CAD_modeling Dr Rachayya.ppt
- 1. 3D-Geometric Modeling Geometric modelling refers to a set of techniques concerned mainly with developing efficient representations of geometric aspects of a design. Therefore, geometric modelling is a fundamental part of all CAD tools. Dr R R Arakerimath GHRCEM
- 2. 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. –2D/3D drafting –3D modeling for visualization –Modeling curves,surfaces,solids,mechanism,assemblies,etc. Dr R R Arakerimath GHRCEM
- 3. • ANALYSIS – Stress (deflection analysis,I.e. numerical methods,FEM – Simulation of actual use – Optimizations – Applications – CAD/CAM integration – Process planning Dr R R Arakerimath GHRCEM
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- 5. CAD Software CAD software can be divided based upon the technology used: 1. 2-D drawing. Its applications include, · mechanical part drawing · printed-circuit board design and layout · facilities layout · cartography 2. Basic 3-D drawing (such as wire-frame modelling) 3. Sculptured surfaces (such as surface modelling) 4. 3-D solid modelling 5. Engineering analysis Dr R R Arakerimath GHRCEM
- 6. DATA BASES FOR CAD Volume Plane surfaces Warped surfaces curves Net of curves patch point Is bounded by Is boundary of Consist of Belongs to Belongs to Consist of surface unit Has boundary curve Is chain of Makes up precedes succeeds Has starting point delimits surface Curve segment Dr R R Arakerimath GHRCEM
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- 8. CAD DOES? • Full-fledged platform for engineering solution; modeling, FEA, assembly, drawing in one system • Integration with engineering knowledge; guide user throughout the modeling process • design-wonder capable assisting designer; understanding the drawing Dr R R Arakerimath GHRCEM
- 9. CAD? • Modeling, assembly and drawing generation within a single system • Current CAD software comes with FEA software eg. Solidwork with COSMOSM • Well established neutral file capabilities • Networking facilities Dr R R Arakerimath GHRCEM
- 10. Product design Dr R R Arakerimath GHRCEM
- 11. Elements of Product design Dr R R Arakerimath GHRCEM
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- 16. • Surface modeling Dr R R Arakerimath GHRCEM
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- 34. Boundary Representation Objects are represented by their bounded faces. Dr R R Arakerimath GHRCEM
- 35. B-Rep Data Structure Dr R R Arakerimath GHRCEM
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- 39. a system that constructs relations among the geometry of different elements. When one element is changed, the geometry of the rest of the elements are changed as well. Parametric design changed the way products are designed and prototyped: design > prototype > manufacture … all on computer Dr R R Arakerimath GHRCEM
- 40. Dr R R Arakerimath GHRCEM Needs & Desires Informal Constraints Analysi s Formal Requiremen ts Formal Constraints synthesis DESIG N
- 41. Solid Modeling Functions Dr R R Arakerimath GHRCEM
- 42. Surface Modeling • Stores equations of surfaces • Most 3D graphics libraries use surface modeling • Good for visualizing complex surfaces and automated NC path generation of complex surfaces • Material volume information is ambiguous or hard to determine (therefore can’t calculate volume) Dr R R Arakerimath GHRCEM
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- 47. Advantages of CAD/CAM • Product quality • Shorter design time • Production cost reductions • Database availability • New range of capabilities • Reduces need for “similar” parts Dr R R Arakerimath GHRCEM
- 48. • SURFACE MODELING Dr R R Arakerimath GHRCEM
- 49. SURFACE ENTITIES Similar to wireframe entities, existing CAD/CAM systems provide designers with both analytic and synthetic surface entities. Analytic entities include : •Plane surface, •Ruled surface, •Surface of revolution, and •Tabulated cylinder. Synthetic entities include •The bicubic Hermite spline surface, •B-spline surface, •Rectangular and triangular Bezier patches, •Rectangular and triangular Coons patches, and •Gordon surface. Dr R R Arakerimath GHRCEM
- 50. Plane surface. This is the simplest surface. It requires three noncoincident points to define an infinite plane. Dr R R Arakerimath GHRCEM
- 51. Ruled (lofted) surface. This is a linear surface. It interpolates linearly between two boundary curves that define the surface (rails). Rails can be any wireframe entity. This entity is ideal to represent surfaces that do not have any twists or kinks. Dr R R Arakerimath GHRCEM
- 52. Surface of revolution. This is an axisymmetric surface that can model axisymmetric objects. It is generated by rotating a planar wireframe entity in space about the axis of symmetry a certain angle. Dr R R Arakerimath GHRCEM
- 53. Tabulated cylinder. This is a surface generated by translating a planar curve a certain distance along a specified direction (axis of the cylinder). Dr R R Arakerimath GHRCEM
- 54. Bezier surface. This is a surface that approximates given input data. It is different from the previous surfaces in that it is a synthetic surface. Similarly to the Bezier curve, it does not pass through all given data points. It is a general surface that permits, twists, and kinks . The Bezier surface allows only global control of the surface. Dr R R Arakerimath GHRCEM
- 55. B-spline surface. This is a surface that can approximate or interpolate given input data (Fig. 6- 9). It is a synthetic surface. It is a general surface like the Bezier surface but with the advantage of permitting local control of the surface. Dr R R Arakerimath GHRCEM