DE102021105918A1 - Additive repair system - Google Patents

Abstract

The invention relates to an additive repair system (1) and a method for determining correction parameters of a corresponding system (1). The additive repair system (1) comprises a construction platform (2) with a construction volume (3) located above it and a control device ( 5) controlled laser scanner (4) for the selective laser melting of powdered material introduced successively in layers into the construction volume (3) at predetermined coordinates. The construction platform (2) has a plurality of repair positions (6) with receptacles (7) that are accurate in terms of position and position for components (10) to be repaired by applying material. Furthermore, a correction module (8) for transforming predetermined repair geometries (20) for components (10) arranged at individual repair positions (6) using correction parameters determined for the respective repair position (6) before the repair geometries (20) are sent to the control device (5) for controlling the laser scanner (4). The method according to the invention is used to determine the correction parameters as used by the additive repair system (1) according to the invention.

Description

The invention relates to an additive repair system and a method for determining correction parameters of a corresponding system.

Methods and systems for additive manufacturing are known in the prior art, in which successively applied layers of metal powder are selectively remelted by a controlled laser beam according to a specified CAD model to form a solid material after solidification ("selective laser melting"; SLM). After all layers have been processed accordingly, the non-remelted powder can be removed and a metal component remains, which has to be reworked if necessary or can be used directly.

The technology of the additive manufacturing process with selective laser melting is also used for the additive repair of components. For this purpose, additional material is applied to existing components using the method described, for example to compensate for missing or worn areas on a component.

In order to be able to carry out corresponding repairs, the exact positioning or at least exact determination of the position of the component to be repaired on the construction platform of the production system is essential. At the same time, the laser system must be precisely calibrated in relation to the component or the construction platform. This is the only way to ensure that the material powder lying directly on the component to be repaired is actually remelted by a laser beam and thus firmly connected to the component to be repaired.

The systems for additive manufacturing have to be calibrated in a complex manner, especially for the repair methods described. For this purpose, the prior art proposes, among other things, to produce a specified calibration body in additive manufacturing at a specified position on a construction platform of the manufacturing system. After completion, the calibration body produced in this way and still on the construction platform is measured immediately, for example using tactile measuring methods. Correction values for a possible displacement or rotation of the coordinates parallel to the construction platform can then be determined from any deviation of the calibration body or its position on the construction platform and the specifications, which can be taken into account directly by the control unit of the laser. The correction values can be checked by repeatedly producing the calibration body, taking into account the previously determined correction values.

It has been shown that with this method, any distortions in the coordinate system of the laser system can often not be determined via the construction platform. In addition, the calibration process is very complex due to the required production of calibration bodies and their subsequent measurement and often requires up to ten working days to carry out. Also, inaccuracies in the measurement, which ultimately lead to an inaccurate calibration, often cannot be completely avoided.

In systems for additive manufacturing processes calibrated according to the state of the art, a corresponding additive repair is usually only possible for a single component arranged centrally on the construction platform, if at all, due to the distortions that cannot be completely avoided when controlling the laser beam. A simultaneous repair of several smaller components, which can be arranged together and at a distance from one another on the construction platform, is regularly not possible, despite the great effort involved in calibrating.

The object of the present invention is to create an additive repair system and a method for its calibration, in which the disadvantages of the prior art no longer occur or only occur to a reduced extent.

This object is achieved by an additive repair system according to the main claim and a method for determining correction parameters of such a repair system according to the independent claim. Advantageous developments are the subject of the dependent claims.

Accordingly, the invention relates to an additive repair system comprising a construction platform with an overlying construction volume and a laser scanner controlled by a control device for selective laser melting of powdery material introduced successively in layers into the construction volume at predetermined coordinates, the construction platform having a plurality of repair positions with positions - and positionally accurate recordings for components to be repaired by applying material and a correction module for the transformation of predetermined repair geometries for components arranged at individual repair positions using correction parameters determined for the respective repair position before the repair geometries are transmitted to the control device for controlling the laser scanner, is provided.

1. a) Anordnen von einem oder mehreren Messsystemen an einer oder mehreren Reparaturpositionen des Reparatursystems zur Erfassung der an der jeweiligen Reparaturposition einfallenden Laserstrahlen;
2. b) Ansteuerung des Laser-Scanners zum gleichzeitigen oder sukzessiven Anstrahlen jeweils eines oder mehrerer vorgegebenen Punkte der Reparaturposition(en), an denen ein Messsystem angeordnet ist;
3. c) Ermittlung der jeweils lokalen Korrekturparameter über das oder die Messsysteme anhand der erfassten einfallenden Laserstrahlen;
4. d) Wiederholung der Schritte (a) bis (c) mit veränderter Anordnung des oder der Messsysteme, bis lokale Korrekturparameter für jede Reparaturposition ermittelt sind; und
5. e) Ablegen der Korrekturparameter im Korrekturmodul.

Furthermore, the invention relates to a method for determining the correction parameters of an inventive appropriate additive repair system, with the steps:

1. a) arranging one or more measuring systems at one or more repair positions of the repair system for detecting the incident laser beams at the respective repair position;
2. b) activation of the laser scanner for the simultaneous or successive irradiation of one or more specified points of the repair position(s) at which a measuring system is arranged;
3. c) determination of the respective local correction parameters via the measuring system or systems based on the detected incident laser beams;
4. d) repeating steps (a) to (c) with a different arrangement of the measuring system or systems until local correction parameters have been determined for each repair position; and
5. e) Storing the correction parameters in the correction module.

For an additive repair of a component, a so-called "repair geometry" is determined from the difference between the actual geometry of the damaged component and the desired geometry after the material application, which reflects the geometry of the material to be applied.

This repair geometry is used in the additive repair system according to the invention, which is fundamentally based on the principle of additive manufacturing processes with selective laser melting, and consequently a laser scanner that can be controlled via a control device for selective laser melting of powdered material successively introduced in layers into a construction volume located above a construction platform specified coordinates, is used to remelt the powdery material at the appropriate points so that the damaged component and the added material gradually result in the desired geometry and the added material is firmly connected to the component. For this it is imperative that the laser scanner implements the repair geometry in the correct position and position in relation to the component to be repaired.

In the additive repair system according to the invention, the construction platform has a plurality of repair positions, at each of which a location-accurate receptacle for a component to be repaired is provided. A recording is "accurate in position and position" if the position and the position or alignment of the component to be arranged at a repair position for repair purposes is specified by the recordings. In this case, a receptacle can be designed in such a way that the position and location of a component inserted therein is immediately and unambiguously obtained. If the component to be repaired is, for example, the turbine blade of an aircraft engine, the receptacle can have a profile for precisely fitting the blade root, via which the position and orientation of the—in this example—turbine blade is clearly and precisely defined. Alternatively, it is possible that the recording allows an adjustment of the position and location of a component inserted therein, the adjustment either to achieve a predetermined position and location - compliance with which is preferably checked by suitable measuring devices - or the actually set adjustment to the later described Correction module is supplied and taken into account there in the transformation of the repair geometry accordingly.

In order to ensure during the additive repair of components at each of the repair positions that the added material is actually accurately and securely connected to the component to be repaired at the desired points, correction parameters are determined according to the invention for each of the repair positions. According to the invention, the specified repair geometries for the individual components arranged at the various repair positions are transformed using the correction parameters determined for the respective repair positions before these transformed repair geometries are then transmitted to the control device of the laser scanner for the final execution of the repair.

The transformation finally converts the coordinate system of the repair geometry oriented on the actual component to be repaired at a repair position into a coordinate system which corresponds to the local coordinate system of the laser scanner for this repair position. In other words, the transformation ensures that a coordinate designating a point on the surface of the real component, after transformation and transmission to the laser scanner, results in a laser beam directed at precisely this point.

The correction module can be designed to rotate, shift and/or distort the repair geometries according to the correction parameters for the purpose of transformation. It is often sufficient if the transformation takes place solely in the plane parallel to the construction platform. Since the application of material to a component to be repaired in the direction perpendicular to the construction platform is largely determined by the thickness of the individual powder layers is determined, there are usually only extremely few possibilities for correction in precisely this direction. At the same time, there is almost never a need for corrections in this direction.

It has also been shown that it is usually sufficient to determine a set of correction parameters for each repair position, which is then applied to the entire repair geometry of the component at the corresponding repair position. Since more than one repair position is provided on the construction platform, the maximum size for components to be repaired is regularly limited in such a way that a set of correction parameters has sufficient accuracy for the respective repair position over the entire component arranged there. Depending on the size and spacing of the individual repair positions, it may be sufficient to determine a set of correction parameters for only part of the repair positions, which is then also used as a correction parameter for the respective directly surrounding repair positions. In this case, correction parameters are determined for a plurality of repair items, which are then also applied to other repair items, so that correction parameters are determined for all repair items.

It is also possible for the correction module to be designed for the spatial interpolation of the correction parameters between two or more repair positions and for the transformation of the repair geometries, taking into account the interpolated correction parameters. Individual correction parameters can then be determined for each point in the construction volume. Since only the correction parameters at the repair positions still have to be determined, the effort involved in determining correction parameters does not increase. However, by appropriate interpolation between the correction parameters determined for the repair position, it is still possible to approximately and regularly compensate for any distortions in the coordinate system of the laser scanner with sufficient accuracy.

To determine the individual repair parameters, a measuring system that can be freely arranged at the individual repair positions can be provided, which determines correction parameters for the respective repair position when the laser scanner illuminates a predetermined point of the repair position. In this case, it is preferred if the measuring system can be fastened to the recording of the repair position in question in a precise position and position. If the measuring system is arranged at a repair position, the laser scanner can be controlled to illuminate one or more specified points at the repair position. By measuring the actual point of impact and/or the angle of incidence of the laser beam for each of the specified points by the measuring system, deviations between the point illuminated by the laser scanner according to the specified coordinates and the actual point, the coordinates of which were transmitted to the laser scanner, can be determined and suitable ones can be determined from this Correction parameters are derived. This process is repeated until correction parameters are available for all repair items. All correction parameters are then stored in the correction module, as described above, used to transform the repair geometry.

Since separate correction parameters are determined for each repair position, an accuracy that is sufficient for the additive repair of components is ensured at each of the repair positions. Since the transformation of the individual repair geometries for each repair position is carried out individually in a correction module, which does not have to be integrated in the control device of the laser scanner, it is possible to use an already existing system for additive manufacturing processes, which only requires a uniform calibration for the entire construction volume provides for further development of a system according to the invention by adding a correction module and the definition of several repair positions on the construction platform.

To explain the method according to the invention for determining the correction parameters, reference is made to the above statements.

• 1: eine schematische Darstellung eines erfindungsgemäßen additiven Reparatursystems;
• 2: eine schematische Darstellung eines erfindungsgemäßen additiven Reparatursystems mit darin eingesetzten Turbinenschaufeln;
• 3a-d: schematische Darstellungen zur Ermittlung einer Reparaturgeometrie für eine Turbinenschaufel;
• 4: schematische Darstellung zur Transformation der Reparaturgeometrie aus 3 gemäß ermittelter Korrekturparameter;
• 5: schematische Darstellung zur Ermittlung von Korrekturparametern; und
• 6 schematische Darstellung der Korrekturparameter sämtlicher Reparaturpositionen des Reparatursystems aus 1 und 2.

The invention will now be described by way of example on the basis of an advantageous embodiment with reference to the accompanying drawings. Show it:

• 1 : a schematic representation of an additive repair system according to the invention;
• 2 : a schematic representation of an additive repair system according to the invention with turbine blades inserted therein;
• 3a-d : schematic representations for determining a repair geometry for a turbine blade;
• 4 : schematic representation of the transformation of the repair geometry 3 according to determined correction parameters;
• 5 : schematic representation for determining correction parameters; and
• 6 schematic representation of the correction parameters of all repair positions of the repair system 1 and 2 .

In 1 and 2 an example of an additive repair system 1 according to the invention is shown schematically. In this example, the repair system 1 is used to repair engine blades 10 that have been damaged by foreign particles and have been reduced to the undamaged base area (cf. 2 ) intended.

The repair system 1 comprises a construction platform 2 as the lower boundary of a construction volume 3. A laser scanner 4 is arranged above the construction platform 2 and the construction volume 3, with which each point in the construction volume 3 can be specifically illuminated. To control the laser scanner 4, a control device 5 connected to it via a data line 9 is provided.

Layers of powdery material (not shown) are successively introduced into the building volume 3 and are selectively remelted with the aid of the laser scanner 4 at the coordinates specified for the respective layer.

In this respect, the system 1 corresponds to a system known from the prior art for additive manufacturing using selective laser melting.

In this exemplary embodiment, a total of nine repair positions 6 are provided on the construction platform 2 . A mount 7 is provided at each of the repair positions 6, to which engine blades 10 can be fastened in a precise position and orientation (cf. 2 ). For this purpose, the receptacles 7 have a profile that fits exactly to the blade roots 11 of the engine blades 10 and into which the engine blades 10 can be pushed.

Also provided is a correction module 8, the functioning of which will be discussed in more detail below. The correction module 8 is designed separately from the control device 5 and is connected to it via a data line 9 . As a result, a system for additive manufacturing using selective laser melting according to the prior art can also be used by providing receptacles 7 on the construction platform 2 and a correction module 8 to form an additive repair system 1 according to the invention, as is shown in 1 and 2 is shown, educate.

In the 2 The engine blades 10 shown are--as explained below--already reduced to their respective non-damaged base area 13 and face the laser scanner 4 with their connection surface 14. With the help of the additive repair system 1 according to the invention, the engine blades 10 are restored to their original shape, rising from the connection surfaces 14 built up. Depending on the design of the repair system 1, it is possible for the individual engine blades 10—as illustrated—to have base regions 13 of different design. However, it can also be advantageous or, depending on the configuration of the repair system 1, possibly even necessary for the connecting surfaces 14 of all engine blades 10 to lie in a common plane. Irrespective of this, a repair geometry 20 must be determined for each of the engine blades 10 .

As in 3 outlined, in a first step an engine blade 10 with damage 12 ( 3a) , which may have been caused, for example, by a particle impacting the engine blade 10 during operation, is reduced to an undamaged base area 13 by machining ( 3b) , which also results in the connection surface 14.

The resulting shape of the blade 10 reduced to the undamaged base area 13, which is recorded, for example, by a 3D scanner, with a digital model 10' of the target shape of the engine blade 10 ( 3c ) matched. The repair geometry 20 ( 3d ).

In the comparison described, both the data recorded by the 3D scanner data and the data of the model 10' are related to a common predetermined coordinate system 21, in which the repair geometry 20 is then also mapped. The repair geometry 20 together with the coordinate system 21 therefore not only specifies the shape of the part of material to be added, but also the exact position and alignment at which point material of the engine blade 10 is to be added.

The repair geometry 20 determined in this way for an engine blade 10 at a specific repair position 6 can then be used to apply material to the engine blade 10 in order to compensate for the damage 12 in question. However, the simple application of the repair geometry 20 to a repair position 6 by the control device 5 does not ensure that the material is actually applied with a precise fit for the damage 12 .

In particular, since a plurality of repair positions 6 are distributed over the construction platform 2, it is not ensured that a calibration of the laser scanner 4 carried out according to the prior art, for example for a central point of the construction platform 2, will have sufficient accuracy for the central point of this Point distant repair position 6 offers.

In 4 is shown schematically as an example of how the repair geometry 20 shown in dashed lines with the associated coordinate system 21 can be subject to deviations when directly implemented by the control device 5 even with a calibrated laser scanner 6, which would ultimately result in an incorrect repair. Even if the deviations in 4 are particularly large for purposes of illustration, even small deviations can lead to a defective connection of the additionally applied material to the engine blade 10 .

According to the invention, the respective repair geometries 20 are transformed with the help of correction parameters determined for the respective repair position 6 in such a way that when the control device 5 converts the coordinate system 21 associated with the respective repair geometry 20 into the actually desired position and alignment, as determined by the coordinate system 21′ indicated and which is ultimately specified by the mount 7, is transformed, with which the repair geometry 20 is then also precisely aligned with the damage 12 of an engine blade 10 inserted into the mount 7 and the material application takes place with a precise fit on the connecting surface 14. In this case, the transformation can include a displacement, rotation and/or distortion of the coordinate system 21 .

To determine which transformations are required at a repair position 6 - i.e. to determine the correction parameters for the corresponding repair position 6 - a measuring system 30, as exemplified in 5 is shown. The measuring system 30 includes a foot 31 with which it can be inserted in the receptacle 7 of that repair position 6 in a precise position and position for which the correction parameters are to be determined. When inserted into a receptacle 7, the measuring system 30 comprises light incidence surfaces 32 facing the laser scanner 4, on which the position of impact of individual laser beams can be determined. The light incidence surfaces 32 can, for example, comprise a large number of light detectors in a matrix arrangement or from an image acquisition chip (CCD or CMOS), possibly with optics arranged in front of them, in order to determine the position of laser beams incident on the light incidence surface 32.

For the measuring system 30, a pattern of points of light 33 is specified in the coordinate system 21 that also forms the basis of the repair geometries 20 (cf. 3 and 4 ). To determine the correction parameters, the laser scanner is instructed via the control device 5 to image precisely this pattern of points of light 33 at the repair position 6, at which the measuring system 30 is arranged. The light points 33'' actually generated on the light entry surface 32 deviate in their position from the specified positions of the light points 33, but allow the determination of a coordinate system 21" associated with the light points 33" actually recorded". From a comparison of the coordinate systems 21' and 21" according to 5 correction parameters can then be derived, which ultimately result in a transformation of the coordinate system 21 4 into the coordinate system 21' specified by the receptacle 7.

The correction parameters can be determined directly by the measuring system 30 . However, it is also possible for the determination on the basis of the information provided by the measuring system 30 regarding the position deviations of the actually recorded light points 33'' from the corresponding specifications 33 to be carried out by any other unit, e.g. the correction module 8 as well. The only important thing is that the correction parameters determined must be sent to the correction module 8 for transformations, such as those associated with 4 explained are available.

The related to 5 The determination of correction parameters described above can be carried out one after the other for each repair position 6 - or if there are sufficient measuring systems 30 also simultaneously for all - repair positions 6, with different correction parameters regularly resulting for each repair position 6, as is shown in 6 is indicated where the coordinate systems 21" (dashed) determined via one or more measuring systems 30 and the coordinate systems 21' specified by the recordings 7 at the respective repair positions are shown schematically in a plan view of the construction platform 2. The coordinate systems 21" shown in dashed lines correspond at the same time the coordinate systems 21 of the repair geometries 20 if they were implemented by the laser scanner 4 without prior transformation.

The transformation of the repair geometries 20 is carried out individually for each repair position 6 by the correction module 5 using the correction parameters determined for the respective repair position. Since this transformation is carried out separately from the actual control device 5 of the laser scanner 4, existing machines for additive manufacturing or repairs can be easily developed into a system according to the invention using selective laser melting. However, it is of course also possible for the correction module 5 to be integrated into the control device.

Claims (10)

Additive repair system (1) comprising a construction platform (2) with a construction volume (3) above it and a laser scanner (4) controlled by a control device (5) for selective laser melting of powdered material successively introduced in layers into the construction volume (3). at predetermined coordinates, characterized in that the construction platform (2) has a plurality of repair positions (6) with positionally and positionally accurate receptacles (7) for components (10) to be repaired by applying material and a correction module (8) for the transformation of predetermined repair geometries (20) for components (10) arranged at individual repair positions (6) using correction parameters determined for the respective repair position (6), before the repair geometries (20) are transmitted to the control device (5) for controlling the laser scanner (4). are provided. repair system after claim 1 , characterized in that the correction module (8) is designed to rotate, shift and/or distort the repair geometries (20) according to the correction parameters for the purpose of transformation. repair system after claim 2 , characterized in that the transformation is limited to the plane parallel to the construction platform (2). Repair system according to one of the preceding claims, characterized in that the correction module (8) is designed for spatial interpolation of the correction parameters between two or more repair positions (6) and for transformation of the repair geometries (20) taking into account the interpolated correction parameters. Repair system according to one of the preceding claims, characterized in that at least one receptacle (7) is designed in such a way that the position and location of a component (10) inserted therein results directly and unambiguously. Repair system according to one of the preceding claims, characterized in that at least one receptacle (7) is designed in such a way that the receptacle allows the position and position of a component (10) inserted therein to be adjusted. Repair system according to one of the preceding claims, characterized in that at least one measuring system (30) to be arranged freely at the individual repair positions is provided, which, when a predetermined point of the repair position (6) is illuminated by the laser scanner (4), corrects parameters for the respective repair position (6) determined. repair system after claim 7 , characterized in that at least one measuring system (30) can be connected to the receptacle (7) at a repair position (6) in a precise position and location. Method for determining the correction parameters of an additive repair system (1) according to one of the preceding claims, having the steps: a) arranging one or more measuring systems (30) at one or more repair positions (6) of the repair system (1); b) activation of the laser scanner (4) for the simultaneous or successive irradiation of one or more specified points (33) at the repair position(s) (6) at which a measuring system (30) is arranged; c) determination of the respective local correction parameters via the measuring system or systems (30) based on the detected incident laser beams (33'); d) repeating steps (a) to (c) with a changed arrangement of the measuring system or systems (30) until local correction parameters have been determined for each repair position (6); and e) Storing the correction parameters in the correction module (8). procedure after claim 9 , characterized in that the arrangement of a measuring system (30) at a repair position (6) includes the position and position-accurate attachment to the receptacle (7) of the repair position (6).

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