Mechanical Engineering
Models of Product
Development
Mechanical Engineering:
ME30294 – Product Design and Development
Models of product development
Product development = design + development
Design is "the process by which artefacts get the
dimensions they actually have".
Models of the product introduction process are used
to “add structure to a chaotic process”
They help focus attention on important aspects, and
they guide action in the process
Models are divided into descriptive models – that
describe design based on observation – and
prescriptive models – which suggest a best process
Mechanical Engineering:
ME30294 – Product Design and Development
Models of product development
The conventional view: the design process involves a
series of stages from statement of "need" through
concept exploration to detail design
Traditional models of the design process are
sequential and iterative: e.g.
– BS7000
– Pahl and Beitz
– Pugh/SEED
– Ohsuga
Mechanical Engineering:
ME30294 – Product Design and Development
Generic design process model
NEED
CONCEPT DESIGN
DETAIL DESIGN
MANUFACTURE
USE
EMBODIMENT
Mechanical Engineering:
ME30294 – Product Design and Development
DESIGN ACTIVITIES
• Clarify task
• Elaborate the specification
• Identify essential problems
• Establish function structures
• Search for solution principles
• Combine into concept variants
• Evaluate against technical & economic criteria
• Develop preliminary layouts & form designs
• Select best preliminary layouts
• Refine against technical & economic criteria
• Optimise & complete form designs
• Check for errors & cost effectiveness
• Prepare preliminary parts list
• Prepare preliminary production documents
• Finalise details
• Complete detail drawings & production documents
• Check all documents
DESIGN STAGE
SPECIFICATION
DEFINITIVE
LAYOUT
PRELIMINARY
LAYOUT
TASK
DOCUMENTATION
SOLUTION
CONCEPT
DESIGN PHASE
TASK
CLARIFICATION
CONCEPTUAL
DESIGN
DETAIL
DESIGN
EMBODIMENT
DESIGN
TIM
E
UP
GR
AD
E &
IM
PR
OV
E
Pahl and Beitz Model Ref: G Pahl, W Beitz, Engineering
Design: a Systematic Approach, 2nd Ed,
Springer, 1995
Mechanical Engineering:
ME30294 – Product Design and Development
Pugh/SEED design activity model
Reference: S Pugh, Total Design,
Addison-Wesley, 1991
Mechanical Engineering:
ME30294 – Product Design and Development
Theory of Technical Systems
Technical System (TS) Purpose
– Achievement of desired transformation
TS Process Model
– Internal transformation of inputs to outputs
TS Function Structure
– TS in a state of being capable of working
TS Organ Model
– Organ – to realise functions
TS Component Model
– Component – means of realising functions
See separate sheets
Tech. process
TS
Effects Operand
states
Mechanical Engineering:
ME30294 – Product Design and Development
BS7000 model
BS 7000-1:1999 Design management systems. Guide to
managing innovation
BS 7000-2:1997 Design management systems. Guide to
managing the design of manufactured products
BS 7000-3:1994 Design management systems. Guide to
managing service design
BS 7000-4:1996 Design management systems. Guide to
managing design in construction
BS 7000-5:2001 Design management systems. Design
management systems. Guide to managing obsolescence
BS 7000-10:1995 Design management systems. Glossary of
terms used in design management
Mechanical Engineering:
ME30294 – Product Design and Development
BS7000 model
BS 7000-1:1999 Design management systems. Guide to
managing innovation
BS 7000-2:1997 Design management systems. Guide to
managing the design of manufactured products
BS 7000-3:1994 Design management systems. Guide to managing
service design
BS 7000-4:1996 Design management systems. Guide to managing
design in construction
BS 7000-5:2001 Design management systems. Design management
systems. Guide to managing obsolescence
BS 7000-10:1995 Design management systems. Glossary of terms
used in design management
Mechanical Engineering:
ME30294 – Product Design and Development
BS7000:2 design process
Phase of project Process Output
Concept phase
Inception of new/improved product;
formation of team; analysis of
business concepts; formulation/
evaluation/approval of project
Opportunities; Business and
product concepts; Preferred
concept; project proposal;
permission to proceed
Feasibility phase
Planning, research and feasibility
studies -> proposal; develop of
functional spec.; development of
work programme; sanctioning of
project; forming of team
Criteria of acceptability; project
design brief; project and
resource plans; project approval;
preferred option;
roles/responsibility matrix
Implementation
phase
Concept development; outline
design; detailed design; construction/
testing of pre-production design.
Finalisation of design; design for
manufacture; product launch; selling
and use; monitoring “in-use”
Specification for product;
confirmation of performance inc.
reliability/ maintainability;
product package; product
availability; fulfilment of business
objectives; improvements
Termination
phase
Evaluation of project; termination of
project; design support for
decommissioning; disposal of
product
Handover of responsibilities;
continuing liability
Manufacturing stage
Liability starts
Design/development
stage
Internal to organisation
External to organisation
Mechanical Engineering:
ME30294 – Product Design and Development
Design implementation process
Time scales
Cost
Performance
Profitability
Systematic
monitoring
against
design brief
by project
manager
Record
and
control
Verification by:
testing
reviews
repetition
competition
Formal
design
reviews
throughout
the design
process
Validation
by
usage
Evaluation:
customer
in-house
independent
BS7000:2 Design Implementation Process
De
sig
n p
roc
es
s
Itera
tion
Mechanical Engineering:
ME30294 – Product Design and Development
Stage-gate models
Current company models often use “stage-gate”
models, risk management and design review
Stage gate model – Robert Cooper, McGill University
From www.stage-gate.com
Mechanical Engineering:
ME30294 – Product Design and Development
Bombardier model
DETAIL
DESIGN
DEFINE SPEC
OBTAIN ITP
INITIAL
DESIGN
DELIVER TO
CUSTOMER
MANUFACTURE
& ASSEMBLY
TEST, ANALYSE
& CERTIFICATE
concept
review
initial
review
basic
review
compliance
review
external
(customer / supplier)
reviews as required
CONTINUOUS PRODUCT DEVELOPMENT
RISK MANAGEMENT
Mechanical Engineering:
ME30294 – Product Design and Development
Airbus model
M0 M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14
Product idea established
Order released for project
Top level aircraft specification
Definition of basic concept
Concept for product selected
Instruction to proceed (ITP)
Authorisation to offer (ATO)
Go ahead
First metal cut
Begin final assembly
Power on
First flight
Type certification
Entry into service
End development phase for basic aircraft
A321-100 in-service Jan 1994
A321-100 certificate Dec 1993
A321-100 first flight Mar 1993
A321-100 go ahead Nov 1989
A321-100 DBD
PRODUCTION PHASE
IN-SERVICE PHASE
DEFINITION PHASE DEVELOPMENT PHASE
Mechanical Engineering:
ME30294 – Product Design and Development
Risk management
Goal definition
Risk identification Continual monitoring
Budget levels
Risk prioritisation
Modelling relationships
Impact and
probability evaluation
Mitigation and
contingency planning
Mechanical Engineering:
ME30294 – Product Design and Development
Systems engineering VEE model
Used in particular by electrical and computer-
systems engineers, but also by Peugeot and BMW in
their development processes
Distinguishes between systems and component
design
Mechanical Engineering:
ME30294 – Product Design and Development
Systems engineering VEE model
Systems
design
Component
design
Mechanical Engineering:
ME30294 – Product Design and Development
BMW Example
Mechanical Engineering:
ME30294 – Product Design and Development
CAM’s Views
The design of an artefact is driven by the functional
requirements placed upon the artefact by the
customer
Designs that are proposed to meet these
requirements are characterised by solution
principle(s), configuration and physical arrangement.
They are defined within a design space bounded by
constraints
The design process can be viewed as proposing and
developing solution principles within the bounded
design space
Mechanical Engineering:
ME30294 – Product Design and Development
The Product Model
The artefact is described by design parameters and
performance parameters
Design parameters are explicit, definitive or descriptive
– form, dimension, surface
condition, material
properties etc.
– Modelled by drawings,
diagrams, CAD models
Mechanical Engineering:
ME30294 – Product Design and Development
Product Attributes
Performance parameters are judgements, emergent
properties, and indicate how well the design meets
functional requirements
– Analytical, experimental,
mathematical, test,
computational etc.
models are used to
make a judgement
– Obtained by considering
the artefact subject to
loads/external influences
– They are derived or implicit
Mechanical Engineering:
ME30294 – Product Design and Development
Loads and Requirements
Performance parameters are obtained by considering
the artefact in an environment – e.g. subject to loads
and external influences
Performance parameters are used to judge the
performance of the emerging design with respect to
the design requirements, e.g.:
– Test conditions used to assess wear performance
– Analysis used to assess fatigue performance
Mechanical Engineering:
ME30294 – Product Design and Development
Constraints and Design Space
The product is defined within bounds imposed by
constraints
– Some constraints are global - e.g. material limitations;
some local to the artefact - e.g. manufacturing process
constraints
The design space is defined by:
– the feasible values for design parameters;
– permissible values of performance parameters
The boundaries of the space are fuzzy/uncertain as are
our methods of estimating performance parameters
Mechanical Engineering:
ME30294 – Product Design and Development
Model Transformation
The product development process involves developing multiple models representing aspects of the product
In particular:
– Design parameter, functional requirement and constraint models are developed and refined
– Assessments and judgements about the performance parameters are elaborated
– Auxiliary models (e.g. computational, mathematical) are created as required to help in estimation of performance parameters
Mechanical Engineering:
ME30294 – Product Design and Development
Model Transformation
Function/ constraints
Loads
Design parameters
Auxiliary models
Performance parameters
Time
The Design Process
Mechanical Engineering:
ME30294 – Product Design and Development
Create information for manufacture
and testing
Plan Manufacture
Test
Ohsuga’s Process Model
Conceptual
Design
Preliminary
(Embodiment)
Design
Detail
Design
Requirements
Build
Model Model 1
Modify and
Refine
Analyse and
Evaluate
Model 2
Modify and
Refine
Analyse and
Evaluate
Model n
Modify and
Refine
Analyse and
Evaluate Product
Drawings, CAD
models etc.
Models for
evaluation
purposes
Mechanical Engineering:
ME30294 – Product Design and Development
Estimating performance parameters
The principal objective of design analysis,
experimental work and prototype test is to predict
and then validate the performance of the new
product.
A hierarchy of techniques is used:
– Classical analytical techniques
– Computer-based analysis
– Bench/laboratory test
– Prototype test
Mechanical Engineering:
ME30294 – Product Design and Development
Computational analysis
Mechanical Engineering:
ME30294 – Product Design and Development
Log (cost)
Log (error)
Error versus cost
E.g. Aerodynamic
coefficients; fatigue life
A: Classical analytical
techniques.
B: Computer-based
analysis - CFD, FEA +
damage accumulation
Bench/laboratory test:
servo-hydraulic test rig;
wind tunnel
Prototype test: track test;
flight test
A
B
C D
Mechanical Engineering:
ME30294 – Product Design and Development
Alternative techniques
Adapted from:
http://www.cds.caltech.edu/conferences/1997/vecs/
tutorial/Examples/Cases/777.htm
Log (cost)
Number of
conditions
Computational
analysis
Physical test
Mechanical Engineering:
ME30294 – Product Design and Development
Discussion
P Gerson suggests there are 5 basic approaches to
representing the process
Mechanical Engineering:
ME30294 – Product Design and Development
The traditional view - design “thrown over the
wall” from department to department:
– Leads to delay before problems are corrected.
– Specialist expertise is applied once decisions have
been made
Concurrent engineering compresses the process
through parallel activities:
– Specialist expertise is applied early in the design
process.
Concurrent engineering
Mechanical Engineering:
ME30294 – Product Design and Development
David Dilt – Owen at Vanderbilt
Mechanical Engineering:
ME30294 – Product Design and Development
TIME
• individuals
• slow changes
• long lead time
• lower quality
S
Sequential Product
Development
Product Definition Requirements Definition Process Definition Production & Distribution
Embodiment Concept Detail
F
Errors, Changes and Corrections
S
• teams
• fast changes
• short lead time
• higher quality
Concurrent Product
Development
Requirements
Definition
Product Definition
Concept
Embodiment
Detail
Process
Definition
Production
& Distribution
F
CE Life Cycle Time Time Saved
Errors,
Changes
and
Corrections
Mechanical Engineering
Armand Hatchuel’s
C-K Theory
Mechanical Engineering:
ME30294 – Product Design and Development
Hatchuel C-K model
Formal distinction
between spaces of
concepts “C” and
knowledge “K”
All propositions of K
have a logical status
(e.g. true/false)
Concepts are
propositions with no
logical status
Models the dynamics of
design as expansion of
C and K spaces
C K
C K
The
Design
Square
Expansion by
deduction or
experiment
Disjunction/partition/validation
Conjunction/activate
Expansion
by partition
or
inclusion
Mechanical Engineering:
ME30294 – Product Design and Development
Conclusions
Models of the product introduction process are used
to explain or “add structure to a chaotic process”
The process involves a series of stages from
statement of "need" through concept exploration to
detail design
A number of model variations exist
Concurrent engineering compresses the process
time scale by overlapping steps
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