The Desgin Process & the Role of CAD
Transcript of The Desgin Process & the Role of CAD
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The design process model
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Knowing design process allows better
understanding of computer use in design.
Existence of a variety ofdesign processmodels.
All have the same principles: step-by-step flow.
The need to use computers grows as
designing has become more challenging:
Low-cost (cheaper), reduced time-scales (faster),
and quality (better).
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The design process modelcontd
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Types of design model
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There is a variety of representations needed indesign.for`preliminary layouts' and `complete detail drawings'.
The designer uses a host of different modelsdepending on the property of the design is to be modeled, and who or whatis the target, orreceiver, for any communication
Need to model the;
function of a design,
its structure (how the various parts go together),
the form or shape of the component parts, and
the materials, surface condition and dimensions that arerequired.
can form mathematical models, or computer-based representations,to assist in the evaluation of a design.
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Form and Structure
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Form;of particular importance in engineering,the most appropriate method of representing these hastraditionally been graphical.drawings of form:
defining the shape and arrangement of the component parts ofthe design.
Structureconcerned with the structure of the assembly of standardelements to form a design,
with the way these elements are connected together, and withthe flows (e.g. of energy or material) between parts (this approachis often called a systems engineering approach).E.g.. electric or hydraulic circuit design, or the design of processplant,
diagrams:showing structure, or system arrangement.
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Design communication
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In order for any communication to besuccessful, the `language' that is employedmust be agreed and understood by all thoseinvolved.
The complexity of design in many domains,and the crucial necessity to avoidmisinterpretation and ambiguity in instructinghow something must be made, the design models must conform to agreed
standards that define the syntax of the languages
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Modeled properties in designvia Drawing
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the propertiesmodeled by designersin designingautomotive engine
components
The purpose ofdrawings is torepresent thoseattributes ofengineering productsthat must be definedin order for the
products to be made.
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Modeled properties in designvia schematic diagram
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the propertiesmodeled by designersin designing electronic
circuit.The purpose ofdiagrams is torepresent thoseattributes ofengineering productsthat must be definedin order for theproducts to be made.
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Application of design models
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form andstructure:(predominant modeledproperties in design).
actions to be taken with the design information bythe receivers: 2 main classifications
generative actions, to generateinformation from the model foruse downstream of the design
process, progressing to itsmanufacture
evaluating actions,
taken to assess the
properties or merit ofthe design .
extraction of information from the design representation, and the
combination of this with further information to form a new model
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Model transformations in design
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Model transformations in design
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The evaluation of the connecting rods which connect the crankshaftof an
automotive engine to its pistons.
Connectingrod
crankshaft
piston
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Application of design models
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A design analyst might use this for thefollowing assessments: visual assessment, by inspection of the drawing or
CAD model, to ensure that there are no obviousweak areas;
an assessment of the mass of the components, byanalysis using the CAD model;
an evaluation of loads in the components, byconsidering them as parts of a mechanism, asshown in the figure.
an evaluation of stresses, for example using a finiteelement analysis model as in figure.
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Application of design models.
contd
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Detailed drawingsof
the componentsof the design.
information
extraction
ToolingControl
of production
machines
At a later stage of thedesign process
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Modeling using CAD
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Designers construct a series of models of various aspects of thedesign using a number of representation techniques.
Sequentially or concurrently, others involved in the evaluation ofthe design and in the manufacture of the product extractinformation from these models and, in the process, form newmodels to assist them in their work.
Ideation(abstract)
Realization(concrete)
the design is progressively refined
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The use & development of models in design
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The figure shows models of the information required in a concurrent engineering process for themanufacture of a product the form, dimension, surface condition, structure and so on, being
developed as the core of the design process.
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The use & development of models in design.
Contd
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In parallel, the following are also developed: models of the functional and other customer
requirements for the design, because these may alsodevelop and change as the design progresses;
models of constraints on the design, imposed forexample by available materials and manufacturingprocesses;
models of loads imposed on the design; models used to evaluate the performance of the
design for example, for stress or thermal analysis,or for aerodynamic assessment.
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The aim of CAD
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Using computers for
modelingand
communicationof designs.
to automate/assistin such tasks as
the production of drawingsor diagrams
and the generation oflists of parts in a design .
to provide new techniqueswhich give the designer
enhanced facilitiesto assist in thedesign process
Basic Level Advanced
often used together
The degree of sophistication of CAD
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ContdThe aim of CAD
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design models are beingdeveloped/refined throughout
the design process
applied at various stages to the;a) evaluation of the design,
b) generation of information for manufacture
Model1
Model
Model2
Model3
Modelx
CAD shouldinvolve thedevelopment of acentral designdescription.
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A CAD system architecture: The
Integration
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CADsystem
Hardware Software
~ the computer and
associated peripheralequipment;
~ computer program(s)
that run on thehardware;-> the data structure createdand manipulated by thesoftware;
~ human knowledgeand activities.
CAD systems have been described in very generalterms. More specifically, they can be thought of ascomprising:
.
Mindware
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CAD system software
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The software normally comprises a number ofdifferent elements or functions that processthe data stored in the database in differentways.
model definition: for example, to addgeometric elements to a model of the form ofa component;
model manipulation: to move, copy, delete,
edit or otherwise modify elements in thedesign model;
picture generation: to generate images ofthe design model on a computer screen or on
some hardcopy device;
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CAD system software
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user interaction: to handle commands input by theuser and to present out-put to the user about theoperation of the system;
database management: for the management of thefiles that make up the database;
applications: these elements of the software do notmodify the design model, but use it to generateinformation for evaluation, analysis or manufacture;
utilities: a `catch-all' term for parts of the softwarethat do not directly affect the design model, but modify
the operation of the system in some way (e.g. toselect the color to be used for display, or the units tobe used for construction of a part model).
These features may be provided by multiple programs operating on acommon database, or by a single program encompassing all of theelements.
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CAD Software
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An example of Production Control sheet
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Tooling
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Interference checking
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Stress analysis
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An example of CAD models
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