Solid Modeling - Engineering Graphics - Lecture Slides, Slides of Computer Graphics and Animation

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Solid Modeling

Objective

• To learn how to generate solid models in CAD

• To understand how to use solid modeling in

the design process

Solid Models

• Definition: A 3-D model of an object that

contains volumetric information

• Mass can be represented

• Interior surfaces are generated automatically

as portions of an object are removed

• Easily constructed using primitive shapes,

extruding, and revolving

Solid Primitives

• Box (Parallelepiped)

• Cylinder

• Cone

• Sphere

• Wedge

EXTRUDE

• Two dimensional closed objects can be extruded to give solid objects
• The direction of the extrusion is typically normal to the 2-D cross sectional sketch
• The height of extrusion can be specified

SWEEP

• The path of the extrusion must be defined (trajectory)
• The extruded cross section must be defined
• The cross section stays normal to the path

BLEND

• Smooth transition can be made between two closed shapes with similar geometry (i.e. equal number of vertices)
• The distance between sections must be defined
• The angle of twist between sections must be specified

Solid Model Operators

• Subtract / Cut
• Intersection
• Union / Protrusion

Solid Model Operators

• Intersection
  • Creates a solid that represents the region that is in common to the selected solids

Solid Model Operators

• Union / Protrusion
  • Creates a single solid from two solids that intersect

Example: Solids from Drawings

• Extrude the view with the most

detailed perimeter

• The depth of the extrusion may

be found from an adjacent view

Example: Solids from Drawings

• Use the perimeter of other views to make additional cuts
• Interpret interior details by making assumptions about geometry in one view and testing them in adjacent views

Using Solid Modeling for Design

• Intersection of wedge

and cylinders is not

clearly defined

• Construction of solid

model forces

resolution regarding

details of construction

Using Solid Modeling for Design

• Intersection of wedge with post produces a gap, a ledge, or a circular groove
• Intersection of wedge with base produces a ledge, an overhang, or requires a rounded end
• These details can be shown in the multiview drawing but are more obvious in the solid model