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