WO2024245684A1 - Method for monitoring a laser processing process, and laser processing system - Google Patents

Abstract

A method for monitoring a laser processing system is specified. The method comprises the steps of: acquiring, in a monitoring period, measured values of a measured variable of the laser processing process; comparing the measured values with value ranges of the measured variable of a plurality of process levels; determining whether the measured values lie in one of the value ranges of the process levels; and, if the measured values lie in one of the value ranges of the process levels, setting the process level, in the value range of which the measured values lie, for monitoring the process.

Description

Method for monitoring a laser processing process and laser processing system

The present disclosure relates to a method for monitoring a laser processing process. Furthermore, the present disclosure relates to a laser processing system and a computer program product which are configured to carry out the method.

background

In a laser processing system, also known as a laser processing system or system for short, a laser beam is directed at the workpiece to be processed. The processing can include laser welding, laser cutting, laser engraving or laser hardening.

To ensure the quality of the processing, the laser processing process can be monitored. For monitoring purposes, a sensor or sensor unit can record process emissions that arise during the laser processing process. The sensor data can be compared with specified limit values and/or envelopes. If the sensor data is outside the envelopes or exceeds or falls below a limit value, an error in the laser processing process is detected.

An error-free laser processing process can also occur if the sensor data lie outside the specified envelope curves or exceed or fall below the limit values. For example, the sensor data for a "cold" system, i.e. for a system with a short operating time, can differ considerably from sensor data for a "warm" system, i.e. for a system with a longer operating time. In both cases, however, the laser processing process can run error-free. Sensor data for error-free operation can also differ considerably for different laser processing processes, for different positions in a scanning field of a laser scanner system, for different component tolerances of the laser processing system and/or for different production or material batches. disclosure of the invention

It is an object of the present disclosure to provide a method and/or a laser processing system by which monitoring of a laser processing process, in particular online monitoring, is improved.

A further object of the present disclosure is to provide a method and/or a laser processing system by which error detection of the laser processing process is improved. In particular, an object of the present disclosure is to provide a method and/or a laser processing system by which false error detection is reduced.

Another object of the present disclosure is to provide a method and/or a laser processing system by which monitoring of the laser processing process is improved.

A further object of the present disclosure is to provide a method and/or a laser processing system by means of which reliable process monitoring is possible in an automated manner, regardless of the state of the system or individual components.

One or more of these objects are achieved by the subject matter of the independent claims. Advantageous embodiments and further developments are specified in the dependent claims.

The present disclosure is based on the idea that a stably set laser processing process can run at different process levels (process windows) for various reasons, e.g. due to a dependency on a scan field position in a laser scanner system, tolerance of a clamping device for fixing components, component tolerances, a temperature (cold/warm system). Accordingly, according to the present disclosure, a method and a laser processing system are provided for monitoring a laser processing process online that runs at different process levels. To ensure this, according to one aspect of the present disclosure, automatic (automatic or manually) learned or defined process levels (process windows) are recognized based on sensor data or measured values recorded in a laser processing process and (previously automatically or manually) determined parameters for process monitoring are automatically set to the recognized process level.

A method for monitoring a laser processing process is specified. The method comprises the steps of: recording, in a monitoring period, measured values of a measured variable of the laser processing process, comparing the measured values with value ranges of the measured variable of several process levels, determining whether the measured values are in one of the value ranges of the process levels, and if the measured values are in one of the value ranges of the process levels, setting the process level for process monitoring in whose value range the measured values are, and monitoring the laser processing process based on at least one parameter that is assigned to the set process level. The method can be carried out for each measured variable of the laser processing process that is to be used for process monitoring. The monitoring period can be while the laser processing process is being carried out.

In other words, according to the present disclosure, a method for monitoring a laser processing process based on at least one measured variable of the laser processing process comprises the following steps for each measured variable in a monitoring phase or in a monitoring period: capturing measured values of the measured variable of the laser processing process; comparing the measured values with (predetermined) value ranges of several (predetermined) process levels; determining whether the measured values are in one of the (predetermined) value ranges of the (predetermined) process levels; if the measured values are in one of the (predetermined) value ranges of the (predetermined) process levels, setting the process level for process monitoring in whose value range the measured values are; and monitoring the laser processing process based on at least one parameter that is associated with the set process level.

Furthermore, a laser processing system for carrying out a laser processing process is specified. The laser processing system comprises a laser processing head with at least one sensor unit, wherein the sensor unit is set up to measure values of a measured variable of the laser processing process in a monitoring period. The laser processing system comprises a control device. The control device is set up to: compare the measured values with value ranges of several process levels; determine whether the measured values are in one of the value ranges of the process levels, and if the measured values are in one of the value ranges of the process levels; set the process level for process monitoring in whose value range the measured values are; and monitor the laser processing process based on at least one parameter that is assigned to the set process level. The laser processing system can further comprise a scanning device for deflecting a processing laser beam to different positions in a scan field of the scanning device. The scanning device can, for example, comprise at least one, preferably two mirror elements that can be pivoted about at least one axis by means of a drive (e.g. a galvo drive).

The laser processing system, in particular the control device, can be configured to carry out any method step or method disclosed herein. In particular, the sensor unit and/or the control device is configured to carry out a method step disclosed herein.

Further provided is a computer program product comprising instructions that cause a laser processing system to perform a method disclosed herein.

The method may be any method disclosed herein. The laser processing system may be any laser processing system disclosed herein.

By comparing measured values, for example recorded by a sensor, with several value ranges of different process levels, different properties or configurations of the laser processing process or the laser processing system can be taken into account in process monitoring. For example, the measured values can be outside a first value range that was defined for a "warm" system (first process level), and the measured values can be within a second value range that was defined for a "cold" system (second process level). If the measured values were only compared with the value range of the first process level ("warm" system), it could be wrongly assumed that a malfunction of the process or system can be detected, even though the process is running stably or error-free on a "cold" system. This improves the operation or monitoring of the laser processing process. This also applies to components of the laser processing system from different batches, workpieces from different batches or properties (material, alloy, dimensions, etc.), for different users, component tolerances, etc.

In particular, in a laser processing system with a scanning device for deflecting the processing laser beam (i.e. a laser scanner system), the measured values of the measured variable under consideration can experience a (sudden) change from one process level to another process level by changing the scanning position in the scanning field of the scanning device. The scanning position can, for example, influence measured values of a radiation intensity of process emissions, e.g. of thermal radiation, due to a different angle and/or distance to the corresponding sensor unit. According to the present disclosure, an automatic adjustment of the process level is proposed in order to ensure automatic and continuous process monitoring.

The monitoring period can be any interrupted or uninterrupted period. In particular, the monitoring period can be an uninterrupted or continuous period. The monitoring period can be part of a longer or larger monitoring period. The monitoring period is preferably shorter than 1 min, more preferably shorter than 10 s, more preferably shorter than 1 s, more preferably shorter than 300 ms. The monitoring period can be a period of complete laser processing of one or more workpieces, for example a complete welding of two workpieces.

The measured values can be recorded by a sensor or a sensor unit. The measured values can be individual measured values (digital measuring signal) or continuous measured values (analog measuring signal). A large number of measured values can be recorded in the monitoring period. The measured values can represent a trend. A trend can be created based on the measured values. The trend can be compared with the value ranges of the process levels. The trend can be a time trend.

The measured variable of the laser processing process can be any measured variable, in particular a measured variable of the laser processing process. In particular, the measured variable can be a temperature, a pressure, an intensity of electromagnetic radiation and/or an intensity of an optical process emission. Measured values of several measured variables can be recorded. Different sensors can be provided for this purpose.

For each process level, there is at least one value range or exactly one value range. This means that each process level can be assigned exactly one value range. The number of value ranges and process levels can be the same. Each of the value ranges contains values of the measured variable. Each process level can be assigned to a different value range or each process level can be assigned a different value range. Several process levels can be defined or present for each measured variable. This means that for each measured variable, the measured values recorded for this measured variable can be compared with value ranges of several, i.e. different, process levels.

In general, different process levels may differ in at least one property or in at least one configuration of the laser processing process or the laser processing system.

None of the value ranges can completely overlap with another of the value ranges. One value range can partially overlap another value range. Preferably, the value ranges are completely spaced apart from one another, i.e. the value ranges can be completely non-overlapping or not overlapping. The value ranges can be spaced apart from one another at least at one point in time or in one time period in the laser processing process, i.e. the value ranges can be non-overlapping or not overlapping at least at one point in time or in one time period in the laser processing process. In this case, each measured value of the measured variable can be clearly assigned to a value range or a process level. The value ranges and/or the parameters for process monitoring can be stored or saved in a memory of the laser processing system.

The measured values can be compared with at least 2, preferably at least 5, more preferably at least 10, more preferably at least 50, different value ranges. The measured values can be compared with at most 100, preferably at most 50, more preferably at most 10, different value ranges. In particular, the number of value ranges with which the measured values are compared is between 2 and 100. In general, the number of value ranges with which the measured values are compared can be selected such that a clear assignment of the measured values to (exactly) one value range is possible.

The comparison of the measured values with the value ranges can be carried out in real time. In particular, the comparison of the measured values with the value ranges is carried out in less than 1 s, preferably less than 500 ms, more preferably less than 200 ms.

When determining whether the measured values lie within one of the value ranges of the process levels, it can be determined whether the measured values, in particular within the monitoring period, lie predominantly or completely within one of the value ranges of the process levels.

If the measured values are in one of the value ranges of the process levels, the laser processing process can be monitored at this process level. This means that a process level can be selected or identified based on the measured values in the monitoring period. The laser processing process can then be monitored based on the at least one process monitoring parameter of the selected or identified process level.

The method can include: if the measured values are not in any of the value ranges of the (known or specified) process levels, recognizing that an unknown process level is present. For example, the presence of an unknown process level can occur if measured values from several laser processing processes are in a new value range (i.e. not yet assigned to a process level) and/or are similar. In this case, the unknown process level can be learned by setting the measured value a range of values for the unknown process level is determined and at least one parameter for monitoring the laser processing process is determined and assigned to the (previously) unknown process level.

Alternatively or additionally, the method may include: if the measured values are not within any of the value ranges of the process levels, detecting that there is or was a fault in the laser processing process or that the laser processing process is or was faulty.

As a result of the determination, it can be determined that the measured values are (completely) not within any of the value ranges. In other words, it can be determined that the measured values are (completely) outside of all value ranges. In this case, an error can be detected.

As a result of the determination, it can also be determined that the measured values lie (completely) in (exactly) one of the value ranges of the process levels. In this case, the laser processing process can be monitored based on the detected process level. In particular, the monitoring is carried out based on a parameter that is assigned to the process level.

Also, as a result of the determination, it can be determined that the measured values (within the monitoring period) are only partially or exactly partially or at most partially or at least partially within a range of values. In other words, it can be determined that part of the measured values are within a range of values and another part of the measured values are outside the range of values. If a limit value for a number of measured values within a range of values or a limit value for a period of measured values within the range of values is exceeded, it can be recognized that an error is present. If a limit value for a number of measured values outside a range of values or a limit value for a period of measured values outside the range of values is exceeded, it can be recognized that an error is present. If a limit value for a number of measured values outside a range of values or a limit value for a period of measured values outside the range of values is exceeded, the process level can be recognized or identified. If a limit value for a number of measured values within a range of values or a If the limit is exceeded for a period of measured values within the value range, the process level can be detected or identified.

It can be provided that a process level is detected if at least 90% of the measured values in the monitoring period are in the value range of the process level. Alternatively or additionally, it can be provided that faulty operation or an error is detected if at least 10% of the measured values in the monitoring period are not in any of the value ranges.

Based on the detected process level, the process can be monitored. Each of the process levels can be assigned one or more parameters. The parameter can also be referred to as a monitoring parameter. The parameter can include a statistical value, a mathematical function, etc. The parameter can be assigned a value or a range of values. The value or range of values can specify a maximum permissible deviation.

For example, at least one reference curve for the set process level can be specified for the measured values of the measured variable. In particular, an upper and a lower reference curve can be specified, and/or a mean value reference curve. The parameter can be or include a (maximum) amplitude with which the measured values exceed or fall below this reference curve. If a specified value (e.g. limit value) for the parameter, i.e. for the (maximum) amplitude, is exceeded, an error can be detected. Alternatively or additionally, the parameter can be or include a (maximum) area that includes measured values above or below this reference curve with the reference curve. If a specified value (e.g. limit value) for the parameter, i.e. for the (maximum) area is exceeded, an error can be detected. Alternatively or additionally, the parameter can be or include an area below the measured values or an integral of the measured values during a laser processing process. If a specified value (eg limit) for the parameter, ie for the area or the integral, is exceeded or not reached, an error or no error can be determined. The area or the integral can be understood as the integral of the temporal course of the measured values or the measurement signal. Alternatively or additionally, the parameter can be or include an outlier frequency, ie a Frequency or number of measured values that are above or below the reference curve. If a specified value (e.g. limit value) for the parameter, ie for the outlier frequency, is exceeded, an error can be detected. The outlier frequency can be understood as the number or period of measured values above the upper reference curve and below the lower reference curve. The outlier frequency can be an absolute or relative value. Alternatively or additionally, the parameter can be or include a quadratic deviation from a specified reference curve (e.g. a mean reference curve). If a specified value (e.g. limit value) for the parameter, ie for the quadratic deviation, is exceeded, an error can be detected. To determine the quadratic deviation, a deviation of a measured value or measurement signal from the reference curve can be squared.

If an error is detected, an error message can be output, in particular to a user. The error message can be a visual or acoustic signal. In particular, the error message can be a graphical representation on a display of the laser processing system. Based on the error message, the user can change the laser processing process. Alternatively or additionally, the laser processing process can be changed if an error is detected. For example, the laser processing process can be interrupted or switched off. Likewise, the laser processing process can be controlled or regulated, in particular based on the result of the comparison of the measured values with the value ranges.

Each of the value ranges can be defined by specified limit values. In particular, each of the value ranges can be defined by two curves.

At least one limit value can be specified for each of the value ranges. In particular, at least two limit values can be specified for each of the value ranges. A first limit value can be an upper limit value and the second limit value can be a lower limit value. The value range can be specified between the first limit value and the second limit value. Each of the limit values can be specified or can be specified by a user or operator of the laser processing system or by a manufacturer of the laser processing system. Each The limit values can be set or determined automatically by the laser processing system.

Each of the limit values can be a progression or a curve. Preferably, each of the limit values is an envelope curve (also referred to as a "reference curve" or "reference" for short). An upper envelope curve and a lower envelope curve can be defined for each value range. The value range can be defined between the upper envelope curve and the lower envelope curve. The value range can have a mean value, for example a mean value curve.

The method can comprise for each measured variable (e.g. in a recording phase): recording, e.g. in a recording period or in a recording phase, measured values of the measured variable; determining a value range for at least one process level or for each of the process levels based on the measured values in the recording period. This allows new or as yet unknown process levels to be defined. The method can further comprise: determining at least one parameter for monitoring the laser processing process and assigning it to the corresponding process level.

The recording period can be referred to as a recording phase or can be included in a recording phase. The recording period of the laser processing process can be any interrupted or uninterrupted period. In particular, the recording period is an uninterrupted or continuous period. The recording period can be part of a longer or larger recording period. The recording period is preferably longer than 1 hour, preferably longer than 4 hours, more preferably longer than 12 hours, more preferably at least 24 hours. The recording period can be longer than the monitoring period.

A laser processing process can be carried out in the detection period. Preferably, the same laser processing process is carried out in the detection period as in the monitoring period. The laser processing process in the monitoring period can be a part or section of the laser processing process in the detection period.

In the recording period, measured values of the same measurand can be recorded as in the monitoring period. In particular, the same sensor or the same sensor unit is used for Collection of measured values in the collection period as used in the monitoring period.

In the recording period, measured values of the measured variable can be recorded for more than one process level, in particular for a large number of process levels. Based on the measured values in the recording period, several value ranges for different process levels can be determined. One value range can be assigned to one process level or linked to it.

The recording period and the monitoring period can be spaced apart (in time). The recording period and the monitoring period cannot occur at the same time. The recording period and the monitoring period cannot overlap (in time). The recording period and the monitoring period can be adjacent to each other. The recording period can be before the monitoring period.

A parameter for monitoring the laser processing process can be assigned to each of the process levels. The assignment can be manual or automated. The parameter can be the same for all process levels. In this case, however, a value or value range assigned to the parameter can be different. Likewise, the parameters of at least two process levels can be different. The parameters of all process levels can be different.

The recording of measured values in the recording period can be carried out several times for different process levels. Alternatively or additionally, the determination of value ranges can be carried out several times for different process levels. Alternatively or additionally, the assignment of at least one parameter for monitoring the laser processing process to one or each of the process levels can be carried out several times for different process levels.

For example, measured values for a first process level can be recorded in the recording period and measured values for a second process level can be recorded in the recording period. In general, measured values can be recorded for a variety of process levels A value range can be determined for measured values of each process level, so that respective value ranges for several process levels can be determined using measured values in a (continuous) recording period. A parameter can be assigned to each process level. The laser processing process can be monitored based on the parameter.

The recording of measured values in the recording period can be carried out before the laser processing system is put into operation. Alternatively or additionally, the determination of value ranges can be carried out before the laser processing system is put into operation. Alternatively or additionally, the assignment of at least one parameter for monitoring the laser processing process to one or each of the process levels can be carried out before the laser processing system is put into operation.

A predetermined laser processing program can be carried out in the recording period. Laser processing processes with different process levels can be carried out in the laser processing program. The laser processing program can comprise at least two different process levels, preferably at least five different process levels. The laser processing program can be or be determined by a manufacturer of the laser processing system or by a user of the laser processing system.

A further recording of measured values in a recording period can be carried out after the recording of measured values in a monitoring period, e.g. if an unknown process level is present. Alternatively or additionally, a further determination of value ranges can be carried out after the recording of measured values in a monitoring period. Alternatively or additionally, the assignment of at least one parameter for monitoring the laser processing process to one or each of the process levels can be carried out after the recording of measured values in a monitoring period. A further determination of value ranges can also be carried out after a first determination of value ranges, wherein preferably at least one monitoring period between the further determination of value ranges and the first determination of value ranges In other words, after a monitoring phase, you can switch back to an adjustment phase.

The further recording and/or the further determination of value ranges and/or the further assignment of parameters can be carried out after a change in the laser processing system and/or after a change in the laser processing process.

The number of value ranges of the process levels, in particular in a memory of the laser processing system, can change or remain the same through the further determination of value ranges. In other words, through the further determination of value ranges, value ranges can be determined that supplement value ranges already determined or value ranges already determined can be replaced by further determined value ranges.

In general, the number of value ranges considered, i.e. the number of value ranges with which measured values are compared, can be variable. The number can be increased or reduced. The change in the number of value ranges considered can be automated, in particular based on an error detection rate.

The change in the laser processing process can include a change in a component of the laser processing system. For example, a component (e.g. a lens or protective glass) of the laser processing system can be replaced. This can change the laser processing process slightly, so that updating or adding value ranges for process levels is useful. The change in the laser processing process can also be due to aging or wear of a component of the laser processing system. The change in the laser processing process can be caused by a batch change of a component.

The further recording and/or further determination of value ranges and/or the assignment of parameters can be initiated by a user or can be carried out automatically, for example automatically after a component of the laser processing system has been changed. The value ranges and/or the parameters of the process levels can be determined using one or more statistical methods. For example, a box plot analysis or a frequency distribution can be carried out for this purpose. Other statistical methods known per se are possible. The value ranges can be determined based on the recorded measured values for the measured variable in the recording period using one or more statistical methods.

For example, a mean curve can be determined based on measured values in the recording period. For the mean curve, curves can be determined as limit values. The curves can be envelope curves. The envelope curves can comprise an upper envelope curve and a lower envelope curve, with the mean curve lying between the upper envelope curve and the lower envelope curve. The mean curve and/or the envelope curves can be determined using a statistical method, e.g. a box plot analysis. The mean curve can comprise mean values and/or median values of the measured values recorded for the measured variable during the recording period. In the recording period, the respective limit value can be set based on the mean curve determined for the measured variable and/or on the envelope curves determined for the measured variable. The upper envelope curve can in particular be set such that it has a predetermined first distance from the mean curve, and the lower envelope curve can be set such that it has a predetermined second distance from the mean curve. The first distance and the second distance can be equal or different in terms of amount. The envelope curves can be used to define a respective value range of a process level.

Before comparing the measured values with the value ranges of the process levels, a selection of the process levels can be made. The measured values can be compared with the value ranges of the selected process levels.

The selection may be based on at least one of the following information: information about the laser processing system, information about the laser processing process, information about the temperature of the laser processing system, information about the operating time of the laser processing system, information about the pressure in and/or outside the laser processing system, information about a user of the Laser processing system, information about aging and/or wear of at least one component of the laser processing system, a component tolerance of one or more components of the laser processing system, a batch of workpieces to be processed in the laser processing process and/or a scan field position.

The selection can be made based on user input. Alternatively or additionally, the selection can be made automatically based on information from the laser processing system and/or the laser processing process. For example, the laser processing system can know the current operating time and this information can be used for the selection. The selection can reduce the number of process levels or value ranges with which measured values from the monitoring period are compared.

Preferably, the comparison of measured values from the monitoring period is only carried out with those value ranges that have been selected or that are available through the selection. Non-selected value ranges are preferably not used for the comparison of measured values from the monitoring period with value ranges.

In general, a process level can be based on at least one of the following information: information about the laser processing system, information about the laser processing process, information about the temperature of the laser processing system, information about the operating time of the laser processing system, information about the pressure in and/or outside the laser processing system, information about a user of the laser processing system, information about aging and/or wear of at least one component of the laser processing system, a component tolerance of one or more components of the laser processing system, a batch of workpieces to be processed in the laser processing process and/or a scan field position.

Different process levels may differ in at least one characteristic or configuration of the laser processing system and/or laser processing process.

The measured variable can be at least one of the following: a temperature, a thermal radiation and an intensity of at least one process emission, in particular an optical Process emission. The process emission can include laser light reflected from a workpiece, plasma radiation generated by the laser processing process, light in the visible spectral range generated by the laser processing process, and/or light in the infrared spectral range generated by the laser processing process.

The measured variable can be detected by a sensor unit or a sensor. The sensor or the sensor unit can comprise at least one, in particular several photodiodes that are sensitive to different wavelength ranges. Alternatively or additionally, the sensor or the sensor unit can comprise at least one two-zone photodiode that is designed to detect two different wavelength ranges separately.

The sensor or the sensor unit can have a first photodiode that is set up to detect process radiation in at least a first predetermined wavelength range, in particular in the visible wavelength range. The sensor unit can also have a second photodiode that is set up to detect process radiation in at least a second predetermined wavelength range, in particular in the ultraviolet wavelength range. The sensor unit can preferably have a third photodiode that is set up to detect process radiation in at least a third predetermined wavelength range, in particular in the infrared wavelength range. The first, second and third wavelength ranges preferably do not intersect or overlap, or at least not completely.

The different photodiodes can be set up to detect different types or wavelength ranges of process radiation, such as thermal radiation, a back reflection of the processing laser beam, scattered light or plasma radiation. Thermal radiation or temperature radiation can be in the wavelength range of infrared and/or near-infrared radiation, whereas plasma radiation can be in the visible wavelength range. The use of several photodiodes, i.e. at least two photodiodes that can detect process radiation in different wavelength ranges, has the advantage that different parts of the process radiation can be detected and evaluated separately. For example, a processing error can be reflected primarily in the temperature radiation, while another processing error can be reflected in the best detected in the plasma radiation signal. This allows the laser processing process to be monitored across a wide range of the spectrum and for various processing errors or artifacts, and therefore leads to particularly comprehensive and reliable monitoring of laser processing processes.

For each measured variable or for each sensor or for each of the photodiodes, there can be a separate value range per process level.

The laser processing process may be or include a laser welding process, a laser cladding process, a laser cutting process, a laser engraving process, or a laser hardening process.

Short description of the drawings

The invention is described in detail below with reference to figures.

Figs. 1a and 1b each show a laser processing system 400;

Fig. 2 shows measured values for different process levels 601, 602, 603, 604;

Fig. 3 shows measured values 501, 502, 503 for different process levels 601, 602, 603;

Fig. 4 shows value ranges 701, 702, 703 for different process levels 601, 602, 603; and

Figs. 5 and 6 show measured values 801, 802, 803 in different monitoring periods tU.

Detailed description of the drawings

The laser processing system 400 shown in Figs. 1a and 1b includes a laser processing head 100 and a controller 300. The laser processing system 500 may include a laser source 200.

The laser source 200 can generate a processing laser beam L (laser beam). The laser source 200 can be designed as a single-mode laser, as a solid-state laser or as a fiber laser. The processing laser beam L generated by the laser source 200 can be transmitted from the laser source 200 to the laser processing head 100 via an optical fiber. The processing laser beam L can be coupled into the laser processing head 100 via a fiber coupler 140. The fiber coupler 140 can be arranged on a housing 110 of the laser processing head 100.

The laser processing head 100 can comprise a collimation optics 121 (collimating optics). The collimation optics 121 can be arranged and designed in the laser processing head 100 such that the processing laser beam L entering the laser processing head 100 divergently is collimated. The collimation optics 121 can be arranged in the housing 110 of the laser processing head 100.

The collimation optics 121 can comprise at least one lens or two or more lenses. A distance between the two or more lenses can be adjustable, in particular by an electric motor. The collimation optics 121 can define an optical axis.

The laser processing head 100 can comprise at least one aperture 125. The aperture 125 can be arranged between the fiber coupler 140 and the collimation optics 121. The aperture 125 can shape the processing laser beam L so that it hits the collimation optics 121 with a defined diameter.

Furthermore, the laser processing head 100 can comprise a focusing optics 122. The focusing optics 122 can be arranged and designed in the laser processing head 100 such that the collimated processing laser beam L is focused. The focusing optics 122 can be arranged in the housing 110 of the laser processing head 100.

The focusing optics 122 can comprise at least one lens or two or more lenses. A distance between the two or more lenses can be adjustable, in particular by an electric motor. An optical axis can be defined by the focusing optics 122. The focusing optics 131 can be an F-Theta lens. The F-Theta lens can be arranged telecentrically. The focused processing laser beam L can be emitted from the laser processing head 100 and irradiated onto a workpiece W to process the workpiece W. Preferably, the housing 110 includes a nozzle 171 from which the processing laser beam L is emitted.

For example, the workpiece W can be welded. Two workpieces W can be welded together or a component can be welded to the workpiece W. The workpiece W can also be cut, engraved or hardened.

The laser processing head 100 may be a laser beam welding head, a laser beam cutting head, a laser beam engraving head, a laser beam hardening head, or a laser cladding head.

The laser processing head 100 can comprise at least one protective glass 123. The protective glass 123 can be arranged at one end of the housing 110. In particular, the protective glass 123 is replaceable. The protective glass 123 can protect an interior of the laser processing head 100 against contamination, particles, smoke, smoke, splashes, etc. The processing laser beam L can exit the laser processing head 100 through the protective glass 123 in order to be irradiated onto the workpiece W in particular.

Furthermore, the laser processing head 100 can comprise a lens, a transmissive element, a reflective element, a beam shaping element, a beam splitter and/or an optical wedge.

By means of optical elements of the laser processing head 100, an optical path for the processing laser beam L through the laser processing head 100 can be defined.

The laser processing head 100 can comprise a sensor unit 130 (also referred to as “sensor” for short). The sensor unit 130 can be configured to record measured values of a measured variable, in particular a measured variable of the laser processing process and/or the laser processing system 400. The sensor unit 130 can be arranged at least partially, in particular completely, within the housing 110 of the laser processing head 100. Such a configuration is shown in Fig. 1a. The sensor unit 130 can comprise a temperature sensor and be configured to detect a temperature, in particular a temperature of a component of the laser processing system and/or a temperature of the laser processing process. Alternatively, the sensor unit 130 can comprise a radiation sensor or a photodiode for detecting scattered radiation and/or process emissions.

The sensor unit 130 can be arranged at least partially, in particular completely, outside the housing 110 of the laser processing head 100. Such a sensor unit 130 is shown in Fig. 1b. In particular, the sensor unit 130 is set up to detect a process emission E that arises during the laser processing process. The process emission E is, for example, plasma radiation, light generated by the laser processing process in the visible spectral range and/or light generated by the laser processing process in the infrared spectral range. The process emission E can radiate into the laser processing head 100 and be coupled out of the laser processing head 100 by an optical element, for example by a semi-transparent mirror E, and coupled into the sensor unit 130. The sensor unit 130 can be an optical sensor unit 130.

The control device 300 can control the operation of the laser processing head 100. In particular, the control device 300 can control the laser power and/or the position and/or attitude of at least one optical element.

To monitor the laser processing process, i.e. during a monitoring phase, the control device 300 can be set up to record measured values 801, 802, 803 and to automatically examine them in real time for predetermined or previously learned process levels. For this purpose, the measured values 801, 802, 803 can be compared with (predetermined) value ranges of these process levels. If the measured values 801, 802, 803 are not in any value range of one of the known process levels, the process can be marked as faulty. If a process level is detected, i.e. if the measured values 801, 802, 803 are in a value range of one of the known process levels, this process level is set for process monitoring and the laser processing process is based on one or more of this process level. assigned parameters. For process monitoring, the measured values 801, 802, 803 can be compared with the parameters for the set process level and a process evaluation can be carried out. Manual intervention and manual switching to the associated parameters is therefore not necessary.

In particular, the control device 300 is configured to compare measured values 801, 802, 803 during a monitoring phase or during a monitoring period tU with value ranges 701, 702, 703 of different process levels 601, 602, 603, 604. The control device 300 is further configured to determine whether the measured values 801, 802, 803 are in one of the value ranges 701, 702, 703 of the process levels 601, 602, 603, 604. The control device 300 is further configured, if the measured values 801, 802, 803 are in one of the value ranges 701, 702, 703 of the process levels 601, 602, 603, 604, to set the process level 601, 602, 603, 604 for process monitoring, in whose value range 701, 702, 703 the measured values 801, 802, 803 are. In this way, the process monitoring can also be carried out for laser processing processes with changing process levels.

Fig. 2 shows real measured values of process emissions with different process levels 601, 602, 603, 604, which were recorded by an optical sensor, e.g. a photodiode. The intensity of the measurement signal is plotted against time. Four process levels 601, 602, 603, 604 are shown as examples for this measured variable, but fewer or more process levels can be considered. The courses of the measured values from several stable, i.e. error-free, laser processing processes were superimposed on one another in order to illustrate the process levels 601, 602, 603, 604. The measured values are in different value ranges and correspond to different process levels 601, 602, 603, 604. As can be seen in Fig. 2, the courses of the measured values differ considerably. The process levels can be automatically detected in an initial phase and the associated parameters for process monitoring can be statistically calculated or determined for each process level.

In the learning phase, the process levels and at least one parameter for process monitoring can be determined for each process level. Process monitoring can be deactivated. As shown in Fig. 3, measured values are recorded during a (non-monitored or exemplary) machining process, a process evaluation or - There is no external monitoring. Ideally, all commonly occurring process levels are represented in the measured values. The recorded or captured measured values can then be examined for different process levels (process windows) and one or more parameters for process monitoring can be automatically calculated for each process level using statistical methods. The process monitoring can then be activated by the operator.

Fig. 3 schematically shows three curves of measured values 501, 502, 503, where the intensity of the measurement signal is again plotted against time. The curves of measured values 501, 502, 503 can be mean value curves or median value curves or raw data. In particular, the curves of measured values 501, 502, 503 are determined by a statistical method.

The measured values 501, 502, 503 were recorded in a recording period tE. Each of the courses of the measured values 501, 502, 503 corresponds to an error-free or stable operation of a laser processing process at different process levels 601, 602, 603.

As shown in Fig. 4, an upper envelope 511, 521, 531 and a lower envelope 512, 522, 532 can be formed for each of the courses of measured values 501, 502, 503. A distance between the courses of the measured values 501, 502, 503 and the associated upper envelopes 511, 521, 531 and lower envelopes 512, 522, 532 can be an absolute or relative value. The distance can be a fixed value or selected by a user. The distance between a course of the measured values 501, 502, 503 and an upper envelope 511, 521, 531 and the distance between a course of the measured values 501, 502, 503 and a lower envelope 512, 522, 532 can be the same or different. The distance between a course of the measured values 501, 502, 503 and an upper envelope 511, 521, 531 and/or a lower envelope 521, 522, 532 can be constant or varying along the respective course.

A value range 701, 702, 703 can be formed by an upper envelope 511, 521, 531 and a lower envelope 512, 522, 532. One of the value ranges 701, 702, 703 can be assigned to a process level 601, 602, 603 or linked to it. Each of the process levels 601, 602, 603 is assigned at least one parameter for process monitoring. The parameter can be used to monitor the laser processing process. The parameters of the process levels 601, 602, 603 can be (all) the same or (all) different. Likewise, the parameters of the process levels 601, 602, 603 can be at most partially or at least partially different. Different types of parameters or different parameter values can be used.

In Figs. 5 and 6, in addition to the value ranges 701, 702, 703 of the process levels 601, 602, 603, measured values 801, 802, 803 are shown in a respective monitoring period tU.

In the monitoring period tU, measured values 801, 802, 803 of a measured variable of a laser processing process are recorded. The measured variable is preferably the same measured variable for which the measured values 501, 502, 503 were recorded in the recording period tE.

Preferably, the measured values 501, 502, 503 of the measured variable are recorded in the recording period tE before measured values 801, 802, 803 of the measured variable are recorded in the monitoring period tU. Further measured values 501, 502, 503 in a recording period tE can be recorded after measured values 801, 802, 803 have been recorded in at least one monitoring period tU. In other words, firstly the value ranges 701, 702, 703 of the process levels 601, 602, 603 can be defined in an incorporation phase, for example as part of a test or calibration laser processing process, but also as part of a real laser processing process. Further value ranges of process levels can be added or existing process levels can be removed. In particular, ranges of process levels are added or removed after the laser processing process has been changed, e.g. by changing a setting of the laser processing process, or after the laser processing system has been changed, e.g. by replacing a component or part of the laser processing system.

The measured values 801, 802, 803 in the monitoring period tU are compared with the value ranges 701, 702, 703 of the process levels 601, 602, 603 and it is determined whether the measured values 801, 802, 803 are in one of the value ranges 701, 702, 703. If the measured values 801, 802, 803 are in one of the process levels, the (detected) process level 601, 602, 603 used for process monitoring, in whose value range 701, 702, 703 the measured values 801, 802, 803 lie.

The measured values 801, 802, 803 can be compared with all value ranges 701, 702, 703 or only or at most with a part of the value ranges 701, 702, 703. A selection of the value ranges 701, 702, 703 with which the measured values 801, 802, 803 are compared can be made by a user or can be made based on information about the laser processing process and/or information about the laser processing system. For example, the operating time of the laser processing process can be known. Based on the operating time, a selection of value ranges 701, 702, 703 with which the measured values 801, 802, 803 are compared can be made.

Preferably, the measured values 801, 802, 803 are compared with at least two value ranges 701, 702, 703.

In the example of Fig. 5, the measured values 801 in the monitoring period tU lie entirely within the value range 701 of the process level 601. Based on this, the process level 601 can be recognized as the currently applicable process level. The laser processing process can be monitored based on the parameter assigned to the recognized process level 601.

In the first example of Fig. 6, measured values 802 in a monitoring period tU lie completely outside all value ranges 701, 702, 703 of the considered process levels 601, 602, 603. This makes it possible to recognize that an error is present or that the laser processing process is faulty.

In the second example of Fig. 6, measured values 803 in a monitoring period tU are only partially in the value range 703 of a process level 603. In this case, it can be determined over which period tA measured values are outside the value range. If the period is above a limit value, it can be recognized that an error is present. If the period is below the limit value, the process level 603 can be recognized as the currently applicable process level. Based on the at least one parameter for Process monitoring of this process level 603 can be used to monitor the laser processing process. Alternatively, it can be determined over which period the measured values are within the value range. If the period is above a limit value, the process level 603 can be recognized as the currently applicable process level. If the period is below the limit value, it can be recognized that an error has occurred.

Alternatively or additionally, it can be determined by what amount the measured values are outside the value range. If a limit value for the amount is exceeded, it can be recognized that an error is present. If the limit value for the amount is undershot, the process level 603 can be recognized as the currently applicable process level. After recognizing a process level, any method disclosed herein for monitoring the laser processing process can be used.

In general, a limit or each of the limits can be an absolute or relative value. The limit or each of the limits can be specified by a user or can be fixed.

According to the present disclosure, during process monitoring, the measured values recorded or detected by a sensor can be automatically examined in real time for previously learned process levels. If the measured values are not in a known process level, the process can be marked as faulty. If a process level is detected, the measured values can be compared with the previously determined parameters for this process level and a process evaluation can be carried out (process monitoring).

Claims

patent claims 1. A method for monitoring a laser processing process based on at least one measured variable of the laser processing process, the method comprising the following steps for each measured variable: Recording, in a monitoring period (tU), measured values (801, 802, 803) of the measured variable of the laser processing process; Comparing the measured values (801, 802, 803) with value ranges (701, 702, 703) of several process levels (601, 602, 603, 604); Determining whether the measured values (801, 802, 803) are in one of the value ranges (701, 702, 703) of the process levels (601, 602, 603, 604); if the measured values (801, 802, 803) are in one of the value ranges (701, 702, 703) of the process levels (601, 602, 603, 604), setting the process level (601, 602, 603, 604) for process monitoring in whose value range (701, 702, 703) the measured values (801, 802, 803) are; and Monitoring the laser processing process based on at least one parameter associated with the set process level (601, 602, 603, 604). 2. The method according to claim 1, wherein the method further comprises for each measured variable, if the measured values (801, 802, 803) are not in any of the value ranges (701, 702, 703) of the process levels (601, 602, 603, 604): Detecting that an unknown process level (601, 602, 603, 604) exists; or Detect that there is an error in the laser processing process. 3. Method according to one of the preceding claims, wherein each of the value ranges (701, 702, 703) is defined by fixed limit values and/or by two curves (511, 512; 521, 522; 531, 532). 4. Method according to one of the preceding claims, wherein the method further comprises for each measured variable: Recording, in a recording period (tE), measured values (501, 502, 503) of the measured quantity; Determining a value range (701, 702, 703) for at least one process level (601, 602, 603, 604) based on the measured values (501, 502, 503) in the recording period (tE); and Determining at least one parameter for monitoring the laser processing process for the process level (601, 602, 603, 604). 5. The method according to claim 4, wherein the acquisition of measured values (501, 502, 503) in the acquisition period (tE), the determination of a value range (701, 702, 703) and the determination of at least one parameter are carried out for several process levels (601, 602, 603, 604). 6. The method according to claim 4 or 5, wherein the acquisition of measured values (501, 502, 503) in the acquisition period (tE), the determination of value ranges (701, 702, 703) and the determination of at least one parameter is carried out before commissioning of the laser processing system (400) and/or in a learning phase. 7. Method according to one of claims 4 to 6, wherein a further recording of measured values (501, 502, 503) in a recording period (tE), a further determination of value ranges (701, 702, 703) and a further determination of at least one parameter is carried out after the recording of measured values in a monitoring period (tU), in particular after a change in the laser processing system (400) and/or a change in the laser processing process. 8. Method according to one of claims 4 to 7, wherein the determination of the value ranges (701, 702, 703) and/or the parameter for monitoring the laser processing process is carried out by one or more statistical methods. 9. Method according to one of the preceding claims, wherein before comparing the measured values (801, 802, 803) with the value ranges (701, 702, 703) of the process levels (601, 602, 603, 604), a selection of process levels (601, 602, 603, 604) is made and the measured values (801, 802, 803) are compared with the value ranges (701, 702, 703) of the selected process levels (601, 602, 603, 604), in particular wherein the selection is based on at least one of the following information: information about the laser processing system, information about the laser processing process, information about the temperature of the laser processing system, information about the operating time of the laser processing system, information about the pressure in and/or outside the laser processing system, information about a user of the laser processing system, information about an aging of at least one component of the laser processing system, information about a component tolerance of one or more components of the laser processing system, Information about a tolerance of a clamping device, information about a batch of workpieces to be processed in the laser processing process and/or a scan field position. 10. Method according to one of the preceding claims, wherein a process level (601, 602, 603, 604) is based on at least one of the following information: information about the laser processing system, information about the laser processing process, information about the temperature of the laser processing system, information about the operating time of the laser processing system, information about the pressure in and/or outside the laser processing system, information about a user of the laser processing system, information about an aging of at least one component of the laser processing system, information about a component tolerance of one or more components of the laser processing system, information about a tolerance of a clamping device, information about a batch of workpieces to be processed in the laser processing process and/or information about a scan field position. 11. Method according to one of the preceding claims, wherein the at least one measured variable is at least one of the following: a temperature, a temperature radiation and an intensity of at least one process emission, in particular an optical process emission, wherein the process emission in particular comprises laser light reflected from a workpiece (W), plasma radiation generated by the laser processing process, light generated by the laser processing process in the visible spectral range and/or light generated by the laser processing process in the infrared spectral range. 12. The method according to any one of the preceding claims, wherein the laser processing process is or comprises a laser welding process, a laser cladding process, a laser cutting process, a laser engraving process or a laser hardening process. 13. Laser processing system (400) for carrying out a laser processing process, the laser processing system (400) comprising: a laser processing head (100) with at least one sensor unit (130), wherein the sensor unit (130) is configured to record measured values (801, 802, 803) of a measured variable of the laser processing process in a monitoring period (tU); and a control device (300) which is set up to compare the measured values (801, 802, 803) with value ranges (701, 702, 703) of several process levels (601, 602, 603, 604) and to determine whether the measured values (801, 802, 803) are in one of the value ranges (701, 702, 703) of the process levels (601, 602, 603, 604), and if the measured values (801, 802, 803) are in one of the value ranges (701, 702, 703) of the process levels (601, 602, 603, 604), to set the process level (601, 602, 603, 604) for process monitoring, in whose value range (701, 702, 703) the measured values (801, 802, 803) lie, and to monitor the laser processing process based on at least one parameter associated with the set process level (601, 602, 603, 604). 14. The laser processing system (400) of claim 13, wherein the sensor (130) comprises at least one of the following: a first photodiode configured to detect electromagnetic radiation in the visible wavelength range, a second photodiode configured to detect electromagnetic radiation in the ultraviolet wavelength range, and a third photodiode configured to detect electromagnetic radiation in the infrared wavelength range. 15. A computer program product comprising instructions that cause a laser processing system to carry out the method according to any one of claims 1 to 12.