Computeraided product and assembly line design

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Computer-aided product and assembly line design

• Pierre De Lit
• Department of Applied Mechanics
• Université Libre de Bruxelles

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What will we talk about ?

• Introduction
• Description of the methodology
• Product structure and analysis
• Assembly modes and techniques
• Line layout
• Conclusions

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What will we talk about ?

• Introduction
• Description of the methodology
• Product structure and analysis
• Assembly modes and techniques
• Line layout
• Conclusions

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The aim is to design mixed models hybrid assembly
lines

• Multivariant
• Different kinds of stations
• Manual
• Dedicated/Robotized

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Fundamental Principles

• Product and assembly line design is too difficult
  to be done fully automatically but also to be
  done manually
• We develop a set of tools to aid the designer to
  test many alternatives
• The designer always keeps control of the design

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Line design is a constrained optimization problem

• It is important to leave the constraints floating
  as long as possible
• The constraints must be released as much as
  possible

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What will we talk about ?

• Introduction
• Description of the methodology
• Product structure and analysis
• Assembly modes and techniques
• Line layout
• Conclusions

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The methodology is subdivided into three main
modules
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Available information
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Software and Database interaction
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What will we talk about ?

• Introduction
• Description of the methodology
• Product structure and analysis
• Assembly modes and techniques
• Line layout
• Conclusions

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Complexity Explosion
A global multi-variant approach on 81 variants
is rather impossible
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Complexity Explosion a solution

• But 81 3333
• The complexity explosion is caused by the
  combination of small numbers of variants
• So if we treat each module  separetly, the
  problem is reduced to four 3 variants analyses,
  which is a lot easier.

Product division into Functional Entities (FEs)
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The product is decomposed into Functional
Entities

• The FE must correspond to a product functionality
• The number of variants of a FE is rather small
• The product must be able to be assembled as a
  combination of FEs
• A FE may be composed of a single part

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The product is decomposed into Functional
Entities

• The variants of the product are described as a
  combination of variants of FEs.

FEs
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Resulting product analysis
FEs allow the introduction of the product
modularity in the analysis

• The product is analyzed FE by FE
• Two levels
• A first level related to the assembly of the FEs
  to each other
• A second level related to the assembly of the FE
  itself

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Product definition and analysisGeneric and
Variants

• For FEs, SAs, or components, we define a
  fictitious generic element representing it
• The generic element is particularized into
  several variants
• The links between the components are links
  between generic ones

If the generic element is well designed, its
treatment should be applicable to all of its
variants
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Product definition and analysisGeneric and
Variants
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User entries and resultsProduct and FE analysis
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What will we talk about ?

• Introduction
• Description of the methodology
• Product structure and analysis
• Assembly modes and techniques
• Line layout
• Conclusions

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Basic principles

• The features of the parts (fragility,
  flexibility) related to the choice of the
  operating modes and techniques are affected to
  the generic elements
• The variants of a generic element should be
  assembled the same way (same interfaces between
  parts...) to systematize the use of a single
  piece of equipment for a generic element.
• The similarities between equipment are maximized
  for a FE

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Steps of the methodology

• Technique choice
• Operation characterization
• Mode preferences (technical requirements)
• Predetermination and quantification of the needed
  devices
• Feeding operation
• Mode preferences (economical)
• Precedence constraints

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User entries and resultsOperating modes and
techniques
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What will we talk about ?

• Introduction
• Description of the methodology
• Product structure and analysis
• Assembly modes and techniques
• Line layout
• Conclusions

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The line layout takes the modularity into account

• Each FE is associated to a merely independent
  section of the line (called workcenter)
• The line is divided into real workcenters, the
  optimization of the balancing stays a global one.

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The line layout takes the modularity into account
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Workcenters are defined to allow more flexibility

• Line is subdivided into workcenters with
• a cycle time,
• associated FEs,
• a number of stations
• the links between this workcenter and the other
  ones

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The links between workcenters define a line
topology
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Line Balancing (LB)

• According to the link type, the operations (FE)
  affected to a WC may be allocated to another one.

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Optimization criteria for LB
Possible solutions of the problem are compared
with Promethee II, according to weights defined
by the user

• Balance
• Cost
• Reliability

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General methodology

• set the desired workcenters, and for each of
  them
• assign tasks into workcenters, dealing with
  precedence graph,
• set the desired number of stations,
• set the desired cycle time,
• set the preferences,
• set the desired links between workcenters,
• balance the whole plant (set of workcenters),
• position workcenters and workstations,
• check for material handling problems, flows, ...
• evaluate the solution thanks to a simulation
  package
• if no satisfying solution is obtained
• exchange tasks between workcenters
• exchange links between workcenters

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User entries and resultsTransfer selection and
Line layout
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What will we talk about ?

• Introduction
• Description of the methodology
• Product structure and analysis
• Assembly modes and techniques
• Line layout
• Conclusions

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Let us conclude

• Product and assembly line design is decomposed
  into three modules
• Functional entities are defined by the designer
• There is a feedback between these modules to
  improve the line and product design
• The designers intervention is a key of the
  proposed method