Solid Modeling

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Solid Modeling

• Engineering Graphics
• Stephen W. Crown Ph.D.

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Objective

• To learn how to generate solid models in CAD
• To understand how to use solid modeling in the
  design process

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Overview

• Primitives
• Extrude
• Sweep
• Revolve
• Blend
• Solid Model Operators
• Viewing Solid Models

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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

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Solid Primitives

• Box (Parallelepiped)
• Cylinder
• Cone
• Sphere
• Wedge

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Example Using Primitives

• Box
• Wedge
• Union / Protrusion
• 6 boxes
• 2 wedges
• Subtract / Cut
• 1 box - minus 2 wedges
• 1 box - minus 2 boxes

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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

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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

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REVOLVE

• Two dimensional closed objects can be revolved to
  give solid objects
• The axis of rotation must be defined
• The angle of revolution must be specified

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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

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Solid Model Operators

• Subtract / Cut
• Intersection
• Union / Protrusion

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Solid Model Operators

• Subtract / Cut
• subtracts one solid from another
• One solid is subtracted from the other.

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Solid Model Operators

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

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Solid Model Operators

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

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Example Solid Model Operators
What procedure would you follow to create the
two mating parts?

• Create the bounding box for the upper part
• Create the two cylinders
• Subtract the cylinders from the box
• Create the bounding box for the lower part
• Subtract the finished upper part

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Example Solids from Drawings

• Extrude the view with the most detailed perimeter
• The depth of the extrusion may be found from an
  adjacent view

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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

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Example Solids from Drawings

• Verify that the completed part satisfies every
  view
• Generate a multiview drawing from the solid part
  and compare to the original sketch or drawing

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Using Solid Modeling for Design

• Intersection of wedge and cylinders is not
  clearly defined
• Construction of solid model forces resolution
  regarding details of construction

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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

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Viewing Solid Models

• Rendering Styles
• Wireframe with hidden lines
• Hidden lines removed
• Shaded

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Viewing Solid Models

• LIGHTING
• Distance, Point, Spotlight
• Ambient light
• Intensity
• Modify (specify location of light)
• SURFACE FINISH
• Specify roughness, color, sensitivity to ambient
  light, texture maps, and bump maps
• Apply finishes to individual parts or assemblies