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From a 3D point cloud to an engineering CAD model:a knowledge-product-based approach for reverseengineeringA Durupt a , S. Remy a , G. Ducellier a & B. Eynard ba ICD-LASMIS , Université de Technologie de Troyes , 12 Rue Marie Curie, 10010, Troyes,Franceb Department of Mechanical Engineering , Université de Technologie de Compiègne ,Compiègne, FrancePublished online: 09 May 2008.

To cite this article: A Durupt , S. Remy , G. Ducellier & B. Eynard (2008) From a 3D point cloud to an engineering CADmodel: a knowledge-product-based approach for reverse engineering, Virtual and Physical Prototyping, 3:2, 51-59, DOI:10.1080/17452750802047917

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From a 3D point cloud to an engineering CAD model: a knowledge-product-based approach for reverse engineering

A Durupt$, S. Remy$*, G. Ducellier$ and B. Eynard%

$ICD-LASMIS, Universite de Technologie de Troyes, 12 Rue Marie Curie, 10010 Troyes, France

%Department of Mechanical Engineering, Universite de Technologie de Compiegne, Compiegne, France

Reverse engineering (RE) is an area of current interest in which physical models are

measured or digitised to obtain a virtual model. Currently, geometric models are rebuilt

using geometric approaches. These models are generally frozen (i.e. not parameterisable

and not easy to modify). This paper deals with a new knowledge-based approach for

reverse engineering that enables nonfrozen computer-aided design (CAD) models.

According to the product knowledge, we propose to assist CAD software application

user to build the tree structure of the product. The proposed approach aims to obtain an

engineering CAD model by merging existing geometric approach and the tree structure of

the product.

Keywords: reverse engineering; product design; segmentation; feature extraction

1. Introduction

Reverse engineering (RE) is an area that is currently

attracting a lot of interest. It appears that, nowadays,

companies, organisations and suppliers need to manufac-

ture old parts or products they use everyday. As an example,

RE is massively used by the US army (Army research office

virtual parts engineering research initiative, VPERI) for the

maintenance of their legacy parts because of the absence of

documentation. In the forging industry, people have to

manufacture new tools for old parts. Also, suppliers have to

produce parts from the prototype of a customer.

Regarding the current RE approaches and according to

users, the results are not good enough because geometric

models rebuilt are generally frozen (parametric surface

approaches or meshed surface approaches). Consequently,

the possibility for re-engineering or re-designing the parts

does not exist. For example, in a meshed model, a hole has

no diameter and no axis but it is only composed of a set of

triangles. Moreover, applying constraint of a parallelism or

a fillet between two faces is impossible. With the ‘surface/

solid based approaches’, the three-dimensional (3D) point

cloud of the original object is changed into a surface model

or a solid model. If the software application used is not a

full computer aided design (CAD) tool, the resulting model

is generally composed of NURBS surfaces, even if it is

made of primitive features (plane, cylinder). This kind of

model is as useless as a meshed model with regards to re-

design facilities. Surface models or solid models can be also

obtained from point clouds using CAD software solution.

In this case, it is possible to obtain a model that enables re-

design approach but it is a very long set of geometric

operations.

In this paper, we propose a new approach which takes

into account knowledge about the lifecycle of the original

product. In a real CAD model, designers put data about

expert knowledge (with parameters and relationships),

about the manufacturing process (draft angles . . .), about

the function of the product (roughness . . .) . . . A geometric

approach is not sufficient for obtaining such a product

model. The knowledge dealing with the product, its lifecycle

and its environment have to be considered as well as the

geometric appearance.

Thus, the presented approach proposes to formalise

this knowledge and to semi-automate the rebuilding

*Corresponding author. Email: sebastien.remy@utt.fr

Virtual and Physical Prototyping, Vol. 3, No. 2, June 2008, 51�59

Virtual and Physical PrototypingISSN 1745-2759 print/ISSN 1745-2767 online # 2008 Taylor & Francis

http://www.tandf.co.uk/journalsDOI: 10.1080/17452750802047917

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methodology. The objectives of this approach is to obtain

an engineering CAD model with a tree structure of features

called functional and structural skeleton. The originality of

this approach is the merging between a classical geometric

approach (point cloud segmentation and features data

extraction) and a knowledge based approach (functional

and structural skeleton).

This paper is organised as follows: section 2 presents a

state of the art of segmentation techniques and knowledge

formalisation. Section 3 presents the research directions,

techniques and concepts that are proposed. Section 4

proposes to illustrate the presented approach using a case

study concerning an automotive journal cross.

2. State of the art

2.1 Segmentation techniques

Segmentation is a complex iterative process that aims to

logically divide the original point cloud into a set of point

clouds, one for each feature, such that it contains just those

points sampled from this particular feature (Varady et al.

1997). There are diverse methods for segmentation, which

differ according to the measurement quality, the number of

points, the geometric characteristics of the product and the

amount of human interactions required.

The two-dimensional (2D) types of segmentation techni-

ques deals with 2D images but can be applied to 2D1/2

point clouds. They are range image segmentation and range

data segmentation (Besl and Jain 1988, Yokoya and Levine

1989, Sapidis and Besl 1995).

The 3D segmentation of a 3D digitised data (Point

Cloud) is more interesting in the research context. These

types of point clouds are obtained using 3D sensors. These

sensors can be from several types (structured light, laser

triangulation, contact and so on) and are often integrated

on several devices (coordinate measuring machine, 3D

measurement, and so on). These point clouds are sets of

unorganised points representing 3D objects. We propose an

overview of several segmentation techniques. Patane and

Spagnuolo 2002 proposed an approach for edge-based

segmentation and extraction of feature lines based on a

multi-resolution representation and analysis of the scan

data. In this approach, based on a sequence of local

updates, the point cloud is organised according to a

multi-resolution hierarchy. The application domain of this

approach is defined by scan lines. This approach is

characterised by three phases: (a) multi-resolution data

modelling, (b) a scale and a geometry classification based

on form feature similarity, and (c) a two-step line by line

detection phase and segmentation. Woo et al. (2002)

introduced a different edge-based segmentation approach

that uses an Octree-based 3D grid-splitting process. An

iterative subdivision of cells is done based on the normal

values of points, and the region growing process to merge

the divided cells into several groups. A triangulation

method is used in estimating the normal point. The input

for this algorithm is a well-organised point cloud based on

the scan line from a strip type laser scanner. Benko et al.

(2001) used a noniterative approach ‘direct segmentation’

based on the fact that it is possible to compute local

characteristic quantities (e.g. normal direction) within the

interior face. This characterises the planarity of the point

neighbourhood. Then, a second-order algebraic surface is

fitted to surrounding points in the neighbourhood. How-

ever, direct segmentation produces disjoint regions, each of

which is approximated by a simple analytic or swept

surface. An extension to this work is presented in Benko

et al. (2001). As segmentation of surfaces sharing sharp

edges is easy, they present algorithms including tests to cut

surfaces sharing smooth edges. These tests are based on

statistical similarity.

In another approach for edge-based segmentation, Al-

berts (2004) declared that taking the information about

scan paths into account allows reconstructing creases and

ridges more reliably than the algorithms developed for

unorganised point cloud.

Thus, the scientific literature is composed of many

segmentation techniques. For this reason, we explore

another approach that considers the product knowledge

in order to deduce most important design parameters

(diameter, radius, for example). In the following part, we

present several references that represent the different types

of knowledge.

2.2 Definition of knowledge?

RE begins with a manufactured part and aims to produce a

geometric model. We believe that redesign is possible as

soon as the original design intents are known. In the

scientific literature, this idea is not clearly stated. Indeed,

feature extraction/recognition based approaches are often

characterised as knowledge base and ‘design intents’.

Nevertheless, feature recognition systems are purely geo-

metric based extraction from a point cloud and consist to

solve fitting problems. For example, Han et al. (2001)

presented an effort for integrating process planning and

feature recognition. Their system recognises only manufac-

turability features by consulting tool database, and, simul-

taneously, constructs dependencies among the features.

Another example, Trika and Kashyap investigated the

extraction of machining features and deal with interaction

of features. Indeed features create difficulties since the

adjacency information between some faces is lost.

However, several works deal with features recognition

systems where ‘knowledge concept’ is considered. Moha-

gheh et al. (2006) obtained ‘part’s information’ from two

different sources: the conventional way (consisting in

52 A. Durupt et al.

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measuring a real model) and reviewing the design aspects.

When using a mould to create a part, sides faces are usually

slightly rotated in order to provide a part that can be easily

removed from the mould. REFAB project (Reverse-Engi-

neering-FeAture-Based) project, by Thompson et al. (1999)

is a human interactive system where the user selects

predefined features in a list and chooses where these

features are located in the 3D point cloud. This system

supports constraints of parallelisms, concentricity etc,

which enrich the final virtual model.

Our approach is different and consists in an analysis of

the part in order to justify the presence of features and to

structure them in a CAD tree. This analysis is a kind of

‘part’s knowledge extraction’. In the scientific literature, we

notice two ‘types of knowledge’: (1) the manufacturing

knowledge and (2) the functional specification. For exam-

ple, Bespalov et al. (2005) presented several distinctive

benchmarked datasets for evaluating techniques for auto-

mated classifications and CAD model retrievals. These

datasets include two datasets of industrial CAD models

classified based on object function and manufacturing

process. The first classify into (1) prismatic machined parts

and (2) cast machined part. The second classify the function

by seven groups of models (Linkage arms, Housing,

Brackets, Nuts, Gears, Screws and Springs).

VPERI (Virtual Parts Engineering Research Initiative)

project was created by the US Army Research Office in

order to provide a solution to solve legacy systems

maintenance problem. This concerns many complex elec-

tro-mechanical products designed 25 to 50 years ago.

Because of the cost of replacement, these systems may

have to be used for decades to come, well beyond their

intended design life. Maintenance requires spare parts, but

in many cases, the original manufacturers are no longer

existing to provide them. Hence, the military needs a

comprehensive plan to determine how best to prolong the

life of these legacy systems and, in some cases, new

technology to redesign critical parts. Remanufacturing old

systems can be difficult because documentation about the

components may be unavailable, incomplete, or in a form

that is incompatible with modern computer-aided design

and manufacturing software. For these products, the

knowledge of the geometric shape and size is necessary

but not sufficient to reproduce the part. Another knowledge

such as material specification, heat treatment, surface

treatment, surface finish and tolerances must be known.

Moreover, availability of new materials, manufacturing

technologies have to be considered to improve the re-design.

Furthermore, it might be better in some cases to ignore

the original part and to re-design it completely or to replace

it with an equivalent contemporary standard device.

Actually, the performance requirements, space/weight con-

straints, mechanical/electrical connections, flow and poten-

tial variables at the connections, signal types/magnitudes

must be extracted from the existing system by physical tests

because of the missing documentation. Thus, this first

reference shows a class of product Knowledge composed of

functional specifications with, for example the mechanical/

electrical connection and signal types/magnitudes. There

are also geometric characteristics with for example, material

specification and treatments etc.

Bernard et al. (2006) proposed an approach for the

redesign of an old mechanism and try to answer to this

question ‘how to prolong longevity of the technical

information of collection, archives and heritages sites?’ In

this approach, the authors advance that knowledge has to

be capitalised from the functional diagram block of the

APTE method. Two knowledge types are distinguished:

The functional and mechanical characteristics (internal

flow design only: functional and structural); the external

data (socio-technical context environment etc).

In conclusion, functional specification should be con-

sidered for interpreting product knowledge. Therefore, a

functional analysis of the system has to be defined.

3. Research directions

The project integrates geometric recognition and knowledge

management. In fact, using only a geometric approach,

results in frozen CAD models (i.e. not parameterisable and

not easy to modify). We believe that the interpretation of

product knowledge could improve the resulting CAD

model. The originality of this approach is the merging

between a classical geometric approach (point cloud

segmentation and feature data extraction) and a knowledge

based approach (functional and structural skeleton).

3.1 Knowledge extraction

In a classical and direct design operation, a CAD model

contains expert knowledge provided by the designer (i.e.

parameters, relations, attributes). These data are domain-

related, and could concern for instance the product

mechanical functions or its manufacturing process. In a

reverse engineering context, several product details are

known. These details consist in a base to interpret the

‘product knowledge’. Once interpreted, this knowledge will

allow to constrain and/or position the different geometric

features with each other during the reconstruction phase. It

also enables the detection of surfaces from the segmentation

phase and eases the determination of driving and driven

parameters. In fact, a CAD model is not only a geometric

image of a product but also a technological and functional

image too. To improve the reconstruction process, and to

determine parameters, we need to know accurately what is

the environment of the product, what are the lifecycle data,

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and what are its functions. We truly believe this product-

related knowledge will improve the reconstruction process.

This step consists in extracting knowledge related to the

part by taking into account its lifecycle and its environment.

From our point of view and as explained in Han et al.

(2001) the first reference in section 2.2, the knowledge can

be of two types: the manufacturing knowledge (foundry,

machining . . .) and the functional knowledge. As a hypoth-

esis, we consider only these data functional knowledge and

process knowledge. We assume that both are known. For

the functional knowledge, at least one person (the one who

redesigns the part) knows at least one use case of the part

that is digitised in order to be redesign. For the process

knowledge, manufacturing features on the part are always a

good clue to indicate the manufacturing process that was

originally used to produce that part. Once known, this

manufacturing process can explain the presence of many

features (draft angle due to a forging tool, filet from a

milling machine . . .).

3.1.1. The manufacturing knowledge. Observing old parts,

the manufacturing process can be deduced. Indeed, mould,

casting extraction etc . . . leave traces on surfaces such as

line of joint for mould process. Moreover, manufacturing

process concerns certain materials. Thus, in this part, we

show that manufacturing knowledge explains the presence

of geometric shapes. Execution of different processes leads

to different shapes and particular geometric characteristics

that are important for the part. It can be extracted using

interaction with users. A table will allow to integrate

manufacturing rules extracted from different manufactur-

ing processes.

In Figure 1, a prismatic milled part could have a large

plane surface which corresponds to a fixture. Width, length,

perimeter and area can be possible driving parameters.

Another example, a cast part has drafted surfaces. Draft

angles can also be driving parameters (Figure 2).

Manufacturing knowledge interpretation can reveal driv-

ing parameters that a CAD application user should be able

to modify. Moreover, regarding the references in section 2,

functional specification could lead to reveal new design

parameters.

3.1.2. The function specification, functional analysis. An old

machine/system is a classical use case for RE. It was designed

and manufactured in order to answer a customer need. Each

one of its parts ensures one or more known functional

specification. So, the environment of the system and its

interaction with other products are known. This knowledge

enables functional analysis, which could help to explain the

presence of geometric features, and design parameters.

For example, one of the mechanical functions of a piston

is ensured by a pivot linkage with a bore. Consequently, this

linkage reveals the presence of cylindrical surfaces. Thus,

the driving parameters could be the diameter end length.

Our project aims to assist a CAD software application user

in order to extract knowledge from product in order to deduce

a class of design. These ones allow to build a design skeleton

called functional and structural skeleton. This one is studied

in LASMIS laboratories by Lionel Roucoules and Jean-

Sebastien Klein Meyer (Klein-Meyer and Roucoules (2006)).

The functional and structural skeleton is based on a skin

and skeleton concept. Skins represent any surfaces where

circulate a flow:

. Mechanical flow (Contact zone between two parts)

. Magnetic flow

. Electrical flow

Skeletons represent the material which transmits energy

flow between the various skin, it could be:

. A section (for example the section of cylinder.)

. A trajectory material flow (the axis of cylinder)

In product design, the skeleton design concept is often used

(It enables to manage a digital mock-up (DMU) for

example). In a re-design context, the functional and

structural skeleton can allow to justify the presence of the

different features of the part and the constraints and

parameters that link them with each other.

To summarise, knowledge about the lifecycle (manufac-

turing process and functional analysis) of the product can

be used to justify the presence of features as well as to

extract parameters and constraints that link these features

with each others. These features are also extracted by the

segmentation of the point cloud. It enables to create a

skeleton that will be used to correctly position and to

Manufacturing

Characteristics

Foundry

Prismatic milling

-Uniform Thickness t

-Surface drafted

- For Thickness t<=10mm ; Radius fillet R=t ;

- For t>10 ; R=0.3t

Simple Shape - Plan surfaces for Fixture - Fillets, Chamfers

Figure 1. List of processes.

Fixture

Draft angles Prismatic milledpart

Cast part

Figure 2. Geometric characteristic of a process.

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constraint the different features with each other. All these

data can be used to create the CAD model that is more than

a simple geometric image of the product.

In section 4, we propose to illustrate the proposed

approach using the case study of a journal cross of Peugeot

403.

4. The case of study of a journal cross of a Peugeot 403

The Peugeot 403 is a car produced by the French

manufacturer Peugeot from 1955 to 1966. Figure 3 shows

journal cross of a 2-door convertible version.

We propose to re-design this device in order to re-

manufacture it. Regarding the proposed approach, the

knowledge from its lifecycle is extracted. Then, it is used

to create an engineering CAD model. In the following

sections, software developments are presented.

Thus, section 4.1 presents a classical geometric approach.

Sections 4.2 and 4.3 show knowledge interpretation and a

software application that enables to deal with the extracted

data. Section 4.4 proposes a solution to connect the features

with each other using knowledge interpretation within an

engineering CAD model.

4.1 The geometric approach

Following a classical geometric approach the rebuilding of a

model from a physical part gives a frozen model. In this

section, this approach is quickly illustrated in order to

highlight some drawbacks. We assume that the 3D digitising

is already done as this paper is not about the acquisition of

the point cloud. The input of a classical geometric approach

a 3D point cloud. Figure 4 considers the 3D point cloud of

the journal cross.

Considering this point cloud, the first step of a classical

approach is the segmentation of this point cloud. It consists

in the subdivision of the point cloud in N sub-point clouds

with N as the number of features within the part. In fact,

each of these sub-point clouds represents a given feature of

the part (i.e. a plan, a cylinder, a sphere . . .). This

segmentation is usually provided by an engineer who uses

a specific software application (CATIA, Paraform, Rain-

drop Geomagic . . .) to create manually all these sub-point

clouds. Research works propose also automatic solution for

the segmentation. In this particular domain, we can notice,

for example, AlRashdan et al. (2000), Patane and Spag-

nuolo 2002, Benko (2001) and Mohib et al. (2006) proposed

a state of the art of segmentation techniques. Once the

segmentation is complete, each sub-point cloud is used to

rebuild the associated surface. Figure 5 gives the example of

a cylinder rebuilt based on a sub-point cloud segmented

from the journal cross main point cloud.

To complete the rebuilding of the journal cross model,

each sub-point cloud is processed. At this point, we can

present a drawback of this approach. Actually, each feature

is rebuilt, based on the point cloud, independently from the

others. According to the noise within the point cloud and

the inaccuracy of the scanner, the resulting geometrical

model can lack of design information that can be very

essential. For example, in a journal cross, two opposite

cylinders are coaxial. The fact is that two cylinders, rebuilt

using this classical approach, have very few chances to be

coaxial, even collinear, owing to the noise and the

inaccuracy described bove (Figure 6).

So, as already stated, the model is rebuilt feature by

feature. Each new feature imported in the model is adjusted

with the others (Figure 7).

In the end, as a result, we obtain a construction tree

composed by a set of features adjusted one with each

others. In the following picture, we give an example of such

a tree using CATIA (Figure 8).

Here, we point a second drawback of this approach. This

kind of construction tree is not useful because, for example,

it is very difficult to associate threads, parameters or

relationships to an adjustment operation. It means that

the resulting model could be used to make a copy of the

part but barely used to make real re-design operation.

Figure 3. 403 Peugeot, the 2-door convertible version. Figure 5. Rebuilt cylinder after segmentation.

Figure 4. The point cloud of a journal cross.

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In the following section, we propose a methodology to

associate the knowledge-based approach to this classical

geometric approach in order to obtain a more useful model.

4.2 Manufacturing knowledge extraction

Here, we notice from the analysis of the real part that there

is a material removal, in other terms a hole (Figure 9).

The hole is a result of the fact that the part was

manufactured by forging process. It allows to guide the

coining and the homogenisation of the material propaga-

tion. Knowledge interpretation reveals the presence of

cylinder which correspond to a material removal. The

parameters are the diameter and the length of the cylinder.

We propose an interactive interface (Figure 10). We

imagine that the CAD application user informs, after an

analysis of the part, one or more scenarios of the

manufacturing process. For each manufacturing process,

the CAD application user consults the associated rules.

Each rules corresponds to one or more features (in this use

case, a hole). The CAD application user selects or adds the

best feature for him. Hence, the functional and structural

skeleton is represented by the section of this cylinder which

is represented by the diameter and the trajectory of material

flow is represented by the cylinder axis which is represented

by the length of the cylinder.

The second step consists in extracting knowledge from

functional specifications.

4.3 The functional specifications

The environment of a journal cross is represented by two

yokes. Indeed, we propose a solution, based on a functional

analysis, which allows one to list the environment of the

part and to establish relationship between each other. In

our study case, environments are the two yokes (Figure 11).

The four functions of functional analysis facilitate the

pivot linkage between the two yokes. They reveal the

presence of four cylindrical surfaces. Then, the design

driving parameters are diameters and the lengths of each

cylinder. The software interface assists the CAD application

user in the definition of constraints and relationships

between the features defined above. In this case, axis of

the four cylinders are coaxial 2 by 2 and equal in length 2 by

2. Moreover, all diameters have the same value. We suppose

that these different constraints will enable to generate the

first functional and structural skeleton in a CAD software

application. The design tree is structured in a following

way:

. Each feature (skeleton and section) generated in a part

file.

. All features with relationships in an assembly file which

correspond at the part.

The interface enables to define constraints such as coaxial

constraint and to generate a pre-assembly file (Figure 12).

A user defines the first constraint and the system

generates a pre-constrained assembly file. Indeed, we think

that a CAD shell interface is more adapted for the

definition of more complex constraints such as for example

angle constraints and parallel constraints.

Figure 13 shows the assembly file with constraint

performed from the knowledge product and defined

manually by CAD experts. This CAD model presents the

functional and structural skeleton of the journal cross.

Figure 9. The material removal in the journal cross.Figure 7. Adjustment of imported entities.

Figure 8. The tree structure in a CAD shell.

Figure 6. Drawback due to the noise of the point cloud.

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4.4 From the skeleton to the final parameterised CAD model

From the geometrical approach, we have identified the

features composing the journal cross. From the knowledge

extraction approach, we have identified the constraints and

the relationships between all these features.

Based on these results, this paragraph deals with the

creation of an engineering CAD model of the journal cross.

Our approach is focused on the user assistance during the

reconstruction of the part. First of all, the system provides a

set of functional parameters directly extracted from the

functional analysis. The pre-constrained assembly file

elaborated in section 4.3 is improved with these parameters.

These parameters represent the geometrical values of the

journal cross. As an example, the four cylinders are

described using two parameters, one for the diameter, one

for the length.

The value of these parameters is extracted from the

segmentation in the geometric approach. The parameters

are included in a skeleton at the top of the assembly tree.

This skeleton is used as a reference for each part composing

the assembly. Each parameter is copied with reference in the

parts composing the journal cross.

At this stage, the final CAD model regroups the entire

functional and structural information and geometric para-

meters extracted from the geometrical approach. Based on

this result, the CAD application user completes the 3D

model with surface and volume information. For each type

of features, the CAD application provides multiple func-

tions of reconstruction. As an example, a cylinder can be

created using an extrusion function, a revolve or a sweep

function. In this context, our system proposed a

strong interaction with the final user. It proposes a

friendly interface for linking functional and structural

information, geometric parameters and CAD functions in

order to provide a fully parameterised CAD assembly

(Figure 14).

5. Conclusion

The RE based on geometric approach is often frozen and

not reusable. In this paper, we have proposed to focus on

the classical design approach adapted to RE issue. In this

approach, we define the functions of the product based on

the interaction of multiple expertises in order to identify

and classify the driving parameters.

Each function of the product is organised and gathered in

skeleton design called the functional and structural skele-

ton. Based on this skeleton, we propose a hybrid approach

that integrates geometric aspects and functional aspects.

The main goal of this approach is to return into a complete

and fully parameterised CAD model including design

intents.

As the first milestone, we propose a prototype software

application, which answers to the need for integration

between geometric and functional aspects of the part. In

the use case, knowledge interpretation is reduced to a single

part. This is clearly a limit of the global approach and

further research will be conducted in domains larger than

mechanical engineering. Hence, the software solution inter-

face has to take into account the product.

F1 : To ensure the first Pivot/Slider linkage between a yoke 1 and Journal Cross F2 : To ensure the second Pivot/Slider linkage between a yoke 1 and Journal Cross F3 : To ensure the first Pivot/Slider linkage between a yoke 2 and Journal Cross F4 : To ensure the second Pivot/Slider linkage between a yoke 2 and Journal Cross

Reveal a presence of cylindrical surfaces, consequently, design leading parameters are diameters and lenghts

Journal CrossYoke1 Yoke2

F2

F1 F3

F4

Figure 11. Functional analysis.

Figure 10. An example of interface for knowledge extrac-

tion.

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As the second milestone, a methodology is required to

interpret and to manage knowledge about the product in

order to deduce the set of driving parameters and construct

the functional and structural skeleton. This methodology is

clearly needed when considering larger assembly or complex

parts.

As the third milestone, we have to develop a solution for

connecting a geometry extracted with the functional and

structural skeleton.

The merging of knowledge management and the geo-

metric approach should make it possible to build a

complete and fully parameterised CAD model. Finally, we

will propose a software solution as a tool for a knowledge

based reverse engineering approach. During this project,

the results obtained will be confronted with an industrial

case from the forging industry as this uses the RE approach

to rebuild tools for old parts.

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Figure 12. A picture of future interface.

Figure 13. The functional and structural skeleton.

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