INTRODUCTION TO CAD What is CAD Integration of

INTRODUCTION TO CAD What is CAD? –Integration of CS techniques in engineering design –Use of computers(hardware & software)for designing products –Numerical method, optimizations etc. – 2 D/3 D drafting – 3 D modeling for visualization –Modeling curves, surfaces, solids, mechanism, assemblies, etc.

• ANALYSIS – Stress (deflection analysis, I. e. numerical methods, FEM – Simulation of actual use – Optimizations – Applications – CAD/CAM integration – Process planning

3 ASPECTS OF CAD • • Modeling Display/visualization Applications MODELING – Definition of objects – Relation between objects – Properties – Orientations in suitable co-ordinate system – Modification of existing definition (editing)

• DISPLAY VISULIAZITION AIDS – Display of model objects – Mapping objects onto screen coordinates – Surface display, shading – Projections – Hidden line removal when multiple surfaces are displayed

REQUIREMENTS OF MODELING • Solids are modeled by storing information of constituent surfaces • This help in – Displaying surfaces(3 D) – Computing solid properties – Modeling by storing info. on bounding curves or by storing their geometric definitions

DATA BASES FOR CAD Volume delimits surface Is bounded by Plane surfaces Warped surfaces Is boundary of Has boundary curve Makes up Consist of surface unit Is chain of precedes succeeds Has end point Is the end of Is the start of Curve segment point Belongs to curves Has starting point Consist of Net of curves patch

LIST OF REFERENCE BOOKS • Principal of interactive CG by Newman & sprawl* • Geometric modeling by Mortenson* • Fundamental of ICG by Foley & van dam • Procedural elements of CG by Rogers* • Mathematical elements of CG by Rogers and Adams • Principal of CG by Hearn & baker • Computer graphics, A programming approach by Steven & Harrington

• An introduction to FE computations by Hinton & Owen • An introduction to FE in engineering* by Chandrupatla & Belegundu • Zincowicz (3 C) • Zincowicz & taylor (4 C)

Evaluations • • Minors (I and II) – 30% Major --- 40% Labs ---- 20 % Quizes --- 10%

DISPLAY DEVICES • Storage tube devices • Permanent phosphorescence • For erasing entire screen is flooded with a particular voltage • Can draw a line from any point to any point • CALLIGRAPHIC REFRESH GRAPHICS DISPLAY • Picture is refreshed 40 -50 times a second

• Display buffer & controller • Stores INFO about each entity to be displayed Display buffer controller Vector/character generator Repeats whole process 40 -50 times a second CRT

RASTER REFRESH GRAPHICS DISPLAY • SCREEN IS A MATRIX OF POINTS • Each point (pixel) can be bright/dark • Lines & curves as series of bright pixels

• Frame buffer stores a bit for each pixel(I if on, o if off)bit plane • Additional bit planes for achieving different gray levels/colors. • The programmer modifies the frame buffer • And the display controller refreshes the screen on the basis of the frame buffer

INPUT OUTPUT DEVICES • Input devices – Analog type: mouse (ball type) – X-y variable Resistance

– Track ball – Joy stick • Digital type • Light pen – Light sensitive diode to point the screen – Positioned is sensed on basis of when pen senses light

TABLET AND PEN Grid of wire Pen emits radio frequency and intensity received by each wire tells the position

HARDCOPY AND OUTPUT DEVICES • Flat bed plotters – Pen – X-drive motor & Y-drive motor – Pen raise & lower mechanism – Controller – Drum plotter • Pen • Raise and lower mechanism

• X-drive(for pen) & Y drive(for drum) motors • Controller • Printers – DMP – Laser – Inkjet