the desgin process & the role of cad

7/31/2019 The Desgin Process & the Role of CAD

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The design process model

The design process & the role of CAD1

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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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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