WO2020109482A1

WO2020109482A1 - Method and device for customized production of replacement structure parts

Info

Publication number: WO2020109482A1
Application number: PCT/EP2019/082937
Authority: WO
Inventors: Tobias Kötter; Thorsten SCHÜPPSTUHL; Christian Schlosser; Felix JAHN; Christian Sowa
Original assignee: Lufthansa Technik Ag
Priority date: 2018-11-28
Filing date: 2019-11-28
Publication date: 2020-06-04
Also published as: DE102018130091B4; DE102018130091A1

Abstract

The invention relates to a method for customized production of replacement structure parts (40) from a blank (29) for replacing damaged structure components which are provided with a multiplicity of holes for attachment to a receiving structure (10). The method comprises here the steps: a) 3D scanning of the receiving area (11) for a replacement structure part (40) on the receiving structure (10) comprising the joints (12) for the replacement structure part (40) and the drilled holes (13) for attaching the replacement structure part (40); b) extracting model data of the joints (12) and/or drilled holes (13) on the receiving structure (10) from the point cloud (32) acquired by means of the 3D scanning, c) transferring the extracted model data of the joints (12) and/or drilled holes (13) onto model data for boundary edges (42) and drilled holes (41) for the replacement structure part (40) by means of predefined transfer functions; d) determining collision-free robot paths (43) in order to transfer the model data for boundary edges (42) and drilled holes (41) for the replacement structure part (40) onto the blank (39) of the replacement structure part (40); and e) actuating a robot (20) according to the determined collision-free robot paths (43) in order to transfer the model data onto the blank (39). The device according to the invention is configured to carry out this method.

Description

Method and device for precisely fitting

Manufacture of replacement structural parts

The invention relates to a method and an apparatus for the precise manufacture of replacement structural parts from a blank for the replacement of damaged, with a variety of holes for attachment to a receiving structure provided with structural components.

In the mechanical repair of structures, the parts of which are connected to each other with a large number of screws and / or rivets, an exchange structural part must be adapted precisely to the other existing structural components, both in terms of its external shape and with regard to the fastening holes.

Due to manufacturing tolerances, but also due to deformations in the structure during operation, it is not always possible to completely prefabricate a replacement structural part in such a way that it can be inserted directly into the repairable structure. In such cases, a blank is used which has the basic shape of the structural part in question, but has an oversize and is regularly manufactured without fastening holes.

The blank must then be manually based on the structure to be repaired and if necessary with the help of templates or the like. can be reworked so that it can be inserted as an exchange structure part in the structure.

An example of a corresponding exchange structure part is the inlet cowl lip skin segment of an aircraft engine, that is to say a segment of the annular and aerodynamically shaped cover at the inlet of the jet engine of an aircraft, in particular a commercial aircraft. Corresponding lip skins or their segments are multi-curved components and Secured to the Inlet Cowl structure with hundreds of circumferential riveted joints.

To replace a lip skin segment, a blank is used that is supplied both without holes for the fastening elements - usually rivets - and with an oversized contour. The relevant geometric elements - holes and delimiting edges - have to be transferred, introduced or adapted into the blank using the receiving inlet cowl structure and the other lip skin segments.

According to the state of the art, this is done by hand using a caliper and a special hole transfer template.

To cut the blank to the required shape, the outside contour of the required replacement structure is partially drawn with the help of a vernier caliper that is temporarily attached to an auxiliary element (e.g. an adhesive strip) attached to the Inlet Cowl structure. The blank is then cut accordingly.

For each individual hole, a mark is first made on the adjacent area of the Inlet Cowl structure using a pen and stencil. On the basis of this marking, the bore positions can then be transferred back to this spare part after placing the cut but still undrilled spare part. The required holes can be drilled immediately or initially only marked to be drilled at a later date.

The manual procedure described is very time-consuming and therefore costly. In addition, the processes require a great deal of experience on the part of the persons performing the work, in particular aircraft mechanic. However, due to the regularly high number of holes to be drilled, there is an inherent potential for error even with experienced mechanics, which is why reproducible quality can only be achieved to a limited extent.

The object of the present invention is to provide a method and an apparatus in which the disadvantages known from the prior art no longer occur or only to a reduced extent.

This object is achieved by a method according to the main claim and an apparatus according to claim 9. Advantageous further developments are the subject of the dependent claims.

Accordingly, the invention relates to a method for the precise manufacture of replacement structural parts from a blank for replacing damaged structural parts provided with a plurality of holes for attachment to a receiving structure, with the steps: a) 3D scanning of the receiving area for an exchange structural part the receiving structure comprising the abutting edges for the exchange structure part and the bores for fastening the exchange structure part; b) extracting model data of the abutting edges and / or

Drilling the receiving structure from the point cloud obtained by 3D scanning; c) transferring the extracted model data of the abutting edges and / or bores to model data for boundary edges and bores for the exchange structural part by means of predetermined transfer functions; d) determining collision-free robot paths for transferring the model data for boundary edges and bores for the exchange structure part onto the blank of the exchange structure part; and e) triggering a robot according to the determined collision-free robot paths for transferring the model data to the blank.

Furthermore, the invention relates to a device for custom-made manufacture of replacement structural parts from a Roh ling to replace damaged, with a plurality of holes for attachment to a receiving structure provided structural components comprising

- A 3D scanner for scanning the receiving area for an exchange structure part on the receiving structure comprising the abutting edges for the exchange structure part and the bores for fastening the exchange structure part;

a control and calculation device which is designed to:

- extract model data of the abutting edges and / or bores on the receiving structure from the point cloud obtained by the 3D scanning;

- To transfer the extracted model data of the abutting edges and / or bores to model data for boundary edges and bores for the exchange structural part by means of predetermined transfer functions; and

- Collision-free robot tracks for transferring the model data for boundary edges and holes for determine the exchange structure part on the blank of the exchange structure part; and

- Train a robot to transfer the model data to the blank according to the collision-free robot determined.

The invention accordingly creates a method in which an exchange structure part can be produced automatically and precisely on the basis of a suitable blank. Due to the automation achieved in accordance with the invention, it is possible to produce at low cost with consistent quality over a number of replacement structural parts.

The invention has recognized that for a tailor-made manufacture of an exchange structural part regularly not on construction drawings or the like. can be used, since both the outer contour of the component to be replaced, but in particular the bores for fastening the component are subject to considerable manufacturing tolerances and the ultimately receiving structure can deform over time. Rather, the structure for which the exchange structure part is produced is used directly, so that all deviations from the original construction of the structure can be taken into account when producing the exchange structure part.

The present invention deliberately relies on the automated machining of blanks in the production of replacement structural parts. This is because the invention has recognized that the structural parts, which are fastened to adjacent structural parts with a large number of rivets or screws, are regularly exposed to such a high mechanical and / or thermal load that constructive manufacturing processes Ren, such as 3D printing, are not (currently) suitable for corresponding exchange structure parts. By using blanks, mechanically and thermally sufficiently durable replacement structural parts can be produced.

At the beginning of the method, the receiving area for the exchange structure part to be produced is first recorded on the receiving structure, including the abutting edges for the exchange structure, and the bores for fastening the exchange structure in part as a 3D scan. In other words, after removal of the damaged or exchanged structural part, that area of the structure which comprises the required outer contour of the exchanged structural part and all bores for fastening the missing and to be replaced structural part should be completely scanned. The 3D scanning is preferably done in a contactless manner and can be carried out, for example, with a robotic optical measuring system.

The result of the 3D scanning is a point cloud, which partly reflects the surface of the scanned structure - in particular comprising the connection area for the exchange structure to be produced. Since the point cloud cannot be used directly for the subsequent steps, the abutting edges and / or the bores of the receiving structure are determined from the point cloud after the point cloud has been obtained. So model data are extracted from the point cloud, which reflect the abutting edges and / or bores. The model data are logically and / or mathematically describable 3D lines of any shape (straight lines, circles, arcs, ellipses, splines, etc.), as they are known from the area of 3D CAD, for example. The extracted model data can be visualized as a wireframe model.

A preferred variant for extracting model data from point clouds comprises the steps: - Identification of points of the point cloud as edge points by calculating an edge point probability, preferably on the basis of the angle criterion, half disc criterion and / or shape criterion;

- Summary of the identified edge points into an individual one or more abutting edges or edge point groups describing a bore, preferably based on a distance metric; and

- Determine an analytical description of the edge

points of each edge point group.

In other words, those points from the point cloud that are most likely to be located at the edge of the structure depicted by the point cloud are identified, regardless of whether it is a boundary edge of the structure itself or the delimitation of a borehole.

To determine the edge point probability for each individual point of the point cloud, the angle criterion, half disc criterion and / or shape criterion can be used, as described in detail in G. H. Bendels et.al. "Detecting Holes in Point Set Surfaces" (Journal of WSCG 14, 2006, pp. 89-96) and S. Gumhold et al. "Feature extraction from point clouds" (Proceedings of 10th international meshing roundtable, 2001) are discussed.

The edge points are then grouped together in such a way that the edge points of a group each reflect a geometric feature of the structure - in particular a butt edge or a hole. The assignment to a group can be based, for example, on a distance metric, in which only those edge points are assigned to a group if the distance to at least one further edge point in the group is below a predetermined threshold value lies. If the threshold value for the distance is greater than the resolution of the 3D scanner, but smaller than the smallest distance between two neighboring geometric features of the structure, the desired assignment to the individual edge point groups is generally very reliable.

For the edge point groups thus determined, analytical descriptions are then determined on the basis of the edge points contained therein. A search is made for an analytical and therefore logically and / or mathematically expressable function which reflects the edge geometry represented by the edge points of the respective edge point group as precisely as possible. Any complex logical and / or mathematical functions can be adapted to the boundary points of the respective groups. However, it is preferred if certain analytical descriptions are specified for at least some of the geometric shapes to be expected, in order to be adapted to the boundary points if necessary. A 3D circle - that is to say a circle whose radius and position in the three-dimensional space can be adapted as desired - is preferably specified as one of possibly several analytical descriptions in order to be able to use it to describe, in particular, holes in the structure.

It is preferred if, before or after determining the analytical description, the marginal points, marginal point groups and / or analytical descriptions irrelevant for the exchange structure part are discarded. If boundary points and / or boundary point groups can already be determined as irrelevant for the production of the exchange structure part, for example because they describe bores that are not intended for connection to the exchange structure part, the computing power can be used for the determination the analytical description for these marginal points and / or marginal point groups can be saved. The same applies to analytical descriptions that have already been determined: For the manufacture of the replacement structural part irrelevant analytical descriptions need not be taken into account in the subsequent steps, which can save computing power.

The extracted model data, which reflect the abutting edges and / or the bores on the receiving structure, are transmitted to model data for the boundary edges and / or bores for the exchange structure part by means of predetermined transfer functions. Since the extracted model data only represent the recorded receiving structure on which the exchange structure part is to be located or with which it is to be connected, it is not always possible to transfer the model data of the receiving structure to the exchange structure part and, finally, the blank. Rather, it is envisaged to convert the extracted model data into model data for the exchange structure part using transfer functions, it being possible, for example, to take into account the thickness of the exchange structure in the area of the holes for connecting elements. In addition, it is preferred if, in the transfer functions, distances between abutting edges of the structure and the respective boundary edges of the exchange structure are provided, for example in order to create a gap for sealing compound between the receiving structure and the exchange structural part.

A 3D model of the blank can be used to transfer the extracted model data of the abutting edges and / or holes to model data for boundary edges and holes for the replacement structure part, in order to ensure that the transferred model data for boundary edges and holes for the exchange structure part actually lie on the Find the blank to be processed or its surface below. It can be provided that the model data for boundary edges and bores for the exchange structural part can be checked and / or edited manually before the final implementation of the model data in the blank takes place.

On the basis of the model data for boundary edges and bores for the exchange structure part, which may have been changed manually, collision-free robot tracks for transferring this model data to the blank of the exchange structure part are then determined in a known manner. In addition to the model data, this also requires information about the robot and, in particular, its mobility, which is, however, regularly available.

Finally, a robot is controlled in accordance with the determined collision-free robot paths for transferring the model data to the blank. The transfer of the model data to the blank can include the marking of bores and boundary edges, which can then be worked out accordingly - if necessary also manually - or the direct introduction of bores and / or the milling of boundary edges. Robots suitable for this purpose are known from the prior art.

At the end of the process, there is a replacement structural part made from a blank, which can be fitted into the structure to be accommodated and attached directly to it.

To explain the device according to the invention, reference is made to the above statements.

The invention will now be described by way of example with reference to a preferred embodiment with reference to the accompanying drawings. Show it: FIG. 1: schematic representation of the inlet cowl area of an aircraft engine with the lip skin segment to be set removed;

Figure 2: a 3D scanner for scanning the inlet cowl

Figure 1;

Figure 3: exemplary section of a point cloud as

Result of the 3D scanner from FIG. 2;

FIG. 4: schematic representation of the model data of the Inlet Cowl from FIG. 1 extracted from a point cloud according to FIG. 3;

Figure 5: schematic representation of the model data transferred to a blank based on the model data of the Inlet Cowl along with collision-free robot tracks; and

FIG. 6: schematic representation of a robot for transferring the model data according to FIG. 5 to a blank.

FIG. 1 shows a section of an inlet cowl 1 of an aircraft engine from which a defective lip skin segment 2 has already been removed. The adjacent lip skin segments 2 have remained on the inlet cowl 1, as have the connecting straps 3 with which the lip skin segments 2 on the inlet cowl 1 and the adjacent lip skin segments 2 are connected. The connecting tabs 3 have a hole image 4 to be firmly connected to the parts to be connected by rivets 5.

The inlet cowl 1 and the remaining lip skin segments 2 together with connecting straps 3 form an accommodating one Structure 10 in the sense of the present invention with a receiving area 11 for an exchange structure part 40 as a replacement for the already removed defective lip skin segment 2. So that the exchange structure part 40 fits into the receiving area 11, on the one hand, its outer contour must match that of the receiving structure 10 defined boundary of the receiving area 11 to be adapted, on the other hand, the pattern to be provided for the attachment to the exchange structural part 40 on holes 41 must be designed for the holes 13 provided in the connecting tabs 3. The butt edges 12 relevant in this connection and the bores 13 in the connecting straps 3 are indicated in FIG. 1.

According to the invention, it is provided that the recording area 11 is captured by means of a 3D scan method.

FIG. 2 shows an example of a device 20 suitable for the desired 3D scan.

The device 20 comprises a robot 21 and a workpiece carrier 23 rotatable about a vertical axis 22 for receiving the receiving structure 10. The robot 21 has a tool changer 24, one tool being a laser line sensor 25. Robot 21 incl. the workpiece carrier 23, the tool changer 24 and the laser line sensor 25 are respectively controlled via control units 26, 27, 28 assigned to them, which are connected via a bus system 29 to a higher-level control and calculation device 30 which controls the various components the device 20 coordinates. A terminal 31 is also arranged on the control and calculation device 30, via which a user can influence the control of the device 20. Due to the tool changer 24, it is possible to provide the robot 21 optionally with a marking pen or machining elements, such as drills or milling cutters, so that the device 20 according to FIG. 2 basically also for the machining of a blank 39 explained in conjunction with FIG. 6 suitable is.

The control and calculation device 30 controls the device 20 such that the receiving area 11 of the receiving structure 10 shown in FIG. 1 is completely captured. The laser line sensor 25 provides one as a result

Point cloud 32 of the receiving area 11 including the relevant abutting edges 12 and the bores 13. An exemplary section of a corresponding point cloud 32 is shown in FIG. 3.

From the point cloud 32, model data of the impact edges 12 and the bores 13 are then extracted by the control and calculation device 30. For this purpose, the boundary points in the point cloud 32 are first determined by calculating a boundary point probability on the basis of the angle criterion, the half-pane criterion and the shape criterion, as is known from the literature. These identified edge points are then combined based on a distance metric into individual one or more abutting edges 12 or edge point groups describing a bore 13, for which an analytical description is then determined in each case. A 3D circle is predefined as the analytical description for the bores 13, and a straight line projected onto the surface of the blank, which is in the form of 3D CAD data, is provided for the abutting edges 12.

After determining the analytical description for all of the abutting edges 12 and bores identifiable in the point cloud 32 13 then the analytical descriptions irrelevant for the production of the exchange, some 40 - e.g.

all holes 13 outside the abutting edges 12 - discarded, so that only analytical descriptions of the actually relevant geometry of the receiving area 11 remain. These can be represented, for example, as a 3D CAD model, as is shown in FIG. 4 as a simplified top view, which is particularly reduced in terms of the number of holes 13.

Based on the extracted model data of the abutting edges 12 and bores 13 in the receiving area 11 of the receiving structure 10, model data for the boundary edges 42 and bores 41 for the exchange structure part 40 are then determined by the control and calculation device 30 with the aid of predetermined transfer functions this fits the receiving area 11 of the receiving

Structure 10 is. For example, the position of the holes 41 is adjusted taking into account the wall thickness of the blank 39. In addition, the boundary edges 42 are changed so that in the inserted state of the exchange structural part 40 produced from the blank 39 in the receiving region 11 of the receiving structure 10 between the boundary edges 42 and the abutting edges 12 there is a gap for receiving sealing material.

The model data obtained in this way for the boundary edges 42 and bores 41 for the exchange structure part 40 can also be represented as 3D CAD data, as is shown in FIG. 5 analogously to the representation from FIG. 4. This model data can still be adjusted manually if required.

If the model data - for example via the terminal 31 - is released by a user, in a next step the Control and calculation device 30 collision-free ro bot tracks 43 for transferring the model data for boundary edges 42 and holes 41 for the exchange structural part 40 determined on a blank 39. These robot tracks 43 can be determined in a known manner taking into account the degrees of freedom of the robot 20 and are indicated in FIG. 5.

The robot tracks 43 determined in this way are then used to control the robot 20 with which the model data are transferred to the blank 39 (FIG. 6). The robot 20 executes the holes 41 itself directly, while the boundary edges 42 are only drawn on the blank 39, so that the desired exchange part 40 can be triggered from the blank 39 in a manual processing. The exchange structure part 40 thus arises from the blank 39 by machining by the robot 20 and by subsequent manual machining. The change between the drill and the marking pen is carried out with the aid of the tool changer 24.

The exchange structure part 40 produced in this way fits directly into the receiving area 11 of the receiving structure 10. A further fitting is fundamentally not necessary.

Claims

1. A method for the precise manufacture of exchange structural parts (40) from a blank (39) for replacing damaged ter, with a plurality of holes for attachment to a receiving structure (10) provided structural components, with the steps: a) 3D scanning the receiving area (11) for an exchange structure part (40) on the receiving structure (10) comprising the abutting edges (12) for the exchange structure part (40) and the bores (13) for fastening the exchange structure part (40); b) extracting model data of the abutting edges (12) and / o of the bores (13) on the receiving structure (10) from the point cloud (32) obtained by 3D scanning; c) transferring the extracted model data of the abutting edges (12) and / or bores (13) to model data for boundary edges (42) and bores (41) for the exchange structure part (40) by means of predetermined transfer functions; d) determining collision-free robot tracks (43) for transmitting the model data for boundary edges (42) and bores (41) for the exchange structure part (40) onto the blank (39) of the exchange structure part (40); and e) controlling a robot (20) according to the determined collision-free robot paths (43) for transferring the model data to the blank (39).

2. The method according to claim 1,

characterized in that Extracting model data of the abutting edges (12) and / or of the bores (13) on the receiving structure (10) from the point cloud (32) obtained by 3D scanning comprises the steps:

- Identification of points of the point cloud (32) as

Edge points by calculating an edge point probability, preferably based on the angle criterion, half-disc criterion and / or shape criterion;

- Summary of the identified edge points into an individual one or more abutting edges (12) or a hole (13) describing edge point groups, preferably based on a distance metric; and

- Determine an analytical description of the edge

points of each edge point group.

3. The method according to claim 2,

characterized in that

Various analytical descriptions are predefined for determining an analytical description, the predefined analytical descriptions comprising a 3D circle for describing bores (13).

4. The method according to claim 2 or 3,

characterized in that

before or after determining the analytical description, the marginal points, marginal point groups and / or analytical descriptions that are irrelevant for the exchange structure part (40) are discarded.

5. The method according to any one of the preceding claims,

characterized in that

the transfer function for transferring the extracted Consider model data of the abutting edges (12) on model data for boundary edges (42) specifications with regard to distances between abutting edges (12) and boundary edges (42).

6. The method according to any one of the preceding claims,

characterized in that

the transfer of the model data to the blank (39), the drawing of bores and boundary edges, the introduction of bores and / or the milling of boundary edges.

7. The method according to any one of the preceding claims,

characterized in that

the 3D scanning is contactless and is preferably carried out with a robot-guided optical measuring system (25).

8. The method according to any one of the preceding claims,

characterized in that

Model data for boundary edges (42) and bores (41) for the replacement structural part are manually checked and / or processed before the determination of collision-free robot paths (43).

9. Device for the precise manufacture of exchange structural parts (40) from a blank (39) for replacing damaged ter, with a plurality of holes for attachment to a receiving structure (10) provided structural components comprising

- A 3D scanner for scanning the receiving area (11) for an exchange structure part (40) on the receiving structure (10) comprising the abutting edges (12) for the exchange structure part (40) and the bores (13) for fastening the exchange structure part (40) ; - A control and calculation device (30), which is designed to:

- Extract model data of the abutting edges (12) and / or bores (13) on the receiving structure (10) from the point cloud (32) obtained by the 3D scanning;

- the extracted model data of the abutting edges (12)

and / or to transfer bores (13) to model data for boundary edges (42) and bores (41) for the exchange structural part (40) by means of predetermined transfer functions; and

- Collision-free robot tracks (43) for transferring the model data for boundary edges (42) and bores (41) for the exchange structure part (40) to determine the blank (39) of the exchange structure part (40); and

- A robot (20) for transferring the model data to the blank (39) according to the collision-free robot tracks (43) determined.

10. The device according to claim 9,

characterized in that

the device for performing a method is designed according to one of claims 2 to 8.