Engineering Design Methodology Principles and Guidelines of Embodiment Design
Dr.-Ing. Alex Brezing
September 3, 2012
The Sirindhorn International Thai-German Graduate School of Engineering, KMUTNB
Institute for Engineering Design, RWTH Aachen University
2
Review - Overview
„method knowledge“
„rules knowledge“
• Requirements list
• Function structure
• Effects structure
• Principle solution
• Selection of a solution
Working out solutions
“Embodiment Design”
• Basic embodiment
design rules
• Principles of embodiment
design
• Design for X
The Sirindhorn International Thai-German Graduate School of Engineering, KMUTNB
Institute for Engineering Design, RWTH Aachen University
Embodiment Design
3
1. Process View
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Institute for Engineering Design, RWTH Aachen University
General Process of Engineering Design
WHAT? Problem exploration
and documentation
HOW? Identify working
principle / concept
GO! Define and
document
geometry
4
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Institute for Engineering Design, RWTH Aachen University
5
Steps of Embodiment Design 1
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Steps of Embodiment Design 2
6
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Institute for Engineering Design, RWTH Aachen University
Embodiment Design
7
2. Implications on CAD
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8
CAD Strategy?
• qualitative -> quantitative: parametric modeling
• abstract -> concrete: use skeletons
... allowing for a top-down/bottom-up approach
• main functions -> auxiliary functions
• rough -> detailed
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Institute for Engineering Design, RWTH Aachen University
9
Parametric CAD: qualitative -> quantitative
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Institute for Engineering Design, RWTH Aachen University
Use skeletons: abstract -> concrete
10
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Institute for Engineering Design, RWTH Aachen University
Top-down / bottom-up: rough / detailed
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Institute for Engineering Design, RWTH Aachen University
Top-down / bottom-up: main / auxiliary
12
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Institute for Engineering Design, RWTH Aachen University
Embodiment Design
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3. Embodiment Elements
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Institute for Engineering Design, RWTH Aachen University
Embodiment Elements
The embodiment of a technical artefact is made up of embodiment
elements
Embodiment elements can have different degrees of complexity:
• points, corners, bits,
• line pieces, edges,
• partial surfaces,
• components,
• assemblies,
• machines, devices, apparatus
In a technical system, an embodiment element is the smallest element
that can still be influenced by the embodiment design.
14
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Institute for Engineering Design, RWTH Aachen University
Levels of Complexity: Embodiment Elements
Level Subsyst. emb. el. Explanations Example Level Subsyst.
emb. el. Explanations Example
1 corner, point
intersection point of component edges, partial component surfaces taping off to a point
6 part
a part of a technical artefact that cannot be further disassembled
2
edge, 1st and 2nd order, area boundary
boundary of an area, edge- or tangent-shaped transition between two partial surfaces (1st or 2nd section discontinuous)
7 assembly
independent (own cradle) functionable subsystem consisting of at least two components
3
partial surface, working surface
parts of the surface of a component
8 machine, device, apparatus
technical system for realization of a certain energy, material or information conversion process
4 working surface pair
interacting partial surfaces of two components
9 systems, installa-tions, units
technical system consisting of several machines, devices and/or apparatus
5 subbodies
subbodies which can be imagined for the composition of a component
10 technical system
complex technical systems, e.g. flight system (aeroplanes, airport, air traffic control), vehicle systems (car, road) etc 15
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Institute for Engineering Design, RWTH Aachen University
Plant: Examples
People-Mover
System
Baggage conveyor
Refinery
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Assemblies and Components
Source: MZ-B Vertriebs GmbH, www.motorradtechnikbarnim.de
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Embodiment Design
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4. Design Rules - Overview
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Guidelines („design for X“)
Basic
Rules
Principles
• “Simple, Clear, Safe”
• Violation will result in bad products
• Affect function structure, concept
and embodiment
• 5 kinds of principles
• If applicable
• Affect concept and
embodiment
• Countless catalogues
• If applicable
• Affect embodiment
Design Rules
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Rules – apply when?
Principles: often connected to principles, consider during rough embodiment design
Guidelines: mostly relevant during detailing
Basic rules: not only relevant for product properties but also documentation
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Embodiment Design
21
5. Basic Rules: Clear
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• Clear assignment of functions and their inputs/outputs
• (Mathematically) clear interrelations of inputs and outputs
(applicable also on loads and resulting stresses)
• Enforce the correct operation
• Complete documentation (incl. production drawings)
• Assembly sequences that prevent wrong assembly, transport
aids
• Clearly defined intervals for service, inspection ...
• Identify materials, clear division between incompatible
materials
Clear Embodiment Design
Referring to the contents of the guideline about embodiment design 22
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“Clear” Assignment of Functions
Clear bearing arrangement
clear separation of radial and
axial forces)
No clear bearing arrangement
(division of radial and axial forces)
23 acc. to Pahl/Beitz
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Embodiment Design
24
6. Basic Rules: Simple
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• A low number of procedures and components for the
realization of the function
• (Mathematically) Simple geometric shapes
• Use symmetry
• Obvious MMI
• Few production procedures
• Easily identifiable parts
• Uncomplicated assembly procedures
• Simple error detection
• Materials suitable for production processes and operation
Simple Embodiment Design
Referring to the contents of the guideline about embodiment design 25
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Simple: Slide Valve
strive for
simple shapes
casting
braze parts 26
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Embodiment Design
27
7. Basic Rules: Safe
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Safety: Definition
Is this car save??
Yes: It meets NCAP crash regulations
Will I survive this accident? 28 acc. to www.focus.de
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Definition: Safety
Risk limit
is the largest still acceptable system-specific risk relating to a particular technical process
or situation
Protection
is the reduction of risk by suitable means to reduce the frequency of the occurrence or
the extent of damage or both
Safety
is a state in which the risk is smaller than the risk limit
29 Quelle: DIN EN 292
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Safety Aspects of a System
energy flow
material flow
sequences
danger
safe
control
safe
regulation
safe
monitoring
design
measures
safety measures
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• Direct safety
Choosing a solution that precludes danger from the outset (in
general to be strived for)
• Indirect safety
The danger is isolated via construction of special protective systems
and arrangement of protective barriers
• Warnings
Dangers are pointed out and made clear (only to be used as an
additional measure)
Safe Embodiment Design
Consider DIN 31000 and DIN/EN 292 Parts 1 and 2! 31
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Example: Fail-Safe
Crane brake:
safety brake, has to be vented
for lifting or lowering of the
load.
Compression spring:
also ensures jaw contact force
in case of a fracture.
32
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Redundant Arrangement: Protective Devices
Principle redundancy Parallel connection
Protective devices:
• safety valve (SV)
• bursting disc (BD)
SV
SV
BS
SV
33 acc. to Pahl/Beitz
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Embodiment Design
34
8. Principles: Force Transmission (Direct and Short Force Transmission Path, Principle of Matched Deformations, Principle of Balanced Forces)
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Institute for Engineering Design, RWTH Aachen University
Target:
• minimum use of materials
• minimum resulting
deformations
reached, if:
• only tension or
• compressive forces
are transmitted
Direct and Short Force Transmission Path
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uniform stress-level and
thus optimal utilization
of the material
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Direct and Short Force Transmission
All three transmission units have the
same load and the same stress
(rectangular cross section of the same
thickness)
direct force transmission
indirect but closed force
transmission
indirect force transmission
1
2
3
36 acc. to: Ehrlenspiel
1
2
3
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Direct and Short Force Transmission
1
2
3
37 acc. to: Meißner, Hoenow
2 3
The clevis represents variant 2 and
the crane hook represents variant 3
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Direct Force Transmission: Relief Notches
relief notches support the
direct flow of forces
38 falsch richtig wrong right
flow of
forces
relief notches
notch zone
notch plane
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Matched Deformation: Drive Shaft
same angle of torsion of the gears
due to matched deformation of the
shaft sections by an asymmetric gear
arrangement
symmetric gear arrangement ensures
synchronous running
synchronization problems due to
unsymmetrical gear arrangement
39 Quelle: Pahl/Beitz
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Principle of Balanced Forces
The forces acting outwards
neutralize one another
acc. to Pahl/Beitz 40
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Embodiment Design
41
9. Principles: Division of Tasks
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Principle of the Division of Tasks
• Clear production processes
• Clear assembly operations
• Increased safety (clearness)
• Number of components
• Number of parts
• Spatial requirements (interfaces)
• Increased weight
One function carrier
for each function
One function carrier
for several functions
The dilemma
42
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Embodiment Design
43
10. Principles: Self-Help (Self-Reinforcing, Self-Balancing)
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Self-Reinforcing: Tyre Valve
The sealing force of the valve
and the tyre on the rim increases
with increasing tyre pressure
44 acc. to: Pahl/Beitz
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Self-Reinforcing: Seals
Internal pressure, P,
increases the sealing
effect
45 acc. to: Pahl/Beitz
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Self-Reinforcing: Drum Brake
Brake with two brake cams: Two
brake shoes running up
Brake with two brake cams, self-
centering
Standard design: one brake
shoe running up and one
running down
46 acc. to: Niemann
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Self-Balancing: Turbine Blade
Conventional solution,
the blade stands straight Self-balancing:
due to the leaning of the blade the centrifugal
force counterbalances the bending stress
47 acc. to: Pahl/Beitz
Potential of increased
performance by
enlarged blades!
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Embodiment Design
48
11. Principles: Stability/Bi-Stability
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Common examples of Bi-Stability
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Bi-Stability principle
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Energy Storage Medium
spring, pressure vessel, heat
accumulator, Hook-medium
stable Low energy level
stable Low energy level
labile High energy level
Auxiliary Energy
• potential
• kinetic
• electrical
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Rocker I
stable starting
position labile balance second stable
position
Energy Level
51
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Embodiment Design
52
12. Design Guidelines: Df Cutting
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Cutting
Turning Millling
53
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Influencing Factors
Manufacturing Costs
material Manufacturing method
machine
(new/old)
setup-, process-, auxiliary time
tool
wear
dimension
quantity
tolerances
surface
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Costs
0123456789
101112131415161718192021
6 10 14 20 24 28 32 36 40 45 50
Co
sts
Bore diameter d [mm]
Drilling on boring mill
Drilling , opening, reaming
drilling, opening
drilling
Boring mill
Drilling machine
55
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Fine machining of cogwheels
0
1
2
3
4
5
6
7
8
Co
sts
56
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Turning I
shaped tool standard tool
consider the
necessary tool
runout
target: improve quality
Use simply
shaped tools
target: improve quality
inappropriate appropriate
57
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Turning II
internal turning:
avoid grooves
and narrow
tolerances
target: reduce effort
provide
adequate
chucking
surfaces
target: improve quality
inappropriate appropriate
58
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Embodiment Design
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13. Design Guidelines: Df Assembly
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Course of Assembly
ordered
storing,
stacking
storing
the parts
identifying,
seizing,
moving
the parts
handling
the parts
adjusting
and
aligning
for joining
positioning
the parts
form fit and
material
fitting,
joining
elements
joining
the parts
balance of
tolerances,
adjustment
of clearances
setting,
adjusting securing
ensure a lasting
function of the
joining
controlling
carry out set-
actual
comparison,
correct
deviations 60
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Building Structure for Ease of Assembly
acc. to Pahl/Beitz 61
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Design for Ease of Assembly
acc. to Pahl/Beitz 62