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CAD and the Design Process

CAD and the Design Process. The Design Process. Problem identification. Specifications. Conceptual design. Concepts. Embodiment design. Layouts. Detail design. Drawings. Manufacture. Product. CAD/CAM/CAE. Models and Representations. Function and behavior mathematical models

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CAD and the Design Process

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  1. CAD and the Design Process

  2. The Design Process Problem identification Specifications Conceptual design Concepts Embodiment design Layouts Detail design Drawings Manufacture Product

  3. CAD/CAM/CAE

  4. Models and Representations • Function and behavior • mathematical models • Structure • flowcharts, diagrams • Form or shape • engineering drawings

  5. Form Models

  6. Traditional Approach • 2D representations used to represent 3D objects • descriptive geometry • orthographic projections • multi-view drawings • Isometric pictorials • Standards and conventions developed so that 3D object could be built from drawings • Drawings created manually, using drafting instruments • Difficult to visualize, error-prone, time-consuming

  7. Multi-view Drawings

  8. Pictorials Isometric Perspective

  9. The Evolution of CAD • 2D drafting • replaced manual drafting • 3D wireframe modelling • 3D surface modelling • 3D solid modelling

  10. 2D CAD • Drawing tools • Line types • Hatching • Dimensioning • Etc.

  11. 2D Drawing Tools

  12. Limitations of 2D CAD • Simply automates manual drafting • Still no 3D representation of the object

  13. 3D Modelling • Geometry must be located relative to a 3D coordinate system • CAD systems use a global coordinate system and local coordinate systems • Various methods available for inputting geometry • work planes • direct keyboard entry • snap to existing entities • etc.

  14. Wireframe Modelling • Geometric entities are lines and curves in 3D • Volume or surfaces of object not defined • Easy to store and display • Hard to interpret - ambiguous

  15. Wireframe Modelling

  16. Wireframe What is this?

  17. Hidden-Line Wireframe

  18. Surface Modelling • Models 2D surfaces in 3D space • All points on surface are defined • useful for machining, visualization, etc. • Surfaces have no thickness, objects have no volume or solid properties • Surfaces may be open

  19. Surface Modelling

  20. Solid Modelling • Complete and unambiguous • Models have volume, and mass properties

  21. Solid Model

  22. Designing in 2D • 3D object is represented by 2D views • The user must make sure views are consistent and valid • The user must generate views from 3D object, and visualize object from views • Spatial visualization has been a key skill for engineers! • These skills have been taught for generations as engineering graphics

  23. Designing in 3D • New CAD systems allow the designer to work directly in 3D • The model can be viewed and manipulated easily and naturally • When the design is complete, 2D drawings and views can be generated automatically

  24. AutoCAD mostly 2D limited 3D modelling limited surface modelling PC-based UNIGRAPHICS (I-DEAS) full 3D solid modelling powerful surface modelling feature-based, parametric solid modeller Workstation-based UNIGRAPHICS (I-DEAS) vs. AutoCAD

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