DE102022126951A1 - Method and device for controlling heat input into a component - Google Patents

Abstract

The invention relates to a method for controlling heat input into a component by a laser beam, comprising the steps of: periodically scanning a surface of the component with the laser beam; detecting, during the periodic scanning, photoemissions which are emitted by a predetermined partial area of the surface irradiated with the laser beam; determining a periodic temperature profile of a surface temperature and an average surface temperature based on the detected photoemissions; calculating a deviation of the average surface temperature from an upper limit of a predetermined target temperature range and from a lower limit of the predetermined target temperature range; and adjusting an energy input into the component controlled by a laser control based on the calculated deviations. The invention further relates to an alternative method and a corresponding device for controlling heat input into a component with a laser beam.

Description

FIELD OF INVENTION

The present invention relates to a method and a corresponding device for controlling a heat input into a component, as well as an alternative method and a corresponding device for controlling a heat input into a component.

TECHNICAL BACKGROUND

In the additive manufacturing of components, in-situ heat treatment can be carried out at regular intervals after melting and before or after solidification of the material to form an additive layer, or only after production. The same laser can be used, for example, to reduce residual stresses in the manufactured layers by applying targeted heat. However, it is difficult to achieve a uniform temperature distribution in the layers, as irregularly applied material, different heat dissipation, etc. cause local temperature differences. By measuring the temperature of the surface, conclusions can be drawn about the differences in order to then adjust the parameters, such as the output power of the laser, for example to prevent the material from melting again.

EN 11 2020 000895 T5 describes a method for measuring and controlling a temperature of a transfusion roller gap in which the emitted amount of radiation from a radiant heat source is modified according to radiation measured by a pyrometer.

SUMMARY OF THE INVENTION

Against this background, the present invention is based on the object of specifying an improved method for dynamically adjusting the heat input in a scanning machining process.

According to the invention, this object is achieved by a method having the features of patent claim 1, by a method having the features of patent claim 6, by a device having the features of patent claim 10 and/or by a device having the features of patent claim 13.

• - Ein Verfahren zur Regelung eines Wärmeeintrags in ein Bauteil durch einen Laserstrahl, mit den Schritten: Periodisches Scannen einer Oberfläche des Bauteils mit dem Laserstrahl; Erfassen, während des periodischen Scannens, von Photoemissionen, welche von einem mit dem Laserstrahl bestrahlten vorbestimmten Teilbereich der Oberfläche emittiert werden; Bestimmen eines periodischen Temperaturverlaufs einer Oberflächentemperatur und einer mittleren Oberflächentemperatur basierend auf den erfassten Photoemissionen; Berechnen einer Abweichung der mittleren Oberflächentemperatur von einer Obergrenze eines vorbestimmten Zieltemperaturbereichs und einer Untergrenze des vorbestimmten Zieltemperaturbereichs; und Anpassen eines durch eine Lasersteuerung geregelten Energieeintrags in das Bauteil basierend auf den berechneten Abweichungen.
• - Ein Verfahren zur Regelung eines Wärmeeintrags in ein Bauteil durch einen Laserstrahl, mit den Schritten: Scannen einer Oberfläche des Bauteils mit dem Laserstrahl entlang einer Scanstrecke; Erfassen von Photoemissionen, welche beim Scannen entlang der Scanstrecke von der Oberfläche emittiert werden; Bestimmen eines Verlaufs einer Oberflächentemperatur entlang der Scanstrecke basierend auf den erfassten Photoemissionen; Berechnen einer Abweichung der Oberflächentemperatur von einer vorbestimmten Zieltemperatur entlang der Scanstrecke; und Erneutes Scannen der Oberfläche und gleichzeitiges dynamisches Anpassen eines durch eine Lasersteuerung geregelten Energieeintrags in das Bauteil entlang der Scanstrecke basierend auf der bestimmten Abweichung der Oberflächentemperatur von der Zieltemperatur.
• - Eine Vorrichtung zur Regelung eines Wärmeeintrags in ein Bauteil durch einen Laserstrahl, mit einem Laser, welcher derart ausgebildet ist, bei einer Bestrahlung mit dem von dem Laser emittierten Laserstrahl auf eine Oberfläche des Bauteils einen Wärmeeintrag zu erzeugen; mit einer Strahlsteuerungseinrichtung, welche dazu ausgebildet ist, ein periodisches Scannen des Laserstrahls auf der Oberfläche auszuführen; mit einem Sensor, welcher dazu ausgebildet ist, Photoemissionen, welche bei dem Scannen von der mit dem Laserstrahl bestrahlen Oberfläche emittiert werden, zu detektieren; und mit einer Steuerungseinrichtung, welche mit dem Laser und dem Sensor verbunden ist, und dazu ausgelegt ist: einen periodischen Temperaturverlauf der Oberflächentemperatur und eine mittlere Oberflächentemperatur des Teilbereichs basierend auf den erfassten Photoemissionen des Teilbereichs zu bestimmen, eine Abweichung der mittleren Oberflächentemperatur von einer Obergrenze des vorbestimmten Zieltemperaturbereichs und einer Untergrenze des vorbestimmten Zieltemperaturbereichs zu berechnen, und einen durch eine Lasersteuerung geregelten Energieeintrag in das Bauteil basierend auf der bestimmten Abweichung des Maximums und Minimums von der Obergrenze und Untergrenze des vorbestimmten Zieltemperaturbereichs anzupassen.

• - Eine Vorrichtung zur Regelung eines Wärmeeintrags in ein Bauteil durch einen Laserstrahl, mit einem Laser, welcher derart ausgebildet ist, bei einer Bestrahlung mit dem von dem Laser emittierten Laserstrahl auf eine Oberfläche des Bauteils einen Wärmeeintrag zu erzeugen; und mit einer Strahlsteuerungseinrichtung, welche dazu ausgebildet ist, ein Scannen des Laserstrahls auf der Oberfläche auszuführen; mit einem dem Scannen mitgeführten Sensor, welcher dazu ausgebildet ist, Photoemissionen, welche von der mit dem Laserstrahl bestrahlten Oberfläche emittiert werden, zu detektieren; mit einer Steuerungseinrichtung, welche mit dem Laser und dem Sensor verbunden ist, und dazu ausgelegt ist: eine Oberflächentemperatur basierend auf den erfassten Photoemissionen zu bestimmen, eine Abweichung der Oberflächentemperatur von einer vorbestimmten Zieltemperatur zu berechnen, und einen durch eine Lasersteuerung geregelten Energieeintrag in das Bauteil basierend auf der berechneten Abweichung der Oberflächentemperatur von der Zieltemperatur anzupassen.

Accordingly, it is envisaged:

• - A method for controlling a heat input into a component by a laser beam, comprising the steps of: Periodically scanning a surface of the component with the laser beam; detecting, during the periodic scanning, photoemissions emitted by a predetermined partial area of the surface irradiated with the laser beam; Determining a periodic temperature profile of a surface temperature and an average surface temperature based on the detected photoemissions; Calculating a deviation of the average surface temperature from an upper limit of a predetermined target temperature range and a lower limit of the predetermined target temperature range; and adjusting an energy input into the component controlled by a laser control based on the calculated deviations.
• - A method for controlling a heat input into a component by a laser beam, comprising the steps of: scanning a surface of the component with the laser beam along a scanning path; detecting photoemissions emitted by the surface during scanning along the scanning path; determining a course of a surface temperature along the scanning path based on the detected photoemissions; calculating a deviation of the surface temperature from a predetermined target temperature along the scanning path; and re-scanning the surface and simultaneously dynamically adjusting an energy input into the component controlled by a laser control along the scanning path based on the determined deviation of the surface temperature from the target temperature.
• - A device for controlling a heat input into a component by a laser beam, with a laser which is designed to generate a heat input when irradiated with the laser beam emitted by the laser on a surface of the component; with a beam control device which is designed to carry out a periodic scanning of the laser beam on the surface; with a sensor which is designed to detect photo emissions which are emitted during the scanning from the surface irradiated with the laser beam; and with a control device which is connected to the laser and the sensor and is designed to: determine a periodic temperature profile of the surface temperature and an average surface temperature of the partial area based on the detected photo emissions of the partial area, a deviation of the average surface temperature from an upper limit of the predetermined target temperature range and a lower limit of the predetermined target temperature range, and to adjust an energy input into the component controlled by a laser control based on the determined deviation of the maximum and minimum from the upper limit and lower limit of the predetermined target temperature range.

• - A device for controlling a heat input into a component by a laser beam, with a laser which is designed to generate a heat input when irradiated with the laser beam emitted by the laser onto a surface of the component; and with a beam control device which is designed to scan the laser beam on the surface; with a sensor which is carried along with the scanning and is designed to detect photoemissions which are emitted by the surface irradiated with the laser beam; with a control device which is connected to the laser and the sensor and is designed to: determine a surface temperature based on the detected photoemissions, calculate a deviation of the surface temperature from a predetermined target temperature, and adjust an energy input into the component which is controlled by a laser control based on the calculated deviation of the surface temperature from the target temperature.

The finding underlying the present invention is that the melting of the material can be position-dependent, since the component manufactured additively here can have different heat dissipation capabilities depending on the position. This can be the case, for example, due to a different thickness or height below the irradiated surface.

The idea underlying the present invention is to measure the surface temperature of the irradiated surface of the component during scanning in order to obtain information about the current temperature in the component. Based on the information obtained in this way, a laser control system can be adjusted, which controls all parameters that influence the energy input into the component when scanning with the laser beam.

This can be achieved using two complementary and alternative methods and corresponding devices. The first method involves a stationary measurement of the surface temperature of the irradiated surface of the component during scanning. This part of the stationary measurement can be selected anywhere on the surface, but is preferably a central area. The temperature profile obtained from this is just as periodic as the scanning itself and should be within a certain target temperature range that is advantageous for heat treatment of a material. By comparing the average temperature, or alternatively the maxima and minima, of the oscillating temperature profile, statements can be made about the adjustment of the scanning parameters, in particular the laser beam power or output power of the laser, and adjusted accordingly.

The second method involves a sensor that is carried along and determines the surface temperature via detected photoemissions at or at least near the point where the laser beam is currently operating. This results in a temperature profile that fluctuates around a target temperature with a suitable output power and other parameters such as beam diameter, etc. These fluctuations are caused by irregularities in the surface temperature of areas of the surface that, for example, have different local heat dissipation capacities.

The laser can be selected differently depending on the material. Lasers with emitted wavelengths from the UV range to the far infrared are possible. Lasers in the near infrared, for example with a wavelength of around 1030 nm with Yb-doped active materials, such as fiber lasers, are preferred, as these deliver high performance with good beam quality in a reliable and cost-effective manner. For both alternative methods and devices, multi-laser systems can also be designed in which carried or stationary sensors are installed in a common or individual beam path.

A beam steering device controls the direction of the laser beam on the surface. This is usually a scanner with rotating scanning mirrors, but can also have moving or rotating transmissive optics, for example. The beam steering device also contains focusing optics to control the beam diameter.

Adjusting the laser control includes all parameters that influence the energy input into the component and thus the heat development and temperature of the component. In addition to the output power of the laser, these can be the scanning speed, the beam diameter or the beam size on the surface, a wavelength, pulse frequency, duty cycle of a modulation of the laser beam, an attenuator setting, etc. All of these parameters can be controlled by the Control device can be controlled and adjusted accordingly.

The component can be any type of component that can be subjected to heat treatment. This can include aluminum or steel alloy, each heated to 660°C or 1400°C and more to relieve residual stresses. Nickel-based alloys are also possible.

Advantageous embodiments and further developments emerge from the further subclaims and from the description with reference to the figures of the drawing.

According to a further preferred embodiment, the detection of photoemissions is carried out by a pyrometer which is sensitive in the spectral range of the photoemissions. The arrangement thus enables simple detection of photoemissions from the same partial area of the surface during the periodic scanning process.

According to a further preferred embodiment, the specific periodic temperature profile oscillates between maxima and minima approximately according to a sine curve. This is generally the case when the partial area of the surface from which the photoemissions are recorded is scanned at regular time intervals.

According to a further preferred embodiment, the upper limit of the predetermined target temperature range is below the melting temperature of a material used for the component. This is advantageous in the case of heat treatment, in-situ and post-processing, of one or more additively applied layers, for example to reduce residual stresses.

According to a preferred embodiment, the detection of photoemissions is carried out by a sensor that is carried along with the scanning. This enables a uniform detection of the photoemissions, which results in a more precise determination of the local surface temperature.

According to a further preferred embodiment, the sensor has at least one coaxially arranged photodiode. Coaxial here means that the photodiode can detect the photoemissions on the same optical axis as the scanning laser beam. A photodiode selected according to the emission spectrum has good sensitivity and has good temporal resolution. For example, when heat treating aluminum, common temperatures of around 660°C or 1400°C to 1500°C for steel can be measured, which have an emission peak according to Planck's radiation law between 1 μm and 3 μm with a corresponding width. These emissions can also be detected with a silicon diode or with an InGaAs diode. In a preferred embodiment, both types of photodiode are used to measure the photoemissions using a further beam splitter.

According to a further preferred embodiment, a calibration step is additionally provided in which the sensor is calibrated to detect the photoemissions along the scanning path. Such a calibration increases the accuracy of the temperature measurement and enables precise detection of the absolute temperature.

According to a further preferred embodiment, the periodic scanning of the surface of the component includes a heating phase in which the surface is heated from room temperature to the predetermined target temperature range. Furthermore, the deviation is determined by determining the deviations of the maxima and minima of the periodic temperature profile of the surface temperature to an upper limit and lower limit of a target temperature increase range. The target temperature increase range follows a predetermined temperature increase that is typically adapted to the material, which prevents cracking of the material, for example. In addition, the energy input into the component, which is regulated by a laser control, is adjusted based on the determined deviations, so that the surface temperature oscillates periodically within the target temperature increase range. In this way, good temperature control can be ensured even during a heating phase. Furthermore, a cooling phase is provided in which the component cools from the target temperature range to the ambient temperature. In this cooling phase, laser-based heat treatment can slow down the cooling or achieve a cooling curve by applying small amounts of energy by scanning the surface of the component.

According to a further preferred embodiment, the sensor is arranged in a stationary manner in order to detect the photoemissions emitted by a predetermined partial area of the surface irradiated with the laser. In this way, photoemissions from an area can be detected periodically following the scanning.

According to a further preferred embodiment, the sensor is designed as a thermal camera, which is used to detect the area emitted photoemissions. A thermal camera provides reliable surface temperature values of the partial area of the surface.

According to a further preferred embodiment, an output device is provided which is arranged in such a way as to output the photo emissions between the beam control device and the laser to the sensor. In this way, a detection range of the sensor can be easily moved along with the scanning.

According to a further preferred embodiment, the sensor has at least one coaxially arranged photodiode, which is designed to detect the photoemissions emitted by the surface. As already mentioned above, a coaxial arrangement in this context means that the photodiode can detect the photoemissions on the same optical axis as the scanning laser beam. A photodiode selected according to the emission spectrum has good sensitivity and has good temporal resolution.

The above embodiments and further developments can be combined with one another as desired, provided that this makes sense. In particular, all features of the device for controlling heat input into an additively manufactured component can be transferred to the corresponding methods for controlling heat input into an additively manufactured component, and vice versa.

Further possible embodiments, further developments and implementations of the invention also include combinations of features of the invention described above or below with regard to the exemplary embodiments that are not explicitly mentioned. All embodiments should also apply to multi-laser systems in which sensors are installed in a common or individual beam path. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention.

TABLE OF CONTENTS OF THE DRAWING

• 1 eine schematische Darstellung eines Ausführungsbeispiels einer Vorrichtung zur Regelung eines Wärmeeintrags in ein Bauteil;
• 2 eine schematische Darstellung eines Ausführungsbeispiels eines entsprechenden Verfahrens zur Regelung eines Wärmeeintrags in ein Bauteil;
• 3 eine schematische Darstellung einer Oberfläche des Bauteils mit eingezeichneter Scanstrecke gemäß eines Ausführungsbeispiels;
• 4 ein Diagramm eines Temperaturverlaufs gemäß eines Ausführungsbeispiels;
• 5 eine schematische Darstellung eines Ausführungsbeispiels einer Vorrichtung zur Regelung eines Wärmeeintrags in ein Bauteil;
• 6 eine schematische Darstellung eines Ausführungsbeispiels eines entsprechenden Verfahrens zur Regelung eines Wärmeeintrags in ein Bauteil; und
• 7 ein Diagramm eines Temperaturverlaufs gemäß eines Ausführungsbeispiels.

The present invention is explained in more detail below with reference to the embodiments shown in the schematic figures of the drawings. They show:

• 1 a schematic representation of an embodiment of a device for controlling heat input into a component;
• 2 a schematic representation of an embodiment of a corresponding method for controlling heat input into a component;
• 3 a schematic representation of a surface of the component with a scan path marked in accordance with an embodiment;
• 4 a diagram of a temperature curve according to an embodiment;
• 5 a schematic representation of an embodiment of a device for controlling heat input into a component;
• 6 a schematic representation of an embodiment of a corresponding method for controlling heat input into a component; and
• 7 a diagram of a temperature curve according to an embodiment.

The accompanying drawings are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the noted advantages will be apparent upon reference to the drawings. The elements of the drawings are not necessarily shown to scale with respect to one another.

In the figures of the drawing, identical, functionally identical and acting elements, features and components are provided with the same reference symbols, unless otherwise stated.

DESCRIPTION OF EXAMPLES OF IMPLEMENTATION

1 shows a schematic representation of an embodiment of a device for controlling heat input into a component with a laser beam.

In the 1 The device 1 shown has a laser 2. This is designed so that an irradiation with the laser beam 5 emitted by the laser 2 onto a surface 6a of the component 6 generates a heat input. This is usually determined by the wavelength of the laser beam 2, which must have an absorption in the material of the component 6. The 1 The component 6 shown is positioned on a base plate 9 and shows an additively applied layer 6b, which has not yet been subjected to any heat treatment, for example to reduce residual stresses. An underlying layer 6c has already been heat-treated. The device shown here is therefore used to treat the layer in-situ with heat after it has been applied by the laser beam 5. The device 1 is therefore to be regarded as part of a larger system for 3D printing, which can usually also have a powder chamber and an overflow container.

The device 1 also has a beam control device 3, which is designed to carry out a periodic scanning of the laser beam 5 on the surface 6a. In this embodiment, the beam control device 3 is designed as a scanner with scanning mirrors 3a. The scanning speed should be selected to be very high so that the most homogeneous heat input possible is achieved. Scanning speeds are typically in the range of 10 m/s to 30 m/s.

The device 1 also has a sensor 4, which is designed to detect a wavelength range of photoemissions 7, which are emitted during scanning from the surface 6a irradiated with the laser beam 5. In this first device, the sensor 4 is arranged stationary and designed as a pyrometer in order to detect the photoemissions 7 emitted by a predetermined partial area 12 of the surface 6a irradiated with the laser. The sensor 4 is alternatively designed as a thermal camera, which is designed to detect the photoemissions 7 emitted by the partial area 12 by being able to detect certain wavelength ranges in the near and mid-infrared (for example 1 μm to 3 μm).

The device also contains a control device 8 which is connected or coupled to the laser 2 and the sensor 4. The control device 8 is designed to determine a periodic temperature profile of the surface temperature Ts of the partial region 12 based on the detected photoemissions of the partial region 12. The control device 8 is also designed to calculate a deviation of a maximum T ₁ of the determined periodic temperature profile from an upper limit T _Z1 of the predetermined target temperature range ΔT _Z and a minimum T ₂ of the determined periodic temperature profile from a lower limit T _Z2 of the predetermined target temperature range ΔT _Z. Furthermore, the control device 8 is designed to adapt an energy input into the component, regulated by a laser control, based on the determined deviation of the maximum T ₁ and minimum T ₂ from the upper limit T _Z1 and lower limit T _Z2 of the predetermined target temperature range ΔT _Z. The upper limit T _Z1 of the predetermined target temperature range ΔT _Z is below the melting temperature of a material used for the component 6.

The adjustment of the laser control includes all parameters that influence the energy input into the component and thus the heat development and temperature of the component 6. In addition to the output power of the laser 2, these can be the scanning speed, the beam diameter 13 or the beam size on the surface 6a, a wavelength, pulse frequency, duty cycle of a modulation of the laser beam 5, etc. All of these parameters can be controlled by the control device 8 and adjusted accordingly.

2 shows a schematic representation of an embodiment of a corresponding method for controlling heat input into a component 6 with a laser beam.

This in 2 The method shown initially contains the step of periodically scanning S1 a surface 6a of the component 6 with the laser beam 5. During this periodic scanning, photoemissions 7 are detected S2. The photoemissions are emitted from a predetermined partial area 6a _T of the surface 6a irradiated with the laser beam 5. This area is in the field of view of a sensor 4 which detects these photoemissions. This is followed by the step of determining S3 a periodic temperature profile of a surface temperature T _S based on the detected photoemissions 7. This is determined by a control device 8. This is followed by calculating S4 a deviation of a maximum T _S1 of the determined periodic temperature profile from an upper limit T _Z1 of a predetermined target temperature range ΔT _Z and a minimum T _S2 of the determined periodic temperature profile from a lower limit T _Z2 of the predetermined target temperature range ΔT _Z and adjusting S5 an energy input into the component controlled by a laser control based on the calculated deviations.

3 shows a schematic representation of a surface 6a of the component 6 with a scan path 10 drawn in according to an embodiment.

In 3 a scanning path 10 is shown, through which the laser beam 5 passes for a heat treatment of the surface 6a of the component 6. Also visible is an example of a beam diameter 13, which can have a size of approximately 0.4 mm to 1 mm or more. This scanning path 10 is formed as a hatching, which has parallel and orthogonal scanning vectors 11. More complex shapes with curved Scan vectors 11 are also conceivable. The observation location or the partial area 12 of the surface that is in the field of view of the sensor 4 can be recognized, and thus a part of the photo emissions 7 emitted by this partial area, which are basically emitted in all directions, are recorded.

4 shows a diagram of a temperature curve according to an embodiment.

This in 4 In the diagram 20 shown, the surface temperature T _S of the partial area 12 is plotted against a horizontal time axis 21 on a vertical temperature axis 22. The temperature profile of the surface temperature Ts exhibits periodic behavior, with a time period P corresponding to the time of a run through the scanning path 10. The periodic temperature profile of the surface temperature Ts between maxima T ₁ and minima T ₂ of the periodic temperature profile oscillates approximately according to a sine curve.

First, in a heating phase 23, the periodic scanning of the surface 6a of the component 6 is carried out in order to heat the surface 6 from a room temperature to the predetermined target temperature range ΔT _Z. In this case, the deviations of the maxima T ₂ and minima T ₁ of the periodic temperature profile of the surface temperature T _S to an upper limit T _AZ1 and lower limit T _AZ2 of a target temperature increase range ΔT _Z can be determined. Furthermore, the energy input into the component controlled by the laser control can then be adjusted based on the determined deviations so that the surface temperature Ts oscillates periodically within the target temperature increase range. This then leads to the controlled temperature increase, as in 4 is shown. Furthermore, an average surface temperature 24 is shown, which is used as a reference for the deviations. This temperature follows the energy input into the component and is based on the laser beam power and the scanning speed.

During the oscillation, the cooling, i.e. the decreasing part of the oscillation between a maximum T ₂ or TA2 and a minimum T ₁ or T _A1 , is determined by the heat dissipation of the underlying material of the component 6. The local heating, i.e. the increasing part of the oscillation between a minimum T ₁ or T _A1 and a maximum T ₂ or T _A2 , is given by the scanning speed and the laser power of the laser, which locally heats a point. The increase in the average surface temperature 24 during the heating phase 23 is determined by a heating frequency, which indicates the inverse of a duration until a point on the surface of the component is repeatedly exposed. The more often the laser beam exposes a point, the more the heating predominates, and the less often this point is exposed, the more the cooling predominates. If cooling and energy input are in balance, a constant average temperature is maintained, as in 4 is shown.

In a stationary phase, a deviation of the mean temperature, alternatively the maxima T _S1 and minima T _S2 of the specific periodic temperature profile from the upper limit T _Z1 of a predetermined target temperature range ΔT _Z and from a lower limit T _Z2 of the predetermined target temperature range ΔT _Z is then calculated analogously to the method described above. This control leads to a stationary oscillation of the surface temperature T _S in the target temperature range ΔT _Z , which is essential for effective heat treatment.

5 shows a schematic representation of a further embodiment of a device 1' for controlling a heat input into a component 6 with a laser beam 5.

In the 5 The second device 1' shown is based on the device shown in 1 shown first device 1. However, it has a sensor 4' which is carried along with the scanning and is designed to detect photo emissions 7 which are emitted during the irradiation from the surface 6 irradiated with the laser beam 5. Furthermore, an outcoupling device 14 in the form of a beam splitter is provided here, which is arranged in such a way as to couple the photo emissions 7 between the beam control device 3 and the laser 2 to the sensor 4'. The sensor has at least one coaxially arranged photodiode which is designed to detect the photo emissions 7 emitted from the surface 6a. The photodiode can be a Si or InGaAs-based photodiode for detecting long-wave radiation up to the mid-infrared range. In further embodiments, a further beam splitter is provided which directs the photo emissions onto respective paths towards a Si photodiode and an InGaAs photodiode.

The device 1' is also distinguished by a slightly adapted control device 8 in order to determine a surface temperature Ts based on the detected photoemissions 7, to calculate a deviation of the surface temperature T _S from a predetermined target temperature T _Z , and to adjust an output power of the laser 2 based on the calculated deviation of the surface temperature Ts from the target temperature T _Z. Since the sensor is carried along here, it is essential that the control device 8 also processes the data provided by the sensor 4' relatively quickly, for example in the kHz range. and can quickly control the output power of laser 2.

6 shows a schematic representation of an embodiment of a corresponding method for controlling a heat input into a component 6 with a laser beam 5.

The method 1' shown comprises the step of scanning S1` a surface 6a of a component 6 with a laser beam 5 along a scanning path 10. Then, a detection S2` of photoemissions 7 which are emitted from the surface 6a during scanning along the scanning path 10 takes place. Furthermore, a determination S3' of a profile of a surface temperature Ts along the scanning path 10 is provided based on the detected photoemissions. This is used to calculate S4' a deviation of the surface temperature Ts from a predetermined target temperature T _Z along the scanning path 10. Furthermore, the surface 6a is scanned again, with a simultaneous dynamic adjustment of an output power of the laser 2 along the scanning path 10 being carried out based on the determined deviation of the surface temperature Ts from the target temperature T _Z.

Furthermore, the additional step of calibration can be provided, in which the sensor 4' is calibrated to detect the photoemissions 7 along the scanning path 10.

7 shows a diagram of a temperature curve according to an embodiment.

This in 7 In the diagram 30 shown, the surface temperature T _S measured along the scanning path 11 is plotted against a horizontal time axis 31 on a vertical temperature axis 32. The temperature profile of the surface temperature T _S follows a target temperature T _Z , although these differ from one another. The curve shown here as an example corresponds to the passage through a scanning path 10. If the starting point is known, it is possible to see in which areas of the scanning path 10 a slightly too high surface temperature Ts has formed and in which areas of the surface 6a a slightly too low surface temperature Ts has formed. These temperature fluctuations can be compensated by appropriate dynamic adjustment of the output power of the laser 2 or the laser beam power of the laser beam 5 during the following scanning processes.

Although the present invention has been fully described above using preferred embodiments, it is not limited thereto, but can be modified in many different ways. In particular, the embodiments described above contain simplified optical systems. For example, an optical element for beam attenuation can be provided, for example in the form of an A/2 plate in combination with a polarizer. Furthermore, a focusing optics can be provided that can be controlled to vary the beam diameter. This focusing optics can be integrated in the scanner and arranged upstream or downstream of the scanning mirrors. Although only one laser is mentioned in the above embodiments, the above method also applies to devices with several similar or different lasers that are used for scanning. Furthermore, the beam diameter can also be varied, which can be achieved, for example, by controlling a focusing optics in the scanner. Furthermore, the scanning speed or a dwell time of the laser beam can also be varied.

List of reference symbols

1, 1'

Devices

2

Laser

3

Beam control device

4, 4`

Sensors

5

laser beam

6

Component

6a

Surface of the component

6b

Section of the component to be treated

6c

untreated section of the component

7

Photoemissions

8th

Control device

9

Base plate

10

Scanning path

11

Scan vector

12

Observation point/part of the surface

13

Beam diameter

14

Output optics

20

Temperature curve diagram

21

Timeline

22

Temperature axis

23

Heating phase

24

Average surface temperature

30

Temperature curve diagram

31

Timeline

32

Temperature axis

P

Period of a scan run

S1 - S5

Process steps

S1' - S5'

Process steps

TAZ1

Upper limit of the target temperature rise range

TAZ2

Lower limit of the target temperature rise range

TS

recorded surface temperature

TS1

Maximum of the periodic temperature curve

TS2

Minimum temperature of the periodic temperature curve

ΔTZ

Target temperature range

TZ

Target temperature

TZ1

Upper limit of the target temperature range

TZ2

Lower limit of the target temperature range

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EN 112020000895 T5 [0003]

Claims (15)

Method for controlling heat input into a component (6) by a laser beam (5), comprising the steps of: Periodically scanning (S1) a surface (6a) of the component (6) with the laser beam (5); Detecting (S2), during the periodic scanning, photoemissions (7) emitted by a predetermined partial region (12) of the surface (6a) irradiated with the laser beam (5); Determining (S3) a periodic temperature profile of a surface temperature (T _S ) and an average surface temperature (24) based on the detected photoemissions (7); Calculating (S4) a deviation of the average surface temperature (24) from an upper limit (T _Z1 ) of a predetermined target temperature range (ΔT _Z ) and a lower limit (T _Z2 ) of the predetermined target temperature range (ΔT _Z ); and adjusting (S5) an energy input into the component (6) controlled by a laser control based on the calculated deviations, wherein the scanning parameters comprise at least a laser beam power. Procedure according to Claim 1 , characterized in that the detection of photoemissions (7) is carried out by a pyrometer which is arranged and designed to detect the photoemissions (7) of the irradiated predetermined partial region (12) of the surface (6). Procedure according to Claim 1 or 2 , characterized in that the determined periodic temperature profile between maxima (T ₁ ) and minima (T ₂ ) oscillates periodically approximately according to a sine curve. Procedure according to Claim 3 , characterized in that the upper limit (T _Z1 ) of the predetermined target temperature range (ΔT _Z ) is below the melting temperature of a material used for the component (6). Method according to one of the preceding claims, characterized in that the periodic scanning of the surface (6a) of the component (6) comprises a heating phase (23) in which the surface (6) is heated from a room temperature to the predetermined target temperature range (ΔT _Z ), and that the determination of the deviation is carried out by determining the deviations of the maxima (T ₂ ) and minima (T ₁ ) of the periodic temperature profile of the surface temperature (T _S ) to an upper limit (T _AZ1 ) and lower limit (T _AZ2 ) of a target temperature increase range, and that the adaptation of the energy input into the component (6) regulated by the laser control is carried out based on the determined deviations, so that the surface temperature (T _S ) oscillates periodically within the target temperature increase range. Method (1') for controlling heat input into a component (6) by a laser beam (5), comprising the steps of: scanning (S1') a surface (6a) of the component (6) with the laser beam (5) along a scanning path (10); detecting (S2') photoemissions (7) emitted from the surface (6a) during scanning along the scanning path (10); determining (S3') a profile of a surface temperature (T _S ) along the scanning path (10) based on the detected photoemissions; calculating (S4') a deviation of the surface temperature (T _S ) from a predetermined target temperature (T _Z ) along the scanning path (10); and re-scanning the surface (6a) and simultaneously dynamically adjusting an energy input into the component (6) along the scanning path (10) controlled by a laser control based on the determined deviation of the surface temperature (T _S ) from the target temperature (T _Z ), wherein the scanning parameters comprise at least a laser beam power. Procedure according to Claim 6 , characterized in that the detection (S2') of photoemissions (7) is carried out by a sensor (4') carried along with the scanning. Procedure according to Claim 7 , characterized in that the sensor (4') has at least one coaxially arranged photodiode. Method according to one of the Claims 5 until 8th , characterized in that a calibration step is additionally provided in which the sensor (4') for detecting the photoemissions (7) along the scanning path (10) is calibrated. Device (1) for controlling a heat input into a component (6) by a laser beam (5), in particular using a method according to one of the Patent claims 1 until 9 , with a laser (2) which is designed to generate a heat input when irradiated with the laser beam (5) emitted by the laser (2) onto a surface (6a) of the component (6); with a beam control device (3) which is designed to carry out a periodic scanning of the laser beam (5) on the surface (6a); with a sensor (4) which is designed to detect photoemissions (7) which are generated during the scanning of the surface irradiated with the laser beam (5). (6a) are emitted; and with a control device (8) which is connected to the laser (2) and the sensor (4) and is designed to: - determine a periodic temperature profile of the surface temperature (T _S ) of the partial region (12) based on the detected photoemissions (7) of the partial region (12), - calculate a deviation of an average surface temperature (24) from an upper limit (T _Z1 ) of the predetermined target temperature range (ΔT _Z ) and a lower limit (T _Z2 ) of the predetermined target temperature range (ΔT _Z ), and - adapt an energy input into the component (6) regulated by a laser control based on the determined deviation of the maximum (T ₁ ) and minimum (T ₂ ) from the upper limit (T _Z1 ) and lower limit (T _Z2 ) of the predetermined target temperature range (ΔT _Z ). Device according to Claim 10 , characterized in that the sensor (4) is arranged stationary in such a way as to detect the photoemissions (7) emitted by a predetermined partial region (12) of the surface (6a) irradiated with the laser (2). Device according to Claim 11 , characterized in that the sensor (4) is designed as a thermal camera which is designed to detect the photoemissions (7) emitted by the partial region (12). Device (1') for controlling a heat input into a component (6) by a laser beam (5), in particular using a method according to one of the Patent claims 1 until 9 , with a laser (2) which is designed to generate a heat input when irradiated with the laser beam emitted by the laser (2) on a surface (6a) of the component (6); with a beam control device (3) which is designed to scan the laser beam (5) on the surface (6a); with a sensor (4') which is carried along with the scanning and which is designed to detect photoemissions (7) which are emitted by the surface (6a) irradiated with the laser beam (5); and with a control device (8) which is connected to the laser (2) and the sensor (4') and is designed to: - determine a surface temperature (T _S ) based on the detected photoemissions (7), - calculate a deviation of the surface temperature (T _S ) from a predetermined target temperature (T _Z ), and - adapt an energy input into the component (6) controlled by a laser control based on the calculated deviation of the surface temperature (T _S ) from the target temperature (T _Z ). Device according to Claim 13 , characterized in that an outcoupling device (14) is provided which is arranged to couple the photoemissions (7) between the beam control device (3) and the laser (2) to the sensor (4'). Device according to Claim 13 or 14 , characterized in that the sensor (4') has at least one coaxially arranged photodiode which is designed to detect the photoemissions (7) emitted from the surface.

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