Ideation

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SPECIFICATIONS, CONCEPT GENERATION AND SELECTION
SUMMARY
QFD
Functional Decomposition Morphological Analysis
Feasibility judgment Technology readiness Go/no
go screening Decision matrix method
Concept 1 Concept 2 Concept 3 Concept n
Required functionality
Final concept
Need

• Ideation
• Brainstorming
• Patents
• Reference (Books, Trade Journals)
• Experts help

Design review 1
Design review 2
2
IT IS TIME TO START THE NEXT DESIGN PHASE THE
DETAILED DESIGN

• Specification Development / Planning Phase
• Determine need, customer and engineering
  requirements
• Develop a project plan
• Conceptual Design Phase
• Generate and evaluate concepts
• Select best solution
• Detail Design Phase
• Documentation and part specification
• Prototype evaluation
• Production Phase
• Component manufacture and assembly
• Plant facilities / capabilities
• Service Phase
• Installation, use , maintenance and safety

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WE NOW NEED A NEW TOOL CAD
Quality function deployment Gantts charts
Critical path method Ideation Brainstor
ming Patents Reference materials Functional
decomposition and morphological
analysis Sketches Feasibility
judgment technology readiness
assessment Go/no-go screening Decision matrix
method (with pair-wise comparison) CAD
Specification Development / Planning Phase
Conceptual Design Phase Concept generation
Conceptual Design Phase Concept selection
Detailed Design Phase
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EVOLUTION OF CAD TOOLS
1970s
Manual drafting Electronic drafting board
1980s
Wire frame geometry
Surface geometry
1990s
Solid geometry
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MODERN CAE TOOLS
COMPUTATIONAL FLUID DYNAMICS
FINITE ELEMENT ANALYSIS
CAD SOLID, PARAMETRIC, FEATURE BASED
..
MOTION ANALYSIS
..
Computer Aided Design (CAD) is at the hub of
other Computer Aided Engineering (CAE ) tools
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IN MME2259a WE USE SolidWorks CAD SOFTWARE
You can burn your installation DVD on any lab
computer
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www.eng.uwo.ca/designcentre
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WHAT IS A SOLID, PARAMETRIC, FEATURE BASED CAD?
PARAMETER
SOLID GEOMETRY
BASE FEATURE (POSITIVE SOLID)
CHILD OF BASE FEATURE (NEGATIVE SOLID)
panel 01.SLDPRT
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TO TAKE FULL ADVANTAGE OF A SOLID, PARAMETRIC,
FEATURE BASED CAD WE NEED TO UNDERSTAND HOW TO
USE IT. WELL SPLIT OUR REVIEW INTO MODELING
PHILOSOPHY SKETCHES FEATURES PARTS ASSEMBLIES
DRAWINGS
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MODELING PHILOSOPHY
There is one factor of model building philosophy
which stands above others what matters the most
is what we want to do with the final geometry.
Model geometry is not created to stay it is
meant to be changed. We need to understand
which features we would like to drive and control
some other ones, what portions are to be
modified, what are the boundaries of
modifications and anticipate how the model is
going to be developed further. All of this has
to be incorporated in the model history and
developed to a state where the model behaves
the intended way. We call this The Design Intent.
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MODELING PHILOSOPHY
The objective is not only to arrive to the
destination build the final geometry but to
walk the journey towards it. Road to the
destination will teach us the reasons why and
after arriving to the destination we will start
to understand. There are no shortcuts or quick
leaps there. How does this all reflect on the
model building techniques? The model has to be
able to easily handle changes down the road (and,
for sure, there will be changes). Changing basic
dimensions, changing number of features, changing
shape the model should handle all such
requests.
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MODELING PHILOSOPHY
3D solid modeling software usually creates 3D
geometry by taking a 2D sketch and extruding,
revolving, sweeping and blending it in a third
direction which results in a 3D feature.
Both the sketch and the feature are parametric
dimension driven. Changing the values of
dimensions (if they are meaningful) forces the
geometry to assume new shape.
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MODELING PHILOSOPHY
Proper feature geometry starts with proper
parametric sketch. Sketch is the entry point to
incorporate design intent in the model. Each 2D
sketched entity will become a portion of a 3D
feature, e.g. lines will be converted to
surfaces, endpoints become edges, circles will
become cylinders, etc. 90 of all errors are
errors in sketches!
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MODELING PHILOSOPHY
The way that geometry is built does not
necessarily reflect manufacturing process of a
real, physical part. It rather resembles a
step-by-step approach by adding and subtracting
material. For example, while in real life a
machined part is created always by removing
material only, 3D modeling combines solid
protrusions (adding) and cuts (removing) to build
geometry. This is why the dimensioning scheme
on model cannot effectively replicate
manufacturing dimensioning scheme.
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SKETCHES
Sketch can be placed on a reference place or a
flat face of already existing geometry. If
possible, use underlying geometry to position
sketch entities
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SKETCHES
Construct the first sketch on the first reference
plane Extrude in positive direction Keep
sketches simple Use sketch relations where
possible Test relations by rebuilding sketch with
different dimensions Constrain all sketches Give
sketches some meaningful names
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SKETCHES
Sketch should not contain more than 12-15
geometric entities (lines, arcs, conics, etc.)
included construction geometry (centerlines,
sketched points). The more complex the sketch
the harder is to control it with minimum number
of dimensions. Less is more. Sketch implicit
rules (assumptions or constraints) should be
maximized to simplify the geometry. Abundance of
dimensions is worst than their scarcity. The
more dimensions we have to drive a sketch, the
easier it is to omit one when modifying feature
geometry. This is one of the most frequent
mistakes.
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SKETCHES
No symmetry relations
With symmetry relations
Use relations in sketches
plate 001.prt
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SKETCHES
Use relations in sketches
plate 001.prt
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SKETCHES
sketch
extrusion
pattern
Use construction geometry to create intelligent
sketches. Here we want to control the bolt
circle diameter of three holes placed in 120º.
increments about the center axis of a flange.
flange.prt
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SKETCHES
Massage the sketch change values of crucial
dimensions and update it to find out if it
behaves the way you like.
Use underlying parent features for proper
alignments of sketches. This will create
parent-child relationship between features. Use
consciously for controlling children through
parents
flange.prt
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SKETCHES
Exaggerate the sketch when creating features.
Say we would like to sketch a line 1º. from
vertical. It is easier to sketch it about 10º
from vertical, dimension it and modify the
dimension to 1 deg, than try to sketch it almost
vertical, dimension it and expect the system to
accept the value. The systems implicit rules
will kick-in assuming the line should be vertical
and we will have hard time to overrule it.
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SKETCHES
YES
NO
Add details to features, not to sketches (also
see the next slide)
cup.prt
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SKETCHES
BASE FEATURE
FILLET FEATURE
cup.prt
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FEATURES
Main geometry
Half detail
Detail
Create main geometry This is usually the main
volume - the biggest feature, although it does
not have to be. This feature becomes parent to
majority of following features. Add
half-detail These will be features like shells,
construction ribs, cutouts, etc. Finally create
fine detail These features are usually
pick-and-place features such as rounds, chamfers,
drafts, cosmetic grooves, etc.
plate with boss.prt
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FEATURES
Cosmetic feature
Cosmetic feature
YES
NO
When creating features avoid undesirable
parent-child relationships. Features representing
cosmetic (fine detail) geometry should not be
parent of any subsequent features, unless driven
by design intent
plate with boss.prt
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FEATURES
YES Sketch on reference plane
NO Sketch on face
When orienting the sketch use construction
planes, rather than solid features in case the
solid feature will be later redefined and its
children fail by losing their references.
pipes.prt
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FEATURES
Axis of rotation
Sketch
When creating features of one kind (e.g.
revolved), use the same construction plane for
sketching and orientation. Sketch the entities
always on the same side of the centerline of
rotation (e.g. left-hand)
pipes.prt
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FEATURES
NO
Avoid unattached geometry (two or more solid
bodies within part). The part geometry is by
definition a continuum and should remain
continuum anytime during the history of feature
creation.
pipes.prt
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PARTS
All part features should be unsuppressed when
releasing (making the final version) the
part. Part must have material property and color
assigned Part must not be in roll-back
mode Features and sketches must be named All
sketched must be fully defined Use mm, N, s, K
units ( important for analysis) Zoom to fit and
position in isometric view before saving
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ASSEMBLIES
Assembly of 3D solid modeling software in general
does not contain assembly geometry. The
assembly contains components (i.e. parts and
lower level assemblies) assembled together in the
intended manner. Assembly contains information
on where to find parts and how are parts oriented
relative to each other (mated). The only
features that can be defined in assembly are
negative features (cut)
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ASSEMBLIES
When retrieving the assembly (opening assembly
file), CAD program needs the following
information - BOM (Bill of Material)
structure This information is stored within
assembly file and is used to retrieve all listed
components. It is obvious, that the system has
to be able to see and retrieve all components
regardless where they reside on the network. -
Mating information How feature surfaces of
individual components are assembled - mated to
their parent components. - Feature information
Assembly cuts (in case they have been created)
and parts/features that are being intersected by
them.
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ASSEMBLIES
BOM
MATING INFO
ASSEMBLY FEATURE (CUT)
shear pin.sldasm
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ASSEMBLIES
Mating can use parts geometry or reference
geometry
bracket002.sldasm