Adaptive Repair Method for Aerofoil Blades

Abstract

This disclosure concerns an adaptive repair method, for example for aerofoil blade components. The method generates a digitised model of a physical component and uses data from the digitised model to align a part of the physical component with a nominal CAD model of the component. A combination of the digitised data and data from the nominal CAD model are then used to create an adapted model for repair of the component.

Claims

1. An adaptive repair method comprising the steps of providing a digitized model of a base portion of a physical component, aligning a corresponding base portion of a nominal CAD model of said component with the digitized model such that the nominal model extends beyond the digitized model used for alignment, extracting a set of co-ordinate points from the nominal model once aligned and lofting a cross-sectional profile based on the measured profile of the base portion along a path defined by the co-ordinate points of the nominal model once aligned to create an adapted model for repair of the component; and adding material to the component based on the adapted model.

2. An adaptive repair method according to claim 1, wherein the digitized model is created by digitizing an entire component and electronically cutting back the resulting model to a predetermined crop plane.

3. An adaptive repair method according to claim 1, wherein the physical component is physically cut back before digitizing to create the digitized model of the base portion.

4. An adaptive repair method according to claim 1, wherein the cross-sectional profile is adapted to create an oversized material addition region for a material addition step in the adapted model.

5. An adaptive repair method according to claim 1, wherein the adapted model includes tool path data within the oversized material addition region for a re-profiling step in the repair process.

6. An adaptive repair method according to claim 1, further comprising the step of machining the component based on the adapted model.

7. An adaptive repair method according to claim 1, wherein the component is an aerofoil blade and the co-ordinate points comprise points at the leading edge and/or trailing edge of the blade.

8. An adaptive repair method according to claim 7, wherein the co-ordinate points comprise points on the concave and/or convex surfaces of the blade.

9. An adaptive repair method according to claim 1, wherein the co-ordinate points are located in a number of planes, at least one of said planes intersecting the digitized model of the base portion, and at least one plane being located beyond the digitized model of the base portion.

10. An adaptive repair method according to claim 9, wherein at least ten planes are located beyond the digitized model of the base portion.

11. An adaptive repair method according to claim 9, wherein at least three planes intersect the digitized model of the base portion.

12. An adaptive repair method according to claim 9, wherein at four planes intersect the digitized model of the base portion and seventeen planes are located beyond the digitized model of the base portion.

13. An adaptive repair method comprising the steps of providing a component; and a digitized model of a portion of the component; and an adapted model; and adding material to the component based on the adapted model; wherein the adapted model is provided by aligning a corresponding portion of a nominal CAD model of said component with the digitized model such that the nominal model extends beyond the digitized model, extracting a set of co-ordinate points from the aligned nominal model and lofting a cross-sectional profile based on the measured profile of the base portion along a path defined by the co-ordinate points of the aligned nominal model to create the adapted model for repair of the component.

14. An adaptive repair method according to claim 13, further comprising a step of machining the component based on the adapted model.

15. An adaptive repair method according to claim 13, wherein the digitized model is created by digitizing an entire component and electronically cutting back the resulting model to a predetermined crop plane.

16. An adaptive repair method according to claim 13, wherein the physical component is physically machined before digitizing to create the digitized model of the base portion.

17. An adaptive repair method comprising the steps of providing a digitized model of a base portion of a physical component, aligning a corresponding base portion of a nominal CAD model of said component with the digitized model such that the nominal model extends beyond the digitized model used for alignment, extracting a set of co-ordinate points from the aligned nominal model and lofting a cross-sectional profile based on the measured profile of the base portion along a path defined by the co-ordinate points of the aligned nominal model to create an adapted model for repair of the component; and further comprising a step of machining the component based on the adapted model.

18. An adaptive repair method according to claim 17, wherein the digitized model is created by digitizing an entire component and electronically cutting back the resulting model to a predetermined crop plane.

19. An adaptive repair method according to claim 17, wherein the physical component is physically machined before digitizing to create the digitized model of the base portion.

20. An adaptive repair method according to claim 17, wherein the adapted model includes tool path data within the oversized material addition region for a re-profiling step in the repair process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Practicable embodiments of the disclosure are described in further detail below by way of example only with reference to the accompanying drawings, of which:

[0032] FIG. 1A to 1D show the steps of a prior art repair process;

[0033] FIG. 2 shows the basic process steps of the present disclosure;

[0034] FIG. 3 shows the results of a high quality scan of a component;

[0035] FIG. 4 shows the alignment of a nominal model of an aerofoil blade with a measured/digitized hub portion;

[0036] FIG. 5 shows the sampling of two-dimensional points from the aligned model;

[0037] FIG. 6 shows the updating and dimensioning of the two-dimensional points;

[0038] FIG. 7 shows a lofted CAD model formed from the updated two-dimensional points;

[0039] FIG. 8 shows an example of toolpaths created by the process of the disclosure; and

[0040] FIG. 9 shows two examples of the results of the process.

DETAILED DESCRIPTION OF EMBODIMENTS

[0041] FIGS. 1A to 1D illustrate the steps of a typical repair process on a component 20. At each stage of the process highly skilled labour is required to perform each task to the required standards for aero engine repairs.

[0042] The first step, shown in FIG. 1A, is sentencing. This requires a skilled inspector to identify and classify the damaged area(s) 22 of the component 20. The component 20 is the cleaned, as illustrated in FIG. 1B, to prepare the damaged area(s) 22 for material addition. FIG. 1C shows the result of the material addition step, the process of filling in the damaged area(s) 22, which is usually accomplished with welding 24 by a highly skilled welder. Finally, the result of dressing back the weld(s) 24 to restore the aerofoil surface, re-profiling, is illustrated in FIG. 1D. Again, this step requires a high level of skill.

[0043] FIG. 2 sets out the process steps of the present disclosure in their most basic form. The steps apply for both material addition (MA) and re-machining operations.

[0044] In the example of FIG. 2, the adaptive repair process has been created using the following commercially available software from the following vendors: [0045] Innovmetric's Polyworks™ Inspector 11.0, and [0046] Siemens™ NX 7.5.

[0047] FIG. 2 shows which steps of the CADCAM process between hardware focused operations (scanning and machining) are performed with Polyworks™ Inspector 11.0 (Polyworks™ Steps) and which are performed with NX 7.5 (NX Steps). It should be understood, however, that similar software from alternative suppliers could be used without departing from the inventive concept. The steps in FIG. 2 are numbered 1 to 11, and will be described below with reference to the further Figures as appropriate.

[0048] In step 1 the component is scanned to obtain a high quality input scan of all datum features. The results of such a scan are shown in FIG. 3, where the hubs 26 of two aerofoil blades 20 are shown joined to a drum 28. Typically, a scan of an entire bladed drum 28 is produced and is then broken down into individual blade models. In instances requiring a full chord repair, where a necessary stage in the repair process is paring a damaged blade back to a hub before rebuilding a full aerofoil with material addition, the scan may be performed after the paring back operation has been performed.

[0049] FIG. 4 shows step 2 of the process, where the scanned base/hub section 26 is aligned with a nominal CAD model 30 of the aerofoil blade. Where a scan of a complete blade 20 is performed in step 1, this scan is cut back at a predetermined crop plane 32 to leave only the hub section 26 for alignment purposes. The alignment is performed locally, and once complete the nominal model 30 of the aerofoil blade is extended to allow extraction above the real aerofoil.

[0050] Step 3 of the process is to extract local co-ordinate systems following the alignment. The aerofoil gauge of the nominal model 30 is determined and used to create leading edge point, plane vector and inlet angle. Plane-line-point geometry is extracted and a local co-ordinate system is created, measured relative to world. In order to ensure that all dimensions are positive, a 100 mm offset in both X and Y directions can be incorporated.

[0051] An NX readable co-ordinate file is exported detailing the local co-ordinate system locations. In this example, a total of twenty-one planes are included to provide various aerofoil gauges. Four of the planes are located below the crop plane 32 and seventeen above to allow blending.

[0052] In step 4, the aerofoil gauge used in step 3 extracts a two-dimensional cross section profile and a two-dimensional spline is created.

[0053] FIG. 5 illustrates step 5 of the process, where the two-dimensional point coordinates are extracted from the aligned models. The aerofoil gauge capability of the Polyworks™ software is used to sample points from the cross section, and these points are converted into two-dimensional co-ordinates relative to the local co-ordinate system. Nominal points 34 from the nominal CAD model 30 are selected above the crop plane 32, and measured points 36 from the scanned hub 26 below.

[0054] The final Polyworks™ step, step 6 in FIG. 1, is to extract an NX readable text file for use in the NX steps of the process. The text file can include point co-ordinate specific data, eg section1_point1_CC_X=22.358 and/or an NX readable format expression file, eg=Vector(I,J,K).exp file.

[0055] In step 7, the NX readable text file created in step 6 is passed to the Siemens™ NX 7.5 software, where the local coordinate systems are adapted. The existing plane line point geometry is parametrically controlled and updated

[0056] Step 8 is to adapt the two-dimensional points within the NX software. Existing nominal geometry is maintained within sketches 38 based on the measured cross-sections of the aerofoil hub 26. The parametric dimensioning 40 allows updating of the points without the risk of incorporating errors into related points or geometries.

[0057] Once the points have been updated, as shown in FIG. 6, step 9 of the process is to adapt the section two-dimensional spline. The cross-section spline is recreated in the NX software and is constrained to points split into leading edge, trailing edge, concave and convex surfaces. Splitting the surfaces in this way allows for material addition dwells for cooling on the leading edge and trailing edge.

[0058] Step 10 is to generate a lofted CAD model 42 as shown in FIG. 7. Multiple adapted sketches 38 from step 9 are re-lofted to recreate aerofoil geometry, following paths defined by the nominal CAD model. The resulting model contains manufacturing offsets and metal for features by suppression.

[0059] Finally, in step 11, the lofted CAD model 42 is output for the Computer Aided Manufacturing (CAM) process. Root blending is switched off for the purposes of material addition. Only planes four to twenty-one (ie the planes at and above the cut plane 32) are used. The cropping surface is moved radially to allow for excess tip material addition or re-cutting the tip diameter. FIG. 8 illustrates a stage of the CAM process. Associative toolpaths are created on nominal surfaces, and update to move with the new surfaces.

[0060] The embodiment above generally describes a repair process where a full chord rebuild is required. However, the disclosure also allows for other repairs/re-profiling of aerofoil blades. FIG. 8 illustrates a material addition 42 and re-profile adapted 44 CAD models on the same stage three drum scan.

[0061] The described disclosure provides a process that extracts co-ordinates from a measured point cloud, and controls an adaptive parametric CAD model. The model can be used for creating either material addition CAD geometry, or the machining CAD surfaces required to 5-axis mill a new blade profile. The models are then used to generate Siemens™ NXCAM generated machine code for either material addition or machining. Any blade can be repaired on any stage of the drum.

[0062] Of particular benefit is that one model can be used to provide adaptive CAD for both material addition and re-profiling (5 axis machining) operations, and full 3D aerofoil replacement is made possible. Similar technology has only previously been used to repair patches.

[0063] The nominal adaptive CAD aerofoil blade can be moved between stages of compressors. It can also deal cope with non-timed aerofoils using an appropriate local co-ordinate system, for example as defined in pending patent application GB 1505400.0.

[0064] In addition, it is possible for the toolpath for cropping to be adapted to ensure cutter access between aerofoils. This is an important consideration when repairing untimed aerofoils. A tang can also be left so that the blade does not fall onto the part. The process needs to be accurate because of the tang's small size. If too small, the blade might fall off. If too large, the operator may not be able to remove it when required.

[0065] Points can also be output on aerofoil surfaces for 5-axis on machine probing. This can be helpful when calculating any fine machine offsets or alignment overchecks.

[0066] For the avoidance of doubt, the disclosure is not considered to be limited to the specific example described above. Examples of some changes that may be made without departing from the inventive concept include: [0067] Different software that can similarly interact (E.g. Replace NX with Catia™) [0068] All points could have world references (X, Y and Z) [0069] Variable offsets on regions of each cross section [0070] Adding positional variation to machining CAD to allow for distortion in the additive material process [0071] Different metal removal techniques like polishing or EDM [0072] Different material addition techniques like CNC welding or powder bed [0073] Application of the process to items other than compressor blades (eg turbines or fan blades)

[0074] ELE re-profiling could also be integrated with this technology, allowing the improvement/repair of multiple aerofoils on an assembly (bladed disk or conventional) for performance reasons.

[0075] This process could also be used to create an adaptive ‘condition of supply’ CAD model for other CNC controlled additive material processes, such as MIG welding, powder deposition or sintering; or indeed in other material removal processes such as Electro-Discharge Machining, Waterjet and Linishing/polishing.

[0076] Finally, the process may be used to machine an aerofoil smaller than its current size, to remove surface damage or stress raisers like nicks/dents, rather than recreating a new aerofoil from deposited material. This could speed up repair times, particularly on multi-stage drums, by reducing the need to crop the blade off and redeposit material.