DE102022109014A1 - Device for producing and/or processing a workpiece, in particular for additively producing a workpiece and method for operating a device - Google Patents

Abstract

A device (100) for producing and/or processing a workpiece (105), in particular for additively producing a workpiece (105), is presented. The device (100) has a laser unit (110), an illumination unit (115) and a detection unit (120). The laser unit (110) is designed to emit a laser light beam onto the workpiece (105) in order to process the workpiece (105). The lighting unit (115) for illuminating the workpiece (105) is designed to illuminate the workpiece (105) with a light of a first wavelength, to obtain a first light reflected by the workpiece (105) and to illuminate the workpiece (105). to illuminate with a light having a second wavelength different from the first wavelength in order to obtain a second light reflected by the workpiece (105). The determination unit (120) for reading in the first and second light reflected by the workpiece (105) is designed to determine a parameter of the workpiece (105) using a size of the reflected first light and a size of the reflected second light.

Description

State of the art

The invention is based on a device or a method according to the preamble of the independent claims. The subject of the present invention is also a computer program.

Materials for scan-based laser material processing may exhibit fluctuations or contamination. This can be detected using upstream or in situ inspection steps and corrected actively or passively in the machining process. The DE 10 2016 000 415 A1 describes a device for three-dimensional detection of a surface structure.

Against this background, the approach presented here presents a device for producing and/or processing a workpiece, in particular for additively producing a workpiece, and a method for operating a device and finally a corresponding computer program according to the main claims. The measures or features listed in the dependent claims make advantageous developments and improvements of the device specified in the independent claim possible.

The advantages that can be achieved with the approach presented here are, in particular, that a device is created which can draw conclusions about a parameter, for example of the material, of the workpiece based on lights reflected on a workpiece.

A device for producing and/or processing a workpiece, in particular for additively producing a workpiece, is presented. The device has a laser unit, an illumination unit and a detection unit. The laser unit is designed to emit a laser light beam onto the workpiece in order to process the workpiece. The lighting unit for illuminating the workpiece is designed to illuminate the workpiece with a light of a first wavelength, to obtain a first light reflected by the workpiece and to illuminate the workpiece with a light having a second wavelength different from the first wavelength, to obtain a second light reflected from the workpiece. The determination unit for reading in the first and second light reflected by the workpiece is designed to determine a parameter of the workpiece using a size of the reflected first light and a size of the reflected second light. The determination unit can comprise a light-sensitive sensor, for example a photodiode, or an image sensor, for example a CCD or CMOS image sensor. It can be designed as a camera.

The device can be, for example, a device for laser welding a workpiece, or a device for additive manufacturing of a workpiece by selective laser melting. In the latter case, it can involve the selective melting of a powder, in particular a metal powder. Such a metal powder may comprise one or more different metals. It may additionally include non-metallic components.

The approach proposed here is based on the knowledge that by evaluating the quantities of the reflected first light and the reflected second light, it is possible to draw a conclusion about a parameter of the workpiece or the material. For example, it can be exploited that a type of material, for example a certain metal, has a different absorption behavior in different frequency ranges or different wavelengths, so that by evaluating the size, which can be an intensity, for example, a conclusion can be drawn about the type or nature of the current illuminated material can be closed. This can also be used, for example, when a material is formed or changed during processing, so that not only a structure that is created during processing can be recognized or detected, but also processing errors can be discovered, which, for example, lead to a faulty connection of certain Components lead and therefore do not correspond to the expected parameter.

The approach proposed here offers the advantage that the parameters of the material can be determined as accurately as possible using technically simple means. Components that are often already available can be used and, if necessary, modified or supplemented with little effort. In this way, additional benefits can be achieved very easily in existing material processing units.

The approach presented here can also be understood as multispectral illumination with an arrangement for scanning a surface with absorption coefficient determination. The approach presented here can enable high resolution for large processing fields, which can, for example, detect point defects. Furthermore, the orientation of the investigation can A perspective error can be prevented and obscurations, such as shadows, of small 3D structures by other structures can be prevented. In addition, a subsequent control using a further process step can be omitted. The approach presented here can enable a process with inline monitoring where no further testing is necessary. In addition, a high-resolution image of the surface and the processing can be made possible.

Multi-wavelength lighting can improve the image. For example, the surface can be viewed or analyzed in the visual range and the weld seams through plastic in the infrared range. If it is not possible to “view” the weld seams in the infrared range due to poor transparency of the batch, it is possible, for example, to easily switch to another infrared range source. Furthermore, a derivation of the degree of absorption and a correction of the laser power or the laser path derived therefrom can be made possible. In addition, a depth of field can be achieved via wavelength shift.

According to one embodiment, the laser unit and the illumination unit can be designed to at least partially guide the reflected light beams of the first light and the second light and the laser light beam in a common optical path. Advantageously, an image of a surface of the workpiece can be reliably recorded with components already present and, if possible, without major optical distortions. This can also save installation space.

According to a further embodiment, the laser unit, the lighting unit and additionally or alternatively the determination unit can have at least one pivotable mirror. Additionally or alternatively, the detection unit can have a semi-transparent mirror. Advantageously, the pivotable mirror can be aligned as required and can guide a laser light beam from the laser unit and reflect the light reflected on the workpiece, so that multiple uses of a component can be realized.

According to a further embodiment, the lighting unit can be designed to output at least the first light and the second light at the same time and additionally or alternatively at different times. Additionally or alternatively, the lighting unit may have a first unit for illuminating the workpiece with the first light and a second unit for illuminating the workpiece with the second light. Advantageously, the workpiece can be illuminated with one wavelength or with several wavelengths as required. This makes it possible, for example, to obtain a high-resolution image of a surface of the workpiece. Illumination with several wavelengths, namely at least 2, advantageously at least 4 and particularly advantageously six or more, enables a better image or an improved evaluation option of the workpiece. For example, the surface of the workpiece can be “viewed” or evaluated in the wavelength range visible to the human eye and weld seams, for example, in the infrared range. You can easily switch between wavelengths; For example, if the weld seams are not visible in the infrared range due to poor transparency, you can switch to a source of a different wavelength.

According to a further embodiment, the determination unit can comprise a camera or an optical image sensor, which can be designed as a matrix sensor, for example a CCD or CMOS sensor. A matrix sensor can include several light sensor elements that can be evaluated separately. This allows a two-dimensional image to be provided. According to a further embodiment, the determination unit can have a 0-dimensional light sensor, i.e. one with only one light sensor element, for example a photodiode. The determination unit can also have replaceable and/or selectable color filters for filtering light with different wavelengths, at least two, advantageously at least four and particularly advantageously six or more replaceable and/or selectable color filters. Advantageously, the light can be reliably filtered to a wavelength to be examined using technically simple means.

According to a further embodiment, the determination unit can be designed to evaluate an intensity of the first light and the second light as the size of at least the first light and the second light. The intensity of the light can be understood as a grayscale value. Based on the determined gray scale value, very precise conclusions can advantageously be drawn about material-dependent absorption properties and reflection properties.

According to a further embodiment, the determination unit can be designed to evaluate, as the parameter of the workpiece, a material type of the workpiece and additionally or alternatively a quality of a processing structure of the workpiece produced by the laser light beam. The quality can be, for example, a quality of the processing structure. Advantageously, conclusions can be drawn about the material type, material properties, process errors, geometry and height profiles.

According to a further embodiment, the determination unit can have a focusing optics unit. A distance of a portion of the workpiece to the focusing optics can be detected by evaluating a focal plane of the first light and a focal plane of the second light. Such an embodiment offers the advantage of being able to adjust the optical projection properties for detecting the reflected light as well as possible when using a scanner in order to be able to obtain a focused point on the surface of the material from different viewing directions of the scanner.

According to a further embodiment, the focusing optics unit can have at least one aspherical lens. Advantageously, improved image quality can be achieved using an aspherical lens. In other words, an aspherical lens can mean that the focusing optics unit can produce a sharp image across the processing field and the wavelengths used.

According to a further embodiment, the lighting unit can be designed to illuminate the workpiece at least with a light with a third wavelength that is different from the first wavelength and the second wavelength in order to obtain a third light reflected by the workpiece, in particular wherein the lighting unit is designed to illuminate the workpiece with lights of six wavelengths. The determination unit can be designed to detect the third light reflected by the workpiece in order to determine a parameter of the workpiece using a size of the third light. Advantageously, for example, an even more precise determination of the parameter of the material can be achieved, since at least one additional size is used to determine the parameter of the workpiece. It is also conceivable that light with more than three different wavelengths is evaluated, for example light with six different wavelengths. In this way, a further improved determination of the parameters of the workpiece can be achieved based on the variables to be further evaluated.

A method for operating a device for producing and/or processing a workpiece, in particular for additively producing a workpiece, has an output step, an activation step, a detection step and a determination step. The outputting step is carried out to output the laser light beam from the laser unit to process the workpiece at at least one processing location. The step of activating is carried out to activate the lighting unit, to illuminate the workpiece with a light of a first wavelength at an illumination location which contains the processing location, to obtain a first light reflected from the workpiece and to illuminate the workpiece at the To illuminate the lighting point with a light with a second wavelength that is different from the first wavelength in order to obtain a second light reflected by the workpiece. The detecting step is performed to detect the first and second lights reflected from the workpiece. The step of determining is carried out to determine a parameter of the workpiece at least at the machining location using a magnitude of the reflected first light and a magnitude of the reflected second light. This also allows the advantages of the approach described here to be realized very efficiently. The steps of recording and determining can take place after the step of activating, which can mean that the result of processing the respective processing point is recorded. The steps of detecting and determining can also advantageously take place before the step of activating, which can mean that a parameter of the workpiece or a material parameter is detected before the respective processing point is processed. The capture and discovery steps can also be performed twice, before activation and after activation. A comparison of the determined parameters at the processing point before processing and after processing can then be possible. It is also possible for the parameter to be recorded in the vicinity of the processing point depending on the location. The parameter can be determined both at locations that have already been processed and/or at locations that have not yet been processed. For example, if an image sensor is used, the parameters can be determined at several locations with just one recording at a time. The parameter can also be determined, for example, as an average value over an image area.

Specifically, in additive manufacturing, the parameters of the material (e.g. metal powder) are determined before it is melted or added to the workpiece. In this case, the material at the processing point then becomes part of the workpiece. The parameter can also be determined either at the processing point or as an average over a larger image area.

According to a particularly favorable embodiment, following the step of Determining a step of calculating a target laser energy from the parameter takes place, the laser light beam with the calculated target laser energy being output to the processing point. Such an embodiment offers the advantage of being able to determine an appropriate amount of energy depending on the material identified that is to be processed or added to a workpiece. In this way, inefficient processing due to the output of too much energy or damage to the workpiece can be avoided.

According to another embodiment, the light beam can also be emitted with the target laser energy in the output step in such a way that a material present, in particular a metal powder, is melted at the processing point. Such an embodiment offers the advantage of particularly efficient and therefore quick and energy-saving production/processing of the workpiece.

An embodiment is also conceivable in which, in the output step, the target laser energy is adjusted by changing an output power of the laser and/or a pulse duration of the laser and/or a number of laser pulses. Such an embodiment offers the advantage of a rapid modification of the power or energy to be output by the laser source, thus enabling a rapid response to a changed environmental situation and/or variable material composition.

A method according to the invention can be carried out several times in succession. The multiple execution can take place at different processing points. For this purpose, the workpiece can be moved relative to the laser light beam, which can be done, for example, by moving the workpiece and/or the laser light beam.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control device.

The approach presented here also creates a control device that is designed to carry out, control or implement the steps of a variant of a method presented here in corresponding devices. This embodiment variant of the invention in the form of a control device can also solve the problem on which the invention is based quickly and efficiently.

For this purpose, the control device can have at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, at least one interface to a sensor or an actuator for reading in sensor signals from the sensor or for outputting data or control signals to the Have an actuator and / or at least one communication interface for reading or outputting data that is embedded in a communication protocol. The computing unit can be, for example, a signal processor, a microcontroller or the like, whereby the storage unit can be a flash memory, an EEPROM or a magnetic storage unit. The communication interface can be designed to read or output data wirelessly and/or by wire, wherein a communication interface that can read or output wired data can, for example, read this data electrically or optically from a corresponding data transmission line or output it into a corresponding data transmission line.

In the present case, a control device can be understood to mean an electrical device that processes sensor signals and, depending on them, outputs control and/or data signals. The control device can have an interface that can be designed in hardware and/or software. In the case of a hardware design, the interfaces can, for example, be part of a so-called system ASIC, which contains a wide variety of functions of the control unit. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In the case of software training, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

Also advantageous is a computer program product with program code that can be stored on a machine-readable medium such as a semiconductor memory, a hard drive memory or an optical memory and is used to carry out, implement and/or control the steps of the method according to one of the embodiments described above, if the program is executed on a computer or a control device.

• 1 eine schematische Darstellung eines Ausführungsbeispiels einer hier vorgestellten Vorrichtung;
• 2 eine schematische Darstellung eines Ausführungsbeispiels einer hier vorgestellten Vorrichtung;
• 3 eine schematische Draufsichtdarstellung eines Werkstücks nach einer Bearbeitung mit einer Vorrichtung gemäß einem Ausführungsbeispiel;
• 4 ein Histogramm mit Wellenlängenbereichen zur Erläuterung einer Funktionsweise einer hier vorgestellten Vorrichtung gemäß einem Ausführungsbeispiel;
• 5a eine schematische Darstellung von Bildebenen für eine spezifisch verwendete Wellenlänge zur Erläuterung einer Funktionsweise einer hier vorgestellten Vorrichtung gemäß einem Ausführungsbeispiel;
• 5b eine schematische Draufsichtdarstellung von Schichten zur Erläuterung einer Funktionsweise einer hier vorgestellten Vorrichtung gemäß einem Ausführungsbeispiel;
• 6 ein Ablaufdiagramm eines Ausführungsbeispiels eines Verfahrens zum Betreiben einer Vorrichtung gemäß einem Ausführungsbeispiel; und
• 7 ein Ablaufdiagramm eines Ausführungsbeispiels eines Steuergeräts zum Betreiben einer Vorrichtung gemäß einem Ausführungsbeispiel.
• 8 ein Ablaufdiagramm eines zweiten Ausführungsbeispiels des Verfahrens

Exemplary embodiments of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows:

• 1 a schematic representation of an exemplary embodiment of a device presented here;
• 2 a schematic representation of an exemplary embodiment of a device presented here;
• 3 a schematic top view representation of a workpiece after processing with a device according to an exemplary embodiment;
• 4 a histogram with wavelength ranges to explain the functionality of a device presented here according to an exemplary embodiment;
• 5a a schematic representation of image planes for a specifically used wavelength to explain the functionality of a device presented here according to an exemplary embodiment;
• 5b a schematic top view representation of layers to explain the functionality of a device presented here according to an exemplary embodiment;
• 6 a flowchart of an exemplary embodiment of a method for operating a device according to an exemplary embodiment; and
• 7 a flowchart of an exemplary embodiment of a control device for operating a device according to an exemplary embodiment.
• 8th a flowchart of a second exemplary embodiment of the method

In the following description of favorable exemplary embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, with a repeated description of these elements being omitted.

1 shows a schematic representation of an exemplary embodiment of a device 100 for processing a workpiece 105. The device 100 is, for example, a device for welding workpieces using laser light beams.

In order to be able to carry out such processing, the device 100 has a laser unit 110, an illumination unit 115 and a determination unit 120. According to one exemplary embodiment, the determination unit 120 comprises a camera 125 with a color filter 130 and/or a focusing optics unit 120a. The color filter 130 can also be referred to as a switchable filter for different wavelengths. According to one embodiment, the color filter 130 has a plurality of interchangeable color filters for filtering light with different wavelengths, in this embodiment six interchangeable color filters, which are arranged, for example, in a filter rail or a turret system. According to one exemplary embodiment, optics 175 of the camera channel with possible optical z adjustment are arranged between the color filter 130 and the laser unit 110. According to one exemplary embodiment, the device 100 has a control device 155, which can also be referred to as a control unit, and a computer 153, which can also be referred to as an evaluation PC, which is connected to other components of the device 100 in a signal-transmitting manner. The area of an optical head 170 is shown as an example.

The laser unit 110 is arranged, for example, between the determination unit 120 and the focusing optics unit 120a, which can also be referred to as laser focusing optics. The laser unit 110, which can also output laser light into a laser path, is designed to emit a laser light beam onto the workpiece 105 in order to process the workpiece 105. For example, the workpiece 105, which is also referred to as the workpiece, can be welded using the laser light beam. In order to emit the laser light beam onto the workpiece 115, the device 100 has a partially transparent mirror 135, which is arranged obliquely below the laser unit 110 and directs the laser light beam onto the workpiece 105. The mirror 135 can also be referred to as a laser coupling or beam splitter. In the exemplary embodiment shown here, the laser light beam runs through an optical path 140, which is L-shaped, so that at least one further mirror 145 (possibly also two further mirrors) is arranged on an opposite side of the mirror 135 in order to work together with the mirror 135 to direct the laser light beam onto the workpiece 105. According to one exemplary embodiment, the mirror 135 or the further mirror 145 is designed to be pivotable and can be arranged on the laser unit 110, the lighting unit 115 and/or the determination unit 120.

According to a further exemplary embodiment, the device 100 has a scanning unit 150, which can also be referred to as an x,y scanner and which is designed to move the laser light beam of the laser unit 110 over the workpiece 105 by tilting the further mirror 145. The scanning unit 150 is arranged, for example, between the laser unit 110 and the focusing optics unit 120a. For example, the lighting unit 115 is arranged below the focusing optics unit 120a.

The lighting unit 115 is designed to illuminate the workpiece 105. Points to this the lighting unit 115, for example, has a light source or multiple light sources for outputting light in multiple wavelengths in order to illuminate the workpiece 105 with a light of at least two wavelengths. The illumination unit 115 may also be referred to as multi-wavelength light illumination. The lights emitted from the illumination unit 115 are reflected from the workpiece 105, so that the reflected lights are guided through the optical path 140 using the mirrors 135, 145. The laser unit 110 and the illumination unit 115 are designed according to an exemplary embodiment to guide the reflected light beams of the first light and the second light and the laser light beam together through the optical path 140.

More specifically, the lighting unit 115 illuminates the workpiece 105 with a light of a first wavelength. The light is reflected from the workpiece 105 to produce a reflected first light. Further, the illumination unit 115 illuminates the workpiece 105 with a light of a second wavelength to obtain a second light reflected from the workpiece 105. The first wavelength and the second wavelength are different. According to an exemplary embodiment, the lighting unit 115 is designed to output at least the first light and the second light at the same time and/or at different times. Additionally or alternatively, the lighting unit 115 has a first unit 160 and a second unit 165. The first unit 160 is designed to illuminate the workpiece 105 with the first light and the second unit 165 is designed to illuminate the workpiece 105 with the second light. According to one exemplary embodiment, a distance of a portion of the workpiece 105 to the focusing optics unit 120a can be detected by evaluating a focal plane of the first light and a focal plane of the second light. The optics of the focusing optics unit 120a are designed in such a way that the axial color error of the laser optics, F-theta, creates a dispersion difference through targeted glass selection and, in interaction with the laser optics, an apo- or achromation of the camera path is generated. According to an exemplary embodiment, the focusing optics unit 120a has at least one aspherical lens. This means that the camera can produce a sharp image across the processing field and the wavelengths used.

The determination unit 120 is designed to read in the first light reflected from the workpiece 105 and the reflected second light. After reading, the determination unit 120 determines a parameter of the workpiece 105 using a size of the reflected first light and a size of the reflected second light. According to one exemplary embodiment, the determination unit 120 is designed to evaluate, as the parameter of the workpiece 105, a material of the workpiece 105 and/or a quality, i.e. a quality, of a processing structure of the workpiece 105 produced by the laser light beam. According to a further exemplary embodiment, the determination unit 120 is designed to evaluate an intensity, i.e. the gray level of the first light and the second light, as the size of the first light and the second light.

According to an exemplary embodiment, the lighting unit 115 is designed to illuminate the workpiece 105 with at least one light with a third wavelength that is different from the first wavelength and the second wavelength in order to obtain a third light reflected by the workpiece 105. The lighting unit 115 can also be designed to illuminate the workpiece 105 with lights of more than three, for example six, wavelengths. The determination unit 120 is accordingly designed to detect the third light reflected by the workpiece 105 (or, in the case of lights with correspondingly more wavelengths, this too) in order to determine a parameter of the workpiece 105 using a size of the third light (or the sizes of the other detected lights of different wavelengths).

In other words, the approach presented here enables inline monitoring of a scanrer-based welding process with different wavelengths in trough-the-lens operation, TTL for short, through the processing optics using multispectral lighting. Absorption properties, material properties, process errors, geometry and height profiles can be derived from the data obtained.

The basic mechanical structure and function are already known, so only a few changes/adaptations are necessary. Multi-wavelength illumination is made possible with at least two different sources, for example via the illumination unit 115, which can also be referred to as ring lights, around the focusing optics unit 120a or similar. A longitudinal chromatic aberration of the focusing optical unit 120a is compensated for using a liquid lens or an autofocus lens, which makes complete observation in TTL possible.

Switching the illumination wavelength is regulated via a filter 130 in the observation channel when units 160, 165, which can also be referred to as sources, are switched on. It is also possible to switch the individual units 160, 165 on and off.

It is also possible to arrange an optical z-axis in the optical path 140, which can also be referred to as the beam path of the laser, in front of the observation channel in order to adaptively correct the longitudinal chromatic aberration. Alternatively, the z-axis, for example liquid lens, autofocus lens, is only accommodated in the optical path 140, which can also be referred to as an observation channel, in front of the mirror 134.

A lateral color error is corrected by targeted control of the scanner mirrors. An imaging error or distortion is corrected via the computer 153, which can also be referred to as evaluation software. This is made possible using the laser look-up table (LLUT) that is common in 2D scanners. This forms the basis for the camera look-up table (CLUT) simulations. For this simulation, the optical setup including the camera channel is simulated. The real behavior of the scanning unit 150, which can also be referred to as a scanner, and the focusing optics unit 120a, which can also be referred to as F-theta, is described with sufficient precision via the LLUT at the wavelength of the processing laser used, for example λ = 1064 nanometers. Separate CLUTs are simulated for each illumination wavelength. For this purpose, the positions of the scanner mirrors are optimized so that a dot grid of 21 x 21 can be approached using the LLUT at the wavelength of the processing laser used. The same grid can be used for the illumination wavelengths. As a result, the lateral chromatic aberration caused by the F-theta, which increases from the center to the corners of the work area, is corrected by the scanning unit 150. However, this method can only correct a 1-dimensional signal and not a 2-dimensional signal from a camera sensor surface. This means that a square is imaged as a distorted square by the laser optics. This effect increases as the working surface angle increases. For this reason, in a second simulation step, a square area on the work surface is assumed for each grid point and projected onto the camera sensor by the system. The image of the center of the square area (x, y) also corresponds exactly to the camera center in the imaging plane. Furthermore, the distance of the corner points (x1, y1 / x2, y2 / x3, y3 / x4, y4) to the center point (x, y) is determined and two scaling factors are formed for each corner coordinate by comparing them with the real dimensions in the work area. This results in the CLUT, with which a certain distortion is applied to the camera image for each work area position approached in order to obtain a geometrically correct image. If positions between the 21 x 21 point grids are approached, the target positions and scaling factors are interpolated with two (exactly on a line between two points) or with four neighboring points (in the space between four points). The data also makes it possible to scan the entire work area with the camera and create a composite overview image. A separate CLUT is calculated for each wavelength.

In order to be able to draw conclusions about the absorption properties and reflection properties of the materials, the individual exposure times are determined via a calibration step. This can be done using a highly reflective calibrated test target. The spectral behavior of the material must be known precisely and would ideally have 100 percent reflectivity at all wavelengths, although this is technically only possible to a limited extent. The average gray value of the image determined during the exposure time corresponds to the reflectivity of the test target. Due to clipping apertures in the camera channel, geometric shadowing occurs in the individual image. At a maximum gray value of 255 in the histogram of the image, the center is already overexposed and information is lost. The exposure time is therefore deliberately set so that the grayscale value of 255 is not exceeded. Consequently, a higher value corresponds to a reflectance greater than 100 percent.

In order to correct the grayscale wedge caused by the shading from the center of the image to the edge of the image, the shading in the individual image is set to the gray value of 255 using a white balance. An image of the calibrated test target with the determined exposure times serves as the basis. For each image taken in the future, the pixels of the correction are added to the pixels of the image.

A histogram is then derived from the corrected individual images or from the combined images, as will be shown and described in more detail below. Two values of the histogram are crucial for deriving the extinction from the images, namely the mean gray value µ and the standard deviation σ. The average value of the histogram indicates the maximum grayscale value of 255 and therefore corresponds to 100 percent reflection at a certain wavelength. The gray scale value 0 corresponds to an absorption of 100 percent. From the change in the histogram at different illumination wavelengths, conclusions can then be drawn about the material-dependent absorption properties and reflection properties of the powder or in general of the material or material type. The range of the absorption values can be derived from the standard deviation of the histogram.

For absorption mapping of the work area, the absorption values can be determined for individual tiles with, for example, 200 x 200 pixels. A literature value or known absorption values can be used as a basis for each wavelength. The absorbance derived from the histogram, subtracted from the known absorption value, forms an absolute value and indicates significant deviations. A threshold is set for the absolute value of each tile, which corresponds to the absorbance derived from the standard deviation of the histogram σ. An absolute value below this threshold corresponds to the value 0. An addition of all wavelengths of the individual tiles forms the absorption data for a multispectral overview image in which the material deviations are shown in greater detail ( 5b) . If no deviation occurs, the course of the histogram is identical for all other wavelengths and spatial coordinates. The information collected is used to readjust the laser power or the laser path for the downstream process. Another advantage is to take advantage of the axial chromatic error. The focus of the image is specifically shifted in z by changing the wavelength. This means that a larger depth of field range of the process area is covered.

2 shows a schematic representation of an exemplary embodiment of a device 100 presented here for processing a workpiece 105. These are the ones in 1 described device 100 or a similar device.

The focusing optics unit 120a can be referred to, for example, as F-theta optics. According to one embodiment, the mirror 135 is formed as a dichroic mirror.

An xyz axis 200 is shown as an example. The workpiece 105 has, for example, an uneven surface, with a section 205 of the workpiece 105 in 3 is described in more detail. According to one exemplary embodiment, the uneven surface of the workpiece 105 represents a powder layer 210. For example, in selective laser melting, a powder layer is applied to the workpiece 105 and/or remelted using the laser beam. This process can be repeated as desired, so that the workpiece 105 can have a plurality of powder layers. In the exemplary embodiment shown here, the workpiece 105 has a plurality of powder layers 210, which creates the uneven surface.

3 shows a schematic top view of a three-dimensional surface, with the differently hatched elements indicating the area of the plane of focus on a surface of the workpiece 105, which results from a specific illumination wavelength (color) used. The cutout 205 of the workpiece 105 in 3 corresponds to the cutout of the workpiece 2 , except that in 3 a top view of the cutout 205 on the workpiece 105 is shown. More precisely, shows 3 a recorded image of the workpiece 105 or the powder layers 210, the individual powder layers 210 being shown in different hatchings. The workpiece 105 is illuminated, for example, with different wavelengths, so that the different powder layers 210 are shown in different hatchings, depending on which wavelength detects or penetrates which powder layer 210 of the workpiece 105. The wavelength ranges lie between an infrared range and an ultraviolet range. The wavelength ranges are shown as an example on a scale 300.

4 shows a histogram 400 with wavelength ranges to explain the functionality of a device presented here according to an exemplary embodiment. The wavelengths can be, for example, 3 wavelengths shown act. An x-axis 405 represents the pixel wavelengths in percent. A y-axis 410 represents the grayscale value. According to the exemplary embodiment shown here, wavelengths in the ultraviolet range 410, in the blue range 420, in the green range 425, in the yellow range 430, in the red range 435 and in the infrared range 440 are shown.

5a shows a schematic representation of image planes for a specifically used wavelength or layers to explain how a device presented here works according to an exemplary embodiment. These are, for example, individual layers 500 of the derived absolute absorption of a multispectral data cube with copper impurities 515, which contribute to the absorption data for a multispectral overview image, as in 5b is shown to be added. A z-axis 505 represents the wavelengths in millimeters, an x-axis 510 and a y-axis 520 represent the size of the layers 500 in pixels.

5b shows a schematic top view representation of layers 500 to explain the functionality of a device presented here according to an exemplary embodiment, which is at the layers 500 around the summed layers in 5a acts. In 5b For example, material deviations or unevenness are shown in greater detail. At the points with copper impurities 515 the absorption changes and is shown dark.

The x-axis 510 and the y-axis 520 represent the size of the layers 500 in pixels. A scale 525 exemplifies the absolute absorption deviation.

6 shows a flowchart of an exemplary embodiment of a method 600 for operating a device according to an exemplary embodiment. The device corresponds to or is similar to the device from one of the figures described herein.

The method 600 has a step 605 of issuing, a step 610 of activating, a step 615 of detecting and a step 620 of determining. The outputting step 605 is carried out to output the laser light beam from the laser unit to process the workpiece at at least one processing location. The step 610 of activating is carried out to activate the lighting unit to illuminate the workpiece with a light of a first wavelength at an illumination location containing the processing location, to obtain a first light reflected from the workpiece, and to illuminate the workpiece to illuminate the illumination point with a light having a second wavelength that is different from the first wavelength in order to obtain a second light reflected by the workpiece. The detecting step 615 is performed to detect the first and second lights reflected from the workpiece. The determining step 620 is performed to determine a parameter of the workpiece at least at the machining location using a magnitude of the reflected first light and a magnitude of the reflected second light. The parameter can be determined in step 620 of determining, for example, either at the processing point or as an average over a larger image area.

8th shows a flowchart of a second exemplary embodiment of a method 600 for operating a device according to an exemplary embodiment. The device corresponds to or is similar to the device from one of the figures described herein.

The method 600 has a step 610 of activating, a step 615 of detecting and a step 620 of determining. The step 610 of activating is carried out to activate the lighting unit to illuminate the workpiece with a light of a first wavelength at an illumination location containing the processing location, to obtain a first light reflected from the workpiece, and to illuminate the workpiece to illuminate the illumination point with a light having a second wavelength that is different from the first wavelength in order to obtain a second light reflected by the workpiece. The detecting step 615 is performed to detect the first and second lights reflected from the workpiece. The determining step 620 is performed to determine a parameter of the workpiece at least at the machining location using a magnitude of the reflected first light and a magnitude of the reflected second light. The parameter can be determined in step 620 of determining, for example, either at the processing point or as an average over a larger image area. In this exemplary embodiment, the parameter is determined before processing with the laser beam.

In this exemplary embodiment, the output step 605 is carried out only after the parameter has been determined. The output step 605 is carried out to output the laser light beam from the laser unit in order to process the workpiece at at least one processing point.

According to a modification of the first or second exemplary embodiment, step 620 of determining can be followed by a step of calculating a target laser energy from the parameter, with the laser light beam with the calculated target laser energy being output to the processing point. For this purpose, for example, the material that has not yet been processed, for example the powder that has not yet been melted, can be analyzed and only heated in a final step using the laser and melted onto or onto the workpiece.

According to a further modification of the first or second exemplary embodiment, the method can be carried out several times in succession at different processing points.

According to a further exemplary embodiment, in the output step, the light beam can be output with the target laser energy in such a way that a material present, in particular a metal powder, is melted at the processing point. This allows precise control of the required amount of energy, so that errors in the production of the workpiece can be largely avoided.

Finally, according to a further exemplary embodiment, in the step of outputting, the target laser energy can be adjusted by changing an output power of the laser and/or a pulse duration of the laser and/or a number of laser pulses. This allows for quick, flexible and precise adjustment of the required energy output by the laser, ensuring efficient machining or manufacturing of the workpiece.

7 shows a block diagram of an exemplary embodiment of a control device 155 for operating a device. The control device 155 is designed to carry out the method 6 or carry out a similar procedure. The control device 155 has a unit 705 for outputting the laser light beam, a unit 710 for activating the lighting unit, a unit 715 for detecting reflected lights and a unit 720 for determining a parameter. The output unit 705 is designed to carry out and/or control the output step. The unit 710 for activating is designed to carry out and/or control the step of activating. The unit 715 for detecting is designed to carry out and/or control the step of detecting. The unit 720 for determining is designed to carry out and/or control the step of determining.

If an exemplary embodiment includes an “and/or” link between a first feature and a second feature, this should be read as meaning that the exemplary embodiment, according to one embodiment, has both the first feature and the second feature and, according to a further embodiment, either only that first feature or only the second feature.

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 assumes no liability for any errors or omissions.

Cited patent literature

• DE 102016000415 A1 [0002]

Claims (15)

Device (100) for producing and/or processing a workpiece (105), in particular for additively producing a workpiece, the device (100) having the following features: a laser unit (110) configured to emit a laser light beam onto the workpiece (105) to process the workpiece (105); an illumination unit (115) for illuminating the workpiece (105), wherein the illumination unit (115) is designed to illuminate the workpiece (105) with a light of a first wavelength in order to obtain a first light reflected by the workpiece (105). and illuminating the workpiece (105) with a light having a second wavelength different from the first wavelength to obtain a second light reflected from the workpiece (105); and a determination unit (120) for reading in the first and second light reflected by the workpiece (105), the determination unit (120) being designed to determine a parameter of the workpiece (105) using a size of the reflected first light and a size of the reflected to determine the second light. Device (100) according to Claim 1 , wherein the laser unit (110) and the illumination unit (115) are designed to at least partially guide the reflected light beams of the first light and the second light and the laser light beam in a common optical path (140). Device (100) according to one of the preceding claims, wherein the laser unit (110), the illumination unit (115) and/or the determination unit (120) have at least one pivotable mirror (145) and/or the determination unit (120) has a semi-transparent mirror (135 ) having. Device (100) according to one of the preceding claims, wherein the lighting unit (115) is designed to output at least the first light and the second light at the same time and/or at different times and/or wherein the lighting unit (115) has a first Unit (160) for illuminating the workpiece (105) with the first light and a second unit (165) for illuminating the workpiece (105) with the second light. Device (100) according to one of the preceding claims, wherein the determination unit (120) has a camera with interchangeable and/or selectable color filters (130) for filtering light with different wavelengths, in particular six interchangeable and/or selectable color filters. Device (100) according to one of the preceding claims, wherein the determination unit (120) is designed to evaluate an intensity of the first light and the second light as the size of at least the first light and the second light. Device (100) according to one of the preceding claims, wherein the determination unit (120) is designed to use as the parameter of the workpiece (105) a material type of the workpiece (105) and / or a quality of a processing structure of the workpiece (105) produced by the laser light beam ) to evaluate. Device (100) according to one of the preceding claims, wherein the determination unit (120) has a focusing optics unit (120a), wherein a distance of a partial area of the workpiece (105) to the focusing optics unit (120a) is evaluated by evaluating a focal plane of the first light and a focal plane of the second Light can be detected. Device (100) according to Claim 8 , wherein the focusing optics unit (120a) has at least one aspherical lens. Device (100) according to one of the preceding claims, wherein the lighting unit (115) is designed to illuminate the workpiece (105) at least with a light with a third wavelength different from the first wavelength and second wavelength in order to produce a light from the workpiece (105) 105) to obtain reflected third light, in particular wherein the lighting unit (115) is designed to illuminate the workpiece (105) with lights of six wavelengths and wherein the determination unit (120) is designed to illuminate the workpiece (105) reflected to detect the third light in order to determine a parameter of the workpiece (105) using a size of the third light. Method (600) for operating a device (100) for producing and/or processing a workpiece (105), in particular for additively producing a workpiece, the method (600) having the following steps: outputting (605) the laser light beam from the laser unit (110) to machine the workpiece (105) at at least one machining point; Activating (610) an illumination unit (115) to illuminate the workpiece (105) with a light of a first wavelength at an illumination point which contains the processing point in order to produce a first light reflected from the workpiece (105). to obtain light and to illuminate the workpiece (105) at the illumination location with a light having a second wavelength different from the first wavelength to obtain a second light reflected from the workpiece (105); detecting (615) the first and second light reflected from the workpiece (105); and determining (620) a parameter of the workpiece (105), at least at the processing location, using a magnitude of the reflected first light and a magnitude of the reflected second light. Procedure according to Claim 11 , further comprising subsequently after the step (620) of determining a step of calculating a target laser energy from the parameter, wherein the laser light beam with the calculated target laser energy is output to the processing point. Procedure according to Claim 12 , characterized in that in the output step the light beam is output with the target laser energy in such a way that a material present, in particular a metal powder, is melted at the processing point. Procedure according to Claim 13 , characterized in that in the output step the target laser energy is adjusted by changing an output power of the laser and/or a pulse duration of the laser and/or a number of laser pulses. Control device (155), which is set up to carry out the steps of the method (600) according to one of Claims 11 until 14 to be carried out and/or controlled in appropriate units.

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