38 is designed to detect wear of the gas control unit 24 as a fault due to the exceedance of the amplitude limit value by the periodic oscillation 88 in the first period 72 and / or due to the exceedance of the amplitude limit value by the periodic oscillation 88 in the second period 76. In the illustrated embodiment, excessive regulation of the process gas pressure by means of the gas control unit 24 takes place, which is why the periodic oscillations occur.

[0080] Fig. 6 shows a graph of the target pressure curve 66 and the actual pressure curve 82. In the first period 72, the actual pressure curve 82 follows the target pressure curve 66. In the second period 76, the actual pressure curve 82 reaches a maximum actual pressure value 90, which is lower than the second target pressure value 78. For example, the maximum actual pressure value 90 is 1 bar lower than the second target pressure value 78.

[0081] The control unit 38 is configured to analyze the actual pressure profile 82 and calculate an average value of the actual pressure profile 82 for the second period 76. The control unit 38 is configured to determine a pressure difference 92 between the average value of the actual pressure profile 82 in the second period 76 and the second target pressure value 78. The control unit 38 is preset with a pressure limit value of, for example, 0.5 bar. Therefore, the pressure difference 92, with a value of 1 bar in the second period 76, is greater than the preset pressure limit value of 0.5 bar. The control unit 38 detects as an error that an inlet pressure at the inlet 60 of the pressure control valve 58 is insufficient.

[0082] Figures 3 to 6 each illustrate the occurrence of a single fault. In further alternative embodiments, the faults shown in Figures 3 to 6 can occur in combination. For example, an overshoot and periodic oscillations can occur simultaneously. The control unit 38 is designed to detect all faults occurring simultaneously. After detecting a fault, the control unit 38 outputs the detected fault. The fault output can be displayed on a screen (not shown) of the laser processing machine 10.

[0083] Additionally, the control unit 38 can output instructions for correcting the detected fault. These instructions can also be displayed on the screen.

Claims

Patent claims 1. Method for operating a laser processing machine (10) for processing a workpiece (12) by means of a laser beam (14), wherein during the processing of the workpiece (12) the laser beam (14) and a process gas (30, 32, 34) exit from a nozzle unit (16) and are directed onto the workpiece (12) by means of the nozzle unit (16), wherein the process gas (30, 32, 34) can be selected from a plurality of process gases (30, 32, 34) by means of a gas control unit (24) and the selected process gas (30, 32, 34) is fed to the nozzle unit (16) via a pressure control valve (58) of the gas control unit (24) for setting a target pressure, wherein the method comprises: Conducting a comprehensive test procedure: Selecting a process gas (30, 32, 34) from the majority of process gases (30, 32, 34) using the gas control unit (24), Setting a target pressure profile for the selected process gas (30, 32, 34) by means of the pressure control valve (58), wherein the target pressure profile has a first target pressure value (74) for a first period (72) and a second target pressure value (78) for a second period (76), Measuring an actual pressure profile (82) at an output (62) of the pressure control valve (58), Creating test data, wherein the test data contains information about the selected process gas (30, 32, 34), the target pressure profile (66) and the actual pressure profile (82), Analyzing the test data for the presence of an error.

2. The method according to claim 1, wherein the method is repeated at a predetermined time interval and / or manually initiated and / or initiated by a predetermined event.

3. Method according to one of the preceding claims, wherein the test procedure is carried out for each process gas (30, 32, 34).

4. A method according to any of the preceding claims, wherein the first target pressure value (74) and the second target pressure value (78) differ from each other, and / or wherein the target pressure curve (66) for a third period (80), which is located between the first period (72) and the second period (76), has a third target pressure value with an amount of 0 bar.

5. Method according to any of the preceding claims, wherein, if the selected process gas is oxygen (34), the target pressure curve (66) has a maximum target pressure value of 12 bar, or wherein, if the selected process gas is nitrogen (32), the target pressure curve (66) has a maximum target pressure value of 25 bar, or wherein, if the selected process gas is compressed air (30), the target pressure curve (66) has a maximum target pressure value of 5 bar.

6. Method according to one of the preceding claims, wherein the analysis of the test data comprises detecting an insufficient cross-section in the supply line (36) to the gas control unit (24) as a fault if the first target pressure value (74) is not equal to 0 bar and the actual pressure curve (82) drops in the first period (72), and / or if the second target pressure value (78) is not equal to 0 bar and the actual pressure curve (82) drops in the second period (76).

7. Method according to one of the preceding claims, wherein the analysis of the test data comprises detecting wear of the gas control unit (24) as a fault if the actual pressure profile (82) in the first period (72) exhibits an overshoot (86) above the first target pressure value (74) with an amount greater than a predetermined overshoot limit, and / or if the actual pressure profile (82) in the second period (76) exhibits an overshoot (86) above the second target pressure value (78) with an amount greater than the predetermined overshoot limit.

8. Method according to one of the preceding claims, wherein the analysis of the test data comprises detecting wear of the gas control unit (24) as a fault if the actual pressure profile (82) in the first period (72) exhibits a periodic oscillation (88) around the first target pressure value (74) with an amplitude greater than a predetermined amplitude limit, and / or if the actual pressure profile (82) in the second period (76) exhibits a periodic oscillation (88) around the second target pressure value (78) with an amplitude greater than the predetermined amplitude limit.

9. Method according to one of the preceding claims, wherein the analysis of the test data comprises detecting an insufficient inlet pressure at an inlet (60) of the pressure control valve (58) as a fault if a pressure difference (92) between an average value of the actual pressure profile (82) in the first period (72) and the first target pressure value (74) is greater than a pressure limit value and / or if a pressure difference (92) between an average value of the actual pressure profile (82) in the second period (76) and the second target pressure value (78) is greater than the pressure limit value.

10. Laser processing machine (10) for processing a workpiece (12) by means of a laser beam (14), wherein the laser processing machine (10) is configured to perform a method according to one of the preceding claims, wherein the laser processing machine (10) comprises: the nozzle unit (16) for directing the laser beam (14) and the process gas (30, 32, 34) onto the workpiece (12), the gas control unit (24) for selecting the process gas (30, 32, 34) from a plurality of process gases (30, 32, 34) with the pressure control valve for setting a target pressure of the selected process gas (30, 32, 34), and a control device (38), wherein the selected process gas (30, 32, 34) is guided to the nozzle unit (16) via the pressure control valve (58), wherein the The pressure control valve (58) has a pressure sensor (64) for measuring the actual pressure profile (82) at the output (62) of the pressure control valve (58),wherein the control device (38) is configured to generate the test data and to analyze the test data for the presence of the fault.

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