MEM 201 Fundamentals of Computer Aided Design

• History • Computer Hardware & Software • Basic and Application of CAD Dept of Mechanical Engineering and Mechanics, Drexel University

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The Age of Computers

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Definition of Computer Aided Design • “It is the technology concerned with the use of

computer systems to assist in the creation, modification, analysis and optimization of a design” [Groover and Zimmers, 1984]

• Computer Aided Design and Drafting (CADD)

– refer to the designing and technical drawing of various projects on a computer rather than a traditional drawing board.

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What is the Computer-Aided Design? The use of computer to assist for creation and manipulation - design model represented as a digital data or computer image to assist engineer in the design process

A CAD system usually consists of: · · · ·

A general CAD station

hardware: the computer and associated peripheral equipment; software: the computer program(s) running on the hardware; data or model created and manipulated by the software; human knowledge and activities.

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Hardware • Input Devices

– Keyboard, Mouse – Light pens, Data Tablets, Spaceball • Output Devices

– CRT Monitors, Flat Panel Displays – Plotters, Printers

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The First 2D Software - SKETCHPAD • Developed at MIT by Ivan Sutherland in 1963. • Allowed the user to interact with a computer

graphically. – CRT monitor, Light Pen, Graphical Interface

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The historical evolution of CAD and system architecture Business system required large computer connecting to many terminals •

• •

1st CAD project, MIT in 1959 - 1960, by Ivan Sutherland, developed SKETCHED system, which was an early drawing processing system that used computers, the system included most of the concepts of today's interactive 2D CAD system. General Motors DAC-1 Lockheed Corp. CADAM for business application in 1967

Mini-computer to dedicated graphics terminal • •

Applicon Corp. introduced AGS in 1968 Computer Vision Corp. introduced CADDS in 1969

Personal Computer (PC) AutoDESK (for low-end user) • • • •

AutoDESK Corp. introduced AutoCAD for 2D CAD system in later 1970's AutoCAD R 12, and R13 C4 in 1996 AutoDESK Collection, AutoCAD, AutoVision, Desiger, 3D studio Mechanical Desktop – parameter based system

Integrated and knowledge-based CAD/CAE/CAM System (for high-end user) •

I-DEAS/Pro-E/UG/CATIA

Mid-range solid modeler •

SolidWorks, Solid Edge 10/2/2008

Role Role of of CAD CAD in in Product Product Development Development Process Process Design Model The descriptions of the design processes are often called models of the design process. The design model describes design as a series of stages and progressing from requirements through conceptual design and preliminary design to detail design and to manufacturing to record and manipulate ideas, to provide a basis for the evaluation of the design. to communication of the design At the various stages of the design the design models are developed through a process of analysis and evaluation leading to modifications and refinements. Types of design model can be defined by the following modeled properties Types of design model: Design model for function Design model for structure Design model for form of the component parts Design model for materials Design model for surface condition Design model for dimensions etc.

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Role Role of of CAD CAD in in Product Product Development Development Process Process

CAD in assisting geometric modeling Graphics or geometric modeling using CAD is used to visualize, analyze, document, and produce a product or process. In fact, geometric modeling itself could be considered both a process and a product. As a process, geometric modeling produces final design solutions, as well as inputs to the production process, in the form of computer databases. As a product, geometric modeling is a result of the engineering design process

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Representation Representation of of Design Design Model Model By drawing

By diagram

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Representation Representation of of Design Design Model Model By By digital digital data data -- CAD CAD solid solid modeling modeling

CAD for complex design representation Full-Scale Aircraft Structural Test Fixture (4206 parts in FASTER system) 10/2/2008

Major Major functions functions of of aa solid solid modeling modeling based based CAD CAD system system in in design design process process model definition

- geometrical or design modeling

model manipulation

- to edit and modify in the design model

visualization

- image of design model and design results

application

- generate interfacing information evaluation/analysis/manufacture

database management

- files and data management

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CAD CAD used used as as aa design design assistant assistant tool tool Basic level - to assist in drafting

- Produce 2D engineering drawing and diagram - CAD is only used for Computer-Aided Drafting Advantages:

Productivity - short period of design and lower cost of design work Accuracy - improvements of product quality Consistency - national standards, in-house standards

Advanced level - to assist in design by 3D modeling - wireframe model, began to link with CAM and CAE - 3D surface model, shading for image - 3D solid model, completed information and real-photo image - 3D CAD modeling for visualization - 3D CAD modeling for analysis - 3D CAD modeling for prototyping - 3D CAD modeling for manufacturing - 3D CAD modeling for simulation - 3D CAD modeling for animation

- CAD/Design Vision - CAD/CAE and FEA - CAD/RP&M - CAD/CAM/CNC, CAD/CAPP - CAD/Real Physical Model - CAD/Real Physical Model

3D modeling has transformed CAD from Computer-Aided Drafting into Computer-Aided Design 10/2/2008

Example Example of of CAD CAD systems systems -- AutoCAD AutoCAD

Icons (Tool Palette) - Composite set of most frequently used commands Pull-Down Menu(Menu Bar) - Listed on the menu bar, contain all the commands. Screen Menu - Containing almost all the commands. Graphics Window - the place used to build up model. Status Line - Give you information about the current status of your model Command Window - A place you and AutoCAD can talk to each other

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Features Features of of AutoCAD AutoCAD System System Command Entry Styles Keyboard entry Pull-down menus Screen Menus Table Menu and Icons Geometric Entities and Entry Coordinates Three parts of AutoCAD Commands Draw Construct Modify

- entities (line, arc, circle, pline etc.) - manipulate of entities (copy, array, chamfer, fillet, mirror, etc.) - edit of entities (erase, trim, move, etc.)

A geometric-based CAD modeler

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