Adjustment of turbine engine part

Abstract

The invention relates to a method for adjusting a turbine engine part to be placed in a gas stream of the turbine engine, the part having previously undergone a material addition operation in order to fill in a defect in at least one area of the surface thereof, resulting in an extra thickness in at least one area of the surface thereof, characterised in that the method comprises steps of: - ordering (E1) the formation of a three-dimensional image of the part; - identifying (E2) the at least one area of the surface of the part that includes the extra thickness, and identifying the extra thickness, in the three-dimensional image of the part; - determining (E3) a trajectory of an adjustment tool, as a function of the geometry of the extra thickness identified; and - ordering (E4) the adjustment of the part according to the trajectory determined.

Description

[0001] TURBOMACHINE PART ADJUSTMENT

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention relates generally to the repair of turbomachine parts. More particularly, it relates to the removal of material, or adjustment, carried out after resurfacing of material to repair a turbomachine part.

[0005] STATE OF THE PRIOR ART

[0006] Particular consideration is given to high-pressure turbine parts, including the nozzles that are part of the turbine stator. These parts are formed from nickel superalloy and are subject to very high stresses during flight phases. These parts operate at very high temperatures, up to approximately 1,100°C, and are subject to thermal fatigue stresses.

[0007] These stresses cause wear on these parts, resulting in the formation of cracks on the surface of the parts.

[0008] Crack repair involves resurfacing with material by diffusion brazing to fill the gaps and then removing the excess brazing thickness to restore the part's original aerodynamic profile. Currently, this material removal operation, or adjustment, is carried out manually. It takes approximately one and a half hours per part.

[0009] This operation is therefore time-consuming and can cause significant musculoskeletal disorders among operators.

[0010] FR 3 116 456 describes a method for repairing a turbomachine part in which a worn area of ​​a part, in particular the worn leading edge of a blade of a single-piece bladed disc, is machined. DISCLOSURE OF THE INVENTION

[0011] The invention aims to solve the problems of the prior art by providing a method for adjusting a turbomachine part to be placed in a gas stream of the turbomachine, the part having previously undergone an operation of adding material to fill a defect in at least one area of ​​its surface, resulting in an excess thickness in the at least one area of ​​its surface, characterized in that it comprises steps of:

[0012] - command to form a three-dimensional image of the part,

[0013] - identification of at least one area of ​​the surface of the part including the excess thickness, and identification of the excess thickness, in the three-dimensional image of the part,

[0014] - determination of a trajectory of an adjustment tool, depending on the geometry of the identified excess thickness, and

[0015] - control of adjustment of the part according to the determined trajectory.

[0016] Thanks to the invention, it is possible to automatically generate a material removal trajectory adapted to each part according to the excess thicknesses to be removed. The invention allows adaptation to the variability of the input state of the parts to be adjusted. Indeed, the position of the excess thicknesses on the part is random. Furthermore, the invention makes it possible not to intervene on the healthy material of the part.

[0017] The invention is particularly suitable for parts of complex geometry such as high pressure turbine parts of aircraft engines.

[0018] The invention makes it possible to limit the occurrence of significant musculoskeletal disorders among operators and frees them from time-consuming operations in favor of other operations with higher added value.

[0019] According to a preferred characteristic, the step of identifying at least one area of ​​the surface of the part including the excess thickness, and identifying the excess thickness comprises:

[0020] - a pre-detection of irregularity on the surface of the part, then, in the case of the pre-detection of at least one irregularity, - a filtering of data representing the at least one irregularity to produce zone data in which the data representing the at least one irregularity have been deleted, called healthy zone data,

[0021] - a surface reconstruction performed by a function having a continuous slope, from the healthy area data to produce reconstructed surface data corresponding to a surface without excess thickness,

[0022] - a comparison of the data of the actual surface of the part with the data of the reconstructed surface, and, depending on the result of the comparison, an identification of the excess thickness.

[0023] According to a preferred feature, the three-dimensional image of the part comprises a mesh which represents the actual part composed of mesh elements and the pre-detection of irregularity on the surface of the part comprises the identification of first mesh elements whose curvature exceeds a curvature threshold as irregularities.

[0024] According to a preferred characteristic, the pre-detection of irregularity on the surface of the part further comprises the identification of second mesh elements neighboring the first mesh elements over a predetermined number of rows.

[0025] According to a preferred feature, the function having a continuous slope is defined by a polynomial equation.

[0026] According to a preferred characteristic, the step of identifying at least one area of ​​the surface of the part including the excess thickness, and identifying the excess thickness comprises an adjustment between a model of the part and the three-dimensional image of the part. This characteristic is implemented in the case of a highly curved area, in addition to the characteristics set out previously.

[0027] According to a preferred characteristic, the determination of a trajectory of an adjustment tool comprises the comparison of a predetermined trajectory with the coordinates of the points of the identified excess thickness, so as to retain only the points of the programmed trajectory whose distance from the points of the defect is less than a comparison threshold. According to a preferred characteristic, the adjustment command of the part according to the determined trajectory comprises a detection of a first contact of the tool with the excess thickness and the command of the tool so that it carries out a progressive descent in successive passes.

[0028] The invention also relates to a system for adjusting a turbomachine part to be placed in a gas stream of the turbomachine, the part having previously undergone an operation of adding material to fill a defect in at least one area of ​​its surface, resulting in an excess thickness in the at least one area of ​​its surface, the adjustment system comprising a three-dimensional measuring device and an adjustment machine, the adjustment system being characterized in that it comprises a control module capable of:

[0029] - control the three-dimensional measuring device to form a three-dimensional image of the part,

[0030] - identify at least one area of ​​the surface of the part including the excess thickness, and identify the excess thickness, in the three-dimensional image of the part,

[0031] - determine a trajectory of an adjustment tool, based on the geometry of the identified excess thickness, and

[0032] - control the adjustment machine to adjust the part according to the determined trajectory.

[0033] The system has advantages similar to those previously presented.

[0034] In a particular embodiment, the steps of the method according to the invention are implemented by computer program instructions.

[0035] Consequently, the invention also relates to a computer program on an information medium, this program being capable of being implemented in a computer, this program comprising instructions adapted to the implementation of the steps of a method as described above.

[0036] The invention also relates to a computer-readable information medium, and comprising computer program instructions adapted to the implementation of the steps of a method as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other characteristics and advantages will appear on reading the following description of a preferred embodiment given by way of non-limiting example, described with reference to the figures in which:

[0038] Figure 1 illustrates a mechanical part adjustment system according to a preferred embodiment of the invention.

[0039] Figure 2 illustrates the method of adjusting a mechanical part according to a preferred embodiment of the invention.

[0040] Figure 3 illustrates a step of identifying at least one area of ​​the surface of the part including an excess thickness, and identifying the excess thickness, included in the method of Figure 2.

[0041] Figures 4a, 4b, 4c and 4d illustrate a surface reconstruction step, included in the method of Figure 2.

[0042] Figure 5 illustrates an example of a trajectory generated according to a preferred embodiment of the invention.

[0043] Identical, similar or equivalent parts of different figures bear the same numerical references so as to facilitate the transition from one figure to another.

[0044] The different parts represented in the figures are not necessarily on a uniform scale, to make the figures more readable.

[0045] The different possibilities (variants and embodiments) must be understood as not being mutually exclusive and can be combined with each other.

[0046] DETAILED PRESENTATION OF SPECIFIC EMBODIMENTS

[0047] According to a preferred embodiment shown in Figure 1, a mechanical part adjustment system is for example intended to carry out the adjustment of parts to be placed in a gas stream of the turbomachine. The mechanical part is a high-pressure turbine part, in particular a distributor which is part of the stator of the turbine. We consider a mechanical part 1 which has previously undergone an operation of adding material due to the formation of cracks on its surface. An addition of material on the part causes an excess thickness compared to the initial geometry of the part. The purpose of the adjustment is to remove this excess thickness and to restore the part to its initial geometry, or at least to give it a profile suitable from an aerodynamic point of view, without localized excess thicknesses.

[0048] The adjustment system comprises a support 2 adapted to receive and hold the part to be adjusted 1. The support can be movable so as to be able to provide different positions for the part to be adjusted.

[0049] The adjustment system also includes an adjustment machine 3 which itself includes a robotic arm 31 configured to be able to move along several axes.

[0050] The robotic arm 31 is adapted to be equipped with an adjustment tool 32. Preferably, several adjustment tools can equip the robotic arm, for example comprising abrasives whose surface has grains whose grain size is different from one abrasive to another, so as to carry out different tasks such as cutting, grinding, sanding and smoothing. Preferably, an automatic tool changer 33 equips the adjustment machine 3 so as to equip the robotic arm 31 with the most appropriate adjustment tool 32.

[0051] The adjustment system also comprises a three-dimensional measuring device 4, for example by photogrammetry. The three-dimensional measuring device 4 is capable of carrying out a three-dimensional measurement of the part to be adjusted 1.

[0052] The adjustment system also comprises a control module 10 which controls the various elements of the adjustment system previously presented. The control module 10 has the general structure of a computer. It comprises in particular a processor 100 executing a computer program implementing the method according to the invention, a memory 101, input interfaces 102 and output interfaces 103.

[0053] These different elements are conventionally connected by a bus 105. The input interfaces 102 are connected to the different elements previously described and are intended to receive information from them.

[0054] The processor 100 executes the processing operations that will be described below. These processing operations are carried out in the form of computer program code instructions that are stored in the memory 101 before being executed by the processor 100.

[0055] The memory 101 can further store the results of the treatments carried out.

[0056] The output interfaces 103 are connected to the various elements previously described and are intended to send them instructions.

[0057] To simplify the representation, the various mechanical and electrical connections of the elements previously described have not been represented in figure 1.

[0058] The operation of the adjustment system is ensured by the control module 10 and is detailed in the form of a method described below.

[0059] Figure 2 represents the method for adjusting a mechanical part according to one embodiment of the invention. The adjustment method comprises steps E1 to E5 implemented by the control module 10 previously described.

[0060] It is assumed that a part 1 such as a high-pressure turbine stator distributor of an aircraft engine has previously undergone a material addition operation due to the formation of cracks on its surface. An addition of material results in an excess thickness compared to the surface of the original part. This excess thickness is a defect in the part.

[0061] It is also assumed that part 1 has been fixed on support 2. This is the part to be adjusted.

[0062] Step E1 is a command to the three-dimensional measuring device 4 so that it measures the part to be adjusted 1, for example by photogrammetry, and forms a three-dimensional image of it.

[0063] To do this, the part is scanned and then polygonized. This produces a mesh that represents the actual part composed of basic elements, here of the triangle type. The theoretical profile of the surface considered is continuous, which implies that the mesh elements composing it have substantially the same characteristics.

[0064] The three-dimensional image data thus produced are stored. The next step E2 is a processing of the three-dimensional image to identify the area(s) of part 1 which has / have material additions, i.e., excess thicknesses. The excess thicknesses themselves are also identified. Correlatively, the areas not having excess thickness are also identified. In the rest of the processing, only the areas with excess thickness are processed, and the areas without excess thickness are excluded from the processing and are left intact. In other words, the processing is reserved only for the areas having excess thicknesses.

[0065] Step E2 is described with reference to Figures 3 and 4a to 4d and comprises sub-steps E21 to E24.

[0066] Figures 4a to 4d represent a search area for a healthy zone in which an excess thickness is located. The zone has, for example, a diameter between 10 and 20 mm, for example 15 mm. Indeed, among all the types of brazing excess thicknesses, none has dimensions greater than 15 mm in all directions. Such a search area dimension therefore makes it possible to systematically have healthy zones. This dimension also makes it possible to find a balance between the following factors: processing time (non-linear), overlap between the different zones so as not to forget any zone, double analyses generated (time-consuming redundancy) ...

[0067] Sub-step E21 is a pre-detection of irregularities on the surface of the mechanical part. An irregularity is shown in Figure 4a. It may be an excess thickness to be treated or another irregularity not treated within the scope of the invention, such as a cooling hole present in the air stream.

[0068] To do this, the curvature of the mesh elements is analyzed. During an initial selection, mesh elements whose curvature exceeds a configurable curvature threshold are identified as irregularities. The curvature threshold varies, in particular, depending on the areas of the part analyzed.

[0069] Preferably, a second selection is carried out to also select the mesh elements neighboring the mesh elements identified as irregularities, over a number of ranks which is for example 5. The number of ranks is determined empirically and can be configurable.

[0070] The set of selected mesh elements is the set of pre-detected irregularities. It is assumed in the following that at least one irregularity has been detected.

[0071] The next sub-step E22 is a filtering of pre-detected irregularities in order to remove them from the three-dimensional image data.

[0072] Filtering irregularities results in surface area data in which irregularity data have been removed (Figure 4b).

[0073] The surface area data after defect filtering thus identifies a so-called healthy area.

[0074] The next sub-step E23 is a surface reconstruction at the level of the area of ​​the part surface that has been removed, based on the healthy area located around the removed area on both sides. The reconstruction is carried out by a function with a continuous slope, for example defined by a polynomial equation. The polynomial equation is for example of order 5, or higher, which in practice allows good quality results to be obtained.

[0075] Thus, the reconstruction uses the healthy area surface data determined in the previous step and results in reconstructed surface data corresponding to a defect-free surface (Figure 4c).

[0076] The next sub-step E24 is a comparison of the data of the real surface of the part with the data of the reconstructed surface in the considered area (figure 4d).

[0077] The comparison makes it possible to isolate the part of the mesh corresponding to the excess thickness. This step allows identification and characterization of the excess thickness located in the area considered.

[0078] For a given excess thickness, the result of step E2 is a set of data representing the excess thickness, called excess thickness data, and a set of data representing the area including the excess thickness. The data are typically point coordinates. For example, the excess thickness data are point coordinates of the given excess thickness. It is possible to associate an excess thickness value with each point considered.

[0079] It should be noted that in some highly curved areas, and for patch-type rework, the curvature of the basic elements (elementary triangles) is already significant even in the absence of irregularity. In this case, the use of the curvature of the basic mesh elements for the pre-detection of irregularity on the part surface (sub-step E21) may not be optimal. For these areas, an alternative method to identify and characterize an overthickness (step E2) can be an adjustment between a model of the part and the three-dimensional image of the part. This adjustment can be made between a part of the model of the part on the one hand (model corresponding to the theoretical geometry of the part, given by its CAD representation), and a part of the actual measured surface on the other hand.Such a local (rather than global) adjustment makes it possible to overcome possible deformations of the part compared to its theoretical CAD (in particular relative deformations, of one part of the part compared to another part of the part, for example of the leading blade compared to the driven blade). This method is however less effective on beads and prominent defects in the air streams. In the example process described here, for the most curved areas of the part (leading edge for example), it is this alternative method which is used instead of the surface reconstruction method which was presented above with reference to figures 4a to 4b.

[0080] Step E2 is followed by step E3 which is the determination of a trajectory of the adjustment tool 32. Step E3 is described for a detected excess thickness, or defect, in a given zone, and is repeated for all the excess thicknesses detected on the part considered.

[0081] The part has been previously processed by CAD / CAM software, in order to produce a programmed trajectory. The programmed trajectory is a machining trajectory which would lead, after machining, to a surface corresponding to the surface of the theoretical CAD model of the part.

[0082] The programmed trajectory is compared with the coordinates of the fault points in the area under consideration. Each point of the programmed trajectory and each point of the fault are compared, with a comparison threshold, so as to retain only the points of the programmed trajectory whose distance from the fault points is less than the comparison threshold. The value of the threshold is, for example, between 0.1 and 0.3 mm.

[0083] It is possible to make local adjustments between a part of the CAD geometry and the real geometry, in order to overcome possible deformations generating differences between the theoretical CAD geometry and the real geometry of the part, in particular relative deformations of one part of the part compared to another part of the part, and thus reposition the trajectory to be carried out. This makes it possible to improve the precision of the positioning of the tool in relation to the part.

[0084] Alternatively, the CAM calculation of the tool path is performed on the basis of the reconstructed surface (without excess thickness), obtained at the end of sub-step E23 and which is based on the actual geometry recorded rather than on the theoretical CAD base. The calculation complexity is greater, but the accuracy is increased since this makes it possible to avoid possible deformations of the part.

[0085] The points thus retained form a trajectory of the adjustment tool, as illustrated in Figure 5. Figure 5 represents a portion of the surface of a mechanical part containing defects. For one of the defects, the generated trajectory is represented by dotted lines.

[0086] The next step E4 is a command to the adjustment machine 3 so that it carries out the adjustment of the part according to the determined trajectory of the adjustment tool 32.

[0087] Optionally, in particular when the programmed trajectory is obtained on the basis of the theoretical CAD modeling of the part and without local recalibration, the first contact of the tool with the excess thickness can be detected, for example with a power meter. The tool is then controlled to perform a progressive descent, in successive passes, for example with a vertical increment of between 0.01 and 0.05 mm, or even between 0.02 and 0.03 mm. This detection of contact then progressive descent makes it possible to overcome errors, in the programmed trajectory, due to deformations of the real part compared to its theoretical CAD modeling. Step E4 comprises the selection of an adjustment tool 32 and the control of the tool changer 33 so that it equips the adjustment arm 31 with the selected adjustment tool 32.

[0088] Step E4 may involve the successive use of two adjustment tools, a first tool being intended to carry out a coarse material removal and a second tool being intended to carry out a gentle abrasion to produce a smooth surface. Of course, the number of successive tools may be greater than two, each tool producing a finer abrasion than the previous one.

[0089] The next step E5 is an inspection of the machined part. According to a first variant, the inspection is carried out visually by an operator, for example during a manual finishing operation following machining.

[0090] According to a second variant, the three-dimensional measuring device 4 is controlled so that it measures the part 1 after adjustment, for example by photogrammetry, and forms a three-dimensional image of it. This step is similar to step E1. The image formed is analyzed to verify the conformity of the result of the adjustment with an expected result.

Claims

CLAIMS 1. Method for adjusting a turbomachine part to be placed in a gas stream of the turbomachine, the part having previously undergone an operation of adding material to fill a defect in at least one area of ​​its surface, resulting in an excess thickness in the at least one area of ​​its surface, characterized in that it comprises steps of: - command (El) for forming a three-dimensional image of the part, - identification (E2) of at least one area of ​​the surface of the part including the excess thickness, and identification of the excess thickness, in the three-dimensional image of the part, - determination (E3) of a trajectory of an adjustment tool, as a function of the geometry of the identified excess thickness, and - command (E4) to adjust the part according to the determined trajectory.

2. Method for adjusting a part according to claim 1, in which the step (E2) of identifying the at least one area of ​​the surface of the part including the excess thickness, and identifying the excess thickness comprises: -A pre-detection (E21) of irregularity on the surface of the part, then, in the case of the pre-detection of at least one irregularity, - filtering (E22) of data representing the at least one irregularity to produce zone data in which the data representing the at least one irregularity have been deleted, called healthy zone data, - a surface reconstruction (E23) carried out by a function having a continuous slope, from the healthy area data to produce reconstructed surface data corresponding to a surface without excess thickness, - a comparison (E24) of the data of the real surface of the part with the data of the reconstructed surface, and, depending on the result of the comparison, an identification of the excess thickness.

3. A method of adjusting a part according to claim 2, wherein the three-dimensional image of the part comprises a mesh which represents the actual part composed of mesh elements and the pre-detection of irregularity on the surface of the part comprises the identification of first mesh elements whose curvature exceeds a curvature threshold as irregularities.

4. Method for adjusting a part according to claim 2, in which the pre-detection (E21) of irregularity on the surface of the part further comprises the identification of second mesh elements neighboring the first mesh elements over a predetermined number of rows.

5. A method of fitting a part according to any one of claims 2 to 4, wherein the function having a continuous slope is defined by a polynomial equation.

6. Method for adjusting a part according to claim 1, in which the step (E2) of identifying the at least one area of ​​the surface of the part including the excess thickness, and identifying the excess thickness comprises an adjustment between a model of the part and the three-dimensional image of the part.

7. Method for adjusting a part according to any one of claims 1 to 6, in which the determination (E3) of a trajectory of an adjustment tool comprises the comparison of a predetermined trajectory with the coordinates of the points of the identified excess thickness, so as to retain only the points of the programmed trajectory whose distance from the points of the defect is less than a comparison threshold.

8. Method for adjusting a part according to any one of claims 1 to 7, in which the command (E4) for adjusting the part according to the determined trajectory comprises a detection of a first contact of the tool with the overthickness and the control of the tool so that it makes a progressive descent in successive passes.

9. System for adjusting a turbomachine part to be placed in a gas stream of the turbomachine, the part having previously undergone an operation of adding material to fill a defect in at least one area of ​​its surface, resulting in an excess thickness in the at least one area of ​​its surface, the adjustment system comprising a three-dimensional measuring device (4) and an adjustment machine (3), the adjustment system being characterized in that it comprises a control module (10) capable of: - controlling the three-dimensional measuring device (4) to form a three-dimensional image of the part, - identify at least one area of ​​the surface of the part including the excess thickness, and identify the excess thickness, in the three-dimensional image of the part, - determine a trajectory of an adjustment tool, based on the geometry of the identified excess thickness, and - control the adjustment machine (3) to adjust the part according to the determined trajectory.

10. Computer program comprising instructions for executing the steps of the method according to any one of claims 1 to 8 when said program is executed by a computer.

11. Computer-readable recording medium on which is recorded a computer program comprising instructions for carrying out the steps of the method according to any one of claims 1 to 8.

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