EP3160681A1

EP3160681A1 - Method and device for the quality assurance of at least one component during the production thereof by a generative production process

Info

Publication number: EP3160681A1
Application number: EP15733608.2A
Authority: EP
Inventors: Günter Zenzinger; Thomas Hess; Joachim Bamberg; Alexander Ladewig
Original assignee: MTU Aero Engines AG
Current assignee: MTU Aero Engines AG
Priority date: 2014-06-26
Filing date: 2015-04-29
Publication date: 2017-05-03
Also published as: WO2015197038A1; DE102014212246B3; US20170136574A1

Abstract

The invention relates to a method for the quality assurance of at least one component (14) during the production thereof, wherein the production takes place by means of at least one additive manufacturing process, which comprises the following steps: building up the component (14) layer by layer, and thermographically recording at least one image of each individual layer applied. In order to facilitate nondestructive crack detection of a metallic component (14) during the production process (inspection by means of an online process), at least some of the layers applied are subjected to a controlled heat treatment below the melting temperature of the material of the component before the thermographic recording of the associated image, wherein the heat treatment causes the last layer applied to radiate heat which, if at least one crack in the layer develops, exhibits a characteristic heat profile at the crack, wherein the heat profile, and consequently the crack, is made visible by means of the associated thermographic recording. Preferably, each layer applied is subjected to such a treatment.

Description

METHOD AND DEVICE FOR QUALITY ASSURANCE OF AT LEAST ONE COMPONENT DURING THEIR MANUFACTURE THROUGH GENERATIVE MANUFACTURING PROCESS

description

The invention relates to a method for quality assurance of at least one component during its production according to the preamble of patent claim 1 and an apparatus for carrying out the method.

Laser thermography methods are known from the prior art which are used as non-destructive testing methods (ZFP methods) for detecting cracks in components. Here, the cooling of the surface of the component to be tested is recorded with a laser thermography camera. However, this is associated with limitations, since the component to be tested must be housed for laser safety reasons. Due to the high energy of the laser, there is a considerable heating of the surface of the component to be tested. For the examination of the component, the manufacturing process must be interrupted in a generative manufacturing process. For the heating of the component, a second energy source is required.

The invention is therefore based on the object to provide a method that allows a non-destructive crack test of a metallic component during the manufacturing process (testing by means of an online method) in a generative manufacturing process.

This object is achieved by a method according to claim 1. Furthermore, the object is achieved with a device according to claim 8. Advantageous embodiments of the invention are contained in the subclaims.

According to the invention, the object is achieved in a method for quality assurance of at least one component during its production, the production taking place by means of at least one additive manufacturing method, comprising the following steps:

- layered structure of the component,

thermographing at least one image of each individual layer applied. At least some of the applied layers are subjected before the thermografi recording of the associated image of a controlled heat treatment below the melting temperature of the component material, wherein the heat treatment emanating from the last layer applied thermal radiation causes the occurrence of at least one crack in the layer a characteristic heat history Having crack, wherein the heat history and thus the crack is made visible by means of the associated thermographic recording. A characteristic heat profile at the crack is understood to mean a heat distribution, which arises in particular due to the interruption of the material at the crack. The thermography device is in particular a laser-free or laser-independent thermography device in which no heating of the component takes place by the thermography device.

As a result, it is possible to test the respectively last-produced layer of a component during production during additive production. This results in a test in the form of an on-line method by means of which the entire component can be examined for cracks during production or production and completely documented. Preferably, each individual layer is subjected to such a treatment.

With the method according to the invention, it is thus possible to carry out a crack test using an online method without significant additional effort. Internal cracks can be detected non-destructively so that aerospace approval of the component is possible without downstream tests.

In an advantageous embodiment of the invention, the controlled heat treatment generates heat radiation in the layer, which lies in the infrared region at the edge of the visible spectrum and in the detection spectrum of a thermography device. It is thus carried out a reduced heat input, which raises the temperature in the layer locally to a level at which heat radiation in the near infrared is emitted, without causing re-melting occurs. However, the heat radiation comes so close to the edge of the visible spectrum that a high-resolution thermography device can detect the heat distribution. In a specific embodiment, at least one energy source required for the additive manufacturing process, in particular a laser, effects the heat treatment. In this case, no further energy source is required except the energy source for the generative manufacturing process. In an alternative embodiment, at least one energy source effects the heat treatment, which is independent of the generative manufacturing process. In this alternative, a division of the functions of the generative manufacturing process and the heat treatment takes place. As a result, an existing device can be easily retrofitted without online crack detection.

In addition, the additive manufacturing process may be a selective laser melting and / or a selective laser sintering. These methods are particularly well suited for the additive production of metallic components. According to an advantageous development of the invention, the crack is corrected by reflowing the cracked layer. Thus, the quality of the layer is not only tested, but also secured or guaranteed.

In a further improved embodiment of the invention, the images recorded by the thermography device are analyzed and, upon detection of the crack, a signaling device is activated and / or a remelting of the cracked layer is triggered. These method steps can be purely manual, fully automatic or partially automatic or partially manual. The activation of the signaling device may alert an operator when a crack is detected. The operator can then interrupt the generative production of the component and set the energy source for the generative manufacturing process so that the cracked layer is remelted again. Alternatively, the remelting of the cracked layer can be triggered automatically. In addition, an alarm signal can be generated.

Furthermore, the solution of the object in an apparatus for carrying out the method with at least one additive manufacturing device and at least one thermogravure fieeinrichtung, characterized in that the device comprises at least one energy source, by means of which the controlled heat treatment of each individual layer is feasible. The energy source must be specially designed for it to perform the controlled heat treatment. This feature enables quality assurance. In an advantageous embodiment of the invention, the energy source of the generative manufacturing device is at the same time the energy source for the controlled heat treatment. For example, can be used for the heat treatment of the already existing in the generative manufacturing device laser, so that a further energy source is not required. This achieves a thermography test without additional integration of further energy sources and recording systems in the generative manufacturing facility.

In an alternative embodiment of the invention, the energy source of the generative manufacturing device is independent of the energy source for the controlled heat treatment. This makes the easy retrofitting of existing systems possible.

In a further preferred development of the invention, the thermography device comprises a high-resolution image recording device and / or an image recording device sensitive to infrared rays, which is based in particular on CCD, CMOS or sCMOS sensors. Such image pickup devices are well suited for thermographic recording. This achieves a fast, extremely high-resolution thermography test with all the advantages of this test technique.

In addition, during the test, the component may be arranged without housing in the generative manufacturing device. This only allows the execution of the component inspection in an online process. In the laser thermography known from the prior art, the component to be tested must be housed for laser safety reasons. In addition, the high laser energy leads to an uncontrolled and undesired strong heating of the test surface. In particular, the device comprises at least one display device, at least one

Evaluation device, at least one signaling device for reporting a crack and at least at least one control of the power source of the generative manufacturing device. The recordings recorded by the thermography device can be displayed optically on the display device. The evaluation device is used for data processing. The signaling device may alert an operator when a crack is detected. The operator can then interrupt the generative production of the component and control the energy source for the generative manufacturing process in such a way that the cracked layer is remelted again. Alternatively, the remelting of the layer by means of the control of the energy source for the generative manufacturing process can be triggered automatically by the evaluation device. In addition, the signaling device can be activated. In the following an embodiment of the invention will be explained in more detail with reference to five greatly simplified figures. Show it:

1 is a perspective view of a detail of a device according to the invention, Fig. 2 is a schematic side view of the device according to the invention shown in FIG. 1,

3 shows a thermographic image of the respective uppermost layer of several components during the implementation of the method according to the invention, FIG. 4 shows a perspective enlargement of the detail IV and FIG

Fig. 5 is a schematic diagram of the device according to the invention.

1 shows a perspective view of a section of a device 10 according to the invention, which comprises a generative production device 12 for producing a component 14. Fig. 1 will be explained below in conjunction with Fig. 2, in which a schematic side view of the device 10 according to the invention shown in FIG. 1 is shown. The device 10 serves to carry out a method for quality assurance of a component 14 during its manufacture. In the present case, the generative production device 12 itself is designed as a selective laser melting system (SLM) known per se, ie a laser 22 is the energy source for the melting process. The laser is directed downwards, so that the component 14 can be produced from the bottom to the top in layers to be applied one above the other. A thermography device 18 is arranged outside a construction space 16 (FIG. 2) of the generative production device 12 and serves to detect a heat development in the uppermost layer of the component 14 during its production. The thermography device 18 is directed onto the respectively uppermost layer of the component 14, wherein the detection angle of the thermography device 18 covers the installation space 16 so that the entire uppermost layer of the component 14 can be detected. For this purpose, the thermography device is arranged in a vertical plane, which in this case corresponds to the image plane in FIG. 2, between the laser 22 and the outer boundaries of the installation space 16. As a result, an optical distortion that might arise in a too inclined thermography device avoided. Between the installation space 16 (FIG. 2) and the thermography device 18, a laser protection glass 20 (FIG. 1) is arranged in order to prevent damage to a sCMOS sensor of the camera by a laser 22 of the generative production device 12. The thermography device 18 is thus located above the installation space 16 and outside the beam path II of the laser 22 of the generative production device 12. This ensures that the thermography device 18 is not located in the beam path II and that the laser 22 accordingly no energy losses through optical elements like semitransparent mirrors, grids or the like. Furthermore, the thermography device 18 does not affect the manufacturing process of the component 14 and is also easily replaceable or retrofittable. The thermography device 18 here comprises an IR-sensitive sMOS camera with 5.5 megapixels and a refresh rate of 100 Hz. Although other sensor types, black-and-white cameras or the like can be used in principle, a color sensor or a sensor with a broad spectral range provides comparatively more information, which allows a correspondingly more accurate assessment of the uppermost layer of the component 14. To produce the component 14, thin powder layers of a high-temperature-resistant metal alloy are applied in a manner known per se to a platform (not shown) of the generative production device 12, locally melted by means of the laser 22 and solidified by cooling. Subsequently, the platform is lowered, applied a further powder layer and solidified again. This cycle is repeated until the component 14 is produced. An exemplary component 14 consists of up to 2000 component layers and has a total layer height of 40 mm. The finished component 14 can then be further processed or used immediately.

In the method according to the invention, the respectively uppermost layer of the component 14 is subjected to a heat treatment below the melting temperature of the component material. This heat treatment causes thermal radiation emanating from the uppermost layer, which can be detected by means of a thermography device 18. The heat radiation of the uppermost layer is adjusted so that it lies in the infrared region at the edge of the visible spectrum and also in the sensitivity range of the thermography device 18.

The energy source, e.g. The heat generated in the uppermost layer of the component 14 by the laser 22 or an additional energy source is determined in the form of a slice image 24 (see FIG. The heat profile in the uppermost layer of the component 14 and optionally further information derived therefrom is subsequently visualized in a spatially resolved manner and coded, for example, via brightness values and / or colors by means of a display device 32 (FIG. 5).

During the examination of the component 14, this is arranged without an enclosure in the generative production device 12. An enclosure is not necessary because the thermography device 18 has no influence on the heat flow in the component 14 either during the additive production or during the examination of the component 14.

The optical thermography not only provides geometric information, but also information about the local temperature distribution in the relevant component layer. It can be provided in principle that the layer image 24 is composed of several individual images. For example, the layer image 24 depending on the surface of the space 16 be composed of up to 1000 individual images or more per component layer or from individual images, each of which between 0, 1 cm 2 and 1, 0 cm of the individual component layer image. The exposure time per image is required between 1 ms and 5000 ms, preferably between 50 ms and 500 ms. In principle, it can be provided that the distance covered by the laser beam per individual image is between 10 mm and 120 mm, for example 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 1 10 mm or 120 mm. Furthermore, it can in principle be provided that each layer image 24 is determined within 2 minutes in order to avoid excessive cooling of the component layers and a concomitant loss of information.

3 shows, by way of example, a layer image 24 of a plurality of components 14, which are produced together in the installation space 16 of the production device 12 and are represented here as rotor blades for an aircraft engine, which are constructed in layers in a direction perpendicular to their longitudinal extent. The layer image can be displayed, for example, on at least one display device 32 (FIG. 5). It can be seen that the layer image 24 images the entire space 16 without overlapping. From each component 14 as many detail sections can be increased. The maximum magnification of the detail sections depends on the resolution of the thermography device 18.

With the reference numeral III, a detail and the associated enlargement of this detail of one of the components 14 are characterized, wherein the corresponding component 14 has a schematically illustrated crack 30 in its uppermost layer. The crack 30 may be a hot crack or a segmentation crack. The reference numeral IV denotes a special section of the detail III, wherein the cutout IV includes the crack 30.

4 shows an additional enlargement of the section IV in a schematic perspective detail view. By way of example, three layers 26, 28 of the component 14 are shown here. However, the component 14 may also include more or fewer layers 26 depending on the current manufacturing state. The two layers 26 shown here are crack-free layers whose cracks are detected by means of the thermography device 18 could, so that the manufacturing process was continued. The uppermost layer of the component 14 is a cracked layer 28.

The course and the shape of the crack 30 are shown here only schematically. In the layer 28, more than one crack 30 may occur. The crack can take any random form. The length and width of the crack 30 may vary and be in the range of a few microns. These small dimensions can only be detected by means of the thermography device 18. In addition, cracks 30 of this magnitude can only be brought into the optical detection range of the thermography device by the corresponding heat treatment described above.

If the length and / or the maximum width of the crack 30 fall below certain limit values, the generative production can be continued. However, if the limits are reached or exceeded, the manufacturing process for the corresponding component 14 is prematurely terminated or the cracked layer 28 of the component 14 is corrected by reflow.

According to FIG. 5, each layer 26, 28 is optically detected by means of the thermography device 18 and displayed on the display device 32. In addition, the thermography device is in operative connection with at least one evaluation device 34 so that the recorded images can be sorted and stored there and, if necessary, an instruction for interrupting the generative production process of one or more components 14 having cracks can be triggered. The evaluation device 34 is configured such that it can detect the crack 30 in the uppermost layer 28 of the component 14 with the aid of an algorithm. However, these processes can also be carried out manually by evaluating the images or images of the thermography device 18 on the pointing device 32 by an operator.

If it is detected with the aid of the thermography device 18 and the evaluation device 34 that the layer 28 of the component 14 is subject to cracking, the generative production process can be interrupted and the cracked layer 28 corrected by reflowing. The remelting of the cracked layer 28 takes place, for example, in that the

Evaluation device 34 upon automatic detection of a crack 30 of the controller 38 of the Sers 22 gives a corresponding command for interrupting the generative manufacturing process and remelting.

Alternatively, the generative manufacturing process for a single or multiple cracked components 14 may be terminated prematurely. This is done by a command, which is triggered manually or by the evaluation device 34, to the controller 38 of the laser 22.

The premature termination of the generative manufacturing process is preferably carried out when the component 14 has only a small number of layers 26, 28. If the component 14 is already almost finished, the interruption and re-melting of the layer 28 is preferred.

Quite generally, the evaluation device 34 can also trigger an alarm in the form of acoustic or optical signals by means of a signal device 36, e.g. in the form of a warning message on the display device 32 or another computing device (not shown) connected to the generative manufacturing device 12. Then it can be decided by an operator whether and how the generative production of the components 14 is continued.

The evaluation device 34 and the signal device 36 including the required signal lines between the thermography device 18, the evaluation device, the signal device 36 and the controller 38 of the laser 22 generative manufacturing device 12 are components of the device 10th

The invention relates to a method for quality assurance of at least one component during its production, wherein the production takes place by means of at least one additive manufacturing method, comprising the following steps:

- layered structure of the component,

thermographing at least one image of each individual layer applied. In order to enable a non-destructive crack test of a metallic component during the manufacturing process (testing by means of an on-line method), at least some of the applied layers are subjected to a controlled heat treatment below the melting temperature of the component material prior to the thermographic recording of the associated image, wherein the heat treatment a heat emanating from the last applied layer Radiation causes the occurrence of at least one crack in the layer has a characteristic heat history at the crack, the heat history and thus the crack is made visible by means of the associated thermographic recording. Preferably, each applied layer is subjected to such a treatment.

LIST OF REFERENCE NUMBERS

10 device

12 Generative production facility

14 component

16 space

18 thermography device

20 laser safety glass

22 lasers

24 layer picture

26 Crack-free layer

28 Cracked layer

30 crack

32 display device

34 evaluation device

36 signaling device

38 control

II beam path of the laser

III detail

IV section

Claims

claims

A method for quality assurance of at least one component (14) during its production, wherein the production takes place by means of at least one additive manufacturing method, comprising the following steps:

layered structure of the component (14),

thermographically taking at least one image of each individual coated layer (26, 28),

characterized in that at least some of the applied layers (26, 28) are subjected to a controlled heat treatment below the melting temperature of the component material before the thermographic image of the associated image, the heat treatment causing a heat radiation emanating from the last applied layer, which at least one occurs Crack (30) in the layer (28) has a characteristic heat profile at the crack (30), wherein the heat history and thus the crack (30) is made visible by means of the associated thermographic recording.

2. The method according to claim 1, characterized in that the controlled heat treatment generates a heat radiation in the layer (26, 28) which lies in the infrared region at the edge of the visible spectrum and in the detection spectrum of a thermography device (18).

3. The method according to claim 1 or 2, characterized in that at least one energy source required for the generative manufacturing process, in particular a laser (22), causes the heat treatment.

4. The method according to claim 1 or 2, characterized in that at least one energy source causes the heat treatment, which is independent of the generative manufacturing process.

5. The method according to any one of claims 1 to 4, characterized in that the additive manufacturing process is a selective laser melting and / or a selective laser sintering.

6. The method according to any one of claims 1 to 5, characterized in that the crack (30) is corrected by reflowing the cracked layer (28).

7. Method according to claim 6, characterized in that the images recorded by the thermography device (18) are analyzed and upon detection of the crack (30) a signal device is activated and / or a remelting of the cracked layer (28) is triggered.

8. Device (10) for quality assurance of at least one component during its manufacture, wherein the production by means of at least one generative manufacturing method, in particular for carrying out the method according to one of claims 1 to 7, with at least one generative manufacturing device (12) and at least one thermography device (18), characterized in that the device (10) comprises at least one energy source (22) by means of which the controlled heat treatment of each individual layer (26, 28) is feasible.

9. Device (10) according to claim 8, characterized in that the energy source (22) of the generative manufacturing device (12) is at the same time the energy source for the controlled heat treatment.

10. Device (10) according to claim 8, characterized in that the energy source (22) of the generative manufacturing device (12) is independent of the energy source for the controlled heat treatment.

11. Device (10) according to one of claims 8 to 10, characterized in that the thermography device (18) comprises a high-resolution image recording device and / or an infrared ray-sensitive image recording device, in particular CCD, CMOS or sCMOS sensors based.

12. The device (10) according to claim 1 1, characterized in that the component (14) during the examination is arranged without a housing in the generative manufacturing device (12).

13. Device (10) according to one of claims 8 to 12, characterized in that the device (10) at least one display device (32), at least one evaluation device (34), at least one signaling device (36) for reporting a crack (30). and at least one controller (38) of the power source of the generative manufacturing device (12).