REGULATION METHOD FOR ADDITIVE MANUFACTURING

Abstract

A regulation method, corresponding device, and computer program product for the additive manufacturing of a component. The method includes: a) acquiring spatially resolved temperature data for a layer built up additively during the manufacture of the component; b) determining at least one region-of-interest on the layer, which is intended to be processed during the manufacture of the component; c) classifying temperature values of the region-of-interest; d) forming an average value of the classified temperature values; and e) controlling a processing device with the formed average value as the input value in order to process the layer.

Claims

1. A regulation method for the additive manufacturing of a component, comprising: a) capturing spatially resolved temperature data relating to an additively constructed layer during the manufacturing of the component, b) determining at least one region of interest of the layer which is intended to be processed during the manufacturing of the component, c) classifying temperature values of the region of interest, d) forming a mean value of the classified temperature values, and e) controlling a processing device with the formed mean value as an input value in order to process the layer, wherein the processing apparatus is an induction heating apparatus for preheating the layer and comprises a regulation system which receives the mean value as an input value.

2. The method as claimed in claim 1, wherein the temperature data are captured by means of an infrared camera or thermographic ally.

3. The method as claimed in claim 1, wherein the temperature data are captured only in a “region of interest” of the layer, and wherein the temperature values are calculated or determined from the temperature data.

4. The method as claimed in claim 1, wherein a histogram of temperature values is created and—for the classification—an absolute or relative class frequency of the temperature values is determined.

5. The method as claimed in claim 1, wherein the largest 10% of the temperature values are classified or selected from the at least one region of interest.

6. The method as claimed in claim 1, wherein temperature values are classified or selected from a range of the largest 10 to the largest 50 values from the at least one region of interest.

7. The method as claimed in claim 1, wherein the mean value of the classified temperature values is an arithmetic mean value.

8. The method as claimed in claim 1, wherein a multiplicity of regions of interest are determined and/or processed in the additive manufacturing of the component.

9. The method as claimed in claim 7, wherein the regulation system continuously regulates the induction heating apparatus.

10. The method as claimed in claim 1, which is a computer-implemented method.

11. An apparatus for controlling a processing device, comprising: means for carrying out the steps of the method as claimed in claim 1, a temperature capture device, a computer, and a regulation device, in particular a PID regulator.

12. The apparatus as claimed in claim 11, which is part of an additive manufacturing system.

13. A non-transitory computer readable media, comprising: instructions which, when executed by a computer, cause the computer to carry out the method as claimed in claim 1.

14. A method for the additive manufacturing of a component, comprising: layer-by-layer additive construction of the component from a pulverulent base material, wherein, after or during the solidification of a powder layer by an energy beam, this layer is processed with the processing device using the method as claimed in claim 1.

15. The apparatus as claimed in claim 11, wherein the apparatus comprises an inductive heating device.

16. The apparatus as claimed in claim 12, wherein the additive manufacturing system comprises a system for powder-bed-based additive manufacturing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1 shows a schematic sectional view of a component during its additive manufacturing.

[0059] FIG. 2 shows a schematic plan view of a component cross section which is processed with a processing device.

[0060] FIG. 3 indicates, by way of example, a histogram of captured temperature values of a layer, which is greatly simplified for the sake of clarity.

[0061] FIG. 4 uses a schematic plan view of a solidified component layer to indicate a sequence of a plurality of processing steps.

[0062] FIG. 5 shows a simplified flowchart for illustrating method steps of the method described.

DETAILED DESCRIPTION OF INVENTION

[0063] In the exemplary embodiments and figures, identical or identically acting elements can each be provided with the same reference signs. The elements shown and their proportions to one another are fundamentally not to be regarded as true to scale; rather, individual elements can be shown exaggeratedly thick or with large dimensions for better presentability and/or for better understanding.

[0064] FIG. 1 uses a schematic sectional view to indicate the additive manufacturing of a component 10 from a powder bed, advantageously by means of selective laser melting or electron beam melting. A corresponding additive manufacturing system is identified with the reference sign 200.

[0065] A starting or base material B for the component 10 is selectively irradiated and solidified in layers by an energy beam, advantageously a laser beam 105, in accordance with the desired (predetermined) geometry. For this purpose, the component is manufactured on a substrate or a construction platform 12 or welded to it.

[0066] The platform 12 simultaneously serves as a mechanical support during manufacturing in order to protect the component from thermal distortion. After the solidification of each layer, a manufacturing surface (not explicitly identified) is newly coated with powder B, advantageously by a coater 11, and the component is constructed further in this way. Layers 1 and 2 are indicated by dashed lines in FIG. 1 merely by way of example, the layer thickness of which in such processes is usually between 20 and 80 μm.

[0067] The component 10 is advantageously a component which is used in the hot gas path of a turbomachine, for example a gas turbine. In particular, the component can be a rotor or guide blade, a segment or ring segment, a burner part or a burner tip, a frame, a shield, a heat shield, a nozzle, a seal, a filter, an orifice or lance, a resonator, a stamp or an agitator, or a corresponding transition, insert, or a corresponding retrofit part. Accordingly, the component 10 is advantageously a component that is thermally and/or mechanically highly stressed in its intended operation and is made of a superalloy, for example a cobalt-based or nickel-based superalloy.

[0068] A processing device 20 is also indicated on the right-hand side of a manufacturing surface (on the right in the figure). The processing device 20 can be used to expediently be pretreat and/or post-treat a newly applied powder layer or a freshly solidified or irradiated component layer. This processing is particularly advantageous or expedient in order to carry out an advantageous or necessary heat treatment (heat management) of the corresponding components, advantageously in-situ and/or during construction.

[0069] The large process-inherent temperature gradients in powder-bed-based processes often exceed 10.sup.4 K/s and accordingly cause high chemical imbalances, cracks and/or mechanical stresses. It is therefore expedient, for example, to thermally process a newly applied powder layer (see reference sign 2) or an already fully solidified component layer (see reference sign 1) with a processing device (see reference sign 20).

[0070] The means described in the present case for the processing or the processing device 20 are advantageously suitable for heating a processing or preheating of the component 10 or a component layer 2 to be subsequently manufactured to a temperature of over 1000° C.

[0071] FIG. 2 shows a schematic plan view of a layer 1 freshly irradiated with the energy beam 105 and solidified. As in FIG. 1, a coater 11 or a coating device 11 can be seen here, which is configured to apply new powder B for a layer to be subsequently irradiated (see reference sign 2 in FIG. 1). The coater 11 is advantageously movable in the X direction along a construction surface and can be moved back and forth to apply new powder B in order to distribute powder, for example from a powder supply (also not explicitly identified), on a manufacturing surface.

[0072] According to the illustration in FIG. 2, the cross section of the component 10 is only shown in a rectangular shape for the sake of clarity. In the case of components for which additive manufacturing is offered or worthwhile, this is of course often not the case, and the component cross section can have a complicated geometry, for example a geometry which is not closed or has cavities.

[0073] In contrast to FIG. 1, according to the present invention, it is possible to see a processing device 20 which advantageously comprises or represents an inductive heating device. Alternatively, the processing device can introduce heat into a component layer using a different principle, for example.

[0074] A conventional additive manufacturing system (see reference sign 200 in FIG. 1) advantageously comprises a temperature capture device 101, advantageously an infrared camera, which can be used to record, for example for each irradiated layer, a complete temperature image of the layer or of the manufacturing surface. An item of image information relating to a pixel (see FIG. 2) from the temperature image can, for example, be converted into a temperature value via calibration and can be evaluated at corresponding positions of later processing (see FIG. 3 further below).

[0075] Via a computer 102 or a data processing device and advantageously also a regulation device 103, captured temperature data, advantageously said temperature or thermal image of the layer 1, can be stored and transferred to the processing device 20 or this can be controlled accordingly.

[0076] An apparatus 100 can accordingly be configured to control the processing device 20 and can also comprise said computer program means (see reference sign CPP further below), the temperature capture device 101, the computer 102 and, for example, the regulation device 103. Accordingly, the apparatus 100 can be coupled or connected to the processing device 20.

[0077] In the embodiment shown in FIG. 2, the processing device 20 has an inductive heating device or an induction coil 104. Although this is not explicitly shown, the device 20 can also have a plurality of induction coils, for example a coil arranged displaceably or movably along the X direction and a coil arranged displaceably or movably along the Y direction. The coils mentioned can also be superimposed in such a way and without disruption or independently of one another that desired or predefined heating, for example heating of over 1000° C., can be achieved only in a selected region (cf. “region of interest” and reference sign ROI).

[0078] The “region of interest”, which is shown by way of example on the left in FIG. 2, can also correspond to the region of a “coil eye” and can thus represent a region in which particularly precise temperature monitoring and regulation is required in order to achieve an advantageous structure of the layer 1 or of the component 10. The region ROI is divided into a multiplicity (approx. 80) of pixels P in FIG. 2 by means of grid lines. This division is still only an example. In a real application of the described method or the described apparatus, the region of interest can comprise several hundred temperature values, for example 200, 300, 400 or 500 temperature values; or this number of values can be captured therein by the temperature capture device 101.

[0079] According to the present invention, temperature data or temperature values T of the layer 1 are correspondingly captured and/or stored in a spatially resolved manner by the temperature capture device 101.

[0080] The region of interest can be determined, for example, by (predefined) positions or position data of the processing device, more precisely of the induction coil 104 or its “eye”.

[0081] Instead of, for example, carrying a pyrometer for capturing the temperature of or processing the layer 1 to a multiplicity of positions (see FIG. 4 further below) and aiming it at a fixed point within the coil eye and capturing the temperature there merely at a point pyrometrically, as is customary in the prior art, temperature values of the region of interest are now classified according to the present invention. This can be done in a similar way to the construction of a histogram (see FIG. 3 further below).

[0082] Corresponding temperature values or pixels P, in particular, are captured on the basis of the temperature image captured by the temperature capture device. This can be done by means of calibration or corresponding conversion of image data into temperature values. The captured temperature values T in the region of interest are now classified, advantageously automatically or in a computer-implemented manner, based on the required regulation quality and efficiency.

[0083] For expedient temperature regulation in the context described, it is furthermore most expedient to provide a reliable value or mean value for a maximum temperature within the region of interest. Therefore, in one advantageous configuration of the present invention (see also FIGS. 3, 4 and 5 further below), the 10% of the captured temperature values which are the largest in terms of absolute value are classified or used for further regulation. Alternatively, for example, it is also possible to select the 10, 20, 30, 40 or 50 values which are the largest in terms of absolute value or other values from the region of interest, for example the 25 largest temperature values.

[0084] For the sake of simplicity, only one coil 104, which can heat a region ROI to be selected in a predefined manner, is identified in FIG. 2. The coil 104 is arranged to be movable and displaceable along the X direction. In the same way, it is possible to provide a similar coil so as to be movable along the Y direction, such that the selected region ROI can be heated in a focused and expedient manner by both coils.

[0085] The processing device 20 is also advantageously configured to be moved, through its movability, over any positions above the powder bed or the layer surface in such a way that both an already solidified component layer (see layer 1) and a layer of newly applied base material or powder (see layer 2) can be heated. In contrast to the solid component structure, however, heating of the powder (see on the left in FIG. 2) is negligible, and the heating power absorbed is dominated by the already solidified layers at the bottom. In the SLM method, these layers are generally significantly thinner than the penetration depth of the induction field or the magnetic flux of the coil(s) 104 that induces the eddy currents.

[0086] FIG. 3 shows a schematic, simplified histogram with classified temperature values of the layer 1 or of the component 10.

[0087] Temperature values T, which advantageously correspond to captured temperatures or temperature values from the region of interest (see FIG. 2), are plotted on the abscissa.

[0088] In particular, six temperature classes are classified or divided by way of example and in a simplified manner; a first temperature class between T1 and T2, a second temperature class between T2 and T3, a third temperature class between T3 and T4, a fourth temperature class between T4 and T5, a fifth temperature class between T5 and T6 and a sixth temperature class between T6 and T7. It is also shown by way of example that the class widths (compare, for example, b1 for the first temperature class and b2 for the second temperature class) of the second, third, fourth and fifth temperature classes are the same and are half as large as the class widths of the first and sixth temperature classes.

[0089] In the present case, the different class widths can be, for example, only one or more tenths of a degree Celsius.

[0090] The area of the rectangles (compare, for example, a1 for the first temperature class and a2 for the second temperature class), which respectively denotes the relative or absolute class frequency, corresponds to the product of the respective class width b.sub.n and the frequency density ρ. Correspondingly, the frequency density ρ is plotted on the ordinate of the histogram.

[0091] The class frequency reflects either an absolute or a relative value. The absolute value corresponds to the number of values that belong to a class. The relative value, on the other hand, expresses what percentage of the values belong to a class.

[0092] As indicated above with reference to the description of FIG. 2, the 10% of the temperature values which are the largest (in terms of absolute value) and are captured from at least one region of interest in each case can be used to form the mean value, for example. Alternatively or additionally, the 10, 20, 30, 40 or 50 absolute values which are the largest (in terms of absolute value), advantageously the 25 largest values, can also be used, for example. Accordingly, the temperature values of the sixth temperature class (with class frequency a6) of the histogram have a greater significance for the present application of the regulation method than, for example, the temperature values of temperature class 1 of class frequency a1. For a different application or the same application, however, further temperature classes can also represent a valuable input for the temperature regulation in order to optimize the processing of the layer or the component 10 during manufacture.

[0093] The captured temperature data can be divided or classified, for example, by means of machine optimization methods, for example representing or comprising artificial neural networks or genetic or evolutionary algorithms.

[0094] According to the present invention, a mean value, advantageously the arithmetic mean value, of the classified temperature values is now formed. This value can then be used to subsequently control or regulate the processing device 20 as an actual or input value, for example in order to process the layer 1 (see FIG. 1). Advantageously, the use of the mean value of the classified values makes it possible to provide a robust and accurate regulation system which has a significantly improved noise behavior (increased signal-to-noise ratio) than, for example, when evaluating an individual pixel with a pyrometer, which, as indicated above, evaluates only a measurement spot within the region of interest, for example.

[0095] The noise can be reduced by transmitting or capturing an item of information multiple times. Since noise occurs stochastically, the standard deviation of the noise signal, for example, also increases only by the factor √{square root over (n)} when n transmissions are added, whereas the signal increases by the factor n. The signal-to-noise ratio related to the signal amplitude increases by √{square root over (n)}.

[0096] FIG. 4 shows, on the basis of a representation similar to the representation in FIG. 2, a sequence of processing steps, on the basis of which a solidified component layer 1 is processed, advantageously inductively heated, advantageously immediately, after solidification by means of the processing device 20 described. According to the invention, the processing device 20 is therefore advantageously regulated or controlled with the mean value formed as the input value.

[0097] The mean value can accordingly denote an actual value for a PID regulator which can function as a regulation device 103. The regulation device, for example having a PI, PD or PID regulator, can be configured using software and hardware, for example, and can be executed on the computer 102 or another programmable device, for example.

[0098] For example, a heat treatment tailored to the alloy of the component may be necessary or advantageous, for example, in order to relieve tension in the component, avoid or prevent hot cracks or to prevent large process-inherent temperature gradients which in turn prevent cracks, chemical imbalances or, in principle, weldability of the base material.

[0099] The corresponding processing regions (compare ROI at positions P1, P2 and P3 in FIG. 3) can be, for example, those positions which are also irradiated one after the other according to an irradiation strategy. Alternatively, they may be specially selected regions, for example regions in the layer which are particularly susceptible to structural defects or other factors, for example strength-related factors. The positions can also—unlike in FIG. 3—merge continuously or steadily into one another.

[0100] Typically, after processing a first position P1, the coil 104 or the processing device 20 is moved to a subsequent second position P2 and/or to a subsequent third position P3, which then indicates a not yet heated or cold point, and can be processed, for example, in a corresponding ROI of the position. Instead of three positions and/or ROIs, as indicated in FIG. 3, in reality, for example, several hundred or thousand positions can be approached and/or processed per layer.

[0101] The temperature capture device 101, like the processing device 20, can be concomitantly moved from one position to the next in this case. However, this is not absolutely necessary. With suitable positioning, only a single temperature image of the layer can also be sufficient to successfully carry out the processing on the basis of the captured temperature values. The region of interest can then be shifted from a first position to a further or second position, for example simultaneously with the movement of the processing device 20, using data, software or program technology, for example, during the additive manufacturing of the component. In other words, only a corresponding measurement region can accordingly be shifted (virtually).

[0102] According to the present invention, the temperature data, as described above, are stored and/or captured at different positions of the additively constructed layer 1, advantageously in the determined regions of interest ROI (compare method steps a) and b) further below); rather than, for instance, within the entire recorded temperature image. Furthermore, the temperature values can be stored and/or captured during the processing of the layer, for example along the positions P1 to P3 as a function of the position or per ROI.

[0103] The regulation of the temperature or the processing of the layer 1 with the processing device 20 can still be carried out quasi-continuously in the present case. In particular, a dense sequence of images from the infrared camera, which can capture for example data or images at 50 Hz, can be used for quasi-continuous or time-dependent regulation; and this per region of interest and for each additively constructed layer or layer to be additively constructed.

[0104] FIG. 5 shows a schematic flowchart which indicates that method steps of the described method can be carried out, for example, individually or cumulatively according to the present invention by a computer program or in a computer-implemented manner. In particular, the steps of determining the region of interest b), classifying the temperature values c), forming the mean value d) and controlling e) can be carried out using program technology. This is indicated in FIG. 5 by the computer program product CPP. The computer program product or computer program can also be part of the apparatus 100 which in turn can be coupled to the processing device 20 and/or to the additive manufacturing system 200 or connected to it. Furthermore, the computer program product CPP can possibly be read into a processor or a computer of the manufacturing system 200.

[0105] The invention is not restricted by the description based on the exemplary embodiments to these exemplary embodiments, but rather encompasses any new feature and any combination of features. This includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.