(cad) computer aided design in geometric · pdf filemeng 351, lecture 3 dr. hesham hegazi...

MENG 351, Lecture 3 Dr. Hesham Hegazi

Geometric Modelingin

Computer Aided Design (CAD)

MENG 351, Lecture 3 Dr. Hesham Hegazi

Geometric Modeling

• Definition: Geometric modeling is the technique we use to describe the shape of an object.

MENG 351, Lecture 3 Dr. Hesham Hegazi

CAD Computer- Aided Drafting and Design

• 2D - Two Dimensional• 3D - Three Dimensional

– Wire Frame Models– Surface Models– Solid Models– Parametric Models

MENG 351, Lecture 3 Dr. Hesham Hegazi

3-D Wire Frame Modeling• Disadvantages:

– Not able to fully define real objects

(No volume and mass)– Displays only edges of

a model

MENG 351, Lecture 3 Dr. Hesham Hegazi

Surface Modeling• Surface models

provide a more complete description of the object, but is still not as good as the solid model.

MENG 351, Lecture 3 Dr. Hesham Hegazi

Surface Modeling

MENG 351, Lecture 3 Dr. Hesham Hegazi

Solid ModelingSolid

B-Rep CSG

Boundary Representation:•Extrusion•Revolving•Sweeping•Blending of 2-D profiles

Constructive Solid Geometry:•Construction of solid by combining primitives using Boolean operators of union, intersection, and difference•Uses solid primitives (cylinder, cone, etc.) as building blocks

MENG 351, Lecture 3 Dr. Hesham Hegazi

Solid Modeling

MENG 351, Lecture 3 Dr. Hesham Hegazi

Solid Modeling

MENG 351, Lecture 3 Dr. Hesham Hegazi

Parametric Modeling

Parametric Modeling

Constraint-Based ModelingDimension-Driven Modeling

Uses parameters to specify dimensions of entities

Uses geometric constraints such as parallelism, concentricity, etc.

MENG 351, Lecture 3 Dr. Hesham Hegazi

Design

Design

Personal Expression(Artisitic)

Product/ProcessDevelopment(Technical)

Aesthetic(Industrial Design)

Functional(Engineering Design)

Engineering Design Cycle

Product Process

MENG 351, Lecture 3 Dr. Hesham Hegazi

Basic Geometric Entities

• Point (X,Y,Z)• Line (X,Y,Z) Start (X,Y,Z) End• Circle (X,Y,Z) Center & Diameter• Arc (X,Y,Z) Center , Radius, Start & End

Angle or Point

MENG 351, Lecture 3 Dr. Hesham Hegazi

More advanced Approaches• Feature-based modeling

– Uses features such as holes, ribs, pockets, slots– More advanced than CSG

• Assembly modeling– Modeling of assembled parts– Utilizes much of the same technology as solid

modeling• Product modeling

– Includes not only the geometry of an object, but also any information that is needed to design, develop, and produce the product. (e.g. stress-analysis)

MENG 351, Lecture 3 Dr. Hesham Hegazi

Basic CAD Functions

• Viewing Commands (zoom, pan, etc..)• File commands (new, open, save, etc..)• Drawing Commands (line, circle,

rectangle, arc, spline, 3D shapes, etc..)• Modifying Commands (Trim, erase,

extend, copy, move, Extending, etc..)

MENG 351, Lecture 3 Dr. Hesham Hegazi

Neutral File Formats

• DWG – AutoCAD Drawing file• DXF - Drawing Exchange Format• IGES - Initial Graphics Exchange

Specification• CADL- CADKEY Advanced Design

Language• STL - Sterolithography.

MENG 351, Lecture 3 Dr. Hesham Hegazi

Future Directions of 3-D Modeling

• Geometric modeling will be “supplanted by product modeling which not only includes the geometry of the object, but any information or data that is needed to design, develop, produce and support the product through its entire life cycle.”

MENG 351, Lecture 3 Dr. Hesham Hegazi

Commercial CAD Software

• Pro Engineer (http://www.ptc.com/)• Unigraphics (http://www.ugsolutions.com/)• Autocad (http://www.autodesk.com/)• CADKEY (http://www.cadkey.com/)• Microstation• CATIA

(http://www-.ibm.com/solutions/engineering/eshome.nsf/public/catmain)

• VisualCADD (http://www.imsisoft.com/products/visualcadd/index.cfm)• TurboCAD (http://www.turbocad.com/)• SolidWorks (http://w ww.solidworks.com/)