Industrial BackgroundResearch ProblematicMethod OverviewKey Characteristics Assembly Sequence Conclusion

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Benoît Marguet E.A.D.S Corporate Research Center - France

Tel : +33-1-46-97-33-46email : benoit.marguet@eads.net

Method & Tools for Method & Tools for Geometric Variation ManagementGeometric Variation Management

Industrial Background (I)Industrial Background (I)

Complex Product

Extensive manufacturing organisation

Structural Assembly

High number of parts

Various Assembly levels

Aircraft Assembly Line

Car Assembly Line

Assembly

Conversion

Material

45%45%

30%30%

25%25%

Aircraft manufacturing cost :

}Importance of Assembly Cost

Need to manage product’s assemblability

Design Manufacturing Integration

Section assemblySystem installations

Aircraft assemblySystem tests

Sectionarchitecture

DesignToolingDesign

Definition

DefinitionDrawings

ToolingDefinition

Manufacturing

Manufacturing of piece parts

Assembly of workpackages

Manufacturing of assembly toolings

Air

bu

s o

r S

up

plie

rsA

irb

us

Assemblyprinciples

Industrial Background (II)Industrial Background (II)

Development cycle of aircraft sections

Need to manage product’s assemblability as soon as possible during the development cycle

ProblematicProblematic

Sub-section assembly operation

How to improve product’s assemblability ? • By reducing assembly failures

• Parts reduction

• Geometric variation management

Where to manage product variations ?

How to control effect of variations on functional requirements?

Geometric Variation Management Method (GEOVAR)

How to reduce assembly failures ?

Method OverviewMethod Overview

Design Principle

Product Structure

j1

j2 j4

j6

j5j3

j7j8

Key Characteristics

Assembly SequenceManufacturing Capabilities

Part Specifications

GEOVAR : From product’s Key Characteristics to part’s specifications

Product Product Key Characteristics (I)Key Characteristics (I)

Concepts• Functional requirements & related geometrical characteristics

are too numerous on complex product in order to manage all of them.

• Need to focus attention of designers & manufacturers on what is really

important for the product.

Definition “Product Key Characteristics are the geometrical features of component or sub-component whose variation has the greatest influence on the product function”.

Functional Requirement Identification

(1)

Functional Requirement Identification

(1)

Geometrical Requirement

Identification (2)

Geometrical Requirement

Identification (2)

Product Key Characteristics Identification

(3)

Product Key Characteristics Identification

(3)

Identification Process

KC

1

Product Product Key Characteristics (II)Key Characteristics (II)

Functional Requirement Identification

• Inputs : Preliminary Design, Product Structure

• Outputs : Technical Requirements, Product Constraints

• Tools : FAST Diagram, MIMIO

Geometrical Requirements Identification• Inputs : Technical Requirements, Product Constraints • Outputs : Geometrical Requirements (nominal value and tolerance

level)• Tools : QFD Matrix

WHAT

Subjective customerpreferences

HOW

Objective engineering specification

Relation Matrix

How Much

Tolerance Specification

Correlation Matrix

QFD Matrix

Seat Rail Alignment

Geometrical Requirements

2

Product Product Key Characteristics (III)Key Characteristics (III)

Key Characteristics Identification

• Inputs : Geometrical Requirements, Assembly Process

• Outputs : Hierarchical requirement level, PKCs

• Tools : Risk Analysis

CandidateProduct Key

CharacteristicsCause Effect

Occ

uren

ce

Sev

erit

y

Det

ecta

bil

ity

Ris

kN

umbe

r

Distancebetween rail

seat

Misalignementbetween railseat

Sectionfitting

4 4 2 32

Rail Thickness RailSectionfitting

3 4 2 24

Position RailPosition of

FloorSectionfitting

2 4 1 8

KC

PKC

3

Product Product Key Characteristics (IV)Key Characteristics (IV)

Benefits of exercise • Defines what is, and is not, important for the variation management.

•Targets areas/features that need to be measured and monitored (through SPC).

• Helps designers to distribute tolerances & select appropriate datums.

Also • Clarifies of Design intent.

• Promotes Concurrent Engineering.

• Truly links Design, performance, manufacturing.

Product Product Key Characteristics (V)Key Characteristics (V)

Assembly Sequence (I)Assembly Sequence (I)

Problematic• Various assembly sequences are available for a single product.• All assembly sequence will have a different quality cost for the product.

Question

What assembly sequence will minimize impact of part’s variation on PKCs ?

Assembly Sequence #1

Assembly Sequence #2

Assembly Sequence (II)Assembly Sequence (II)

Concepts• Assembly Sequence analysis focus on PKCs (for variation impact). • Impact of part variation on PKCs depends on assembly sequence

choice.• Selection of assembly sequence is made very early in the design cycle.

Mate & Contact Identification

(1)

Mate & Contact Identification

(1)

Propagation Chain Identification

(2)

Propagation Chain Identification

(2)

Worst Case &StatisticalTolerance Analysis

(3)

Worst Case &StatisticalTolerance Analysis

(3)

Analysis Process

Goal

To analyze as soon as possible during the design cycle, all admissible

assembly sequences in order to select the optimal one.

Mate & Contact Identification (I)

Definition (D.E Whitney) • A mate is an assembly link that establishes constraints and dimensional

relationships between part.• A contact is an assembly link that supports and fastens the part once it

is located.

Property

Mate and Contact are related to the assembly sequence.

Geometrical variations flow from part to part through mates only.

Benefice• Easy to represent on a graph• Tool for variation propagation

analysis.

Assembly Sequence (III)Assembly Sequence (III)

Stringer

Cleat

Cleat Pannel

M

MM

M

MM

C

C

C

C

Mate

Contact

M

C

1

Assembly Sequence (IV)Assembly Sequence (IV)

Assembly Sequence #1

Lower Floor

Lower Shell

Upper Shell Left

Upper Shell Right

Tool

Door

Upper Floor

Mate & Contact Identification (II)

Tools : Assembly Oriented Graph.

Assembly surfaces

Mate

Contact

PKC1

KC

AOG is a directed acyclic graphical representation of an assembly given a picture of the location dependencies of parts and surfaces. Each node represents assembly surface. Oriented arcs represent mates between two assembly surfaces. The arrow points on the positioned component. Oriented dotted arcs represent contacts between two assembly surfaces and dotted line represents geometrical conditions

Assembly Sequence (V)Assembly Sequence (V)

Propagation Chain Identification

• Inputs : Assembly Oriented Graph, Key Characteristics

• Outputs : Qualitative Assembly Sequence Analysis

• Tools : Propagation Chain

Definition

• A propagation chain is defined by all the mates necessary in order to

perform a Product Key Characteristics.

Property

PKCs quality will be related

to the length of the

propagation chain.

Lower Floor

Lower Shell

Upper Shell Left

Upper Shell Right

Tool

Door

Upper Floor

2Propagation Chain

Assembly Sequence (VI)Assembly Sequence (VI)

Tolerance Analysis• Inputs : Manufacturing Capabilities,Assembly Process, Geometric

Characteristics, PKCs.

• Outputs : Quantitative Assembly Sequence Analysis.

• Tools – Available commercial software (Valisys, CeTol, 3DCS).– In house development (AnaTole).

3

Assembly Sequence (VI)Assembly Sequence (VI)

AnaTole Software• In house development based on TTRS, Variation Model (EADS C.C.R) and

Open Cascade (EADS MatraDatavision).

• Benefits :

– Easy to use without a deep knowledge of CAD system.

– Very close to manufacturing and Design process.

– Over-Constraint Detection and Analysis.

– Statistical & Worst Case Tolerance Analysis.

– Useable as soon as possible in the design cycle (wireframe geometry only).

Method SummaryMethod Summary

1To identify the

major functional requirements

1To identify the

major functional requirements

2To translate the

functional requirements into geometrical

requirement

2To translate the

functional requirements into geometrical

requirement

3To identify

the product’s Key Characteristics

3To identify

the product’s Key Characteristics

4To select an admissible assembly sequence

4To select an admissible assembly sequence

Yes

To

ch

oo

se a

no

the

r a

sse

mb

ly s

eq

ue

nce

To

ch

an

ge

de

sig

n p

rinci

ple

5To select

the Mate / Contact assembly links

5To select

the Mate / Contact assembly links

6 To analyse

the assembly sequence

6 To analyse

the assembly sequence

Are allgeometrical conditions

fulfill ?

Are allgeometrical conditions

fulfill ?

Is it possible to choose another

assembly sequence ?

Is it possible to choose another

assembly sequence ?

Is it possible to improve the manufacturing

capabilities

Is it possible to improve the manufacturing

capabilities

To

imp

rove

M

an

ufa

ctu

ring

ca

pa

bili

ties

Assembly sequencevalidated + tolerance specification

Yes

Yes

No

No

No

Conclusion & Future prospectConclusion & Future prospect

Need to manage tolerance from the functional requirement to ISO

specification based on :• Product Key Characteristics• Assembly processes• Manufacturing Capabilities

Definition & Deployment of a Variation Management Method• Useful for complex product like aircraft.• Used as soon as possible during the design process.• Allowing to select the optimal assembly sequence.

On going Works • Take into account flexible parts in the method• Automatic assembly sequence planning

& analysis.• Wide deployment of the method.