MECH 6303: Computer Aided Design: CAD

Lecture 2

- What is CAD/ CAM? - CAD software classification - CAD software selection criteria - General design philosophies - Coordinate systems - Basic CAD tools

Dr. Yonas Tadesse Mechanical Engineering Department The University of Texas at Dallas 1

CAD/CAM • Computer Aided Design – Using computer technology for the design of real or virtual objects – Represent a means • Computer Aided Manufacturing – Using computer based software to manufacture/prototype product components – Represent a goal * Goal = final marketable product of value - Features - Durability - Cost

- Functionality Lecture notes : From Dr. Danni Fadda 2 CAD/CAM

Geometric CAD modeling

CAM CAD Computer Manufacturing Design Automation graphics CAD software

Zeid “Mastering CAD/CAM” classify CAD Software as follows:

Low Range Mid Range High End

• AutoCAD • SolidWorks, • Unigraphics, • Inventor • ProE, • , • CADKEY • MasterCAM • I-DEAS, • CATIA

Lecture notes : From Dr. Danni Fadda 4 Low Range: AutoCAD Software • Primitive 3D • Parts can interfere • Parts are not separately identified as entities • Difficult to make changes • Excellent for 2D design (e.g., HVAC, Architectural, Plumbing, Electrical)

Lecture notes : From Dr. Danni Fadda 5 Mid Range: ProE • Excellent 3D • Parts are drawn and detailed as separate parts • Assembles include all the parts with an available part tree • Changes can be made by simply changing dimensions • No Boolean operations – “A part is a part”

Lecture notes : From Dr. Danni Fadda 6 SolidWorks • A CAD modeling software that run in . • Developed by Dassault Systèmes SolidWorks Corp.(DSS, France) • User usage : more than 1.3 million engineers and designers(2011data), 1.78 million (2012) . • Companies worldwide usage : more than 130,000. • First released in 1995, latest 2012. • DSS Revenue: €1.564 billion (2010) • DSS employee: 9020 ( 2010) Source: - Wikipedia(accessed 10/10/2012) - http://www.Solidworks.com Pro/Engineer and Creo • A CAD modeling software that run in Microsoft Windows. • Developed by Parametric Technology Corporation (PTC). • It is feature based, parametric . • Later included several functionality: Assembly drawing, drafting, FEM, CNC • Creo Elements/Pro (2010), Latest release CREO 3.0 (2014). • First release, Pro/ENGINEER ,1987 • PTC revenue : $1,010 million (2010) Source: -Some data from • PTC employee: 5500 (2010) Wikipedia (accessed 10/10/2012)

High End: CATIA

• Legacy CAD/CAM systems • All of the best of AutoCAD and ProE – Sketch plane – Boolean operations • Product data management (PDM) modules • Used for manufacturing of airplanes/cars/ships/other complex products

Lecture notes : From Dr. Danni Fadda 9 Software selection criteria

• Ease of use • Quality of documentation • Software maintenance • Support and service • Geometric modeling capabilities • Design and manufacturing applications • Programming languages available for customizing

Lecture notes : From Dr. Danni Fadda 10 General design philosophies

• Design for assembly( DFA) • Design for manufacturing (DFM) • Design for Reliability • Fail Safe Design • Damage tolerant Design • Concurrent Engineering

General design philosophies cont.. • Design for assembly(DFA) - Based on ease of assembly and reducing the number of parts - Question to ask? 1. Is there relative movement between the part and other component? 2. Is there any need to assemble and disassemble the part? 3. Must the part be made of different material with the other one?

• Design for Manufacturing(DFM) - Based on ease of fabrication - example : avoiding unnecessary features in the part - The volume of the production process or mass manufacturing . For example casting is preferred than machine, to avoid waste of materials

General design philosophies cont.. • Design for Reliability - based on the probability of the device , working without failure, for certain period of time under specified conditions • Fail Safe Design - Even if one components fails, the whole system needs to be safe. - Aircraft systems : redundant engine • Damage Tolerant Design - assume that initial defect occurs in the materials - based on the ability to maintain its strength in a damaged condition.( eg. Crack) • Concurrent Engineering - All phase of the design from concept to disposal are done at the same time ( concurrently) - Designer, draftsman, manufacturing personnel all work together in parallel.

Coordinate systems in CAD

• Three types of coordinate systems used in CAD - to input - to store - to display

• Three types (1) (2) (3)

Ref: Cad/Cam: Concepts And Applications By Alavala Coordinate systems in CAD

• Three types of coordinate systems used in CAD - to input - to store model geometry and graphics - to display

• Three types (1) World Coordinate System( WCS) (2) User Coordinate System (UCS) (3) Screen Coordinate System (SCS)

Ref: Cad/Cam: Concepts And Applications By Alavala World Coordinate System (WCS): • Often called Model Coordinate System • A reference space in which model geometrical data is stored • The only coordinate system a software system recognize when storing or retrieving geometrical data of a model. • Is the default coordinate system in CAD software User Coordinate System (UCS) • Defined by the user particularly for complex object modeling • The coordinate system can be set up at any position and orientation • Many UCS can be constructed but only one can be active at one time Screen Coordinate System (SCS) • Is a two dimensional Cartesian coordinate system • Device dependant coordinate system. • For raster graphics display, the pixel grid is the screen coordinate system. • When 2D graphics is displayed , the WCS is

transformed by the software. (1024, 1024)

origin

(0,0) Basic CAD tools

A. Sketch B. Features

Basic CAD tools

A. Sketch B. Features - Points - Extrude - Line - Revolve - Spline - Sweep - Plane - Loft - Circle - Extrude Cut -arcs - - Ellipse - Rib - offset -Mirror - Draft - Patterns - Dome

Summary • Introduction CAD/CAM • Design Philosophies • The course coves all the fundamentals and advanced features of CAD system • CAD software classification • CAD software selection criteria

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