Introduction to CAD Motivation Principles of CAD / CAM AML710 - - PDF document

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Introduction to CAD

Motivation Principles of CAD / CAM

AML710 CAD LECTURE 1

AML710 – Computer Aided Design

L-T-P – 3-0-2 : 4 Credits Prerequisites and background Course Coordinator Course Webpage http://web.iitd.ac.in/~hegde/cad Course Contents Books and Notes – Typical topics Course Evaluation Attendance Policy Laboratory Practicals Software tools and Techniques

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Motivation for the Study of CAD

Application of CAD/CAM

• Aerospace

Motivation for the Study of CAD

Application of CAD/CAM

• Aerospace
• Automotive
• Chemical & Process
• Communications
• Computers & IT
• Electrical & Electronics

Examples

• Medical & Pharma
• Military & Defence
• Rail & Marine
• Structural & Civil
• Apparel and Textile

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Graphics Pipeline

PROJECTION Rasterization Display Clipping Orthographic/ Perspective Visual Realism Geometrical Model Viewing Transformations Rendering/ Shading Modeling Transformations

Graphics Pipeline

Real world Object Projections

Theme of the Course

• Starting from geometric concepts we

proceed to compute something in several steps as:

Geometry -> Algebra -> Algorithm -> Program Ex: Circle -> implicit/parametric equation->Smith’s algorithm->computer implementation in C/C++/MATLAB (OpenGL) x2 + y2 = 1 x = cos(t) y = sin(t)

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The Geometric Complexity

• As algorithms are an integral part of the

geometry -> Program representations, we need to think of the complexity involved. They are:

• 1. Dimensional Complexity- 1D/2D/3D
• 2. Analytic Complexity- Polynomials of degree 1,2,3,….
• 3. Combinatorial Complexity- For example,

searching a sorted array of n elements uses O(log2n) comparisons.

• 4. Continuum to Discrete
• 5. Precision and Errors

What is Design?

• Design, usually considered in the context of applied arts,

engineering, architecture, and other creative endeavors, is used both as a noun and a verb.

• As a verb, "to design" refers to the process of originating and

developing a plan for a product, structure, system, or component.

• As a noun, "a design" is used for both the final (solution) plan

(e.g. proposal, drawing, model, description) or the result of implementing that plan (e.g. object produced, result of the process). More recently, processes (in general) have also been treated as products of design, giving new meaning to the term "process design”

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Some Popular Design Approaches

• User-centered design, which focuses on the needs,

wants, and limitations of the end user of the designed artifact.

• Use-centered design, which focuses on the goals

and tasks associated with the use of the artifact, rather than focusing on the end user.

• KISS principle, (Keep it Simple, Stupid), which

strives to eliminate unnecessary complications

• There is more than one way to do it (TMTOWTDI), a

philosophy to allow multiple methods of doing the same thing

• Murphy's Law (things will go wrong in any given

situation, if you give them a chance)

What is Design?

Design is an Iterative Process (Ohsuga 1989)

Requirement Build Model Model 1 Modify / Refine Analyse / Evaluate Model 2 Modify / Refine Analyse / Evaluate Model n Generate information for planning and manufacture CAPP NC / CNC PRODUCT

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The Design Process – An Engineering Activity

• 1. Need
• 2. Concept
• 3. Modeling and Simulation
• 4. Analysis – FEM (Geometrical Data)
• 5. Optimize – Shape / Structure / Topology
• 6. Evaluate – testing / Inspection / Comparison
• 7. Communicate – prepare drawings and details

Taking assistance of Computers in Design

• 1. Manual Design
• 2. Geometric Models and Graphics
• 3. Move / Animate / Visualise
• 4. Use Analysis tools and software
• 5. Optimize – Maximize / minimize the objective

functions: Structure, Shape, Topology

• 6. Evaluate – test and check the model
• 7. Communicate – Drafting and detailing

Generate information Manage/Control Communicate

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Definition of CAD

Computer aided Design is a subprocess of Design process

Computer Graphics Design Engineering Geometric Modeling CAD Network Manufacturing CAD CAM

Computer Aided Design

• 1. CAD Technology = Design Techniques +

Computers (HW+SW)

• 2. The CAD Process is the subset of the Design

process

• 3. The CAM Process is a subset of

Manufacturing Process

• 4. Integration of CAD and CAM leads to

automation

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Steps in CAM activity

Geometric Model Interfacing CAPP Inspection NC Programs Assembly Packaging

Graphics Standards

Many Graphics Standards have been in use. The real issue with choosing the standards is portability and device independence.

• BGI
• GKS
• PHIGS
• OpenGL

A ray tracing Example