Solid Modeling Constructive Solid Geometry CGS Primitives combined
Solid Modeling Constructive Solid Geometry (CGS) ¨ Primitives combined by Boolean operations to form composite solids. General Steps: 1. Construct simple 3 D primitive solids, or create 2 D shapes and convert them to 3 D solids by extruding or revolving. 2. Create primitives in location relative to the associated primitives, or move the primitives into the desired location relative to the associated primities. 3. Use Boolean operations (such as Union, Subtract, or Intersect) to combine the primitives to form a composite solid. 4. Make necessary design changes to features of a composite solid using the variety of editing tools in Solidedit.
Primitives: n 1. 2. 3. 4. 5. 6. 7. 8. basic building blocks that make up more complex solid models. BOX CONE CYLINDER SPHERE TORUS WEDGE EXTRUDE REVOLVE
Extrude • n n creates a solid by extruding (adding a Z dimension to) a closed 2 d object (Pline, Circle, Region) EXTRUDE is a sweeping operation that allows the addition of a Z (height) dimenwion to an otherwise 2 D shape. This command extrudes an existing closed 2 D shape such as a Circle, Polygon, Ellipse, Pline, or Spline. Only closed 2 D shapes can be extruded. The closed 2 D shape cannot be self-intersecting (crossing over itself). (Note: Individual lines and curves can be converted into a Pline using Pedit. ) Two methods determine the direction of extruding: perpendicular to the shape and along a Path. With the default method, the selected 2 D shape is extruded perpendicular to the plane of the shape regardless of the current UCS orientation. Using the Path method, you can extrude the existing closed 2 D shape along any existing path determined by a Line, Arc, Spline, or Pline.
Revolve n n REVOLVE creates a solid by revolving a 2 D shape about a selected axis. The 2 D shape to revolve can be a Pline, Polygon, Circle, Ellipse, or a Spline. Only one object at a time can be revolved.
Boolean Operations n used to combine primitives 1. UNION – joins selected solids. SUBTRACT – subtracts one set of solids from another INTERSECT – creates a solid of intersection (common volume ) from selected solids. 2. 3.
Solids Editing FACE Options: 1. 2. 3. 4. 5. 6. 7. 8. Extrude – extrude any face of a 3 D object Move – move a single face of a 3 D solid, or move an entire primitive within a 3 D solid. Offset – makes parallel copies of faces; (useful in making a hole larger or smaller) Delete – delete faces from composite solids Rotate Taper – change the angle of planar or curved faces Copy – copy faces. The resulting objects are regions. Color – change color of selected faces
Solids Editing EDGE Options: 1. Copy 2. Color BODY Options: 1. Imprint – used to attach a 2 D object on an existing face of a solid (Body) 2. Clean – deletes any 2 D geometry on the solid. (removes imprints) 3. Separate – separate two “unioned” solids that do not occupy the same physical space. 4. Shell – converts a solid into a thin walled shell
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