Engineering Graphics Stephen W. Crown Ph.D. 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 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

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 SURFACE FINISH 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