Course Description. Spring

Transcription

1 Spring Course Description AE4375: advanced treatment for undergrads; focus on learning and aplying CAD to engineering; CAD modeling projects. AE6380: graduate course on CAD focusing on how tools can be integrated into engineering design processes; CAD modeling and integration projects. Course Outline: see class web page Class Schedule: see class web page TTh 8-9:30: lectures on geometric modeling; surface and solid models; CAD processes; integration CATIA Workbook: hands-on training in AE Computer Lab CAD projects: illustrate CAD principles; reinforce training Geometric modeling with Matlab: illustrate principles Capstone project: ties it all together; learn how to learn

2 Spring Grading: Course Details Projects (CAD, Matlab, homework) 60% Midterm exam 15% Final exam 25% Course web page: Academic personnel Course instructor: Prof. J. Craig (x4-3042, james.craig@ae.gatech.edu) Lab instructor: Patrick Roberts (x4-6696, gt0398b@prism.gatech.edu)

3 Spring Product Development Process Example: aircraft wing Product function generate lift support static/dyn loads be of low cost etc. Process model CFD (aerodynamics) FEM (structural analysis) Mfg. cost model etc. Product Function synthesis Product Model Product model geometric model mfg models tolerances assembly feature-based geo. Factory Model Design Process Models Design Process Design Process Models Mfg Process Production

4 Spring Kinds of Design Models Product development models Generic product knowledge (Design Process Models) Product models (geometric & non-geometric) Generic mfg process models (with physics-based and economic models) Factory models (specific instances) Non-geometric models wiring schematics hydraulic piping diagrams flowcharts graph-based models

5 Different Design Models of Same Component Spring

6 Spring Some Non-geometric Models Hydraulic Components Control System Flowchart

7 Some Non-geometric Models Spring

8 Spring Other Issues Chronological Issues: Conceptual Conceptual Preliminary Detail Nongeometric Simple System definition Subsystem partitioning MDO Geometric models Manufacturing Hierarchical Issues: Subsystem Conceptual1 Component 1 System Subsystem 2 Component 2

9 CAD Fundamentals Geometric modeling systems User interface Geometry representation Topology representation Manipulation procedures Database method Data exchange Why 3D models aren t more widely used in design: Conceptual design is concerned with functions performed by geometry; not by the geometry itself Preliminary design is concerned with subsystem interface geo. Detailed design IS concerned with microscopic geometry! Geo. models do not include design intent Geo. models do not identify mfg. or functional or geo. features Tolerances are not easily handled Spring

10 Spring CAD Fundamentals - cont d Why 2D drawings are still widely used: They include lots of nongeometric information in notes Can be sketched easily on paper Familiar system 2D dwgs are difficult: Not always unambiguous Need human interpretation Can t readily be interpreted by machines

11 Spring Basic Descriptive Geometry How do you draw a 3D object in 2D space (on paper)? Projections (axonometric, oblique, persepctive) Multiview projections Conventions (1st angle vs 3rd angle) Axonometric Perspective Multi-view Orthographic

12 A Simple Example - Desk One Point Isometric Cavalier Two Point Dimetric Cabinet Oblique Projections Three Point Perspective Projections Trimetric Axonometric Projections Spring

13 Spring A Simple Example - Desk (cont d) Top Rear Left Side Front Right Side Bottom Conventional Multi-view Orthographic Projection

14 Spring Wireframes easiest of all to create nothing hidden visually ambiguous topological problems? Basic 3D Models

15 Spring Wireframe Problems Can you figure out what this is? (It s really a valid wireframe model )

16 Spring Wireframe Problems - cont d You were looking at this...

17 Spring Basic 3D Models Surface models accurate surface def n enclose a volume topologically difficult to handle Ruled Surface Tabulated Cylinder (swept surface) Surface of Revolution Swept Surface NOTE: control points define shape of surface

18 Spring More complex surfaces Basic 3D Models

19 Spring Volumes combine surfaces together topology is a problem boundary representation models (B-rep) Basic 3D Models

20 Spring Basic 3D Models Boundary models (b-rep) aka: graph-based models graph nodes & edges Rules: faces bounded by single loop or ring of edges edge joins exactly 2 faces and is terminated by vertices at least 3 edges meet at each vertex Euler s Rule applies: V-E+F=2 extended V-E+F-H+2P=2B

21 Spring Solid models Notion of inside vs outside Analytical models (extend surface to 3-parameters) Spatial decomposition or cell enumeration Constructive solid geometry (CSG) B-rep Basic 3D Models Quadtree (2D) Octree (3D)

22 Spring Basic 3D Models CSG Primitives and Boolean Operations Graph-based CSG representation

23 Spring Basic 3D Models This is a simple CSG object... Solid models can have problems... All points are surrounded by valid regions of the surface of the object. Some of thse points are on degenerate (2D or 1D) extensions of the object. This is a much more comples CSG object! (can you see why this is so?) NOTE: By restricting the types of boolean operations that are allowed, we can avoid most of these degeneracies.

24 Spring Basic 3D Models A feature-based approach This is much easier to relate to common manufacturing operations and avoids creating parts that are impossible to manufacture using conventional tooling.

25 Spring Basic 3D Models Solid models are useful to show other aspects of a product - assembly.