1.fundamentals of cad [compatibility mode]

7/24/2019 1.Fundamentals of Cad [Compatibility Mode]

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1.Fundamentals of CAD

Prof. Nagaraj A Raikar

Definition of CAD: Computer Aided Design

Computer Aided Design can be defined as the

use of computer methods to develop the

geometric model of the product in three

dimensional form, such that the geometric

and manufacturing requirements can be

examined.

CAD can also be defined as the Creation,

modification, analysis & optimization of new

component using a computer.


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CAM: Computer Aided Manufacturing

CAM can be defined as the application of

computers to plan, process, manage and

control various operations in a manufacturing

organisation either with direct or indirect

computer interface with available resources.

CAM has two broad categories

Computer Manufacturing & Control Manufacturing Support Application

Product cycle for conventional manufacturing

environment

Customers and

markets

Order new

equipment and

tools

Product

concept

Design

engineeringDrafting

Process

planning

Production

scheduling

ProductionQuality control

The product cycle


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Customers

and markets

Order new

equipment and

tools

Product

concept

Design

engineeringDrafting

Process

planning

Production

scheduling

ProductionQuality control

CAD Computer aideddrafting and

documentation

Computer aided

process planning

Computerized

scheduling, material

requirements planning

and shop floor control

Computer controlled

robots, machine, etc.

Computer aided quality

control.

The impact of computer in product cycle

Product cycle in computerised manufacturing environment

Computer Aided Design (CAD)

Computer-aided design (CAD) can be defined as the use of

computer system to assist in the creation, modification, analysis, or

optimization of a design.

Reasons for implementing a computer aided design systems:

1) Increase the productivity of the designer.

2) Improve the quality of the design.3) Improve communications; It provides better engineering

drawings, fewer drawing errors, better documentation of thedesign and greater legibility.

4) Create a database for manufacturing; In the process of creatingdocumentation for the product design most of the required database to manufacture product is created. Such as, geometriesand dimensions of the product and its components, materialsspecifications for components, bill of materials etc.


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Need of CAD

There are 5 basic reason for using a CAD system.

1. Increasing the productivity of the designer.

2. Improving the quality of Design.

3. Improving the Communication Process.

4. Creating the large Database for Manufacturing

activities.

5. Multiple/Group performance.

Automation and CAD/CAM

Automation can be defined as the

technology concerned with the application

of complex mechanical, electronic, andcomputer-based systems in the operation

and control ofmanufacturing systems.

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Contd..

Automation can be defined as the technologythat incorporates fields of electrical/ mechanical

electronics with modern computer technology

to operate and control the manufacturing

process.

A typical automation could include CAD/CAM

system, robots, automatic machine tool,

material handling etc.

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Types of Manufacturing Systems

1. Continuous-flow processes. Continuous dedicated production

of large amount of bulk product. Continuous manufacturing is

represented by chemicals, plastics, petroleum, and food

industries.

2. Mass production of discrete products. Dedicated production of

large quantities of one product (with perhaps limited modelvariations). Examples include automobiles, appliances and

engine blocks.

3. Batch production. Production of medium lot sizes of the same

product. The lot may be produced once or repeated periodically.

Examples: books, clothing and certain industrial machinery.

4. Job-shop production. Production of low quantities, often one of

a kind, of specialized products. The products are often

customized and technologically complex. Examples: prototypes,

aircraft, machine tools and other equipment.


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Production

quantity

Continuous

-flow

production Mass

production

Batch

production

Job shop

production

Product variety

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Category Automation achievements

Continuous-flow process Flow process from beginning to end

Sensors technology available to measure

important process variables

Use of sophisticated control and optimization

strategies

Fully computer automated lines

Mass production of discrete products Automated transfer machines

Dial indexing machinesPartially and fully automated assembly lines

Industrial robots for spot welding, part handling,

machine loading, spray painting, etc.

Automated material handling systems

Computer production monitoring

Batch production Numerical control (NC), direct numerical

control (DNC), computer numerical control

(CNC).

Adaptive control machining

Robots for arc welding, parts handling, etc.

CIM systems.

Job shop production Numerical control, computer numerical control


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Design Process

Recognition of need

Definition of problem

Synthesis

Analysis & optimization

Evaluation

Presentation

Design process:

1) Recognition of needs; Involves problems exists for correction

and perception of a new product.

2) Definition of the problem; involves the specification (physical

and functional characteristics, cost, quality, and operation

performance.

3) Synthesis and analysis; are closely related and highly iterative inthe design process. A certain component or subsystem is taken

by the designer, subjected to analysis, improved through this

analysis procedure. The process is repeated until the design has

been optimized with the constraints imposed on the design.

4) Evaluation; is concerned with measuring the design against the

specifications established in the problem definition phase. This

requires the fabrication and test of a prototype model.

5) The presentation of the design; The documentations include

drawings, material specification, assembly lists etc.


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Application of computer in Design

Recognition of need

Definition of problem

Synthesis

Analysis & optimization

Evaluation

Presentation

Design process CAD

Geometric modeling

Engineering analysis

Design review & Evalu

Automated drafting

1- Geometric modeling; is mathematical description of the

geometry of an object.

This helps the designer to construct the graphical image of the object on

the CRT screen of the ICG (interactive computer geometry) system by:

Commands for generation basic elements.

Commands for transformations.

Commands for joining the various elements into the desired objects.

The computer converts the commands into mathematical model, stores, and

displays it as an image on CRT. This model can be called from the data files

for review or analysis.

Methods for representing the object in geometric modeling:

Wire frame.

Surface representation

Solid modeling


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2- Engineering analysisAnalysis of mass properties

Finite-element analysis

3- Design review and evaluation

Check the accuracy of the design (dimensions errors,

interference check, kinematics motion evaluation)

4- Automated drafting

Besides these four functions CAD systems can used forclassified and coding the parts (collecting the similar parts

into groups).

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