solid modeling engineering graphics stephen w. crown ph.d
TRANSCRIPT
Solid Modeling
Engineering Graphics
Stephen W. Crown Ph.D.
Objective
• To learn how to generate solid models in CAD
• To understand how to use solid modeling in the design process
Overview
• Primitives
• Extrude
• Sweep
• Revolve
• Blend
• Solid Model Operators
• Viewing Solid Models
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
Example: Using Primitives
• Box• Wedge• Union / Protrusion
– 6 boxes
– 2 wedges
• Subtract / Cut– 1 box - minus 2 wedges
– 1 box - minus 2 boxes
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
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
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
• Subtract / Cut– subtracts one solid from another
– One solid is subtracted from the other.
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: Solid Model Operators
• 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
What procedure would you follow to create the two mating parts?
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
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
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
Viewing Solid Models
• Rendering Styles– Wireframe with
hidden lines – Hidden lines
removed– Shaded
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