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 with
  AutoCAD
• To understand how to use solid modeling in the
  design process

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Overview

• Primitives
• Extrude
• Revolve
• Solid Model Operators
• Sectioning
• 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
• Extrude a 2-D shape
• Revolve a curve about an axis

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BOX

• Gives a box with parallel sides
• Specify two diagonal corners
• Specify one corner and the height, width and
  depth
• Positive height is always interpreted as the
  positive Z axis direction
• Use object snap or type in exact coordinates to
  specify corners

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CYLINDER

• Specify the center point, the diameter, and the
  height
• Positive height is defined in the positive Z axis
  direction
• The centerline of solid cylinders is oriented
  with the Z axis
• Change the user coordinate system to reorient the
  centerline of cylinders

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CONE

• Specify the center point of the base of the cone
  and the height
• Positive height is defined in the positive Z axis
  direction
• The centerline of cone is oriented with the Z
  axis
• Change the user coordinate system to reorient the
  centerline of cones

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SPHERE

• Specify the center point and diameter of the
  sphere
• A circle is drawn in each of the three principle
  planes (based on the current USC) to represent
  the solid sphere in non-rendered views

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WEDGE

• Gives an extruded right triangle
• Specify two diagonal corners on the inclined
  surface of the wedge
• The first point specified is a vertex which does
  not lie on the inclined surface
• The second point is used to determine height,
  width and depth but is not located on the wedge
• The triangular surfaces always lie in the X-Z
  plane

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EXTRUDE

• Two dimensional closed objects can be extruded to
  give solid objects
• circles
• polygons drawn with POLYGON
• rectangles drawn with RECTANG
• closed polylines
• The direction and length of extrusion can be
  defined by a line or polyline
• The height of extrusion in the positive Z axis
  direction can be specified

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REVOLVE

• Two dimensional closed objects can be revolved to
  give solid objects
• circles, closed polylines, etc.
• The axis of rotation can be defined several ways
• object
• x
• y
• two points
• The angle of revolution is specified

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Example Using Primitives

• Box
• Wedge
• Different views can easily be generated
• Use 3D-PROTO.DWG
• top
• front
• side
• iso

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Solid Model Operators

• Subtract
• subtracts one solid from another
• select a solid object then select the solids to
  subtract from it
• Intersection
• Gives the solid region that is in common to the
  selected solids
• Union
• Joins the selected solid so that it becomes a
  single entity

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Example Solid Model Operators

• Box
• Cylinder
• Subtract
• Union

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Example Offset Section

• BOX
• CYLINDER
• SUBTRACT
• Each Solid may be drawn in a different color

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Example Offset Section

• The outline of the part (top view) may be drawn
  and then extruded
• The holes and the slot could be added using BOX,
  CYLINDER, and SUBTRACT
• Always draw the base of the part in the X-Y plane
  of the world coordinate system

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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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Sectioning With Solid Models

• Slice
• cuts the solid object at the specified cutting
  plane using the current color
• breaks the objects into two parts
• one part may be deleted or moved
• Section
• creates a 2-D drawing of the section
• only draws the portion of the object that is cut
  (i.e. the portion of the object that has section
  lines)

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Sectioning With Solid Models

• SLICE command

• SECTION command

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Viewing Solid Models

• RENDER
• Destination
• Viewport
• Renders the object in the viewport
• Can not print rendered object from viewport
• Render window
• Creates a bitmap that may be printed or saved
• File
• Saves rendered image as a GIF, TIFF, BMP, etc.
• Select Objects or Render Scene

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Viewing Solid Models

• DVIEW
• Gives perspective to 3-D objects
• Select objects
• Distance, Camera, Target, Etc.

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Viewing Solid Models

• LIGHTS
• Distance, Point, Spotlight
• Ambient light
• Intensity
• Modify (specify location of light)
• FINISH
• Specify roughness, color, sensitivity to ambient
  light
• attach finishes to solid objects or change
  globally