AML710 CAD LECTURE 1. Introduction to CAD. Motivation Principles of CAD / CAM. AML710 Computer Aided Design

Transcription

1 AML710 CAD LECTURE 1 Introduction to CAD Motivation Principles of CAD / CAM AML710 Computer Aided Design L-T-P : 4 Credits Prerequisites and background Course Coordinator Course Webpage Course Contents Books and Notes Typical topics Course Evaluation Attendance Policy Laboratory Practicals Software tools and Techniques 1

2 Aerospace Motivation for the Study of CAD Application of CAD/CAM 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 2

3 Graphics Pipeline Real world Object Modeling Transformations Rendering/ Shading Viewing Transformations Geometrical Model Visual Realism Orthographic/ Perspective Clipping Display Rasterization PROJECTION Projections Graphics Pipeline 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) x 2 + y 2 = 1 x = cos(t) y = sin(t) 3

4 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 4

5 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 Analyse / Evaluate Modify / Refine Model 1 Model 2 Modify / Refine Analyse / Evaluate CAPP Generate information for planning and manufacture Model n NC / CNC PRODUCT 5

6 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 6

7 Definition of CAD Computer aided Design is a subprocess of Design process Computer Graphics Network CAD Manufacturing CAM CAD Design Engineering Geometric Modeling 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 7

8 Steps in CAM activity Geometric Model Interfacing CAPP NC Programs Inspection 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 8